Boeing X-37

The Boeing X-37, also known as the Orbital Test Vehicle (OTV), is a reusable robotic spacecraft. It is boosted into space by a launch vehicle, re-enters Earth's atmosphere, and lands as a spaceplane. The X-37 is operated by the Department of the Air Force Rapid Capabilities Office, in collaboration with the United States Space Force,<ref name=7th_X-37B_mission>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> for orbital spaceflight missions intended to demonstrate reusable space technologies. It is a 120-percent-scaled derivative of the earlier Boeing X-40. The X-37 began as a NASA project in 1999, before being transferred to the United States Department of Defense in 2004. Until 2019, the program was managed by Air Force Space Command.<ref name="Pentagon-X37B-20200818">Template:Cite news</ref>

An X-37 first flew during a drop test in 2006; its first orbital mission was launched in April 2010 on an Atlas V rocket, and returned to Earth in December 2010. Subsequent flights gradually extended the mission duration, reaching Template:Time interval in orbit for the fifth mission, the first to launch on a Falcon 9 rocket. The sixth mission launched on an Atlas V on 17 May 2020 and concluded on 12 November 2022, reaching 908 days in orbit.<ref name="ussf-20221112">Template:Cite press release</ref> The seventh mission launched on 28 December 2023 on a Falcon Heavy rocket, entering a highly elliptical high Earth orbit, landing in March 2025 after 434 days in orbit.<ref name="arstech-heavy">Template:Cite news</ref><ref name=":0">Template:Cite tweet</ref>

Development

Origins

File:X-37 spacecraft, artist's rendition.jpeg

An artist's rendering of the X-37 spacecraft in 1999

In 1999, NASA selected Boeing Integrated Defense Systems to design and develop an orbital vehicle, built by the California branch of Boeing Phantom Works. Over four years, $192 million was spent on the project, with NASA contributing $109 million, the U.S. Air Force $16 million, and Boeing $67 million. In late 2002, a new $301 million contract was awarded to Boeing as part of NASA's Space Launch Initiative framework.<ref name="MSFC_X-37_Tech_Demonstrator">{{#invoke:citation/CS1|citation |CitationClass=web }} Template:PD-notice</ref>

The aerodynamic design of the X-37 was derived from the larger Space Shuttle orbiter, hence the X-37 has a similar lift-to-drag ratio, and a lower cross range at higher altitudes and Mach numbers compared to DARPA's Hypersonic Technology Vehicle.<ref name="AFRoundtable_20100420">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> An early requirement for the spacecraft called for a total mission delta-v of Template:Convert for orbital maneuvers.<ref name="sfnow20100402">Template:Cite news</ref> An early goal for the program was for the X-37 to rendezvous with satellites and perform repairs.<ref name="nasapr19990714">Template:Cite press release Template:PD-notice</ref> The X-37 was originally designed to be carried into orbit in the cargo bay of the Space Shuttle, but underwent redesign for launch on a Delta IV or comparable rocket after it was determined that a shuttle flight would be uneconomical.Template:Sfn

The X-37 was transferred from NASA to the Defense Advanced Research Projects Agency (DARPA) on 13 September 2004.<ref name="Space20040915">Template:Cite news</ref> Thereafter, the program became a classified project because of its military applications. DARPA promoted the X-37 as part of the independent space policy that the United States Department of Defense has pursued since the 1986 Challenger disaster.

Glide testing

File:Scaled-wk-070711-08-16.jpg

The Scaled Composites White Knight was used to launch the X-37A on glide tests (2007).

The X-37A vehicle that was used as an atmospheric drop test glider had no propulsion system. Instead of an operational vehicle's payload bay doors, it had an enclosed and reinforced upper fuselage structure to allow it to be mated with a mothership. In September 2004, DARPA announced that for its initial atmospheric drop tests the X-37A would be launched from the Scaled Composites White Knight, a high-altitude research aircraft.<ref name="nbcnews20040916">Template:Cite news</ref>

On 21 June 2005, the X-37A completed a captive-carry flight underneath the White Knight from Mojave Spaceport in Mojave, California.<ref name="CNN_23_June_2005">Template:Cite news</ref><ref name="designation-systems"/> Through the second half of 2005, the X-37A underwent structural upgrades, including the reinforcement of its nose wheel supports. The X-37A's public debut for its first free flight, scheduled for 10 March 2006, was canceled due to an Arctic storm.<ref name="mojave">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The next flight attempt, on 15 March 2006, was canceled due to high winds.<ref name="mojave"/>

