A new space power concept incorporating Earth-to-satellite microwave power transmission coupled to onboard regenerative electrochemical energy storage is proposed for energizing defensive satellite constellations. The system addresses housekeeping, orbital maneuvering, and burst-mode power requirements, and offers an attractive alternative to the nuclear space power systems currently being considered for this application. This energy-conversion system incorporates six steps: 1) generate primary dc power at surface stations along the satellite ground track, 2) convert to microwave (rf) frequencies, 3) transmit in a narrow beam to spacecraft using phased-array antennas that track and lock on to satellite receivers as they pass in range during a fraction of their orbit, 4) receive the energy and convert to dc in space using lightweight and inexpensive rectennas, 5) store the energy onboard as chemical energy by electrolysis of water to oxygen and hydrogen, and 6) recover free energy onboard the spacecraft during the balance of the orbit continuously or on demand as pulsed power with a high power-density fuel cell. Component and overall systems considerations of this scheme are discussed, outstanding research problems are defined, and preliminary analyses are described.