Experimental Study on Lodging a Metal Anchor into Free-falling Targets for Space Debris Mitigation

Abstract

An experimental system for lodging a metal anchor into free-falling targets has been developed and the lodging behavior has been investigated. Lodging a metal anchor into space debris to capture it is a good candidate for gathering the debris in space debris mitigation systems. Being one of the simplest methods, it can be applied to most any system, such as the electrodynamic tether system or a propulsion system. Basically, a tethered anchor is fired into space debris to capture it. In our experimental setup, a test plate representing the target space debris is initially attached to a rigid frame using two electromagnetic mounts. A specially designed projectile anchor is fired into the target, in precise coordination with the release of the target test plate into a free-fall condition (i.e., controlled by optical sensors mounted on the acceleration tube and electromagnetic mount). As a result, the metal anchor impacts the target while free-falling through space. The experimental results show that an adequate anchor accuracy can be achieved with the appropriate projectile velocity for a non-fixed (free-falling) target. Moreover, we show that the penetration velocity differs predictably between fixed and non-fixed targets, as well as that predictability changes based on the distance of the projectile's impact point from the target's center-of-mass (CM). The equations derived for predicting penetration velocities for free-falling targets were validated through physical testing and the required penetration velocities were accurately predicted.