[en] The first step in effectively understanding and using space reactor electric systems is to understand thoroughly the building blocks that make up the systems -- the subsystems. This paper is a synopsis of a technology assessment of these subsystems. The assessment, performed by Rockwell International, determined where subsystem technology had been in the past, where it can go in the future, how long it will take to get there, and how much it will cost to develop. The subsystem assessment is part of an overall system-level assessment that is now under way