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(Music)

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Hey guys, this is Mike Meacham at the Jet
Propulsion Laboratory and this is an episode

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of Crazy Engineering.

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(Music)

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Here at JPL, we have to solve problems that
nobody’s ever solved before and sometimes

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the solutions can seem a little crazy.

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Today we’re going to talk about this bad
boy, an ion thruster. What’s so special

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about an ion thruster? What makes it different
and how does it help us get through the solar

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system? Let’s go talk to an expert.

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Alright guys, we found our expert. This is
Marc Rayman.

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Hi Mike.
Marc, where are we?

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We’re at a vacuum chamber here at JPL where
we test ion engines like this one and we have

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three just like it on the Dawn spacecraft.
It’s out in the main asteroid belt between

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Mars and Jupiter.

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Can you explain what makes an ion thruster
different than other types of thrusters?

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Sure, well first, let’s remind ourselves
how a regular rocket engine works.

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You take a gas and you heat it up, or you
put it under pressure and you push it out

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of the rocket nozzle, and the action of the
gas going out of the nozzle causes a reaction

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that pushes the spacecraft in the other direction.

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With ion engines, instead of heating the gas
up or putting it under pressure, we give the

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gas xenon a little electric charge, then they’re
called ions, and we use a big voltage to accelerate

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the xenon ions thru this metal grid and we
shoot them out of the engine at up to 90,000

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miles per hour. And they’re going out so
fast that each individual ion gives a relatively

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large push back on the spacecraft.

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So, if I’m the spacecraft could you push
me as hard as I’m going to feel from one

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of these thrusters.

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I can try.

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Okay, I’m ready. I can take it.

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(Blows air)

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I barely felt that.
That’s right, the engine pushes on the spacecraft

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as hard as this single piece of paper pushes
on my hand.

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In the zero gravity, frictionless, environment
of space though, gradually the effect of this

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thrust builds up.

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At full throttle, it would take Dawn four
days to accelerate from zero to sixty miles

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per hour.

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Wow that’s a slow car, isn’t it?

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It is, but instead of thrusting for four days,
if we thrust for a week or a year or as Dawn

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already has, for almost five years, you can
build up fantastically high velocity.

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It’s what I like to call acceleration with
patience.

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Why is that a good thing? What’s the tradeoff?
What can Dawn do that other spacecraft cannot

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do?

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The ion engine gives us the maneuverability
to go into orbit and after we’ve been there

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for awhile, then to leave orbit and go on
to another destination and do the same thing.

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In 57 years of space exploration, Dawn is
the first mission targeted to orbit any two

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extraterrestrial destinations. It wouldn’t
be possible without ion propulsion.

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For two centuries, this has been just a little
smudge of light against the stars.

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Dawn got to spend 14 months at Vesta and turned
it into a whole new complex, fascinating,

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alien world.

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Marc, where are we right now? This is the
Dawn mission control room at JPL. This is

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where we control the spacecraft from; we tell
the spacecraft where to point the thruster,

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what throttle level to use and that’s how
we guide the spacecraft through the solar

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system.

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And we’re on to the next location, which
is Ceres.

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That’s right, the dwarf planet, in fact
the first one ever discovered we’re going

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to get into orbit very soon and the pictures
are going to be coming into this very room.

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Very cool! Stay tuned for those photos and
stay tuned for some more Crazy Engineering.