SNAP-8 Electrical System

This paper presents a brief description of the SNAP-8 electrical-system design changes and provides a broad perspective of the overall system changes incorporated early in 1963. These modifications made feasible a modular approach to component and subsystem development, provided greater system development flexibility, and permitted the application of much presently available electrical technology. The rotating speed was changed from 20,000 to 12,000 revolutions per minute (rpm) resulting in a change of system frequency from 1,000 to 400 cycles per second (cps). The alternator and the regulator were removed from the high-temperature and mercury-vapor environment. The mercury lubrication and cooling concept was replaced with organic-fluid lubrication and a low-temperature cooling loop was added to the system. Significant development problems still exist, however. There remains the requirement for 10,000-hours minimum life in the space and nuclear environment, coupled with extremely high reliability objectives.