Infrasound and Seismic Analysis of the SpaceX Falcon9 Explosion Sequence of 1-September-2016

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During a static launch test on 1-Sep-2016 at Kennedy Space Center, a SpaceX Falcon 9 rocket exploded causing loss of the rocket and the payload, and extensively damaging the launch complex. The sequence was captured by a 3-element infrasound array and a broadband 3-component seismometer at the Astronaut Beach House, just 0.87 miles (1.4 km) from the launch pad.

Manual picking identified 153 impulsive airwave signals over a 26-minute interval and these were compared to video recordings of the sequence. The explosion onset consisted of a moderate signal on both seismic and infrasound (52 Pa) instruments. This corresponds to the rupture of the second-stage fuel tank. We found no signals before this, so we do not believe that there was an external cause. The primary fuel tank ruptured 4 seconds later and was the strongest event by far, producing an infrasound signal that exceeded 1400 Pa (~2000 Pa in reduced pressure). The seismic signal consists mainly of air-coupled Rayleigh waves with frequencies of 5-23 Hz.

The infrasound events occurred in four clusters. The first cluster included the onset and main events and 46 smaller events. This was followed by several minutes without infrasound signals during which a 3.5 minute continuous seismic vibration occurred. Cluster 2 consisted of 4 events ranging from 117-256 Pa. Cluster 3 comprised 96 events of 7-78 Pa. Cluster 4 consisted of 5 events with overpressures of 23-63 Pa. Gaps of several minutes without infrasound and seismic signals occurred between clusters 2 and 3, and 3 and 4. In terms of energy, the main event dominated; in terms of numbers, cluster 3 had the most infrasound events.

The seismic and infrasound data are complementary to video recordings of the explosion, and provide additional characterization that may be useful to interpret the sequence of events. Because of the proximity of our array to this rocket explosion, our dataset may be unique.

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Presented at the AGU Fall Meeting on December 14, 2017 in New Orleans, LA