Boeing X-37

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

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.{{cite web|url=http://www.nasa.gov/centers/marshall/pdf/100431main_x37-historical.pdf|title=X-37 Technology Demonstrator: Blazing the trail for the next generation of space transportation systems|publisher=NASA|series=NASA Facts|date=September 2003|access-date=23 April 2010|id=FS-2003-09-121-MSFC|archive-date=14 February 2021|archive-url=https://web.archive.org/web/20210214170258/https://www.nasa.gov/centers/marshall/pdf/100431main_x37-historical.pdf|url-status=dead}} {{PD-notice}}

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.{{cite web |url=http://www.dodlive.mil/index.php/2010/04/air-force-bloggers-roundtable-air-force-set-to-launch-first-x-37b-orbital-test-vehicle/ |title=Air Force Bloggers Roundtable: Air Force set to launch first X-37B Orbital Test Vehicle |publisher=United States Department of Defense |date=20 April 2010 |access-date=23 April 2010 |archive-url=https://web.archive.org/web/20100424060839/http://www.dodlive.mil/index.php/2010/04/air-force-bloggers-roundtable-air-force-set-to-launch-first-x-37b-orbital-test-vehicle/ |archive-date=24 April 2010 |url-status=live}} An early requirement for the spacecraft called for a total mission delta-v of {{convert|7000|mph|km/s}} for orbital maneuvers.{{cite news |url=http://www.spaceflightnow.com/atlas/av012/100402x37update/ |title=Air Force spaceplane is an odd bird with a twisted past |work=Spaceflight Now |first=Stephen |last=Clark |date=2 April 2010 |access-date=3 April 2010 |archive-url=https://web.archive.org/web/20100405201814/http://www.spaceflightnow.com/atlas/av012/100402x37update/ |archive-date=5 April 2010 |url-status=live}} An early goal for the program was for the X-37 to rendezvous with satellites and perform repairs.{{cite press release |url=http://www.hq.nasa.gov/office/pao/History/x-33/99-139.htm |title=NASA, Boeing Enter Cooperative Agreement to Develop and Fly X-37 Technology Demonstrator |publisher=NASA |date=14 July 1999 |access-date=20 October 2014 |id=Press Release 99-139 |archive-url=https://web.archive.org/web/20150626151311/http://www.hq.nasa.gov/office/pao/History/x-33/99-139.htm |archive-date=26 June 2015 |url-status=live}} {{PD-notice}} 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.{{sfn|Yenne|2005|p=277}}

The X-37 was transferred from NASA to the Defense Advanced Research Projects Agency (DARPA) on 13 September 2004.{{cite news |url=http://www.space.com/news/x37_darpa_040915.html |title=NASA Transfers X-37 Project to DARPA |work=Space.com |first=Brian |last=Berger |date=15 September 2004 |access-date=15 August 2008 |archive-url=https://web.archive.org/web/20080905111429/http://www.space.com/news/x37_darpa_040915.html |archive-date=5 September 2008 |url-status=live}} 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.

File:Scaled-wk-070711-08-16.jpg 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.{{cite news |url=https://www.nbcnews.com/id/wbna6001932 |title=DARPA takes on space plane project |work=NBC News |first=Brian |last=Berger |date=16 September 2004 |access-date=19 October 2014 |archive-url=https://web.archive.org/web/20141016020508/http://www.nbcnews.com/id/6001932 |archive-date=16 October 2014 |url-status=live}}

On 21 June 2005, the X-37A completed a captive-carry flight underneath the White Knight from Mojave Spaceport in Mojave, California.{{cite news |url=http://www.cnn.com/2005/TECH/space/06/23/white.knight/index.html |title=White Knight carries X-37 aloft |work=CNN |first=Leonard |last=David |date=23 June 2005 |access-date=15 October 2012 |archive-url=https://web.archive.org/web/20121109005023/http://www.cnn.com/2005/TECH/space/06/23/white.knight/index.html |archive-date=9 November 2012 |url-status=live}} 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.{{cite web |url=http://www.mojaveweblog.com/ |title=Mojave web log entries |work=MojaveWeblog.com |access-date=15 October 2012 |archive-url=https://web.archive.org/web/20060604074814/http://www.mojaveweblog.com/ |archive-date=4 June 2006}} The next flight attempt, on 15 March 2006, was canceled due to high winds.

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.{{cite news |url=http://www.space.com/missionlaunches/060407_x37_drop.html |title=X-37 Flies at Mojave But Encounters Landing Problems |work=Space.com |first=Leonard |last=David |date=7 April 2006 |access-date=18 January 2009 |archive-url=https://web.archive.org/web/20090606053255/http://www.space.com/missionlaunches/060407_x37_drop.html |archive-date=6 June 2009 |url-status=live}} 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,Source of flights: mission markings posted on side of White Knight aircraft two of which resulted in X-37 releases with successful landings. These two free flights occurred on 18 August 2006 and 26 September 2006.{{cite web |url=https://www.youtube.com/watch?v=bxJzPngPMo4 |title=X-37 Test Flight B-Roll (No Audio) |work=YouTube.com |publisher=U.S. Air Force |date=22 April 2010 |access-date=29 November 2016 |archive-url=https://web.archive.org/web/20160625013226/https://www.youtube.com/watch?v=bxJzPngPMo4 |archive-date=25 June 2016 |url-status=live}}

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.{{cite news |url=http://www.space.com/news/061117_x27b_otv.html |title=U.S. Air Force Pushes For Orbital Test Vehicle |work=Space.com |first=Leonard |last=David |date=17 November 2006 |access-date=17 November 2006 |archive-url=https://web.archive.org/web/20080724132321/http://www.space.com/news/061117_x27b_otv.html |archive-date=24 July 2008 |url-status=live}} The X-37B was designed to remain in orbit for up to 270 days at a time.{{cite news |url=http://spaceflightnow.com/atlas/av012/100225x37arrival/ |title=Air Force X-37B spaceplane arrives in Florida for launch |work=Spaceflight Now |first=Stephen |last=Clark |date= 25 February 2010 |access-date=3 March 2010 |archive-url=https://web.archive.org/web/20100301080636/http://spaceflightnow.com/atlas/av012/100225x37arrival/ |archive-date=1 March 2010 |url-status=live}} 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".

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.{{cite web |url=http://space.skyrocket.de/doc_sdat/x-37.htm |title=X-37B OTV 1, 2, 3, 4 |work=Gunter's Space Page |first=Gunter |last=Krebs |access-date=21 May 2015 |archive-url=https://web.archive.org/web/20150507083646/http://space.skyrocket.de/doc_sdat/x-37.htm |archive-date=7 May 2015 |url-status=live}} 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.{{cite news |url=http://www.aviationweek.com/aw/generic/story.jsp?id=news/aw080408p2.xml&headline=USAF%20To%20Launch%20First%20Spaceplane%20Demonstrator&channel=awst |title=USAF To Launch First Spaceplane Demonstrator |work=Aviation Week |first=Craig |last=Covault |date=3 August 2008 |archive-url=https://web.archive.org/web/20110812011945/http://www.aviationweek.com/aw/generic/story.jsp?id=news%2Faw080408p2.xml&headline=USAF%20To%20Launch%20First%20Spaceplane%20Demonstrator&channel=awst |archive-date=12 August 2011 |url-status=dead}} In 2010, manufacturing work began on the second X-37B,{{cite news |url=http://www.aviationweek.com/aw/generic/story_channel.jsp?channel=space&id=news/asd/2010/12/07/02.xml&headline=Second%20X-37B%20Prepared%20For%20Launch |title=Second X-37B Prepared For Launch |work=Aviation Week |first=Guy |last=Norris |date=7 December 2010}}{{dead link |date=January 2018|bot=InternetArchiveBot|fix-attempted=yes}} which conducted its maiden mission in March 2011.

