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[ ♪ ]

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Mike Meacham: We've all played
these claw games before

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where it can be really
frustrating using a grapple

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to pull a toy out of a machine.

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Well, the success of
NASA's InSight mission

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depends upon a grapple.

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Let's learn about it on this
episode of Crazy Engineering!

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[ ♪ ]

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Crazy Engineering:
Space Claw

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All right. We are here at
the InSight lander

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surface test bed.

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This is Nick. He was one
of the key engineers

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on the grapple mechanism.

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Nick, thanks for joining us.

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Sure.

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You've got this grapple. What
does it do? What's its purpose?

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NIcholas Haddad: So, its purpose
is to grab the instruments

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so the robotic arm
can then lift them

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and the place them
down onto the surface.

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Mike: When I play these arcade
games, right? They're really

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hard to get that toy
out of the game.

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And you're using a mechanism
that kinda reminds me of that.

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Is that a good idea?

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Nick: So, the mechanisms
themselves,

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although they look
similar, are very different.

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With the arcade game, when you
grab that stuffed animal

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and you pull on that
stuffed animal,

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you actually open
the claw fingers

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and that stuffed
animal falls out.

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With the InSight grapple

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that mechanism is
designed to latch.

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So once those fingers are closed

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it's impossible to pull on
those fingers to open it.

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Mike: So, how does it work?

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Nick: So, the grapple
has 5 fingers.

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And we've designed this grapple
to maximize our success.

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It uses a wax actuator to open
the fingers.

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We grab onto little hooks at
the top of each instrument.

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And then the robotic arm
picks those instruments up

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and places them down
on the surface.

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Mike: You said "wax"--

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that we're using wax to open
and close the grapple?

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Nick: Yeah.

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Mike: Why do we use wax?
Why don't we use

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a more typical solenoid
or an electric motor?

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Nick: It's actually a thoroughly
proven technology.

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It's used in space applications
like the InSight grapple.

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But it's also used for
decades in things like

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our car thermostats and
our appliances at home.

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It uses a heater to melt some
wax inside of a little housing.

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And when this wax melts,
it expands.

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And it develops this
hydraulic pressure.

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And that pressure
pushes out a rod

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which we use to actuate
our mechanism.

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Mike: Once it's completed
its primary function of

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putting instruments down,
what does it do after that?

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How does it get out of the way
for other things you want to do?

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Nick: So, there's actually
another hook

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on the side of the robotic arm.

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And the robotic arm can maneuver
itself so the grapple can

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restow itself on the
side of the arm.

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Then the arm is free
to essentially do

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whatever it needs to do.

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Mike: Nick, this grapple
mechanism is truly unique.

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It's really fun to learn about.
Thank you so much

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for bringing us into
the test bed and

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answering all these questions.

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And, as always, thank you out
there for paying attention

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and check back here for some
more Crazy Engineering!

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[ ♪ ]

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Woo hoo hoo!

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[ ♪ ]

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Crazy Engineering

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NASA Jet Propulsion Laboratory