Summary
The objective of NASP was to develop two flight vehicles with air breathing propulsion from takeoff to orbit. Rocket engines were to be used for final orbital insertion and orbital maneuvers. Airframe, engine module and test facility RFPs were sent out in November 1985. In April 1986 the first design contracts for the NASP program were awarded. Contractors included Boeing, Lockheed, McDonnell Douglas, General Dynamics and Rockwell, with Pratt & Whitney and General Electric for propulsion research. Rocketdyne later contributed to NASP under its own funding. In October 1987, following Phase 2A evaluation, Lockheed and Boeing were dropped from the NASP program, alongside General Electric. Throughout the NASP program the Department of Defense had an 80% share of all money spent on the program. In 1989, during his first week of office as the Secretary of Defense, Richard Cheney terminated the DoD NASP effort. A program review by the National Space Council recommended extending Phase 2 to 1993. In 1991, the National Team program approach combined the resources of the five contractors in a joint-venture partnership to develop a single X-30 concept. Upon completion of the Phase 2D technology development portion in 1993, the technological maturity was deemed not to be at the level required to justify a $15 billion investment to develop two X-30 aircraft in Phase 3, and the NASP was finally cancelled in May 1993.
Sources
http://www.secretprojects.co.uk/forum/index.php/topic,315.0/all.html