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. 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.{{cite news |url=http://www.floridatoday.com/story/tech/science/space/2014/10/08/secretive-x37b-space-plane-will-use-nasa-space-shuttle-hangars/16930223/ |title=NASA: Secret X-37B space plane will use shuttle hangars |work=Florida Today |first=James |last=Dean |date=8 October 2014 |access-date=9 October 2014 |archive-url=https://web.archive.org/web/20230726015443/https://eu.floridatoday.com/story/tech/science/space/2014/10/08/secretive-x37b-space-plane-will-use-nasa-space-shuttle-hangars/16930223/ |archive-date=26 July 2023 |url-status=live}}

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". The primary objectives of the X-37B are twofold: reusable spacecraft technology and operating experiments, which can be returned to Earth. The Air Force states that this includes testing avionics, flight systems, guidance and navigation, thermal protection, insulation, propulsion, and re-entry systems.{{cite news |url=http://www.airspacemag.com/daily-planet/now-we-know-least-two-payloads-x-37b-180955405/?no-ist |title=Now We Know at Least Two Payloads on the X-37B |work=Air & Space/Smithsonian |last=Smith-Strickland |first=Kiona |date=27 May 2015 |access-date=27 May 2015 |archive-url=https://web.archive.org/web/20150527163801/http://www.airspacemag.com/daily-planet/now-we-know-least-two-payloads-x-37b-180955405/?no-ist |archive-date=27 May 2015 |url-status=live}}

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.{{cite news |url=http://www.spacedaily.com/reports/The_Militarization_of_Outer_Space_The_Pentagon_Space_Warriors_999.html |title=The Militarization of Outer Space: The Pentagon's Space Warriors |work=Space Daily |first=Tom |last=Burghardt |date=11 May 2010 |access-date=15 October 2012 |archive-url=https://web.archive.org/web/20221013235558/https://www.spacedaily.com/reports/The_Militarization_of_Outer_Space_The_Pentagon_Space_Warriors_999.html |archive-date=13 October 2022 |url-status=live}} In January 2012, allegations were made that the X-37B was being used to spy on China's Tiangong-1 space station module.{{cite news |url=https://www.theregister.co.uk/2012/01/06/x_37b_spying_tiangong_1/ |title=US 'space warplane' may be spying on Chinese spacelab |work=The Register |first=Brid-Aine |last=Parnell |date=6 January 2012 |access-date=13 January 2012 |archive-url=https://web.archive.org/web/20120108202545/http://www.theregister.co.uk/2012/01/06/x_37b_spying_tiangong_1/ |archive-date=8 January 2012 |url-status=live}} 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.{{cite news |url=http://au.ibtimes.com/articles/278442/20120109/expert-u-s-secret-space-plane-spying.htm |title=Expert: U. S. Secret Space Plane Not Likely 'Spying' on China Module |work=International Business Times |first=Genalyn |last=Corocoto |date=9 January 2012 |access-date=13 January 2012 |url-status=dead |archive-url=https://web.archive.org/web/20120111080248/http://au.ibtimes.com/articles/278442/20120109/expert-u-s-secret-space-plane-spying.htm |archive-date=11 January 2012}}

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".{{cite news |url=https://www.theguardian.com/us-news/2014/oct/26/x37b-us-military-secret-space-plane-mission |title=X-37B secret space plane's mission remains mystery outside US military |work=The Guardian |first=Alan |last=Yuhas |date=27 October 2014 |access-date=28 October 2014 |archive-url=https://web.archive.org/web/20141028220502/http://www.theguardian.com/us-news/2014/oct/26/x37b-us-military-secret-space-plane-mission |archive-date=28 October 2014 |url-status=live}} 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.{{cite news |url=http://www.ibtimes.co.uk/space-race-revealed-us-china-test-futuristic-emdrive-tiangong-2-mysterious-x-37b-plane-1590289 |title=Space race revealed: US and China test futuristic EmDrive on Tiangong-2 and mysterious X-37B plane |work=International Business Times |last1=Russon |first1=Mary-Ann |date=7 November 2016 |access-date=15 December 2016 |archive-url=https://web.archive.org/web/20230524022356/https://www.ibtimes.co.uk/space-race-revealed-us-china-test-futuristic-emdrive-tiangong-2-mysterious-x-37b-plane-1590289 |archive-date=24 May 2023 |url-status=live}} 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.{{cite journal |url=http://www.emdrive.com/IAC14publishedpaper.pdf |title=Second generation EmDrive propulsion applied to SSTO launcher and interstellar probe |journal=Acta Astronautica |first=Roger |last=Shawyer |volume=116 |pages=166–174 |date=November–December 2015 |doi=10.1016/j.actaastro.2015.07.002 |archive-url=https://web.archive.org/web/20230324165752/http://www.emdrive.com/IAC14publishedpaper.pdf |archive-date=24 March 2023 |url-status=live}}{{cite web |author1=UK Department of Trade and Industry |title=Boeing End User Undertaking |url=https://drive.google.com/file/d/0B7kgKijo-p0idV9tcmVIVzZrdTQ/view |archive-url=https://web.archive.org/web/20161019052837/https://drive.google.com/file/d/0B7kgKijo-p0idV9tcmVIVzZrdTQ/view |url-status=dead |archive-date=19 October 2016 |access-date=15 December 2016 |date=2007}} Boeing has since stated that it is no longer pursuing this area of research.{{cite news |url=http://aviationweek.com/awin/propellentless-space-propulsion-research-continues |title=Propellentless Space Propulsion Research Continues |last1=Hambling |first1=David |work=Aviation Week & Space Technology |date=5 November 2012 |access-date=16 December 2016 |url-access=subscription}} The U.S. Air Force has stated that the X-37B is testing a Hall-effect thruster system for Aerojet Rocketdyne.

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.{{cite news |url=https://www.military.com/daily-news/2019/07/23/former-secaf-explains-how-secret-x-37-space-plane-throws-enemies.html |title=Former SecAF Explains How Secret X-37 Space Plane Throws Off Enemies |website=Military.com |last=Pawlyk |first=Oriana |date=23 July 2019 |access-date=23 July 2020 |archive-url=https://web.archive.org/web/20231102195845/https://www.military.com/daily-news/2019/07/23/former-secaf-explains-how-secret-x-37-space-plane-throws-enemies.html |archive-date=2 November 2023 |url-status=live}}

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

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.{{Cite web |url=https://spaceflightnow.com/atlas/av012/100422launch/ |title= Atlas rocket delivers Air Force spaceplane to orbit |website= Spaceflightnow.com |date= 22 April 2010 |access-date= 17 January 2024}}{{Cite web |url=https://www.thedrive.com/the-war-zone/30699/here-what-we-know-the-shadowy-x-37b-was-up-to-during-its-record-720-days-in-space |title= Here's What We Know the Shadowy X-37B Was up to During Its Record 780 Days in Space |date= 28 October 2019 |website= theDrive.com |access-date= 17 January 2024}}

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 due to toxic hypergolic gases.{{cn|date=August 2022}}