On 24 March 2006, the X-37A flew again but a datalink failure prevented a free flight and the vehicle returned to the ground still attached to its White Knight carrier aircraft. On 7 April 2006, the X-37A made its first free glide flight. During landing, the vehicle overran the runway and sustained minor damage.<ref name="Space20060407">Template:Cite news</ref> Following the vehicle's extended downtime for repairs, the program moved from Mojave to Air Force Plant 42 in Palmdale, California, for the remainder of the flight test program. White Knight continued to be based at Mojave, though it was ferried to Plant 42 when test flights were scheduled. Five additional flights were thought to have been performed,<ref name="WNflights" group="N">Source of flights: mission markings posted on side of White Knight aircraft</ref> two of which resulted in X-37 releases with successful landings. These two free flights occurred on 18 August 2006 and 26 September 2006.<ref name="Youtube20100422">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

X-37B Orbital Test Vehicle

On 17 November 2006, the U.S. Air Force announced that it would develop its own variant of NASA's X-37A. The Air Force version was designated the X-37B Orbital Test Vehicle (OTV). The OTV program was built on earlier industry and government efforts by DARPA, NASA, and the Air Force under the leadership of the Air Force Rapid Capabilities Office in partnership with NASA and the Air Force Research Laboratory. Boeing was the prime contractor for the OTV program.<ref name="sfnow20100402"/><ref name="X-37B_space.com">Template:Cite news</ref><ref name=spaceplane_to_orbit/> The X-37B was designed to remain in orbit for up to 270 days at a time.<ref name="sfn_feb2010">Template:Cite news</ref> The Secretary of the Air Force stated that the OTV program would focus on "risk reduction, experimentation, and operational concept development for reusable space vehicle technologies, in support of long-term developmental space objectives".<ref name=X-37B_space.com/>

The X-37B was originally scheduled for launch in the payload bay of the Space Shuttle, but after the Space Shuttle Columbia disaster, it was transferred to a Delta II 7920. The X-37B was subsequently transferred to a shrouded configuration on the Atlas V rocket, due to concerns over the unshrouded spacecraft's aerodynamic properties during launch.<ref name="GSP">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Following their missions, X-37B spacecraft primarily land on a runway at Vandenberg Air Force Base, California, with Edwards Air Force Base as a secondary site.<ref name="avweek20080803">Template:Cite news</ref> In 2010, manufacturing work began on the second X-37B,<ref name="AW_2nd_X-37B_prepared">Template:Cite newsTemplate:Dead link</ref> which conducted its maiden mission in March 2011.<ref name="sfnow20110305" />

On 8 October 2014, NASA confirmed that X-37B vehicles would be housed at Kennedy Space Center in Orbiter Processing Facilities (OPF) 1 and 2, hangars previously occupied by the Space Shuttle. Boeing had said the space planes would use OPF-1 in January 2014, and the Air Force had previously said it was considering consolidating X-37B operations, housed at Vandenberg Air Force Base in California, nearer to their launch site at Cape Canaveral. NASA also stated that the program had completed tests to determine whether the X-37B, one-fourth the size of the Space Shuttle, could land on the former Shuttle runways.<ref name="floridatoday20141008"/> NASA furthermore stated that renovations of the two hangars would be completed by the end of 2014; the main doors of OPF-1 were marked with the message "Home of the X-37B" by this point.<ref name="floridatoday20141008">Template:Cite news</ref>

Speculation regarding purpose

Most of the activities of the X-37B project are secret. The official Air Force statement is that the project is "an experimental test program to demonstrate technologies for a reliable, reusable, uncrewed space test platform for the U.S. Air Force".<ref name="USAF_factsh"/> The primary objectives of the X-37B are twofold: reusable spacecraft technology and operating experiments, which can be returned to Earth.<ref name="USAF_factsh"/> The Air Force states that this includes testing avionics, flight systems, guidance and navigation, thermal protection, insulation, propulsion, and re-entry systems.<ref name="Smithsonian2015">Template:Cite news</ref>

