Estimation of ejecta generation and mitigation measures for large-scale structures on geostationary orbit

Abstract

Large-scale structures have a non-negligible collision probability with micrometeoroid and orbital debris (MMOD) due to their massive size, even in geostationary orbit (GEO) with low debris flux. When MMOD impact the spacecraft surfaces at high velocity, secondary debris called ejecta are generated, and they may remain semi-permanently and accumulate because there is no atmospheric drag at high altitudes such as GEO. To evaluate the amount of ejecta generation, hypervelocity impact tests were conducted for the material for future large-scale structures or material commonly used in conventional spacecraft, such as CFRP honeycomb panels and solar cells. The effect of impact energy on ejecta generation was evaluated by changing the impact velocity and projectile density. Impact tests were also conducted on irradiated samples to investigate the effects of environmental degradation due to long-term exposure to orbit. The results showed that the amount of ejecta increased with impact energy and may have been affected by radiation-induced degradation. Next, hypervelocity impact tests were conducted to investigate the measures to reduce ejecta, and it was shown that the ejecta generation could be reduced by using low-density materials such as polyimide foam and silica aerogel.