A Cost-Effective Approach to Evaluate High-Temperature Ablatives for Military Applications

Abstract

Several methods for evaluating thermal performance of ablative materials under simulated solid rocket exhaust plumes are presented in this paper. A small-scale supersonic rocket motor facility capable of delivering more than 700 Btu/s-ft2 (7,947 kW/m2) was used to simulate the rocket motor environment in the laboratory. A particle feeder with the capability of injecting 40 lb/hr (5.0 gm/s) of aluminum oxide (Al2O3) particles into the flow stream was used to simulate the particle impingement effects of solid rocket exhaust. Application of several gauges for heat flux measurement is discussed in this paper. These gauges include a circular foil calorimeter (Gardon), flat plate calorimeter, and pencil probe surface thermocouple. Several techniques for erosion measurement are also presented. These techniques consist of a linear variable differential transformer (LVDT), eddy current device, ultrasonic device, and laser-based sensor. The operation principle of the LVDT and laser-based sensors is presented, and some typical results are shown. High-speed motion and video analyses were performed to study material surface behavior during testing. Scanning electronic microscope (SEM) analyses were also performed on ablatives to study subsurface structure behavior during ablation. A cost-effective approach was developed to evaluate high-temperature ablatives for military applications.