Abstract:
Radioisotope Power Systems (RPS’s) are a key element to NASA’s deep space
exploration programs. As NASA looks towards new generations of smaller, modular
spacecraft, appropriately smaller RPS’s will be needed. The Single General Purpose Heat
Source Radioisotope Thermoelectric Generator (S-GPHS-RTG) has been developed to
fill this role. The S-GPHS-RTG will utilize one GPHS to provide 250 Wt which will be
ideally be converted to 20-25 We by Thermoelectric Converters (TEC’s). Using a full
scale model S-GPHS-RTG in a vacuum chamber, 250 Wt was applied via an electrically
powered model GPHS, and steady-state temperatures were observed. As part of these
tests, multiple insulation packages were investigated, including: Multi Layer Insulation
(MLI), silica fiber, and various aerogel combinations. The vacuum conditions were
intended to simulate space conditions the S-GPHS-RTG will experience as it travels
through space. The steady-state temperatures it experiences will largely affect its
performance as a power source, as the TEC’s ability to convert heat to electricity is
dependent on the temperature gradient they experience. A virtual model of the
experiment was also created in Thermal Desktop in an attempt to simulate it. However,
this virtual model failed to generate accurate results.
