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Date of Award

12-2006

Document Type

Thesis - Open Access

Degree Name

Master of Aerospace Engineering

Department

Aerospace Engineering

Committee Chair

Dr. Eric Perrell

Committee Member

Dr. William A. Engblom

Committee Member

Dr. Thomas R. Reinarts

Abstract

Knowledge of aerothermally induced convective heat transfer and plume induced radiative heat transfer loads is essential to the design of thermal protection systems (TPS) for launch vehicles. These loads are measured via the cylindrical heat flux gauges that are flush mounted with the outer surface of a launch vehicle and are exposed to the in-flight external thermal and velocity boundary layers as well as thermal radiation. Typically, Schmidt-Boelter gauges measure the incident heat flux based on the one-Dimensional Fourier's law. This instrumentation, when surrounded by low-conductivity insulation, has an exposed surface temperature significantly lower than the insulation. A substantial disturbance to the thermal boundary layer results, causing the heat flux incident on the gauge to be considerably higher (potentially by factors of 2 or more) than it would have been on the insulation had the gauge not been there. In addition, the gauge can receive energy radially from the hotter insulation, contributing to the increase of the indicated heat flux. The goal is to correct the gauge measurements to reflect the local heat flux on the insulation had the instrument not been present. The three major components of this effort include: 1) a three-dimensional, solid, thermal conduction model including the internal heat transfer details of a Schmidt-Boelter gauge and an installation surrounded by high temperature insulation, 2) a three-dimensional Navier-Stokes computational fluid dynamics (CFD) analysis to determine the effects of the rapidly changing thermal boundary layer over the near step changes in surface temperature, and 3) testing performed on physical models exposed to aerothermal and radiative environments in the Marshall Space Flight Center (MSFC) Improved Hot Gas Facility (IHGF) to calibrate the models. Much of the background research and testing was previously completed by the author, T. R. Reinarts, and M. L. Matson (Reinarts and Ford, 2004; Matson and Reinarts, 2002). This paper will focus on the effort to model the heat flux gauge under typical flight conditions. A brief summary of calibration issues and background will be presented, followed by the detailed analytical efforts, as well as an analysis of testing results and model calibration. Finally, recommendations will be made for flight data corrections.

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