In May 2010, Tom Burghardt speculated on Space Daily that the X-37B could be used as a spy satellite or to deliver weapons from space. The Pentagon subsequently denied claims that the X-37B's test missions supported the development of space-based weapons.<ref>Template:Cite news</ref> In January 2012, allegations were made that the X-37B was being used to spy on China's Tiangong-1 space station module.<ref name="register20120106">Template:Cite news</ref> Former U.S. Air Force orbital analyst Brian Weeden later rejected this claim, emphasizing that the different orbits of the two spacecraft precluded any practical surveillance flybys.<ref name="ibtimes20120109">Template:Cite news</ref>

In October 2014, The Guardian reported the claims of security experts that the X-37B was being used "to test reconnaissance and spy sensors, particularly how they hold up against radiation and other hazards of orbit".<ref name="guardian20141027">Template:Cite news</ref> In November 2016, the International Business Times speculated that the U.S. government was testing a version of the EmDrive electromagnetic microwave thruster on the fourth flight of the X-37B.<ref name="ibtimes20161107">Template:Cite news</ref> In 2009, an EmDrive technology transfer contract with Boeing was undertaken via a State Department TAA and a UK export license, approved by the UK Ministry of Defence.<ref name="Shawyer2015">Template:Cite journal</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Boeing has since stated that it is no longer pursuing this area of research.<ref>Template:Cite news</ref> The U.S. Air Force has stated that the X-37B is testing a Hall-effect thruster system for Aerojet Rocketdyne.<ref name="sfn20150427" />

In July 2019, former United States Secretary of the Air Force Heather Wilson explained that when an X-37B was in an elliptic orbit it could, at perigee, use the thin atmosphere to make an orbit change preventing some observers from discovering the new orbit for a while, permitting secret activities.<ref name=military-20190723>Template:Cite news</ref>

Processing

File:X-37B OTV4 landed at Kennedy Space Center (170507-O-FH989-001).jpg

X-37B 2 sits on the Shuttle Landing Facility after the OTV-4 mission, with ground crew wearing protective suits.

Processing for the X-37 is carried out inside Bays 1 and 2 of the Orbiter Processing Facility (OPF) at Kennedy Space Center in Florida, where the vehicle is loaded with its payload. The X-37 is then placed inside a fairing along with its stage adapter and transported to the launch site. Previous launch sites have included SLC-41 and Kennedy Space Center LC-39A.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Landing is at one of three sites across the US: the Shuttle Landing Facility at Kennedy Space Center, Vandenberg Space Force Base, or Edwards Air Force Base. To return to Kennedy Space Center, the X-37 is placed into a payload canister and loaded into a Boeing C-17 cargo plane. Once at Kennedy, the X-37 is unloaded and towed to the OPF, where it is prepared for its next flight. Technicians must wear protective suits<ref name="sfnow20191027" /> due to toxic hypergolic gases.Template:Cn

Design

File:World's First Five Spaceplanes.PNG

The X-37 (far right) is the smallest and lightest orbital spaceplane yet flown. Both the North American X-15 and SpaceShipOne were suborbital. Of the spaceplanes shown, only the X-37 and Buran conducted uncrewed spaceflights.

The X-37 Orbital Test Vehicle is a reusable robotic spaceplane. It is an approximately 120-percent-scale derivative of the Boeing X-40,<ref name=MSFC_X-37_Tech_Demonstrator /><ref name="avweek20080803"/> measuring over Template:Convert in length, and features two angled tail fins.<ref name=USAF_factsh>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>Template:Sfn The X-37 launches atop an Atlas V 501<ref name="USAF_factsh"/><ref name="spaceplane_to_orbit"/> or a SpaceX Falcon 9<ref>Template:Cite news</ref> or Falcon Heavy<ref>Template:Cite news</ref> rocket. The spaceplane is designed to operate in a speed range of up to Mach 25 on its reentry.<ref name="nbcnews20050527">Template:Cite news</ref><ref name="nasax37facts2">{{#invoke:citation/CS1|citation |CitationClass=web }} Template:PD-notice</ref>

The technologies demonstrated in the X-37 include an improved thermal protection system, enhanced avionics, an autonomous guidance system and an advanced airframe.Template:Sfn The spaceplane's thermal protection system is built upon previous generations of atmospheric reentry spacecraft,<ref name="USAF_CollMaxwell">Template:Cite report</ref> incorporating silica ceramic tiles.<ref name="AF_press_conference">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The X-37's avionics suite was used by Boeing to develop its CST-100 crewed spacecraft.<ref name="Space20120405">Template:Cite news</ref> The development of the X-37 was to "aid in the design and development of NASA's Orbital Space Plane, designed to provide a crew rescue and crew transport capability to and from the International Space Station", according to a NASA fact sheet.<ref name="spdaily20120617">Template:Cite news</ref>

