DSMC Simulations for Cupid’s Arrow

Speaker: Arnaud Borner, Science and Technology Corporation / NASA Ames Research Center
September 17, 2020

Presentation

Abstract

This presentation will discuss hypervelocity sampling in the upper atmosphere of Venus, with respect to the Cupid’s Arrow mission concept, in which a stand-alone small spacecraft (~80 cm diameter, sphere/cone geometry) is designed to skim through the Venus upper atmosphere and acquire gas samples below the homopause altitude, where the different atmospheric compounds are expected to be well mixed. The velocity of the spacecraft where sampling would occur is expected to be between 10.5 km/s and 13.1 km/s, depending on the trajectory chosen. The altitude during sampling operations is expected to be around 110 km. QITMS, a miniaturized quadrupole ion trap mass spectrometer developed at JPL, will be used to measure the noble gas concentrations in the acquired gas samples. In order to ensure that it is possible to relate the composition of the sampled gases to the free stream atmospheric composition, numerical simulations are used to model the flow through the Cupid’s Arrow sampling system. In particular, an emphasis is placed on quantifying fractionation that occurs during the sample acquisition process in order to determine how measured isotopic ratios of noble gases in the sample compare to actual isotopic ratios in the Venus atmosphere.

The Direct Simulation Monte Carlo (DSMC) code SPARTA, an open source software package developed by Sandia National Laboratories, is used in this work. SPARTA, based on Bird’s DSMC method, is a molecular-level gas-kinetic technique. As SPARTA is able to model hypervelocity reacting flows in strong chemical and thermal non-equilibrium, this software package is well suited to determine relevant flow properties for the Cupid’s Arrow mission concept, and to numerically quantify the expected level of elemental and/or isotopic fractionation in the sample acquired by Cupid’s Arrow. This presentation will show results from 3D simulations quantifying the predicted noble gas isotopic fractionation in the gas acquired at hypervelocity speeds

Biography

Arnaud Borner is a senior research scientist for the Science and Technology Corporation working in the Computational Physics Branch of the NASA Advanced Supercomputing Division at NASA's Ames Research Center. He received the NASA Group Achievement Award in 2017 as part of the ESM Micro-Scale TPS Modeling Team For exceptional engineering achievement in developing revolutionary capability for predictive modeling of TPS performance from first principles. Borner joined the Predictive Materials Modeling (PMM) group at NASA in September 2014. He obtained his PhD in Aerospace Engineering from the Pennsylvania State University in 2014, working under the supervision of Prof. Debbie Levin from 2009 to 2014. His dissertation, entitled “Use of Advanced Particle Methods in Modeling Space Propulsion and its Supersonic Expansion”, focused on the use of Molecular Dynamics (MD) and direct simulation Monte Carlo (DSMC) codes in rarefied environments. Borner also holds a MS in Aerospace Engineering for the Pennsylvania State University (2009) and a MS in Engineering from the Ecole Centrale de Lyon in France (2008). He has been one of the developers of the SPARTA DSMC code since joining NASA in 2014.