Buffet loads on Shuttle Thermal Protection System tiles

Abstract

This paper presents results of wind tunnel and acoustic tests to investigate buffet loads on Shuttle Thermal Protection System (TPS) tiles. It also describes the application of these results to the prediction of tile buffet loads for the first Shuttle flight into orbit (STS-1). The tests were conducted in wind tunnels at transonic and supersonic Mach numbers and in a progressive wave tube. The wind tunnel tests included single tiles of various thicknesses and arrays of tiles mounted on both rigid and elastic substructures. The corresponding acoustic tests were of the single tiles only. In most cases the “test” tiles were of Orbiter qualified material and they were bonded to the panels and proof-loaded in accordance with flight-vehicle specifications. The fixtures for the panel installations in the wind tunnels were designed to simulate flow regions on the Orbiter where shock waves and related high pressure gradients and high dynamic loads would occur. The results of the wind tunnel tests indicate that significant tile buffet loads occurred due to separated flows and oscillating shocks. Separated flow excitation caused higher buffet loads than oscillating shocks for a given level of excitation, however, the highest combined steady and dynamic loads occurred when shock waves with ΔP > 1.5 psi were on tiles.