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ABLATION EXPERIMENTS WITH PLASTICS AT HYPERSONIC SPEEDS AND AT LOW HEAT-TRANSFER RATES,
DAVID TAYLOR MODEL BASIN WASHINGTON D C
The ablation behavior of the plastics polyethylene, Teflon, and polycarbonate has been studied for various model configurations. Tests were conducted at Mach numbers of 7.0 and 9.3 and at low convective heating rates with stagnation temperatures about 1350F and stagnation pressures about 300 psia. A few initial tests concerned a flat-plate shape and a flat-faced disk shape. These tests included melt flow observations and some crude comparison studies of the various materials. The remaining tests, which represent the bulk of this investigation, concerned two dozen plastic coneshaped models which were exposed to wind tunnel conditions for various durations up to 60 seconds. Shape change studies were made of these conical models using as control devices, ablation rods ejected from the apex and flowseparation ablation spikes. It was seen that, with proper matching of materials, shape changes in the conical models could be virtually eliminated by means of apex ejection. The ablation spikes were found to maintain a conical apex region by shifting the heat load downstream where it could be absorbed with relatively little shape change. Author