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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Boeing X-37 | 3/4 | https://en.wikipedia.org/wiki/Boeing_X-37 | reference | science, encyclopedia | 2026-05-05T12:38:23.150238+00:00 | kb-cron |
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 29 feet (8.8 m) in length, and features two angled tail fins. The X-37 launches atop an Atlas V 501 or a SpaceX Falcon 9 or Falcon Heavy rocket. The spaceplane is designed to operate in a speed range of up to Mach 25 on its reentry. The technologies demonstrated in the X-37 include an improved thermal protection system, enhanced avionics, an autonomous guidance system and an advanced airframe. The spaceplane's thermal protection system is built upon previous generations of atmospheric reentry spacecraft, incorporating silica ceramic tiles. The X-37's avionics suite was used by Boeing to develop its CST-100 crewed spacecraft. 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. The X-37 for NASA was to be powered by one Aerojet AR2-3 engine using storable propellants, providing thrust of 6,600 pounds-force (29.4 kN). 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. This was reportedly changed to a hypergolic nitrogen-tetroxide/hydrazine propulsion system. 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 and the U.S. space shuttle, which had automatic landing capability by the mid-1990s, but never tested it. The X-37 is the smallest and lightest orbital spaceplane flown to date; it has a launch mass of around 11,000 pounds (5,000 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".
== 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.
=== OTV-1 ===
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. 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 249 by 262 miles (401 by 422 km). 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. 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. As scheduled, the X-37B was de-orbited, reentered Earth's atmosphere, and landed successfully at Vandenberg SFB on 3 December 2010, at 09:16 UTC, 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 224 days and 9 hours in space. OTV-1 suffered a tire blowout during landing and sustained minor damage to its underside.
=== OTV-2 ===
The second X-37B launched on its inaugural mission, designated OTV-2/USA-226, aboard an Atlas V rocket from Cape Canaveral SLC-41 on 5 March 2011 at 22:46 UTC. The mission was classified and described by the U.S. military as an effort to test new space technologies. On 29 November 2011, the U.S. Air Force announced that it would extend USA-226 beyond the 270-day baseline duration. In April 2012, General William L. Shelton of the Air Force Space Command declared the ongoing mission a "spectacular success". On 30 May 2012, the Air Force stated that the X-37B would land at Vandenberg AFB in June 2012. The spacecraft landed autonomously on 16 June 2012, having spent 468 days and 14 hours in space.
=== OTV-3 ===
The third mission and second flight of the first X-37B, OTV-3 was originally scheduled to launch on 25 October 2012, but was postponed because of an engine issue with the Atlas V launch vehicle. It was successfully launched from Cape Canaveral SLC-41 on 11 December 2012 at 18:03 UTC. Once in orbit, the spacecraft was designated USA-240. Landing occurred at Vandenberg AFB on 17 October 2014 at 16:24 UTC, after a total time in orbit of 674 days and 22 hours.
=== 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. Objectives included a test of Aerojet Rocketdyne's XR-5A Hall-effect thruster in support of the Advanced Extremely High Frequency communications satellite program, and a NASA investigation on the performance of various materials in space for at least 200 days. The vehicle spent what was then a record-breaking 717 days and 20 hours in orbit before landing at Kennedy Space Center's Shuttle Landing Facility on 7 May 2017 at 11:47 UTC.
=== OTV-5 ===