The James Webb Space Telescope will be launched into the extreme cold of space
To deal with these harsh environments, engineers of the observatory used special
materials to build it. Well, one of the instruments, NIRSPEC, or Near Infrared Spectrograph,
used silicon carbide. What exactly is silicon carbide?
We're here at Astrium, in Ottobrunn, Germany to find out. So, Guenther, I guess this is silicon carbide.
What's so special about it? Guenther Kling/Astrium: It's two times stiff than steel and five times stiff than
aluminum. Silicon carbide is a ceramic material and it offers outstanding
properties to fulfill the mission of NIRSPEC. So ceramic... like porcelain?
Yeah, in principal, yes. It's a lightweight design, you see. The material offers high stability.
The optics stays aligned and that is very important for this mission.
I can show you this piece within NIRSPEC when we are in the cleanroom.
Mary, do you recognize the piece of silicon carbide I have shown outside? Oh yeah, that bar right there.
It is part of an optical element on NIRSPEC. What parts are silicon carbide?
every gray-colored item you see here is made out of silicon carbide.
It's representing 75% of the structure you see.
Do you guys does actually make silicon carbide?
We don't manufacture it here. Boostec in France are manufacturing these pieces out of silicon carbide.
Hi Michael. Michel Bougoin/Space Projects Manager - Boostec: Hello, Mary.
Guenther from Astrium told us that you guys make the
parts for NIRSPEC out of silicon carbide. What exactly is silicon carbide?
Silicon carbide is a synthetic material made from the chemical reaction
at high temperature of silica sand and carbon.
Can I touch it? Yes.
Kinda looks like a meteorite.. Now, is this is stuff that NIRSPEC is made of then?
No. In fact for NIRSPEC, we have to crush this into fine powder
like this one. Typically one micron in grain size.
So, is this the stuff then that goes into making NIRSPEC?
Not yet. There is a further step where we press this powder into blocks
We have just got the blank for NIRSPEC base plate. I will show it to you now.
This material is still very brittle and it feels like chalk or chocolate.
It can be break by hand like that. It can be easily machined because the material is soft.
Guenther told us that this is going to be a ceramic. Is it a ceramic now?
No it is not yet a ceramic. It will become a ceramic after being sintered.
And sintered means what?
Sintering involves a treatment at high temperature, typically more than 2,000 degrees Celsius.
What is interesting here is that you can see that it is machined very quickly.
This just gives him a flat surface to work with?
He has to get a flat surface and also the good thickness.
We have seen the pressed block and afterwards, we have to machine it…. And to machine it, it’s done with milling machines.
And you’re using these programs to program the machine?
Yes, we are simulating the program of the big base plate of NIRSPEC.
Once we put the part in the milling machine, we start green machining.
It is here that we shape the part. This will take roughly two weeks.
Where do we go after this?
The part will be sintered in order to transform the compact of powder into the ceramic.
What's he doing now?
He’s preparing the measurement of this part with this coordinate measuring machine.
He will measure the flatness of this area here.
How precise to his measurements have to be?
Precise in the range of a few micrometers.
In one millimeter, you have one thousand micrometers.
Here is non-destructive inspection of the parts.
We first spray the dye penetrant,
then we rinse it off, then we dry it
and we inspect it in the darkroom under UV light
and if we have cracks in the part,
we are able to see them with this technique.
For space applications, we do not tolerate any crack.
If we have a small one, we will remove it by grinding. We are able to do that.
The UV allows us seeing the cracks and the big holes.
here, we are looking for very small holes.
And this is on top of the process we just saw with the UV light.
What’s he preparing to do now?
This laser scanning head allows us to make 3D model very quickly
and to compare the real model with the theoretical one.
You have here some NIRSPEC samples.
You have NIRSPEC mirror, flat mirror, structure part of NIRSPEC, which have been sintered.
And now you can touch it, the material is not brittle.
While silicon carbide is used the build space telescopes like Webb
its unique properties are valuable for things right here on Earth
like the water pump in your car.
Thanks for joining us for this edition of Behind the Webb.