Fuel cells have been used as a power source in the space shuttle for decades and are expected to be used in future higher power, larger systems. A new, passive gas/liquid phase separator for use in such large fuel cell space applications has been invented. It is a vortex separator designed to accommodate gas driven two phase flows. The work presented here is a first of a kind study of this newly invented separator examining the minimum inlet gas flow rate necessary for a stable vortex inside the separator as a function of separator size. A dimensional scaling analysis was done to predict this minimum inlet gas flow rate. Experiments were performed on the ground and in conjunction with the NASA microgravity simulating aircraft to validate modeling. The results of the experiments and scaling analysis are compared.