Hybrid electrical power source testing for electromechanical actuation applications

New technology Launch vehicle programs such as the Reusable Launch Vehicle (RLV)X-33 and the Evolutionary Expendable Launch Vehicle (EELV), have the desire to incorporate electromechanical actuator (EMA) technology for thrust vector control (TVC), aerosurface control and propellant flow valves. A major part of this technology advancement lies in power source selection, development and testing. The challenge for EMA power sources is the high pulse, high rate power demands needed for electromechanical actuation. By using a turbo-alternator/capacitor hybrid power source, significant load leveling and improved overall performance result. Previous testing at NASA's Marshall Space Flight Center (MSFC) with the support of Auburn University's Space Power Institute proved the validity of the hybrid power source concept. MSFC in cooperation with Lockheed Martin Astronautics tested several power sources using a 25 hp EMA developed at MSFC as the load. A bank of deep-cycle marine lead-acid batteries, silver-zinc (Ag-Zn) batteries, and hybrid combinations of each were compared for their performance characteristics. Test results reveal the performance traits of each source under various EMA load profiles, and the optimization gained by using a hybrid configuration.