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 highly accurate unified solver for prediction of mixed continuum-rarefied flows with contaminant dispersal. This will enable better understanding and prediction of thermal and force loading and contamination of spacecraft components, and enable design of a new era of safer next-generation in-space propulsion systems. Phase I will demonstrate improved modeling fidelity and provide great insight into in-space thruster plume contaminant environments. Phase II will bring the complete predictive capabilities to production for detailed investigations into contaminant environments for full spacecraft configurations.

Benefits: The proposed computational architecture for prediction of plume flow impingement and contaminant dispersal through mixed continuum-rarefied flow environments combines multiple novel computational approaches into one unified simulation environment. This technology will be highly beneficial to NASA and its contractors for prediction and analysis of contaminants and particulate transport and interaction in near-vacuum conditions for in-space propulsion applications. Direct benefits include risk reduction through improved fidelity simulations of thruster plume molecular and droplet contamination reaching spacecraft surface insulation, optical sensors and sensitive instruments. Direct NASA applications include supporting spacecraft design with most advantageous thruster placement and design mitigation measures such as shielding through simulation based engineering. 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.