File:World's First Five Spaceplanes.PNG 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, measuring over {{convert|29|ft|m}} in length, and features two angled tail fins.{{cite web |url=http://www.af.mil/AboutUs/FactSheets/Display/tabid/224/Article/104539/x-37b-orbital-test-vehicle.aspx |title=Fact Sheet: X-37 Orbital Test Vehicle |publisher=U.S. Air Force |date=21 May 2010 |archive-url=https://web.archive.org/web/20140626041942/http://www.af.mil/AboutUs/FactSheets/Display/tabid/224/Article/104539/x-37b-orbital-test-vehicle.aspx |archive-date=26 June 2014 |url-status=dead}}{{sfn|Miller|2001|p=377}} The X-37 launches atop an Atlas V 501 or a SpaceX Falcon 9{{cite news |url=https://www.theverge.com/2017/6/7/15751050/spacex-air-force-x-37b-spaceplane-falcon-9-launch-contract |title=SpaceX scores contract to launch Air Force's secretive X-37B spaceplane |work=The Verge |last=Grush |first=Loren |date=7 June 2017 |access-date=3 September 2017 |archive-url=https://web.archive.org/web/20170904012400/https://www.theverge.com/2017/6/7/15751050/spacex-air-force-x-37b-spaceplane-falcon-9-launch-contract |archive-date=4 September 2017 |url-status=live}} or Falcon Heavy{{cite news|url=https://spacenews.com/u-s-air-force-x-37b-spaceplane-to-launch-on-a-spacex-falcon-heavy-rocket/ |title=U.S. Air Force X-37B spaceplane to launch on a SpaceX Falcon Heavy rocket |work=Space News}} rocket. The spaceplane is designed to operate in a speed range of up to Mach 25 on its reentry.{{cite news |url=https://www.nbcnews.com/id/wbna8008541 |title=Mothership adopts a new space plane |work=NBC News |first=Leonard |last=David |date=27 May 2005 |access-date=2 February 2013 |archive-url=https://web.archive.org/web/20140202135514/http://www.nbcnews.com/id/8008541/ |archive-date=2 February 2014 |url-status=live}}{{cite web |url=http://www.nasa.gov/centers/marshall/news/background/facts/x37facts2.html |title=X-37 Demonstrator to Test Future Launch Technologies in Orbit and Reentry Environments |publisher=NASA |date=May 2003 |access-date=2 February 2013 |id=FS-2003-05-65-MSFC |archive-url=https://web.archive.org/web/20121024120833/http://www.nasa.gov/centers/marshall/news/background/facts/x37facts2.html |archive-date=24 October 2012 |url-status=live}} {{PD-notice}}

The technologies demonstrated in the X-37 include an improved thermal protection system, enhanced avionics, an autonomous guidance system and an advanced airframe.{{sfn|Yenne|2005|p=277}} The spaceplane's thermal protection system is built upon previous generations of atmospheric reentry spacecraft,{{cite report |url=http://apps.dtic.mil/dtic/tr/fulltext/u2/a407255.pdf |title=X-37 Space Vehicle: Starting a New Age in Space Control? |publisher=Defense Technical Information Center |first=Austin D. |last=Jameson |date=April 2001 |id=ADA407255 |access-date=19 October 2014 |archive-url=https://web.archive.org/web/20141019122346/http://www.dtic.mil/dtic/tr/fulltext/u2/a407255.pdf |archive-date=19 October 2014 |url-status=live}} incorporating silica ceramic tiles.{{cite web |url=http://www.defense.gov/Blog_files/Blog_assets/PaytonX-37.pdf |title=Mr. Gary Payton, Under Secretary of the Air Force for Space Programs, Media Teleconference (Pentagon), X-37B Launch |work=Defense.gov |date=20 April 2010 |access-date=3 December 2010 |url-status=dead |archive-url=https://web.archive.org/web/20120125072253/http://www.defense.gov/Blog_files/Blog_assets/PaytonX-37.pdf |archive-date=25 January 2012}} The X-37's avionics suite was used by Boeing to develop its CST-100 crewed spacecraft.{{cite news |url=http://www.space.com/15173-boeing-cst100-spaceship-update.html |title=Boeing's New Crew-Carrying Spaceship Taking Shape |work=Space.com |first=Leonard |last=David |date=5 April 2012 |access-date=17 April 2012 |archive-url=https://web.archive.org/web/20120407190000/http://www.space.com/15173-boeing-cst100-spaceship-update.html |archive-date=7 April 2012 |url-status=live}} 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.{{cite news |url=http://www.spacedaily.com/reports/Pilotless_US_space_plane_lands_after_469_days_in_orbit_999.html |title=Pilotless US space plane lands after 469 days in orbit |work=Space Daily |agency=AFP |date=17 June 2012 |access-date=18 June 2012 |archive-url=https://web.archive.org/web/20120627042701/http://www.spacedaily.com/reports/Pilotless_US_space_plane_lands_after_469_days_in_orbit_999.html |archive-date=27 June 2012 |url-status=live}}

The X-37 for NASA was to be powered by one Aerojet AR2-3 engine using storable propellants, providing thrust of {{convert|6600|lbf|kN|sigfig=3}}.{{cite conference |url=https://ntrs.nasa.gov/search.jsp?R=20000033615 |title=Peroxide Propulsion at the Turn of the Century |conference=4th International Symposium on Liquid Space Propulsion. 13 March 2000. Heilbronn, Germany. |first1=William E. |last1=Anderson |first2=Kathy |last2=Butler |first3=Dave |last3=Crocket |first4=Tim |last4=Lewis |first5=Curtis |last5=McNeal |date=2000 |id=5487a |access-date=7 July 2017 |archive-url=https://web.archive.org/web/20160807023832/http://ntrs.nasa.gov/search.jsp?R=20000033615 |archive-date=7 August 2016 |url-status=live}} 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.{{cite web |url=http://sscfreedom.ssc.nasa.gov/etd/ETDPropulsionSS_H2O2AR23.asp |title=Peroxide (H2O2) Test Programs, AR2-3 Flight Certification |publisher=NASA Engineering and Test Directorate |first=Bartt |last=Herbert |date=24 July 2009 |url-status=dead |archive-url=https://web.archive.org/web/20110721053057/http://sscfreedom.ssc.nasa.gov/etd/ETDPropulsionSS_H2O2AR23.asp |archive-date=21 July 2011}} This was reportedly changed to a hypergolic nitrogen-tetroxide/hydrazine propulsion system.{{cite news |url=http://www.airspacemag.com/space/spaceplane-x-37-180957777/ |title=What's the X-37 Doing Up There? |work=Air & Space/Smithsonian |first=Kiona |last=Smith-Strickland |date=February 2016 |access-date=12 April 2016 |archive-url=https://web.archive.org/web/20160407022953/http://www.airspacemag.com/space/spaceplane-x-37-180957777/ |archive-date=7 April 2016 |url-status=live}} 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{{cite book |url=https://ntrs.nasa.gov/search.jsp?R=20050010181 |title=Rockets and People |script-title=ru:Ракеты и люди |volume=1 |publisher=NASA |series=NASA History Series |first=Boris E. |last=Chertok |editor-first=Asif A. |editor-last=Siddiqi |year=2005 |page=179 |id=SP-2005-4110 |access-date=7 July 2017 |archive-url=https://web.archive.org/web/20181006083046/https://ntrs.nasa.gov/search.jsp?R=20050010181 |archive-date=6 October 2018 |url-status=live}} {{PD-notice}} and the U.S. space shuttle, which had automatic landing capability by the mid-1990s, but never tested it.{{cite web|url=https://historycollection.jsc.nasa.gov/JSCHistoryPortal/history/oral_histories/NASA_HQ/Administrators/HaleNW/HaleNW_5-28-14.htm|title=N. Wayne Hale Oral History|date=May 28, 2014|publisher=NASA|quote=There was always a concern, particularly as we got these longer and longer flights, there’s some vestibular things that happen, some vision changes that happen with people, and we were concerned about them landing. We wanted to make sure we had a viable auto-land system, and the program manager gave us direction to test that out. For STS-53, we worked very, very hard to dot all the i’s and cross all the t’s so we could do an auto-land test. An auto-land test—you’re using a real Orbiter with the live crew. They’ve got to, no kidding, be right on the mark, or it could be really bad. ...Jed [Jeremiah W.] Pearson, who was the associate administrator for human spaceflight, former Marine Corps general, as I recall, reviewed it and said, “We’re not going to be flying any more of these long-duration flights. We don’t need to do this. We’re going to knock this off.” Devastating. The team was all set to do this. We were all ready to do this, we were so excited about doing it, thought it would be a good capability. |archive-url=https://web.archive.org/web/20230622182821/https://historycollection.jsc.nasa.gov/JSCHistoryPortal/history/oral_histories/NASA_HQ/Administrators/HaleNW/HaleNW_5-28-14.htm |archive-date=22 June 2023 |url-status=live}} The X-37 is the smallest and lightest orbital spaceplane flown to date; it has a launch mass of around {{convert|11000|lb|kg}} and is approximately one quarter the size of the Space Shuttle orbiter.

