Seeking radio emissions from hypervelocity micrometeoroid impacts: Early experimental results from the ground

High-velocity impact experiments have been conducted to look for radio frequency (RF) emissions from impact-produced plasmas that could be used to identify micrometeoroid impacts to spacecraft in orbit. Launched by a three-stage light gas gun, 17 mm diameter by 0.9 mm thick Ti6Al-4V flyer plates impacted 0.75 mm thick indium (In) foil at more than 10 km s−1. The resulting collision presumably ionized some fraction of the vaporized In cloud, which was accelerated to about 12 km s−1. This weak In plasma then passed through a wide-band detection system that looked for RF emissions. Over the course of five shots during the experiment, no conclusive plasma emissions from the In were detected. However, strong evidence indicates that significant charge is accumulated on the flyer plate during acceleration and flight, possibly producing Paschen discharge to the chamber walls. Finally, plasma may be produced by the launcher secondary to launching the plate, leading to further contamination of the results. These effects have significant consequences for RF experiments attempted in launching systems of this type.