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An ion is created when an atom gains or loses electrons. In ion propulsion an
electron gun is used to knock electrons into a sea of xenon atoms, turning them
into ions. Three charged plates accelerate the ions and send them out of the
back of the rocket engine at speeds about 77,000 mph. To avoid accumulating a
negative charge, the probe shoots electrons back into the stream of xenon ions
as they’re leaving the engine. Ion propulsion only needs a tenth of the fuel of
a chemical rocket to reach the same destination, and that means a smaller rocket
is needed to launch missions, successfully. This will allow probes, such as the
NASA Dawn, to orbit two separate objects, in Dawn’s case the asteroid Vesta in
2011 and the dwarf planet Ceres.
Some disadvantages to the ion engines, although it only requires a tenth of the
fuel needed by a chemical thruster, it also lacks power. Marc Rayman, chief
engineer on the Dawn mission, has labeled ion propulsion “acceleration with
patience.”
Deep Space 1
In 1998, Deep Space 1 became the first spacecraft to use ion propulsion to reach
a destination in the solar system. Using more than 160 lbs. of xenon, the probe
showed a dozen new technologies and flew by two asteroids. Deep Space 1 went on
operating its ion engine for 678 days, the longest any propulsion system had
been continuously run, the Dawn mission is expected to surpass this record.
Hayabusa
A Japanese space probe built to investigate an asteroid and use new technology
to bring back samples of an asteroid’s surface to earth. Japan has realized a
mission that uses a small spacecraft for a discovery of a very approachable
asteroid and the development of a highly efficient electric propulsion system
for the spacecraft is a brilliant advancement.
In November 2005, Hayabusa suffered a serious fuel leak right after its second
successful touching down on the surface of Itokawa, an asteroid near Earth.
Since the extra engines were not available, the strong disturbance occurred on
December 8th and caused the communication to be lost since then.
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