Space debris is a growing problem and threat to future space missions. The number of objects in an earth's orbit increases exponentially as the costs of getting an object there continue to sink. This makes it easier for companies and research institutions to get small satellites or experimental satellites into orbit. Deorbiting of these objects after a failure or end of life is fundamental to ensure the safety of existing and future space missions. The H2020 E.T.PACK project is developing a deorbit kit based on an electrodynamic low work function tether (LWT) coated with Ca24Al28O644+(4e-) electride material (C12A7:e-). Due to an electrodynamic effect, one end of the LWT captures electrons from the ambient plasma while the opposite end emits electrons due to the thermionic and photoelectric effects. While moving through the Earth's magnetic field, the electric current through the tether generates a Lorentz force that drags the spacecraft towards earth. Before the demonstration mission of the deorbit kit, the functionality and space durability of the tether must be ensured. In order to determine the properties and suitability for space operation of the LWT, a test campaign for a number of samples was developed. The samples had to undergo various tests and measurements executed by Technische Universität Dresden (TUD), Fraunhofer IKTS and German Aerospace Center (DLR) to examine the electrical and optical properties, as well as degradation behavior due to the space environment. The measurements to determine the material properties are: thermionic emission measurement, photocurrent density measurement and emissivity measurement. To examine space durability, the material underwent an atomic oxygen exposure test, an UV radiation exposure test and a thermal cycling test. The influence of these tests on the material properties was examined afterwards. This publication will provide an overview of the test plan and test procedures. The results of the individual tests and measurements are presented and discussed.
Stark et al. (Fri,) studied this question.