Martin X-23 PRIME

The Martin X-23A PRIME, built by Martin Marietta for the United States Air Force, was a small unmanned lifting-body re-entry vehicle flown in 1966 and 1967 as part of the Air Force's START programme. PRIME stands for Precision Reentry Including Maneuvering reEntry, and the vehicle, also designated SV-5D, was meant to show that a wingless shape could steer itself during re-entry, where the earlier ASSET gliders had mainly tested structures and heating. Each vehicle rode an Atlas booster from Vandenberg Air Force Base, separated at re-entry speed and was guided to a chosen recovery area, protected by an ablative heat shield and slowed by a ballute and parachute so that a modified C-130 could catch it in mid-air. Three flights were made between December 1966 and April 1967, and the last recovered the craft after a manoeuvre reaching about 1,143 kilometres of cross-range. The shape led on to the piloted X-24, and a surviving X-23A is displayed at the National Museum of the United States Air Force.