The X-37 for NASA was to be powered by one Aerojet AR2-3 engine using storable propellants, providing thrust of Template:Convert.<ref name="AndersonW2000">Template:Cite conference</ref> The human-rated AR2-3 engine had been used on the dual-power NF-104A astronaut training vehicle and was given a new flight certification for use on the X-37 with hydrogen peroxide/JP-8 propellants.<ref name="nasa20090724">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> This was reportedly changed to a hypergolic nitrogen-tetroxide/hydrazine propulsion system.<ref name="GSP"/><ref name="airspace201602">Template:Cite news</ref> The X-37 lands automatically upon returning from orbit and is the third reusable spacecraft to have such a capability, after the Soviet Buran shuttle<ref name="rockets_and_people">Template:Cite book Template:PD-notice</ref> and the U.S. space shuttle, which had automatic landing capability by the mid-1990s, but never tested it.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The X-37 is the smallest and lightest orbital spaceplane flown to date; it has a launch mass of around Template:Convert and is approximately one quarter the size of the Space Shuttle orbiter.<ref name="X-37B_shrouded" />

On 13 April 2015, the Space Foundation awarded the X-37 team with the 2015 Space Achievement Award "for significantly advancing the state of the art for reusable spacecraft and on-orbit operations, with the design, development, test and orbital operation of the X-37B space flight vehicle over three missions totaling 1,367 days in space".<ref name='Award2015'>Template:Cite news</ref>

Operational history

The two operational X-37Bs have completed seven orbital missions; they have spent a combined 4,208.66 days (11.53 years) in space.

Flight	Vehicle<ref>DutchSpace. "X-37B Mission Information and vehicle used".</ref>	Launch site	Launch date	Landing date	Launcher	Mission<ref name="gunter-otv">{{#invoke:citation/CS1|citation	CitationClass=web }}</ref>	Duration	Notes	Status
OTV-1	1	Cape Canaveral, SLC-41	Template:Sort 23:52 UTC	Template:Sort 09:16 UTC	Atlas V 501	USA-212	Template:Time interval	First launch of Atlas V 501 configuration First American autonomous orbital runway landing First X-37B flight Landed at Vandenberg AFB Runway 12	Template:Success
OTV-2	2		Template:Sort 22:46 UTC	Template:Sort 12:48 UTC	Atlas V 501	USA-226	Template:Time interval	First flight of second X-37B Landed at Vandenberg AFB Runway 12	Template:Success
OTV-3	1		Template:Sort 18:03 UTC	Template:Sort 16:24 UTC	Atlas V 501	USA-240	Template:Time interval	Second flight of first X-37B Landed at Vandenberg AFB Runway 12	Template:Success
OTV-4	2		Template:Sort 15:05 UTC	Template:Sort 11:47 UTC	Atlas V 501	USA-261 (AFSPC-5)	Template:Time interval	Second flight of second X-37B First landing on the Shuttle Landing Facility Runway 15 at Kennedy Space Center	Template:Success
OTV-5	2	Kennedy, LC-39A	Template:Sort 14:00 UTC	Template:Sort 07:51 UTC	Falcon 9 Block 4	USA-277	Template:Time interval	Third flight of second X-37B First launch of an X-37B on SpaceX's Falcon 9 vehicle Landed at Shuttle Landing Facility Runway 33	Template:Success
OTV-6	1	Cape Canaveral,SLC-41	Template:Sort 13:14 UTC	Template:Sort 10:22 UTC	Atlas V 501	USA-299 (USSF-7)	Template:Time interval	Third flight of first X-37B Carried most experiments to date First X-37B launch by USSF Longest X-37B mission Landed at Shuttle Landing Facility Runway 33	Template:Success
OTV-7	2	Kennedy, LC-39A	Template:Sort 01:07 UTC	Template:Sort 07:22 UTC	Falcon Heavy	USSF-52	Template:Time interval	First launch of an X-37B on SpaceX Falcon Heavy Fourth flight of second X-37B First spaceplane beyond low earth orbit in a highly elliptical, high Earth orbit<ref name=":0" /> Landed at Vandenberg SFB Runway 12	Template:Success

OTV-1

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File:Boeing X-37B after landing at Vandenberg AFB, 3 December 2010.jpg

X-37B 1 sits on the runway after landing at Vandenberg SFB at the end of its OTV-1 (USA-212) mission on 3 December 2010.

