A dynamic liquid/gas separator for microgravity applications has been developed. A dynamic separator was designed and fabricated to further develop the technology needed to efficiently separate liquids and gases in a microgravity space environment. Similar units had been utilized in space before, and a number of problems had been identified. Some of these were liquid carryover (poor separation), flooding of the unit, foaming of the liquid in the separator, and high levels of gas trapped in the separated liquid.This design built upon the technology utilized to date and extended that technology to address previous problems of inefficient separation of liquids and gases in space. A prototype laboratory unit was successfully built and then extensively tested both in the laboratory and in a microgravity environment aboard the KC-135. The test data demonstrated that the design concepts employed advanced the state of the art for separating liquids and gases in a microgravity space environment.The integrated fan/separator unit contains a rotating liquid/gas separator bowl, a pitot pump, two centrifugal impellers, a liquid check valve, and a three-phase, 400-Hz electric drive motor. Phase separation is accomplished by centrifugally separating liquid which is entrained in a gas. Gas flow developed by the blower draws the liquid/gas stream into the separator. The liquid is centrifuged to the periphery of the separator and collected by the pitot pump. The relative velocity between the stationary pitot tube and the rotating fluid creates a pumping effect, which discharges the liquid through a check valve. After separation, the gas passes through the centrifugal blower and is available for use. This design concept incorporates liquid/gas separation, liquid removal, and gas flow/pressurization into one unit, thus minimizing power, weight, and volume penalties to the system.This paper describes the design, development, and performance of the liquid/gas separator. This paper also discusses testing of the separator unit, including descriptions and results from ground and KC-135 testing.