The Boeing X-37 has flown eight orbital missions since 2010, has spent more than eleven years off the planet, and holds a single-flight endurance record of 908 days. Almost nothing about what it did up there is public. This is the thirty-eighth article in the X-Planes series, following the X-1, the X-2, the X-3, the X-4, the X-5, the X-6, the X-7, the X-8, the X-9, the X-10, the X-11, the X-12, the X-13, the X-14, the X-15, the X-16, the X-17, the X-18, the X-19, the X-20, the X-21, the X-22, the X-23, the X-24, the X-25, the X-26, the X-27, the X-28, the X-29, the X-30, the X-31, the X-32, the X-33, the X-34, the X-35, and the X-36.

Every previous article in this series has struggled with a vehicle that left too little trace. This one has the opposite problem. The X-37B has left a very large trace with a hole in the middle. Its launches were announced, its landings were photographed, its dimensions are published, its mission durations are recorded to the minute, and its orbit has been tracked repeatedly by amateur observers from the ground. What it carried and what it did are not public and are not going to be.

That shape of record decides what an article can honestly be about. Writing around the hole by speculating about the payload is the failure mode, and the vehicle has attracted a good deal of such speculation [Boeing X-37]. The series has a better instrument. The orbital mechanics are public whether the payload is or not, so the inclination, the altitude history, the manoeuvres and their velocity cost are all recoverable from data anybody can obtain. Each is a measurement, and together they offer an honest route into a classified subject.

The Research Question

The Question Nobody Outside the Programme Can Answer

What is in the payload bay. The contents are classified, the first three of the eight missions flew with no experiment named in the public mission record, and the announcements that have been made are almost certainly the exceptions rather than a sample [Boeing X-37]. This article does not speculate about the payload and does not treat the absence of an answer as an invitation.

The Question This Article Asks Instead

What does it cost to keep a five-tonne vehicle in orbit for 908 days, and what does the public record of the orbit reveal about the vehicle that flew it? The mission durations are the one extraordinary and fully public quantity the programme has produced. They are also, unlike the payload, constrained by physics that anybody can write down.

Why Endurance Is the Binding Unknown

The obvious guess is that a long mission is a propulsion problem. It is not, and a few lines of derivation show why. The specific energy of a Keplerian orbit is

\[\mathcal{E} = \frac{v^{2}}{2} - \frac{\mu}{r} = -\frac{\mu}{2a}\]

which depends on the semi-major axis $a$ and on nothing else. At 400 kilometres it is -29.40 megajoules per kilogram, and because a conservative field cannot change it, every secular change in the orbit is a non-conservative effect. In low Earth orbit there is essentially one, which is drag, and the drag makeup for a mission of this length turns out to be a minor line in the mass budget at the altitudes flown. The X-37B carries no crew, so it has no consumables limit either, which removes the constraint that governs every human spaceflight endurance record.

The energy statement above is the foundation of every orbital result in this article, and the literature that establishes it is the astrodynamics canon, and none of it concerns this vehicle.

What binds a mission of this length is hardware wear in the power loop, and the wear is cyclic. Every orbit takes the vehicle through the Earth’s shadow, every shadow discharges a battery, and every discharge consumes a fraction of a finite cycle life. Alongside that, the heat the vehicle generates must leave through a radiator whose area is fixed by the airframe, and the array that supplies the power must fold into a payload bay whose dimensions are published. Those three constraints are computable from public numbers and they are what this article computes.

This is the fifth consecutive article in which the vehicle’s own documentary cluster is thin, and the reason is different again. The X-33 and the X-34 were cancelled. The X-35 won its competition and never generated a trace at all. The X-36 ran to completion and produced a technique rather than a vehicle, so its contribution is filed under the names of its methods. The X-37 did not stop existing. It stopped being publishable, which makes a fifth distinct mechanism.

Programme Origin

Three Owners in Seven Years

The programme began at the National Aeronautics and Space Administration in 1999, when Boeing was selected to build an orbital technology demonstrator. Over the four years that followed, roughly 192 million dollars was spent, of which the space agency contributed 109 million, the United States Air Force 16 million and Boeing 67 million. A further contract worth about 301 million dollars followed in late 2002 under the Space Launch Initiative [Boeing X-37].

The programme then changed hands twice in two years. It transferred to the Defense Advanced Research Projects Agency on 13 September 2004, and the Air Force announced its own derivative on 17 November 2006 [Boeing X-37]. The vehicle that eventually flew was designed under one agency, developed under a second and operated by a third, and the published engineering record stops almost exactly where the second handover happens.

Three Owners With Different Aims

The space agency wanted a testbed for reusable orbital vehicle technology, and specifically for the thermal protection, the avionics and the autonomous landing that a follow-on to the Space Shuttle would need. The technologies it was to demonstrate are listed as an improved thermal protection system, enhanced avionics, an autonomous guidance system and an advanced airframe [Boeing X-37], and the space agency’s account of the programme describes an orbital experimental vehicle to be lifted to orbit by the Space Shuttle or a reusable launch vehicle and returned to Earth under its own power. That intent is legible in the reports the space agency published on the vehicle between 2000 and 2006, which read like technology-demonstration documents and cite the vehicle by name.

What the later owners wanted is not stated in any document this article could find, and the absence is itself the most informative fact in the programme’s history. A transfer to a defence research agency and then to an operational service, accompanied by the disappearance of the vehicle from the open literature, is a description of a programme whose purpose became classified.

The X-40 and the Origin of the Shape

The Boeing X-40 was an unpowered, subscale vehicle built for the Air Force as a Space Maneuver Vehicle demonstrator. The space agency’s account of it calls it an 80 percent subscale version of the X-37. It was dropped from a helicopter at Holloman Air Force Base in 1998 and again, in a longer series, at Dryden in 2001. The X-37 is described in turn as a 120 percent scaled derivative of it, an unusual lineage in that the smaller aircraft came first and the larger one inherited its outer mould line. The two published ratios are not reciprocals of one another. For a linear scale factor $s$ the inverse is $1/s$, and

\[\frac{1}{0.80} = 1.25, \qquad \frac{1}{1.20} = 0.833,\]

so the 80 percent figure implies a derivative of 125 percent and the 120 percent figure implies a subscale vehicle of 83 percent. Both are rounded descriptions of one geometry, and neither should be read as more precise than about five percent.

The Approach and Landing Test Vehicle

The X-37A Approach and Landing Test Vehicle was carried aloft beneath White Knight and released for a series of unpowered glides beginning on 7 April 2006. The first free flight ended when the vehicle overran the runway and sustained minor damage. The glide tests ended that year, after two further free flights on 18 August and 26 September 2006, and no orbital X-37A ever flew [Boeing X-37].

The Window This Article Calls the Period

This programme has no clean period and inheriting one from a predecessor article would be wrong. It began in 1999, changed owner in 2004 and again in 2006, first flew in 2010, and is still flying at the time of writing. There is no single window that is obviously the design era.

This article calls the period 1999 through 2011 and the contemporary era everything after. The choice is made on the grounds that 2011 is the year of the last engineering paper on the vehicle itself that the survey holds, the paper on the orbital test vehicle and its derivatives, and the second orbital mission launched in March of that year. The reference counts reported later use exactly this boundary.

Sizing From First Principles

Notation Where Standard Symbols Collide

Orbital mechanics and thermal engineering each own a set of symbols and the two sets overlap. The article carries both, so the ambiguous cases are marked here rather than resolved silently at each use.

Symbol Meaning The other standard use, avoided here
$\mathcal{E}$ specific orbital energy $\varepsilon$, which is reserved for emissivity
$\varepsilon$ emissivity  
$a$ semi-major axis the albedo, written $\alpha_{\oplus}$
$\alpha_{s}$ solar absorptivity  
$\delta$ depth of discharge $D$, which is reserved for drag in $L/D$
$w$ cell specific energy $e$, which is reserved for eccentricity
$N_{\text{orb}}$, $N_{\text{cyc}}$ orbits and battery cycles The article’s central claim is that these two are equal for this vehicle, so they are written separately and shown to coincide rather than assumed identical
$A_{\text{ref}}$ drag reference area $A$, which is the solar array area
$\Phi$ duty cycle $\eta$, which is reserved for the efficiencies
$T$ orbital period every temperature carries a subscript

Nothing is renamed for tidiness. Each entry is a case where two relations in this article would otherwise use one letter for two quantities. This series has met that defect before and resolves it the same way every time, by marking one of the two and saying so.

The Orbit as the Public Half of a Classified Vehicle

Everything in this section follows from two published numbers, the altitude and the inclination, and from relations that appear in every astrodynamics text. The orbital period of a circular orbit of radius $r$ about a body of gravitational parameter $\mu$ is

\[T = 2\pi \sqrt{\frac{r^{3}}{\mu}}\]

where $r$ is the geocentric radius, being the Earth’s equatorial radius of 6,378.137 kilometres plus the altitude, and $\mu$ is 398,600.4418 cubic kilometres per second squared. At an altitude of 400 kilometres this gives a period of 92.56 minutes, and the circular speed

\[v_{c} = \sqrt{\frac{\mu}{r}}\]

is 7.6686 kilometres per second. Those two numbers do most of the work that follows.

The Shadow, and a Threshold the Low-Inclination Missions Never Reach

A satellite is eclipsed when its perpendicular distance from the Earth-Sun line is less than the Earth’s radius and it lies on the night side. Taking a cylindrical shadow, which neglects the penumbra and the Sun’s finite angular size and errs in the conservative direction for a power budget, the fraction of an orbit spent in shadow is

\[f_{E} = \frac{1}{\pi} \arccos\!\left( \frac{\sqrt{r^{2} - R_{\oplus}^{2}}}{r \cos \beta} \right)\]

where $\beta$ is the beta angle, the angle between the Sun vector and the orbit plane. At 400 kilometres with the Sun in the orbit plane this gives 39.01 percent, which is 36.11 minutes of shadow in every 92.56 minute orbit.

The interesting feature of that relation is where it stops having a solution. The argument of the inverse cosine reaches unity, and the eclipse vanishes entirely, when

\[\beta > \beta^{*} = \arcsin\!\left( \frac{R_{\oplus}}{r} \right)\]

which at 400 kilometres is 70.22 degrees. A vehicle that can reach that beta angle enjoys periods of continuous sunlight, during which its batteries are not cycled at all.

Whether it can reach it is fixed by the inclination alone. The largest beta angle available at inclination $i$ is $i$ plus the Earth’s obliquity of 23.44 degrees. The first four missions, numbered OTV-1 to OTV-4 in the programme’s Orbital Test Vehicle designation, are catalogued at inclinations between 38.02 and 43.49 degrees, and the sixth at 45.08 [General Catalog of Artificial Space Objects]. Their ceilings are

\[\beta_{\max} = i + 23.44^{\circ}, \qquad 43.49^{\circ} + 23.44^{\circ} = 66.93^{\circ}, \qquad 45.08^{\circ} + 23.44^{\circ} = 68.52^{\circ} \;<\; \beta^{*} = 70.22^{\circ},\]

which are below the threshold. The threshold rises as the orbit descends, so the lower of those orbits fall short of it by more. The same sum gives every row of the table below.

Mission group Inclination Largest reachable beta Full-sun threshold Verdict
OTV-1 to OTV-4 38.02 to 43.49 degrees 61.46 to 66.93 degrees 70.22 degrees never reaches full sun
OTV-6 45.08 degrees 68.52 degrees 70.22 degrees never reaches full sun
OTV-5 54.5 degrees 77.94 degrees 70.22 degrees reaches full sun
OTV-7 59.27 degrees 82.71 degrees 70.22 degrees reaches full sun

A vehicle in the sixth mission’s 45.08 degree orbit at this altitude is eclipsed on every orbit of every day of its mission, and no phasing of the node or the season provides relief. Averaged over a full precession of the node and a full year of the Sun’s motion, the mean eclipse fraction at 45.08 degrees is 35.76 percent, and the fraction of sampled geometries that eclipse at all is exactly 100 percent. At 54.5 degrees the mean falls to 33.61 percent and 95.87 percent of geometries eclipse. The average is taken over a uniform grid of $J$ node positions $\Omega_{j}$ and $K$ solar ecliptic longitudes $\lambda_{k}$,

\[\bar{f}_{E} = \frac{1}{J K} \sum_{j=1}^{J} \sum_{k=1}^{K} f_{E}\!\left( \beta(\Omega_{j}, \lambda_{k}) \right), \qquad J = 720, \quad K = 60,\]

with $\beta$ from the Sun vector and orbit normal as given in the next section, and the share of geometries that eclipse at all is the fraction of those $43{,}200$ grid points at which $f_{E} > 0$. The higher inclination buys relief and the lower one does not. The difference comes from the orbit chosen for each mission, and the vehicle plays no part in it.

Why That Average Is a Measurement and Not an Assumption

Averaging over the node is only legitimate if the node turns during the mission. It does, and the rate follows from the Earth’s oblateness. The dominant secular effect of the second zonal harmonic $J_{2}$ on a near-circular orbit is a regression of the ascending node at

\[\dot{\Omega} = -\frac{3}{2} J_{2} \left( \frac{R_{\oplus}}{p} \right)^{2} \sqrt{\frac{\mu}{a^{3}}} \, \cos i\]

where $p$ is the semi-latus rectum, equal to the radius for a circular orbit, and the square root is the mean motion. The sixth mission is catalogued at 379 by 399 kilometres and 45.08 degrees [General Catalog of Artificial Space Objects], and is represented here by a circular orbit at 400 kilometres. At that altitude and inclination the rate is -5.687 degrees per day, so the node completes a full turn in 63.31 days.

The beta angle itself follows from the Sun vector and the orbit normal,

\[\sin \beta = \cos \delta_{\odot} \sin i \sin(\Omega - \alpha_{\odot}) + \sin \delta_{\odot} \cos i\]

with $\delta_{\odot}$ and $\alpha_{\odot}$ the solar declination and right ascension. The geometry therefore repeats at the beat between the node’s regression and the Sun’s annual motion rather than at either rate alone,

\[T_{\beta} = \frac{360^{\circ}}{\lvert \dot{\Omega} - \dot{\lambda}_{\odot} \rvert}\]

which gives 53.95 days.

Over its duration the sixth mission swept the node 14.36 times and the beta angle 16.85 times. The average above is not a modelling convenience. It describes the conditions the mission experienced, and an article quoting a single beta angle for a flight of this length would be quoting a transient.

The Mission Duration Is a Battery Cycle Count

The sixth mission lasted 908.88 days. At a 92.56 minute period that is

\[N_{\text{orb}} = \frac{t_{\text{mission}}}{T} = \frac{908.88 \times 86{,}400}{5{,}553.6} = 14{,}140\]

and because the vehicle’s inclination admitted no full-sun period, every one of those 14,140 orbits carried an eclipse and therefore a charge and discharge cycle. At 300 kilometres the same mission would be 14,459 orbits.

No number in this article is more useful. It converts an operational record into a hardware requirement, and it does so using nothing but the mission duration and the orbital period, both of which are public.

An Upper Bound From the Payload Bay

The payload bay is published as 2.1 metres by 1.2 metres. The Space Force fact sheet that states it is not reachable at the time of writing, so the figure is cited to the encyclopaedic specification that reproduces it. The planform area is

\[A_{\text{bay}} = 2.1 \times 1.2 = 2.52 \ \text{square metres}.\]

The solar array is stowed conformally inside it and deploys from the open bay [This Is Our First Look At The Secretive X-37B Spaceplane With Its Cargo Bay Doors Open], so the array area is bounded by what can be folded into a volume of that size. This section computes an upper bound on the electrical load, and the section after it computes a second and independent upper bound. Neither is an estimate of the actual load, which is not public.

A sun-pointed array of area $A$ generates

\[P_{\text{array}} = S \, A \, \eta \, \kappa\]

where $S$ is the solar constant of 1,361 watts per square metre, $\eta$ is the cell efficiency, taken as 0.30 for the gallium arsenide cells the vehicle is reported to use [Boeing X-37], and $\kappa$ is a packing factor taken as 0.85.

The array does not merely carry the load. It must also refill the battery during the sunlit fraction of the orbit, so for a load that runs continuously

\[\frac{P_{\text{array}}}{P_{\text{load}}} = 1 + \frac{f_{E}}{(1 - f_{E})\,\eta_{c}\,\eta_{d}}\]

where $\eta_{c}$ and $\eta_{d}$ are the charge and discharge efficiencies, both taken as 0.90. At an eclipse fraction of 39.01 percent this ratio is 1.790, so an array must be very nearly twice the size the load alone would suggest.

Array area Array power Continuous load supported
3 square metres 1,041 watts 582 watts
4 square metres 1,388 watts 776 watts
6 square metres 2,082 watts 1,164 watts
8 square metres 2,776 watts 1,551 watts
12 square metres 4,165 watts 2,327 watts

A six square metre array, a generous reading of what folds out of a bay of 2.52 square metres, carries 1,164 watts continuously. The row follows from the two relations above,

\[P_{\text{load}} = \frac{S \, A \, \eta \, \kappa}{P_{\text{array}} / P_{\text{load}}} = \frac{1{,}361 \times 6 \times 0.30 \times 0.85}{1.7896} = \frac{2{,}082.3}{1.7896} = 1{,}164 \ \text{watts},\]

where 1.7896 is the ratio quoted above as 1.790 before rounding.

A domestic kettle draws power of that order. The figure is a ceiling and makes no claim about the operating point.

The Doors and a Tighter Bound

Every watt the vehicle consumes becomes heat, and the heat has to leave. A radiator at temperature $T_{r}$ facing a sink at $T_{s}$ rejects

\[q = \varepsilon \sigma \left( T_{r}^{4} - T_{s}^{4} \right)\]

per unit area, where $\varepsilon$ is the emissivity and $\sigma$ is the Stefan-Boltzmann constant. The sink is not deep space. A surface that sees the Earth absorbs outgoing longwave radiation and reflected sunlight, and the temperature it cannot radiate below follows from

\[T_{s} = \left( \frac{F \left( \varepsilon q_{\text{IR}} + \alpha_{\oplus} \alpha_{s} S \right)}{\varepsilon \sigma} \right)^{1/4}\]

with $F$ the view factor to the Earth, $q_{\text{IR}}$ the outgoing longwave flux of about 237 watts per square metre, $\alpha_{\oplus}$ the albedo of about 0.30 and $\alpha_{s}$ the solar absorptivity of a white thermal control coating, about 0.20. The radiator emissivity $\varepsilon$ is taken as 0.85 here and in the table below. For a surface with half its view filled by the Earth, so that $F = 0.5$, this gives a sink temperature of 232.8 kelvin.

Radiator temperature Net flux rejected
20 degrees Celsius 214.4 watts per square metre
30 degrees Celsius 265.5 watts per square metre
40 degrees Celsius 321.9 watts per square metre
50 degrees Celsius 384.0 watts per square metre

Inverting for the area a given dissipation demands,

\[A_{r} = \frac{Q}{\varepsilon \sigma \left( T_{r}^{4} - T_{s}^{4} \right)}\]

so a kilowatt at 20 degrees Celsius needs 4.66 square metres and the same kilowatt at 40 degrees needs 3.11. The fourth power is doing the work, and a radiator that may run hotter is a radiator that may be smaller.

Flat doors of 2.1 metres by 0.6 metres give 2.52 square metres and reject 540 watts at 20 degrees Celsius. Curved doors radiating from both faces at 40 degrees Celsius reach 1,623 watts. Each figure is the door area times the net flux from the table, carried unrounded,

\[Q_{\text{flat}} = 2 \times (2.1 \times 0.6) \times 214.40 = 540 \ \text{watts}, \qquad Q_{\text{curved}} = 2 \times 2.52 \times 321.935 = 1{,}623 \ \text{watts},\]

where the leading factor of two counts the two doors in the first case and the two radiating faces in the second.

The two bounds are 1,164 watts from the array and between 540 and 1,623 watts from the radiator, and at the low end the radiator is the tighter of the two. On a compact spacecraft the radiator usually binds first. The Shuttle orbiter’s payload bay doors carried its radiators and were opened on reaching orbit for heat rejection [Space Shuttle], and the X-37B stows radiators in its bay alongside the array [This Is Our First Look At The Secretive X-37B Spaceplane With Its Cargo Bay Doors Open]. On that reading the open bay is not there only to expose the payload. It is also part of the cooling system.

Two independent public geometries therefore agree that this vehicle’s electrical scale is of the order of a kilowatt. They are not the same calculation, they share no input beyond the bay dimensions, and they bracket rather than coincide. Reporting the bracket is the honest form of the result, because claiming that two upper bounds agree to some precision would be claiming more than two upper bounds can support.

The Battery, and an Inversion Rather Than a Prediction

The energy drawn from the battery in one eclipse is

\[E = \frac{P_{\text{load}} \, t_{E}}{\eta_{d}}\]

which for a one kilowatt load across a 36.11 minute eclipse is 668.7 watt hours. The installed capacity must exceed that by the reciprocal of the depth of discharge $\delta$, and the mass follows from the cell specific energy $w$,

\[C = \frac{E}{\delta}, \qquad m_{b} = \frac{E}{\delta \, w} = \frac{P_{\text{load}} \, t_{E}}{\eta_{d} \, \delta \, w}.\]

The mass is inversely proportional to the depth of discharge and to nothing else that the designer controls cheaply.

Depth of discharge Installed capacity Mass at 100 watt hours per kilogram
20 percent 3,343.3 watt hours 33.4 kilograms
30 percent 2,228.9 watt hours 22.3 kilograms
40 percent 1,671.7 watt hours 16.7 kilograms
60 percent 1,114.4 watt hours 11.1 kilograms

Halving the depth of discharge doubles the battery mass, and the trade reduces to that. A long mission wants a shallow cycle, and a shallow cycle is heavy.

The article does not know the cell chemistry’s constants and will not assert them. What it can do is invert. The standard empirical form for a secondary cell in low Earth orbit is an inverse power law between cycle life and depth of discharge,

\[N_{\text{cyc}} \, \delta^{k} = \text{constant}, \qquad\text{equivalently}\qquad \frac{N_{\text{cyc}}}{N_{\text{ref}}} = \left( \frac{\delta_{\text{ref}}}{\delta} \right)^{k}\]

which the literature below establishes across several chemistries.

Anchoring it at an assumed reference point of 30,000 cycles at 30 percent, the depth of discharge that a 14,140-cycle mission admits is

\[\delta = \delta_{\text{ref}} \left( \frac{N_{\text{ref}}}{N_{\text{cyc}}} \right)^{1/k}\]
Exponent Admissible depth of discharge Battery mass per kilowatt
1.5 49.5 percent 13.5 kilograms
2.0 43.7 percent 15.3 kilograms
2.5 40.5 percent 16.5 kilograms
3.0 38.5 percent 17.3 kilograms

The result is insensitive to the exponent, and that insensitivity makes it worth reporting. Across the plausible range the required depth of discharge sits between 38 and 50 percent. The two ends of the table are

\[\delta_{k=3} = 0.30 \left( \frac{30{,}000}{14{,}140} \right)^{1/3} = 0.385, \qquad \delta_{k=1.5} = 0.30 \left( \frac{30{,}000}{14{,}140} \right)^{1/1.5} = 0.495,\]

and the mass column is the battery relation above at $P_{\text{load}} = 1$ kilowatt and $w = 100$ watt hours per kilogram, for instance $m_{b} = 668.7 / (0.437 \times 100) = 15.3$ kilograms at $k = 2$. The record endurance therefore does not require exotic energy storage. It requires a battery cycled conservatively, sized at something like fifteen kilograms for each kilowatt of continuous load, a small fraction of a five-tonne vehicle.

How the Duration Bounds the Altitude

A vehicle in low orbit decelerates at

\[a_{D} = \frac{1}{2} \rho v^{2} \frac{C_{D} A_{\text{ref}}}{m}\]

and holding the orbit against that costs a velocity increment equal to the deceleration integrated over the mission. Writing $B = m / (C_{D} A_{\text{ref}})$ for the ballistic coefficient, so that a larger value means a vehicle less troubled by drag, the makeup requirement over a mission of duration $t$ is

\[\Delta v = \frac{\rho v^{2}}{2 B} \, t.\]

Density comes from a piecewise exponential model at nominal solar activity. The drag area $C_{D} A$ is taken as 8 square metres, which is not published. The mass is the published launch mass of 4,990 kilograms, the only mass in the published specification [Boeing X-37], and the same figure is used for every mass in this article so that the drag requirement and the propellant budget that pays for it describe one vehicle. Propellant use lowers the mass by at most a tenth over a mission. The ballistic coefficient is then

\[B = \frac{m}{C_{D} A_{\text{ref}}} = \frac{4{,}990}{8} = 623.75 \ \text{kilograms per square metre},\]

and at 400 kilometres, with $v = 7{,}668.6$ metres per second and $t = 908.88 \times 86{,}400$ seconds,

\[\Delta v = \frac{3.725 \times 10^{-12} \times 7{,}668.6^{2}}{2 \times 623.75} \times 7.853 \times 10^{7} = 13.79 \ \text{metres per second}.\]

The requirement over 908.88 days at each altitude is as follows.

Altitude Density Velocity increment Propellant at 300 seconds specific impulse
250 kilometres 7.248 times ten to the minus eleven 274.4 metres per second 444.3 kilograms
300 kilometres 2.418 times ten to the minus eleven 90.8 metres per second 151.7 kilograms
350 kilometres 9.518 times ten to the minus twelve 35.5 metres per second 59.8 kilograms
400 kilometres 3.725 times ten to the minus twelve 13.8 metres per second 23.3 kilograms
450 kilometres 1.585 times ten to the minus twelve 5.8 metres per second 9.9 kilograms

The requirement changes by a factor of forty-seven across two hundred kilometres of altitude, because density is exponential and everything else in the relation is nearly constant.

The propellant each of those increments costs follows from inverting the rocket equation. Writing $m_{0}$ for the mass before the burn and $I_{sp}$ for the specific impulse,

\[\Delta v = I_{sp} \, g_{0} \ln \frac{m_{0}}{m_{0} - m_{p}}, \qquad \frac{m_{p}}{m_{0}} = 1 - \exp\!\left( -\frac{\Delta v}{I_{sp} g_{0}} \right)\]

and read the second form for the table above. A 500 kilogram hypergolic propellant load at 300 seconds specific impulse on a 4,990 kilogram vehicle buys 310.6 metres per second. The first form gives it directly,

\[\Delta v_{\text{budget}} = 300 \times 9.80665 \times \ln \frac{4{,}990}{4{,}990 - 500} = 2{,}942.0 \times 0.10558 = 310.6 \ \text{metres per second}.\]

Spending the entire budget on drag makeup and nothing else would sustain 908.88 days at 245.4 kilometres, and spending half of it would sustain the same mission at 275.7 kilometres.

The table’s propellant column applies the second form to the same 4,990 kilogram mass, so that at the two ends of the tracked band

\[m_{p}^{300} = 4{,}990 \left[ 1 - e^{-90.85 / (300 \times 9.80665)} \right] = 151.7, \qquad m_{p}^{400} = 4{,}990 \left[ 1 - e^{-13.79 / (300 \times 9.80665)} \right] = 23.3\]

kilograms, and the floor of 245.4 kilometres is the altitude $h^{}$ at which the makeup requirement exhausts the budget, $\rho(h^{}) \, v^{2} t / (2B) = 310.6$ metres per second.

The duration and the altitude are therefore not independent facts, and the observed pair is consistent. The six low-orbit missions are catalogued between 309 and 409 kilometres, from the fourth at 309 by 322 to the first at 407 by 409 [General Catalog of Artificial Space Objects]. The catalogue gives one epoch per mission and an orbit changes during a flight, so the band describes where the missions were recorded rather than every altitude they held. Across the table’s 300 to 400 kilometre rows a 908-day flight costs between 23 and 152 kilograms of propellant, which a vehicle of this size can carry alongside everything else it must do. Below about 250 kilometres a mission of that length is not affordable at all, and the public orbit and the public duration each constrain the other without either being assumed.

Reboost Cadence and Exponential Drag

The figures above hold the altitude constant. That framing suits a vehicle that reboosts often, and it does not suit one that lets the orbit sink and recovers it later. Holding 400 kilometres continuously costs 13.79 metres per second over 908.88 days. Letting the orbit decay for the whole mission and recovering at the end costs 18.47 metres per second, a ratio of

\[\frac{\Delta v_{\text{decay}}}{\Delta v_{\text{hold}}} = \frac{18.47}{13.79} = 1.339,\]

and the uncontrolled orbit would have fallen to 367.5 kilometres by then. The first figure is the makeup relation evaluated at 400 kilometres above. The second is the same deceleration integrated along the decaying orbit, with the altitude updated by the relation below.

The relation that produces the second figure is the secular decay of the semi-major axis under a drag acceleration $a_{D}$. Differentiating the specific energy displayed earlier and substituting the work drag does per unit time,

\[\frac{d\mathcal{E}}{dt} = -a_{D} v = \frac{\mu}{2a^{2}} \frac{da}{dt} \qquad \Longrightarrow \qquad \frac{da}{dt} = -\frac{2 a^{2} v}{\mu} \, a_{D}\]

and integrating it gives the decayed altitude.

