Assessing the vulnerability to debris impacts of electrodynamic tethers during typical de-orbiting missions

De-orbiting devices based on the use of conducting tethers have been recently proposed as innovative solutions to mitigate the growth of orbital debris. Electrodynamic tether drag might actually provide a cost-effective method to rapidly and safely remove spent upper stages and defunct satellites from low Earth orbits. However, because of their small diameter, tethers of normal design may have a high probability of being severed by impacts with relatively small meteoroids and orbital debris. In order to assess the vulnerability of electrodynamic tether systems during typical de-orbiting missions, specific work has been carried out at ISTI/CNR (Pisa, Italy) and Kyushu University (Fukuoka, Japan) over the last few years, and suitable models and methods have been specifically developed for the analysis of single and double line tethers in circular orbit and aligned along the gravity gradient. The purpose of this paper is to present the two different approaches, which have been applied to realistic de-orbiting missions of spacecraft with inclinations up to about 75 deg and initial altitudes up to 1400 km.