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".{{cite news |last=David |first=Leonard |url=http://www.space.com/29293-air-force-x37b-space-plane-details.html |title=Inside the US Air Force's Next X-37B Space Plane Mystery Mission |work=Space.com |date=8 May 2015 |access-date=11 May 2015 |archive-url=https://web.archive.org/web/20150510203155/http://www.space.com/29293-air-force-x37b-space-plane-details.html |archive-date=10 May 2015 |url-status=live}}

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

{{main|OTV-1}}

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

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.{{cite news |url=http://spaceflightnow.com/atlas/av012/100422launch/ |title=Atlas rocket delivers Air Force spaceplane to orbit |work=Spaceflight Now |first=Stephen |last=Clark |date=22 April 2010 |access-date=23 April 2010 |archive-url=https://web.archive.org/web/20100425005846/http://www.spaceflightnow.com/atlas/av012/100422launch/ |archive-date=25 April 2010 |url-status=live}} 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 {{convert|401|by|422|km|mi|order=flip}}.{{cite news |url=http://www.space.com/news/secret-x-37-b-space-plane-spotted-by-amateur-astronomers-100522.html |title=Secret X-37B Space Plane Spotted by Amateur Skywatchers |work=Space.com |first=Leonard |last=David |date=22 May 2010 |access-date=10 June 2010 |archive-url=https://web.archive.org/web/20100525234030/http://www.space.com/news/secret-x-37-b-space-plane-spotted-by-amateur-astronomers-100522.html |archive-date=25 May 2010 |url-status=live}}{{cite news |url=http://www.news.com.au/technology/amateur-astronomers-unravel-x37-b-orbit-say-likely-use-for-deploying-spy-satellites/story-e6frfro0-1225870574214 |title=Amateur astronomers unravel X37-B orbit, say likely use for deploying spy satellites |work=News.com.au |date=24 May 2010 |access-date=10 June 2010 |archive-url=https://web.archive.org/web/20100527025526/http://www.news.com.au/technology/amateur-astronomers-unravel-x37-b-orbit-say-likely-use-for-deploying-spy-satellites/story-e6frfro0-1225870574214 |archive-date=27 May 2010 |url-status=live}} 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.{{cite news |url=https://www.nytimes.com/2010/05/23/science/space/23secret.html |title=Surveillance is Suspected as Spacecraft's Main Role |work=The New York Times |first=William J. |last=Broad |date=21 May 2010 |access-date=22 May 2010 |archive-url=https://web.archive.org/web/20100526032355/http://www.nytimes.com/2010/05/23/science/space/23secret.html |archive-date=26 May 2010 |url-status=live}} 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.{{cite news |url=https://www.vandenberg.spaceforce.mil/?id=123232786 |title=Preparations underway for first landing of X-37B |publisher=U.S. Air Force |agency=30th Space Wing Public Affairs |date=30 November 2010 |access-date=21 May 2012 |url-status=live |archive-url=https://web.archive.org/web/20120305222949/http://www.vandenberg.af.mil/news/story.asp?id=123232786 |archive-date=5 March 2012}}{{cite news |url=https://aviationweek.com/awin/usaf-x-37b-landing-slated-dec-3-6-0 |title=USAF X-37B Landing Slated for Dec. 3–6 |work=Aviation Week |date=30 November 2010 |access-date=1 December 2010}}{{Dead link|date=June 2022 |bot=InternetArchiveBot |fix-attempted=yes}} 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,{{cite news |url=http://www.spaceflightnow.com/news/n1012/03x37landing/ |title=Home again: U.S. military space plane returns to Earth |work=Spaceflight Now |first=Stephen |last=Clark |date=3 December 2010 |access-date=3 December 2010 |archive-url=https://web.archive.org/web/20101204015756/http://www.spaceflightnow.com/news/n1012/03x37landing/ |archive-date=4 December 2010 |url-status=live}}{{cite news |url=http://www.aviationweek.com/Blogs.aspx?plckBlogId=Blog%3a27ec4a53-dcc8-42d0-bd3a-01329aef79a7&plckPostId=Blog%3a27ec4a53-dcc8-42d0-bd3a-01329aef79a7Post%3a39e8008f-3395-43b1-bf7b-c6db93c2ace0 |title=USAF's X-37B Spaceplane Returns to Earth |work=Aviation Week |first=Graham |last=Warwicj |date=3 December 2010 |access-date=2 June 2012 |url-status=dead |archive-url=https://web.archive.org/web/20120606134732/http://www.aviationweek.com/Blogs.aspx?plckBlogId=Blog:27ec4a53-dcc8-42d0-bd3a-01329aef79a7 |archive-date=6 June 2012}}{{cite news |url=https://www.bbc.co.uk/news/science-environment-11911335 |title=X-37B US military spaceplane returns to Earth |work=BBC News |first=Paul |last=Rincon |date=3 December 2010 |access-date=3 December 2010 |archive-url=https://web.archive.org/web/20101204044540/http://www.bbc.co.uk/news/science-environment-11911335 |archive-date=4 December 2010 |url-status=live}} 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 {{time interval|22 April 2010 23:52|3 December 2010 09:16|show=dh}} in space. OTV-1 suffered a tire blowout during landing and sustained minor damage to its underside.

{{main|OTV-2}}

The second X-37B launched on its inaugural mission, designated OTV-2/USA-226,{{cite web |url=http://www.n2yo.com/satellite/?s=37375 |title=OTV 2 (USA 226) Satellite details 2011-010A NORAD 37375 |work=N2YO.com |first=Mike |last=McCants |access-date=8 April 2012 |archive-url=https://web.archive.org/web/20120501102442/http://www.n2yo.com/satellite/?s=37375 |archive-date=1 May 2012 |url-status=live}} aboard an Atlas V rocket from Cape Canaveral SLC-41 on 5 March 2011 at 22:46 UTC.{{cite news |url=http://www.spaceflightnow.com/atlas/av026/ |title=Air Force's second robotic space shuttle circling Earth |work=Spaceflight Now |first=Stephen |last=Clark |date=5 March 2011 |access-date=20 October 2016 |archive-url=https://web.archive.org/web/20161021070132/http://www.spaceflightnow.com/atlas/av026/ |archive-date=21 October 2016 |url-status=live}} The mission was classified and described by the U.S. military as an effort to test new space technologies.{{cite news |url=http://www.space.com/11031-secret-x37b-space-plane-launch.html |title=Secretive X-37B Space Plane Launches on New Mystery Mission |work=Space.com |first=Mike |last=Wall |date=5 March 2011 |access-date=8 April 2012 |archive-url=https://web.archive.org/web/20120403131121/http://www.space.com/11031-secret-x37b-space-plane-launch.html |archive-date=3 April 2012 |url-status=live}} On 29 November 2011, the U.S. Air Force announced that it would extend USA-226 beyond the 270-day baseline duration.{{cite news |url=http://www.spaceflightnow.com/news/n1111/29otv2/ |title=Military space shuttle receives mission extension |work=Spaceflight Now |first=Stephen |last=Clark |date=29 November 2011 |access-date=1 December 2011 |archive-url=https://web.archive.org/web/20111201190421/http://www.spaceflightnow.com/news/n1111/29otv2/ |archive-date=1 December 2011 |url-status=live}} In April 2012, General William L. Shelton of the Air Force Space Command declared the ongoing mission a "spectacular success".{{cite news |url=http://www.nbcnews.com/id/47361223/ |title=Air Force's secret X-37B a 'spectacular success' |work=NBC News |first=Leonard |last=David |date=9 May 2012 |access-date=10 May 2012 |archive-url=https://web.archive.org/web/20160304084657/http://www.nbcnews.com/id/47361223/ |archive-date=4 March 2016 |url-status=dead}}

