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An artist’s impression of the X-37, made in 1999
April 7, 2006 (drop test)
Development and testing
NASA/DARPA (X-37A) USAF (X-37B)
The Boeing X-37 Advanced Technology Demonstrator is an unpiloted demonstration spaceplane that is intended to test future spaceflight technologies while in orbit and during atmospheric reentry. It is a reusable robotic spacecraft that is a 120 percent–scaled derivative of the X-40A. The X-37 began as a NASA project in 1999, then was transferred to the US Department of Defense in 2004. The X-37 had its first flight as a drop test on April 7, 2006 at Edwards AFB. The spacecraft was launched on April 22, 2010 to begin a United States Air Force mission.
Design and development
In 1999, NASA selected Boeing Integrated Defense Systems to design and develop the vehicle, which was built by the California branch of Boeing’s Phantom Works. Over a four year period NASA contributed $109 million, the Air Force $16 million, and Boeing $67 million to the project. At the end of 2002, a new $301 million contract was awarded to Boeing in the framework of NASA’s Space Launch Initiative.
The X-37 was transferred from NASA to the Defense Advanced Research Projects Agency on September 13, 2004. The program has become a classified project, though it is not known whether DARPA will maintain this status for the project. NASA’s spaceflight program may be centered around the Crew Exploration Vehicle, while DARPA will promote the X-37 as part of the independent space policy which the Department of Defense has pursued since the Challenger disaster.
This vehicle has the potential to become the United States’ first operational military spaceplane, after the cancellation of Dyna-Soar in 1963. It is expected to operate in a velocity range of up to Mach 25 on reentry. Among the technologies to be demonstrated with the X-37 are improved thermal protection systems, avionics, the autonomous guidance system, and an advanced airframe. The on-board engine is the Rocketdyne AR-2/3, which is fueled by hydrogen peroxide and JP-8.
The X-37 was originally designed to be carried into orbit in the Space Shuttle cargo bay, but underwent redesign for launch on a Delta IV or comparable rocket after it was determined that a shuttle flight would be uneconomical.
The X-37’s aerodynamic design was derived from the Space Shuttle, hence the X-37 has a similar lift-to-drag ratio, and a lower cross range at high altitudes and mach numbers than the Hypersonic Technology Vehicle.
The 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. Most of the thermal protection tiles were ‘fake’, made of inexpensive foam rather than ceramic; a smaller number of the X-37’s tiles were actual TPS tiles, and TPS blankets were used in areas where heating would not have been severe enough to require tiles.
On September 2, 2004, it was reported that for its initial atmospheric drop tests, the X-37 would be launched from the Scaled Composites White Knight, a high-altitude research aircraft better known for launching Scaled’s SpaceShipOne.
On June 21, 2005, the X-37 completed a captive-carry flight underneath the White Knight at Mojave Spaceport, Mojave, California. Through the second half of 2005, the X-37 underwent structural upgrades including reinforcement of the nose wheel supports. Further captive-carry flight tests and the first drop test were expected mid-February 2006.
March 10, 2006 was scheduled for X-37’s public debut—its first free flight, to be broadcast live on NASA TV. But an Arctic storm covered the area, dropping snow on the Mojave. The X-37 remained in the airport’s Hangar 77, while an occasional engineer popped out onto the flight line to snap pictures of the snow. The next attempt at a flight, on March 15, 2006, was canceled due to high winds. On March 24, 2006, the X-37 flew, but a data link failure prevented the free flight and the vehicle returned to the ground still docked with its White Knight carrier.
Following an extended down time while the vehicle was repaired, the program moved from Mojave to Air Force Plant 42 (KPMD) in Palmdale, California for the remainder of the flight test program. White Knight continued to be based at Mojave, but would ferry over to Plant 42 when flights were scheduled. Five additional flights were performed, at least one of which is believed to have been a free flight with a successful landing.
X-37B Orbital Test Vehicle
On November 17, 2006 the U.S. Air Force announced it would develop the X-37B from the NASA X-37A. The Air Force version is designated X-37B Orbital Test Vehicle (OTV). The OTV program builds on industry and government investments by DARPA, NASA and the Air Force. The X-37B effort will be led by the Air Force Rapid Capabilities Office and includes partnerships with NASA and the Air Force Research Laboratory. Boeing is the prime contractor for the OTV program. The X-37B can remain in orbit for up to 270 days at a time.
The Secretary of the Air Force states the OTV program will 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 following the Columbia accident, it was transferred to a Delta II 7920. It was subsequently transferred to a shrouded configuration on the Atlas V following concerns over the unshrouded spacecraft’s aerodynamic properties during launch.
The first orbital flight of the X-37B, named OTV-1, was launched on an Atlas V rocket at Cape Canaveral Air Force Station, Florida on April 22, 2010 at 23:58 GMT. The spacecraft was placed into low Earth orbit for testing, then will be de-orbited for landing.
Following their missions, X-37B spacecraft are to land on a runway at Vandenberg Air Force Base, California with Edwards Air Force Base as an alternate site. A second X-37B is being manufactured for a test mission scheduled for 2011
The original AR2-3 main engines were fueled by JP-8 (a kerosene-like military jet fuel) and hydrogen peroxide; now uses hypergolic nitrogen tetroxide/hydrazine. The maneuvering engines are fueled by hydrogen peroxide. An experiment bay is available for payloads.
- Crew: None
- Length: 29 ft 3 in (8.9 m)
- Wingspan: 14 ft 11 in (4.5 m)
- Height: 9 ft 6 in (2.9 m)
- Loaded weight: 11,000 lb (4,990 kg)
- Powerplant: 1× Rocketdyne AR2-3 rocket engine, 6,596 lbf (29.341 kN)
- Power: Gallium Arsenide Solar Cells with lithium-Ion batteries
- Boeing X-40
- Avatar (rocket)
- Orbital Sciences X-34
- “Star Wars 2010? U.S. military launch space plane on maiden voyage… but its mission is top secret”, Daily Mail, 23 April 2010, http://www.dailymail.co.uk/news/worldnews/article-1268138/X-37B-unmanned-space-shuttle-launched-tonight.html .
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- Source of flights: mission markings posted on side of White Knight
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- ‘US’ new spacecraft to trigger arms race in space’
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- X-37B Orbital Test Vehicle. Boeing
- Antczak, John for Associated Press. “Air Force to launch robotic winged space plane”. Physorg.com, April 3, 2010.
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