Optimal Thrust Vectoring for an Annular Aerospike Nozzle

Recent success of an annular aerospike flight test by NASA Dryden has prompted keen interest in providing thrust vector capability to the annular aerospike nozzle (AAN). The AAN with a moveable spike for thrust vectoring and throttling could provide a more efficient alternative to traditional bell nozzles. Cal Poly, which has a thrust vector research facility, has teamed with Rolling Hills Research Corporation, with CFD capability, to experimentally and analytically determine the optimal approach to thrust vectoring and throttling the AAN. In Phase I, several scale AAN models were fabricated with movable spikes that could be displaced and/or gimballed. One set of studies quantified thrust changes as a function of spike axial position for throttling. Other studies examined the thrust vectoring effectiveness of various proprietary nozzle configurations. Schlieren photography and 3-axis force measurements showed excellent correlation to predictions made with the OVERFLOW CFD code. The most promising of the nozzle configurations for thrust vectoring and throttling were shown to produce stable flow that generates a resultant turn angle whose magnitude is in the neighborhood of current rocket booster technology. These promising configurations have been selected for extensive laboratory testing and computational analysis for optimization in the Phase II program. The objective of Phase III will be flight test.