Counteracting contingencies in fast rendezvous with ISS

Abstract

The existing rendezvous profiles of Russian crew vehicles in some flight phases are not adapted to contingencies which can be caused by an autonomous rendezvous system failure. If it occurs, the crew can complete the rendezvous in manual mode only at a range of less than a kilometer. However, at a long range the manual rendezvous mode is complicated because the on-board algorithm of the motion control system generates free trajectories that do not provide the crew with a convenient manual control. As a rule, in this case re-rendezvous is required with shifting the docking to the next day. In the case of fast rendezvous profiles (which allow to get to the ISS in 3 h) re-docking should be scheduled only in two days because of the crew adaptation to the weightlessness. In order to allow the crew to complete the rendezvous in manual mode without delaying the docking, it is required to create a more simple procedure for calculating and performing transfer burns. From the Gemini, Apollo and ATV spaceflight heritage, the technique for approaching the target from a coelliptical orbit has been known, that provides a uniform motion and convenient control of the crew vehicle in manual mode. The paper proposes the fast rendezvous profile with the insertion of the crew vehicle into an intermediate orbit coelliptical with the target orbit. In this approach, in case of automatic rendezvous failure, the crew, having a complete understanding of the relative motion, is able to perform the transfer to the target in manual mode without increasing the duration of the flight till the docking. The paper presents the results of testing this approach on a simulator, which in the long term will allow to reduce the rendezvous duration of Russian vehicles to a single orbit.