Design and spacecraft-integration of RTGs for solar probe

The design, analysis, and spacecraft integration of radioisotope thermoelectric generators (RTG) to power the Solar Probe under study at NASA JPL is described. The mission of the Solar Probe is to explore the solar corona by performing in situ measurements at up to four solar radii to the sun. Design constraints for the RTG are discussed. The chief challenge in the design and system integration of the Solar Probe's RTG is a heat rejection problem. Two RTG orientations, horizontal and oblique, are analyzed for effectiveness and results are summarized in chart form. A number of cooling strategies are also investigated, including heat-pipe and reflector-cooled options. A methodology and general computer code are presented for analyzing the performance of arbitrarily obstructed RTGs with both axial and circumferential temperature, voltage, and current variation. This methodology is applied to the specific example of the Solar Probe RTG obstructed by a semicylindrical reflector of 15-inch radius.