Abstract

Understanding and accurately modeling the acoustic sources and propagation of high-intensity tactical jet aircraft and rocket noise is essential for vehicle design, environmental impact assessment, and mitigation strategies. Despite progress in the understanding of these sources, significant challenges persist in both predictive modeling and noise mitigation. This dissertation advances both the characterization of full-scale supersonic tactical jet aircraft noise sources and the development of modern empirical prediction models for rocket launch noise. Across multiple measurement campaigns and modeling efforts, the work integrates advanced array signal processing, high-fidelity field measurements, and improved empirical methods to expand the physical understanding of source mechanisms and deliver accurate, practical prediction tools. The first portion of this work focuses on acoustic source characterization for a full-scale, installed GE F404 engine operating at afterburner. Using coherence-based partial field decomposition methods, implemented via an equivalent source reconstruction with acoustical holography, apparent source distributions are resolved across frequency. A bandwidth extension technique employing array phase-unwrapping and interpolation enables detailed mapping of local maxima, distinct in frequency and space, along the nozzle lipline. Analysis reveals distinct subsources--ranging from possible large-scale turbulence in the convectively subsonic region to likely Mach wave radiation originating throughout the shear layer--along with regions of mixed source contributions producing spatiospectral lobes. Subsequent analysis addresses broadband shock-associated noise (BSN), a dominant high-frequency component in imperfectly expanded supersonic jets. Full-scale measurements from the installed F404 engine on the T-7A trainer aircraft identify BSN sources along the nozzle lipline, corroborated by in-situ imaging. Measured shock spacing deviates from current analytical predictions, impacting the performance of established BSN frequency models; however, accuracy is restored when models are corrected using measured shock cell spacing. Coherence analysis demonstrates coupling between upstream-directed BSN and downstream Mach wave radiation, as well as elevated coherence between shock cells, indicating a partially coherent, spatially distributed BSN source. Building on these source characterization efforts, a field measurement campaign measured the acoustic environment surrounding the Atlas V JPSS-2 launch from Vandenberg Space Force Base. Eleven measurement stations, ranging from 200 m to 7.7 km at multiple azimuthal angles, captured several details of the launch acoustics. These include both a 30 dB variation in ignition overpressure peak levels due to flame trench directionality and potential azimuthal asymmetry in the radiated noise field. These data form the foundation for subsequent empirical model development. A new set of simplified predictive relationships is presented for estimating overall acoustic power levels and maximum overall sound pressure levels from heated supersonic aircraft jet engines and rockets. Based on fundamental flow properties, these models demonstrate strong predictive performance for Atlas V and Vulcan Centaur launches, as well as for the installed GE F404 engine across several operating conditions, achieving root mean square errors of less than 2 dB for maximum unweighted sound levels. The final contribution is SATURN (Scientific Acoustic Tool for Understanding Rocket Noise), a modular, open research model that modernizes the legacy NASA SP-8072 framework. SATURN incorporates high-fidelity acoustic parameters derived from the Atlas V 401 dataset and an empirically derived propagation loss model for spectral levels. Validation against Firefly Alpha and SpaceX Starship launches yields 34 independent validation points over a broad range of distances. SATURN predicts the unweighted levels near peak radiation with a root-mean-square error of ~1 dB within 20 km, representing a factor of two or more improvement in acoustic pressure accuracy over SP-8072. Collectively, this work provides new physical insights into the source mechanisms of full-scale supersonic jets, delivers improved empirical tools for rocket noise prediction, and establishes a validated, modular modeling framework for future launch noise prediction applications. The combination of high-fidelity measurements, advanced source decomposition, and modernized prediction models offers a pathway toward more accurate and flexible acoustic assessment capabilities for aerospace applications.

Degree

PhD

College and Department

Computational, Mathematical, and Physical Sciences; Physics and Astronomy

Rights

https://lib.byu.edu/about/copyright/

Date Submitted

2025-08-20

Document Type

Dissertation

Keywords

rocket noise, jet noise, broadband shock-associated noise, acoustical holography, coherence, signal processing, acoustics

Language

english

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