The Tether Reboost System: A Cost-Effect Propulsion Solution
for the International Space Station

by

Greg Garbe
26 October 2001

The International Space Station (ISS) orbits at an inclination of 51.6 degrees and an altitude varying between 360 and 490-km depending on solar cycle conditions. This rather low altitude range was necessary in order to provide a sufficient protective atmospheric layer and provide reasonable access by NASA's shuttle and the Russian Soyuz and Progress vehicles. However, this altitude region also produces a significant drag force on the ISS averaging over 0.5-N during solar minimum. The current baseline reboost strategy is to deliver approximately 65-MT of bi-propellant via the three resupply vehicles over the 2006-2016 period.

The Tether reboost System (TRS) is a straightforward conceptual electrodynamic tether propulsion system design that would eliminate the need for any chemical reboost. The TRS has a triangle configuration with the 100-m ISS Truss forming the base and a pair of tethers meeting at the power supply satellite to form the apex. The tethers have a mechanical connection to the truss with a 115-m nonconducting tether segment before transitioning to a 15-m diameter charge collector and 2.5-km insulated conducting tether. The power supply satellite will generate the power needed to overcome the orbit induced EMF and drive the approximate 10-Amps of current through each of the two tethers to produce a reboost force of approximately 0.6-N. TRS advantages include its mechanical connection, a small shift in the ISS center of mass (~3 M), it requires only a single shuttle flight for delivery and full installation to ISS, and finally its self sufficient nature. This talk will give an overview of the design, performance, and development plan for the TRS.

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