Takao Koura

Solar-Array Arcing Due to Plasma Created by Space-Debris Impact

A solar-array paddle has a high probability of a space-debris impact because it has a large area. The space-debris impact on the solar array causes not only mechanical damage but also electrical damage such as solar-array arcing through the local high-density plasma created by hypervelocity impact. In the worst case, Joule heating of the arcing carbonizes an insulation layer, and a permanent short-circuit path is created. This is permanent sustained arc (PSA). However, no PSA caused by space-debris impact in orbit has been reported. This paper evaluates the possibility of PSA caused by debris impact. Hypervelocity-impact tests on solar-array coupons in the condition of pseudopower generation were conducted. We ascertained that a space-debris impact can lead to PSA on the solar array.

Use of elemental materials for the creation of an in-situ space dust impacts detector

This research focuses on space dust ranging from 100?m to 1mm. Space dust is mainly due to secondary space debris, which is called ejecta. The objective was to create an inexpensive space dust impacts detector using elemental materials. The detector is a glass/epoxy laminate printed circuit board with an area of 81cm2 for a weight of 30g. The detector can estimate the number of impacts and can give an approximation of the space dust size. The detector will be mounted on Horyu II that will operate in polar orbit for one year. In this article the authors report: a) the production of ejecta, b) the ejecta experiments on solar array coupon, aluminium honeycomb and CFRP/aluminium honeycomb, c) the detectors working principle and d) the estimations of the minimum detectable size of debris and collision probability. The ejecta experiments demonstrated that the ejectas mass is 7 to 46 times higher than the projectiles mass. For space dust in the range 100?m ? 600?m in diameter, the collision probability was calculated to be 16.5 percent. The detectors capabilities to detect broken lines and to transmit the data to the on-board computer were also demonstrated. This in-situ space dust impacts detector is thus a very promising research area for its lightness, low cost and its ability to provide immediate data on space dust population.

Development and Evaluation of a TSLGG— Application of an ETC Gun System to its First Stage

A new type of launcher, ETC-TSLGG, is a two-stage light gas gun (TSLGG) using the technology of electrothermal-chemical (ETC) gun for its first stage. ETC-TSLGG is an improved version of the ETC gun which we had researched previously. It is developed to speed up the projectile velocity and control of variation of delay time from the ignition signal to the projectile launch. It will be used as a projectile launcher in a counter impact. Therefore, launch timing of the projectile is very important. Adjusting charge voltage and inductance of coils in a 10-kJ condenser bank so that variation of delay time is as small as possible, we depressed jitter of launch timing within a microsecond order in ETC-TSLGG. In this study, we investigated the delay time generation process. In order to clarify the operational state, pressure sensors were mounted in the ignition chamber and the pump tube. We measured projectile velocity, delay time, discharge voltage profile, current profile, and pressure profiles at different charge voltage and inductance. It can be said from these profiles that the delay time jitter was stabilized at high charge voltage and low inductance. Moreover, we have demonstrated that the delay time jitter of ETC-TSLGG was 1/100 smaller than that of the conventional TSLGG