Assessment of Propellant Droplet Contamination Effects on the Europa Clipper Spacecraft

NASA's Europa Clipper spacecraft will carry nine science instruments to investigate whether Jupiter’s moon Europa has an environment that could support life. Europa Clipper is the largest spacecraft NASA has flown for a planetary mission. With solar arrays fully extended the spacecraft spans over 30 meters. At launch, nearly half of Europa Clipper’s mass is propellant which will be consumed during travel to Jupiter, inserting the spacecraft into orbit around Jupiter, and to perform almost 50 flybys of Europa. Europa Clipper’s propulsion system has 24 bipropellant engines which will process nearly 2750 kg of fuel and oxidizer during the course of the mission. During propulsion system operation liquid droplets of unburned fuel and oxidizer are expelled from the engines. An empirical bipropellant plume contamination model that was originally developed for International Space Station thrusters was applied to investigate droplet effects on the Europa Clipper spacecraft. Unburned propellant droplets can cause damage to spacecraft materials by chemical reactions and mechanical damage exhibited by pitting surfaces. Bounding estimates for propellant droplet fluxes to Europa Clipper surfaces were obtained using the empirical model. Based on material testing results, estimates of damage to materials used for thermal blankets, solar arrays, and instruments were assessed to determine the impact to spacecraft thermal, power and science systems. Where needed, design changes were made to mitigate deleterious effects caused by propulsion system operation.