The first X-37B launched on its first mission–OTV-1/USA-212–on an Atlas V rocket from Cape Canaveral SLC-41 on 22 April 2010 at 23:52 UTC. The spacecraft was placed into low Earth orbit for testing.<ref name="spaceplane_to_orbit">Template:Cite news</ref> While the U.S. Air Force revealed few orbital details of the mission, a worldwide network of amateur astronomers claimed to have identified the spacecraft in orbit. On 22 May 2010, the spacecraft was in an inclination of 39.99°, circling the Earth once every 90 minutes on an orbit Template:Convert.<ref name="Space_Plane_Spotted">Template:Cite news</ref><ref name="Amateur_astronomers_unravel">Template:Cite news</ref> OTV-1 reputedly passed over the same given spot on Earth every four days, and operated at an altitude that is typical for military surveillance satellites.<ref name="nytimes20100521">Template:Cite news</ref> Such an orbit is also common among civilian LEO satellites, and the spaceplane's altitude was the same as that of the ISS and most other crewed spacecraft.

The U.S. Air Force announced a 3–6 December landing on 30 November 2010.<ref name="usaf20101130">Template:Cite news</ref><ref name="avweek20101130">Template:Cite newsTemplate:Dead link</ref> As scheduled, the X-37B was de-orbited, reentered Earth's atmosphere, and landed successfully at Vandenberg AFB on 3 December 2010, at 09:16 UTC,<ref name="sfnow20101203">Template:Cite news</ref><ref name="AW_X-37B_completes">Template:Cite news</ref><ref name="BBC_X-37B_returns">Template:Cite news</ref> conducting the first US autonomous orbital landing onto a runway. This was the first such landing since the Soviet Buran shuttle in 1988. In all, OTV-1 spent Template:Time interval in space.<ref name="spaceplane_to_orbit"/><ref name="sfnow20101203"/> OTV-1 suffered a tire blowout during landing and sustained minor damage to its underside.<ref name=AW_2nd_X-37B_prepared/>

OTV-2

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The second X-37B launched on its inaugural mission, designated OTV-2/USA-226,<ref name="n2yo37375">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> aboard an Atlas V rocket from Cape Canaveral SLC-41 on 5 March 2011 at 22:46 UTC.<ref name="sfnow20110305">Template:Cite news</ref> The mission was classified and described by the U.S. military as an effort to test new space technologies.<ref name="Space20110505">Template:Cite news</ref> On 29 November 2011, the U.S. Air Force announced that it would extend USA-226 beyond the 270-day baseline duration.<ref name="sfn20111129">Template:Cite news</ref> In April 2012, General William L. Shelton of the Air Force Space Command declared the ongoing mission a "spectacular success".<ref name="nbcnews20120509">Template:Cite news</ref>

On 30 May 2012, the Air Force stated that the X-37B would land at Vandenberg AFB in June 2012.<ref name="usaf20120530">Template:Cite news</ref><ref name="Space20120530">Template:Cite news</ref> The spacecraft landed autonomously on 16 June 2012, having spent Template:Time interval in space.<ref name="sfnow20110305"/><ref name=X372012>Template:Cite news</ref><ref name="SpaceComLanding">Template:Cite news</ref>

OTV-3

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The third mission and second flight of the first X-37B, OTV-3 was originally scheduled to launch on 25 October 2012,<ref name="sfnow20120918">Template:Cite news</ref> but was postponed because of an engine issue with the Atlas V launch vehicle.<ref name="afmag20121025">Template:Cite news</ref> It was successfully launched from Cape Canaveral SLC-41 on 11 December 2012 at 18:03 UTC.<ref name="X-37B_shrouded">Template:Cite news</ref><ref name="LaunchTheThird">Template:Cite news</ref><ref name="December2012OTV">Template:Cite news</ref> Once in orbit, the spacecraft was designated USA-240.<ref name="nssdc2012071a">{{#invoke:citation/CS1|citation |CitationClass=web }} Template:PD-notice</ref><ref name="usaf20121211">Template:Cite news</ref> Landing occurred at Vandenberg AFB on 17 October 2014 at 16:24 UTC, after a total time in orbit of Template:Time interval.<ref name="LaunchTheThird"/><ref name="fltglobal20141017"/><ref name="guardian20141017"/><ref name="space20141017"/>

