The development of a milliwatt-level radioisotope power source

Future NASA spacecraft for unmanned planetary exploration will be much smaller and require much less power than the large systems used in prior missions. The “Powerstick”, a miniaturized isotopic electrical power generator, uses a flight-qualified, DoE-manufactured, 1.1 W Radioisotope Heater Unit (RHU) to generate the high temperature sink for a thermoelectric converter (TEC). The TEC generates sufficient electrical power (∼40 mW) to trickle-charge an external rechargeable battery pack, which can then be used in low duty cycle, low power applications. The original Powerstick concept (proposed by JPL) was refined at Swales Aerospace (SA), which has: repackaged it, constructed a prototype, and performed limited testing. The prototype Powerstick is 63.5 mm (2.500″) in diameter, 76.2 mm (3.000″) long, and weighs about 0.3 kg (0.66 lb). Structural analysis indicates the Powerstick can easily survive typical launch loads. Thermal analysis indicates that over 70% of the RHU energy enters the TEC. This paper will...