The desire to utilize low cost, quick turn around CubeSats for interplanetary missions is an exciting challenge. There are three fundamental constraints to the system design that a long duration, interplanetary mission imposes: Power Generation, Volume, and Radiation. This talk will discuss the critical design decision between going RadHard vs COTS, and provide a comparison of their relative performance, and power requirements. A brief discussion on radiation effects on components will lead into a trade of several system architectures. It will be shown that the pace that modern mobile electronics are progressing, and performance per watt that they achieve makes a strong case for their utilization. Modern processors and memory provide the processing capability and storage, with a variety of “Sleep” modes for significant power savings. Several radiation tolerant system design techniques are discussed to enable COTS technology to survive long duration, interplanetary missions. The talk will end by proposing a mission that could provide enormously useful data points that can influence the design of technically ambitious CubeSat missions with high science value.