9-6. Preliminary Assessment of Rover Power Systems for the Mars Rover Sample Return Mission D. J. BENTS Summary Four isotope power system concepts are presented and compared on a common basis for application to on-board electrical prime power for an autonomous planetary rover vehicle. A representative design point corresponding to the Mars Rover Sample Return (MRSR) preliminary mission requirements (500 watts) was selected for comparison purposes. All system concepts utilize the GPHS isotope heat source developed by DoE. Two of the concepts employ thermoelectric (TE) conversion: one using the GPHS RTG used as a reference case, the other using an advanced RTG with improved thermoelectric materials. The other two concepts employed are dynamic isotope power systems (DIPS): one using a closed Brayton cycle (CBC) turboalternator, and the other using a free piston Stirling cycle engine /linear alternator (FPSE) with integrated heat source/heater head. Near-term technology levels have been assumed for concept characterization using component technology figure-of-merit values taken from the published literature. For example, the CBC characterization draws from the historical test database accumulated from space Brayton cycle subsystems and components from the NASA ‘B' engine through the mini-BRU. TE system performance is estimated from Voyager/MHW- RTG flight experience through Mod-RTG performance estimates considering recent advances in TE materials under the DoD/DoE/NASA SP-100 and NASA CSTI programs. The Stirling DIPS system is characterized from scaled-down Space Power Demonstrator Engine (SPDE) data using the GPHS directly incorporated into the heater head. The characterization/comparison results presented here differ from previous comparisons of isotope power (made for LEO applications) because of the elevated background temperature on the Martian surface compared to LEO, and the higher sensitivity of dynamic systems to elevated sink temperature. Although dynamic systems have historically shown advantages of lower specific mass and reduced isotope inventory per delivered electrical watt, the mass advantage of dynamic systems is significantly reduced for this application due to Mars' elevated background temperature. Introduction The Mars Rover Sample Return (MRSR) Mission proposed for the late 1990s (discussed in Refs [1] and [2]), would place two spacecraft in orbit about Mars and land a surface rover vehicle (Fig. 1). In addition, a separate ascent stage would return about 100 kg of geological samples gathered by the rover to Earth. Building on the legacy from the Viking program, where delivery of payloads to the Martian surface D. J. Bents, NASA-Lewis Research Center, Cleveland, OH 44135, USA. Paper number IAF-ICOSP89-9-6.
RkJQdWJsaXNoZXIy MTU5NjU0Mg==