Engineering topics

Withrow, C. A.

Publications and source records attributed to Withrow, C. A..

5 records

NASA NTRS1992

Design of small Stirling dynamic isotope power system for robotic space missions

Design of a multihundred-watt Dynamic Isotope Power System (DIPS) based on the U.S. Department of Energy (DOE) General Purpose Heat Source (GPHS) and small (multihundred-watt) free-piston Stirling engine (FPSE) technology is being pursued as a potential lower cost alternative to radioisotope thermoelectric generators (RTG's). The design is targeted at the power needs of future unmanned deep space and planetary surface exploration missions ranging from scientific probes to Space Exploration Initiative precursor missions. Power level for these missions is less than a kilowatt. Unlike previous DIPS designs which were based on turbomachinery conversion (e.g. Brayton), this small Stirling DIPS can be advantageously scaled down to multihundred-watt unit size while preserving size and mass competitiveness with RTG's. Preliminary characterization of units in the output power ranges 200-600 We indicate that on an electrical watt basis the GPHS/small Stirling DIPS will be roughly equivalent to an advanced RTG in size and mass but require less than a third of the isotope inventory.

Bents, D. J.↗

NASA NTRS1991

SEI power source alternatives for rovers and other multi-kWe distributed surface applications

Results of the study performed to support the Space Exploration Initiative (SEI) which investigated power system alternatives for the rover vehicles and servicers that would be used for construction and operation of a lunar base is described. Using the mission requirements and power profiles that were subsequently generated for each of these rovers and servicers, candidate power sources incorporating various power generation and energy storage technologies were identified. The technologies were those believed most appropriate to the SEI missions, and included solar, electrochemical, and isotope systems. The candidates were characterized with respect to system mass, deployed area and volume. For each of the missions a preliminary selection was made. Results of this study depict the available power sources in light of the mission requirements as they are currently defined.

Bents, D. J.↗

NASA NTRS1991

Design of multihundredwatt DIPS for robotic space missions

Design of a dynamic isotope power system (DIPS) general purpose heat source (GPHS) and small free piston Stirling engine (FPSE) is being pursued as a potential lower cost alternative to radioisotope thermoelectric generators (RTG's). The design is targeted at the power needs of future unmanned deep space and planetary surface exploration missions ranging from scientific probes to SEI precursor missions. These are multihundredwatt missions. The incentive for any dynamic system is that it can save fuel which reduces cost and radiological hazard. However, unlike a conventional DIPS based on turbomachinery converions, the small Stirling DIPS can be advantageously scaled to multihundred watt unit size while preserving size and weight competitiveness with RTG's. Stirling conversion extends the range where dynamic systems are competitive to hundreds of watts (a power range not previously considered for dynamic systems). The challenge of course is to demonstrate reliability similar to RTG experience. Since the competative potential of FPSE as an isotope converter was first identified, work has focused on the feasibility of directly integrating GPHS with the Stirling heater head. Extensive thermal modeling of various radiatively coupled heat source/heater head geometries were performed using data furnished by the developers of FPSE and GPHS. The analysis indicates that, for the 1050 K heater head configurations considered, GPHS fuel clad temperatures remain within safe operating limits under all conditions including shutdown of one engine. Based on these results, preliminary characterizations of multihundred watt units were established.

Bents, D. J.↗

NASA NTRS1991

SEI power source alternatives for rovers and other multi-kWe distributed surface applications

To support the Space Exploration Initiative (SEI), a study was performed to investigate power system alternatives for the rover vehicles and servicers that were subsequently generated for each of these rovers and servicers, candidate power sources incorporating various power generation and energy storage technologies were identified. The technologies were those believed most appropriate to the SEI missions, and included solar, electrochemical, and isotope systems. The candidates were characterized with respect to system mass, deployed area, and volume. For each of the missions a preliminary selection was made. Results of this study depict the available power sources in light of mission requirements as they are currently defined.

Bents, David J.↗

NASA NTRS1991

Design of multihundred-watt dynamic isotope power system for robotic space missions

The design of a multihundred-watt dynamic isotope power system (DIPS) based on the US Department of Energy (DOE) general-purpose heat source (GPHS) and small (multihundred-watt) free-piston Stirling engine (FPSE) is described as a potential lower cost alternative to radioisotope thermoelectric generators (RTGs). The design is targeted at the power needs of future unmanned deep space and planetary surface exploration missions. Since the competitive potential of FPSE as an isotope convertor was first identified, work has focused on the feasibility of directly integrating GPHS with the Stirling heater head. Thermal modeling of various radiatively coupled heat source/heater head geometries has been performed using data furnished by the developers of FPSE and GPHS. The analysis indicates that, for the 1050 K heater head configurations considered, GPHS fuel clad temperatures remain safe operating limits under all conditions including shutdown of one engine on a twin engine unit. Based on these results, preliminary characterizations of multihundred-watt units have been established. They indicate that, per electrical watt, the GPHS/small Stirling DIPS will be roughly equivalent to MOD RTG in size and mass but will require about a third the amount of isotope fuel.

Bents, D. J.↗