Leak Mitigation in Mechanically Pumped Fluid Loops for Long Duration Space Missions

Abstract

Mechanically pumped fluid loops (MPFLs) are increasingly considered for spacecraft thermal control. A concern for long duration space missions is the leak of fluid leading to performance degradation or potential loop failure. An understanding of leak rate through analysis, as well as destructive and non-destructive testing, provides a verifiable means to quantify leak rates. The system can be appropriately designed to maintain safe operating pressures and temperatures throughout the mission. Two MPFLs on the Mars Science Laboratory Spacecraft, launched November 26, 2011, maintain the temperature of sensitive electronics and science instruments within a -40°C to 50°C range during launch, cruise, and Mars surface operations. With over 100 meters of complex tubing, fittings, joints, flex lines, and pumps, the system must maintain a minimum pressure through all phases of the mission to provide appropriate performance. This paper describes the process of design, qualification, test, verification, and validation of the components and assemblies employed to minimize risks associated with excessive fluid leaks from pumped fluid loop systems. NomenclatureCFC = Chlorofluorocarbon CHRS = Cruise Heat Rejection System CIPAS = Cruise Integrated Pump Assembly System FEM = Finite Element Model GHe = Gaseous Helium HRS = Heat Rejection System JPL = Jet Propulsion Laboratory MMPDS = Metallic Materials Properties Development and Standardization MMRTG = Multi-Mission Radioisotope Thermoelectric Generator MPFL = Mechanically Pumped Fluid Loop MSL = Mars Science Laboratory RAMP = Rover Avionics Mounting Plate RHRS = Rover Heat Rejection System RIPAS = Rover Integrated Pump Assembly System SCC = Standard Cubic Centimeter