Arcjet rocket
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Arcjets are a form of electric propulsion for spacecraft, whereby an electrical discharge (arc) is created in a flow of propellant (typically hydrazine or ammonia). This imparts additional energy to the propellant, so that one can extract more work out of each kilogram of propellant, at the expense of increased power consumption and (usually) higher cost. Also, the thrust levels available from typically used arcjet engines are very low compared with chemical engines.
When the energy is available, arcjets are well suited to station keeping in orbit and can replace monopropellant rockets.
In Germany, researchers at the University of Stuttgart's Institute of Space Aviation Systems have been looking into these challenges for years and have developed various hydrogen-powered arcjet engines capable of power outputs from 1 to 100 kW. The heated hydrogen reaches exit speeds of just under 10 miles per second (16 km/s). In 2009, an arcjet-propelled test satellite by the name of Baden-Württemberg 1 is scheduled to go to the moon.
In the future, (hydrogen-powered) advanced arcjet engines could replace conventional chemical jet engines[citation needed], both in spacecraft and jet airplanes. The advantages are: higher output per fuel quantity, improved maneuverability especially with spacecraft, very high reliability, and, last but not least, less air pollution. Hydrogen simply turns into water upon combustion, and under the premise that hydrogen production will no longer rely on fossil fuels as an energy source in the future, a significant step towards protecting the environment could be made.
[edit] Suggested Reading
Lichtbogenantriebe für Weltraumaufgaben (Arcjet propulsion systems for space applications), Prof. Monika Auweter-Kurtz, B.G. Teubner Stuttgart 1992 Institute of Space Systems at the University of Stuttgart
