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Hypervelocity Shock Tunnel Studies of Blunt Body Aerothermodynamics in Carbon Dioxide for Mars Entry

Citation

Leibowitz, Matthew Gregory (2020) Hypervelocity Shock Tunnel Studies of Blunt Body Aerothermodynamics in Carbon Dioxide for Mars Entry. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/chyn-ea06. https://resolver.caltech.edu/CaltechTHESIS:05272020-173051776

Abstract

A low mass and reliable thermal protection system for Martian atmospheric entry requires an accurate prediction of the aerothermal environment encountered by the spacecraft. In order to move forward with predictive models for larger vehicles needed for manned and sample return missions, anomalous data needs to be resolved. This work aims to address two critical problems relevant for Mars missions.

I) We investigate significant discrepancies between experimental and simulated blunt body bow shock standoff distance in ground test facilities. Experiments using high-speed and high-resolution schlieren imaging are conducted in the T5 reflected shock tunnel and the Hypervelocity Expansion Tube (HET) to examine facility independence of the measurements. A recently-developed model for sphere and sphere-cone behavior is in good agreement with experiments, and with predictions from Navier-Stokes simulations with thermal and chemical nonequilibrium. The need to account for the divergence of the streamlines in conical nozzles is highlighted. The contributions of vibrational and chemical nonequilibrium to the stagnation-line density profile are quantified using the simulation results in order to compare different reaction rate models.

II) We measure and characterize carbon dioxide mid-wave infrared radiation in hypervelocity flow. Initially assumed negligible in the design of the Mars Science Laboratory (MSL) mission heat shield, this mechanism of heating must be considered for accurate predictions of the heating environment. Specifically, carbon dioxide radiation can be a dominant source of heating in the afterbody, particularly later in the trajectory at lower velocities. Presented are spectral measurements of the 4.3 μm fundamental band of carbon dioxide radiation measured using fiber optics embedded on the surface of an MSL scaled heat shield model. When comparing experiments and simulations, good agreement is found when running the HET in shock tube mode where the shock layer is optically thick, while discrepancies are observed in expansion tube mode where the shock layer is optically thin. A thorough analysis of flow features in the line-of-sight including freestream uncertainties is performed to explore possible reasons for this discrepancy. After developing the spectroscopic calibration technique and obtaining forebody measurements in the expansion tube, an experimental campaign is completed in the T5 Reflected Shock Tunnel to measure spectral radiation in the forebody and afterbody. The accompanying T5 simulations needed for radiation predictions are being carried out by NASA Ames.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:hypervelocity, standoff distance, sphere-cone, mid-wave infrared radiation, Mars entry
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Aeronautics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Austin, Joanna M.
Group:GALCIT
Thesis Committee:
  • Shepherd, Joseph E. (chair)
  • Hornung, Hans G.
  • Blanquart, Guillaume
  • Austin, Joanna M.
Defense Date:16 January 2020
Funders:
Funding AgencyGrant Number
NASA80NSSC19K0837
NASANNX16AO55G
NASANNX14A097A
NASANNX14AM59H
Record Number:CaltechTHESIS:05272020-173051776
Persistent URL:https://resolver.caltech.edu/CaltechTHESIS:05272020-173051776
DOI:10.7907/chyn-ea06
Related URLs:
URLURL TypeDescription
https://doi.org/10.2514/6.2019-1555DOIArticle adapted for Chapters 3 and 5.
https://doi.org/10.2514/6.2018-1721DOIArticle adapted for Chapters 2 and 4.
ORCID:
AuthorORCID
Leibowitz, Matthew Gregory0000-0002-7297-2592
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:13726
Collection:CaltechTHESIS
Deposited By: Matthew Leibowitz
Deposited On:29 May 2020 17:51
Last Modified:16 Jan 2021 01:01

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