An on-board oxygen concentrator is required during long duration manned space missions to supply medical oxygen. Commercial medical oxygen generators are pressure swing adsorption (PSA) based systems that use nitrogen selective zeolites and are mostly large, massive, and power intensive. TDA Research, Inc. (TDA) proposes to develop a small, lightweight, portable oxygen generator that uses a high capacity, long life, regenerable oxygen absorbent to produce concentrated medical oxygen from ambient cabin air. TDA's system will have less volume, mass, and power draw than current systems. In Phase I, we will demonstrate the ability of the oxygen concentrator technology to produce greater than 60% oxygen at 6 LPM from ambient cabin air. We will evaluate the sorbent performance in bench-scale experiments and carry out a preliminary design of the unit, determine its weight, volume and energy requirements, and compare them to those of other competing technologies. The technology will be at TRL-3 at end of Phase I. In Phase II, we will fabricate a sub-scale oxygen concentrator prototype with all key components to fully demonstrate the concept and reliable long duration operation. We will optimize cycle duration, stage length etc. The technology will be at TRL-5 at end of Phase II.