Future missions will need power systems for small spacecraft.
As missions look beyond the inner solar systems, solar flux drops off immensely, requiring solar-powered missions to have enormous solar arrays. As small spacecraft are fundamentally volume limited, solar arrays for U-Class and small spacecraft provide insufficient power for deep-space (beyond Jupiter) missions. NASA needs new power systems in order for small spacecraft to expand their use for proposed deep space missions.
Proposed deep space missions could significantly benefit from a set of U-Class spacecraft providing myriad functions, such as taking measurements, serving as small impactors or low fidelity probes, and performing health checks on the parent spacecraft. However, at the distance of Jupiter, for example, solar irradiance is just 3% of what it is at Earth orbit. Thus, at deep space distances, the available power provided by U-Class solar arrays is inadequate.
Chris Baker, Small Spacecraft Technology Program Executive