The X-37B is an American experimental military spacecraft operated by the United States Air Force (USAF) and National Aeronautics and Space Administration (NASA). The aircraft is designed for reusable space missions of up to 270 days, with a maximum payload of 8,000 pounds (3,600 kg). The X-37B is a robotic vehicle which launches vertically and lands horizontally. It is currently used for various purposes including testing new technologies in orbit, conducting risk reduction experiments, and demonstrating reusable spacecraft technologies.
The first X-37B mission was launched on April 22, 2010 from Cape Canaveral Air Force Station in Florida, USA. The second mission was launched on March 5, 2011 from Vandenberg Air Force Base in California, USA. As of July 2014, the two craft have completed a combined 468 days in orbit.
The X-37B program is managed by the USAF Rapid Capabilities Office. Boeing Defense, Space & Security’s Phantom Works division serves as the prime contractor for the vehicle; other contributors include United Launch Alliance (ULA), Orbital Sciences Corporation (now Northrop Grumman Innovation Systems), Honeywell International Inc., and Ball Aerospace & Technologies Corp.. NASA’s involvement includes managing the transfer of new technologies developed for the X-37B to its own future programs such as Orion or Commercial Crew Development effort.
The original plan for the Pentagon’s Experimental Spaceplane System called for two vehicles: one each from Boeing and Lockheed Martin. However, budget cuts forced cancellation of Lockheed’s design in 2001; only Boeing continued with development of their concept vehicle now designated as “XSPS” (“eXperimental Space Plane”). On September 16, 2004 NASA announced that they would be joining forces with DARPA and USAF on this project which was then renamed “XSS” (“eXperimental Space System”). In 2005 it was again renamed to “XCV” (“eXperimental Conventional Vehicle”), though some documents still referred to it as “XSS”. On December 13 that year it received its final designation as “X 37”, or “Experimental Transport Aircraft”. Following additional delays due to issues with propulsion system safety certification by Aerojet Rocketdyne – manufacturer of AJ26 engines originally selected – Pratt & Whitney Rocketdyne RL10 engines were substituted instead . This change added significant delay because PWR had no prior experience certifying an engine for use on an orbital launch vehicle . After review by government auditors it was decided in early 2006 that developing two separate but similar transport aircraft systems side-by-side was not prudent use of resources so only Boeing’s entry would continue being developed into what became known as just “the X 37″ or occasionally also called simply OTV (“Orbital Test Vehicle”).