Between 1998 and 2003, Hi-Z Technology developed and built a 40 mW radioisotope power supply (RPS) that used a 1 watt radioisotope heater unit (RHU) as the energy source. This RPS represented a continuation of 30 years of development that began in the Thermoelectrics Division of General Atomics in the 1960's. This system is the most efficient of its size to this day, and has been validated by extensive life testing. We now propose to devise improvements to the design giving it increased resistance to mechanical shock. In the Phase I we will conduct simulations to inform a trade study examining multiple options of up to 10,000 G of shock tolerance and up to 40 mW of output power. We will also build TEM modules for destructive testing to measure mechanical properties. In Phase II, we will fabricate prototypes that use electric heaters and weights to simulate an RHU. These will be subjected to shock testing at NASA Ames. After iterations of design, build and test, we will present a new RPS design that offers valuable new mission capabilities to the space program.