Orbital Space Plane Program

The Orbital Space Plane (OSP) program was a NASA concept in the early 2000s designed to support the International Space Station requirements for crew rescue, crew transport and contingency cargo such as supplies, food and other needed equipment.

With the initiation of the Constellation program in 2004, NASA transferred the knowledge gained on the OSP to the development of Crew Exploration Vehicle, an Apollo-style capsule with separate crew and service modules.

Origin

The initial plans for the International Space Station envisaged a small, low-cost 'Assured Crew Return Vehicle' (ACRV) which would provide emergency evacuation capability; the X-38 was the prototype of this. Following cancellation of the ACRV in 2002, the program led to the more capable Orbital Space Plane concept.

The first variant of the Orbital Space Plane was designed to serve as a crew rescue vehicle for the ISS; this replaced the previous plans for a dedicated station Crew Return Vehicle, which had been sidelined by budget cuts.

Spaceplane

A spaceplane is an aerospace vehicle that operates as an aircraft in Earth's atmosphere, as well as a spacecraft when it is in space. It combines features of an aircraft and a spacecraft, which can be thought of as an aircraft that can endure and maneuver in the vacuum of space or likewise a spacecraft that can fly like an airplane. Typically, it takes the form of a spacecraft equipped with wings, although lifting bodies have been designed and tested as well. The propulsion to reach space may be purely rocket based or may use the assistance of airbreathing jet engines. The spaceflight is then followed by an unpowered glide return to landing.

Only five spaceplanes have successfully flown to date, having reentered Earth's atmosphere, returned to Earth, and safely landed — the North American X-15, Space Shuttle, Buran, SpaceShipOne, and Boeing X-37. All five are considered rocket gliders. As of 2015, only these aircraft and rockets have succeeded in reaching space. Two of these five (X-15 and SpaceShipOne) are rocket-powered aircraft, having been carried up to an altitude of several tens of thousands of feet by an atmospheric mother ship before being released, and then flying beyond the boundaries of the earth's atmosphere under their own power. Three (Space Shuttle, Buran, and X-37) are vertical takeoff horizontal landing (VTHL) vehicles relying upon rocket lift for the ascent phase in reaching space and atmospheric lift for reentry, descent and landing. The three VTHL spaceplanes flew much further than the aircraft launched ones, not merely leaving the earth's atmosphere but also entering orbit around it, which requires at least 50 times more energy on the way up and heavy heat shielding for the trip back. Also, of the 5 vehicles, three have been piloted by astronauts, with the Buran and X-37 flying unmanned missions.