Phase separation in reduced gravity continues to be an obstacle for the National Aeronautics and Space Administrations' power programs. Phase separation would be necessary for the use of a Rankine power conversion cycle in microgravity. The vortex phase separator invented by Texas A&M University may be implemented in a microgravity Rankine cycle for successful phase separation. With the known characteristics of the separator/inventory control system, the Texas A&M University vortex phase separator can be operated successfully for a wide variety of uses in microgravity. The separator operating principle and envelope, test performance data, and inventory monitoring system are described.