[MUSIC PLAYING] The James Webb Space Telescope will be launched into the extreme cold of space. To deal with these harsh environments, engineers of the observatory use special materials to build it. Well, one of the instruments NIRSpec or Near Infrared Spectrograph used silicon carbide. 

What exactly is silicon carbide? Well, we're here at Astrium at Ottobrunn in Germany to find out. So Guenther, I guess this is silicon carbide. What's so special about it? 

It's two times stiff than steel-- 

Wow, OK. 

--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 or something? 

Yeah, in principle, yes. It's a lightweight design, you see? The material offers high stability. The optic stays aligned. So that is very important for this mission. I can show you this piece within NIRSpec when we are in the clean room. 

Mary, do you recognize the piece of silicon carbide I have shown you outside? 

Oh, yeah, it's that part 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 actually make silicon carbide? 

We don't manufacture it here. Boostec in France are manufacturing these pieces out of silicon carbide. 

Hi, Michael. 

Hello, Mary. 

Gunther 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 of the chemical reaction at high temperature of silica sand and carbon. 

Can I touch it? 

Yes 

It kind of looks like a meteorite. Now, is this the stuff that NIRSpec is made of, then? 

No, in fact, for NIRSpec, we have to crush this into fine powder, like this one. It's typically one micron in in grams 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 baseplate. I will show it to you now. 

This material is still very brittle. And it feels like chalk or chocolate. It can be breaked by hand, like that. It can be easily machined, because the material is soft. 

Guenther told us that this was going to be a ceramic. Is this a ceramic now? 

No, it's not yet a ceramic. It will become a ceramic after being sintered. 

And sintering means what? 

Sintering involves a treatment at high temperature, typically more than 2000 degrees Celsius. What is interesting here is that you can see that it is machined very quickly. 

This just gives them a flat surface to work with? 

You have to get a flat surface and also the good thickness. We have seen the press block. And afterwards, we have to machine it. And for to machine it, it's done with milling machines. 

And you're using these programs to program the machine? 

Yes, here we are simulating the program of the big base plate of NIRSpec. Once we put 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 do his measurements have to be? 

Precise in the range of a few micrometers. In 1 millimeter, you have 1,000 micrometers. 

Here, it's non-destructive inspection of the part. We first spray the dye penetrant on. Then we rinse it off. Then we dry it. And we inspect it in the dark room under UV light. And if we have cracks in the part, we are able to see them with this technique. 

For space application, we do not tolerate any crack. If you 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 that process we just saw with the UV light. What's he preparing to do now? 

This laser scanning annal allows us to make 3D model very quickly and to compare the real model with the theoretical one. We have here some NIRSpec samples. And you have NIRSpec mirror, flat mirror structure part of NIRSpec here, which have been sintered. And now, you can touch it. The material is not brittle. 

While silicon carbide is used to 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 Web. 

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