Development of an innovative microwave-based continuous flow sterilization system for the energy efficient gravitationally independent production of Medical Grade Water (MGW) is proposed. During the Phase I, microwaves were very efficiently coupled to a single-phase flowing water stream using an antenna based microwave sterilization chamber that rapidly heated water to temperatures well above normal autoclave conditions. Microbial sterilization was demonstrated for single and mixed cultures of gram-positive and gram-negative bacteria including Bacillus stearothermophilus, a thermophilic spore former utilized to validate autoclave sterilization. Novel ultrahigh temperature sterilization processes eliminated chemical sterilization requirements for external connections, and more significantly, inactivated endotoxins, a major MGW purity requirement. These attributes results in an extremely low ESM, MGW generator that will meet autonomous medical care needs for MGW aboard manned spacecraft, or Lunar and planetary habitations. A fully functional computer controlled prototype capable of producing MGW from NASA potable water without expendables will be developed during the Phase II. To achieve these objectives, a compact controllable microwave power generator will be mated to an optimized sterilization chamber producing an energy efficient MGW generator without the need for expendables. Characterization of system performance and ESM will provide the basis for future NASA development decisions.