SPACECRAFT ION PROPULSION DEVELOPMENT IN THE UNITED-KINGDOM

The on-board propulsion system dominates the design of many spacecraft , particularly as regards mass and volume. However, the mass of this s ystem, sometimes 50 per cent or more of the total, can be reduced dram atically by using ion propulsion technology, rather than the more usua l chemical thrusters. In an ion thruster, the propellant is ionized in an electrical discharge, then the positive ions are extracted from th e resulting plasma and accelerated to a very high velocity by an elect ric field, forming an extremely energetic exhaust. This paper describe s the development and status of the two UK ion propulsion systems, whi ch have thrust levels in the 1-30 mN and 50-300 mN ranges.