OTV-4

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The fourth X-37B mission, OTV-4, was codenamed AFSPC-5 and designated as USA-261 in orbit. It was the second flight of the second X-37B vehicle.<ref name="GSP"/> The X-37B launched on an Atlas V rocket from Cape Canaveral SLC-41 on 20 May 2015 at 15:05 UTC.<ref name="sfnow20150520">Template:Cite news</ref> Objectives included a test of Aerojet Rocketdyne's XR-5A Hall-effect thruster in support of the Advanced Extremely High Frequency communications satellite program,<ref name="sfn20150427">Template:Cite news</ref><ref name="ajrdpr20150701">Template:Cite press release</ref> and a NASA investigation on the performance of various materials in space<ref name="GSP"/><ref name="Award2015"/><ref name="space20150520">Template:Cite news</ref> for at least 200 days.<ref name="GSP"/> The vehicle spent what was then a record-breaking Template:Time interval in orbit before landing at Kennedy Space Center's Shuttle Landing Facility on 7 May 2017 at 11:47 UTC.<ref name="sfnow20170507">Template:Cite news</ref><ref>Template:Cite news</ref>

OTV-5

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The fifth X-37B mission, designated USA-277 in orbit,<ref name="gunter-otv" /> was launched from Kennedy Space Center Launch Complex 39A on 7 September 2017 at 14:00 UTC, just before the arrival of Hurricane Irma.<ref name="verge-20170907">Template:Cite news</ref><ref name="nsf-20170907">Template:Cite news</ref> The launch vehicle was a Falcon 9 rocket,<ref name="nsf-20170907" /> and a number of small satellites also shared the ride.<ref name="afspc-20170831" /> The spacecraft was inserted at a higher inclination orbit than previous missions, further expanding the X-37B's envelope.<ref name="afspc-20170831">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> During the flight, the spacecraft modified its orbit using an on-board propulsion system.<ref>Template:Cite news</ref> While the complete payload for OTV-5 is classified, the Air Force announced that one experiment flying is the Advanced Structurally Embedded Thermal Spreader II (ASETS-II), which measures the performance of an oscillating heat pipe.<ref name="afrl-asets2">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The mission was completed with the vehicle landing at the Shuttle Landing Facility on 27 October 2019 at 07:51 UTC.<ref name="sfnow20191027">Template:Cite news</ref><ref name="today20191027">Template:Cite news</ref>

OTV-6

File:X-37B concludes sixth mission (221111-F-XX000-0002).jpg

X-37B 1 sits on the runway after landing at the Shuttle Landing Facility at KSC on 12 November 2022, the 909th day of the OTV-6 (USA-299) mission

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The sixth X-37B mission (OTV-6), U.S. Space Force 7 (formerly known as AFSPC 7), launched on an Atlas V 501 rocket from Cape Canaveral SLC-41 on 17 May 2020 at 13:14:00 UTC.<ref name="nsf20200517">Template:Cite news</ref> This mission is the first time the spaceplane has carried a service module, a ring attached to the rear of the vehicle for hosting multiple experiments.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The mission hosts more experiments than prior X-37B flights, including two NASA experiments. One is a sample plate evaluating the reaction of select materials to conditions in space. The second studies the effect of ambient space radiation on seeds. A third experiment designed by the Naval Research Laboratory (NRL) transforms solar power into radio frequency microwave energy, then studies transmitting that energy to Earth. The X-37B remains a Department of the Air Force asset, but the newly established U.S. Space Force is responsible for the launch, on-orbit operations, and landing.<ref name="SFN20200506">Template:Cite news</ref><ref name="ussf20200506">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

The X-37B released a small, Template:Cvt satellite named FalconSat-8 (USA-300) around 28 May 2020.<ref>Template:Cite news</ref> Developed by United States Air Force Academy cadets in partnership with the Air Force Research Laboratory (AFRL), the small satellite carries five experimental payloads. The spacecraft will test a novel electromagnetic propulsion system, low-weight antenna technology and a commercial reaction wheel to provide attitude control in orbit. According to the United States Air Force Academy, FalconSat-8's experiments include:<ref name="sfn20200517">Template:Cite news</ref>

• Magnetogradient Electrostatic Plasma Thruster (MEP) – Novel electromagnetic propulsion system
• MetaMaterial Antenna (MMA) – Low size, weight, power antenna with phased array-like performance
• Carbon nanotube experiment (CANOE) – RF cabling with carbon nanotube braiding flexed using shape-memory alloy
• Attitude Control and Energy Storage (ACES) – Commercial reaction wheel modified into a flywheel for energy storage and release
• SkyPad – Off-the-shelf cameras and GPUs integrated into low-SWAP (size, weight and power) package

The mission was completed with the vehicle landing at the Shuttle Landing Facility on 12 November 2022 at 10:22 UTC.<ref name="ussf-20221112"/>

OTV-7

File:Novel space maneuver conducted by X-37B (8878863).jpg

An X-37B onboard camera captures an image of Earth while conducting experiments in a highly elliptical orbit in 2024.

