This page no longer updated from 31 October 2001. Latest version can be found at Prime

Prime -

Credit: USAF. 30,365 bytes. 241 x 427 pixels.

Other Designations: SV-5D. Article Number: X-23A. Class: Manned. Type: Spaceplane. Nation: USA. Manufacturer: Martin.

After the cancellation of Dynasoar, the Air Force pursued futher development of manned spaceplanes under the START Project. This included the ASSET and PRIME/X-23 suborbital launch of subscale lifting body designs and B-52 drop tests of the X-24A and X-24B lifting body designs into the mid-1970's. The X-23 was a subscale re-entry test vehicle of the lifting body configuration used in the X-24A manned aerodynamic test aircraft. The PRIME (Precision Recovery Including Maneuvering Entry) project was the second part of the START program. It had the dual objective of testing advances in space hardware and further exploring the development of manned and unmanned lifting body vehicles. Four SV-5D vehicles were built by the Martin Company to fulfill the objectives of the PRIME program. Outside earth's atmosphere the SV-5D was maneuvered by the release of high pressure nitrogen through jet thrusters. When the craft re-entered the atmosphere its control system automatically switched to airplane-type flaps for pitch and roll control.

On a typical flight, the unmanned SV-5D was launched by an Atlas booster from Vandenberg AFB, California. At the high point in its flight path, the Atlas pitched downward while its rocket continued accelerating it to speeds nearly as great as those of the spacecraft re-entering the earth's atmosphere. The lifting body's inertial guidance system directed it to a preselected recovery point. Three PRIME test flights were made, the first on December 21, 1966, and the last on April 19, 1967. A scheduled fourth flight was cancelled due to successes of the previous tests.


Total Length: 2.1 m. Maximum Diameter: 1.2 m. Total Mass: 405 kg. Electrical System: Batteries.

Prime Chronology

21 December 1966 Prime 1 Launch Site: Vandenberg . Launch Vehicle: SLV-3 Atlas.


05 March 1967 Prime 2 Launch Site: Vandenberg . Launch Vehicle: SLV-3 Atlas.


19 April 1967 Prime 3 Launch Site: Vandenberg . Launch Vehicle: SLV-3 Atlas.



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Last update 12 March 2001.
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© Mark Wade, 2001 .