Characterization of a Phase Change Propellant Management Device

CubeSat propulsion imposes unique propellant management issues. The requisite form factor often necessitates conformal tank geometries and high-density two-phase propellants. Fluid management in these saturated propellant systems cannot generally be accomplished using conventional capillary devices, and current state-of-the-art alternatives are comparatively large. Recently, approaches based on thermal phase change have been proposed. In these phase change propellant management devices (PMDs), the propellant is vaporized in one portion of the tank through the application of heat and condensed in cooler portions due to increased pressure. Experimental results presented here show that ullage bubbles can be repositioned in a thermally insulative nylon tank using less than 5 W of input power. Test data and models indicate that the thermal conductivity of the tank has a significant effect on the efficiency of a phase change PMD when the heat source makes direct contact with the wall. The position of the heater is also shown to have a major impact on performance. Appropriate heater positioning could allow phase change PMDs to be used in tanks constructed of any material in microgravity.