High-Fidelity Prediction of Launch Vehicle Lift-off Acoustic Environment

Launch vehicles experience extreme acoustic loads during liftoff driven by the interaction of rocket plumes and plume-generated acoustic waves with ground structures. Currently employed predictive capabilities to model the complex turbulent plume physics are too dissipative to accurately resolve the propagation of acoustic waves throughout the launch environment. Higher fidelity liftoff acoustic analysis tools to design mitigation measures such as deluge water and launch pad geometry are critically needed to optimize launch pads for SLS and commercial launch vehicles. This STTR project will deliver breakthrough technologies to drastically improve predictive capabilities for launch vehicle lift-off acoustic environments. Hybrid RANS/LES modeling presently established in NASA production flow solvers will be used for simulation of the acoustic generation physics, and a high-order accurate unstructured discontinuous Galerkin (DG) solver developed in the same production framework will be employed to accurately propagate acoustic waves across large distances. An innovative hybrid CFD-CAA method will be developed in which the launch-induced acoustic field predicted from hybrid RANS/LES will be transmitted to a DG solver and propagated using high-order accurate schemes ideal for acoustic propagation modeling. This new paradigm enables: (1) Improved fidelity over linear methods for modeling nonlinear launch-induced acoustics; (2) Greatly reduced numerical dissipation and dispersion; and (3) Improved acoustics modeling for attenuation, reflection, and diffraction from complex geometry. The merits of the proposed approach will be investigated and demonstrated in Phase I for benchmark CAA applications and plume impingement problems. In Phase II, the methodology will be refined and validated against realistic targeted applications.

This hybrid CFD/CAA tool will uniquely fill the technology gap at NASA centers in defining lift-off environments for ongoing 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, ATK, Boeing, Space-X, Orbital Sciences, and payload system and sensitive instrument developers, particularly for one-of-a-kind DoD, NRO, and NOAA satellites. At the end of the 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.

This is early/mid-stage (TRL 3) — the most realistic path in is NASA SBIR/STTR, which funds small businesses and research institutions to develop technology aligned with NASA's needs (equity-free, phased funding). Check whether a current SBIR/STTR solicitation topic overlaps with this project's technology area, or contact the project directly (above) to ask.

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