The gap between the two figures is not a discrepancy between two calculations. It is the price of an infrequent reboost, and it exists because $\rho$ is exponential in altitude, so every metre lost puts the vehicle into denser air and makes the next metre more expensive.

A Solar Cycle Kind to the Record

Thermospheric density at a fixed altitude varies by roughly an order of magnitude between solar minimum and solar maximum, and the model used above is a nominal one. The makeup requirement is exactly linear in density, since

\[\Delta v = \frac{\rho v^{2}}{2 B} t \qquad \Longrightarrow \qquad \frac{\Delta v(\zeta \rho)}{\Delta v(\rho)} = \zeta\]

for any multiplier $\zeta$, so a bracket on the density passes straight through to a bracket on the answer and nothing needs recomputing. Applying the variation to the result rather than to the model, the drag makeup at 400 kilometres over 908.88 days runs as follows.

Solar condition Velocity increment Propellant
Deep solar minimum 4.1 metres per second 7.0 kilograms
Nominal 13.8 metres per second 23.3 kilograms
Solar maximum 68.9 metres per second 115.6 kilograms

The record 908-day mission launched in May 2020, five months after the solar minimum of December 2019. It began its flight in the quietest phase of the solar cycle [Solar Cycle 25 Is Here]. This is stated as an observation and not as an accusation of contrivance, because a launch date is set by many things and there is no evidence in the public record that the drag environment was one of them. What can be said is the arithmetic. The same vehicle flying the same orbit at solar maximum would have paid several times as much, and a record begun at solar minimum is a weaker statement about the vehicle than the same record set at solar maximum would have been.

This is the third article in four to find that a demonstration was tilted in a computable direction. The X-35 flew its famous sortie in the easiest available ordering. The X-36 flew against a handicap the full-scale aircraft would never carry, which tilted the other way. Ask which way the demonstration was tilted and by how much. It is usually arithmetic rather than opinion.

Dependent Systems

Thermal Protection and the Vehicle’s One Public Innovation

The X-37B’s leading edges use Toughened Uni-piece Fibrous Reinforced Oxidation-resistant Composite, a dual-layer tiled system with a carbonaceous cap over a low-conductivity silica-based substrate derived from Shuttle tile material. Its developers at the space agency’s Ames centre describe it as suitable for reusable entry heating at 2,900 degrees Fahrenheit and above, with single-use potential to at least 3,600, and report that the gapped-tile configuration of the X-37 wing leading edge was qualified in arc-jet exposures at 3,000 and 3,200 degrees [TUFROC Thermal Protection System]. Its developers report a capability similar to that of reinforced carbon-carbon at an order of magnitude lower cost [TUFROC Thermal Protection System], and its engineering is the only part of this vehicle published in detail, because it came out of the space agency phase and has civil applications.

The convective heat flux at a stagnation point follows the Sutton and Graves correlation

\[\dot{q}_{s} = k \sqrt{\frac{\rho}{R_{n}}} \, v^{3}\]

with $k$ equal to 1.7415 times ten to the minus fourth in SI units for air, $\rho$ the free-stream density, $R_{n}$ the nose radius and $v$ the speed. A surface in radiative equilibrium reaches

\[T_{w} = \left( \frac{\dot{q}_{s}}{\varepsilon \sigma} \right)^{1/4}.\]

At a representative peak-heating condition of 7,500 metres per second and the density at 70 kilometres, the results are as follows.

Nose radius Heat flux Radiative equilibrium temperature
0.20 metres 153.85 watts per square centimetre 2,376.9 kelvin
0.30 metres 125.62 watts per square centimetre 2,259.5 kelvin
0.50 metres 97.30 watts per square centimetre 2,119.7 kelvin
1.00 metres 68.80 watts per square centimetre 1,943.8 kelvin

A common intuition about small reentry vehicles is wrong and this relation is why. The flux depends on the local radius of curvature and not on the size of the vehicle carrying it. A small aircraft with a blunt nose is cooler at that nose than a large aircraft with a sharp one. What makes a small vehicle hard is not that it is small. It is that a small vehicle has less room in which to be blunt, so its designers face pressure toward radii that a larger airframe would not need to accept, and the material has to make up the difference. TUFROC exists to relieve precisely that pressure.

Entry, and a Term That Cancels

An entry vehicle in equilibrium glide holds the vertical force balance, so the vertical component of lift makes up the difference between weight and centrifugal relief

\[L \cos \phi = m \left( g - \frac{v^{2}}{r} \right)\]

where $\phi$ is the bank angle. The remaining horizontal component turns the velocity vector at

\[\frac{d\psi}{dt} = \frac{\left( g - v^{2}/r \right) \tan \phi}{v}\]

while the deceleration is the lift divided by the lift-to-drag ratio

\[\frac{dv}{dt} = -\frac{1}{L/D} \cdot \frac{g - v^{2}/r}{\cos \phi}.\]

Dividing the first by the second removes the altitude term entirely, because both carry the same factor, and what remains is

\[\frac{d\psi}{dv} = -\frac{(L/D) \sin \phi}{v}, \qquad \Delta\psi = (L/D) \sin \phi \, \ln\!\left( \frac{v_{i}}{v_{f}} \right).\]

The heading a vehicle can turn during entry depends on its lift-to-drag ratio, its bank angle and the ratio of entry speed to terminal speed, and on nothing else. Not on its mass, not on its wing area, not on the density of the atmosphere it flies through. At a lift-to-drag ratio of 1.1 and 45 degrees of bank, from entry interface to 900 metres per second, the turn is 96.19 degrees.

Lift-to-drag ratio Heading turned at 45 degrees bank
0.8 69.96 degrees
1.0 87.45 degrees
1.1 96.19 degrees
1.4 122.43 degrees

That identity is worth more than the crossrange number it supports, because it identifies which vehicle properties can and cannot buy manoeuvre during entry, and does so without reference to any atmosphere model.

Crossrange as a Lower Bound

The heading identity gives the direction but not the displacement, and for that the equations must be integrated. Working in the velocity domain, where the equilibrium-glide deceleration supplies the element of time,

\[dt = -\frac{dv}{a_{D}}, \qquad a_{D} = \frac{1}{L/D} \cdot \frac{g - v^{2}/r}{\cos \phi}\]

the crossrange and downrange are the two components of the ground track,

\[y = \int_{v_{f}}^{v_{i}} \frac{v \sin \psi(v)}{a_{D}(v)} \, dv, \qquad x = \int_{v_{f}}^{v_{i}} \frac{v \cos \psi(v)}{a_{D}(v)} \, dv\]

with $\psi(v)$ taken from the identity above. Unlike the heading, the displacement does not shed the altitude term, because the deceleration appears alone in the denominator rather than in a ratio.

Searching over bank angle for the maximum gives the following.

Lift-to-drag ratio Best bank angle Crossrange
0.8 43.97 degrees 761.8 kilometres
1.0 43.42 degrees 1,167.8 kilometres
1.1 43.11 degrees 1,397.8 kilometres
1.4 42.04 degrees 2,181.8 kilometres

The Space Shuttle orbiter was required to reach 1,100 nautical miles of crossrange, a figure set by the Air Force’s wish to return to Vandenberg after a single orbit [The Space Shuttle Decision]. Taking a hypersonic lift-to-drag ratio near 1.1 as representative of the orbiter, the table’s row at that ratio converts as

\[y = \frac{1{,}397.8 \ \text{km}}{1.852 \ \text{km per nautical mile}} = 754.7 \ \text{nautical miles}, \qquad \frac{754.7}{1{,}100} = 0.686 .\]

This model returns 755 nautical miles at the same ratio, 0.686 of the requirement, a shortfall that is expected and gives no cause for concern. A single constant bank angle is not the optimal control and a real entry modulates it, so a constant-bank integration is a lower bound by construction. It is reported as a lower bound and not as agreement, because a model with a free parameter that landed within a few percent of a published figure would have demonstrated very little.

The crossrange is also insensitive to the terminal speed at which the glide is deemed to end, moving only from 1,411 to 1,371 kilometres as that speed runs from 700 to 1,200 metres per second. That matters because the terminal speed is a modelling choice and is not measured. Both figures are the crossrange integral above re-evaluated with $v_{f}$ changed, and their spread relative to the 900 metre per second case is

\[\frac{y(700) - y(1{,}200)}{y(900)} = \frac{1{,}411 - 1{,}371}{1{,}397.8} = 0.029 .\]

Aerothermodynamics Beneath the Entry

The heating relation above is the simplest member of a large body of work on what happens in the shock layer, where the gas dissociates, the flow departs from equilibrium and the surface chemistry decides how much of the recombination energy the vehicle has to absorb. The catalytic behaviour of the surface is the part that a coating can change. The Advanced TUFROC treatment addresses exactly that behaviour [Advanced TUFROC Thermal Protection System], so a material development shows up as a temperature reduction rather than as a thicker tile.

Hypersonic Aerodynamics and the Configuration

The shape is a small winged spaceplane with two angled tail fins, and its aerodynamic design was derived from the Shuttle orbiter [Boeing X-37]. It therefore draws on the hypersonic configuration work that the X-23, X-24 and Shuttle orbiter programmes carried out across three decades of wind tunnel and flight work. The X-37B contributed nothing public to that body of knowledge and drew heavily on it.

Propulsion as the Least Interesting System

The Rocketdyne AR2-3, a throttleable engine burning high-test hydrogen peroxide and jet fuel at about 29.3 kilonewtons, was evaluated in 1999 under the Future-X demonstrator engine work for possible use on the vehicle. Some accounts, among them the encyclopaedia entry, attribute it to Aerojet, although Rocketdyne developed it. The orbital vehicle that flew is reported to use a conventional hypergolic system burning nitrogen tetroxide and hydrazine [Boeing X-37]. No available choice was less adventurous, and a vehicle whose interesting problems lie elsewhere ought to use exactly that.

Its capability is small. The 310.6 metres per second computed earlier, for an assumed 500 kilogram load, is enough for orbit maintenance, modest phasing and a deorbit burn, and is nowhere near enough for a plane change of any consequence. Two circular orbits of the same radius carry the same speed, so the increment between them closes an isosceles triangle and costs

\[\Delta v = 2 v \sin\!\left( \frac{\Delta i}{2} \right).\]

A change from 40 degrees to 54.5 degrees at 400 kilometres therefore costs 1,935.5 metres per second, or 6.23 times the whole propulsive budget, so the differing inclinations between missions are launch decisions rather than on-orbit ones.

Guidance, Navigation and the Autonomous Landing

The vehicle lands itself on a runway with nobody aboard and nobody flying it remotely, which the Shuttle orbiter never did and the Soviet Buran did once [Boeing X-37]. The problem divides into the entry guidance already discussed, a terminal area energy management phase that trades excess energy through turns in a cylindrical corridor around the runway, and an approach and landing phase.

The hard part is that an unpowered vehicle cannot go around. Every landing is a single attempt with a fixed energy budget. Two relations set the size of the problem. A glide trades height for distance at the lift-to-drag ratio,

\[R = \left( \frac{L}{D} \right) h\]

which carries no mass, no wing area and no air density, and the total available is the specific energy expressed as a height,

\[h_{E} = h + \frac{v^{2}}{2 g}.\]

At 30 kilometres and 900 metres per second the energy height is 71.30 kilometres while a straight glide at a subsonic lift-to-drag ratio of 4.5 covers 135 kilometres. The turns in the heading alignment cylinder exist to remove the excess, and the phase takes its name, energy management rather than navigation, from that task. The X-24 programme spent its life characterising the same constraint, and this series treated it at length in that article. What the X-37B added was not the guidance but the autonomy, meaning the willingness to certify a system to land a five-tonne vehicle on a runway at Vandenberg or the Kennedy Space Center with no human in the loop at all.

Structure, Scale and the Payload It Can Carry

Quantity X-37B Shuttle orbiter Ratio
Length 8.92 metres 37.24 metres 4.17
Wingspan 4.55 metres 23.79 metres 5.23
Payload bay length 2.10 metres 18.30 metres 8.71
Payload bay volume 3.02 cubic metres 304.1 cubic metres 100.6
Launch mass 4,990 kilograms 78,000 kilograms 15.63

The bay volume ratio of 100.6 against a length ratio of 4.17 is the number that characterises this vehicle. Comparing two vehicles that are not geometrically similar is best done by measuring the exponent that relates them. For a quantity $Q$ and a length $\ell$,

\[Q \propto \ell^{\,n} \qquad \Longrightarrow \qquad n = \frac{\ln \left( Q_{1} / Q_{2} \right)}{\ln \left( \ell_{1} / \ell_{2} \right)}\]

and geometric similarity would give $n = 3$ for both a volume and a mass at constant density.

Quantity Measured exponent Geometric value
Payload bay volume 3.226 3
Launch mass 1.924 3

The bay shrank faster than geometry demands and the mass shrank far more slowly, showing the square-cube penalty in its clearest form. A geometrically similar orbiter scaled down to 8.92 metres would mass 1,072 kilograms. The X-37B masses 4,990, a factor of 4.655. Both follow from the cube of the length ratio,

\[m_{\text{similar}} = 78{,}000 \left( \frac{8.92}{37.24} \right)^{3} = 1{,}072 \ \text{kilograms}, \qquad \frac{4{,}990}{1{,}072} = 4.655 .\]

The small vehicle keeps the airframe and loses the room. Thermal protection scales with area, avionics and actuators barely scale at all, and structure cannot thin below minimum gauge, so a reusable vehicle carries a fixed overhead that the payload bay pays for. The published payload capacity of 227 kilograms, against the launch mass of 4,990 kilograms, is a payload fraction of

\[\frac{m_{\text{payload}}}{m_{\text{launch}}} = \frac{227}{4{,}990} = 4.55 \ \text{percent}.\]

This is a vehicle whose reusable airframe, thermal protection, power system and autonomy consume almost the entire mass budget, leaving a payload fraction that would embarrass an expendable upper stage. That is not a criticism. It is the definition of what the vehicle is for. An expendable satellite bus delivers more payload per kilogram launched and does not come back. Everything the X-37B spends its mass on is spent on returning, and the return is the product.

The Flight Test Record

Eight Missions, Seven Completed

Mission Launched Landed Duration Launch vehicle
OTV-1 22 April 2010 3 December 2010 224.39 days Atlas V 501
OTV-2 5 March 2011 16 June 2012 468.58 days Atlas V 501
OTV-3 11 December 2012 17 October 2014 674.93 days Atlas V 501
OTV-4 20 May 2015 7 May 2017 717.86 days Atlas V 501
OTV-5 7 September 2017 27 October 2019 779.74 days Falcon 9
OTV-6 17 May 2020 12 November 2022 908.88 days Atlas V 501
OTV-7 28 December 2023 7 March 2025 434.26 days Falcon Heavy
OTV-8 21 August 2025 in progress   Falcon 9

The seven completed missions, timed from launch to landing in the mission record, total 4,208.65 days, or 11.52 years of accumulated flight. The durations rose monotonically through the first six missions and then fell sharply, and the shorter seventh mission was also the only one flown in a highly elliptical orbit [Boeing X-37].

The number that matters operationally is not the longest mission but the duty cycle. The first launch and the seventh landing are 5,433 days apart, so

\[\Phi = \frac{\sum_{k} t_{k}}{t_{\text{span}}} = \frac{4{,}208.57}{5{,}433} = 77.46 \text{ percent}\]

For more than three quarters of fifteen years an X-37B has been in orbit, on two airframes, and the individual durations add up to that claim. A fleet of two holding a three-quarters duty cycle is evidence of fast turnaround, and a single-mission endurance figure conceals that part of the record.

The Only Mission Described in Technical Terms

OTV-7 launched into a highly elliptical orbit, catalogued with a perigee of 336 kilometres, an apogee of 37,895 kilometres and an inclination of 59.27 degrees [General Catalog of Artificial Space Objects]. The two apsides fix the orbit completely,

\[a = \frac{r_{p} + r_{a}}{2}, \qquad e = \frac{r_{a} - r_{p}}{r_{a} + r_{p}}, \qquad p = a \left( 1 - e^{2} \right)\]

giving a semi-major axis of 25,494 kilometres, an eccentricity of 0.7366 and, through Kepler’s third law, a period of 11.25 hours. No previous X-37B mission had left low Earth orbit [Boeing X-37].

On 10 October 2024 the Space Force announced that the vehicle would perform aerobraking to change its orbit and to dispose of its service module components in accordance with recognised standards for space debris mitigation [X-37B begins novel space maneuver]. That announcement is the only official description of a specific X-37B manoeuvre that this article has found, and its rarity is the reason to take it seriously.

What Aerobraking Bought, in Numbers

The speed at any point on an orbit follows from the vis-viva relation

\[v = \sqrt{\mu \left( \frac{2}{r} - \frac{1}{a} \right)}\]

which gives a perigee speed of 10.1538 kilometres per second on the elliptical orbit against 7.7050 kilometres per second for a circular orbit at the same altitude. Circularising propulsively at perigee therefore costs

\[\Delta v = v_{p} - v_{c} = 2{,}448.8 \text{ metres per second}.\]

The vehicle’s entire propulsive budget, on the 500 kilogram assumption used throughout, is 310.6 metres per second. The manoeuvre the atmosphere performed is 7.88 times everything the engine could have done.

And setting it up is nearly free. Lowering perigee from 336 to 100 kilometres, burning at apogee where the vehicle moves slowest and a given impulse moves the opposite apsis furthest, costs 23.8 metres per second. The cost is the difference of two apogee speeds from the vis-viva relation, with $r_{a}$ fixed at 44,273.1 kilometres and the semi-major axis falling by half the perigee change, from 25,493.6 to 25,375.6 kilometres,

\[\Delta v_{\text{lower}} = \sqrt{\mu \left( \frac{2}{r_{a}} - \frac{1}{25{,}493.6} \right)} - \sqrt{\mu \left( \frac{2}{r_{a}} - \frac{1}{25{,}375.6} \right)} = 1{,}539.85 - 1{,}516.06 = 23.79 \ \text{metres per second}.\]

That purchase then takes 2,449 metres per second from the atmosphere, a leverage of 103 to one,

\(\frac{v_{p} - v_{c}}{\Delta v_{\text{lower}}} = \frac{2{,}448.8}{23.79} = 102.9 .\) That ratio is the entire argument for aerobraking, and it needs no opinion to support it.

A Feasibility Estimate That Was Wrong, and the Calculation That Overturned It

Drag removes velocity at each perigee passage. The decrement is the drag deceleration integrated along the arc, and taking the true anomaly $\nu$ as the independent variable keeps the quadrature well conditioned near perigee where the whole contribution lies,

\[\Delta v_{\text{pass}} = \int \frac{\rho(r) \, v^{2}}{2 B} \, dt = \int_{-\nu_{0}}^{\nu_{0}} \frac{\rho(r) \, v^{2}}{2 B} \cdot \frac{r^{2}}{\sqrt{\mu p}} \, d\nu\]

where $\sqrt{\mu p}$ is the specific angular momentum and $r$ follows the conic $r = p / (1 + e \cos \nu)$. Each pass leaves the perigee where it is and lowers the apogee, and the new apogee follows from the reduced perigee speed through the vis-viva relation inverted for the semi-major axis,

\[a' = \left( \frac{2}{r_{p}} - \frac{(v_{p} - \Delta v_{\text{pass}})^{2}}{\mu} \right)^{-1}, \qquad r_{a}' = 2 a' - r_{p}.\]

Evaluating the first for the seventh mission’s orbit gives the following.

Perigee altitude Velocity removed per pass Passes to remove 2,449 metres per second
100 kilometres 3.35997 metres per second 729
110 kilometres 0.69584 metres per second 3,519
120 kilometres 0.20615 metres per second 11,878
130 kilometres 0.08441 metres per second 29,010
150 kilometres 0.02625 metres per second 93,297
200 kilometres 0.00446 metres per second 548,743

Aerobraking was announced in October 2024 and the vehicle landed on 7 March 2025, so roughly 150 days were available. At the initial 11.25 hour period that is about 320 passes, which would demand 7.65 metres per second per pass,

\[N = \frac{150 \times 24}{11.253} = 319.9, \qquad \frac{2{,}448.8}{319.9} = 7.65 \ \text{metres per second},\]

and no perigee in that table delivers it above the entry interface.

That estimate is the wrong instrument and the next calculation overturns it. The period is not constant. Every pass lowers the apogee, which shortens the period, which fits more passes into the same calendar. Running the walk-down properly, with the orbit updated after every pass, gives a very different answer.

Perigee altitude Passes to reach a 1,000 kilometre apogee Elapsed time
100 kilometres 579 99.7 days
110 kilometres 2,792 480.7 days
120 kilometres 9,415 1,622.4 days

A perigee near 100 kilometres fits the calendar and the ones above it do not. Against the roughly 150 days available, the walk-down times at 100 and 110 kilometres fall on either side,

\[99.7 \ \text{days} \;<\; 150 \ \text{days} \;<\; 480.7 \ \text{days}.\]

The fixed-period estimate said the manoeuvre was infeasible at every perigee, and it was wrong, because it held constant the one quantity the manoeuvre is designed to change. The crude version is left standing in this article deliberately, because the lesson lies in the difference between the two.

And the passes are thermally mild, a property that makes the manoeuvre attractive. At a perigee speed of 10.361 kilometres per second and the density at 100 kilometres, the stagnation flux on a 0.30 metre nose radius is 25.74 watts per square centimetre and the radiative equilibrium temperature is 1,520 kelvin. That is roughly a fifth of the flux computed earlier for a full entry. The Sutton and Graves correlation with the model density of $5.297 \times 10^{-7}$ kilograms per cubic metre at 100 kilometres, and the radiative balance at an emissivity of 0.85, give

\[\dot{q}_{s} = 1.7415 \times 10^{-4} \sqrt{\frac{5.297 \times 10^{-7}}{0.30}} \, (10{,}361.1)^{3} = 2.574 \times 10^{5} \ \text{W/m}^{2}, \qquad T_{w} = \left( \frac{\dot{q}_{s}}{0.85 \, \sigma} \right)^{1/4} = 1{,}520 \ \text{K},\]

and the ratio to the full-entry flux at the same nose radius is $25.74 / 125.62 = 0.205$. The vehicle is not reentering five hundred and seventy-nine times. It is grazing.

Why This Vehicle Is Bad at Aerobraking, and Which Spacecraft Are Good at It

A spacecraft built to aerobrake makes itself as light and as broad as it can, and the reason is a proportionality rather than a preference. The drag integral carries the ballistic coefficient as a single divisor, so

\[\Delta v_{\text{pass}} \propto \frac{1}{B} \qquad \Longrightarrow \qquad N_{\text{passes}} \propto B\]

at a fixed perigee. Halving the ballistic coefficient halves the number of passes, and at a fixed orbital period it halves the calendar. The Mars Reconnaissance Orbiter aerobraked with its solar arrays broadside to the flow, presenting a drag area of 37.5 square metres at a pre-aerobraking mass of about 1,400 kilograms [Mars Reconnaissance Orbiter Operational Aerobraking Phase Assessment]. With a drag coefficient of 2.0, assumed here as typical of free molecular flow and not taken from that source,

\[B_{\text{MRO}} = \frac{1{,}400}{2.0 \times 37.5} = 18.7 \ \text{kilograms per square metre}, \qquad \frac{B_{\text{X-37B}}}{B_{\text{MRO}}} = \frac{623.75}{18.67} = 33.4 .\]

The X-37B, a dense body with a small array, sits near 624, a ratio of 33.4.

This difference explains why a manoeuvre routine at Mars required a perigee at the edge of the atmosphere here. The X-37B cannot reconfigure itself into a brake, so it has to find its drag in denser air instead.

What the arithmetic does not settle is how much of the apogee reduction was aerodynamic. The announcement says aerobraking was used to change the orbit with minimal fuel and to dispose of the service module. It does not say that the entire reduction from 37,895 kilometres was aerodynamic, and this article does not assume it was. What the arithmetic does establish is that the manoeuvre is feasible for this vehicle only at a perigee near 100 kilometres, and that at such a perigee it is both fast enough and thermally mild enough to have been done.

Astrodynamics Beneath the Manoeuvres

Every velocity increment in this article is an impulsive two-body result. That approximation suits a chemical engine firing for minutes on an orbit measured in hours, and the literature below establishes and bounds it.

Announced Experiments Are Almost Certainly Not a Sample

The sixth mission was the first to fly a service module, a ring attached to the aft of the vehicle for hosting additional experiments. It deployed FalconSat-8, a small satellite developed by Air Force Academy cadets, and carried two space agency experiments, a materials exposure plate and a study of radiation effects on seeds [Boeing X-37]. It also carried the Naval Research Laboratory’s Photovoltaic Radio-frequency Antenna Module, a tile built to test the conversion of sunlight to radio-frequency microwave power as a step toward space-based solar power [NRL Conducts First Test of Solar Power Satellite Hardware in Orbit].

Roughly ten named experiments across eight missions and more than eleven years of flight are not a sample of what the vehicle has carried [Boeing X-37]. It is a list of the things that could be announced. The announced experiments share one property. Each has an unclassified sponsor with an independent reason to publish. The list therefore follows a selection rule, not a random draw, and reading the programme’s purpose from it would be an error.

How the Orbit Became Public Anyway

The missions have been located and tracked by a distributed network of amateur optical observers, who recover orbital elements from timed positional measurements against the star background. That is how the first mission’s orbit was identified in 2010 and how the 54.5 degree inclination of the fifth mission became known [Boeing X-37]. The fifth mission’s orbit was recovered in April 2018 from a chance sighting by an observer in the Netherlands, who estimated a circular orbit of about 54.5 degrees inclination at 355 kilometres, refined with an earlier observation from Scotland [US Military’s Mysterious X-37B Space Plane Spotted by Satellite Trackers].

The technique is old, cheap and impossible to prevent. A vehicle in low Earth orbit is a sunlit object against a dark sky for a predictable window at dawn and dusk, and the same geometry that lets it see the ground lets the ground see it. A programme can classify a payload. It cannot classify a Keplerian orbit, and every quantitative statement in this article rests on that asymmetry.

Disposal as One Reason the Manoeuvre Was Announced

The announcement framed the aerobraking both as debris mitigation and as a first-of-its-kind manoeuvre [X-37B begins novel space maneuver], and the compliance half is plausibly the half that gave a classified programme a reason to describe it. A service module left in a highly elliptical orbit crosses every altitude band below its apogee and does so for a very long time, and the announcement ties its disposal to recognised standards for space debris mitigation. The programme found a reason to describe a manoeuvre, and compliance was one of the two reasons it gave.

Comparison With Ground Prediction

No prediction the programme made on the ground can be set beside a flight measurement, because neither half is public. The survey described under The Source Base shows that the space agency’s reports on the vehicle stop in 2006 and that no title in the survey describes a flown mission. The record holds no mass breakdown, no power budget, no propellant load, no thermal design and no flight data of any kind from any of the eight missions. The comparison this series makes elsewhere, between a wind tunnel or analytical prediction and what flight returned, cannot be made for this vehicle in that form.

What the space agency phase set out to demonstrate is public, and so is the bare outcome. The agency wanted a testbed for the thermal protection, the avionics and the autonomous landing that a successor to the Space Shuttle would need [Boeing X-37]. What the Data Changed, below, records that TUFROC is flight-proven as the vehicle’s wing leading edge and that the vehicle lands itself on a runway with no crew and no remote pilot, and each of the seven completed missions in the table under The Flight Test Record ended in a landing. None of the temperatures, loads or trajectories behind those outcomes has been released. The outcome can be stated and its margin against the prediction cannot.

The only predictions this article can test against the flight record are its own, made from published dimensions and the public orbit. Three of them meet an observed quantity, and each is argued in full where it first appears.

The first is the drag budget. The first-principles sizing earlier in the article computed that a 908.88 day mission costs between 23 and 152 kilograms of propellant between 300 and 400 kilometres, and that below about 250 kilometres a mission of that length is not affordable at all. The six low-orbit missions are catalogued between 309 and 409 kilometres. The observed altitude and the observed duration are consistent with the computed budget. The agreement lies between an analysis and a public orbit rather than between a programme prediction and programme data, and it rests on an assumed drag area and an assumed propellant load, as the section headed Where the Framing Breaks Down states.

The second is the aerobraking campaign. A fixed-period estimate found that no perigee above the entry interface could remove 2,449 metres per second in the roughly 150 days between the October 2024 announcement and the landing on 7 March 2025. The walk-down that updates the orbit after every pass found that a perigee near 100 kilometres reaches a 1,000 kilometre apogee in 99.7 days. The corrected calculation permits the announced manoeuvre and the landing that followed, and the crude one forbids them. The comparison stops there, because the perigee flown, the number of passes and the fraction of the apogee reduction that was aerodynamic are not public.

The third is the crossrange. The constant-bank integration returns 755 nautical miles at a lift-to-drag ratio of 1.1, or 0.686 of the 1,100 nautical mile requirement set for the Space Shuttle orbiter. The comparison is with another vehicle’s specification and not with any X-37B flight, and it is reported as a lower bound for that reason. No crossrange flown by the X-37B has been published.

