Abstract
Mission-critical components of unmanned spacecraft, such as electronic equipment, are often mounted on the interior surfaces of structure panels. This study investigated debris impact damage to structure panels to assess the degree to which they can protect components. If debris perforates a structure panel but is stopped by the equipment chassis, the impact will not affect the probability of mission success. The ballistic limit of the chassis therefore equals to the damage limit of the structure panel. To estimate this damage limit, hypervelocity impact experiments were conducted on sets of a honeycomb sandwich panel, simulating a structure panel, fixed directly to an aluminum alloy plate, simulating an equipment chassis, with no gap between the two. Debris environment models show that alumina debris particles smaller than 1 mm in diameter are dominant in low earth orbit, and the average impact velocity is over 10 km/sec. However, advanced techniques are required to accelerate small solid projectiles to such speeds, so steel projectiles at 6 km/sec were used to simulate the impact pressure caused by alumina impacting at 9 km/sec. The depths of the resulting impact craters on the chassis plates were measured with an optical microscope, and the damage limit equation of the structure panels was derived from the crater depths. The calculated damage limit equation was compared with the SRL ballistic limit equations. As a result, it was found that the equation obtained in this study showed safety results but was too robust. The stand-off distance between honeycomb sandwich panel and aluminum alloy plate was effective to decrease depths of craters in the plate.
