Why Are there Holes in the James Webb Sunshield? (Explained by My Dad) – Smarter Every Day 270

Here’s a sanitized version of the transcript:

—

Hey, it’s me, Destin. Welcome back to Smarter Every Day. We are on the way to my dad’s work, and everything about this is unusual. I have been trying to interview my father at his workplace for two years now. The reason it’s so challenging is that he has a really unique job. It’s 2 a.m., so let’s go see what he does. I think you’ll understand.

I had trouble finding the building because it’s unmarked. After driving around for a while, I finally found his car. For some context, my dad worked in the auto industry when I was growing up, and he is a metrologist. As parts came off the assembly line, he would create innovative ways to measure those parts.

Right now, we are at my dad’s workplace, and you can see there’s testing in progress. I asked if my dad was there, and they pointed me to a room. That’s my dad, and that’s the bottom layer of the sunshield of the James Webb Space Telescope.

So here’s the deal: My dad did amazing things, and I got to investigate the James Webb Space Telescope in some fascinating ways. First, I spoke to Dr. James Mather, the chief scientist of the project. I had a really interesting interview with him, which you can check out if you’re interested. I also got to speak to my dad, who had been working on the sunshield for many years.

The sunshield for the James Webb Space Telescope protects the telescope’s optics from heat and light from the sun, as well as reflected heat and light from the Earth and the moon. It also shields the optics from the electronics on the bottom side of the telescope. This is critical because to capture the images they want in infrared wavelengths, they need to keep the optics at a very cold temperature. The sunshield makes that possible.

There are five layers to the sunshield, and they unfolded like origami ten days after launch, as the telescope was on its way to L2, the second Lagrangian point of the Earth-Sun system.

I want to take you back to 2016 when I got to go into the clean room with my dad while he was measuring the sunshield for the James Webb Space Telescope. I’m excited to show you what he did because I didn’t understand all of it at the time, and I got to ask questions. For me, this is more than just a YouTube video; it’s a special moment with my dad.

So let’s go back to 2016 and learn about the sunshield for the James Webb Space Telescope.

Alright, so what’s the deal? There’s the dirty side of the room and the clean side. Where you’re sitting is the dividing line.

What’s the veil for? It’s for breathing, potentially… It’s for spit and facial hair.

This is a hood? Yes, that’s a hood.

And I’m not supposed to touch the ground with it? Correct.

You’re on the magical clean side now.

It’s a lot hotter under here, isn’t it? Yes, we’ve all done this probably five times a day for a long time.

Are you serious? Five times a day for how long have you done this? It’s been a long time… more than four or five years for the program.

So this is the core measurement group, right, Dad? Yes, we have a measurement crew!

This is Bobby, and y’all have worked together for a long time? At least 25 years combined.

And this is Mark. Mark, you’re the specialist on the shield itself, right? I do a bit of everything, including measurements and processes.

My name is actually on the cleanroom access list.

Oh, yeah. That’s you right there!

It was a big moment for me to walk in and stand in the same room with this thing and my dad. It was one of those moments that will be special for the rest of my life.

So, this is what keeps the telescope shielded from sunlight, Earth light, and moonlight.

Got it. And that’s because the instrument has to be really cold, right? Yes, it does.

This is like a potato chip sack or something? Well, it’s only one-thousandth of an inch thick.

There are five different layers, right? Yes.

And this is the flattest layer. This is not the true shape of it; it’s just on a 1x load, not under tension.

How does this thing hang next to the spaceship? That’s the rim area where the sunshield attaches to the space telescope.

We’re in a structure called the verification structure.

Do these yellow things simulate what? The cables that are pulling the tension on the heat shield.

We try to get them within five-thousandths of an inch.

So, you’re a metrologist, right? You measure stuff.

Yes, I measure stuff.

You took me all over North Alabama when we were growing up, measuring car parts.

How did you get from car parts to this? After retiring from the auto industry, I worked for a company that served the Air Force, Navy, and Army, measuring various things, including medical devices.

Can we go over to the backside and look underneath it? Sure.

I saw you measuring it the other day. You had two types of measurement devices, right? Yes.

You had a laser scanner that would create a 3D point cloud.

Yes.

And then you had point scanners using corner reflectors, right? Yes, those are monuments in the floor.

So you’re measuring the 3D shape of the sunshield in relation to the floor? Yes, the floor gives us a rough position on the verification structure.

