NASA NTRS · 20240012190
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Brian M Howerton. AATT Propulsion Technologies: Advanced Liner Concept Development. https://ntrs.nasa.gov/citations/20240012190
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Rocket launches generate infrasound signatures that have been detected at great distances. Due to the sparsity of the networks that have made these detections, however, most signals are detected tens of minutes to hours after the rocket launch. In this work, a method of near-real-time detection of rocket launches using data from a network of smartphones located 10–70 km from launch sites is presented. A machine learning model is trained and tested on the open-access Aggregated Smartphone Timeseries of Rocket-generated Acoustics (ASTRA), Smartphone High-explosive Audio Recordings Dataset (SHAReD), and ESC-50 datasets, resulting in a final accuracy of 97% and a false positive rate of <1%. The performance and behavior of the model are summarized, and its suitability for persistent monitoring applications is discussed.
Engine inlet geometry for supersonic aircraft is quite different than for subsonic aircraft. The present study considers whether inlet shape has a significant impact on the radiated sound and flyover noise. Axisymmetric two-dimensional simulations were performed for both subsonic and supersonic inlet geometries with the same acoustic input. The effect in the far field is complicated but overall impact on flyover noise from the effective perceived noise level (EPNL) metric was found to be only about 0.5 dB.
Overview of Urban Air Mobility Noise Working Group (UNWG) activities of Subgroup 2, responsible for developing Urban Air Mobility (UAM) vehicle ground and flight testing recommendations for those tasked with evaluating the acoustic characteristics of UAM vehicles under development. This topic is being briefed to an audience at the Advanced Air Mobility (AAM) Ecosystems Working Group Meeting (AEWG).