Analytical and Experimental Evaluation of Aerodynamic Thrust Vectoring on an Aerospike Nozzle

Results from analytical and experimental investigations of aerodynamic thrust vectoring on a small-scale aerospike thruster are presented. The thrust vectoring system uses four secondary injection ports located at approximately 50% of the nozzle length. The nozzle was truncated at 57% of its theoretical length to enhance manufacturability. The resulting low-pressure base-area decreases overall thrust levels, and this effect is partially compensated-for by injecting mass from the nozzle base area. Two-dimensional method-of-characteristics techniques were used to size the system, and allowed calculation of the desired nozzle contours. CFD computations verified the method–of-characteristics solutions, and were used to visualize the associated secondary injection flow phenomena. Analytical calculations are correlated with experimental data measured with a custom-designed 6-degree-of-freedom thrust stand. In-situ calibration procedures for the thrust stand are presented. Data derived from cold-flow thrust vectoring tests with carbon dioxide as the working fluid are presented. These data demonstrate that the injected secondary flow pulses produce substantial side forces. These forces crisply reproduce input pulses with a high degree of fidelity. The achieved side force levels are approximately 1.5% of the total thrust level. Cold flowtests do not verify existence of an aerodynamic multiplying effect on the generated impulsive side force.