Active Insulation Technique Applied to the Experimental Analysis of a Thermodynamic Control System for Cryogenic Propellant Storage

Abstract

A technological barrier for long-duration space missions using cryogenic propulsion is the control of the propellant tank self-pressurization (SP). Since the cryogenic propellant submitted to undesired heat load tends to vaporize, the resulting pressure rise must be controlled to prevent storage failure. The thermodynamic vent system (TVS) is one of the possible control strategies. A TVS system has been investigated using on-ground experiments with simulant fluid. Previous experiments performed in the literature have reported difficulties to manage the thermal boundary condition at the tank wall; spurious thermal effects induced by the tank environment spoiled the tank power balance accuracy. This paper proposes to improve the experimental tank power balance, thanks to the combined use of an active insulation technique, a double envelope thermalized by a water loop which yields a net zero heat flux boundary condition and an electrical heating coil delivering a thermal power Pc∈[0−360] W, which accurately sets the tank thermal input. The simulant fluid is the NOVEC1230 fluoroketone, allowing experiments at room temperature T ∈ [40–60] °C. Various SP and TVS experiments are performed with this new and improved apparatus. The proposed active tank insulation technique yields quasi-adiabatic wall condition for all experiments. For TVS control at a given injection temperature, the final equilibrium state depends on heat load and the injection mass flow rate. The cooling dynamics is determined by the tank filling and the injection mass flow rate but does not depend on the heat load Pc.