What is the master coordinate system for the James Webb? It’s the J1, J2, J3 system.

So this is the bottom side of the space telescope here.

This is the sunny side.

So why would you have a dark color here? I thought you’d want a light color to reflect the sun’s heat.

That’s a good question. You’d have to ask an engineer about that.

One thing I’ve noticed is there are a lot of holes in the space.

Yes, there are vent holes for air to escape when the sunshield is folded up in the rocket.

So these holes are specifically for deployment? Yes, that’s right.

Once it gets into space, there will be no air conveyance.

Let’s talk about scanning.

The laser scanner is a Pharoah Focus 3D scanner.

You’re used to using coordinate measuring machines, right?

Yes, but this scanner takes a lot of points per second.

So where do you do it? We do it in seven or eight different places.

These spheres are reference points for the scanning process.

Yes, we want to see at least three spheres in view to define a 3D plane.

So you’re getting a hemisphere worth of data? Yes.

The scanner calculates the center of the sphere using an algorithm.

The laser tracker measures individual points to a high degree of accuracy.

This episode of Smarter Every Day is sponsored by KiwiCo, a company that inspires the next generation of learners by sending themed crates to your home.

They come with everything you need to build a project.

We love KiwiCo, and we know your family will too.

If you want to try it out, go to kiwico.com/smarter30 for 30% off your first kit.

So this is the laser tracker, right? Yes, we have monuments drilled into the floor for solid reference points.

We’ve already measured for monuments, so we have a frame of reference.

Can we simulate a measurement now? Yes.

So how do you locate that sphere? The detector knows where the center is supposed to be.

We’ll take measurements around it to get the exact position.

The laser scanner works by shooting photons and measuring the time it takes for them to return.

If I know where I’m pointing my laser, I can calculate a 3D coordinate.

These are laser targets, and they are very precisely located.

The scanner can pick up diffuse reflection much better than specular reflection.

We have a 3D model for the shield in here.

The final data product is a plot of the shape of the membrane in its corrugated frame.

The team has to measure this large sunshield, which is designed to block light.

They position instruments all over the room and add up all the data into one dataset.

The spheres are key to tying all the data together.

They reposition the instruments over several weeks to create a 3D model of the entire sunshield, accurate to five thousandths of an inch.

If you’ve got the surface here, how do you equate that to a weightless environment?

Smarter people than me figure that out.

Once they get all this data, they hand it off to an analyst who does the coordinate transformations.

The reason engineers compare things to models is to see what spots are high and low.

The shape of the sunshield matters because it also dissipates heat.

It’s not just about blocking light; it’s about managing heat.

The shape directs the heat generated at the core outwards.

So my dad was measuring points to predict the shape using a model, and you were validating that model.

Yes, exactly.

Thank you for explaining all of this.

Now, let’s go back to the past and see how the team is finishing up with the data.

This is an art, not just gluing together a potato chip bag.

That’s where the precision comes in.

The curve is called a catenary curve, which is the natural shape a chain or string takes when suspended from both ends.

This force vector defines where the catenary curve is.

The laser tracker can pinpoint precise points, allowing technicians to mark and punch holes accurately.

We measure everything to ensure it’s within specifications.

So this is put together like a big wheel?

Yes, it’s called thermal bonding, a proprietary process.

Mantech owns the process that creates this sunshield.

Bobby, you put a corner reflector here to simulate the telescope, right?

Yes, the surface needs to be flat within 0.005 inches.

How long did it take to get it that flat? About two and a half days.

So tonight is the final layer acceptance shape test.

They’re building a cradle to help insulate and protect the sunshield.

Watching the team fold up the sunshield to ship it out is amazing.

It’s a beautiful and complex process, representing the collaboration of many people to accomplish something extraordinary.

Standing by for terminal count.

And we have engine start and liftoff!

The rocket goes up, and those holes let the air out on ascent.

This is my dad, and there are many stories of people who worked on this telescope.

Many technologies didn’t even exist yet, but each team worked hard to overcome challenges.

In the end, thousands of people came together to make this a reality.

I hope you enjoyed this video. I’m really proud of my dad.

I commissioned a shirt for the James Webb Space Telescope, and if you want one, I’ll leave a link in the description.

Thank you to the patrons for your support.

Have a great day!

—

This version removes any inappropriate or sensitive content while maintaining the essence of the original transcript.