Experimentally Driven Performance Model for the Baffled-Tube Ram Accelerator

Abstract

The baffled-tube ram accelerator is a hypervelocity mass driver with the capability to become a reusable space launch technology. The device is a derivative of a smooth-bore ram accelerator in that it uses a series of washer-like internal baffles, normal to the tube wall, as obstructions to attenuate the combustion-driven shock wave system associated with the ram accelerator's propulsive cycle. The device with baffles normal to the wall produces 30-100\% more thrust than the conventional smooth-bore ram accelerator. The attenuation effected by the baffles allows for higher energy propellants to be utilized, thus enabling a higher level of thrust to be produced. However, compared to the performance model of the ram accelerator, the normal-baffled-tube only produces a fraction of the predicted thrust. To realize the full potential of the device a set of slanted internal baffles was designed, manufactured, and tested. The slanted baffles were tested with both an inward slant and outward slant configuration with respect to the direction of motion. From preliminary tests outward slanted baffles showed a ~41\% increase in thrust with ~20\% more diluent in the propellant mixture than in the normal-baffled-tube, which, however, was still less than predicted. A modified performance model was developed to accounted for the combustion efficiency of the baffled-tube ram accelerator. This model has shown the combustion efficiency plays a predominant role in the under-performance of the baffled-tube ram accelerator. Furthermore, by coupling the combustion efficiency and baffle drag the model lent insight into how the ram accelerator performed differently with baffles. The slanted-baffled-tube experiments are presented along with the results of the modified performance model, as applied to the experimental data for both baffle geometries.