An ion engine several times more powerful than any previously flown is being tested by NASA. It could propel a spacecraft all the way to Saturn鈥檚 moon Titan.
Ion engines operate by removing electrons from atoms of a gas 鈥� usually xenon 鈥� and then accelerating the resulting ions through an electric field. The ions are shot out the back of the engine to create thrust.
The engines provide much less thrust at any given time than do rockets. But they are much more fuel efficient, providing a steady source of propulsion that could ideally be used to take spacecraft to the outer solar system.
Advertisement
NASA tried out ion engines on its Deep Space 1 mission, which launched in 1998 and visited an asteroid and a comet at a distance of 203 million kilometres from the Sun. But the so-called NSTAR engines used on that mission were not powerful enough for more distant excursions.
A new engine called NASA鈥檚 Evolutionary Xenon Thruster (NEXT) can generate 2.5 times as much thrust as the NSTAR engine and would enable more ambitious missions. The engine was built by Aerojet, an aerospace company based in Sacramento, California, US.
Throttle down
Like NSTAR, NEXT uses xenon gas as its propellant and solar arrays to capture energy from sunlight. But NEXT鈥檚 ions are trapped and accelerated more efficiently, providing more thrust than previous ion engines.
It can also vary its thrust by a factor of 11, as compared with NSTAR鈥檚 factor of five. This means it can throttle down to lower levels as it travels farther from the Sun and receives less sunlight, allowing it to operate at greater distances than NSTAR.
鈥淭his is taking the technology, enhancing it, and making it a product line ion thruster that could be sent on numerous NASA missions,鈥� says Tibor Kremic, manager of the In-Space Propulsion Program at NASA鈥檚 Glenn Research Center in Cleveland, Ohio, US.
NEXT can generate a force of 236 milliNewtons, compared to NSTAR鈥檚 maximum of 92 mN. This corresponds to 6.9 kilowatts of engine power, compared to NSTAR鈥檚 2.3 kilowatts.
It is also more powerful than the 22 mN engines used on Japan鈥檚 Hayabusa spacecraft sent to asteroid Itokawa (see Smash and grab raid on an asteroid) and the 70 mN engines used on the European Space Agency鈥檚 SMART-1 probe to the Moon (see SMART-1 settles into lunar orbit).
Temperature test
鈥淣EXT offers up a pretty significant leap in capability,鈥� says Scott Benson of NASA鈥檚 Glenn Research Center in Cleveland, Ohio, US. Benson is the programme manager for NEXT.
The first NEXT engine has passed preliminary tests at NASA Glenn and has been sent to NASA鈥檚 Jet Propulsion Laboratory in Pasadena, California, US. There, engineers will test how well it holds up to extremes of temperature that it may experience in space.
Benson hopes to have engine testing finished by September 2007, enabling NASA to consider it for future missions to Saturn鈥檚 moon, Titan, or possibly Jupiter. For the Titan mission, both an orbiter and a lander could be sent to the distant moon, which lies more than 1 billion kilometres from the Sun.
It would require about 20 kilowatts of engine power to get there. 鈥淲e could do that with an array of three thrusters, plus a spare,鈥� Benson told New 杏吧原创.
