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The James Webb Space Telescope
at launch will be seeing forces

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as high as 20g's.

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That's 20 times greater
than the force of gravity

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that you and I feel just
walking around here on Earth.

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Making sure the various
parts of the observatory,

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like this primary mirror
segment behind me,

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will survive the
stresses of launch,

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is a big part of the testing
going on here at Ball Aerospace

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in Boulder, Colorado.

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So, Paul, these vibration
tests-- how long

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do you actually
vibrate these mirrors?

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Oh, it's really only for
a few seconds at a time

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when we vibrate it.

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But we're mimicking
the same loads

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that it will see while
it's in the rocket,

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while it's launching.

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Because the launch doesn't
take a long time, right?

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No, most of the vibration
occurs early in the launch

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and then very soon
will dissipate.

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2, 1, 0.

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We're about to hit full-level
sine sweep on this mirror.

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What do you mean sine sweep?

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What it does-- it starts
at very low frequency,

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where you'll see the greatest
displacement of the mirror.

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It'll move the most
at the beginning.

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And then it'll get to
higher frequencies.

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And as it gets a
higher frequency,

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the mirror is moving
faster and not

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moving as far at that point.

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So you can actually
see the mirror speed up

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as it goes through the sweep.

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So is that kind of like what
it will see during launch?

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Yeah, it will cover all the same
range, the spectrum of forces,

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just like on launch.

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So how do you know
that the mirror passed?

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We have 40
accelerometers mounted

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at different locations,
different components

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on this mirror assembly.

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So each of those
accelerometers is

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measuring essentially
the forces that

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are being applied at every
little component of the mirror.

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And we're continuously
getting feedback

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from those wallets going
through the vibration.

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By looking at all the
different components,

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if one component
where to fracture

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or experienced
strain or something,

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we'd be able to see a
difference in the behavior

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of that component before
and after the test.

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I notice it's in
a plastic casing,

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kind of like it's in its
own clean room essentially.

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And we're already
inside a clean tent.

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Yeah.

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This plastic casing is really
there for safety for us,

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just because the mirror
itself is made of beryllium.

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If there were to be a fracture
or damage to the mirror,

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that beryllium
dust can be toxic.

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And so it's contained
in such a way

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that if there were any
kind of problem, at least

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we would be safe.

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But to date, we haven't
had any such problem

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with these mirrors.

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Well, thanks so
much for giving us

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a closer look at the vibration
testing that's going on here.

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Oh, you're very welcome.

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This vibration test is just
one of the many ways engineers

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are making sure the James
Webb Space Telescope is

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ready to go when it reaches its
destination, one million miles

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from Earth.

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Thanks for joining us for this
edition of Behind the Webb.

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