{{#invoke:Labelled list hatnote|labelledList|Main article|Main articles|Main page|Main pages}} The fourth flight of second<ref>DutchSpace. "OTV-7 image analysis". X, 30 November 2023.</ref> X-37B and seventh overall X-37B mission was planned to be launched on SpaceX's Falcon Heavy on 12 December 2023.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> It was rescheduled for 28 December 2023,<ref>Template:Cite tweet Template:Better source</ref> when it was successfully launched at 8:07 pm EST (01:07:00 UTC on December 29).<ref>Erwin, Sandra. "SpaceX launches U.S. military spaceplane on Falcon Heavy rocket". Space News, 28 December 2023.</ref> The orbit is higher than any spaceplane, in a highly elliptical HEO orbit.<ref name=":0" /> In October 2024, OTV-7 was due to undertake aerobraking maneuvers to safely dispose of its service module.<ref>Template:Cite news</ref> The mission ended on with landing at Vandenberg Space Force Base on 7 March 2025 at 07:22 UTC.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Variants

X-37A

The X-37A Approach and Landing Test Vehicle (ALTV) was an initial NASA version of the spacecraft used in drop glide tests in 2005 and 2006.<ref name="designation-systems">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="Shuttle_Jr"/>

X-37B

The X-37B is a modified version of the NASA X-37A, built for the U.S. Air Force.<ref name="USAF_factsh"/> Two have been built and used for multiple orbital missions.<ref name="LaunchTheThird"/>

X-37C

In 2011, Boeing announced plans for a scaled-up variant of the X-37B, referring to it as the X-37C. This spacecraft was planned to be between 165% and 180% of the size of the X-37B, allowing it to transport up to six astronauts inside a pressurized compartment housed in the cargo bay. The Atlas V was this variant's proposed launch vehicle.<ref name=sdc20111007>Template:Cite news</ref> In this role, Boeing's X-37C could potentially compete with the corporation's CST-100 Starliner commercial space capsule.<ref name="cis20120325">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Template:As of, with NASA selecting Starliner and SpaceX Crew Dragon, there has been no further announcement to develop X-37C.<ref>Template:Cite press release</ref><ref name="aw20110422">Template:Cite news</ref><ref name="spacenews.com">Template:Cite news</ref><ref name="nasa.gov">Template:Cite news Template:PD-notice</ref>

See also

• Boeing X-20 Dyna-Soar, the U.S. Air Force's original (1958–1963) spaceplane program, cancelled before craft was constructed
• Dream Chaser, a lifting-body spaceplane being developed by Sierra Nevada Corporation
• Orbital Sciences X-34, a proposed uncrewed suborbital reusable-rocket technology testbed
• RLV Technology Demonstration Programme, Indian reusable spaceplane development project
• Hermes (spacecraft), a proposed ESA spacecraft design
• HOPE-X, a similar-sized vehicle of comparable role by JAXA (cancelled)
• HYFLEX, a Japanese lifting body spaceplane in 1996, precursor to HOPE-X
• Intermediate eXperimental Vehicle (IXV), an ESA designed experimental reentry vehicle
• Shenlong (spacecraft), a Chinese reusable robotic spaceplane under development, first tested in 2011 (suborbital flight)
• Chinese reusable experimental spacecraft, a reusable spaceplane under development
• Skylon (spacecraft), a British reusable uncrewed spaceplane in development
• Space Rider, a planned robotic spaceplane follow-up to IXV by ESA
• Collier Trophy
• List of USA satellites
• List of X-planes

Sources

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Further reading

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External links

• X-37 Orbital Test Vehicle fact sheet from the U.S. Air Force
• X-37B Orbital Test Vehicle page at Boeing.com
• X-37 fact sheet Template:Webarchive at NASA.gov
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