Development of a Total Enthalpy and Reynolds Number Matched Apollo Re-entry Condition in the X2 Expansion Tunnel

This paper reports on the development of an expansion tunnel condition based on the peak heating point of the Apollo 4 trajectory. Particular emphasis is placed on replicating the total enthalpy and post-shock Reynolds number of the flow such that representative re-entry heating rates are generated. An analytical state-to-state facility model, PITOT, is used to perform the initial condition design using a secondary driver to increase performance. Deviations from ideal theory are seen when performing initial experiments, and no performance gain was evident using the secondary driver, possibly due to the thick Mylar secondary diaphragm. Nonideal facility performance is assessed and incorporated into the modelling whereupon a condition is chosen that closely matches the desired flow properties.