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X-37B OTV 1, 2, 3

X-37 (on orbit) [Boeing]

X-37 [Boeing]

X-37 OTV-1 [USAF]

The X-37B is a prototype of a reusable unmanned satellite. The first prototype is for atmospheric testing, while the second has a strengthened structure to support an unshrouded launch, which was originally planned to be launched in the Shuttle payload bay, the transferred after the Columbia accident to a Delta-7920 launch vehicle. Due to problems with the aerodynamics of an unshrouded launch, the first space test was be launched shrouded on a Atlas-5(501) or on a Delta-4M+(5,2) in 2006. Multiple flights with mission durations up to 21 days are planned. NASA asked Boeing to design the X-37 orbital vehicle for a 270-day stay on orbit.

The original X-37 was to feature an AR-2/3 engine for maneuvering and deorbiting, which uses Hydrogen Peroxide and JP-8 as oxidizer and fuel. Later the propulsion system has been changed to a hypergolic nitrogen tetroxide / hydrazine version with a robust propellant load for maneuvering in space and for the deorbit burn.

The X-37's shape is a 120 percent scale derivative of the Air Force's X-40A, also designed and built by Boeing, which was released from a helicopter and glide-tested in 1998. The X-40A, which lacks the X-37's advanced thermal protection materials, rocket engine, experiment bay and other spacecraft systems, was released from a U.S. Army Chinook helicopter in a series of free flight tests in 2001 to reduce technical risk before flight testing the X-37.

NASA has directed Boeing to throttle back on development of the orbital variant of the X-37 prototype space plane until more money is found for the program, an action likely to delay a re-entry and landing demonstration that was planned for 2006.

Following transfer from NASA to DARPA in October 2004, the X-37 technology demonstrator, the Approach and Landing Test Vehicle, recently completed a series of captive carry and free flight tests from the White Knight aircraft, which was also used to launch the SpaceShipOne. The ALTV validated the X-37 program flight dynamics and extended the flight envelope beyond the earlier low speed/low altitude tests conducted by NASA. The ALTV, in its current configuration, is not capable of space flight.

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 first orbital test flight of the OTV was planned for FY08, with a launch from Cape Canaveral Air Force Station on an Atlas-5(501) launch vehicle. Key objectives of the first flight include demonstration and validation of guidance, navigation and control systems to include fault tolerant, autonomous reentry and landing as well as lightweight high temperature structures and landing gear. Vandenberg Air Force Base will conduct reentry and recovery activities. The first launch did finally take place in 2010.

The first vehicle, X-37B OTV-1 was launched on April 22, 2010 from Cape Canaveral. Although orbital data was classified, the OTV-1 was found in an 401 km × 422 km, 40 orbit by amateur observations. The Centaur upper stage was reportedly disposed off in an escape trajectory to solar orbit. The X-37B OTV-1 conducted several orbit changes during its mission. It landed successfully on December 3, 2010 after 225 days in space. The vehicle will be refurbished for a second flight.

The first flight of the second vehicle, X-37B OTV-2, began in March 2011. This time it stayed 469 days in space, more than doubling the endurance of the first mission.

A second flight of the first vehicle, X-37B OTV-3, was launched in December 2012.

Nation: USA
Type / Application: Reusable satellite
Operator: NASA, USAF
Contractors: Boeing
Equipment: ?
Configuration: reusable space plane
Propulsion: R-4D ?
Power: Deployable solar array, batteries
Lifetime: 270 days (nominal); 225 days (#1); 469 days (#2)
Mass: 5400 kg
Orbit: 401 km × 422 km, 40 (#1), 315 km × 341 km, 43 (#2), 343 km × 360 km, 43.5 (#3)
Satellite COSPAR Date LS Launch Vehicle Remarks
X-37B OTV-1 (USA 212) 2010-015A 22.04.2010 CC SLC-41 Atlas-5(501)
X-37B OTV-2 (USA 226) 2011-010A 05.03.2011 CC SLC-41 Atlas-5(501)
X-37B OTV-3 (USA 240) 2012-071A 11.12.2012 CC SLC-41 Atlas-5(501)