Transient Acoustic Environment Prediction Tool for Launch Vehicles in Motion during Early Lift-Off

Launch vehicles experience extreme acoustic loads dominated by rocket exhaust plume interactions with ground structures during lift-off, which can produce damaging vibro-acoustic loads on the vehicle and payloads if not properly understood and mitigated against. Existing capabilities for modeling the turbulent plume physics during early lift-off are too dissipative to accurately resolve the propagation of acoustic waves throughout the launch environment. Higher fidelity non-dissipative analysis tools are critically needed to design mitigation measures (such as water deluge) and launch pad geometry for current and future launch vehicles. This project will build upon existing capabilities to develop and deliver breakthrough technologies to drastically improve predictions of transient acoustic loading for launch vehicles in motion during early lift-off. Innovative hybrid CFD/CAA techniques based on RANS/LES modeling for acoustic generation physics and an unstructured discontinuous Galerkin method will be employed to model long distance acoustic wave propagation along with vehicle motion using ideally-suited high-order accurate schemes. This new paradigm enables: (1) Greatly reduced dissipation and dispersion; (2) Improved modeling of acoustic interactions with complex geometry; and (3) Automatic identification of transient acoustic environment including vehicle motion. Merits of this approach will be investigated and demonstrated during Phase I. In Phase II, the methodology will be refined and validated against realistic targeted applications.

The technology developed under this project will contribute to technology areas identified in multiple NASA Space Technology Area Roadmaps, notably, TA01 Launch Propulsion Systems, and TA13 Ground and Launch Systems Processing. This hybrid CFD/CAA tool will uniquely fill the technology gap at NASA centers in defining lift-off environments for on-going and new launch vehicle designs, and for the analysis of noise suppression techniques. The developed tool will provide greater confidence to NASA acoustics engineers offering accurate, quantitative acoustic loading predictions from first principle CFD/CAA simulations for specific launch vehicle configurations. The tool will also be invaluable to payload system and instrument developers, particularly for one-of-a-kind and experimental optics and telescope systems that are susceptible to acoustic effects during liftoff.

The proposed innovation offers significant advantages over aeroacoustic prediction tools currently available in industry. The hybrid RANS/LES and high-order DG modeling will provide a unique combination of robust multi-physics modeling and high-fidelity acoustic propagation physics. The proposed approach will offer a great technology advantage through its improved accuracy for acoustic propagation and its integration within a single massively parallel unified production framework (Loci). The toolset will be invaluable to current and future commercial launch service providers such as United Launch Alliance, Boeing, Space-X, Orbital ATK, and payload system and sensitive instrument developers, particularly for one-of-a-kind DoD, NRO, and NOAA satellites. At the end of this SBIR, this technology will be readily available for analysis of micro-jet and active/passive control systems, conventional and STOVL aircraft jet acoustics, airframe and landing noise, and rotorcraft acoustic loading.

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