Shock Radiation Tests for Saturn and Uranus Entry Probes

Cruden, Brett A.; Bogdanoff, David W.

doi:10.2514/6.2015-2965

Cited by 6 publications

(7 citation statements)

References 23 publications

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“…9. Although not definitive, this generally agrees with the observations of Lyman-α radiation in the pre-shock region which Cruden 3 concluded was due to atomic hydrogen diffusing upstream of the shock. In Ref.…”

Section: B East Shot 25 Simulationsupporting

confidence: 85%

“…Having tested the DSMC code on a 0-dimensional relaxation, it was next applied to simulate Shot 25 from a recent campaign in the EAST for Saturn entry conditions. 3 The inflow conditions simulated in this scenario are listed in Table 4 and DSMC shock results are shown in Figs. 9-10 for EAST Shot 25, which had an initial pressure of 0.2 Torr and reached a shock velocity of 27.8 km/s.…”

Section: B East Shot 25 Simulationmentioning

confidence: 99%

“…In Ref. 3, it was determined that optically thick radiation would be seen for atomic hydrogen number densities as low as 1.0×10 18 m -3 . The DSMC simulation predicts H number densities this large as far as 1.2 cm upstream of the shock suggesting again that this upstream H could be emitting if it is hot enough.…”

Section: B East Shot 25 Simulationmentioning

confidence: 99%

“…The length until complete dissociation of H 2 is nearly three times larger than for Shot 25 and no ions besides H + are present downstream. In this shot, α line measurements were used by Cruden 3 to calculate a constant electron density of approximately 5.0×10 20 m -3 throughout the post-shock region, though the actual values may have been lower due to resolution limitations. In Ref.…”

Section: East Shot 17 Simulationmentioning

confidence: 99%

“…2 To mitigate this uncertainty, shock tube tests in the Electric Arc Shock Tube (EAST) at the NASA Ames Research Center were performed for a range of Saturn entry trajectory conditions. 3 These tests were performed in a hydrogen-helium mixture (89%:11% by volume) for a set of freestream velocities between 25-30 km/s and 0.1-0.5 Torr. The results of these experiments found that quantities in the postshock region did not reach the expected equilibrium values and that radiative heating may not play a significant role.…”

Section: Introductionmentioning

confidence: 99%

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DSMC Shock Simulation of Saturn Entry Probe Conditions

Higdon

Cruden

Brandis

et al. 2016

46th AIAA Thermophysics Conference

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This work describes the direct simulation Monte Carlo (DSMC) investigation of Saturn entry probe scenarios and the influence of non-equilibrium phenomena on Saturn entry conditions. The DSMC simulations coincide with rarefied hypersonic shock tube experiments of a hydrogen-helium mixture performed in the Electric Arc Shock Tube (EAST) at the NASA Ames Research Center. The DSMC simulations are post-processed through the NEQAIR line-by-line radiation code to compare directly to the experimental results. Improved collision cross-sections, inelastic collision parameters, and reaction rates are determined for a high temperature DSMC simulation of a 7-species H2-He mixture and an electronic excitation model is implemented in the DSMC code. Simulation results for 27.8 and 27.4 km/s shock waves are obtained at 0.2 and 0.1 Torr, respectively, and compared to measured spectra in the VUV, UV, visible, and IR ranges. These results confirm the persistence of non-equilibrium for several centimeters behind the shock and the diffusion of atomic hydrogen upstream of the shock wave. Although the magnitude of the radiance did not match experiments and an ionization inductance period was not observed in the simulations, the discrepancies indicated where improvements are needed in the DSMC and NEQAIR models. Nomenclature , , , = parameters in the viscosity integral calculation = Millikan-White temperature constant = Millikan-White constant d ref = VHS reference diameter (m) = activation energy (J) = electronic excitation degeneracy at level j = Boltzmann constant (= 1.3806503×10-23 m 2kg/s 2-K)

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Section: B East Shot 25 Simulationsupporting

confidence: 85%

Section: B East Shot 25 Simulationmentioning

confidence: 99%

Section: B East Shot 25 Simulationmentioning

confidence: 99%

Section: East Shot 17 Simulationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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DSMC Shock Simulation of Saturn Entry Probe Conditions

Higdon

Cruden

Brandis

et al. 2016

46th AIAA Thermophysics Conference

Self Cite

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Calculating shock arrival in expansion tubes and shock tunnels using Bayesian changepoint analysis

James

Gildfind

2018

Exp Fluids

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The influence of shock speed variation on radiation and thermochemistry experiments in shock tubes

Collen¹,

Mare²,

Mare³

et al. 2022

J. Fluid Mech.

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Shock tubes are a crucial source of experimental data for the aerothermodynamic modelling of atmospheric entry vehicles. Notably, many chemical-kinetic and radiative models are validated directly against optical measurements from these facilities. Typically, the incident shock speed at the location of the experimental measurement is taken to be representative of the test slug; however, the shock velocity can vary substantially upstream of this location. These variations have been long posited as a source of disagreement with computational predictions, although a definitive link has proved elusive. This work describes a series of experiments which aim to isolate and confirm the importance of the shock deceleration effect. This is achieved by generating different shock trajectories and comparing the post-shock trends in atomic oxygen emission and electron density. These trends are shown to be directly linked to the upstream shock speed variations using a recently developed numerical tool (LASTA). The close agreement of the comparisons confirms the importance of shock speed variation for shock tube experiments; these findings have direct and potentially critical relevance for all such studies, both past and present.

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Shock Radiation Tests for Saturn and Uranus Entry Probes

Abstract: This paper describes a test series in the Electric

Cited by 6 publications

References 23 publications

DSMC Shock Simulation of Saturn Entry Probe Conditions

DSMC Shock Simulation of Saturn Entry Probe Conditions

Calculating shock arrival in expansion tubes and shock tunnels using Bayesian changepoint analysis

The influence of shock speed variation on radiation and thermochemistry experiments in shock tubes

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