Chemical Flow Modeling for Enhanced Analysis of Contamination Experiments

Underlying the many models for simulating space contamination effects are the rates for fundamental chemical processes. The rates are generally not known and are difficult to measure, but are critical for meaningful simulations. Molecular Beam Experiments (MBE), which are typically used to determine them, produce large uncertainties in derived rates arising from uncertainties in the flow field of reacting molecules, and only cover a small portion of the parameter space of interest. We propose an analysis approach coupling fundamental computational chemistry tools to the SOCRATES Direct Simulation Monte Carlo (DSMC) flow field code to provide an accurate simulation of MBEs. This will enable a much more accurate extraction of fundamental rates from MBE data and also allow the rate constant to be extrapolated with confidence to the entire application parameter space of interest. The Phase I technical objectives are: (1) Adapt SOCRATES to simulate MBEs, (2) Validate the approach using gas phase MBE data, and (3) Formulate a gas-surface computational chemistry-flow field model. The extension of the approach to model gas-surface MBE data is more complex and will be formulated in Phase I for implementation and experimental validation in Phase II.