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Hi my name is Elizabeth Thiel.
I'm from Komachin Middle School in Washington state
and you're watching NASA Now.
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Hi, I'm Matt and this is NASA Now.
At NASA, every part of the manufacturing
and assembly process of a spacecraft is critical
to ensuring mission success.
Today, we'll meet an expert
who explains the science behind welding and why a weld
that works on Earth doesn't mean it will hold up in space.
That's ahead, first here's what's happening at NASA Now.
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Did water ever exist on Mars?
Recent images taken from NASA's Mars Reconnaissance Orbiter
reveal that it could have.
This image of the McLaughlin Crater, stretching 57 miles wide
by 1.4 miles deep, shows layered,
flat rocks containing carbonate and clay minerals
that usually form in the presence of water.
Scientists also observed small channels close to the bottom
of the crater that could have marked the surface of a lake.
This observation, combined with the lack
of any large inflow channels,
suggest this may have once been the site
of a groundwater-fed lake.
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Building a spacecraft that can withstand the rigors
of space takes a lot of testing and design.
When the design is ready and it's time to build a prototype,
that's where welding engineer Shane Brooke and hundreds
of other people have a big role.
Shane took some time to give us a firsthand look
at the important role welding plays
as human beings push further and further into space.
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Welding is used on everything.
We use it on engines.
We use it on cryogenic tanks.
It's used with the space frame of the shuttle.
It's used in electronics, so there's a wide array
of welding processes that a lot of people don't give credit to,
but that are, indeed, welding processes.
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Generally speaking, there are two types of welding.
There's fusion welding and solid-state welding.
Some of the fusion processes, we're more familiar with,
you know, that's the stick electrode
or the gas metal arc welding, mostly what you find in shops
and garages across America.
The solid-state welding is a bit different
in that it doesn't use melting.
For example if we have this complicated aluminum alloy,
it's difficult to fusion weld some
of these materials that we create.
But we can use the friction stir process
because it doesn't melt the material
to join the two parts together.
There is no external heat source.
It's friction alone to heat the material
to reach this plastic state, much like if you were
to just rub your hands together really hard
and really fast, you generate heat.
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There are two types of friction stir welding.
We classify them as conventional and self-reacting.
They both use similar heating processes.
Conventional has a one-sided pin tool
where we plunge into the part.
We plasticize it, form it into like a taffy or a putty.
We have an anvil behind the part.
So as we plunge into the part, the anvil reacts that load
so the part doesn't move, and then it's forged together.
The self-reacting process does not have an anvil.
So we basically have a shoulder on both sides pushing,
canceling out the loads, traversing through the joint.
So as both shoulders rotate,
the pin will traverse through the joint.
The material is plasticized and forged together
with a pinching load and we have a perfectly welded part.
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Currently, we're using friction stir welding
for large space vehicle cryogenic tank production.
These large vehicle tank structures are aluminum,
and aluminum, as we know, is a softer metal than steel.
So for the larger space applications, it works great
for cryogenic tank production.
Looking towards the future at different high-strength steels,
we're currently working on friction stir technology
that will allow us to weld these higher strength steels.
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Not necessarily, different materials have different
properties at different temperatures.
So here on earth at 70 degrees a weld may be great but if you get
into space at -300 degrees where it's very, very cold now
that weld may be very brittle.
So we don't want it to fail when the astronauts need it most.
We do all sorts of testing, as you could imagine.
There is testing called, nondestructive evaluation,
where we use ultrasonic technology, x-ray technology,
dye penetrate inspection, where we inspect these welds to see
if there are any surface defects or volumetric defects.
We also do mechanical testing
where we will weld up a test panel.
We'll cut it into strips,
and we will mechanically pull the weld until it fails.
And then based on that strength or that number,
we know how strong that weld is.
And then we can use those numbers
to factor how safe is it to fly this vehicle.
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Did you know that a material used
to make jet engine fan cases is also being used
in sports and healthcare?
Together, NASA and private industry have developed a carbon
fiber, reinforced composite.
This braided, lightweight material is being used
to create jet engine fan cases that are stronger
and lighter-making them safer and more fuel-efficient.
This same technology is being used to create more durable,
lightweight sports equipment and prosthetic devices.
Now you know.
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You've just learned how welding is critical
to holding together a spacecraft during the launch process
and in the harsh environment of space.
Now it's time to test your own engineering ability.
Here's a great project where you
and your students can build a spacecraft structure strong
enough to withstand three successful launches.
Look for Engineering Design Challenge:
Spacecraft Structures.
You'll find it by checking out the extension activity
for this program on the NASA Explorer Schools Virtual Campus.
Well that's it for NASA NOW.
Be sure to visit our facebook page and leave a comment.
We'll see you next time on NASA NOW!
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NASA NOW comes to you from the Virtual Campus
at NASA Explorer schools.