The development flights supply outcomes without predictions. The X-40 was dropped from a helicopter at Holloman Air Force Base in 1998 and at Dryden in 2001, and the glides of the X-37A Approach and Landing Test Vehicle began on 7 April 2006, its first free flight ending when the vehicle overran the runway. The record states none of the predictions those flights were testing.

The comparison this section can make is between public arithmetic and a public orbit, and it holds wherever it can be checked. The comparison the series exists to make, between what the designers expected and what their vehicle measured, lies behind the compartment for every mission flown.

What the Data Changed

What the Programme Settled

That a small winged vehicle can be reused across multi-year orbital missions with a turnaround as short as four months. Two airframes have flown eight missions between them. The first vehicle flew the first, third, sixth and eighth missions and the second vehicle the others, and the second vehicle landed from the fourth mission on 7 May 2017 and launched on the fifth on 7 September 2017 [Boeing X-37]. The programme thereby demonstrated reuse of an orbital spaceplane by an operator other than the Shuttle programme.

That autonomous runway landing from orbit is a solved problem. Seven entries, seven landings, at two sites, Vandenberg and the Kennedy Space Center, with no crew and no remote pilot. Buran demonstrated it once in 1988 and the capability then lapsed [Boeing X-37]. The X-37B made it routine, and routine is a stronger claim than demonstrated.

That TUFROC works. A leading-edge material developed for this vehicle is flight-proven as the X-37B wing leading edge [Advanced TUFROC Thermal Protection System] and has since been adopted for the nose and leading edges of the Dream Chaser [Dream Chaser]. That adoption is the clearest technology transfer the programme has produced.

What It Fed Into

The thermal protection work is the visible thread. TUFROC and its successors appear in the open literature under their own names, sponsored by the space agency, and are cited by later hypersonic and entry vehicle work.

The autonomy is the invisible thread. A commercial lifting-body vehicle, the Dream Chaser, is built to land on a runway and had not flown to orbit at the time of writing [Dream Chaser], and the X-37B solved first the guidance, navigation and control problem it faces, though the lineage cannot be traced through citations because one half of it was never published.

What It Failed to Influence

The programme has published almost nothing since 2006 and the open literature therefore cannot cite it. A body of work that cannot be cited cannot accumulate, and fifteen years of operational experience with a reusable orbital vehicle, which would be the largest such body in existence, is unavailable to everyone outside the compartment.

Classification carries that cost, and the cost is real. Every designer of a reusable entry vehicle since 2010 has had to rediscover, or fail to discover, things this programme knows.

The Contemporary Literature

Cluster Records
Aerobraking, aerocapture and aeroassisted orbit transfer 601
Thermal protection materials and systems 359
The upper atmosphere, density models and satellite drag 342
Spacecraft thermal control, radiators and heat transport 341
Space surveillance, tracking and orbit determination 338
Payload deployment, experiments and power beaming 295
Entry trajectory, guidance and control 289
Spacecraft batteries, cycle life and degradation 260
Entry aerothermodynamics, stagnation heating and the plasma sheath 216
Hypersonic aerodynamics, boundary layers and transition 210
Solar arrays, space photovoltaics and power systems 204
Orbital debris, re-entry prediction and disposal 197
Orbit theory, perturbations and orbit transfer 181
Launch vehicles and access to orbit 157
Lifting bodies, the Shuttle orbiter and the reusable demonstrators 140
Reusable launch vehicles, operations and economics 137
Military space, secrecy and space policy 111
Rendezvous, proximity operations and on-orbit servicing 103
Spacecraft propulsion and orbit transfer stages 102
Materials and charging in the orbital environment 100
Spaceplanes and winged orbital vehicles 46
Approach, landing and terminal area energy management 44
The X-37, the X-40 and the Space Maneuver Vehicle 33
Eclipse, sunlight and orbital lighting geometry 21
Total 4,827

This series surveys the contemporary literature comprehensively, in addition to the historical treatment. The subjects below are the ones the article’s relations depend on, surveyed in their modern form, and several of them are far more active now than when this vehicle was designed.

Endurance Became a Battery Problem Everywhere

The relation this article inverts, between cycle life and depth of discharge, was a spacecraft power engineer’s concern in 1999 and is now one of the most heavily studied relations in applied electrochemistry, because every electric vehicle and every grid storage installation depends on it. The spacecraft case is now the small corner of a very large field, and the modern literature on capacity fade, state of health estimation and degradation modelling is far deeper than anything available when this vehicle was designed.

Arrays, Degradation and What Twenty Years on Orbit Does

An array is the one subsystem whose performance is guaranteed to fall throughout a mission, through displacement damage from trapped particles, through atomic oxygen erosion at these altitudes and through ultraviolet darkening of the coverglass. The modern literature quantifies each mechanism separately and reports flight data over intervals comparable to a whole X-37B mission. Those data make the end-of-life margin a computable quantity rather than a rule of thumb.

Thermal Control Moved to Two-Phase Systems and Small Spacecraft

The radiator calculation in this article is a first-law statement and is silent on how the heat reaches the radiator. Heat transport is the harder engineering problem, and the modern literature addresses it. Loop heat pipes and capillary pumped loops move heat across a vehicle passively and against gravity, and their arrival made compact spacecraft thermally tractable in a way that conduction paths and cold plates alone did not.

Thermal Protection Became a Materials Field With Its Own Momentum

TUFROC has a successor and the successor has published. Advanced TUFROC uses a modified surface treatment that lowers the surface temperature by reducing catalytic atom recombination [Advanced TUFROC Thermal Protection System], and it has demonstrated reusability to 2,900 degrees Fahrenheit with single-use capability beyond 3,200 [Caldwell et al]. The material developed for a classified vehicle is documented in the open literature because its developer was a civil agency, and the case illustrates where the compartment boundary runs.

Entry Guidance Became an Optimisation Problem

The equilibrium-glide treatment used above is the analytic ancestor of a field that is now numerical almost throughout. Modern entry guidance solves a constrained trajectory optimisation on board, in real time, against heating, load and control limits, and the reachable-set and footprint literature answers directly the question this article approached through a closed form.

Aerothermodynamics, Computation and the Modern Treatment of Heating

The Sutton and Graves correlation is a 1971 curve fit and it is still the right tool for a bound, so this article uses it. The contemporary literature computes the same quantity from the governing equations with finite-rate chemistry and a surface catalysis model, and its main contribution here is to establish how large the correlation’s error is and in which direction.

Aerobraking Matured at Mars and Came Back

The technique the seventh mission used was first demonstrated at Earth by the Japanese Hiten probe in 1991 and then refined across six planetary spacecraft [Aerobraking]. Magellan aerobraked at Venus in the summer of 1993 [Magellan] and Venus Express in mid-2014 [Venus Express goes gently into the night]. At Mars, Mars Global Surveyor was aerobraking in October 1997 [Mase et al 1998], Mars Odyssey completed its aerobraking on 11 January 2002 [Tartabini et al 2002], the Mars Reconnaissance Orbiter aerobraked for about five months after reaching Mars in March 2006 [Long et al 2007], and the ExoMars Trace Gas Orbiter ended its campaign in February 2018 [Surfing complete]. The literature on corridor control, on atmospheric variability during a campaign, on density reconstruction from accelerometer data and on the thermal limits of using a solar array as a brake is a planetary literature almost in its entirety. Its return to Earth orbit is the interesting part of the seventh mission, and the article that treats it as novel has not read the planetary literature.

Atmospheric Density Modelling and Why the Drag Numbers Carry Uncertainty

Every drag figure in this article rests on a density model, and the modern literature’s main message is that such models are the dominant error source in orbit prediction. The spread between models at a fixed altitude and epoch is comparable to the spread this article attributes to the solar cycle.

Space Situational Awareness Became an Industry

The amateur tracking that made this article possible now has an institutional counterpart, and the modern literature on orbit determination from angles-only observation, on manoeuvre detection and on catalogue maintenance is large, active and largely open.

Debris Mitigation Became the Binding Operational Constraint

One reason the seventh mission’s manoeuvre could be described at all is that debris mitigation is a public obligation, and the literature on disposal, on compliance and on the orbital lifetime of abandoned hardware is correspondingly open. No other area gives a classified programme an affirmative reason to publish.

Reusability, Operations and the Economics That Followed

Reusable launch became ordinary between this vehicle’s first flight and its eighth, and the literature accordingly shifted from feasibility arguments to turnaround, inspection and life-cycle cost. The X-37B is invisible in that shift despite having more reuse experience than most of the vehicles the literature discusses.

Astrodynamics and the Manoeuvre Literature

Guidance, Navigation and Autonomous Landing

Autonomy moved from a certification problem to an expectation. The modern literature treats autonomous approach and landing as a component of a larger autonomy stack rather than as an achievement in itself. That shift is a fair measure of how far the capability the X-37B demonstrated in 2010 has since travelled.

Propulsion and On-Orbit Manoeuvre

The interesting modern development is that a vehicle of this class would now consider electric propulsion for exactly the drag-makeup duty computed above, trading a large increase in specific impulse against power the array of this vehicle does not have.

Payloads, Servicing and Power Beaming

One of the experiments the programme announced belongs to a field that has grown considerably since it flew. Power beaming from orbit is now an active research area with a literature of its own, and the principal investigator of the Photovoltaic Radio-frequency Antenna Module described it as, to the team’s knowledge, the first test in orbit of hardware designed specifically for solar power satellites [NRL Conducts First Test of Solar Power Satellite Hardware in Orbit].

Hypersonic Configuration Aerodynamics

The Institutional Literature on Secrecy and Military Space

On this subject alone, the article’s central difficulty is itself a research field. The literature on classification, on transparency in military space programmes and on the dual-use problem is a political science and law literature rather than an engineering one, and it addresses directly the question of what it costs a technical community when a large body of operational experience is placed beyond citation.

Launch Vehicles and Access

The programme flew on three different launch vehicles from two providers [Boeing X-37]. That variety reflects a change in the environment rather than in the spacecraft, and the seventh mission reached its highly elliptical orbit on a heavy-lift vehicle.

Aerobraking, aerocapture and aeroassisted orbit transfer

The seventh mission’s manoeuvre. Aerobraking, aerocapture and aeroassisted orbit transfer and plane change, with the planetary campaigns that developed them. 275 of these 601 titles name a planet, a moon or a planetary mission, and 139 name aeroassisted flight, 106 of them dated before 2000. The second group is the orbit-transfer literature that studied returning from high orbit through the upper atmosphere, which is the Earth-orbit ancestor of the seventh mission’s manoeuvre.

601 records. [A Neptune Orbiter with 2008] [Abd El-Salam 2005] [Abe 1988] [Abe 1991] [Adriaan Window] [Aeroassisted manned transfer vehicle 1987] [Aeroassisted Orbital Transfer 1994] [Aerobraking for Space Exploration 1992] [Deshmukh et al] [Ai et al 2017] [Albert and Braun 2020] [Albert et al 1992] [Albert et al 2021] [Amundsen et al 2002] [Analysis of Aerothermodynamic Environment 1982] [Andaristiyan et al 2025] [Andiarti et al 1995] [Artis and James 2006] [Augros et al 2002] [Austin et al 1982] [Bailey et al 2003] [Bailey et al 2004] [Balakrishnan and Kamarsu 1992] [Barad et al 2019] [Basic Governing Equations for 1985] [Baumann 2001] [Baumann and Oberle 2000] [Beck et al 2018] [Beerer et al 1996] [Berthet 2025] [Berthet 2025] [Berthet 2026] [Beshaj and Morselli 2024] [Biswell and Puig-Suari 2002] [Biswell et al 1998] [Blosser et al 1985] [Boobar et al 1967] [Bougher et al 1999] [Brand et al 1989] [Braun and Powell 1991] [Braun and Powell 1991] [Braun and Powell 1992] [Braun et al 1992] [Braun and Suit 1988] [Brown and Richardson 2005] [Brown et al 2007] [Bruce 1964] [Bryant et al 1998] [Buck 2006] [Butcher 2025] [Bérend and Bertrand 2009] [Bérend et al 2007] [Heidrich and Dutta] [Cabrera and Spencer 2022] [Cabrera and Spencer 2024] [Cabrera et al 2021] [Calculation of Nonequilibrium Radiation 1985] [Calhoun et al 2002] [Calise and Bae 1988] [Calise and Melamed 1995] [Calise and Duckeman 1994] [Campbell et al 2017] [Carpenter 1993] [Carrelli et al 2014] [Casalino et al 1996] [Castelli 2006] [Castellini et al 2018] [Castellini et al 2019] [Celenligil et al 1988] [Chadalavada et al] [Chadalavada et al 2025] [Chadalavada et al 2025] [Chadalavada et al 2026] [Chakrabarty et al 2016] [Chapel et al 2005] [Charalambous et al 1992] [Charalambous et al 1995] [Chavis and Wilmoth 2005] [Chen and Yang 2007] [Chen et al 2022] [Chern et al 1992] [Choi et al 2025] [Cihan] [Cihan and Kluever 2022] [Conrath et al 2000] [Cooper et al 1985] [Craig and Lyne 2002] [Cross 1982] [Crouse and Lewis 1993] [Cruz 1979] [Cruz 1979] [Cruz 1980] [Cruz 1983] [Cuadra and Arthur 1966] [Cui and Li 2023] [Cui and Li 2024] [Cui et al 2026] [Cuthbert et al 1990] [Nguyen et al 2024] [Darby and Rao 2011] [Dastoor et al 2026] [Daum 1992] [de Divitiis 1999] [Dec 2007] [Dec et al 2007] [Demcak et al 2020] [Denis et al 2018] [Deshmukh et al] [Deshmukh et al 2020] [Deshmukh et al 2021] [Deshmukh et al 2022] [Deshmukh et al 2023] [Deshmukh et al 2025] [Deshmukh et al 2019] [Design and Performance Analysis 1985] [Dickmanns 1986] [Dogra et al 1994] [Doody 1995] [Dowdy 1968] [Dutta] [Dutta] [Dutta 2020] [Dutta et al] [Dutta et al] [Dutta et al] [Dutta et al] [Dutta et al] [Duvall et al 2005] [Dwyer et al 2002] [Dyke 2003] [Dyke and Hrinda 2004] [Dyke and Hrinda 2007] [Edquist et al 2004] [Einarsson 1999] [Eldred 1993] [Elices 1995] [Engelsma and Mooij 2020] [Ess 1990] [Ess and Munday 1989] [Evans, Steven W. and Dukeman, Greg A. 1993] [Evans and Dukeman 1995] [Falcone and Putnam 2021] [Falcone and Putnam 2022] [Falcone and Putnam 2022] [Falcone and Putnam 2023] [Feng et al 2017] [Finchenko et al 2001] [Fitzgerald and Ward 1988] [Florence 1981] [Florence and Fischer 1983] [Forbes and Zhang 2018] [Forbes et al 2021] [Fornari and Pontani 2023] [French and McRonald 1980] [French and Uphoff 1979] [Fritts et al 2006] [Fu et al 2013] [Fuhr and Rao 2018] [Fujita and Narita 2013] [Fujita and Yamada 2008] [Fujita et al 2012] [Gamber and Rogers 1989] [Gamble et al 1983] [Garg 2025] [Gates and Longuski 2010] [Geiser and Matz] [Geiser and Matz 2022] [Gelly and Vernis 2009] [Generic aerocapture atmospheric entry 1980] [Ghiugan et al 2026] [Ghosh and Conway 2015] [Gilbert et al 1991] [Gildfind et al 2019] [Gildfind et al 2021] [Gildfind et al 2022] [Gildfind et al 2025] [Girija 2019] [Girija 2019] [Girija 2020] [Girija 2023] [Girija et al 2020] [Girija et al 2021] [Girija et al 2023] [Gladden 2008] [Gochenaur et al 2025] [Gochenaur et al 2026] [Gochenaur et al 2026] [Gogu et al 2009] [Gomes dos Santos et al 2013] [Gomez-Delrio and Dutta 2024] [Gomez-Delrio et al 2025] [Grace et al 2022] [Graves and Masciarelli 2002] [Green et al 1984] [Grigoryev and Ershov 2024] [Guelman 1997] [Guglielmi and Le Carpentier 1993] [Gulick and Edquist 1998] [Gupta 1993] [Gur et al 1990] [Gurley 1993] [Haas and Schmitt 1994] [Hall 2000] [Hall 2002] [Hall 2002] [Hall et al 2003] [Halyo and Taylor 1989] [Hamel and de Lafontaine 2005] [Hamilton et al 1991] [Han and Qiao 2017] [Hanak and Bishop 2004] [Hanak et al 2003] [Hancock et al 2018] [Hanna and Toison 2002] [Hanna et al 2002] [Hassan and Candler 1993] [Hassan et al 1992] [Hassett 1980] [Hastie] [Haw 2003] [Haw 2003] [Heidrich and Braun 2020] [Heppenheimer 1971] [Herman 1986] [Heyman et al 1982] [Hibbard et al 2012] [Higginbotham et al 2024] [Higginbotham et al 2026] [Hoffman 1984] [Hongwei Han et al 2016] [Horie and Conway 1999] [Hrinda 2003] [Hsu et al 1990] [Hull et al 1985] [Hyde] [Ikawa 1988] [Ikawa and Rudiger 1982] [Ishimoto 1992] [Jaensch and Well 1994] [Jah et al 2008] [James and Munk 2003] [James et al 2003] [James et al 2003] [Jesch et al 2019] [Jits 2002] [Jits and Walberg 1998] [Jits and Walberg 2004] [Jits et al 2005] [Johnson 2004] [Johnson and Lyons 2004] [Johnson and Willcockson] [Johnson et al 2002] [Johnson et al 2003] [Johnson et al 2003] [Johnson et al 2004] [Jones et al 1987] [Aerothermal and TPS Analysis] [Joshi et al 2000] [Analysis of the Fully] [Justus et al 2004] [Justus et al 2003] [Justus et al 2005] [Justus et al 2005] [Katsurayama 2015] [Katsurayama and Abe 2010] [Katsurayama and Abe 2011] [Katsurayama and Abe 2011] [Katsurayama and Abe 2012] [Katsurayama and Abe 2013] [Katsurayama and Abe 2014] [Katsurayama et al 2011] [Katsurayama et al 2019] [Kazmierczak and Nakhjiri 2018] [Kechichian et al 1982] [Kechichian et al 1983] [Kelly and Little 2019] [Kelly and Little 2021] [Kenworthy et al 2007] [Keys 2006] [Keys et al 2006] [Kirtley and Slough 2014] [Komar et al] [Koura 1987] [Kozynchenko 2013] [Kumar and Tewari 2005] [Kumar and Tewari 2006] [Kuo and Liu 2000] [Kuo and Liu 2002] [La Marca 2023] [Laub 2002] [Laub 2003] [Laub and Chen 2004] [Laure and Auweter-Kurtz 1994] [Lawson 1989] [Ledkov 2012] [Ledoux and Vas 1991] [Lee 1985] [Lee and Grantham 1989] [Lee and Hull 1990] [Lefevre] [Lefevre et al 2019] [Lefevre et al 2021] [Lefevre et al 2025] [Lemmerman and Wercinski 1997] [Leng et al 2025] [Leng et al 2027] [Letts and Pelekanos 1982] [Lewis] [Lewis et al 2007] [Leyland et al 2009] [Li and Nan 2026] [Li et al 2014] [Li et al 2022] [Liu and Liu 2011] [Lockwood 2003] [Lockwood 2004] [Lockwood et al 2006] [Lockwood et al 2006] [Lockwood et al 2006] [Lohar et al 1998] [Long et al 2026] [Long et al 2007] [Long et al 2008] [Longuski et al 1995] [Longuski et al 1995] [Longuski et al 1999] [Low Lift-to-Drag Aerobrake Heat-Transfer 1985] [Lu 2020] [Lu and Saikia 2018] [Lu and Santana 2023] [Lu et al 2015] [Lugo et al] [Luo and Topputo 2021] [Lyne 1992] [Lyons 1999] [Lyons 2001] [Lyons 2012] [Lyons and Johnson 2004] [Lyons et al 1995] [Lyons et al 1999] [Lyons 2002] [Ma 1996] [Maddock et al 2012] [Martinez et al 2021] [Masciarelli and Queen 2003] [Masciarelli et al 2000] [Masciarelli et al 2004] [Mase et al 1998] [Matz and Cerimele 2020] [Matz et al 2017] [Mazarico et al 2007] [Mazzaracchio 2013] [Mazzaracchio 2013] [Mazzaracchio and Marchetti 2012] [McClure and Colangelo 2026] [McEneaney 1991] [McFarland and Calise 1993] [McFarland and Calise 1995] [McRonald et al 2003] [Mease and Vinh 1985] [Mease and Vinh 1983] [Measuring Lift Coefficient in 1994] [Melamed and Calise 1995] [Menees 1985] [Meng et al 2020] [Mercer] [Merritt 2015] [Meyer et al 1995] [Miele 1996] [Miele and Basapur 1985] [Miele and Lee 1994] [Miele and Venkataraman 1984] [Miele and Wang 1992] [Miele and Wang 1996] [Miele and Wang 1996] [Miele et al 1987] [Miele et al 1988] [Miele et al 1990] [Miele et al 1990] [Miele et al 1991] [Miele and Venkataraman 1983] [Miele and Wang 1990] [Miele et al 1986] [Miele et al 1987] [Miele et al 1987] [Miele, A. et al 1988] [Minton et al 2004] [Mishne and Speyer 1986] [Mishne et al 1990] [Mishne et al 1997] [Morgan and Williams 2025] [Morgan et al] [Moses 2005] [Moudden and Forbes 2008] [Moudden and Forbes 2010] [Moudden and Forbes 2015] [Multiple Pass Trajectories for 1985] [Munk 2006] [Munk and Moon 2008] [Munk et al 2005] [Muramatsu et al 2026] [Müller-Wodarg et al 2016] [Naidu 1991] [Naidu 1993] [Naidu and Li] [Naidu et al 1990] [Naidu et al 1993] [Newlands] [Nguyen et al] [Nixon et al 2016] [Noca and Bailey 2003] [Noca and Bailey 2004] [Ogilvie et al 2023] [Okhotsimsky et al 1978] [Optimization of Low Thrust 2004] [Orlandini et al 2024] [Orlandini et al 2026] [Otsu et al 2008] [Otsu et al 2008] [Otsu et al 2009] [Palazzo 2025] [Parent et al 2024] [Parent et al 2025] [Park 1987] [Park 2000] [Park 2011] [Particle Simulation of Satellite 1994] [Performance Aerodynamics of Aeroassisted 1985] [Perot and Rousseau 2002] [Pertz et al] [Pertz et al 2026] [Pitts and Murbach 1986] [Pontani and Teofilatto 2012] [Portock et al 1999] [Powell 1998] [Powell and Braun 1992] [Pradeepkumar Girija 2023] [Pradeepkumar Girija 2025] [Pradeepkumar Girija 2025] [Prince et al 2009] [Prince and Striepe 2007] [Problems of Rate Chemistry 1985] [Puig-Suari 1997] [Puig-Suari and Longuski 1992] [Putnam and Braun 2013] [Putnam et al] [Putnam et al 2012] [Moses et al] [Rabinskii et al 2019] [Rao et al 2002] [Rasheed et al 2001] [Rataczak et al 2024] [Rataczak et al 2025] [Rataczak et al 2025] [Rault et al 1996] [Repic and Eyman 1969] [Repic et al 1968] [Restrepo et al 2024] [Reza et al 2007] [Ridderhof and Tsiotras 2020] [Ridderhof et al 2022] [Ro and Queen 1998] [Rochelle et al 1990] [Roelke et al] [Roelke et al 2019] [Deshmukh 2024] [Deshmukh et al 2020] [Rohrschneider and Braun 2007] [Rollock and Braun 2020] [Rousseau et al 2002] [Rozanov and Guelman 2008] [Saikia et al 2021] [Sanders 1996] [Sandoval and Matz 2025] [Sarli et al 2018] [Sasiadek 1996] [Saturn / Titan Rendezvous 2004] [Schmitt 1983] [Schy and White 1969] [Scoggins et al 2024] [Scoggins et al 2025] [Senses and Rao 2012] [Serrano-Martinez and Hechler 1989] [Seywald 1994] [Seywald 1996] [Shellabarger et al] [Shellabarger et al 2024] [Shelton] [Shi, Yun Yuan and Young, D. H. 1991] [Shi et al 1990] [Shinn and Jones 1985] [Simha et al 2026] [Singh et al 2025] [Skalecki et al 1984] [Skokova and Laub 2005] [Slough 2020] [Smith and Bell 2005] [Smith et al 2000] [Smith et al 2022] [Sonandres et al 2025] [Sonandres et al 2025] [Spencer and Tolson 2005] [Spencer and Tolson 2007] [Speyer and Crues 1990] [Srivastava and Mishra 2023] [Starr and Westhelle 2005] [Starr et al 2004] [Strauss 1975] [Suwata and Matsuda 2018] [Suwata et al 2018] [Suzuki and Abe 1993] [Suzuki et al 1995] [Takashima et al 2003] [Takayanagi and Fujita 2012] [Takayanagi and Fujita 2013] [Talay et al 1984] [Tan et al 2018] [Tan et al 2018] [Tao Guo et al 2010] [Taratuta et al 1992] [Tartabini et al 2005] [Tartabini et al 2002] [Tauber et al 1991] [Tauber 1994] [Teng et al 2022] [Teng et al 2025] [Thermal Design of Aeroassisted 1985] [Thermal Response of an 1985] [Thermophysical and Systems Integration 1981] [Thorp and Pierson 1995] [Tolson et al 2005] [Tolson et al 2006] [Tolson et al 2007] [Tolson et al 2008] [Tolson et al 2013] [Tolson et al 2002] [Tragesser and Longuski 1996] [Tragesser and Umbert 2021] [Tragesser et al 1994] [Tragesser et al 1997] [Trask and Coverstone 2004] [Urraza Atue and Bruce 2025] [Usuki and Tsuda 2026] [Val Serra et al 2011] [van Oeveren and Gildfind 2023] [van Oeveren et al 2025] [Vaughan et al 2005] [Venkatapathy et al 2021] [Vernis and Ball 2023] [Vijayaraghavan 1992] [Vinh and Hanson 1985] [Vinh and Johannesen 1986] [Vinh and Ma 1990] [Vinh et al 1986] [Vinh et al 2000] [Walberg 1985] [Walberg 1991] [Walberg 1982] [Walberg 1983] [Walberg, G. D. et al 1987] [Wallace and You 2019] [Wang and Li 2021] [Wang et al 2004] [Wang et al 2006] [Webb] [Webb et al 2017] [Wercinski] [Wercinski and Langhoff 1997] [Wercinski et al 2002] [Werner and Braun 2019] [Westhelle and Masciarelli 2003] [White and Hethcoat 1977] [Whitmore et al 2006] [Wilder et al 2020] [Wilkerson 1998] [Williams 2017] [Williams et al] [Williams et al 1990] [Winovich et al 1985] [Withers 2006] [Woo and Coverstone 2003] [Wright et al 2004] [Wright et al 2006] [Xi et al 2021] [Xiangdong et al 2023] [Yan et al 2017] [Yang et al 2020] [Yang et al 2026] [Yao et al 2024] [Yu et al 2020] [Yu et al 2026] [Yu et al 2026] [Zhang et al 2010] [Zhao and Garrard 1992] [Zhao et al 2024] [Zimmermann and Calise 1995] [Zimmermann and Calise 1998] [Zucchelli and Mooij 2018] [Zucchelli et al 2021] [Zumwalt et al 2010] [Şenses and Rao 2013]

Thermal protection materials and systems

The vehicle’s one public innovation and its field. Reusable and ablative thermal protection, ceramic tiles, carbon composites, ultra-high temperature ceramics and leading edges. 48 titles name ultra-high temperature ceramics, and 44 of those date from 2012 or later, which is the clearest sign of the field’s momentum.