On 30 May 2012, the Air Force stated that the X-37B would land at Vandenberg AFB in June 2012.{{cite news |url=https://www.vandenberg.spaceforce.mil/?id=123304066 |title=Preparations underway for X-37B landing |publisher=U.S. Air Force |agency=30th Space Wing Public Affairs |date=30 May 2012 |access-date=1 June 2012 |url-status=live |archive-url=https://web.archive.org/web/20120602032208/http://www.vandenberg.af.mil/news/story.asp?id=123304066 |archive-date=2 June 2012}}{{cite news |url=http://www.space.com/15926-secret-x37b-space-plane-landing.html |title=Air Force's Secretive X-37B Space Plane Will Land Soon |work=Space.com |first=Leonard |last=David |date=30 May 2012 |access-date=2 June 2012 |archive-url=https://web.archive.org/web/20120602002229/http://www.space.com/15926-secret-x37b-space-plane-landing.html |archive-date=2 June 2012 |url-status=live}} The spacecraft landed autonomously on 16 June 2012, having spent {{time interval|5 March 2011 22:46|16 June 2012 12:48|show=dh}} in space.{{cite news |url=http://santamariatimes.com/news/local/military/vandenberg/x--b-lands-this-morning-at-vandenberg-afb/article_31f5827c-b7bc-11e1-80b2-0019bb2963f4.html |title=X-37B lands this morning at Vandenberg AFB |work=Santa Maria Times |date=16 June 2012 |archive-url=https://web.archive.org/web/20141025130026/http://santamariatimes.com/news/local/military/vandenberg/x--b-lands-this-morning-at-vandenberg-afb/article_31f5827c-b7bc-11e1-80b2-0019bb2963f4.html |archive-date=25 October 2014 |url-status=live}}{{cite news |url=http://www.space.com/16110-secret-x37b-space-plane-landing.html |title=Air Force's secret X-37B space plane lands in Calif. after mystery mission |work=Space.com |first=Mike |last=Wall |date=16 June 2012 |access-date=16 June 2012 |archive-url=https://web.archive.org/web/20120616171905/http://www.space.com/16110-secret-x37b-space-plane-landing.html |archive-date=16 June 2012 |url-status=live}}

{{main|OTV-3}}

The third mission and second flight of the first X-37B, OTV-3 was originally scheduled to launch on 25 October 2012,{{cite news |url=http://spaceflightnow.com/atlas/av034/stacking.html |title=Another Atlas 5 readied to launch mini space shuttle |work=Spaceflight Now |first=Justin |last=Ray |date=18 September 2012 |access-date=4 October 2012 |archive-url=https://web.archive.org/web/20120922093129/http://spaceflightnow.com/atlas/av034/stacking.html |archive-date=22 September 2012 |url-status=live}} but was postponed because of an engine issue with the Atlas V launch vehicle.{{cite news |url=http://www.airforcemag.com/DRArchive/Pages/2012/October%202012/October%2025%202012/X-37BLaunchDelayed.aspx |title=X-37B Launch Delayed |work=Air Force Magazine |first=Amy |last=McCullough |date=25 October 2012 |access-date=11 December 2012 |archive-url=https://web.archive.org/web/20140220190719/http://www.airforcemag.com/DRArchive/Pages/2012/October%202012/October%2025%202012/X-37BLaunchDelayed.aspx |archive-date=20 February 2014}} It was successfully launched from Cape Canaveral SLC-41 on 11 December 2012 at 18:03 UTC.{{cite news |url=http://www.airforcetimes.com/news/2012/12/gannett-air-force-x37b-mini-shuttle-secrecy-120912/ |title=AF's X-37B mini-shuttle shrouded in secrecy |work=Air Force Times |agency=Florida Today |first=Todd |last=Halvorson |date=9 December 2012 |access-date=10 December 2012 |archive-url=https://archive.today/20130116131111/http://www.airforcetimes.com/news/2012/12/gannett-air-force-x37b-mini-shuttle-secrecy-120912/ |archive-date=16 January 2013 |url-status=dead}}{{cite news |url=http://www.universetoday.com/98937/air-forces-secret-x-37b-space-plane-launches-on-third-mission/ |title=Air Force's Secret X-37B Space Plane Launches on Third Mission |work=Universe Today |first=Nancy |last=Atkinson |date=11 December 2012 |access-date=11 December 2012 |archive-url=https://web.archive.org/web/20121214075442/http://www.universetoday.com/98937/air-forces-secret-x-37b-space-plane-launches-on-third-mission/ |archive-date=14 December 2012 |url-status=live}}{{cite news |url=http://www.space.com/18592-secretive-x37b-space-plane-delay.html |title=New Delay for Mysterious Military Space Plane Launch |work=Space.com |first=Leonard |last=David |date=21 November 2012 |access-date=26 November 2012 |archive-url=https://web.archive.org/web/20121127170956/http://www.space.com/18592-secretive-x37b-space-plane-delay.html |archive-date=27 November 2012 |url-status=live}} Once in orbit, the spacecraft was designated USA-240.{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=2012-071A |title=NSSDC ID: 2012-071A |work=National Space Science Data Center |publisher=NASA |access-date=24 December 2012}} {{PD-notice}}{{cite news |url=https://www.af.mil/News/Article-Display/Article/109994/air-force-launches-3rd-x-37b-orbital-test-vehicle/ |title=Air Force launches 3rd X-37B Orbital Test Vehicle |publisher=U.S. Air Force |first=Eric |last=Badger |date=11 December 2012 |archive-url=https://web.archive.org/web/20140626043058/http://www.af.mil/News/ArticleDisplay/tabid/223/Article/109994/air-force-launches-3rd-x-37b-orbital-test-vehicle.aspx |archive-date=26 June 2014 |url-status=live}} Landing occurred at Vandenberg AFB on 17 October 2014 at 16:24 UTC, after a total time in orbit of {{time interval|11 December 2012 18:03|17 October 2014 16:24|show=dh}}.

