Deployment of defensive weapons in the space environment calls for advanced propulsion systems with high ISP and the capability for long term deployment, on station at various orbit levels. High ISP means exploitation of the. Performance potential or liquid hydrogen fuels. Long-term deployment requires high propellant specifics, low vehicle weights and utilization of the total energy potential of "on board" propellants. One way to minimize these parameters is the use of a common propellant supply for orbit transfer and spacecraft, attitude control engines. To make hydrogen usable in such a system, it is desirable to use high pressure gases in the attitude control engines. This can be accomplished by the development of an electrically driven, gaseous propellant compressor to compress boiloff gases from the main propellant tanks. To be successful, technology must be developed for the design of a pump capable of up to 100 to 1 pressure ratios at near cryogenic inlet temperatures. The pump must be leak proof and capable of operation for at least 10,000 hours without overhaul. Material for seals, valves and bearing must be found or developed. Finally, the technology needs to be demonstrated by operation of a prototype pump in a follow-on development phase.