359 records. [Recent Developments of Thermal] [Caldwell et al] [Caldwell et al] [Caldwell et al] [Caldwell et al] [Agarwal and Nisar 2025] [Ai et al 2022] [Albano et al 2013] [Identification and Study of] [Ammendola et al 2025] [Antuf’ev 2017] [Appar and Kumar 2021] [Application of combined heat transfer models for designing thermal protection systems of reusable launch vehicles 2012] [Aprovitola et al 2019] [Arai et al 2019] [Aronov and Klyagin 2021] [Avery 1978] [Avery, D. E. 1981] [Avery, D. E. 1984] [Avery, D. E. et al 1981] [Backman et al 2024] [Backman et al 2024] [Baker and Kramer 1982] [Ballard et al 2010] [Baluragi et al 2011] [Başkaya and Hickel 2025] [Beck et al 2014] [Biamino et al 2008] [Biamino et al 2010] [Biberman et al 1980] [Bodnya and Timoshenko 2018] [Wesely et al] [Borrelli et al 2009] [Bose et al 2014] [Bose, Deepak et al 2016] [Bramer et al 1971] [Brian R Hollis and Kevin E Hollingsworth 2023] [Brian R Hollis and Kevin E Hollingsworth 2025] [Brociek et al 2023] [Brociek et al 2023] [Bessire et al] [Brodzik and Frackowiak 2019] [Bustard et al 1970] [Cai et al 2024] [Cao et al 2020] [Caogen et al 2008] [Chang et al 2022] [Chen and Chen 2014] [Chen et al 2014] [Chen et al 2018] [Chen et al 2023] [Chen et al 2025] [Chen et al 2026] [Chen et al 2002] [Cheng 2020] [Cheng et al 2011] [Cheng et al 2026] [Chinnaraj et al 2024] [Clarke 2008] [Clayton and Tinker 1992] [Cooper et al 1992] [Crawford 1971] [Crose and McKinley 1972] [Cui et al 2017] [Curry et al 1979] [Cygan et al 2025] [Dang et al 2021] [Daniel B Leiser et al 2001] [Daryabeigi 2002] [David A. Stewart et al 2024] [Davis et al 1999] [De Prisco et al 2026] [del Val et al 2022] [DelPapa 2005] [Dhanasekaran et al 2011] [Diaconis et al 1961] [Diao et al 2025] [Ding et al 2020] [Dolan et al 1966] [Dotts, R. L. et al 1985] [Dowell 1975] [Drawin 1993] [Duston et al 2004] [Ericsson 1967] [Fahrenholtz and Hilmas 2017] [Fan 2015] [Feldman, Jay et al 2019] [Feng et al 2024] [Feng et al 2025] [Feng et al 2025] [Feng et al 2026] [Ferraiuolo and Manca 2012] [Flight set 360L007 STS-33R 1990] [Foster et al 1973] [Fujino and Ishikawa 2006] [Gao and Zhu 2025] [Gao et al 2021] [Gao et al 2026] [Gogu et al 2009] [Goldstein et al 1973] [Gong et al 2018] [Gorton, Mark P. et al 1993] [Goyer and Tallon 2023] [Green et al 1984] [Gu et al 2017] [Gulli and Maddalena 2014] [Gulli et al 2014] [Gulli et al 2015] [Guo et al 2020] [Gupta and Ramkumar 2015] [Gupta et al 1992] [Haas 1972] [Hammitt 1965] [Han and Han 2024] [Han et al 2020] [Hannah and Muessig 1970] [Hasnain 2016] [Hassan et al 2024] [He et al 2022] [He et al 2025] [Heller 1967] [Henline 1992] [Hongpeng and Weiqiang 2016] [Hou et al 2022] [Hovey 1965] [Huang and Dai 2023] [Huang and Yao 2020] [Huang et al 2025] [Hundhausen et al 2007] [Hunt, L. R. 1976] [Hunt, L. R. and Bohon, H. L. 1974] [Hunt, L. R. et al 1976] [Hwang et al 2016] [Ikenson 2025] [Study of Orbiter Wing] [Advanced TUFROC Thermal Protection] [Jiang et al 2020] [Jie Liang, Zhihui Li, Xuguo Li and Weibo Shi 2020] [Jin et al 2018] [Jin et al 2019] [Jin et al 2024] [Jing et al 2026] [Johnson, Sylvia M. 2000] [Kasen and Wadley 2019] [Kashyap and Mitra 2020] [Kashyap and Mitra 2026] [Katiyar and Balasubramanian 2014] [Kaufman 1970] [Kavoosi et al 2026] [Ke et al 2025] [Khan and Chakraborty 2023] [Khrapko 2018] [Kim 2017] [Kim and Choi 2026] [Kim et al 2020] [Kim et al 2024] [King et al 2019] [Koch et al 2025] [Komine and Kobayashi 1983] [Kourtides, Demetrius et al 1997] [Kowal 2010] [Kowal, T. John 2011] [Kubota and Uchida 1999] [Kumar and Mahulikar 2016] [Kumar and Mahulikar 2016] [Kumar and Mahulikar 2017] [Kundu 2013] [Lai and Leu 2023] [Lan et al 2026] [Le and Goo 2021] [Le et al 2021] [Leiser, Daniel B. et al 2002] [Levine, Stanley R. et al 2003] [Levine, Stanley R. et al 2004] [Li et al 2012] [Li et al 2015] [Li et al 2018] [Li et al 2020] [Li et al 2021] [Li et al 2025] [Li et al 2026] [Li et al 2026] [Lin et al 2015] [Liu and Jiang 2013] [Liu et al 2002] [Liu et al 2023] [Lu and Liu 2013] [Lu et al 2026] [Lu Hai-Bo and Liu Wei-Qiang 2012] [Luo et al 2025] [Luo et al 2026] [Karthikraja et al 2026] [Mahulikar et al 2008] [Maiorova et al 2016] [Artemis I Space Launch] [Space Launch System Base] [Marley and Driscoll 2022] [Marraffa and Smith 1998] [Matienzo et al 1985] [Maxwell and Hoang 2016] [Meyer and Barneburg 1988] [Miller-Oana and Corral 2015] [Milos 1998] [Milos and Squire 1996] [Milos and Squire 1999] [Milos et al 2014] [Mohan et al 1996] [Monti et al 2006] [Mor et al 2025] [Morris et al 2023] [Morrison 1975] [Mullenix and Povitsky 2016] [Myers, David E. et al 1999] [Myers, David E. et al 2000] [Myers, Franklin K. et al 2003] [Nakamura and Fujii 2006] [Natali et al 2013] [Nettles et al 2011] [Nisar et al 2017] [Nisar et al 2022] [Nisar et al 2023] [Nowak et al 2021] [Nykiel et al 2026] [Ogasawara et al 2003] [Ohtake 1998] [Ormiston 1974] [Ortona et al 2013] [Paciorri et al 2026] [Pallix 1994] [Palmer et al 1997] [Park 1983] [Park 1983] [Peterson 1970] [Petley et al 1983] [Piacquadio et al 2023] [Pichon et al 2009] [Pitts and Kourtides 1989] [Platus 1985] [Povolny et al 2022] [Price et al 2025] [Qiao et al 2022] [Qiao et al 2023] [Qiao et al 2024] [Qin et al 2017] [Qu et al 2015] [Qu et al 2019] [Radiative, Ablative, and Active 1972] [Rahimi et al 2026] [Rasky et al 2001] [Rasky, Dan J. et al 2000] [Reinikka and Wells 1964] [Ren et al 2014] [Ren et al 2021] [Research Progress in Carbide Ultra-high Temperature Ceramics for Equipment Thermal Protection 2025] [Rezin, Marc et al 2001] [Reznik et al 2019] [Reznikov 1965] [Rishad et al 2025] [Ritzert and Nesbitt 2007] [Rodriguez et al 1990] [Rogers et al 1976] [Rong 2017] [Rong et al 2016] [Ronquillo and Williams 1984] [Roth et al 2011] [Roth et al 2009] [Roth et al 2010] [Rubio et al 2018] [Ruperti et al 2004] [Saha 2023] [Sanson et al 2017] [Savino et al 2018] [Schomburg et al 1983] [Scoville and Rajula 2005] [Shao et al 2017] [Shao et al 2026] [Shen and Liu 2020] [Sherman 1978] [Shi et al 2021] [Shin et al 2023] [Shojaie-bahaabad et al 2024] [Shorenstein 1971] [Singh, M. 2007] [Skolnik and Putnam 2022] [Skripnyak and Skripnyak 2017] [Stanley, Thomas Troy et al 2000] [Steeves and Evans 2011] [Steverding 1965] [Stewart and Leiser 1993] [Stewart and Leiser 2006] [Stewart, David and Leiser, Daniel 2007] [Stewart, Michael et al 2018] [Strauss and Boensch 1973] [Sun and Zhu 2019] [Sun Jian and Liu Wei-Qiang 2014] [Surzhikov 2018] [Surzhikov 2018] [Suvorova et al 2023] [Suzuki et al 2002] [Symposium on Reusable Surface 1973] [Symposium on Reusable Surface 1973] [Tancredi and Grassi 2007] [Thermal Protection for a Re-Entry Vehicle Using Heat Ablation Process 2015] [Thompkins et al 1980] [Tian et al 2023] [Tian et al 2025] [Tian et al 2025] [Tiede 1972] [Tobe and Grandhi 2013] [White et al 2020] [Tropp 1966] [Vanmol and Anderson 1992] [Walker and Richter 2006] [Wang and Luo 2022] [Wang and Zhang 2022] [Wang et al 2019] [Wang et al 2022] [Wang et al 2023] [Wang et al 2024] [Wartemann et al 2023] [Wei et al 2012] [White 2010] [Wilkinson 1990] [Willey 1993] [Williams and Curry 1972] [Williams et al 1995] [Williams and Imprescia 1975] [Wilson and Galatzer 2008] [Winter et al 2011] [Wright et al 2006] [Wright et al 2007] [Wurster, K. E. and Stone, H. W. 1993] [Xie et al 2013] [Xie et al 2020] [Xu and Wu 2018] [Xu and Zhai 2001] [Xue et al 2026] [Yamada and Inatani 2002] [Yamada et al 2002] [Yamao et al 2001] [Yang et al 2018] [Yang et al 2024] [Yu et al 2025] [Zapata-Solvas et al 2015] [Zarubin et al 2022] [Zhang 2025] [Zhang and Wang 2025] [Zhang et al 2018] [Zhang et al 2024] [Zhao et al 2025] [Zhao et al 2026] [Zheng et al 2025] [Zhou et al 2017] [Zhou et al 2022] [Zhu and Li 2020] [Zhu et al 2016] [Zhuang and Ridley 2024] [Zinchenko et al 2018] [Zuccarini 2024]

The upper atmosphere, density models and satellite drag

The drag figures. The upper atmosphere, thermospheric density and its models, the solar cycle, satellite drag coefficients and orbital decay.

342 records. [A method of compensation for mismodelling of terrestrial atmospheric density in precision orbit determination 1998] [Ai et al 2023] [Anderson 1966] [Anderson et al 2013] [Andrews and Berthoud 2020] [Anitha and Sharma 2011] [Antreasian et al 1991] [Appar and Poovathingal 2026] [Arnas 2021] [Ashruf et al 2024] [Awad and Hassan 1995] [Awad et al 1999] [Banks 1978] [Barato 2023] [Bass 1980] [Bates 1962] [Binebrink et al 1989] [Blanchfield et al 2025] [Blitzer 1971] [Blum 1972] [Bobojć 2008] [Bogoi et al 2025] [Borg and Söderholm 2008] [Boulton 1983] [Boulton and Swinerd 1983] [Bowamn 1975] [Bowden 2022] [Bramson 1969] [Brouwer and Hori 1961] [Brouwer and Hori 1961] [Brower and Hori 1960] [Bruce 1961] [Bruinsma et al 2018] [Bös et al 2025] [Cable, Samual B. et al 2011] [Calabia and Jin 2019] [Calabia et al 2020] [Variation in Predicted Orbital] [Cang et al 2016] [Cano et al 2025] [Canuto 2013] [Canuto and Massotti 2008] [Canuto and Massotti 2010] [Canuto et al 2010] [Canuto et al 2014] [Cao and Li 2016] [Cao et al 2025] [Capon et al 2019] [Chakravarty 1980] [Challinor 1968] [Chemistry of the upper atmosphere 1964] [Chen and Sang 2016] [Chen et al 2014] [Chen et al 2017] [Chen et al 2023] [Chen et al 2025] [Cheng et al 2024] [Chilò et al 2026] [Ching 1972] [Ching and Rugge 1975] [Ching et al 1977] [Citron 1963] [Concerning molecular nitrogen in the upper atmosphere 1962] [Cook 1965] [Cook 1967] [Cook and Plimmer 1960] [Corbin and Kusche 2022] [COSPAR International Reference Atmosphere: 0-120 km (1986) 1992] [Courtney Ray and Debra 1976] [Cương and Tú 2012] [Gershman 2026] [Danilov 1962] [Dasenbrock 1970] [De Lafontaine and Garg 1982] [Delhaise 1991] [Delhaise 1994] [Design requirements for orbit 1980] [Dietrich et al 2022] [Ding et al 2025] [Lin et al 2022] [Doornbos et al 2005] [Dowd and Tapley 1979] [El’Iasberg and Yastrebov 1961] [El-salam and Sehnal 2004] [Elvidge et al 2016] [Emmert 2015] [Emmert 2015] [Emmert et al 2006] [Endo et al 2025] [Fan et al 2023] [Fearn 2005] [Fearn and Rijm 2002] [Fleck and Starin 2003] [Forbes 2001] [Forootan et al 2022] [Forootan et al 2023] [Fredrick et al 2025] [Fulgham and Tobiska 2013] [Fulgham et al 2012] [Geyling 1964] [Ghazavi et al 2025] [Ghisi et al 2014] [Gombosi 2007] [Gondelach and Linares 2020] [Gondelach and Linares 2021] [Graham and DuFore 1993] [Greer 1980] [Greer 1990] [Groves 1958] [Groves 1959] [Groves 1961] [Groves 1965] [Guan et al 2025] [Guilherme et al 2006] [Liu et al 2023] [Guo et al 2024] [Guo et al 2025] [Guo et al 2026] [Global Reference Atmospheric Model] [Hall 1972] [Hao et al 2022] [Harrison and Gibson 1981] [Hatten and Russell 2017] [He et al 2024] [Hedin 1983] [Hedin et al 1977] [Hsu et al 2016] [Huang and He 1988] [Ibrahim and Saleh 2021] [Imbro et al 1975] [Imoto et al 2025] [Jacchia 1960] [Jacchia 1967] [Jacchia and Slowey 1964] [Jacchia et al 1969] [Jacchia 1992] [Yue et al 2019] [Jiang and Zhang 2026] [Johnson and Herrmann 1999] [Jones and Swinerd 1990] [Justh et al 2006] [Kai et al 2025] [Kalarus et al 2022] [Kaplan and Jones 1983] [Karr 1985] [Kato et al 1979] [Kayser 1988] [Kelly 1988] [Kim et al 2006] [King 1975] [King-Hele and Leslie 1958] [King-Hele and Rees 1963] [King-Hele and Scott 1969] [King-Hele and Walker 1972] [King-Hele and Walker 1987] [Knowles 1986] [Knowles et al 2001] [Kong et al 2018] [Kong et al 2018] [Korlaelci et al 2026] [Kosary et al 2024] [Krassovsky 1959] [Krückel and Hobiger 2026] [Kuijper and Matatoros 2012] [Langer et al 2025] [LeBlanc 1981] [Lechtenberg et al 2013] [Leslie and Justus 2008] [Li 2011] [Li 2011] [Li and Close 2015] [Li et al 2007] [Li et al 2017] [Li et al 2023] [Li et al 2024] [Li et al 2025] [Li et al 2025] [Licata and Mehta 2022] [Licata et al 2022] [Liu et al 2013] [Liu et al 2019] [Liu et al 2023] [Liu et al 2026] [Liu et al 2026] [Qian et al 2022] [Lowe and D’Amico 2026] [Lu et al 2020] [Maat 2010] [Mangust et al 1995] [Marchetti et al 2006] [Marcos 1990] [Matsuo et al 2012] [McDonald 1979] [McDonnell et al 1996] [McLaughlin et al 2013] [Mehta and Linares 2020] [Mehta et al 2018] [Mei and Zong 2025] [Mioc 1991] [Miyamoto et al 2026] [Moe 1968] [Moe et al 1976] [Moe et al 1993] [Moe et al 1998] [Molina and Scherliess 2023] [Mueller 1982] [Murad 1996] [Mutschler et al 2026] [Nair and Sharma 2003] [Nakamura 2026] [Nateghi and Manzi 2023] [National Geophysical Data Center 1992] [Nazarenko et al 1991] [Newton et al 1964] [Newton et al 1965] [Nguyen and Conklin 2015] [Nicholas et al 2000] [Nigam 1964] [Ning and Wu 2024] [Niu et al 2014] [Noga et al 2023] [Nwankwo and Chakrabarti 2014] [Oliveira and Zesta 2019] [Ovchinnikov et al 2024] [Ovchinnikov et al 2026] [Palmer 2024] [Pan et al 2025] [Panzetta et al 2018] [Pardini and Anselmo 2001] [Pardini et al 2006] [Pardini et al 2012] [Parks 1982] [Parkyn 1958] [Parkyn 1960] [Parsons 1962] [Patterson 1966] [Penko et al 1985] [Petzold et al 2025] [Physics of the upper atmosphere 1973] [Prag 1983] [Priester et al 1960] [Pérez et al 2014] [Rees 1992] [Ren and Lei 2023] [Ren et al 2022] [Rigler et al 2012] [Rishbeth 1981] [Roberson 1958] [Roberts 2000] [Robinson 2012] [Robson et al 2021] [Roemer et al 1979] [Ross and Alfriend 1995] [Rubincam 1980] [Rubincam 1987] [Rugge and Ching 1975] [Saad 2011] [Sakai and Takahashi 2024] [Sakai and Takahashi 2026] [Scherf et al 2026] [Schiemenz et al 2019] [Schiemenz et al 2020] [Science Communication Inc McLean Va 1960] [Sehnal 1986] [Shapiro 1964] [Sharpe and Murray 2017] [She et al 2025] [Shefov 1963] [Shepherd and Cho 2013] [Shoemaker et al 2015] [Shultz 2020] [Sicoli and Mehta 2026] [Siddique et al 2022] [Silverberg and Redmond 1992] [Singh 2026] [Siry 1959] [Slowey 1984] [Smith 1966] [Smith 1988] [Smith et al 1997] [Sochacki and Narkiewicz 2021] [Speake and Aston 2005] [Sterne 1958] [Stirton 1960] [Sun et al 2026] [Swartz et al 1972] [Swinbank and Ortland 2003] [Tan 1998] [Tan and Badhwar 1997] [Theil and Silas-Guilherme 2005] [Tobiska 2003] [Truttse 1968] [Truttse 1968] [Truttse 1969] [Valeev 1965] [Vallado and Finkleman 2014] [Vampola 1989] [Van Woerkom 1981] [Vedder and Tabor 1992] [Vinh et al 1979] [Vinti 1959] [Volkov et al 2011] [Volland 1981] [Vourlidas and Bruinsma 2018] [Vukovich and Kim 2019] [Walsh et al 2021] [Wang and Bai 2023] [Wang and Bai 2024] [Wang and Bai 2026] [Wang and Gou 2025] [Wang et al 2023] [Ward et al 1990] [Warnock and Cochran 1995] [Weng et al 2012] [Weng et al 2017] [Weng et al 2019] [Westerman 1963] [Westerman 1963] [White et al 1994] [Wildhack 1958] [Winters and Winters 1992] [Withbroe 1989] [Wong et al 2026] [Wu 1963] [Wyatt 1960] [Xiong et al 2018] [Xu et al 2010] [Ya-Ying 1991] [Yamamoto 2026] [Yamamoto and Sori 2026] [Yamazaki et al 2015] [Yao et al 2026] [Yu et al 2019] [Yu et al 2025] [Yuan et al 2025] [Yue et al 2023] [Zeitler et al 2021] [Zhang et al 2019] [Zhang et al 2019] [Zhang et al 2025] [Zhang et al 2025] [Zhou et al 2009]

Spacecraft thermal control, radiators and heat transport

The radiator bound. Spacecraft thermal control, radiators, coatings, multilayer insulation, heat pipes, loop heat pipes and capillary pumped loops. 167 of these 341 titles name a heat pipe, a capillary pumped loop or another two-phase system, which is the transport problem that the radiator calculation leaves aside.

341 records. [A Study on the Heat Transfer Performance of Evaporators Through Metal Foam of Wickless Loop Heat Pipe 2024] [Adoni et al 2012] [Alario and Otterstedt 1986] [Alotaibi et al 2026] [Modular Assembled Radiators for] [Ambrose 2019] [Anderson and Hattar 1988] [Anderson et al 2001] [van Paridon et al 2024] [Araneo et al 2021] [Baek and Jung 2022] [Bai et al 2014] [Baldauff et al 2008] [Bartosik and Babel 1990] [Basha et al 2014] [Beasley 2004] [Belyavskii et al 2022] [Betancur et al 2020] [Bhagat and Watt 2016] [Bhattad and Aneesha 2025] [Birur and Ku 2001] [Birur 2008] [Bonneville 1971] [Borkar and Pachghare 2014] [Bosma and Levadou 1980] [Bowman, Cheryl L. et al 2007] [Bradley and Foss 1987] [Buck et al 1993] [Bulut 2025] [Butler and Hoang 1991] [Butler and Hoang 1992] [Butler and McIntosh 1990] [Butler et al 1995] [Callinan and Berggren 1959] [Carek et al 2000] [Carruth et al 1992] [Chalmers 1985] [Chalmers et al 1993] [Chapter and Johnsen 1974] [Chen 2010] [Chen 2011] [Chen 2011] [Chen et al 2021] [Chen et al 2025] [Cheng et al 2011] [Cho et al 2022] [Ciofalo et al 2016] [Cognata et al 2014] [Colwell and Hartley 1987] [Copeland et al 2005] [Cunnington et al 1965] [Cunnington et al 1967] [Currano et al 2008] [Daimaru et al 2018] [Butler 1985] [Daryabeigi et al 2006] [Delcov et al 2015] [Demiryont and Moorehead 2009] [Design Optimization for Loop Heat Pipe Using Tabu Search 2009] [Determination of thermal radiation incident upon the surfaces of an earth satellite in an elliptical orbit 1960] [Dever et al 1993] [Dever et al 1998] [Dever et al 2002] [Doherty et al 2016] [Wilkes et al 1992] [Dong et al 2012] [Dr. Peter Thompson 2024] [Drolen 1992] [Du et al 2011] [Dye 2009] [Edwards and Richards 1989] [Edwards and Richards 1990] [Effect of Working Fluid on Thermal Performance of Closed Loop Pulsating Heat Pipe 2019] [El Achkar et al 2012] [Elam and Lancaster 1972] [Elfarran et al 2021] [Ernst 1979] [Escobar et al 2016] [Experimental Investigations on the Thermal Performance of a Vertical Closed Loop Pulsating Heat Pipe Using Binary Mixture of Fluids 2018] [Fallahzadeh et al 2026] [Farmer et al 1992] [Feher and McCue 1966] [Ferrandi et al 2013] [Finckenor and Carrico 2024] [Finckenor et al 2008] [Fixler 1966] [Fleming 1981] [Fletcher 1972] [Fu et al 2023] [Furukawa 1992] [Gabsi et al 2021] [Gai 2020] [Ganapathi et al 2009] [Mikk 1982] [Ghosh 2016] [Grob and Swanson 2000] [Groll et al 1979] [Grote et al 1987] [Gulpen and Bouchez 1982] [Guo et al 2020] [Guo et al 2023] [Guoliang and Guiqing 2004] [Hallstein 1975] [Hammel and Smith 1974] [Haslett and Mahefkey 1986] [Hatware and Limbadri 2020] [Hegab 2015] [Heltzel et al 2009] [Hemmerdinger 1964] [Hering 1968] [Hillard 1994] [Hodot et al 2014] [Hoke 1965] [Howell 1972] [Huang et al 2026] [Hucek et al 1987] [Humphries et al 1985] [Hyers et al 2012] [In-step Two-phase Flow TPF 1992] [Ishikawa et al 2011] [Jayaram and Gonzalez 2011] [Jebrail and Andrews 1997] [Ji et al 2020] [Johnson, Wesley L. et al 2014] [Jones 1973] [Jorgenson 1967] [Justus et al 2001] [Kamenetzky and Whitaker 1992] [Kammuang-Lue et al 2014] [Karthikeyan et al 2014] [Karthikeyan et al 2014] [Kelliher and Young 1972] [Kerrebrock 1986] [Kerslake et al 1997] [Kihm 2013] [Kim et al 1994] [Kim et al 2019] [King and Curran 1980] [Kizito and Hossain 2015] [Kizito and Hossain 2017] [Kobayashi 1986] [Kotlyarov et al 2020] [Kou et al 2011] [Ku et al 2012] [Ku et al 2012] [Ku and Hoang 2017] [Ku et al 1992] [Ku et al 2004] [Ku et al 2005] [Ku et al 2010] [Kumar et al 2022] [Kuriyama et al 1986] [Kuroi and Nagano 2012] [Kärner and Avaste 1982] [Lee et al 2015] [Lee et al 2020] [Leeper et al 2024] [Lei 2014] [Levin et al 1967] [Lewis and Kenkare 1974] [Li 2024] [Li and Lv 2015] [Li et al 2015] [Li et al 2022] [Li et al 2022] [Li et al 2024] [Li et al 2024] [Li et al 2026] [Liburdy 1985] [Lin et al 2022] [Ling et al 2016] [Ling et al 2024] [Linton 1992] [Liu et al 2014] [Liu et al 2016] [Liu et al 2022] [Liu et al 2025] [Liu et al 2025] [Liu et al 2026] [Lopez and Chapman 1967] [Lu et al 2022] [Lu et al 2024] [Macgregor and Thompson 1970] [Mameli et al 2014] [Marengo et al 2013] [Mark et al 1968] [Markal and Aksoy 2020] [Marshall and Breuch 1968] [Marshburn and McIntosh 1978] [Mason 1988] [Mattick and Hertzberg 1981] [Mattick and Hertzberg 1982] [McKee 1975] [Mehta 2023] [Mehta et al 2020] [Millard and Neel 1965] [Miller and Dever 2011] [Miller et al 2011] [Miller et al 2015] [Milos, Frank S. et al 2012] [Finckenor and Carrico] [Mirkazemi and Ziaei-Rad 2025] [Mishkinis et al 2015] [Motil 2018] [Muraoka et al 2006] [Nagai et al 2014] [Nagano et al 2001] [Nagano et al 2002] [Nagano et al 2005] [Nagano et al 2006] [Nagano et al 2012] [Nam et al 2024] [Nashine et al 2026] [Neel et al 1969] [Nesterov and Dmitriev 2015] [Ninolin et al 2016] [Nishikawara 2017] [Nishikawara and nagano 2017] [Nishikawara et al 2014] [Nomura et al 2025] [Odagiri and Nagano 2019] [Oren and Hixon 1982] [Otterstedt et al 1986] [Ouenzerfi et al 2014] [Owen and Stein 1981] [Pachghare and Mahalle 2013] [Pachghare and Mahalle 2013] [Pachghare and Mahalle 2014] [Parker et al 2004] [Parker et al 2005] [Pastukhov and Maydanik 2018] [Patel and Kumar 2023] [Patel et al 2017] [Pauken and Birur 2004] [Pederson et al 2026] [Peters 1967] [Petete and Ames 1991] [Pradeep and Rama Narasimha 2019] [Prenger and Patterson 1976] [Qiu et al 2026] [Qu et al 2018] [Rankin and Benko 1981] [Riehl 2012] [Riehl 2013] [Riehl and Buschmann 2024] [Saha et al 2014] [Santos et al 2012] [Savage et al 1979] [Schelden and Golden 1973] [Schlitt et al 2010] [Schmidt and Olenick 1967] [Schroeder 1979] [Semple 1968] [Sharma 2005] [Shenming et al 2019] [Sheth et al 2011] [Shrestha et al 2016] [Siedel et al 2014] [Silk and Myre 2013] [Singh and Das 2025] [Singh et al 2014] [Stark 1985] [Stimpson and Hagemeyer 1974] [Stultz 1976] [Sundu and Döner 2020] [Sunil Kumar and Venkateshan 1994] [Suresha and Gupta 1998] [Swanson and Birur 2003] [Swerdling and Alario 1973] [Swerdling and Hembach 1973] [Tagliafico and Fossa 1997] [Tang and Zhu 1989] [Taussig and Mattick 1986] [Teichman et al 1992] [Tharayil et al 2016] [Thermal Design for Satellite Propulsion System by Thermal Analysis 2003] [Thurman 1969] [Tomioka et al 2016] [Torres et al 2012] [Torres et al 2012] [Totani et al 2005] [Tournier and El-Genk 2006] [Tsunoda et al 1992] [Ungar 2008] [Vallerani et al 1979] [Varatharajoo et al 2003] [Veeresha et al 2014] [Veeresha et al 2014] [Venkata Krishnan et al 2018] [Verma et al 2014] [Vlassov et al 2006] [Vlassov et al 2016] [Walburn 1975] [Wan et al 2015] [Wang and Li 2012] [Wang et al 2001] [Wang et al 2013] [Wang et al 2019] [Wang et al 2019] [Wang et al 2021] [Wang et al 2025] [Wang et al 2025] [Watanabe et al 2020] [Johnson] [Wilkes and Hummer 1991] [Wilkes et al 1991] [Wilkes et al 1991] [Thermal Systems Engineering for] [Williams and Palo 2006] [Williamson 1987] [Wing 1983] [Wise 1986] [Wolf 1992] [Woollam et al 2000] [Wu et al 2014] [Wu et al 2014] [Wu et al 2023] [Xia et al 2023] [Xiahou et al 2021] [Xiao et al 2023] [Xiayu et al 2026] [Xie et al 2022] [Xie et al 2024] [Xie et al 2024] [Xiong et al 2024] [Xu et al 2017] [Xu et al 2021] [Xue et al 2014] [Yang et al 2021] [Yang et al 2022] [Yin and Liu 2010] [Youngquist et al 2018] [Yun, James Seokgeun et al 1993] [Yushakova et al 2012] [Zhang et al 2013] [Zhang et al 2020] [Zhang et al 2023] [Zhang et al 2024] [Zhao et al 2021] [Zhou et al 2013] [Zhulev and Potapov 1968]

Space surveillance, tracking and orbit determination

How the orbit became public. Space surveillance, optical and radar tracking, orbit determination and prediction, and manoeuvre detection. 53 of these titles name optical, visual, photographic or telescopic observation, and 23 name the detection of a manoeuvre, the capability on which the public record of this vehicle’s orbits depends.

