The Defense Advanced Research Projects Agency (DARPA) Tactical Technology Office (TTO) is requesting information regarding technologies, spaceflight qualification testing, safe handling, and applications for on-orbit satellite nuclear power systems. Our focus is on producible, cost-effective nuclear reactors – not bespoke designs suited for a one-time demonstration. DARPA TTO and the Department of Energy (DOE) will also hold a workshop to establish a common understanding of on-orbit nuclear power technology and challenges, facilitate community interactions and collaboration, and identify key technology risk areas that, if addressed, would enable practical implementation of on-orbit nuclear power. The workshop will be held on April 21-22, 2026 at the DARPA Conference Center (DCC), 675 N Randolph Street, Arlington, VA 22203.