Green Propellant Infusion Mission Plume Impingement Analysis

The Green Propellant Infusion Mission (GPIM) is a Technology Demonstration Mission (TDM) project, sponsored by NASA’s Space Technology Mission Directorate (STMD). The goal of GPIM is to demonstrate the capability of a green propulsion system, specifically, one using the monopropellant, AF-M315E. The GPIM propulsion system will be flown as a payload on a Ball Aerospace BCP-100, a small, standardized spacecraft. The propulsion system will have one 22 N thruster for primary divert manuevers and four 1 N thrusters for attitude control. One of the risks identified for GPIM is potential contamination of sensitive areas of the spacecraft from the effluents in the plumes of AF-M315E thrusters. NASA Glenn Research Center (GRC) is conducting activities to mitigate the AF-M315E plume risk. The plume risk mitigation activities include modeling the plume flow fields of the AF-M315E thrusters, assessing the plume impingement on the BCP-100 spacecraft including the impact on the power generating capabilities of the solar arrays, and conducting ground-based plume measurements on an AF-M315E thruster to correlate the plume modeling with plume data. This paper describes the preliminary results from the first activity, plume modeling and plume impingement analysis. Plume flow fields of the 22 N and 1 N thrusters have been modeled using both the method-of-characteristics based Reacting And Multi-Phase (RAMP2) code and the Hypersonic Aerothermodynamics Particle (HAP) Direct Simulation Monte Carlo (DSMC) code. The density and temperature plume flow fields are presented, as well as species concentration at different locations in the plume. Chamber pressures from 400 psia to 100 psia are examined, simulating the GPIM propulsion system operating in blowdown mode. Both equilibrium and frozen flow assumptions are also investigated. The plume impingement on the BCP-100 spacecraft are evaluated, using both the PLume IMPingement program (PLIMP) and also HAP. The heating rates on the spacecraft surfaces are found to be fairly benign. Species flux on the surfaces are also examined, with hydrogen gas found to be the dominant species in the backflow region. The simulations from both models are planned to be compared to forthcoming plume measurement data, when AFM315E thruster testing is conducted.