Proposed RETRIEVE Microsatellite Tether Deorbit Experiment

摘要

We have designed and built prototype hardware for very small electrodynamic tether device for deorbiting a microsatellite at the end of its mission. This experiment is intended to fly as a secondary payload on a microsatellite mission. It is designed to present no risk to the spacecraft's primary payloads, remaining completely dormant until the spacecraft has completed its mission. At the end of the spacecraft's mission, the tether device will deploy a 2 km long interconnected-multiline conducting tether upwards from the micro satellite, and will use passive electrodynamic drag to lower the orbit of the microsatellite. To minimize the mass of the device, we developed a new tether deployment mechanism in which the tether deployer ejects itself away from the spacecraft and becomes the tether endmass ballast. Laboratory testing of this deployment mechanism indicates that it can successfully deploy a multiline tether at tensions low enough for successful deployment. We evaluated several plasma contactor technologies for this experiment, and selected a thermionic device based upon a COTS dispenser cathode for its minimal mass and technology maturity. With this tether hardware, a 'barebones' experiment to deorbit a 100 kg microsatellite can be implemented with a total mass of less than 25 kg., which is less than the propellant required to fully deorbit such a microspacecraft using thrusters. A more capable experiment, with active control of tether dynamics and diagnostics on tether performance and dynamics can be implemented with a total mass of 3.5 kg.