Simulating Regolith Excavation, Entrainment, Dispersal and Visibility Impairment due to Rocket Plume-Surface Interaction via a Hybrid Continuum-Rarefied Flow Solver

With NASA planning to visit an asteroid and possible future missions to the Moon or Martian satellites, the effects of thruster plume impingement on the surfaces of these bodies must be better understood. Thruster firings near a regolith-covered surface will scour and accelerate dust and larger particles, creating a spray of debris that endangers the spacecraft and any nearby equipment. These particle jets may degrade thermal coatings and solar arrays, clog or damage robotic actuators, and severely reduce the effectiveness of optical sensors. Without accurate modeling of this particle behavior, mitigation techniques and safe operational plans cannot be developed. Utilizing a hybrid approach, with an established supersonic Navier-Stokes code handling the near field rocket plume and an in-house direct simulation Monte Carlo (DSMC) code determining flow in the transition and rarefied regime, I proposed to develop software that would allow analysis of various realistic proximity and landing scenarios. The key objectives of the research were to: (1) determine how complex configurations including pulsed thrust rockets and non-vertical nozzle attitudes alter the far field debris distribution, (2) understand how dust entrained in the gas flow effects the motion of larger pebble-sized [0.1 – 1 cm] regolith constituents and the hazard these may pose to spacecraft, and (3) how lofted dust adversely affects optical instruments and astronaut visibility. Given that the program period was less than a year and was ended before major research objectives were planned to be achieved, all accomplishments were in the area of synthesizing literature review into a specific research program and handling the logistics of the required supercomputing resources. For example, I decided which thruster I planned to model (R1-E) based on consultations with my NASA advisor and an evaluation of proposed mission architectures and concept of operations. I also obtained the required files to simulate these rocket plumes using NASA’s DPLR. I spent considerable time organizing and troubleshooting the secure supercomputing setup required by the ITAR DPLR software. Finally, I made several test runs of our group’s existing DSMC codebase to familiarize myself with its use and started code modifications to the critical particle patching routine.