The authors apply the philosophy of better, faster, cheaper to the selection of a radioisotope
power system. Presented are definitions of ‘Better’ and ‘Faster’ capable of evaluation. A cost model, based on Cassini program data, aids in defining ‘Cheaper’. The study assesses a number of power conversion designs. A systematic approach evaluates these power conversion alternatives. A modified and repacked Cassini—type RTG results as the best choice for mission success.