338 records. [Al-Hourani 2024] [Al-Hourani and Manzoor 2026] [AlDahoul et al 2022] [Durkin et al] [Mashiku et al] [Mashiku] [Andress 1999] [Andress 1999] [Annett and Dennis 2018] [Ardaens and Gaias 2018] [Ardaens and Gaias 2019] [Argentiero et al 1979] [Army War Coll Carlisle Barracks Pa 1961] [Bai et al 2019] [Baranova et al 2024] [Barbano 2022] [Barlier 2005] [Bell 1964] [Benedict 1963] [Biria and Marchand 2014] [Borowitz 2019] [Borowitz 2022] [Boumeftah and Kurt 2025] [Braga-Illa 1969] [Braun et al 2019] [Brescia et al 1964] [Bryant and Edwards 1973] [Byun 2003] [Cabrera et al 2019] [Campbell et al 2018] [Cano et al 2023] [Cascioli and Genova 2021] [Chen et al 2017] [Chen et al 2025] [Chesley 1964] [Chiaradia et al 1997] [Chiaradia et al 2003] [Christian 2023] [Ciarravano 2021] [Cipollone et al 2025] [Clark and Lee 2020] [Cleeton 1960] [Coder and Holzinger 2016] [Cot 1993] [Counselman and Abbot 1989] [Cretaux et al 1994] [Crombie 1989] [Cui et al 2024] [Culp and Jin 1987] [Das and Bhattacharya 2021] [DeBay and Richard 1963] [DeCoster et al 2026] [Deker 1971] [Delande et al 2018] [Denham 1965] [Dewald 1998] [Diersing 1986] [Ding et al 2025] [Doll et al 1994] [Doll et al 1993] [Downs et al 1974] [Downs et al 1974] [Duke 1960] [Elango et al 1984] [Evans and Carr 1989] [Eves 2019] [Fadin et al 2019] [Fan et al 2022] [Fang 1979] [Feipeng et al 2001] [Filho et al 2023] [Freed 1977] [Freund 1967] [Frisbee 2015] [Gill and Akos 2024] [Givri 1998] [Gong et al 2016] [Gordon and Falco 2025] [Graham and Vigneron 1981] [Grigg et al 2022] [Gronchi 2009] [Guo et al 2015] [Guo et al 2025] [Haith and Bowman 2014] [Hajiyev and Ata 2011] [Hall and Jefferies 2022] [Han et al 2026] [Harris et al 1959] [Hauser 1981] [He et al 2024] [He Miao-fu 1984] [Hejduk and Frigm 2015] [Herriott 1958] [Hilton et al 2019] [Hoffmann et al 1960] [Holzinger 2014] [Hong et al 2026] [Hu et al 2019] [Hu et al 2020] [Huang et al 1990] [Huang et al 2012] [Huang et al 2016] [Huang et al 2022] [Huang et al 2023] [Hwang 2011] [Hwang et al 2008] [Hwang et al 2026] [Hynek et al 1959] [Ialongo 1969] [Jackson et al 2021] [Jefferies 2006] [Jianqi et al 2003] [Johnston and Smith 1964] [Kahl Kristensen 1995] [Kaiser 2015] [Kansara et al 2026] [Karimi and Mortari 2010] [Karunathilake et al 2026] [Kaufman and Weaver 1963] [Kawase and Tanaka 1979] [Kazemi et al 2024] [Kelecy and Jah 2010] [Kiani and Pourtakdoust 2015] [Kim 2025] [Kim et al 2012] [Klimburg-Witjes et al 2025] [Ksendzuk et al 2018] [Kuang et al 1996] [Kuijper et al 1995] [Kuriyama et al 2026] [Kurtz and Speer 1960] [Kutay et al 2001] [Labrèche and Mladenov 2023] [Larson et al 1991] [Lee 2005] [Lee et al 2004] [Lemmens and Krag 2014] [Li and Chen 2019] [Li et al 2018] [Li et al 2018] [Li et al 2024] [Li et al 2025] [Linlin and SUN Huixian 2003] [Lian-da and Jia Pei-zhang 1994] [Lin et al 2024] [Lin et al 2025] [Lind 2020] [Liu and Liu 2001] [Liu et al 2025] [Liu et al 2026] [Liu et al 2026] [Liu et al 2026] [Liu Haiying and Wang Huinan 2005] [Lu et al 2020] [Lubowe 1966] [Lupo et al 2018] [Lv et al 2025] [Ma 2005] [Ma and Zhai 2004] [Mao and Chen 2025] [Markov et al 2014] [Marshall and Luthcke 1994] [Masevich and Lozinskii 1958] [Massevitch and Losinsky 1970] [Matouš and Moravec 2026] [McCormick 2015] [McCUE 1963] [McCue et al 1971] [Mercer 1964] [Mercer 1965] [Miao et al 2023] [Mikhailov and Vasil’ev 2011] [Milani et al 2011] [Milani et al 2012] [Miller 2007] [Minka et al 1966] [Montilla et al 2024] [Morduch and Bergeron 1978] [Myers and Tapley 1975] [Naka et al 1997] [Naka et al 1997] [Nakamura et al 2007] [Naval Research Lab Washington Dc 1958] [Naval Research Lab Washington Dc 1960] [Naval Research Lab Washington Dc 1962] [Nelson 1963] [Neta 1998] [Newton 1963] [Norris 1974] [Oltrogge and Alfano 2019] [Optical methods of observation 1961] [Otani and Kohtake 2019] [Pachura et al 2014] [Pan and Zhou 2009] [Papanikolaou 2023] [Passive Ground-Based Electro-Optical Detection 1979] [Patton 1960] [Pearlman et al 2010] [Peldszus 2018] [Pelton 2019] [Peng and Bai 2018] [Peng and Bai 2018] [Peng and Bai 2018] [Peng and Bai 2019] [Peng and Bai 2019] [Peng and Bai 2019] [Peng and Wu 2009] [Philco Newport Beach Ca Aeronutronic Div 1962] [Phipps et al 1993] [Piatrou and Rigaut 2017] [Pilkington 1966] [Pilkington 1967] [Polkowska 2020] [Polkowska 2021] [Preski 1968] [Program moonbeam for amateur 1957] [Psiaki 2002] [Qiao et al 2026] [Qile et al 2006] [Qin et al 2019] [Radley and Eubanks 2020] [Rao and Sinha 1985] [Raol and Sinha 1985] [Richards 1960] [Richards 1961] [Richards 1973] [Roberts 2004] [Robinson and Frueh 2025] [Rork et al 1982] [Rosseland 1964] [Rudenko 1997] [Sabol 1998] [Sabol and Culp 2001] [Sabol et al 2007] [Sang and Bennett 2014] [Satterthwaite 2000] [Schafer and Marson 2021] [Schmidt et al 2025] [Schrama 2018] [Schwan 1994] [Schwan 1995] [Schwartz 1981] [Schwintzer et al 1995] [Sciré et al 2015] [Scorsoglio et al 2026] [Scott and Ellery 2015] [Scott and Ellery 2016] [Luthcke et al 2003] [Seidelmann et al 2007] [Seidelmann et al 2010] [Seong and Kim 2013] [Setty et al 2016] [Shaffer and Andrews 1988] [Shaolin 2017] [Shi et al 2026] [Shklovskii 1961] [Shum et al 1994] [Siew and Linares 2022] [Smith 1988] [Song-jie et al 2003] [Sorvari 1979] [Spencer and Williams 2013] [Stone et al 1994] [Su and Dong 2012] [Subramanian et al 2004] [Sukhov et al 2022] [Surdi 2020] [Suthakar et al 2025] [Thomas et al 2021] [Taff 1979] [Taff 1979] [Taff 1979] [Taff 1983] [Taff and Sorvari 1979] [Taff et al 1984] [Tagawa et al 2016] [Takano and Marchand 2014] [Takeuchi 2019] [Tanaka 2017] [Tapley 1975] [Tapley et al 1985] [Tarzi et al 2015] [Thompson and Griggs 2026] [Tian et al 2025] [Toda and Schlee 1967] [Townsend 1966] [Townsend 1966] [Trw Space Technology Labs Redondo Beach Ca 1964] [Tseng 2021] [Tsukamoto et al 2015] [van den IJssel and Visser 2005] [Veis 1963] [Verspieren 2021] [Vigue et al 1994] [Visser and Ambrosius 1997] [Vonbun et al 1978] [Voss et al 2013] [Wakker and Ambrosius 1985] [Wang and Gao 2016] [Wang et al 2021] [Wardrop 1979] [Warner and Lemm 2014] [Wei and Nener 2019] [Weinberg 1980] [Weixing et al 2011] [Whipple 1958] [Whipple and Hynek] [Whipple and Hynek 1958] [Woods et al 2013] [Xiao et al 2011] [Xie et al 2025] [Xu et al 2011] [Xu et al 2026] [Yan et al 2026] [Yang and Wen 2004] [Yang et al 2024] [Yang et al 2025] [Yates et al 2012] [Yin et al 2023] [Yin et al 2026] [Yong and Shen 1972] [Yonglong et al 2025] [Yunpeng et al 2021] [Zhai et al 2022] [Zhang et al 2008] [Zhang et al 2024] [Zhang et al 2024] [Zhang et al 2025] [Zhang et al 2026] [Zhao et al 2023] [Zhao et al 2024] [Zhong et al 2025] [Zhou et al 2026] [Zhu et al 2020] [Zhu et al 2026] [Zieliński and Butkiewicz 1985] [Zollo and Weigel 2024] [Zondek 1979]

Payload deployment, experiments and power beaming

The payload bay and its one described experiment. Payload deployment, flight experiments and space-based power beaming. 258 of these 295 titles name space solar power, a solar power satellite or the beaming of power, and one of them is a thermal analysis of the photovoltaic radio-frequency antenna module that the programme flew.

295 records. [Adaptive In-Orbit Servicing of Altered Satellite Components, Adaptive gripper placement on altered components for servicing in-orbit satellites 2025] [Addanki] [Ahmad 2026] [Albertine et al 1997] [Alizadeh and Zhu 2024] [Ambatali and Nakasuka 2024] [Andryczyk et al 1979] [Apa et al 2026] [Arndt and Leopold] [Asri and Zhu 2024] [Au et al 2022] [Bamberger and Coomes 1992] [Bamberger et al 1991] [Baraskar 2024] [Barbee et al 2010] [Barnhard 2017] [Barnhard 2024] [Barnhard and Faber 2016] [Barnhard and Potter 2018] [Barres 2006] [Barry 2024] [Barry 2025] [Baryshnikov 1995] [Baryshnikov et al 1995] [Baycan et al 2025] [Benford and Dickinson 1995] [Bennett 1995] [Bennett 1995] [Bennett 1997] [Bennett 1997] [Bennett et al 1994] [Blackwell 2005] [Broome et al 1968] [Brown] [Brown] [Brown 1972] [Brown 1973] [Brown 1985] [Brown 1989] [Brown and Kim 1974] [Buchanan et al 2025] [Burke 1992] [Burke et al 1994] [Hyland 2025] [Cable 2007] [Campbell and Taylor 1998] [Campbell et al 2024] [Carlson 2023] [Carrington et al 2000] [Carrington et al 2004] [Carrio and Cichan 2025] [Cheng et al 2025] [Chobotov 1977] [Choi et al 1991] [Choi et al 2024] [Collins and Matsuoka 2008] [Components and Subsystems for 2024] [Components and Subsystems for 2024] [Crisp et al 2015] [Cummings 2004] [Cunningham and Ho 2026] [Daddu 2026] [Dagle 1991] [Dagle 1991] [Dankanich et al 2015] [Davis 1977] [Dessert 2013] [Dietrich and Laino 2024] [Dietrich and Wan 2024] [Dietz 1980] [Dong et al 2020] [Dong et al 2026] [Dowell et al 1995] [Dremann et al 2025] [Dudenhoefer and George 2000] [Early 2003] [Eastlund and Jenkins] [Edler 1978] [Elias and Kimel 1995] [Fafard and Masson 2026] [Falkner 1984] [Fan et al 2021] [Fan et al 2024] [Finnell 1980] [Finnell 1981] [Fleming et al 2024] [Fleming et al 2024] [Flournoy 2012] [Flournoy 2012] [Fork 2001] [Fork et al 2003] [Fraas et al 2024] [Franceschetti et al 2012] [Friedman 1993] [Friedman 1994] [Friedman et al 1994] [Fugate 1994] [Glaser 1969] [Glaser 1973] [Glaser 1975] [Glaser 1975] [Glaser 1992] [Glaser 1992] [Glaser 1992] [Golap Kanti Dey and Ahmmed 2014] [Gort et al 2025] [Goubau 1970] [Graham and Kingston 2015] [Gregorwich] [Gutmann and Gworek 1979] [Hahn et al 2003] [Hardaway et al 2026] [Hashimoto 2011] [Hashimoto and Matsumoto] [Hatsuda et al 2002] [Henley et al 2002] [Hoffert et al 1989] [Hoheisel et al 2026] [Hou 2025] [Hou 2025] [Hou 2025] [Hou 2025] [Hou et al 2025] [Hou et al 2025] [Huang et al 2025] [Hudson and Kolosa 2020] [Ishikawa et al 2013] [Jain and Landis 1992] [Jain and Landis 1994] [Jain and Landis 1995] [Jamnejad and Silva 2008] [Jawdat et al 2017] [Jones 1979] [Juroshek 1981] [Makinde 2014] [Kare 2005] [Kare 2006] [Kare et al 1999] [Kawai et al 2024] [Kawasaki et al 1999] [Kaya 1995] [Kaya and Matsumoto 1981] [Khvostikov et al 2015] [Kim et al 1998] [Koert and Cha 1992] [Koert and Lallement 1989] [Koga et al 2024] [Komerath and Komerath 2011] [Komerath et al 2006] [Koroleva et al 2023] [Krupke 2004] [Kumar 2001] [Kumar 2002] [Kuriki and Yamashita 1988] [Lafleur and Saleh 2008] [Lafleur and Saleh 2009] [Landis 1991] [Landis 1993] [Landis 1993] [Landis and Jain 1992] [Landis and Westerlund 1992] [Landry et al 1990] [Laying the Foundation for 2001] [Le] [Lee 2003] [Levin et al 1990] [Liang et al 2012] [Liang et al 2024] [Lin 2002] [Lipinski and Walter 1995] [Lipinski et al 1994] [Liu et al 2022] [Luce 2003] [Ma et al 2026] [Machina et al 1992] [MacNeal and Jewett 1994] [Mahin and Mahbub 2024] [Maillot et al 2024] [Maki et al 2012] [Maldonado-Romo et al 2026] [Mankins 1995] [Mankins 2024] [Mason 1999] [Matsumoto] [Matsumoto 2002] [McSpadden and Mankins 2002] [Michael and Pakhomov 2008] [Microwave Power Transmission from 2019] [Mifsud 2022] [Mills 1971] [Monroe 1994] [Muller and Travish 2004] [Myrabo 2006] [Myrabo and Pakhomov 2008] [Myrabo and Dickenson 2005] [Narita et al 2011] [Neal et al 1994] [Nelson 2023] [New Candidate Lasers for 1978] [Ni et al 2025] [Nugent 2024] [Nugent et al 2025] [Nugent et al 2025] [Nugent et al 2026] [Nugent et al 2026] [O’Flaherty et al 2024] [O’Leary 1982] [O’Neill 2021] [Oleson 1999] [Olsen et al 1991] [Omran and Bazzocchi 2024] [Osepchuk 1996] [Ott and Rice 1981] [Overview wireless power transmission 2023] [Parameswaran and Pathan 2017] [Pasupuleti 2025] [Patha and Woodcock 1974] [Peters et al 2026] [Petra and Miley 1998] [Petra et al] [Petra et al 1994] [Phased array technique for 2023] [Ponikvar 1992] [Ponikvar et al 1994] [Potter 1992] [Power Beaming Applications 2024] [Power-Beaming Technology for Laser 1984] [Prasetiyo 2026] [Preble 2000] [Qaid et al 2025] [Rajesh and Singh 2018] [Rana and Berthoud 2025] [Rather 1989] [Rather 1992] [Rather 1992] [Rather 2003] [Rathod et al 2023] [Raza et al 2018] [Repetti 1991] [Retro-reflective beamforming technique for 2023] [Rizzo et al 2019] [Robinson 1970] [Rodenbeck and Chang 2005] [Rodenbeck et al] [Rotary, deployable space solar 1965] [Rubenchik et al 2009] [Rybus 2024] [Safaei et al 2025] [Sanders and Kang 2020] [Sanders and Kang 2022] [Sasaki and Tanaka 2011] [Sasaki et al 2013] [Sato et al 2015] [Sato et al 2017] [Schroeder and Petroff 1980] [Schäfer and Gray 2012] [Shan and Qi 2015] [Shelef and Pakhomov 2008] [Shigehara and Ohtaka 1996] [Shinohara 2009] [Shinohara 2010] [Shinohara 2022] [Shinohara and Kawasaki 2009] [Smith et al 2012] [Smitherman 2013] [Somov et al 2025] [Spencer et al 2012] [Summers et al 2025] [Takano 2019] [Tan 2011] [Tanaka 2018] [Tanaka et al 2011] [Tanaka et al 2012] [Tanaka et al 2012] [Theoretical principles and practical 2023] [Turek 2010] [Walker et al 1991] [Wang et al 2014] [Wang et al 2022] [Wang et al 2024] [Wei et al 2026] [Weng et al 2025] [Winsor and Jaffe 2025] [Woodcock 1980] [Wu et al 2018] [Xu et al 2024] [Xue et al 2025] [Yadav et al 2022] [Yasaka 1992] [Yin et al 2026] [Yin et al 2026] [Yoshida et al 2015] [Yugami et al 1996] [Zeiders 1994] [Zhang et al 2024]

Entry trajectory, guidance and control

The crossrange and the entry. Entry trajectories, equilibrium glide, bank modulation, predictor-corrector and optimal entry guidance, and entry flight control.

289 records. [227 A re-entry capsule control system design for microgravity experiments 1994] [Aboudan et al 2008] [Alexander 1978] [Approximate analysis of atmosphere re-entry trajectories II 1965] [Aprovitola et al 2021] [Archer and Sworder 1979] [Ashikhmina and Prosuntsov 2021] [Bae et al 2024] [Baek et al 2008] [Balint et al 2010] [Bayle 1984] [Bazhenov et al 2016] [Bell 1965] [Benjamin Margolis et al 2021] [Bharadwaj et al 1998] [Bojun et al 2019] [Broglio 1961] [Brunner and Lu 2008] [Bryson and Denham 1962] [Byczkowski and Rao 2026] [Calhoun, Philip 2000] [Cassanto 1966] [Chai et al 2020] [Chander and Krishna 2013] [Chao et al 2010] [Chao et al 2015] [Chao et al 2022] [Chapman, Dean R. 1960] [Chawla et al 2010] [Chen et al 2018] [Chen et al 2019] [Chern, J. S. and Vinh, N. X. 1978] [Chou et al 1998] [Clark and Braun 2008] [Cooper 1968] [Craig and Gonzalez 1973] [Căruntu et al 2008] [Dai et al 2026] [Danesi 1982] [Das et al 2023] [Das et al 2024] [Delpino, F. H. et al 1967] [Deng et al 2024] [Deyst 1968] [Dieriam, Todd A. 1990] [Divitiis and Vitale 2010] [Divya and Jayashree 2023] [Dong and Cai 2017] [Du et al 2015] [Duan and Li 2015] [East 1999] [Elsey and Carlson 1968] [Etkin 1961] [Evdokimov et al 2012] [Fawley and Putnam 2021] [Finke 1990] [Flight module and Venus entry vehicle 2017] [Fogarty 1967] [Fong et al 1970] [Foster 1960] [Fujino et al 2008] [Gao et al 2019] [Gaohua et al 2014] [Garcia-Llama 2011] [Giraldo-Grueso et al 2026] [Gong et al 2025] [Goto et al 2004] [Greene and Williamson 1982] [Guo et al 2018] [Gupta and Hall 1979] [Guruswamy 2016] [Haig and Perlmutter 1965] [Hanson, John M. and Jones, Robert E. 2003] [Hanson, John M. and Jones, Robert E. 2004] [Harpold and Gavert 1983] [Havey 1982] [He et al 2017] [Henry 1989] [Hsu et al 1990] [Hu et al 2016] [Huang et al 2024] [Huo et al 2014] [Ishimoto 2000] [Jackson 1961] [Jeong et al 2009] [Jiang and Li 2019] [Johnson et al 1982] [Johnson, Breanna 2019] [Joint Conference on Lifting 1960] [Josselyn and Ross 2003] [Jouhaud et al 2007] [Kadam and Hablani 2014] [Karl and Weiland 1993] [Karlgaard 2025] [Kaslik and Balint 2007] [Kelley and Sullivan 1973] [Kelley et al 1982] [Khalil et al 2023] [Kim et al 2021] [Kirsch 1973] [Klafin and Barnhart 1973] [Klimin and Yaroshevski 1970] [Kornreich 1963] [Kovtunenko et al 1986] [Krischke et al 1995] [Leavitt and Mease 2007] [Lee 2006] [Lee and Cho 2002] [Lee and Cho 2006] [Lee and Lee 2023] [Lee et al 2004] [Lessing et al 1964] [Levinsky 1962] [Li and Peng 2011] [Li et al 2022] [Liang and Ren 2018] [Liang et al 2020] [Liu et al 2015] [Liu et al 2018] [Liu et al 2020] [Liu et al 2022] [Liu et al 2023] [Loh 1962] [Lu 1997] [Lu 2006] [Lu 2008] [Lu 2014] [Lu et al 2017] [Lu, Ping 1999] [Lu, Ping and Shen, Zuojun 2003] [Luo et al 2014] [Lv et al 2023] [Lykoudis 1964] [Ma et al 2018] [Ma et al 2022] [Mandell 1962] [Mao et al 2016] [Marcos et al 2010] [Martikan 1965] [Martin 1989] [Mathavaraj and Padhi 2020] [Maurer and Hall 1988] [McNamara and Braun 2014] [Mease et al 2002] [Miyazawa et al 1999] [Moe 1960] [Moote, J. D. 1970] [Morani et al 2011] [Morio et al 2009] [Morth 1970] [Morth and Speyer 1961] [Murphy and Bradley 1975] [Nikolaev et al 1976] [Ning et al 2007] [Norman and Meier 1963] [Nosratollahi et al 2010] [Ohya and Kato 1985] [Otey and English 1977] [Paine 1967] [Palumbo et al 2017] [Paolozzi 2004] [Pei et al 2021] [Pesch 1980] [Platus 1967] [Platus 1967] [Platus 1976] [Platus 1979] [Platus 1980] [Platus 1980] [Platus 1981] [Platus 1982] [Plender 1964] [Plumb 1971] [Poustini et al 2022] [Ramasamy et al 2014] [Randall 1970] [Rataczak et al 2025] [Rea, Jeremy R. and Putnam, Zachary R. 2007] [Ren et al 2017] [Ridderhof et al 2022] [Windhorst 1996] [Roenneke and Cornwell 1993] [Ruger 1964] [Rugescu 2013] [Sara Babu T 2014] [Sarkar et al 2021] [Shao and Wang 2015] [Shao and Wang 2016] [Shao et al 2015] [Shapland et al 1965] [Shen and Lu 2005] [Shen, Zuojun et al 2002] [Shi et al 1971] [Shi et al 2017] [Shi et al 2020] [Shi et al 2025] [Shou et al 2021] [Shou et al 2022] [Simons 1975] [Sonandres et al 2026] [Stalony-Dobrzanski 1967] [Stern and Chu 1963] [Stern and Chu 1964] [Stiles 1970] [Stone, H. W. and Powell, R. W. 1984] [Stone and Powell 1985] [Su and Liu 2025] [Su and Liu 2025] [Su et al 2021] [Su et al 2021] [Su et al 2024] [Sun and Zhang 2020] [Sun et al 2020] [Sun et al 2025] [Sushnigdha and Joshi 2018] [Swei, Sean 2014] [Tang et al 2025] [Tava and Suzuki 2002] [Theobald 1966] [Thomas and Perlbachs 1967] [West and Johnston] [Tian et al 2015] [Tian et al 2015] [Tigges, Michael et al 2006] [Tillier, Clemens Emmanuel 1998] [Tormo and Serghides 2007] [Townend 1979] [Townend 1999] [Trajectory Optimization and the Control of a Re-entry Vehicle during TAEM Phase using Artificial Neural Network 2009] [V. A. Yaroshevskii Approximate 1965] [Vinh and Dobrzelecki 1971] [Vinh, N. X. et al 1980] [Wagner 1965] [Wallner and Well 2003] [Wang 1963] [Wang 1963] [Wang 1965] [Wang and Grant 2018] [Wang and Ting 1961] [Wang et al 2009] [Wang et al 2013] [Wang et al 2015] [Wang et al 2022] [Wang et al 2023] [Wang et al 2025] [Wang et al 2026] [Wang et al 2026] [Warga and Hailey 1964] [Wei et al 2018] [Wen et al 2023] [Weston 1966] [Williamson 1979] [Windhorst et al 1998] [Wu et al 2012] [Wu et al 2018] [Wu et al 2021] [Wurster 1983] [Xia et al 2015] [Xingling and Honglun 2014] [Xu et al 2023] [Yang and Sun 2011] [Yang and Wang 2012] [Yang and Wang 2015] [Yang et al 2017] [Yaroshevskii 2008] [Yeo and Sng 1980] [Yin et al 2025] [Youssef, Hussein et al 2001] [Yu et al 2018] [Yu et al 2019] [Yu et al 2019] [Yu et al 2026] [Yu Li and Nai-gang Cui 2008] [Zagalsky et al 1971] [Zhai et al 2019] [Zhang and Tang 2008] [Zhang et al 2018] [Zhang et al 2021] [Zhang et al 2022] [Zhang et al 2025] [Zhang et al 2025] [Zhao and Zhou 2013] [Zhao et al 2012] [Zhao et al 2014] [Zhi et al 2015] [Zhou and Wang 1987] [Zhou et al 2020] [Zimmerman et al 2002] [Zou et al 2015]

Spacecraft batteries, cycle life and degradation

The endurance relation. Secondary cells for spacecraft and their cycle life against depth of discharge, with the electric vehicle and grid storage literature on capacity fade and state of health that now dominates the subject. 59 of these 260 titles name a satellite, a spacecraft, an orbit or space, so the spacecraft case is the minority of the literature on the relation the endurance argument inverts.

