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Contact: Karina De Castris
European Space Agency

Speeding through space with a wisp of gas

DS4G thruster firing during tests in the ESTEC Electric Propulsion facility (CORONA vacuum chamber) Credits: ESA
Click here for a high resolution photograph.

For almost half a century, spacecraft crossed the Solar System by burning chemical fuel in rocket engines. Then, in 2004, ESA's Smart-1 spacecraft reached the Moon using a revolutionary ion engine. Now ESA and the Australian National University have successfully tested an advanced ion engine that is many times more powerful and fuel efficient.

Ion engines are a form of electric propulsion. Instead of burning large amounts of oxygen and chemical fuel, they use a small amount of gas, such as xenon, and electricity produced by solar panels. The electric current is used to accelerate a beam of positively charged gas particles (ions) away from the spacecraft. The faster the beam leaves the ion engine, the faster the spacecraft accelerates.

A test model of the new Dual-Stage 4-Grid (DS4G) thruster has already produced an ion exhaust plume that reached 210 km/s, over four times faster than previous ion engines. Since it is also four times more fuel efficient, it should be possible to design an engine which is many times more compact than present versions. Although the ion exhaust provides such a small thrust that spacecraft take months to reach high speeds, they can eventually overtake any of the heavier spacecraft fitted with traditional engines.

"Using a similar amount of propellant as SMART-1, with the right power supply, a future spacecraft using our new engine design wouldn't just reach the Moon, it would be able to leave the Solar System entirely," said Dr. Roger Walker of ESA's Advanced Concepts Team.