BETS

Concern about the growth of space debris, aggravated by the increase in the number of countries with direct access to space, made the SPA. 2010. 2. 3-02 Call Topic suggest "preventing generation of new debris and de-orbiting upper stages and spacecraft after mission completion". The Project proposed involves Research and Technology Development of an efficient deorbit system, to be carried in the future by every launched spacecraft. A dedicated system is needed because satellites naturally orbit at ionospheric altitudes where air drag is very weak. The system considered involves magnetic drag on a current-carrying conductive tether, uses no propellant and no power supply, and generates power on board. It beats alternative systems (enhanced air drag, and rocket and electrical thrust) in simplicity and in the combined basic metrics: Frontal Area x Deorbit Time and System-to-Spacecraft Mass Ratio. Like air drag, magnetic drag is a dissipative mechanism arising from the orbital tether motion relative to the corotating magnetized plasma, which induces the current in the tether.

The Work Programme includes studies of plasma-tether interaction under ambient-plasma variations along orbit, performance dependence on orbital altitude/inclination, and trade-off against alternative systems; numerical simulations of current to a bare tether; and studies of orbit/tether dynamics, and of both tether survival and the tether itself as debris. Deorbiting a satellite representative in both orbit and mass in Low Earth Orbit is considered. Tasks involve i) Design and manufacturing the tether as a tape with possible materials-structure both lengthwise and in its cross section, and a study of materials; ii) deployment strategy, and design / manufacturing of subsystems: tether-deployment mechanism, end mass, electric control and driving module, electron-ejecting plasma contactor, and interface elements; and iii) microgravity, and hypervelocity-impact and tether-current laboratory tests.