The X-37B Orbital Test Vehicle, or OTV, is an experimental test program to demonstrate technologies for a reliable, reusable, unmanned space test platform for the U.S. Air Force. The primary objectives of the X-37B are twofold; reusable spacecraft technologies for America’s future in space and operating experiments which can be returned to, and examined, on Earth.
The X-37B Orbital Test Vehicle is the newest and most advanced re-entry spacecraft. Based on NASA’s X-37 design, the unmanned OTV is designed for vertical launch to low Earth orbit altitudes where it can perform long duration space technology experimentation and testing. Upon command from the ground, the OTV autonomously re-enters the atmosphere, descends, and lands horizontally on a runway. The X-37B is the first vehicle since NASA’s Shuttle Orbiter with the ability to return experiments to Earth for further inspection and analysis, but with an on-orbit time of 270 days or greater, the X-37B can stay in space for much longer.
Technologies being tested in the program include advanced guidance, navigation and control, thermal protection systems, avionics, high temperature structures and seals, conformal reusable insulation, lightweight electromechanical flight systems, advanced propulsion systems, advanced materials and autonomous orbital flight, reentry and landing.
The Air Force Rapid Capabilities Office is leading the Department of Defense’s Orbital Test Vehicle initiative, by direction of the Under Secretary of Defense for Acquisition, Technology and Logistics and the Secretary of the Air Force. The Air Force OTV effort uses extensive contractor and government investments in the X-37 program by the Air Force, NASA and the Defense Advanced Research Projects Agency to continue full-scale development and on-orbit testing of a long-duration, reusable space vehicle.
NASA’s original X-37 program began in 1999 and was transferred to DARPA in 2004. NASA envisioned building two vehicles, an Approach and Landing Test Vehicle, or ALTV, and an Orbital Vehicle. DARPA completed the ALTV portion of the X-37 program in 2006, executing a series of captive carry and free flight tests. DARPA successfully validated the flight dynamics and extended the flight envelope beyond the low speed/low altitude tests previously conducted by NASA on the X-40A, a sub-scale version of the X-37 developed by Air Force Research Labs. NASA’s X-37 Orbital Vehicle was never built, but its design was the starting point for the Air Force’s X-37B Orbital Test Vehicle program.
The Air Force has successfully flown four X-37B missions, OTV-1 through OTV-4, beginning with its first launch on April 22, 2010 from Cape Canaveral Air Force Station, Fla. OTV-1 through OTV-3 all landed successfully at Vandenberg AFB, Calif., and the most recent mission, OTV-4, successfully landed at Kennedy Space Center, Fla. The first four OTV missions have spent a total of 2,085 days on orbit, successfully checking out the X-37B’s reusable flight, reentry and landing technologies as well as operating experiments to benefit the national space community. The fifth mission, OTV-5, was launched from Cape Canaveral Air Force Station, Fla. on 7 September, 2018, and is currently on orbit.
Primary Mission: Experimental test vehicle
Prime Contractor: Boeing
Height: 9 feet, 6 inches (2.9 meters)
Length: 29 feet, 3 inches (8.9 meters)
Wingspan: 14 feet, 11 inches (4.5 meters)
Launch Weight: 11,000 pounds (4,990 kilograms)
Power: Gallium Arsenide Solar Cells with lithium-Ion batteries
Launch Vehicles: United Launch Alliance Atlas V (501) and SpaceX Falcon 9