Analysis and design of a friction brake for momentum exchange propulsion tethers

The purpose of this paper is to present an engineering assessment of a proposal for a deployment brake for a momentum exchange tether. Tethers have attracted considerable interest amongst the propulsion community for many years for orbit raising, energy conversion, de-orbiting, and injection into interplanetary transfers, and the motivation for the work described in the paper is directly mission-oriented. The YES2 SpaceMail mission has been planned as a low-cost international effort to provide a facility for the return of small samples from the ISS back to Earth, based on an inflatable re-entry capsule and a mechanical tether system. The system will be lofted into orbit as part of a payload on a Foton/Bion rocket launcher. The brake design concept is based on the use of friction between the deploying tether and a short pole onto which several turns are wound, and the paper summarises the modelling work that has been done, and then discusses an experiment in which the premise was tested in the laboratory. The paper concludes with certain practical proposals for implementation.