SIMULATING SPACE TETHER DEPLOYMENT ON EARTH FOR THE YES2 SATELLITE

摘要

The Young Engineers Satellite (YES) 2 will demonstrate the ability of a long tether to re-enter a small payload using momentum transfer. This ESA-sponsored mission is scheduled for a 2007 launch on a Soyuz-M. To prove that the tether deployer system will function correctly, and improve various parts of the design before launch, a testrig has been constructed (building on experience from the Tethered System Experiment and YES1). In space it is the gravity gradient that tensions the tether and effectively 'pulls' the tether out of its storage canister. This allows the tether to deploy passively, but since its effects are only significant over several kilometers it is impossible to directly simulate on Earth. The testrig allows the tether to be deployed with the aid of a space simulator - accounting for complex gravity, heating, and drag effects. The velocity of deployment is emulated by a spooling motor whose speed is determined by the real-time simulator, which takes rig tension measurements and evaluates the resultant deployment dynamics. The full deployment of the tether was tested, and the hardware and software successfully tracked the optimized trajectory. Inclusion of hardware in the loop caused only small deviations from pure software simulations.