Aeroacoustics Coupled with CFD for GBSD Silo Flyout & Stage Separation

Propulsive exhaust plumes, whether emanating from an aircraft engine or a rocket, generates an intense aeroacoustic environment with levels of sound that are very damaging to surrounding structures. When a missile is launched from within an enclosure such as the silo, the fluid/acoustic interactions (aeroacoustics) are amplified due to repeated reflections that result in high structural loading of the missile body. Proper design of the fuselage, structure, and payload is required so that mission objectives are not compromised by damage caused by the aeroacoustic environment during launch. The same aeroacoustic-induced sideload phenomena has also been observed during in flight during stage separation. The initially low thrust of the upper stage exhaust encounters difficulty in expanding into a high dynamic pressure freestream until the thrust levels climb sufficiently and the stages begin separating. Unfortunately, the potential onset of a large enough nozzle sideload during this critical period provides an opportunity for the separating stages to become misaligned (or cocked) from which recovery is not guaranteed due to the limited control authority available at the initially low thrust of the upper stage motor. CRAFT Tech will leverage its prior aeroacoustics modeling experiences. A very efficient, accurate and fast computational method for solving the aeroacoustic environment induced by rocket motor plumes will be demonstrated, including identification of the incident frequency spectrum during launch as well as IOP. The tools demonstrated for the silo application will also be applied to a notional GBSD (Ground Based Strategic Deterrent) stage separation event to assess the potential for onset of nozzle sideloads. This aeroacoustics coupled Computational Fluid Dynamic (CFD) modeling capability will also be applicable to pad launch, shroud separation and powered free flight. CRAFT Tech’s is teaming with the National Center for Physical Acoustics (NCPA) at the University of Mississippi for the proposed Direct-to-Phase II (D2P2) effort. NCPA will perform high resolution measurements utilizing an existing enclosed plume setup that is being used to generate laboratory data in support of GBSD. CRAFT Tech and NCPA will employ high resolution gages and non-intrusive optical diagnostics to generate complementary high-fidelity data sets with detail not available at larger scale and with careful attention to boundary conditions. The data sets will be utilized to conduct validation of a unified computationally-efficient aeroacoustic and rocket plume modeling model in a silo environment. It will support implementation of efficiency strategies for high throughput simulations. The resulting benefit to AFNWC will be a validated, rapid turnaround capability to perform detailed analyses of launch events, stage separation, evaluation of other configurations, etc.