{{main|OTV-4}}

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. The X-37B launched on an Atlas V rocket from Cape Canaveral SLC-41 on 20 May 2015 at 15:05 UTC.{{cite news |url=https://spaceflightnow.com/2015/05/20/recap-story-x-37b-embarks-on-fourth-voyage-in-space/ |title=Recap story: X-37B spaceplane embarks on fourth voyage in orbit |work=Spaceflight Now |first=Justin |last=Ray |date=20 May 2015 |access-date=11 October 2016 |archive-url=https://web.archive.org/web/20161012152349/https://spaceflightnow.com/2015/05/20/recap-story-x-37b-embarks-on-fourth-voyage-in-space/ |archive-date=12 October 2016 |url-status=live}} Objectives included a test of Aerojet Rocketdyne's XR-5A Hall-effect thruster in support of the Advanced Extremely High Frequency communications satellite program,{{cite news |url=http://spaceflightnow.com/2015/04/27/x-37b-launch-date-firms-up-as-new-details-emerge-about-experiment/ |title=X-37B launch date firms up as new details emerge about experiment |work=Spaceflight Now |first=Justin |last=Ray |date=27 April 2015 |access-date=27 April 2015 |archive-url=https://web.archive.org/web/20150429203122/http://spaceflightnow.com/2015/04/27/x-37b-launch-date-firms-up-as-new-details-emerge-about-experiment/ |archive-date=29 April 2015 |url-status=live}}{{cite press release |url=http://www.rocket.com/article/aerojet-rocketdyne%E2%80%99s-modified-xr-5-hall-thruster-demonstrates-successful-orbit-operation |title=Aerojet Rocketdyne's Modified XR-5 Hall Thruster Demonstrates Successful On-Orbit Operation |publisher=Aerojet Rocketdyne |date=1 July 2015 |access-date=11 October 2016 |archive-url=https://web.archive.org/web/20150709024047/http://www.rocket.com/article/aerojet-rocketdyne%E2%80%99s-modified-xr-5-hall-thruster-demonstrates-successful-orbit-operation |archive-date=9 July 2015 |url-status=live}} and a NASA investigation on the performance of various materials in space{{cite news |url=http://www.space.com/29448-x37b-space-plane-launches-fourth-mission.html |title=US Air Force Launches X-37B Space Plane on 4th Mystery Mission |work=Space.com |first=Mike |last=Wall |date=20 May 2015 |access-date=21 May 2015 |archive-url=https://web.archive.org/web/20150521181418/http://www.space.com/29448-x37b-space-plane-launches-fourth-mission.html |archive-date=21 May 2015 |url-status=live}} for at least 200 days. The vehicle spent what was then a record-breaking {{time interval|20 May 2015 15:05|7 May 2017 11:47|show=dh}} in orbit before landing at Kennedy Space Center's Shuttle Landing Facility on 7 May 2017 at 11:47 UTC.{{cite news |url=https://spaceflightnow.com/2017/05/07/x-37b-spaceplane-returns-to-earth-and-makes-precision-autopilot-landing/ |title=X-37B spaceplane returns to Earth and makes autopilot landing in Florida |work=Spaceflight Now |first=Justin |last=Ray |date=7 May 2017 |access-date=7 May 2017 |archive-url=https://web.archive.org/web/20170508013454/https://spaceflightnow.com/2017/05/07/x-37b-spaceplane-returns-to-earth-and-makes-precision-autopilot-landing/ |archive-date=8 May 2017 |url-status=live}}{{cite news |url=http://www.cnn.com/2017/05/07/us/air-force-x-37b-landing-trnd/index.html |title=Air Force's mysterious space plane lands, wakes up Florida |work=CNN |first=Amanda |last=Jackson |date=8 May 2017 |access-date=12 July 2017 |archive-url=https://web.archive.org/web/20170715191334/http://www.cnn.com/2017/05/07/us/air-force-x-37b-landing-trnd/index.html |archive-date=15 July 2017 |url-status=live}}

{{main|OTV-5}}

The fifth X-37B mission, designated USA-277 in orbit, was launched from Kennedy Space Center Launch Complex 39A on 7 September 2017 at 14:00 UTC, just before the arrival of Hurricane Irma.{{cite news |url=https://www.theverge.com/2017/9/7/16262226/spacex-live-stream-time-falcon-9-launch-x-37b-otv-5 |title=SpaceX launches Air Force's spaceplane just before Hurricane Irma reaches Florida |work=The Verge |last=Grush |first=Loren |date=7 September 2017 |access-date=7 September 2017 |archive-url=https://web.archive.org/web/20170907112227/https://www.theverge.com/2017/9/7/16262226/spacex-live-stream-time-falcon-9-launch-x-37b-otv-5 |archive-date=7 September 2017 |url-status=live}}{{cite news |url=https://www.nasaspaceflight.com/2017/09/spacex-first-x-37b-launch-falcon-9/ |title=SpaceX launches first X-37B launch with a Falcon 9 |website=NASASpaceFlight.com |last=Graham |first=William |date=7 September 2017 |access-date=7 September 2017 |archive-url=https://web.archive.org/web/20170907052033/https://www.nasaspaceflight.com/2017/09/spacex-first-x-37b-launch-falcon-9/ |archive-date=7 September 2017 |url-status=live}} The launch vehicle was a Falcon 9 rocket, and a number of small satellites also shared the ride. The spacecraft was inserted at a higher inclination orbit than previous missions, further expanding the X-37B's envelope.{{cite web |url=http://www.afspc.af.mil/News/Article-Display/Article/1297016/air-force-preparing-to-launch-fifth-orbital-test-vehicle-mission/ |title=Air Force preparing to launch fifth Orbital Test Vehicle mission |publisher=Air Force Space Command |agency=Air Force News Service |date=31 August 2017 |access-date=1 September 2017 |archive-url=https://web.archive.org/web/20170908011804/http://www.afspc.af.mil/News/Article-Display/Article/1297016/air-force-preparing-to-launch-fifth-orbital-test-vehicle-mission/ |archive-date=8 September 2017 |url-status=dead}} During the flight, the spacecraft modified its orbit using an on-board propulsion system.{{cite news |last=David |first=Leonard |date=15 August 2018 |title=Mysterious X-37B Military Space Plane Nears 1 Year in Orbit |url=https://www.space.com/41507-x-37b-space-plane-nears-one-year-orbit.html |work=Space.com |access-date=17 August 2018 |archive-url=https://web.archive.org/web/20180817091219/https://www.space.com/41507-x-37b-space-plane-nears-one-year-orbit.html |archive-date=17 August 2018 |url-status=live}} 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.{{cite web |url=https://www.kirtland.af.mil/Portals/52/documents/ASETSII.pdf?ver=2017-08-10-125001-450 |title=Advanced Structurally Embedded Thermal Spreader II (ASETS-II) |publisher=Air Force Research Laboratory |date=10 August 2017 |access-date=27 August 2017 |archive-url=https://web.archive.org/web/20170827213819/http://www.kirtland.af.mil/Portals/52/documents/ASETSII.pdf?ver=2017-08-10-125001-450 |archive-date=27 August 2017 |url-status=live}} The mission was completed with the vehicle landing at the Shuttle Landing Facility on 27 October 2019 at 07:51 UTC.{{cite news |url=https://spaceflightnow.com/2019/10/27/u-s-militarys-x-37b-spaceplane-lands-in-florida/ |title=U.S. military's X-37B spaceplane lands in Florida |work=Spaceflight Now |first=Stephen |last=Clark |date=27 October 2019 |access-date=28 October 2019}}{{cite news |url=https://www.usatoday.com/story/tech/2019/10/27/x-37-b-spaceplane-returned-earth-after-780-days-orbit/2478740001/ |title=U.S. Airforce's X-37B returns to Earth with a 'boom' and a new record for spaceflight |work=USA Today |agency=Florida Today |first=J. D. |last=Gallop |date=27 October 2019 |access-date=28 October 2019}}

File:X-37B concludes sixth mission (221111-F-XX000-0002).jpg at KSC on 12 November 2022, the 909th day of the OTV-6 (USA-299) mission]]

{{main|OTV-6}}

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.{{cite news |url=https://www.nasaspaceflight.com/2020/05/ula-atlas-v-launch-sixth-x-37b/ |title=ULA Atlas V launches sixth mission for X-37B spaceplane |publisher=NASASpaceFlight.com |last=Graham |first=William |date=17 May 2020}} 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.{{cite web | url=https://taskandpurpose.com/news/space-forces-x-37b-space-plane-900-days-orbit/ | title=Space Force's secretive X-37B plane has spent more than 900 days in orbit | date=6 November 2022}} 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.{{cite news |url=https://spaceflightnow.com/2020/05/06/payloads-revealed-for-next-flight-of-x-37b-military-spaceplane/ |title=Payloads revealed for next flight of X-37B military spaceplane |publisher=Spaceflight Now |first=Stephen |last=Clark |date=6 May 2020 |access-date=7 May 2020}}{{cite web |url=https://www.spaceforce.mil/News/Article/2177702/next-x-37b-orbital-test-vehicle-scheduled-to-launch|title=Next X-37B Orbital Test Vehicle Scheduled to Launch |publisher=U.S. Space Force |date=6 May 2020 |access-date=8 September 2020}}

