OTTOBRUNN, Germany---On 12 July 2001, the European telecommunications satellite Artemis will lift off on board an Ariane 5 launcher. Orbital control of the satellite will be managed by the ion thruster RITA (Radio-frequency Ion Thruster Assembly) developed by Astrium. This was announced by Astrium at a press conference held on Thursday at the Ottobrunn site near Munich.
Artemis is a telecommunications satellite of the European Space Agency (ESA), its prime purpose being to test new technologies. Compared with conventional chemical satellite thrusters, RITA's outstanding features are a very high degree of efficiency and low propellant consumption. Satellite customers from all over the world are thus showing great interest in this technology. At present Astrium foresees annual sales volumes of DM 30 million.
"In the medium and long term, chemical thrusters will be replaced by electrical thrusters in many fields of application," says Dr. Axel Deich, Director Propulsion at Astrium's Space Infrastructure Division. "Since Astrium already covers this product area and is concentrating its resources on future technology, we are reinforcing our position as leading European provider of satellite thrusters. We are positioning ourselves in a growth market and can thus safeguard jobs at the sites concerned in Ottobrunn and Lampoldshausen."
The distinguishing properties of the ion thruster principle are above all environmental compatibility and low propellant consumption. Compared with conventional chemical thrusters, RITA is propelled by xenon, an inert gas that occurs naturally. Radio waves that are generated electrically excite the electrons in the xenon atoms so that they oscillate and leave the atoms, and in this way positively charge the gas. The remaining positively charged particles, the so-called ions, are discharged from the thruster at a speed of 40 km/s. This outlet speed is more than ten times higher than that of chemical thrusters with a resulting propellant utilisation that is ten times better. The degree of efficiency of ion thrusters is 70 per cent. In comparison, a car petrol engine just manages 30 per cent efficiency.
These characteristics make ion thrusters very interesting for satellite operators all over the world. It is particularly in the field of deep space missions, for example to Mercury, Mars or Saturn, that long-life, propellant-saving thrust systems are in great demand, because the life of a satellite depends primarily on the fuel available. Conventional chemical thrusters are therefore not optimal for long missions. Furthermore, every kilogram saved in propellant means another kilogram payload in the form of research instruments, aerials and solar generators.
"Utilisation of RITA on Artemis is an important step forward in the development of new thrusters for space flight," says Deich. "The technology is ready, now we have to convince our customers of its safety and reliability."
The Artemis thruster is built for a thrust of up to 15 mN, which corresponds to 350 Watt or 0.5 PS. And Astrium is already working on an even more powerful model. With 150 mN, the new thruster will provide ten times the power and is planned to be ready for operation by 2003.
RITA forms part of the Astrium-developed Ion Propulsion Package (IPP), on which two EITA (Electron-bombardment Ion Thruster Assembly) units are to be deployed in addition to the two RITA ion thrusters. In the EITA system, which has been developed by Astrium Limited in Great Britain, the ionisation of the xenon atoms is effected by thermal discharge as opposed to the radio waves used in the RITA system.
When Artemis starts its service in space, the satellite will draw its power from high-power solar generators that have also been developed and manufactured by Astrium in Ottobrunn. They are designed for a service life of at least twelve years. The attitude control unit of Artemis, the central control element of the complete satellite system, is also from Astrium.
Astrium is a joint venture of the European Aeronautic Defence and Space Company (EADS) and BAE Systems.
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Astrium High-Tech Ion Thruster Assembly Controls European Telecommunications Satellite
