Ion propulsion and INTELSAT VII

Electric propulsion (EP) systems offer exhaust velocities at least an order of magnitude higher than those of chemical thrusters, so can reduce propellant masses by the same factor. For communications satellites, this benefit will be particularly valuable for north-south station-keeping (NSSK). Following an active interest in EP technology for many years, INTELSAT have assessed the possible application of ion thrusters to INTELSAT VII for NSSK, aided by proposals from the four possible prime contractors. However, these proposals were not deemed acceptable; the reasons for this are discussed, together with the characteristics of the competing EP technologies. The various factors influencing this and future decisions are considered, and INTELSAT´s programme to provide the additional information needed to evaluate the application of EP to later phases is described