The X-37B released a small, {{cvt|136|kg}} satellite named FalconSat-8 (USA-300) around 28 May 2020.{{cite news|url=https://planet4589.org/space/jsr/back/news.779.txt|title=Jonathan's Space Report, No. 779|publisher=Jonathan's Space Report|first=Jonathan|last=McDowell|issue=779|date=14 June 2020|access-date=22 January 2022}} 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:{{cite news |url=https://spaceflightnow.com/2020/05/17/upgraded-x-37b-spaceplane-rockets-into-orbit-aboard-atlas-5-launcher/|title=Upgraded X-37B spaceplane rockets into orbit aboard Atlas 5 launcher |publisher=Spaceflight Now |first=Stephen |last=Clark |date=17 May 2020 |access-date=8 September 2020}}

• 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.

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

{{main|OTV-7}}

The fourth flight of secondDutchSpace. [https://twitter.com/DutchSpace/status/1730114986519806372 "OTV-7 image analysis"]. X, 30 November 2023. X-37B and seventh overall X-37B mission was planned to be launched on SpaceX's Falcon Heavy on 12 December 2023.{{Cite web |url=https://news.satnews.com/2023/12/10/update-spacex-falcon-heavy-launch-on-hold-for-ussf-52-mission/ |title=UPDATE: SpaceX Falcon Heavy launch on hold for USSF-52 mission |date=December 10, 2023 | website=satnews.com |author=| access-date=December 10, 2023}} It was rescheduled for 28 December 2023,{{cite tweet|user=SpaceX|number=1735837375744651476|title=Now targeting no earlier than Thursday, December 28 for Falcon Heavy to launch USSF-52 to orbit from Florida → }} {{better source|date=February 2024}} when it was successfully launched at 8:07 pm EST (01:07:00 UTC on December 29).Erwin, Sandra. [https://spacenews.com/spacex-launches-u-s-military-spaceplane-on-falcon-heavy-rocket/ "SpaceX launches U.S. military spaceplane on Falcon Heavy rocket"]. Space News, 28 December 2023. The orbit is higher than any spaceplane, in a highly elliptical HEO orbit.

In October 2024, OTV-7 was due to undertake aerobraking maneuvers to safely dispose of its service module.{{cite news |last1=Hitchens |first1=Theresa |url=https://breakingdefense.com/2024/10/secretive-space-plane-x-37b-to-test-first-of-a-kind-maneuvers-for-shifting-orbits/ |title=Secretive space plane X-37B to test 'first of a kind' maneuvers for shifting orbits |website=Breaking Defense |date=October 10, 2024}} The mission ended on with landing at Vandenberg Space Force Base on 7 March 2025 at 07:22 UTC.{{cite web|url=https://www.spaceforce.mil/News/Article-Display/Article/4112259/x-37b-orbital-test-vehicle-concludes-seventh-successful-mission/| title= X-37B Orbital Test Vehicle concludes seventh successful mission

|last=Secretary of Air Force Public Affairs|date=2025-03-07|access-date=2025-03-07|website=spaceforce.mil}}

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.{{cite web |url=http://www.designation-systems.net/dusrm/app4/x-37.html |title=Boeing X-37 / X-40 |work=Designation-Systems.net |first=Andreas |last=Parsch |date=November 2009 |access-date=2 August 2012 |archive-url=https://web.archive.org/web/20120510060556/http://designation-systems.net/dusrm/app4/x-37.html |archive-date=10 May 2012 |url-status=live}}

The X-37B is a modified version of the NASA X-37A, built for the U.S. Air Force. Two have been built and used for multiple orbital missions.

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.{{cite news |url=http://www.space.com/13230-secretive-37b-space-plane-future-astronauts.html |title=Secretive X-37B US Space Plane Could Evolve to Carry Astronauts |work=Space.com |first=Leonard |last=David |date=7 October 2011 |access-date=10 October 2011 |archive-url=https://web.archive.org/web/20111009210521/http://www.space.com/13230-secretive-37b-space-plane-future-astronauts.html |archive-date=9 October 2011 |url-status=live}} In this role, Boeing's X-37C could potentially compete with the corporation's CST-100 Starliner commercial space capsule.{{cite web |url=http://www.citizensinspace.org/2012/03/boeing-vs-boeing/ |title=Boeing vs. Boeing |publisher=Citizens in Space |date=25 March 2012 |access-date=21 December 2012 |archive-url=https://web.archive.org/web/20130406101210/http://www.citizensinspace.org/2012/03/boeing-vs-boeing/ |archive-date=6 April 2013 |url-status=live}} {{As of|2024|post=}}, with NASA selecting Starliner and SpaceX Crew Dragon, there has been no further announcement to develop X-37C.{{cite press release|url=http://boeing.mediaroom.com/index.php?s=20295&item=1054|title=NASA Selects Boeing for American Recovery and Reinvestment Act Award to Study Crew Capsule-based Design|publisher=Boeing|first1=Edmund G.|last1=Memi|first2=Michael N.|last2=Gold|date=February 2, 2010|access-date=May 9, 2014|archive-date=March 3, 2016|archive-url=https://web.archive.org/web/20160303235336/http://boeing.mediaroom.com/index.php?s=20295&item=1054|url-status=live}}{{cite news|url=http://aviationweek.com/awin/five-vehicles-vie-future-us-human-spaceflight|title=Five Vehicles Vie For Future Of U.S. Human Spaceflight|publisher=Aviation Week|first=Frank|last=Morring, Jr.|date=April 25, 2011|archive-url=https://web.archive.org/web/20140509041748/http://aviationweek.com/awin/five-vehicles-vie-future-us-human-spaceflight|archive-date=May 9, 2014|url-status=live|quote="the CCDev-2 awards... went to Blue Origin, Boeing, Sierra Nevada Corp. and Space Exploration Technologies Inc. (SpaceX)}}{{cite news|url=http://spacenews.com/civil/120803-boeing-spacex-sierra-ccicap.html|archive-url=https://archive.today/20130104234510/http://spacenews.com/civil/120803-boeing-spacex-sierra-ccicap.html|url-status=dead|archive-date=January 4, 2013|title=Boeing, SpaceX and Sierra Nevada Win CCiCAP Awards |publisher=SpaceNews|date=August 3, 2012}}{{cite news|url=https://blogs.nasa.gov/commercialcrew/2014/09/16/boeing-and-spacex-selected-to-build-americas-new-crew-space-transportation-system/|title=Boeing and SpaceX Selected to Build America's New Crew Space Transportation System|publisher=NASA|date=September 16, 2014|access-date=April 6, 2015|archive-date=May 22, 2017|archive-url=https://web.archive.org/web/20170522164333/https://blogs.nasa.gov/commercialcrew/2014/09/16/boeing-and-spacex-selected-to-build-americas-new-crew-space-transportation-system/|url-status=live}} {{PD-notice}}

{{multiple image |align=right |direction=vertical |width=220 |image1=X 37B OTV-2 01.jpg |image2=X 37B OTV-2 02.jpg |footer=Three-view plans of the X-37B}}