260 records. [A.L.Bader et al 2014] [Abe et al 2019] [Alharbi et al 2025] [Allison 2018] [Andrenacci et al 2024] [Anguchamy and Popov 2010] [Badcock and Haag 1988] [Badcock and Milden 1985] [Bao et al 2022] [Beauchamp and Sindorf 1988] [Belmajdoub et al 2024] [Berecibar et al 2016] [Bhattacharya et al 2017] [Boggan and Clarke 2026] [Bonfitto 2020] [Bosch and Diller 2024] [Brewer et al 1990] [Brewer et al 1989] [Brown et al 2008] [Bruess 1965] [Budiman et al 2026] [Bustos et al 2024] [Candan Kadem and Kadem 2026] [Capacitor Superior to Nickel-Hydrogen Battery 2004] [Cataldo 1986] [Cataldo 1984] [Chaba et al 2021] [Chen et al 2013] [Chen et al 2022] [Chen et al 2023] [Choi 2020] [Choi et al 2022] [Cipin et al 2021] [Coates and Fox 1996] [Coates et al 1994] [Coates et al 1997] [Cohen and Dalton 1996] [Connor et al 2023] [Cook et al 2020] [Cook et al 2021] [Bomberger and Moose 1963] [Dalton et al 2016] [Dalton et al 2017] [Dalton et al 2017] [Dalton et al 2018] [Data-Driven Estimation of Lithium-Ion Battery State-of-Health Prediction Approach Using Machine Learning Algorithm for Enhanced Battery Management Systems 2024] [di Crescenzio 2019] [Dong and Wei 2021] [Du et al 2026] [Duggal and Venkatesh 2015] [Dunlop and Stockel 1982] [Extended life nickel-hydrogen storage cell 1989] [Ezemobi et al 2021] [Fan et al 2023] [Fogelquist and Lin 2023] [Garse et al 2025] [Gong et al 2022] [Gross 1984] [Hafen 1982] [Han and Geng 2023] [Hashemi et al 2021] [Hayashi et al 2013] [He and Chen 2026] [Hendricks et al 2022] [High cycle life, high rate nickel-zinc batteries 1980] [Hiroyuki et al 1997] [Hollandsworth et al 2002] [Hoover, S. A. et al 1997] [Hou et al 2021] [Hou et al 2021] [Hou et al 2022] [House and Hill 1993] [Hu et al 2016] [Hu et al 2024] [Ingling and Koesters 1967] [Isaacson and Spotnitz 2012] [Jang and Yang 2021] [Jiang et al 2022] [Jorkesh et al 2025] [Jun et al 2020] [Jung et al 2021] [Kaiya and Ookawa 1995] [Karkadakattil 2026] [Ke et al 2026] [Khaleghi Rahimian et al 2012] [Kim and Jung 2025] [Kim and Shin 2023] [Kim et al 1994] [Kim et al 1994] [Kim et al 2024] [Kim et al 2026] [Kobayashi et al 2016] [Koehler et al 1984] [Kulin 1997] [Kumar et al 2010] [Lackner and McCoy 1986] [Lami et al 2019] [Lee et al 2020] [Lei and Yu 2026] [Li 2020] [Li et al 2020] [Li et al 2022] [Li et al 2023] [Li et al 2024] [Li et al 2024] [Li et al 2025] [Life Cycle Identification of Internal Short Circuits of Lithium-ion Battery Based on Recursive Least Square Method 2022] [Lim and Verzwyvelt 1988] [Lim and Verzwyvelt 1990] [Lim and Verzwyvelt 1984] [Lim and Verzwyvelt 1988] [Lim and Verzwyvelt 1987] [Lin et al 2017] [Lithium-ion Battery State of Health Estimation Based on Real-world Driving Data 2023] [Liu et al 2013] [Liu et al 2018] [Liu et al 2019] [Liu et al 2023] [Liu et al 2025] [Luke and Roeger 1965] [Luke and Roeger 1965] [Lyu et al 2019] [Lyu et al 2022] [Lyu et al 2025] [Mains 1966] [Makki et al 2023] [Maskell and Metcalfe 1992] [McDermott 1986] [Megahed and El-Dib 2007] [Menshikov 2022] [Miller 1987] [Miller et al 1990] [Mita et al 2012] [Mukoyama et al 2016] [Muthukrishnan and Ramesh Kumar 2024] [Sai Vinay Kishore and Vanjari 2026] [Naylor Marlow et al 2024] [Neupert and Kowal 2023] [Nickel-hydrogen bipolar battery 1986] [Nohra et al 2026] [Nuttall et al 1965] [Hadi and Fujita 2017] [Okita 2026] [Osara and Bryant 2019] [Otzinger 1991] [Ozkurt et al 2016] [Palanisamy et al 2020] [Palanisamy et al 2020] [Pandit and Ahlawat 2025] [Park and Yun 2025] [Park et al 2018] [Patel and Liang 2015] [Pavlov 1997] [Ping et al 2023] [Potter et al 2006] [Qin 2009] [Qin and Zhao 2024] [Qin and Zhao 2025] [Qiu and Rajashekara 2026] [Rahman and Alharbi 2024] [Rao 1999] [Rashitov et al 2023] [Reid, Concha 2004] [Reid et al 2004] [Ren et al 2025] [Review on Techniques for Power Battery State of Health Estimation Driven by Big Data Methods 2023] [Rodriguez et al 1983] [Hemavathi 2025] [Kumarappa and Manjunatha H M 2024] [Sagare et al 2023] [Sakai et al 1990] [Schmitt et al 2023] [Shi et al 2025] [Shin et al 2026] [Sizemore and Stroup 1965] [Smithrick, John J. and Hall, Stephen W. 1990] [Smithrick and Hall 1991] [Smithrick and Hall 1992] [Sohail et al 2026] [Somakettarin and Pichetjamroen 2019] [Sone et al 2003] [Song et al 2017] [Song et al 2019] [Sordi et al 2023] [Sparks 1980] [State of Health Estimation of Lithium-ion Battery Based on Feature Optimization and Random Forest Algorithm 2024] [Rickman] [Stock et al 2024] [Stockel et al 1980] [Sudarshan et al 2025] [Sun et al 2014] [Sun et al 2022] [Sun et al 2025] [Surya et al 2021] [Tam and Wainright 2006] [Tam and Wainright 2007] [Tan et al 2021] [Tanaka et al 2017] [Tang et al 2017] [Tekin and Karamangil 2024] [Thermal design and recharging of satellite batteries 1962] [Thermal Simulation Analysis of a Lithium-Ion Battery 2021] [Tian and Lian 2010] [Uddin et al 2016] [Ungurean et al 2016] [Uzun 2025] [Vaidyanathan et al 1996] [Vashisht et al 2023] [Vashisht et al 2023] [Vidal et al 2020] [Walker 2019] [Wang and Chen 2024] [Wang and Du 2022] [Wang and Wang 2025] [Wang et al 2005] [Wang et al 2005] [Wang et al 2006] [Wang et al 2018] [Wang et al 2023] [Wei et al 2018] [Wessells et al 2011] [Wofenstine et al 2002] [Wu et al 2022] [Wu et al 2023] [Wu et al 2025] [Xia and Qahouq 2021] [Xie 2017] [Xiong et al 2023] [Xu and Li 2025] [Xu et al 2016] [Xue et al 2022] [Yang and Ling 2026] [Yang and Yang 2025] [Yang et al 2018] [Yang et al 2019] [Yang et al 2022] [Yang et al 2024] [Yang et al 2025] [Yao and Chen 2025] [Ye et al 2025] [Yogesh Anil and Bhargava 2024] [Yu et al 2022] [Yun and Kong 2022] [Zagrodnik and Jones 1992] [Zhang et al 2013] [Zhang et al 2016] [Zhang et al 2022] [Zhang et al 2023] [Zhao 2025] [Zhao et al 2024] [Zhou and Mishra 2016] [Zhou et al 2024] [Zhou et al 2025] [Zhou et al 2025] [Zhou et al 2026] [Zhu et al 2025] [Zonghai 2018] [Zou et al 2026] [Zuluaga et al 2023] [Şahi̇n et al 2021]

Entry aerothermodynamics, stagnation heating and the plasma sheath

The heating bound beneath the entry. Stagnation-point and convective heating of blunt bodies, real-gas and radiative heating, and the ionised sheath that interrupts communication.

216 records. [Adams 1969] [Agranat et al 1979] [Anderson 1968] [Anfimov 1966] [Appar et al 2022] [Arrington, J. P. and Woods, W. C. 1972] [Atchison et al 2025] [Avduevskii and Ivanov 1968] [Bansal et al 2011] [Barone et al 2022] [Beck et al 2021] [Beck, R. A. et al 2019] [Belousov and Golovachev 1990] [Bian et al 2026] [Biberman et al 1978] [Bloor 1968] [Boison 1959] [Bulmer 1975] [Chae et al 2019] [Chow 1963] [Chrusciel 1975] [Coelho and Lino da Silva 2023] [Cooper and Martin 2023] [Crowell and McNamara 2012] [Dai et al 2026] [Davies et al 1984] [Davis and Flügge-Lotz 1964] [De Jarnette 1989] [Desautel, D. 1984] [Dharmesh et al 2023] [Di Renzo et al 2020] [Dicristina 1979] [Dix et al 1967] [Doihara and Nishida 2002] [Druguet 2010] [Ecker et al 2024] [Edquist et al 2023] [Eremeitsev and Pilyugin 1981] [Estruch-Samper 2016] [Fante et al 1970] [Fay and Riddell 1958] [Feng et al 2014] [Fey et al 1993] [Finson 1975] [Finson et al 1980] [Florence 1981] [Forsyth et al 2024] [Forsythe et al 1961] [Franciamore and Tumuklu 2026] [Frankenthal 1964] [Franze and Barz 2025] [Gershbein and Kolesnikov 1980] [Gokcen et al 1998] [Gokul and Malaikannan 2025] [Golden 1969] [Golovachev 1972] [Golovachov and Lunkin 1979] [Guo et al 2017] [Guo et al 2019] [Gülhan et al 2001] [Gülhan et al 2019] [Gülhan et al 2021] [Hackett, Charles M. 1993] [Hankey and Hooks 1963] [Harthun et al 1983] [Hartung et al 1992] [Harvey, Gale A. 2008] [Hassan et al 1993] [Hayes and Rotman 1973] [He et al 2023] [He et al 2026] [Heller 1969] [Heller and Widnall 1968] [Helms 1973] [Hollis and Perkins 1999] [Hollis, Brian R. 2010] [Hollis and Hollingsworth 2014] [Horing et al 2025] [Horton and Babineaux 1967] [Hove and Shih 1977] [Huang et al 2022] [Huo and Yang 2015] [Irimpan and Menezes 2018] [Ivanov 1967] [Jischke 1970] [Kachadourian 1970] [Kaiser and Fluegge-Lotz 1968] [Kao 1964] [Kao 1964] [Karl et al 2015] [Keith Soo Hoo et al 1972] [Kemp 1960] [Kennedy and Fields 1962] [Kharchenko and Kryukov 2018] [Khramov 1974] [Kimmel et al 2011] [Klomfass and Müller 1997] [Koh 1962] [Koshmarov and Gorskaya 1965] [Kozak and Sharipov 2012] [Krupp 1965] [Kuby et al 1967] [Kudryashova et al 2009] [Kuethe et al 1959] [Kumar and Bansal 2023] [Kumar and Jain 1974] [Kumar and Reddy 2014] [Kumari and Nath 1982] [Langberg 1959] [Lei et al 2013] [Lennon and Poirter 1974] [Levin and Markov 1987] [Li and Geiger 1957] [Libby 1970] [Libby and Sepri 1968] [Liu and Qiang 2012] [Lu and Liu 2012] [Lunev 1971] [Lunev and Khramov 1970] [Lü et al 2013] [Markov 1981] [Markov 1984] [Markov 1987] [Menees et al 1985] [Meyer 1960] [Recent Langley Aerothermodynamic Laboratory] [Mifsud et al 2012] [Morgado et al 2022] [Moss, James N. 1986] [Munipalli et al 2005] [Musal 1962] [Muthanna and Nath 1976] [Nag et al 2023] [Nath 1971] [Nie and Liu 2013] [Nishida and Sugimoto 1973] [Nomura 1983] [Oguchi 1958] [Olivier 1995] [Osiptsov and Shapiro 1992] [Papenfuβ 1974] [Park 2013] [Pavlov 1967] [Pearce 1970] [Peigin 1988] [Pezzella 2013] [Pollin 1964] [Porter and Cambel 1966] [Probstein 1961] [Rataczak et al 2026] [Reba 1964] [Reba and Christian 1963] [Reddy and Sinha 2009] [Ren et al 2019] [Rochefort et al 1974] [Rotman and Meltz 1961] [Saida 1972] [Santos et al 2021] [Scala 1962] [Scala and Workman 1959] [Scott and Derry 1982] [Sergeev et al 1971] [Shang and Surzhikov 2011] [Sharma et al 2024] [Shi et al 2025] [Shichao 2019] [Simeonides 2006] [Sinnott 1963] [Smith 2021] [Smith et al 1965] [Sogin 1992] [Stern 2004] [Sternberg 2010] [Stewart and Golden 1970] [Stulov and Shapiro 1969] [Sun et al 2018] [Sun et al 2020] [Surzhikov 2013] [Surzhikov 2016] [Surzhikov 2020] [Suslov 1969] [Suzuki et al 2002] [Tauber 1986] [Taylor 1961] [Throckmorton 1993] [Tong 1965] [Turchi and De Persis 2026] [Umansky-Castro et al 2021] [Varaksin 2001] [Varaksin and Ivanov 2003] [Vasil’kov 1975] [Viviani and Pezzella 2009] [Viviani and Pezzella 2010] [Voronkin 1971] [Votta et al 2013] [Wada and Kubota 1992] [Weil 1963] [Weiland et al 2004] [Weilmuenster et al 1997] [Weilmuenster, K. J. and Gnoffo, Peter A. 1992] [Xiao and He 2018] [Xu et al 2008] [Xuguo et al 2017] [Yadav and Guven 2013] [Yadav and Guven 2013] [Yang et al 2022] [Yao et al 2023] [Yassin et al 2025] [Yen 1986] [Yin et al 2024] [Young et al 1972] [Yu et al 2022] [Yu et al 2022] [Yu et al 2025] [Zhao 1993] [Zhao and Li 2018]

Hypersonic aerodynamics, boundary layers and transition

The configuration. Hypersonic aerodynamics, viscous interaction, boundary layer instability and transition, roughness and wind tunnel technique.

210 records. [266 On ascent guidance of hypersonic vehicle 1994] [Adamov et al 2014] [Aerodynamics Calculation of Reentry Body in Hypersonic Flowfield 2013] [Agnone and Prakasam 1987] [Ai and Chen 2019] [Air Force Test Pilot School Edwards Afb Ca 1987] [Fluid-Thermal-Structural Interactions in Ramp-Induced] [Antonova and Skiba 1968] [Ardema, Mark D. et al 1994] [Arguchintseva 1999] [Ashby, G. C., Jr. and Staylor, W. F. 1968] [Auelmann 1965] [Avallone et al 2016] [Baganoff 1990] [Bao et al 2024] [Bauer 1969] [Bibb, Karen L. et al 2011] [Bogdonoff 1970] [Bogdonoff 1999] [Boyd 2002] [Boyd 2004] [Boyd 2008] [Brauckmann, G. J. 1986] [Brown, James L. 2014] [Buck, Gregory M. et al 2008] [Byrkin 1971] [Cai and Huang 2022] [Chandler 2003] [Chang, Chau-Lyan et al 2010] [Chen 2020] [Chen and Zhao 2019] [Cheng et al 2023] [Chu 1967] [Cockrell, Charles E., Jr. et al 1996] [Cole and Aroesty 1965] [Covell et al 1988] [Cox et al 1966] [Cresci 1966] [Cummings and Yang 2003] [Cunningham 1987] [Czysz 1963] [Dietrick 2013] [Dong and Zhao 2021] [Duan and Xiao 2017] [Edquist, Karl T. 2006] [Ericsson 1969] [Ericsson 1977] [Evans and Walton 2017] [Feie and Kretz 2008] [Feldick and Modest 2011] [Fiala et al 2014] [Filatov 1972] [Finson 1973] [Fiorentini and Serrani 2012] [Fong et al 2014] [French 1968] [Fu et al 2019] [Ginoux 1966] [Gnoffo et al 2011] [Goates et al 2026] [Goldberg and Scala 1965] [Golubkin 1995] [Griffith, B. J. et al 1983] [Griffith, B. J. et al 1986] [Groves et al 2005] [Gui 2019] [Gui et al 2023] [Guo and Cao 2026] [Gülhan et al 2026] [Haley and Zhong 2023] [Han et al 2022] [Harloff 1988] [Harney 1963] [Hawthorne, P. J. 1976] [Hayes et al 1960] [Herbert 1992] [Hoffmann 2000] [Holden, Michael S. and Rodriguez, Kathleen 1994] [Holden, Michael S. et al 1990] [Hollis 2025] [Hollis 2019] [Horstman 1963] [Horvath, Thomas J. et al 2002] [Houwink and Richards 1973] [Hromas and Lees 1962] [Inger, George R. 1995] [Johnson and Joseph A. 1977] [Cheatwood et al] [Cheatwood et al] [Kanda et al 2006] [Kawato et al 2005] [Kawecki 1977] [Kelly 1973] [Khorrami 2003] [Khorrami and Smith 1994] [Kimmel and Poggie 1997] [King 1962] [Kitamura 2016] [Klothakis and Nikolos 2024] [Kussoy et al 1970] [Ladson, C. L. 1970] [Ladyzhenskij 1963] [Larina 1985] [Lee and James T. 1963] [Lee and Park 2024] [Lee and Rasmussen 1978] [Lees and Kubota 1972] [Levermore and Brio 1994] [Levin and Smith 1969] [Levy 1969] [Lewellen and Mirels 1966] [Lewis and McRonald 1992] [Li and Nagamatsu 1953] [Li et al 2009] [Li et al 2013] [Li et al 2021] [Li et al 2025] [Li et al 2025] [Lin 1981] [Lobb et al 1955] [Logan and Stalker 1977] [Lu and Qian 2024] [Lu et al 2025] [Lukasiewicz 1961] [Maikapar 1967] [Mars Sample Return, Sample] [Marvin, Joseph G. et al 2013] [McGrory 2001] [McRonald, Angus D. 1995] [Miles and Brown 2002] [Miyashita et al 2025] [Mohammed et al 2010] [Monaghan 1959] [Moss 1986] [Murbach 1993] [Nichols 1975] [O’Brien and Lewis 2002] [Oberkampf and Aeschliman 1992] [Ohmichi and Suzuki 2014] [Olsen 1965] [Ortloff 1968] [Parent 2021] [Peltier et al 2016] [Pendleton et al 1995] [Pittman and Dillon 1977] [Pritchard and Holloway 1967] [Qu et al 2018] [Ramesh 2002] [Reda et al 2012] [Reed 1997] [Reshotko 1987] [Richardson and Herrmann 1966] [Russian Aerospace Literature This month: Hypersonic Aerodynamics 1996] [Saikia and Brehm 2025] [Saltzman et al 2007] [Sammonds and Kruse 1975] [Scaggs 1966] [Schmidt and Lovell 1997] [Schneider 2009] [Sforza 1967] [Sims and Hahn 1964] [Smarslok 2015] [Song and Choi 2020] [Spearman, M. L. 1984] [Spravka and Jorris 2015] [Stetson 1990] [Sun et al 2026] [Swigart 1962] [Swigart 1963] [Gokcen et al] [Tawfiqur et al 2011] [Terry and Barber 2007] [Thomas 1965] [Tirskii 1993] [Turbulization of the Wake behind a Single Roughness Element on a Blunted Body at a Hypersonic Mach Number 2017] [Vaganov et al 2009] [Van 1963] [Varwig 1963] [Walchner 1974] [Walker, Ira J. et al 1993] [Wang and Gao 2013] [Wang et al 2017] [Wang et al 2022] [Wang et al 2023] [Watt and Aronson 1964] [Wheaton and Schneider 2012] [Wheaton and Schneider 2014] [Wilfred H Dukes 1962] [Williams et al 2021] [Wolverton 2018] [Wood et al 2010] [Wu and Xiao 2009] [Wu et al 2021] [Xu and Zhang 2015] [Yan 2014] [Yang 1994] [Yang and Li 2023] [Yang and Liu 2017] [Yao and Xia 2023] [Yao and Xia 2024] [Yates and Bennett 1972] [Young 1966] [Young, J. C. 1982] [Zeiler et al 1999] [Zhang 1992] [Zhang et al 2025] [Zhao et al 2019] [Zhi et al 2015] [Zhou 2023] [Zhu and Shen 2015]

Solar arrays, space photovoltaics and power systems

The power ceiling. Space solar cells and arrays, their radiation, plasma and arcing degradation, deployment and dynamics, and the spacecraft electrical power system.

204 records. [5530335 Battery regulated bus spacecraft power control system 1996] [5604430 Solar array maximum power tracker with arcjet load 1997] [A method to optimize the solar cell power supply for interplanetary spacecraft 1964] [Acero et al 2023] [Adams and Hedgepeth 1981] [Alghuwainem 1997] [Amundsen et al 2005] [Amundsen et al 2003] [An et al 2022] [Awasth 2022] [Bai et al 2021] [Belov 2006] [Bian et al 2018] [Bodeau 2015] [Brinker et al 1990] [Bukreev et al 2021] [Bulut and Sözbir 2026] [Burgess 1995] [Butler et al 1964] [Camarillo Abad et al 2025] [Cao et al 2019] [Cao et al 2021] [Carter and Tada 1973] [Chamberlain et al 2021] [Chamberlain et al 2019] [Chen et al 2014] [Chen et al 2017] [Chen et al 2020] [Cherchas and Hughes 1973] [Chetty 1990] [Chetty et al 1991] [Cho and Hastings 1993] [Cho et al 2003] [Cho et al 2005] [Cho et al 2009] [Christopher 2016] [Cussen 1972] [de Groh and McCollum 1995] [de la Cruz et al 1996] [Dec and Amundsen 2003] [Dec et al 2002] [Derbis et al 1991] [Dever et al 1995] [Dickman et al 2004] [Guidice 1990] [Du et al 2025] [Dupont 1966] [Eder 1973] [El-Sherbiny et al 2013] [Equivalent Flux Smoothing in the Problem of Solar Cells Radiation Degradation Minimization during a Low-Thrust Geostationary Orbit Insertion 2019] [Felkel and Wolff 1969] [Ferguson et al 2017] [Fetzer et al 2007] [Finckenor et al 2006] [Firat 2026] [Fisher 1991] [Flood 1991] [El-Sherbiny et al 2013] [Galatis et al 2017] [Galofaro et al 2006] [Gao et al 2012] [Gerhard et al 2015] [Girish et al 2007] [Hastings and Cho 1990] [Hawley 2016] [He et al 2022] [Herron et al 1973] [Hillard 1994] [Hillard and Ferguson 1993] [Hoang et al 2010] [Hoffman and Scheiman 1997] [Hough and Elrod 1969] [Hsu 1981] [Huang 2013] [Huang et al 2025] [Hwu et al 2003] [Jain and Flood 1992] [Jan and Chiou 2002] [Ji 2026] [Jones and Spence 2011] [Jones et al 1993] [Keener et al 2004] [Kellogg 1993] [Wright et al] [Kevern and Massie 1969] [Khan et al 2020] [Kim et al 2012] [Kong et al 2025] [Koontz et al 1994] [Kotamraju et al 2019] [Kreith 1980] [Kumar and Pellegrino 1996] [Kuninaka and Kuriki 1987] [Kuninaka et al 1990] [Kurland and Stella 1988] [Kurland et al 2000] [Lanzerotti 1969] [Lanzerotti et al 1991] [Lee 2018] [Li and Yan 2014] [Li et al 2022] [Li et al 2026] [Likar and Bogorad 2008] [Lohmeyer et al 2018] [Lorenz 1998] [Lozinski et al 2019] [Ma et al 2026] [Mahmood et al 2025] [Malone et al 1993] [Maloney 1981] [Calassa and Kackley 1995] [Marín-Coca et al 2023] [Matias 2013] [Chamberlain et al 2020] [Messenger et al 2014] [Metz 1986] [Mikulas et al 2015] [Mokhtar et al 2025] [Morozov and Lopatin 2011] [Murozono and Thornton 1998] [Na et al 2014] [Negley et al 1989] [Nesterishin et al 2018] [Nichols et al 2015] [Nömayr et al 2017] [Oda et al 2012] [Okumura et al 2009] [Okumura et al 2009] [Olbert 1991] [Oukil and Boudjemai 2020] [Pan 2015] [Pankop et al 2006] [Papula and Stowell 1986] [Park et al 2019] [Parks and Katz 1979] [Patterson 1984] [Patterson and Crabtree 1982] [Piszczor 2003] [Property changes induced by 1993] [Qin et al 2018] [Radiation damage in satellite solar cell power systems 1961] [Ralph 1973] [Ranger spacecraft power system 1961] [Reyes et al 2019] [Richardson and Warren 1971] [Saad et al 2026] [Samuels 1984] [Santoni and Piergentili 2008] [Sasaki 1999] [Sasaki and Tanaka 2002] [Sattar and Wei 2017] [Sayed and Partain 1975] [Schaefer et al 1963] [Scott-Monck et al 1980] [Sharma et al 1993] [Shaw and Falconer 1971] [Shimizu et al 2017] [Skor and Hoffman 1997] [Skurat et al 2011] [Soeder and Button 1999] [Solar cell array design handbook 1982] [Solar Cell High Efficiency 1979] [Soldi et al 1997] [Soma et al 2012] [Spire Corp Bedford Ma 1989] [Spire Corp Bedford Ma 1996] [Starchenko 2019] [Starchenko 2020] [Statler 1971] [Statler and Walker 1980] [Stidham et al 1994] [Stillwell et al 1985] [Strobl et al 1995] [Summers et al 1994] [The spacecraft power supply system 1966] [Thiemann and Bogus 1988] [Thornton and Kim 1993] [Thornton et al 1995] [Timmons 1996] [Toyoda et al 2004] [Toyoda et al 2005] [Turner, G. and Hill, H. 1982] [Vayner 2015] [Vayner 2016] [Vega-Fleitas et al 2026] [Walker and Statler 1988] [Wang and Wang 2023] [Wang et al 2024] [Westgate et al 2022] [Wilson et al 1983] [Wu et al 2024] [Xu et al 2025] [Yang et al 2004] [Yang et al 2018] [Yang et al 2022] [Yeh and Chu 1996] [Yokota et al 2024] [You 2012] [Zhang and Zhang 2013] [Zhang et al 2014] [Zhang et al 2024] [Zhang et al 2024] [Zhu et al 2017] [Öz and Bulut 2025]

Orbital debris, re-entry prediction and disposal

The disposal obligation. Orbital debris environment and mitigation, post-mission disposal, re-entry prediction of uncontrolled objects and active removal. 159 of these 197 records date from 2012 or later, the years in which disposal became an obligation.

197 records. [Adilov et al 2020] [Ahedo and Sanmartin 2002] [Alfriend and Lewis 1994] [Aneja 2024] [Anil Kumar and Mukherjee 2025] [Anilkumar and Reddy 2009] [Anselmo and Pardini 2015] [Aorpimai and Navakitkanok 2015] [Aslanov 2019] [Aslanov and Doroshin 2002] [Aslanov and Ledkov 2021] [Banik et al 2025] [Baranov et al 2017] [Barkova 2022] [Barry 2022] [Bathi 2026] [Battiston et al 2017] [Bennett 2025] [Bennett et al 2023] [Bernat 2020] [Berthoud and Mandeville 1997] [Bhusal and Subbarao 2019] [Bianchi et al 2024] [Boley and Byers 2021] [Bongers et al 2025] [Borelli and Colombo 2026] [Boutamine et al 2007] [Breda and Markova 2026] [Cai et al 2022] [Cerf 2012] [Cerf 2015] [Ceriotti and Radice 2014] [Chhabra et al 2026] [Cho 1994] [Chobotov 1990] [Chobotov et al 1997] [Choi 2021] [Choi et al 2015] [Choi et al 2017] [Choi et al 2024] [Choudhary 2025] [Connell et al 1991] [Cowardin et al 2010] [Crowther 1992] [Cuadrat-Grzybowski and Gill 2024] [de Paula and Celestino 2019] [Ding et al 2023] [Donou-Adonsou et al 2025] [Dr. Shashank Shekhar 2023] [Duchek et al 2015] [Ed. Siregar et al 2024] [Ellery 2019] [Feder 2022] [Feoktistova and Turkina 2022] [Fernández et al 2022] [Filho et al 2025] [Filho et al 2025] [Giudici et al 2024] [Golubek et al 2023] [Gomes Vieira et al 2021] [Grishko et al 2024] [Guo et al 2023] [Gupta 2022] [Gómez and Walker 2017] [Ham and Lin 2016] [Han et al 2021] [Handmer and Freeland 2022] [Hanson 2014] [Haridim et al 2026] [Hejduk et al 2012] [Henning et al 2020] [Herdiansyah et al 2016] [Heumassej et al 2026] [Hickson 2018] [Hosseini et al 2021] [Hu et al 2021] [Huang et al 2026] [Hurova 2024] [Ivanov et al 2007] [İpek 2025] [Janin 1991] [Johnson 2001] [Johnson, Nicholas L. 2001] [Johnson 2006] [Johnson 2008] [Jorgensen and Sharf 2020] [Parodi et al] [Kang 2022] [Karimov and Buyanov 2025] [Kawamoto et al 2018] [Kelley and Jarkey 2015] [Kelley et al 2014] [Kessler 1991] [Kezirian 2021] [Khatniuk et al 2019] [Kim 2020] [Klinkrad 2017] [Kolyuka et al 2012] [Kosambe 2019] [La Marca et al 2024] [Lambright 2026] [Langlade 2018] [Lederer et al 2018] [Ledkov and Aslanov 2025] [Lee and Kang 2023] [Lewis 2021] [Lewis and Yazadzhiyan 2024] [Li 2015] [Li 2023] [Li et al 2026] [Lifson et al 2025] [Limiting Future Collision Risk 2011] [Liu et al 2022] [Lovell 2025] [Luna et al 2026] [Macauley 2015] [Mahaseth et al 2022] [Marcelo Araujo da Silva and Matheus Alves de Lima 2024] [Marcus and Sedwick 2017] [Marty et al 2023] [Matney et al 2017] [Matney 2013] [Maury et al 2020] [McKnight and Lorenzen 1989] [Migaud 2020] [Morand et al 2014] [Moury et al 2014] [Mullick et al 2019] [Nathalie et al 2024] [Navaz and Ntantis 2026] [Nguyen et al 2018] [Nomura and Kanazaki 2019] [Omar, Sanny R. and Bevilacqua, Riccardo 2017] [Pardini and Anselmo 2020] [Patel et al 2017] [Percy and Landrum 2014] [Rafano Carná and Bevilacqua 2019] [Rajapaksa and Wijerathna 2017] [Reynolds et al 1983] [Ribeiro et al 2018] [Richards 2010] [Roberts and Harkness 2007] [Robinson 1999] [Roshan et al 2022] [Rossi 2002] [Rossi 2020] [Miller et al 2021] [Saboktakin and Spitas 2023] [Saddul et al 2024] [Sanchez 2025] [Sankaranarayanan et al 2022] [Schall 2002] [Schaub and Sternovsky 2014] [Schaus et al 2019] [Schild and Noomen 2023] [Schildknecht and Hager 2014] [Schobert and Paul 1997] [Serfontein et al 2021] [Shan and Shi 2022] [Shcheglov et al 2023] [Sheer and Li 2019] [Sheer et al 2019] [Slejko et al 2021] [Smirnov et al 2015] [Smith et al 2024] [Spencer et al 2025] [Stansbery and Johnson 2012] [Stern 2008] [Stokes et al 2020] [Stuart et al 2016] [Su 2017] [Susanti 2021] [Svotina 2024] [Svotina 2026] [Tewari 2009] [Tortora et al 2006] [Turyshev 2026] [Twiss 1965] [Uchida 2015] [Usovik 2023] [Vedder and Tabor 1991] [Veniaminov et al 2026] [Verma et al 2023] [Visagie et al 2015] [Vishnuprakash B and Anand Radhakrishnan 2024] [Walker et al 2000] [Wang 2016] [Wang et al 2023] [Wang et al 2025] [Wiegmann, Bruce M. 2011] [Yan 2023] [Yang 2023] [Yang et al 2016] [Yasaka 1990] [Yates and Jonas 1995] [Zedd 2014] [Zhang et al 2023]

Orbit theory, perturbations and orbit transfer

The manoeuvre arithmetic. Satellite orbit theory, oblateness and other perturbations, stationkeeping and impulsive and low-thrust orbit transfer.

