X-23 with X-24
X-23 with Orbital X-24
Credit: Lockheed Martin
American manned combat spacecraft. Cancelled 1961. At the beginning of the 1960's, the USAF examined a number of approaches to a manned spacecraft designed to rendezvous with, inspect, and then, if necessary, destroy enemy satellites.
The preferred design was a lifting body, a development line that led eventually to the X-24C spaceplane. The project was quickly squelched by USAF X-20 Dyna-Soar advocates (or possibly it went deep black). Alternatives publicly mentioned as replacements for the mission were the Dynasoar with special payload provisions, or Gemini variants with combat provisions.
On 19 May 1961 the USAF Space Systems Division (SSD) announced its SAINT-II manned space interceptor concept. This was to be a two-man lifting body spacecraft, using subsystems developed for the SAINT-I unmanned satellite inspector. SAINT-II would be capable of orbital rendezvous and limited space logistics missions. Launch vehicle would be a Titan II equipped with a Chariot LF2/Hydrazine high-performance third stage. Following an unmanned test flight in early 1964, 12 manned orbital missions would be conducted, including both near- and far-earth flights. DynaSoar I was seen as not being capable of the mission, due to its limited payload, and restriction to low earth orbits. SSD estimated the total cost for SAINT-II to be $413.8 million, to be spent in the period FY1962 - FY1965.
Naturally this program was seen by USAF DynaSoar advocates as a threat to their project. In October 1961 a USAF management group criticized the proposed SAINT II program as unrealistic in schedule and budget. Not only was it eventually cancelled, but also the USAF later prohibited further use of the SAINT designation in proposals.