{{aircraft specs

|ref=USAF, Boeing,{{cite web |url=http://www.boeing.com/boeing/defense-space/ic/sis/x37b_otv/x37b_otv.page |title=X-37B Orbital Test Vehicle |work=Boeing.com |access-date=6 December 2010 |archive-url=https://web.archive.org/web/20150321121050/http://www.boeing.com/boeing/defense-space/ic/sis/x37b_otv/x37b_otv.page |archive-date=21 March 2015}} Air & Space Magazine,{{cite journal |url=http://www.airspacemag.com/space/space-shuttle-jr-9563914/?all |title=Space Shuttle Jr. |journal=Air & Space Magazine |first=Michael |last=Klesius |date=January 2010 |access-date=19 October 2014 |archive-url=https://web.archive.org/web/20141019121501/http://www.airspacemag.com/space/space-shuttle-jr-9563914/?all |archive-date=19 October 2014 |url-status=live}} and Phys.org{{cite news |url=https://phys.org/news/2010-04-air-robotic-winged-space-plane.html |title=Air Force to launch robotic winged space plane |website=Phys.org |agency=Associated Press |first=John |last=Antczak |date=3 April 2010 |access-date=16 February 2013 |archive-url=https://web.archive.org/web/20120104194826/http://www.physorg.com/news189528362.html |archive-date=4 January 2012 |url-status=live}}{{Cite web |author1=Leonard David |date=2010-11-22 |title=Secretive Air Force X-37B Robotic Space Plane May Be Nearing Mission's End |url=https://www.space.com/9575-secretive-air-force-37b-robotic-space-plane-nearing-mission.html |access-date=2022-04-04 |website=Space.com |language=en}}

|prime units?=imp

|crew= none

|capacity=227 kg

|length ft=29

|length in=3

|length note=

|span ft=14

|span in=11

|span note=

|height ft=9

|height in=6

|height note=

|wing area sqm=

|wing area sqft=

|wing area note=

|airfoil=

|empty weight kg=

|empty weight lb=

|empty weight note=

|max takeoff weight lb=11000

|max takeoff weight note=

|fuel capacity=

|more general=

• Electrical power: Gallium arsenide solar cells with lithium-ion batteries
• Payload bay: {{convert|7|xx|4|ft|abbr=on}}

|eng1 number=1

|eng1 name=

|eng1 type=rocket engine

|eng1 kn=

|eng1 note=

|more performance=*Orbital speed: {{convert|28044|km/h|mph|order=flip|abbr=on}}{{cite web |url=http://www.satobs.org/seesat/May-2012/0236.html |title=Re: X-37B OTV 2-1 search elements |work=Satobs.org |first=Ted |last=Molczan |date=22 May 2012 |access-date=2 June 2012 |archive-url=https://web.archive.org/web/20140108090854/http://www.satobs.org/seesat/May-2012/0236.html |archive-date=8 January 2014 |url-status=live}}

• Orbit: Low Earth orbit to high Earth orbit
• Orbital time: 270 days (design){{cite news |url=http://www.timesonline.co.uk/tol/news/world/us_and_americas/article7106714.ece |title=Launch of secret US space ship masks even more secret launch of new weapon |work=The Times |first=Michael |last=Evans |date=24 April 2010 |access-date=25 April 2010 |archive-url=https://web.archive.org/web/20100529151709/http://www.timesonline.co.uk/tol/news/world/us_and_americas/article7106714.ece |archive-date=29 May 2010}}{{refn|This figure is based on pre-launch design estimates; it does not reflect the spacecraft's actual performance capacity.|group=N}} 908 days (demonstrated){{cite web | url=https://spacenews.com/x-37b-space-plane-completes-its-sixth-mission-lands-after-nearly-30-months-in-orbit/ | title=X-37B spaceplane completes its sixth mission, lands after nearly 30 months in orbit | date=12 November 2022}}

}}

{{Portal|Spaceflight}}

• 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

{{Reflist|group=N}}

{{Reflist|refs=

{{cite news|url=http://www.flightglobal.com/news/articles/us-air-force39s-shadowy-space-plane-lands-after-674-days-in-404904/|title=US Air Force's shadowy space plane lands after 674 days in orbit|work=Flight Global|first=Dan|last=Parsons|date=17 October 2014|access-date=18 October 2014|archive-url=https://web.archive.org/web/20141018141846/http://www.flightglobal.com/news/articles/us-air-force39s-shadowy-space-plane-lands-after-674-days-in-404904/|archive-date=18 October 2014|url-status=live}}

{{cite news|url=https://www.theguardian.com/us-news/2014/oct/17/secret-space-plane-us-air-force-x37b-lands-california|title=Secret space plane lands at US Air Force base after unknown two-year mission|newspaper=The Guardian|agency=Associated Press|date=17 October 2014|access-date=17 October 2014|archive-url=https://web.archive.org/web/20141017193201/http://www.theguardian.com/us-news/2014/oct/17/secret-space-plane-us-air-force-x37b-lands-california|archive-date=17 October 2014|url-status=live}}

{{cite news|url=http://www.space.com/27427-x37b-space-plane-air-force-landing.html|title=X-37B Military Space Plane Lands After Record-Shattering Secret Mission|publisher=Space.com |first=Mike|last=Wall|date=17 October 2014|access-date=17 October 2014|archive-url=https://web.archive.org/web/20141019120909/http://www.space.com/27427-x37b-space-plane-air-force-landing.html|archive-date=19 October 2014|url-status=live}}

}}

{{refbegin}}

• {{Cite book |last=Miller |first=Jay |year=2001 |title=The X-Planes: X-1 to X-45 |location=Hinckley, UK |publisher=Midland |isbn=978-1-85780-109-5}}
• {{Cite book |last=Yenne |first=Bill |year=2005 |title=The Story of the Boeing Company |location=Minneapolis, Minn. |publisher=Zenith |isbn=978-0-7603-2333-5}}

{{refend}}

{{refbegin}}

• {{Cite book |last=Bentley |first=Matthew A. |year=2008 |title=Spaceplanes: From Airport to Spaceport |location=New York |publisher=Springer |isbn=978-0-387-76509-9 |bibcode=2009sfas.book.....B}}
• {{Cite book |last=Gump |first=David P. |year=1989 |title=Space Enterprise: Beyond NASA |location=Westport, Connecticut |publisher=Praeger |isbn=978-0-275-93314-2}}

{{refend}}

{{Commons category|Boeing X-37}}

• [https://www.af.mil/About-Us/Fact-Sheets/Display/Article/104539/x-37b-orbital-test-vehicle/ X-37 Orbital Test Vehicle fact sheet] from the U.S. Air Force
• [https://web.archive.org/web/20150330221458/http://www.boeing.com/boeing/defense-space/ic/sis/x37b_otv/x37b_otv.page X-37B Orbital Test Vehicle page] at Boeing.com
• [http://www.nasa.gov/centers/marshall/news/background/facts/x37facts2.html X-37 fact sheet] {{Webarchive |url=https://web.archive.org/web/20121024120833/http://www.nasa.gov/centers/marshall/news/background/facts/x37facts2.html |date=24 October 2012}} at NASA.gov
• {{Cite web |last=Machi |first=Vivienne |date=February 21, 2025 |title=How The X-37B Is Shaping The Future Of The U.S. Space Force |url=https://aviationweek.com/space/budget-policy-regulation/how-x-37b-shaping-future-us-space-force?elq2=cab5acf5ad4f41fcb497f92a2b000757&sp_eh=8cc27749f183b99591f0c95a2858b11407066243cbe756e8e296e10fe7a5278f&elq2=cab5acf5ad4f41fcb497f92a2b000757&sp_eh=8cc27749f183b99591f0c95a2858b11407066243cbe756e8e296e10fe7a5278f&utm_emailname=AW_News_AerospaceDigest_NL_02212025&utm_rid=CPEN1000001583767 |access-date=2025-02-21 |website= Aviation Week Network (aviationweek.com)}}

{{X-37B flights}}

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{{DEFAULTSORT:X-37}}

X-37

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