14 / 2018-04-15 10:41:43

Study on Propagation of Plasma Induced by Hypervelocity Impact on Aluminum Plates

impact plasma,hypervelocity impact,space debris

There are more than 500,000 pieces of debris in orbits of the Earth which no longer serves a useful function. They are called “space debris”. They travel at speeds up to 7-8 km/s (i.e. hypervelocity). Hypervelocity impact generates not only mechanical phenomena such as generations of a crater and secondary debris but also electrical ones such as radiofrequency emission, plasma generation, flash emission, and variation in electrical potential of the impacted target. Plasma from hypervelocity impact may result in an electrical failure of spacecraft, but the phenomenon of the plasma has not been investigated well. To simulate the debris impact against the spacecraft, we carried out the hypervelocity impact experiments using the two-stage light gas gun of the Institute of Space and Astronautical Science and focused on plasma generation. We selected a pure aluminum and various aluminum alloys plates as targets and a 7mm-diameter nylon sphere as a projectile. The projectile was accelerated at a velocity of approximately 7 km/s and impacted to the target at an angle of 90 degrees. The plasma was measured by an array of plasma probes distributed near the impact point. The expansion of the luminous cloud was observed by a high-speed video camera. The electron temperature to obtain the electron density was assumed to be the same temperature as the luminous cloud. The temperature of the luminous cloud was estimated using spectral photo sensors under the blackbody approximation. We estimated plasma parameters such as electron density and temperature and analyzed the propagation of plasma induced by hypervelocity impact on aluminum plates.