An infrasound source analysis of the OSIRIS-REx sample return capsule hypersonic re-entry

TL;DR

This study analyzes infrasound signals from the OSIRIS-REx capsule's hypersonic re-entry to evaluate sonic boom models, favoring a drag-dominated source model that matches observed data well.

Contribution

It compares multiple sonic boom source models and demonstrates the effectiveness of a drag-dominated model using infrasound data from a real re-entry event.

Findings

Drag-dominated model provides the best fit to recorded infrasound signals.

Carlson's simplified method may be accurate but less preferred.

Infrasound analysis improves understanding of high-altitude infrasonic sources.

Abstract

The OSIRIS-REx sample return capsule hypersonic re-entry into the atmosphere is a rare opportunity to test a variety of sonic boom source models since the projectile dimensions are well characterized. While the as-flown flight path is unknown, the predicted flight path enables a rough approximation of the source Mach number and location. Six infrasound microphones deployed in the boom carpet along the predicted flight path recorded impulsive signals from the OSIRIS-REx re-entry. Using a suite of atmosphere profiles and the geometric acoustics approximation, we estimate locations with uncertainty estimates along the flight path from which the signals were emitted. Acoustic overpressure and signal duration predictions from Whitham's far field theory, Carlson's simplified sonic boom prediction method, and a drag-dominated hypersonic model are analyzed with uncertainty estimates from the location estimate. While the Carlson simplified sonic boom prediction method could be accurate, our preference is for the drag-dominated source model. Using this source model with an inviscid Burgers' equation solver for propagation, we obtained an excellent match to the recorded data. These results will help better inform future sample return capsule re-entry observation campaigns as well as contribute to a better understanding of high altitude infrasonic sources.