Simulating Gas Giant Atmospheric Entry Using Helium and Neon Test Gas Substitutions

Flight into the gas giant planets involves atmospheric entry velocities between 20 and , which are mostly beyond the capabilities of current ground testing facilities that make use of test models. Using an expansion tube, this paper investigates how increasing the percentage of helium in the test gas, or substituting the helium for the heavier noble gas neon, can be used to generate representative shock-layer conditions associated with Uranus and Saturn entry. Theoretically, it was found that either test gas substitution should make it possible to simulate Uranus or Saturn entry shock layers, which was confirmed experimentally for the helium substitution. Lower percentages of the substituted gas were required for neon; however, the helium substitution was found to be able to maintain the flow stagnation enthalpy in the driven sections of the facility with changing diluent fraction. Noting the current interest in sending atmospheric entry probes to both of these planets, this demonstrates that the required experimental capabilities are available for performing simulated experiments using test models.