Electrical Power Control and Conditioning Subsystem for the Manned Orbital Research Laboratory (MORL)

The electrical power control and conditioning subsystem developed under NASA* Contract NASl-4479 represents an integrated, operational design for the Manned Orbital Research Laboratory (MORL) to support 6 men in space for 5 years. The power conditioning systems discussed in recent engineering papers have generally been planned for unmanned craft or were for optimizations of specific electrical loads of modest demand levels, and used conventional battery, solar cell/battery, or fuel cell energy sources. Therefore, an advanced design to supply a greater (by an order-of-magnitude) electrical demand from a radioisotope-dynamic generator drive system, and which meets manned spacecraft design criteria, represents a significant and unique contribution to aerospace electrical design. This paper identifies and discusses (1) the unique electrical design criteria and constraints associated with the radioisotope Brayton cycle drive system, (2) the tradeoff considerations which were necessary to optimize the total system with respect to speed, frequency, and efficiency, (3) the rationale for the selection of the alternator and the frequency converters, and (4) the distribution system design criteria which were established to assure flexibility, efficiency, maintainability, and safe emergency operations. The control system concept and its integration with the energy storage subsystems will also be discussed.