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A better booster

发布时间:2019-03-08 10:03:11来源:未知点击:

By Charles Seife in Washington DC WHILE NASA wrestles with last week’s unexplained failure of the xenon ion drive in its Deep Space 1 probe, it has emerged that a potentially superior ion engine is already in orbit. It is to be found on another American spacecraft—and is based on vintage Russian technology. Last month, the US National Reconnaissance Office quietly launched an experimental satellite that uses Hall thrusters. In principle, Hall thrusters are similar to ion thrusters: both shoot xenon ions out of an engine nozzle to provide push. But Hall thrusters use the Hall effect to generate magnetic fields that accelerate the xenon gas, while ion thrusters use electric fields. “We couldn’t get Hall thrusters to work very well, so we worked on ion thrusters,” says Rob Jankovsky, an electric propulsion expert with NASA’s Lewis Research Center in Ohio. “The Russians couldn’t get ion propulsion to work, so they worked on Hall thrusters.” The NRO’s Space Technology Experiment satellite uses Hall thrusters that were developed by Russia’s Central Scientific Research Institute for Machine Building and was refined at NASA Lewis. Ion thrusters are slightly more efficient than Hall thrusters, but Hall thrusters can provide a stronger impulse. So—at least until last week’s engine failure—ion thrusters were thought preferable for deep-space missions where spacecraft do not have to be moved quickly,