Description: Chemical contamination of spacecraft components as well as thermal and force loading from firing liquid propellant thrusters are critical concerns for in-space propulsion applications. Gas molecular contamination and liquid droplet deposition due to incomplete combustion threaten to damage surface materials, sensitive instruments and optical sensors, and poses major risks for mission success. Liquid propellant thrusters operate in space at near-vacuum conditions, and contaminants traverse a complex mixed continuum-rarefied environment upon exiting the thruster nozzle. Current CFD modeling capabilities for in-space propulsion analysis have made great strides, but fall short of providing the fidelity required to simulate the contaminant transport around the spacecraft with sufficient efficiency and accuracy. This STTR will develop and deliver an innovative computational architecture for prediction of plume flow impingement and contaminant dispersal through mixed flow environments for in-space propulsion analysis. CFDRC will supplement the massively parallel Loci framework with a unified solver for prediction of mixed continuum-rarefied flows with contaminant dispersal. This will enable better understanding of thermal and force loading and contamination of spacecraft components, and enable design of safer next-generation in-space propulsion systems. A proof-of-concept was developed and successfully demonstrated during Phase II for in-space thruster plume contamination environments. Phase II Extended and associated Phase III STMD GCD funding will enable adaptation and maturation of the software simulation technology to deliver production continuum-kinetic-particle predictive capabilities with advanced molecular gas models to support plume gas and plume-surface interaction predictions for human landing systems and other NASA missions.

Benefits: Direct benefits include risk reduction through improved predictions of plume-surface interaction, thruster molecular/droplet contamination reaching spacecraft surface insulation, optical sensors and sensitive instruments. Direct NASA applications include spacecraft design support with optimal thruster placement and design mitigation measures such as shielding through simulations. Other NASA applications include simulation of effectiveness of RCS thrusters in reentry capsule rarefied wake region.

Potential Non-NASA government and commercial applications include, assessment of thruster plume induced environments on commercial and military spacecraft, predicting the impact of particles scattered from thruster plumes on ballistic missile and missile interceptor signatures, and optimization of commercial satellite operational life through contamination minimization.