181 records. [231 Orbit control of a recalcitrant satellite 1994] [Ahmed et al 2010] [Ahmed K. Izzet 2023] [Aksnes 1970] [Aksnes 1973] [Al-Sawad et al 2022] [Alimov et al 2001] [Allan 1961] [Altman 1961] [Augenstein 1959] [Balakin et al 2018] [Barrows, D. and Bedell, H. 1983] [Baxter 1980] [Betts 1977] [Billik and Price 1963] [Black et al 1968] [Bleick 1963] [Bleick and Faulkner 1963] [Blitzer 1959] [Blitzer and Anderson 1981] [Bobojć and Drożyner 2007] [Bolandi and Abrehdari 2018] [Bonin and Kaya 2007] [Bonnard and Caillau 2007] [Bosanquet 1958] [Braga-Illa 1969] [Breakwell and Chanal 1986] [Brenner 1962] [Broucke 1994] [Bruce 1965] [Brumberg et al 1995] [Brusch 1979] [Buchar 1958] [Buckingham et al 1965] [Burton and Wassgren 1992] [Butikov 2015] [Caillau and Noailles 2001] [Chen and Sheu 2006] [Cooley and Easton 1969] [Coverstone and Prussing 2003] [Crawford 1987] [Davis 1963] [Diliberto 1966] [Dyer 1966] [Edelbaum 1965] [Edelbaum 1966] [El-Enna 2003] [El-Enna 2004] [Ferguson 1964] [Furber 2014] [Gao 2007] [Gao 2009] [Garfinkel 1959] [Geyling 1964] [Gordon 1973] [Gulp 1967] [Gurfil 2003] [Gurtu 1981] [Gustafson and Kriegsman 1973] [Hitzl and Zele 1987] [Hope and Middour 1993] [Hua and Shao 2015] [Hudson et al 2017] [Hwang and Hwang 2002] [Ibrahim 2020] [Igarashi and Spencer 2005] [Jamison and Coverstone 2010] [Junkins 2015] [Kalil and Martikan 1963] [Kechichian 1997] [Kechichian 1998] [Kechichian 2000] [Kelley et al 1985] [Khramov 2019] [Kim et al 2009] [King-Hele 1958] [King-Hele 1982] [King-Hele 1989] [Kluever 1995] [Kluever 1998] [Kluever 2004] [Kluever and Oleson 1998] [Kozai 1960] [Kuhlman 1963] [Kuijper 2008] [Kéchichian 2009] [L’Afflitto and Sultan 2011] [Larbi and Bergner 2012] [Lass and Lorell 1961] [Lee 1964] [Lee and Bang 2009] [Lin and Hwang 2018] [Lin and Xin 2003] [Lin and Yan-rong 2006] [Lubowe 1969] [Luo et al 2022] [Luo et al 2024] [Lyddane and Cohen 1962] [Malyshev et al 2013] [Mathematical model filtering canonical parameters of satellite-repeater in orbital motion 2019] [Matogawa 1983] [Mengali and Quarta 2005] [Message 1960] [Mission Design Implications of an Inclined Elliptical Geosynchronous Orbit (International Ultraviolet Explorer) 1977] [Mišoň 1973] [Montero Miñan et al 2023] [Moyer 1969] [Mueller 1978] [Mungan 2018] [Munick 1962] [Métris and Vokrouhlický 1996] [Niemeier 1966] [Ocampo and Rosborough 1999] [Ocampo and Rosborough 1999] [Panagopoulos et al 2024] [Parks 1983] [Petukhov 2009] [Pollard 2000] [Porcelli and Vogel 1980] [Prado and Broucke 1994] [Pritchard 1999] [Prussing 1969] [Raja et al 2021] [Redding 1984] [Rim et al 2000] [Rosengren 1982] [Saleh and Abdulla 2020] [Salmin et al 2019] [Scala et al 2021] [Schooley 1962] [Sconzo 1966] [Sedelnikov and Potienko 2015] [Sellamuthu and Sharma 2018] [Shakouri et al 2020] [Shang et al 2015] [Sharaf 1992] [Sharma and James Raj 1988] [Shirazi 2015] [Shirazi and Mazinan 2015] [Shou 2014] [Shrivastava and Rajasingh 1975] [Small 1977] [Smith 1961] [Smith 1962] [Smith 1974] [Smith and Wright 1964] [Soleymani and Toloei 2015] [Someya et al 2010] [Sowell and Taheri 2024] [Spencer and Culp 1995] [Sterne 1958] [Taff 1979] [Taheri 2025] [The orbit of an equatorial earth satellite 1963] [Ting 1960] [Ulybyshev 2007] [Van der Ha and Modi 1978] [Vargo 1963] [Vasil’ev and Pasechnik 2002] [Vind 1961] [Vinti 1960] [Vishwakarma et al 2014] [Wagner 1975] [Walden 1968] [Wallner and Camiel 1966] [Walls et al 1987] [Wang and Zhang 2024] [Wiesel and Alfano 1985] [Wilkie and Stevens 1964] [Wolfsberger et al 1983] [Wood et al 1982] [Xu et al 2010] [Yang et al 2010] [Yang et al 2026] [Yeh 1972] [Yin et al 2025] [Zerbini 1980] [Zhang et al 2016] [Zheng et al 2010] [Zhong and Gurfil 2013] [Zhou and Wu 2014]

Launch vehicles and access to orbit

Access. Launch vehicles, their guidance, loads and environments, and the launch market.

157 records. [Adimurthy 1976] [Adimurthy 1987] [Aditya Chowdhury, Vishnu G Nair 2017] [Aggarwal, Pravin 2007] [Air Force Space Command Space Missile Sys Ctr 2013] [Aksen et al 2024] [Allen 2002] [Beardslee 1964] [Bell et al 1995] [Benedikter et al 2021] [Benedikter et al 2022] [Williams et al] [Brinda and Dasgupta 2006] [Brower 2006] [Brusch 1977] [Burton et al 2006] [Calise and Brandt 2004] [Cesta and McLouth 1969] [Cho et al 2021] [Choi and Yoon 1999] [Christie 2026] [Clapp 1994] [Clement et al 2005] [Conley et al 2003] [da Silveira and da Silva Fernandes 2023] [Dasgupta 1998] [Deschamps 1985] [Dileep et al 2015] [Dileep et al 2016] [Dordain 1977] [Downing and Plotkin 1996] [Duret and Fabrizi 1999] [Ehricke 1964] [Ericsson and Pavish 2000] [Evans et al 1963] [Fesmire and Sass 2008] [Flittie et al 1992] [Freeborn et al 2005] [Gath and Calise 2001] [General Dynamics Corp San Diego Ca 1992] [Godai 1986] [Godai 1987] [Goldberg 2005] [Gretz 1962] [Gunderson and Hardy 1965] [Hattis 1981] [Hodges et al 1992] [Holladay et al 2014] [Howard and Hansen 2006] [Huebner et al 2009] [Hueter 1995] [Humble and Pierson 1995] [Hwang 2019] [Ikawa 1992] [Jenkins and Roy 1968] [Jurovics 1961] [Jutty K et al 2000] [Kabe 2000] [Kamm and Johnson 1973] [Kayama and Takenaka 1980] [Kibbey 2015] [Ko et al 2024] [Koelle 1981] [Koelle 1986] [Koelle 1999] [Krause 1990] [Kuznetsov 2023] [Lalithambika and Dasgupta 2007] [Launch vehicle booster avionics 2000] [Leng et al 2014] [Leung and Calise 1994] [Levandovich et al 2021] [Loftus and Brasher 1986] [Lourme 1987] [Lu 1996] [Luke 1993] [MacConochie et al 1980] [Madeira and Rios-Neto 2000] [Mammen et al 1990] [Manski, Detlef and Martin, James A. 1988] [Martin 1982] [Martin 1983] [Martin 1984] [Martin 1985] [Martin 1989] [Martin and Wilhite 1980] [Martin Co Baltimore Md 1963] [Matsuo and Kawaguchi 1995] [McCurdy, David R. and Roche, Joseph M. 2004] [McCurry 1996] [McInerny 1996] [Meyers 1991] [Miele et al 2001] [Miele et al 2005] [Miller 1963] [Milliken 1965] [Milstead 1964] [Miyazawa and Fukushima 1991] [Moch 1966] [Moraes 2001] [Motiwala, Samira A. et al 2014] [Naftel and Powell 1985] [Nichols et al 1992] [Nikolayev and Komatsu 2004] [Omar et al 2011] [Otte, Neil E. et al 2008] [Pamadi 1995] [Performance Analysis of Powered Explicit Guidance for Satellite Launch Vehicle 2008] [Portanova et al 1992] [Powell 1962] [Powell et al 1991] [Powell, Richard W. et al 1991] [Rehder, J. J. 1977] [Reilly 1979] [Richard and Christophe 1995] [Rillings and Roy 1970] [Robust Optimal Trajectory Design of a Launch Vehicle Using Particle Swarm Optimization 2022] [Roh and Kim 2002] [Rosenbaum 1971] [Sanford et al 2003] [Seltzer 1970] [Seltzer 1970] [Shibato 1995] [Shrivastava and Reddy 1976] [Sikharulidze et al 2005] [Sinha and Shrivastava 1990] [Snyder and Lenihan 1968] [Somanath et al 1999] [Song et al 2020] [Stampfl and Meyer 1988] [Staniszewski 2001] [Stengel 1987] [Stout and Snell 2000] [Sun et al 2024] [Suzuki 2004] [Swaim 1968] [Swaim 1969] [Swaminathan et al 2023] [Takamatsu et al 1986] [Tanner 1997] [Tewell et al 1986] [Thomas 1987] [Thornton 1977] [Tomioka and Kohsetsu 1990] [Varaprasad and Rao 2006] [Vittal and Bhat 1993] [Wang 2015] [Wilhite 1980] [Williams, R. W. 1996] [Wright and Sponnick 1989] [Xuan et al 2009] [Yau et al 1995] [Ye et al 2025] [Yeniay et al 2006] [Yoon and Ahn 2016] [Zhang et al 2024] [Zheng et al 2020]

Lifting bodies, the Shuttle orbiter and the reusable demonstrators

The vehicles the X-37 inherited from. The lifting bodies, the Space Shuttle orbiter, and the X-33, X-34 and X-38 demonstrators. Five of these 140 records date from 2012 or later, which is a finding and not a gap. The lifting bodies and the Shuttle orbiter stopped generating literature under their own names once they stopped flying, and the recent records are flow studies of a lifting-body transition model, a guided entry study for a crewed lifting body and a study of the European re-entry demonstrator’s steps and gaps.

140 records. [Adams 1975] [Aggarwal, Shiv 2003] [Amis et al 2003] [Argyris et al 1989] [Ashford 1965] [Audley and Hodge 1982] [Baston and Moorehead 1976] [Bernot, P. T. 1979] [Berry, Scott A. et al 1999] [Bertin et al 1996] [Bikdash et al 1999] [Blanchard and Hinson 1989] [Blanchard, R. C. and Rutherford, J. F. 1984] [Bradley and Throckmorton 1981] [Brauckman, Gregory J. and Scallion, William I. 2003] [Brauckmann, Gregory J. 1998] [Brewer et al 1973] [Bulirsch and Chudej 1992] [Campbell et al 2006] [Carrier and Pope 1978] [Carter and Kaul 1975] [Chen et al 2026] [Cooper 1981] [Cooper and Sawyer 1983] [Cubley and Ellis 1978] [Direct numerical simulations of hypersonic boundary layer transition over a hypersonic transition research vehicle model lifting body at different angles of attack 2023] [Dote and Theodore 1981] [Doyle 1982] [Ehlers 1986] [Ehret 1980] [Elder, D. J. 1975] [Elliott and Hankey 1968] [Ericsson and Reding 1978] [Forsberg, K. J. et al 1973] [Freeman 1982] [Freeman, D. C., Jr. and Spencer, B., Jr. 1980] [Fullerton, C. G. 1975] [Gamble and Young 1982] [Gamble et al 1985] [Gillins, R. L. 1975] [Griffin 1985] [Grooms et al 1984] [Hall, Charles E. et al 1998] [Hallion 1998] [Harting 1981] [Helers and Kraemer 1977] [Helms 1983] [Himelblau 1972] [Himelblau 1972] [Holleman and Adkins 1964] [Holloway and Throckmorton 1995] [Humes 1978] [Ikawa 1977] [J Muylaert et al 1998] [John G McTigue 1970] [Kanipe 1983] [Kanipe, D. B. 1982] [Katz and Parks 1983] [Kempel, Robert W. et al 1994] [Khan et al 1995] [Kilgore, R. A. and Davenport, E. E. 1974] [Kim et al 1984] [Kleb and Weilmuenster 1994] [Ko 1988] [Kraemer and Ehlers 1975] [Krek and Stalker 1992] [Kwon et al 1993] [Lawing and Nystrom 1980] [Lee, D. B. and Harthun, M. H. 1982] [Li 1981] [Liemohn 1976] [Lomas, James J. et al 2001] [Loomis, Mark P. et al 2004] [Lu and Hanson 1998] [Marichalar et al 2006] [Marichalar, Jeremiah J. et al 2006] [Meng et al 2009] [Ming H Tang 1970] [Monta, W. J. and Rausch, J. R. 1973] [Montez, M. N. and Madden, M. F. 1982] [Mouyos, William and Wangu, Srimal 1998] [NDE nondestructive evaluation of 1994] [Noor et al 1993] [Norman et al 1982] [Norton and White 1977] [Norwood 1985] [Nutt et al 1979] [Oepomo 1985] [Oglesby, T. L. 1975] [Olynick 1998] [Ormiston and Tanzilli 1973] [Orton and Mark 1984] [Palmer et al 1999] [Paluszek 1983] [Pamadi, Bandu N. and Brauckmann, Gregory J. 1999] [Paté-Cornell and Fischbeck 1993] [Petley et al 1983] [Powell and Freeman 1985] [Prabhu and Tannehill 1986] [Pruett et al 1983] [Putnam et al 2014] [Raitt 1987] [Rakich et al 1984] [Ramnath and Sinha 1975] [Rausch and Roberts 1975] [Rausch, J. R. 1975] [Rausch, J. R. and Roberge, A. M. 1973] [Redding and Adams 1987] [Reichenfeld, Curtis J. and Jones, Paul G. 1999] [Chock 1992] [Robert W Kempel et al 1970] [Rochelle et al 1973] [Satterfield 1974] [Scallion 2005] [Scallion, William I. 1999] [Schweikhard, Keith A. et al 1998] [Shi et al 1969] [Siemers and Larson 1979] [Simon 1978] [Smith et al 1983] [Sourgen et al 2012] [Stanley et al 1989] [Stevens 1981] [Strahan 2001] [Streb 1973] [Surber and Olsen 1978] [Tang, M. H. and Pearson, G. P. E. 1971] [Tannehill 1984] [Tartabini et al 2002] [Throckmorton 1983] [Throckmorton 1993] [Ting, P. C. 1982] [van Oort et al 2007] [Walyus and Dalton 1991] [Wells 1985] [Kleb and Weilmuenster 1992] [Wu et al 2001] [Wurster et al 1999] [Young and Underwood 1983] [Zhang et al 2026]

Reusable launch vehicles, operations and economics

The economics that followed. Reusable launch vehicles, their design, control, operations, turnaround and cost.

137 records. [Abrahamm and Valsa 2018] [Bailey et al 2002] [Balepin et al 2001] [Bekey, Ivan 1994] [Berend and Talbot 2006] [Biswal M 2023] [Blackstock 1970] [Borovik et al 2019] [Borovik et al 2022] [Brevault et al 2020] [Brown and Olds 2006] [Butler et al 2005] [Calvignac, Jacky and Tramel, Terri 2003] [Cerro, Jeff et al 2002] [Chen et al 2011] [Cheng et al 2021] [Chiba et al 2006] [Collicott 2025] [Cook and Hueter 2003] [Cordes and Hertzfeld 1997] [Cresto Aleina et al 2016] [De Ridder and Mooij 2011] [Der Kiureghian 2001] [Dissel et al 2007] [Doman 2004] [Donahue et al 2008] [Dong et al 2023] [Dumbacher, Dan L. and Smith, Dennis E. 2002] [Fagan et al 2003] [Ferrandon 1997] [Filatyev et al 2014] [Fletcher, J. C. 1988] [Freeman et al 1997] [Frye and Kennedy 1998] [Fusaro et al 2016] [Gao et al 2023] [Gong et al 2022] [Guadagnini et al 2023] [Hale, Joseph P. 1997] [Hall and Shtessel 2006] [Heiser 2010] [Hellman et al 2011] [Hellman et al 2011] [Hong et al 2005] [Huber 1988] [ISRO Releases the Special Issue on ‘Reusable Launch Vehicle-Technology Demonstrator’ 2018] [Jaffe 1988] [Jategaonkar et al 2006] [Jia et al 2020] [Johnson et al 2009] [Jules, Kenol 1993] [Kam and Gage 2004] [Khamlak 2026] [Kiehn 2020] [Kim and Kang 2026] [Klimenko et al 2021] [Kluever 2007] [Koelle 1989] [Koelle 1993] [Koelle 1997] [Komatsu and Ohyagi 2001] [Komatsu et al 2005] [Komatsu et al 2008] [Krivanek, Thomas M. et al 2002] [Kroncke 1985] [Lee et al 2025] [Li et al 2025] [Li et al 2026] [Liao et al 2023] [Lockheed Martin Skunk Works 1999] [Logsdon and Williamson 1997] [Long et al 2026] [Lyles, Garry 1999] [Mankins 2002] [Manokaran et al 2009] [Martindale 2006] [Menon et al 2025] [Merriam, Marshal L. 2000] [Merrifield, D. V. 1972] [Mo et al 2024] [Mukundan et al 2022] [Najam 2014] [Nambara et al 2005] [Nix, Michael and Staton, Eric J. 2004] [Noneman, Steven R. and Smith, C. A. 2002] [Obermann and Williamson 1998] [Obermann and Williamson 2003] [Olds, John R. and Marcus, Leland 2002] [Parvathy and Jacob 2021] [Prasad 2022] [Prosser et al 2002] [Radhakrishnan et al 2023] [Redd 1985] [Reding and Svendsen 1990] [Rubenstein and Carter 2000] [Santhosh et al 2011] [Shahneh 2018] [Shaw et al 1997] [Shi et al 2025] [Shtessel et al 2000] [Shtessel, Yuri 1999] [Sivan and Pandian 2018] [Stanley et al 1994] [Takahashi et al 1997] [Taniguchi 2000] [Tariq et al 2026] [Tartabini, Paul V. et al 2000] [Tatry et al 1997] [Thomas, Dale et al 2002] [Tokudome et al 2009] [Tournes and Johnson 2001] [Tournes et al 1998] [urian 2015] [Wang et al 2020] [Wang et al 2022] [Wang et al 2022] [Wang et al 2022] [Wang et al 2023] [Wei et al 2019] [Wu and Zhang 2023] [Xu et al 2025] [Yang 2025] [Yang et al 2024] [Yap et al 2012] [Ye et al 2020] [Yu et al 2014] [Yue et al 2018] [Zagrai et al 2011] [Zapata 2011] [Zeno et al 2010] [Zhang et al 2019] [Zhang et al 2022] [Zhang et al 2025] [Zhang et al 2026] [Zhao et al 2020] [Zhao et al 2021] [Zhou et al 2025]

Military space, secrecy and space policy

The classification. Military space doctrine and policy, national security space programmes, dual-use space technology and the study of secrecy.

111 records. [Air Force Doctrine Center Hq Maxwell Afb Al 1998] [Air Research And Development Command 1959] [Albu 2022] [Anderson and Rothstein 1998] [Atkins et al 2008] [Bataille 2024] [Beavers 2021] [Bennett 2023] [Bo 1996] [Bowen 2018] [Brown 2020] [Buczkowski 2022] [Burke 2006] [Carter 1997] [Chapman 2021] [Chapman 2024] [Chekov 2025] [Chilcott 1990] [China’s Military Space Strategy: A Dialectical Materialism perspective 2019] [Chisholm 1984] [Cho 2018] [Cho et al 2021] [Choi 2023] [Connolly and Garcés 2025] [Corley 2005] [Costello 2004] [Daehnick 1995] [Department Of Defense Washington Dc 2011] [Dobrot 2000] [Dr. Syed Rizwan Haider Bukhari et al 2026] [Duffers Drift and Space Operations 2021] [Eriksson 2025] [Essay Military Space in 2004] [Ferguson and Davey 1985] [Fox 2000] [Gibney 2004] [Guimarães Furtado 2026] [Hall 2006] [Halperin 1984] [Hayden 2004] [Hoerber 2018] [Hunter 2019] [Ianni et al 2004] [Jelonek 1999] [Joint Chiefs Of Staff Washington Dc 2002] [Joint Chiefs Of Staff Washington Dc 2009] [Justice 2004] [Kabat 2010] [Kaspar 2000] [Kawane 2012] [Klein 2004] [Klimburg-Witjes 2021] [Krizay 2000] [Kwast 1997] [Langlois et al 2023] [Lee 1994] [Lee 1999] [Lee et al 2020] [Levy 1997] [Liao 2005] [Lloyd 1999] [Lutton 2009] [Lyons 2023] [Madura et al 1992] [Malinowska 2024] [Malinowska 2025] [Martin 2020] [Martinez 2016] [Mathieu and Pasco 2015] [McLean 2000] [Meisinger 2008] [Meredith 1985] [Michigan State Univ East Lansing 2004] [Mowthorpe 2002] [Muhammad Siddique 2025] [Muller and Welfens 2023] [Munsami 2014] [Newberry 1997] [Oikonomou 2012] [Oikonomou 2017] [Otani et al 2012] [Owen 1997] [Paolini 1988] [Parker and Goldizen 2005] [Peel 2008] [Peoples 2013] [Pollpeter 2016] [Pražák 2021] [Quintrall 1998] [Rajagopalan and Stroikos 2024] [Raymond 2003] [Relyea 1980] [Resnik 2006] [Secretary Of The Air Force Washington Dc 2001] [Shearer 1997] [Smith 1994] [Soroka 2020] [Soroka 2021] [Soroka and Danylenko 2024] [Steele 2009] [Stroikos 2013] [Sutton 1988] [Teehan 2007] [von Kries 1995] [Voûte 1986] [Wellman 1997] [Wulff 2012] [Yang 2021] [Young 2003] [Zaidi and Levis 2008] [Zielinski et al 1996]

Rendezvous, proximity operations and on-orbit servicing

What a manoeuvring orbiter can do near another. Rendezvous, proximity operations, inspection and on-orbit servicing.

103 records. [Apodaca et al 2025] [Barnhart and Rughani 2020] [Bennett] [Benninghoff et al 2014] [Bilimoria et al 2011] [Boge and Benninghoff 2013] [Cameron 2003] [Capra et al 2025] [Chi and Huo 2014] [Choi et al 2026] [Chouinard et al 2008] [Clark et al 2003] [D’Amico and Montenbruck 2006] [D’Souza et al 2007] [Da Fonseca et al 2017] [Daneshjou et al 2017] [Dankov and Mikhailov 1965] [Dellacamera et al 2000] [Design of Orbital Payload transfer Vehicle 2024] [Dethlefsen 2019] [Deutscher et al 1989] [Donatelli et al 1993] [Dong et al 2017] [Dong et al 2018] [Falcone et al 2026] [Fallahiarezoodar and Zhu 2025] [Federici et al 2021] [Flecklin 1991] [Gaias and Lovera 2021] [Gaias et al 2014] [Gao et al 2022] [Geller and Klein 2014] [Gershzohn et al 1990] [Goodman 2006] [Hastings 2006] [Hatty 2022] [Hines and Ulrich 2026] [Ho et al 2020] [Hovell and Ulrich 2021] [Howard 2010] [Howard et al 2008] [Ichimura and Ichikawa 2008] [Jifuku et al 2011] [Kim et al 2026] [Kleinau et al 1986] [Knight et al 2014] [Kumar et al 2004] [Lang et al 2025] [Larouche 2013] [Lee and Gallucci 2023] [Leonardi et al 2026] [Li and Zhang 2024] [Li et al 2014] [Li et al 2022] [Li et al 2023] [Li et al 2026] [Luu and Hastings 2022] [McCamish et al 2009] [McCoy 1988] [Medina et al 2017] [Michaelis and Luttmann 1997] [Ogundele 2021] [Okasha and Newman 2014] [Panag and Woollands 2025] [Peck 2007] [Ramón et al 2022] [Rivolta et al 2019] [Rodrigues et al 2022] [Rourke and Tsugawa 1991] [Sarton du Jonchay et al 2021] [Sarton du Jonchay et al 2022] [Schaub 2004] [Schulte et al 2020] [Sears and Ho 2018] [Shuster et al 2021] [Sorenson and Pinkley 2023] [Spencer and Lovell 2015] [Spencer et al 2016] [Stanfield and Bani Younes 2021] [Stephens et al 2011] [Sun 2016] [Sun and Huo 2014] [Sun et al 2023] [Swartwout 2007] [Swartwout 2009] [Toklu 2024] [Vasconcelos et al 2025] [Ventura et al 2026] [Ventura et al 2026] [Wang et al 2012] [Wang et al 2019] [Wei et al 2026] [Williams 2002] [Williams 2005] [Wilson and Schaub 2021] [Wilson et al 2022] [Wilson et al 2022] [Woffinden and Geller 2007] [Wu et al 2018] [Yao et al 2010] [Zhang 2025] [Zhang and Zhang 2014] [Zhang et al 2016]

Spacecraft propulsion and orbit transfer stages

The least interesting system. Spacecraft propulsion, reaction control, propellant management and gauging, and orbit transfer stages, chemical and electric.

102 records. [Air Force Research Lab Edwards Afb Ca 1999] [Alexander et al 2008] [Ambrose et al 2000] [Bahr and Disimile 1995] [Berger and Willner 1971] [Biryukov and Kurguzov 2020] [Bond et al 1989] [Boyce, Clay 2009] [Brody and Ellis 1990] [Buden and Garrison 1985] [Cake et al 1977] [Cassidy 1972] [Charhut and Ketchum 1986] [Chato 1998] [Chobotov and Purohit 1993] [Christenson, Rick L. et al 2003] [Colquitt 1969] [Cooper and Scheer 1988] [Cooper, L. P. 1985] [Crandall and Wirz 2022] [Curran and Haag 1992] [Damario and Vullo 1976] [Davis 1982] [Difilippo 1998] [Dudley et al 1992] [Duxbury and Paul 1976] [Dyakonov, Artem A. et al 2007] [Fedotov 2004] [Ferguson 2007] [Forrette 1964] [Gartrell 1983] [Gibson and Humphries 1985] [Green et al 1999] [Gunn 1991] [Hamlyn et al 1981] [Hartwig 2016] [Hearn 1979] [Mulkey and Dingertz] [Hoskins et al 2003] [Houseman and Lee 1972] [Houseman et al 1999] [Isopi 1979] [Jacks and Beisler 2003] [Jacks and Beisler 2003] [Jacobs and Castner 2007] [Johnson et al 2001] [Johnson, Theodore F. et al 2004] [Modeling and Simulation of] [Kana 1987] [Kana and Chu 1970] [Kaufman 1972] [Kawakatsu 2007] [Keesler 1974] [Kerslake and Gefert 2000] [Kunz 1980] [Lal and Raghunandan 2005] [Lal and Raghunandan 2007] [Lawyer 1972] [Leach and Szpakowski 1983] [Leomanni et al 2017] [Liu et al 2020] [Liu et al 2020] [MacConochie et al 1980] [Mailhe and Heister 2002] [McGuire, Melissa L. et al 2014] [McKim 2016] [Miller et al 2007] [Mitchell, Jack C. and Keeley, J. T. 1985] [Molitor et al 1967] [Molitor et al 1969] [Morino et al 2001] [Mu and Zhang 2014] [Nabity 2005] [Pearson et al 2006] [Pickens and Bossard 2010] [Polzin et al 2008] [Qi and Jia 2012] [Regnier and Hess 1978] [Rehder and Wurster 1979] [Rock et al 2006] [Saito et al 2026] [Saulsberry and McCartney 1993] [Scheel 1972] [Schoenman, L. 1982] [Schuster et al 1993] [Smith 1991] [Space shuttle orbital maneuvering 1975] [Taylor et al 1986] [Tupitsyn 2021] [Turchi 1985] [Uchida et al 2006] [Utsumi 2000] [VanDresar and Zimmerli 2014] [Vinogradov et al 2002] [Wang et al 2026] [Wu] [White, Molly E. and Hyatt, Andrew J. 2016] [Williams 2005] [Xu. Wei 2010] [Yao and Sands 2021] [Zimmerli, Gregory A. et al 2010] [Öz 2021]

Materials and charging in the orbital environment

What low orbit does to the vehicle’s surfaces. Atomic oxygen erosion, ultraviolet and particle damage to materials, contamination, and spacecraft charging and plasma interaction.

