Acoustic systems for detecting particle impacts in space

This paper briefly describes acoustic systems currently under development for measuring the flux of micrometeorite and orbital debris in space, and detecting damaging impacts when they occur on spacecrafts or habitats. While the particles of interest here are typically small (less than 5-mm diameter) their high speed (greater than 5 km/s) makes an impact quite energetic. At these speeds an impact typically leaves a hole or crater ten times the diameter of the particle, so particles as small as 50 μm can disable a system or create a hazard. The systems described here span a range of purposes. One system is focused on astronaut safety and uses an array of piezoelectric sensors to detect, localize, and assess damage on habitats. Another is focused on scientific data collection and uses a large impact-area diaphragm instrumented with fiber optic sensors for measuring particle size distribution. Other systems use combinations of acoustic and non-acoustic sensors to provide additional information about the nature of the impacting particles. Laboratory tests of each system are described, and the range and limitations of each are briefly discussed. [This work is being supported by the NASA Orbital Debris Office.]