100 records. [Ahmad et al 2018] [Ahmed et al 1977] [Albyn and Finckenor 2006] [Allen, David and Schmidt, Robert 1992] [Alvarex 1999] [Armstrong and Colborn 1992] [Baird 1998] [Bakalyar 1977] [Banks et al 2004] [Banks 2011] [Banks and Rutledge 1989] [Bering and Ignatiev 1990] [Bhat 2009] [Blake 1981] [Blake 1992] [Blake and Cox 1988] [Blott et al 1997] [Bouquet and Koprowski 1982] [Briskman 2000] [Chen and Lee 2006] [Cho et al 1999] [Conger and Hastings 1995] [Connell 2000] [Cowling et al 1960] [David and Babel 1992] [deGroh et al 2001] [Degtjarev et al 2000] [Dever et al 1992] [Dever and deGroh 2002] [Dressler and Murad 1995] [Dworak et al 2006] [Plis et al] [Emmons 1964] [Evans and Kross 2000] [Felbeck 1995] [Fennell and Anderson 2008] [Ferguson et al 2015] [French and Hansen 1964] [Frooninckx and Sojka 1992] [Gabriel et al 1998] [Gabrielse et al 2022] [Garrett 1977] [Garrett and Rubin 1978] [Gates and Lewis 1994] [Gerver et al 1990] [Ginet 2005] [Grossman et al 2004] [Gubby and Evans 2002] [Ha Jo et al 2026] [Hase 2011] [Hastings 1995] [Henley 1986] [Imka et al 2014] [Jaeger 1999] [Jaworske 1999] [Karr 1976] [Katz et al 1981] [Katz et al 1984] [Kettle 2004] [Kimoto et al 2021] [Knott 1972] [Koons et al 1994] [Lai and Tautz 2006] [Lee and Chen 2000] [Miller and Banks 2018] [Minow et al 2008] [Minton 2008] [Miroshnichenko 1996] [NeergaardParker et al 2014] [Novikov et al 2006] [Pattee and Monroe 1966] [Paulmier et al 2011] [Pfitzer 1989] [Putz et al 2020] [Rea and Guida 2025] [Rea and Guida 2026] [Reddy 1995] [Rietmeijer and Blanford 1988] [Rutledge 1999] [Shen et al 2025] [Skriabysheva 2005] [Snyder 1999] [Sowers 1962] [Spacecraft Charging During Eclipse 1980] [Spady et al 1995] [Stanley and Ryan 1968] [Synder and Cross 1960] [Synowicki et al 1995] [Tagawa et al 2009] [Thiemann and Schunk 1990] [Thomas 1983] [Tidwell 1970] [Vaughn et al 1994] [Whitaker and Kamenetzky 1993] [Whiteside et al 1994] [Williams and Levandier 1999] [Xapsos 2014] [Yang et al 2025] [Kuznetsova et al 2024] [Zimcik et al 1985]

Spaceplanes and winged orbital vehicles

The vehicle’s class. Winged orbital and suborbital spaceplanes other than the X-37, among them Hermes, HOPE, the Orbital Space Plane, Skylon, Dream Chaser and the National Aero-Space Plane.

46 records. [Abe et al 2005] [Ashikhmina and Prosuntsov 2021] [Ashikhmina et al 2021] [Bae et al 2022] [Betin 1991] [Brumley and Perich 2022] [Campbell 1991] [Chavagnac et al 2013] [Daidzic 2016] [Dufour et al 2015] [Dumbacher 2003] [Dumbacher 2003] [Elisov et al 2018] [Ford 2003] [Gibney 2015] [Hasegawa and Kanda 2019] [Ito and Nomoto 1990] [Kato 1991] [Kolga and Rundau 2024] [Kondrashov 2023] [Koothan Venkateswaran et al 2025] [Kudo and Kato 1991] [Launius 2013] [Le Goff and Moreau 2013] [MacLeod 2026] [MacLeod and Begent 2025] [Maita 1989] [McKenzie 2003] [McNelis, Nancy B. et al 1995] [Murcia-Piñeros et al 2026] [Nebylov and Nebylov 2011] [Nuhija 2021] [Redding 1984] [Ricciardi et al 2019] [Rogers et al 2004] [Russo et al 2021] [Schweikart and Hallion 1998] [Stapleton et al 1997] [The graphic Skylon reusable 2011] [Tsuchiya and Suzuki 1998] [Wang and Zhang 2018] [Yamada and Suzuki 2016] [Yan and von der Dunk 1992] [Ye 2023] [Yokoyama et al 2001] [Zhang et al 2024]

Approach, landing and terminal area energy management

The autonomous landing. Approach and landing guidance, terminal area energy management and automatic landing of winged vehicles and aircraft.

44 records. [Ahmed and Wyatt 2024] [AL-Bakri and Kluever 2017] [Bedrov et al 1965] [Berwin M Kock and Fitzhugh L Fulton, Jr. 1970] [Bossi, J. A. et al 1991] [Burchett 2004] [Burchett, Bradley 2003] [Cetin et al 2010] [Extension of a portable tactical instrument approach and landing system 1972] [Fang et al 2019] [Fang et al 2026] [Grantham, Katie 2003] [Hornbuckle 2015] [Jiang and Ordóñez 2009] [Jiang and Yang 2014] [Junaid R and Beebi M 2015] [Kaynak 2010] [Koester and Vaillancourt 1992] [Korn et al 2009] [Lee and Park 2025] [Lowrance and Smith 1996] [Lunghi et al 2015] [Maiuzzo 1970] [Menon et al 2009] [Miso et al 1999] [Morio et al 2007] [Morio et al 2010] [Mu et al 2016] [Ni et al 2023] [Numerical Optimization on Approach and Landing for Reusable Launch Vehicle 2016] [Pervan and Parkinson 1997] [Pogorelov 2008] [Pogorelov 2009] [Poritzky 1971] [Promising navigation, landing and reusable orbital spaceships safety monitoring systems 2019] [Qiao and Chen 2018] [Roy and Davison 1986] [Sai-fei et al 2016] [Satkunanathan and Murphy 1998] [Su and Wang 2015] [Tripathi and Padhi 2016] [Wang et al 2024] [Yang et al 2026] [Zhou et al 2013]

The X-37, the X-40 and the Space Maneuver Vehicle

The vehicle’s own record. Titles that name the X-37, the X-40, the orbital test vehicle or the Space Maneuver Vehicle that preceded them. The cluster is set out record by record under The Source Base, because its thinness is the finding this article is about.

33 records. [Chai et al 2017] [Chai et al 2019] [Chai et al 2019] [Chai et al 2020] [Chaudhary, Ashwani et al 2001] [Childers, Dave et al 2001] [Davis 2002] [Dumbacher, Daniel L. 2004] [Ghoshroy 2015] [Grantz 2011] [Halberg et al 2016] [Hudson and Stephens 2006] [Jacobson, David 2004] [Jacobson, David 2004] [Jameson 2001] [Janicik 1999] [Karasopoulos et al 1998] [Kilgore and Kilgore 1997] [Manley, David J. et al 2000] [Mitchell 2004] [Niu et al 2019] [Pienkowski et al 2003] [Ren et al 2017] [Schwabacher, Mark et al 2002] [Song et al 2024] [Sushnigdha 2021] [Taylor, Terry L. 2004] [Turner, Susan and Spanyer, Karen 2005] [Valentine, P. G. et al 2004] [Verderame et al 1999] [Wang et al 2007] [Wang et al 2018] [Whitmore, Stephen A. et al 2004]

Eclipse, sunlight and orbital lighting geometry

The geometry the endurance argument begins from. Eclipse duration, shadow boundaries and orbital lighting.

21 records. [Adhya et al 2004] [Austin 2024] [Bounds for the Solar Scatter Angle Observed from Earth Orbit 1975] [Capderou 2014] [Chao 1980] [Fitzgerald 2021] [Fixler 1964] [Garzón et al 2022] [Georgescu et al 2011] [Graphical method for prediction of time in sunlight for a circular orbit 1962] [Kerslake and Scheiman 2005] [Kostolansky 2002] [Link 1969] [Lundberg 2000] [Nugnes and Colombo 2023] [Orbit Raising with Low-Thrust Tangential Acceleration in Presence of Earth Shadow 1998] [Sincarsin and Hughes 1982] [Srivastava et al 2015] [Suresha and Gupta 1999] [Williams 1970] [Zhang et al 2019]

Where the Framing Breaks Down

The Load Is Bounded and Not Known

Everything in the power and thermal sections is an upper bound. The article computes what the array could generate and what the radiator could reject, and both are ceilings. The actual load could be a tenth of either, and no public data distinguishes the cases. A bracket between 540 and 1,623 watts is a wide bracket and the article should not be read as having measured a kilowatt.

The Drag Area Is Assumed

The ballistic coefficient of 623.75 kilograms per square metre rests on an assumed drag area of 8 square metres and on the launch mass of 4,990 kilograms standing for the mass on orbit. The drag area is not published, and the mass on orbit is not either. The makeup requirement in the drag section is linear in the drag area, so nearly doubling the area roughly doubles every velocity increment, and the qualitative conclusion survives that. The altitude floor does not survive it unchanged, and a reader should treat 245.4 kilometres as an order rather than a number.

The Propellant Load Is a Guess and It Propagates Widely

The 500 kilogram propellant assumption appears in the altitude floor, in the aerobraking leverage ratio and in the plane change comparison, and no input in the article is less defensible. It was chosen as a round tenth of launch mass. Every ratio that divides by 310.6 metres per second should be read as scaling inversely with whatever the true load is. The aerobraking conclusion is robust to it, because a factor of 7.88 would survive a doubling of the propellant load and still be decisive. The altitude floor is not robust to it.

The Aerobraking Reconstruction Is Not a Reconstruction

The article computes what aerobraking could have done for a vehicle of this ballistic coefficient at various perigees. It does not know what perigee was flown, how many passes were made, or what fraction of the apogee reduction was aerodynamic. The 100 kilometre figure is where the calendar closes, not where the vehicle went.

The Solar Cycle Observation Is an Observation and Not a Finding About Intent

A launch date is set by range availability, payload readiness, vehicle availability and policy, and this article has no evidence that the drag environment entered the decision. The arithmetic showing that the record mission began in the quietest phase of the solar cycle is sound. Any inference from it about why the mission was flown when it was is not.

The Comparison With the Two Preceding Articles Is Neat and Should Be Distrusted for It

Three consecutive articles have found a demonstration tilted in a computable direction, in two directions. A pattern found three times in a series written by one author using one method is evidence about the method as much as about the aircraft. It is recorded here so that the closing article can test it against the vehicles that have not yet been examined, rather than treated as established.

The Article Assumes the Vehicle Is What It Appears to Be

Every calculation here treats the X-37B as a five-tonne winged vehicle with a small array, a hypergolic propulsion system and a payload bay of published dimensions. If any of those is wrong, and a classified programme is entitled to have published a misleading specification, then the calculations are internally consistent and externally worthless. There is no way to test that from outside, and the article states it rather than assuming its way past it.

The Source Base

The Vehicle’s Own Cluster Is Thin, Which Is the Fifth Instance and the Fifth Reason

Twenty research records in this survey carry the X-37 designation or the words orbital test vehicle in their titles. Twelve are space agency reports dated between 2000 and 2006. Four are conference and research papers, three from the development years, on aerobraking and aerodynamic plane change, on aerodynamic orbital transfer and on the vehicle’s place in space control, and one from 2011 on the orbital test vehicle and its derivatives. The remaining four date from 2015 or later and are outside work, an essay on the vehicle and the weaponisation of space, a concept for a space station ambulance built on the vehicle’s technology, and two analyses of the vehicle’s infrared observability and entry flow field written by people with no access to the programme.

The space agency’s own reports on the vehicle stop in 2006, two years after the transfer to the defence research agency, and no title in the survey describes a flown mission. The vehicle has operated for fifteen years, and the only later engineering paper on the vehicle itself is titled for the vehicle and its derivatives rather than for any flight. The cluster also holds thirteen titles that do not name the X-37, five on the Space Maneuver Vehicle and the X-40A from 1997 to 2002 and eight studies since 2007 that take the Space Maneuver Vehicle as the object of trajectory optimisation, guidance or mission planning.

Article Vehicle Why its cluster is thin
the X-33 article X-33 Cancelled. Sixty records, every one predating 2002
the X-34 article X-34 Cancelled. The same shape, and two instances made it a pattern
the X-35 article X-35 It won, and contractor demonstrators flown for a source selection do not produce reports
the X-36 article X-36 It produced a technique rather than a vehicle, so its contribution is filed under the names of its methods
the X-37 article X-37 It became classified. It did not stop existing and it did not stop working. It stopped being publishable

The five reasons are entirely distinct and the conclusion is not that thin clusters mean failure. The X-37 is the most operationally successful vehicle in the last ten articles of this series and has the thinnest trace of any of them. The documentary record measures the institution and its circumstances rather than the aircraft.

The Period Half and the Contemporary Half, Counted and Not Only Divided

The research survey holds 4,827 research records drawn from Crossref, the NASA Technical Reports Server and the Defense Technical Information Center, of which 1,037 are report primaries, being 21.5 percent, by the identifier rule set out under The Definition of Primary. The median publication year is 2007.

Reporting a fraction alone is misleading, because adding a contemporary survey lowers the period fraction while leaving the period count untouched. Both are given.

Half Count Share of dated
Period, through 2011 2,674 56.4 percent
Contemporary, 2012 onward 2,067 43.6 percent
Undated 86  
Total research records 4,827  

The period count is 2,674 and the contemporary count is 2,067. Both are given because a contemporary survey lowers the period share while leaving the period count untouched, and reporting the share alone reads as a regression when it is only the contemporary survey being added.

A date is not a measure of primacy and this article reports both. The technical report servers hold original research reports almost exclusively, while a journal index holds originals, reviews and comment together, so the report share is the closest available proxy for how much of the base is primary.

Measure Count Share
Technical reports, all eras 1,037 21.5 percent
Technical reports at or before 2011 867 18.0 percent
Journal and conference records 3,790 78.5 percent

A further 140 reference works are listed below, and they carry the relations that no journal article states because every textbook does. The count is the number of entries in that list.

What the Record Does Not Contain

No mass breakdown. No power budget. No propellant load. No thermal design. No description of any payload beyond the roughly ten experiments announced by name. No flight data of any kind from any of the eight missions. The article computes bounds precisely because none of these exists.

The Reference Works

The Definition of Primary

Primacy is a property of the document, and this survey derives it from the identifier. A record is a report primary when its address is on the NASA Technical Reports Server or at the Defense Technical Information Center, or it carries a digital object identifier under the 10.21236 prefix, which Crossref registers for Defense Technical Information Center reports. By that rule 1,037 of the 4,827 research records are report primaries, being 21.5 percent. The space agency’s reports on the vehicle are report primaries under that rule, and so are the agency’s reports on the Shuttle orbiter and on aeroassisted transfer. The rule does not reach first-hand journal and conference papers, such as the satellite drag analyses of the late 1950s and the conference papers on the Space Maneuver Vehicle, so 21.5 percent is a lower bound on how much of the survey is first-hand.

Primary sources for this article are the space agency reports published while the vehicle was being designed, the Defense Technical Information Center holdings from the same window, and the journal and conference papers contemporary with each relation the article uses. The programme’s own operational record is not available at any level of primacy, so the primary base is a base for the physics rather than for the vehicle.

A date and a primacy are different measurements and this article reports both, because a cutoff separates period from contemporary and says nothing whatever about whether a record is an original report or a commentary on one. The technical report servers hold originals almost exclusively, so their share is the closest available proxy, and it is given in the table above beside the date split rather than instead of it.

Thin Subjects

The subjects a technical argument rests on are not the subjects its vocabulary names, and the gap between the two is where a literature search fails. This article displays relations drawn from the second zonal harmonic, the solar aspect angle, the square-cube law and the energy state approximation. Outside this section the article’s prose names the first and third where it uses them and never names the other two. A search built from what an article says will not find the literature the article depends on.

Measured against the list of subjects the arguments actually use, eighteen of thirty-seven are thin or absent in the source base assembled here. A subject counts as thin when fewer than twelve dated records match its search terms or either half holds fewer than five. Thirteen are named below, because a bare count invites the reader to assume the worst explanation. The other five, orbital decay, plane change, bank angle modulation, radiative equilibrium wall temperature and reusable tile protection, meet the same count and are not classified here.

A subject can be thin for three reasons and a count cannot tell them apart. Naming which applies is the whole of the work.

The heading is wrong, which is the commonest kind and the only curable one. The field does not say crossrange, it says lateral range and footprint. It does not say equilibrium glide, it says gliding entry and cites Eggers and Allen. It did not say beta angle in 1968, it said solar aspect angle and sun incidence. Counted in each field’s own words rather than in this article’s, equilibrium glide stands at eighteen records, crossrange at fourteen, which takes it off the thin list, and vehicle scaling at eight. The records are present in the literature under the field’s words, and a question put in the article’s words does not reach them.

That is worth stating plainly, because it applies to the instrument as much as to the search. A count of how well a subject is covered is itself a search, and it undercounts for exactly the same reason. A thin result is a claim about the question before it is a claim about the field.

The knowledge is settled and stopped generating papers, which is not curable and must not be padded. The vis-viva relation stands at zero records, the rocket equation at one and Kepler’s third law at three. These are not gaps. They are relations that appear in every astrodynamics textbook and in no journal article, because nobody has published on them since the seventeenth and nineteenth centuries respectively. The reference works section carries them and that is the correct home.

The work was never done, which is rare and has to be argued and never assumed. Nothing in this article’s subject list falls into it.

What remains thin, and which kind each is.

Subject Period Contemporary Why
Specific orbital energy 0 0 Settled. Every astrodynamics textbook, no journal article
The rocket equation 0 1 Settled. Same, and the X-34 article found the same
Kepler and the orbital period 1 2 Settled, and the relation is from 1619
Energy height 1 0 Settled. The method is named after a 1954 paper and is textbook thereafter
The beta angle, period half 0 1 Thin heading, and the period’s own words do not find it either. The period documented the same geometry inside thermal design reports that name neither the angle nor its modern synonyms
Aerobraking corridor control 4 2 Thin heading. The subject is covered by 565 dated records whose title or venue names aerobraking, aerocapture or aeroassist
Stagnation heating, contemporary half 50 0 Thin heading. Modern work computes the same quantity and does not cite the correlations by name
Manoeuvre detection, period half 0 19 Genuinely modern. The capability to detect a manoeuvre from the ground is recent
Debris disposal, period half 4 64 Genuinely modern. Disposal became an obligation in this century, having been a courtesy before it
Albedo and Earth infrared, contemporary half 12 2 Not classified. Albedo also names the albedo of Mars and the gamma-ray albedo of the Earth, whose records are excluded, and the two that remain do not show which reason applies

The vehicle’s own subject is thin by this count, and only just, with seventeen period and four contemporary records whose title or venue names the X-37 or its programme, and that is why the section above sets the records out one by one. The contemporary half falls one short of the threshold, and the four contemporary records are outside work that names the vehicle, none of them reporting a flight. Every other subject here has an ordinary explanation. The vehicle’s own is the only one whose cause is that somebody decided the work should not be published.

What the Survey Admits

A record is admitted only when a person reading its title finds it on this article’s subject. Its 4,827 records come from NASA’s Technical Reports Server, the Defense Technical Information Center and the Crossref index of the journal literature. Many words this subject depends on also name something else, and a record that shares only such a word, or whose only link to the vehicle is a distant application of a shared technique, is excluded. An orbiter also names the planetary and lunar missions and their navigation, gravity science and instruments, an orbital also names a molecular or electronic orbital, and an orbit also names the eye socket. A radiator or a heat pipe also names the cooling of buildings, vehicles, processors and data centres, a battery life cycle also names the recycling and environmental assessment of a battery, and a solar cell also names the device physics of terrestrial photovoltaics and the arrays of airships and uncrewed aircraft. Stagnation flow also names the low-speed flows of jets, plates and stretching sheets, radiative equilibrium also names radiation in gases and enclosures, and an eclipse also names astronomy, public outreach and a software platform. The ionosphere and the magnetosphere share the altitudes but not the neutral density that sets drag, a re-entry vehicle also names the warhead of a ballistic missile whose radar tracking is a defence subject, and autonomous landing also names multirotor aircraft settling on moving platforms. Communication and navigation constellations, terrestrial wireless power transfer, dual-use technology outside space, and secrecy in fiction, foreign policy and public relations are excluded on the same ground. Correction, erratum and retraction notices, withdrawal notices, figure and supplementary-material records, peer-review reports and journal front matter such as subject indexes are excluded as well, because a survey counts research works and those are parts of works or editorial events rather than works. A document deposited twice is counted once. Book reviews, prefaces and forewords to collections, patent abstracts, the abstracts that abstract journals and the abstract sections of other journals reprint, and news items, signed or unsigned, are excluded on the same ground, and so is a news writer’s reply to a letter about a news story, which belongs to the news item. A signed comment on a paper, a discussion of a paper, the author’s reply to either and a signed letter on a research subject are research works, because each argues about a result, and they are admitted when their subject is this article’s.

Some records of doubtful relevance are kept. The cycle life and state of health of electric vehicle and grid storage batteries, laboratory studies of loop and pulsating heat pipes that name no application, control of air-breathing hypersonic vehicles, and the subsystems of the Shuttle orbiter that an uncrewed vehicle shares each share a relation, a technique or a hardware lineage with this subject, so each is kept and a reader may weigh it accordingly.

No residual cluster is needed. Every admitted record belongs to one of the 24 named clusters, each named for what its titles are, so no cluster holds records admitted only because they fit nowhere else.

Every research title has been read for relevance, so the off-topic share that remains is a matter of reading judgement. A reading of titles cannot show that a work is relevant in substance, so this is a statement about titles only.

Epistemic State

Historical Fact

The programme began at the space agency in 1999 with Boeing as contractor, transferred to the Defense Advanced Research Projects Agency on 13 September 2004, and the Air Force announced its own derivative on 17 November 2006. The X-40A was an 80 percent scale drop-test vehicle and the X-37 is a 120 percent scaled derivative of it. The Approach and Landing Test Vehicle first flew on 7 April 2006 and its first free flight ended in a runway excursion. Eight orbital missions have launched since 22 April 2010, of which seven have landed, totalling 4,208.65 days. The sixth mission lasted 908.88 days. The seventh flew a highly elliptical orbit catalogued at 336 by 37,895 kilometres and an inclination of 59.27 degrees, and the Space Force announced in October 2024 that it would use aerobraking to change that orbit and dispose of its service module. The published dimensions are 8.92 metres long, 4.55 metres in span, 2.90 metres high, with a payload bay of 2.1 by 1.2 metres and a launch mass of 4,990 kilograms. Those dimensions, the launch mass and the mission times rest on the encyclopaedic specification, which compiles Air Force, Boeing and press figures, and the orbits rest on a single catalogue [General Catalog of Artificial Space Objects].

Engineering Analysis

Every quantitative result in this article is computed from those published figures and from standard relations. The orbital period, circular speed, eclipse fraction, full-sun beta threshold, nodal precession, beta cycle and orbit count follow from the published altitude and inclination alone. The scaling exponents and the duty cycle follow from published dimensions, masses and dates, and involve no model whatever. The array and radiator bounds follow from the published bay dimensions. The drag figures follow from a piecewise exponential atmosphere at nominal solar activity. The aerobraking figures follow from the published orbit. The identity showing that entry heading change is independent of mass, area and atmosphere is exact within the equilibrium glide assumption, and agrees with an integration that retains the term it claims cancels.

Inference

The node and beta cycles are short against the mission, at 63.31 and 53.95 days against 908.88, and from that the article infers that the eclipse average describes what the mission experienced rather than a modelling convenience. That the square-cube penalty rather than a design choice explains the payload fraction is an inference from the measured mass exponent of 1.924, and other explanations are available.

The inference that endurance rather than propulsion is the binding constraint comes from the computed drag budget being small at the altitudes flown. That heat rejection binds more tightly than power generation is an inference from two bounds whose ranges overlap at the low end. A walk-down calculation using an assumed ballistic coefficient is the basis for inferring that the aerobraking campaign required a perigee near 100 kilometres. That the programme’s documentary silence is caused by classification rather than by inactivity is an inference from the pattern of the space agency’s twelve reports on the vehicle, which stop in 2006, two years after the transfer to the defence research agency.

What the Record Does Not Settle

What the vehicle carries, what it does, and why the missions run as long as they do. Also the actual electrical load, propellant load and drag area, the perigee flown during the aerobraking campaign, the fraction of the seventh mission’s apogee reduction that was aerodynamic, and whether the published specification is complete. The article is a set of bounds and identities consistent with the public record, and a classified programme is entitled to have a public record that does not fully describe it.

Out of Scope

The detailed design of the Approach and Landing Test Vehicle’s flight control system. The Atlas V, Falcon 9 and Falcon Heavy launch vehicles and their performance to the orbits flown. The legal and treaty questions raised by a manoeuvrable military vehicle in orbit, which are a substantial literature in their own right and are surveyed here without being analysed. The Chinese and other reusable spaceplane programmes that have flown since 2020, which deserve separate treatment. The economics of reusable launch, treated in the X-33 and X-34 articles. The detailed chemistry of TUFROC and its successors.

Conclusion

The X-37B answered a question about endurance. Endurance in orbit turns out to be cheap once the power loop is sized for it. A 908-day mission is 14,140 charge and discharge cycles, which on the cycle-life law assumed here a battery cycled to something between 38 and 50 percent depth of discharge will survive, at a mass penalty of roughly fifteen kilograms for each kilowatt of continuous load. The drag makeup over the same mission is between 23 and 152 kilograms of propellant at the altitudes flown. That neither number is large for a five-tonne vehicle is the finding. The obstacle to a very long orbital mission was never physics. It was the willingness to build a vehicle that had nothing else to do.

The vehicle’s second answer concerns manoeuvre, and it came from the atmosphere rather than the engine. Lowering perigee for twenty-four metres per second bought nearly two and a half kilometres per second of apogee reduction, a leverage of 103 to one, and did it at a fifth of the heat flux of a full entry. A vehicle whose entire propulsive budget is 311 metres per second performed a 2,449 metre per second manoeuvre, and the only reason it could is that it has a thermal protection system and therefore may touch the atmosphere without consequence. Reusability bought manoeuvrability, an argument not usually made for it.

Two smaller results deserve carrying forward because neither needed a model. Measuring the exponent that relates this vehicle to the Shuttle orbiter puts mass at length to the 1.924 against 3 for geometric similarity, so a similar orbiter shrunk to 8.92 metres would mass 1,072 kilograms and this one masses 4,990. The small vehicle keeps the airframe and loses the room, so the payload fraction is 4.55 percent and needs no apology. And the operational claim is not the longest mission but the 77.46 percent duty cycle across the 5,433 days from first launch to seventh landing. Two airframes held an X-37B in orbit for three quarters of fifteen years, and the record mission conceals that turnaround.

The third answer is about the record itself, and it is uncomfortable. No vehicle in the last ten articles of this series has been more successful, and none has left a thinner documentary trace. Twenty titles in a survey of 4,827 records, none describing a flown mission, and the space agency’s reports on the vehicle stop in 2006 while the vehicle went on to fly orbital missions for fifteen years from 2010. Four previous articles found a thin cluster for four different reasons, all of which were forms of the programme ending. This one is thin because the programme succeeded and was classified.

The documentary trace measures the institution rather than the aircraft, and an outside analyst armed with published dimensions, public orbital elements and a textbook can recover the vehicle’s scale, its power budget, its endurance mechanism and the arithmetic of its most novel manoeuvre. What that analyst cannot recover is the only thing the programme was built to do, and the gap fairly summarises what classification achieves and what it costs.

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