Behind the Webb Episode 21: "All Sewn Up" Transcript of
The sunshield of the James Webb Space Telescope is about the size of a tennis court like the
one Iím walking on right now.
But try to find the material that the sunshield is made of thatís big enough, well youíre
going to be out of luck.
So weíve come to Huntsville, Alabama where the folks at Mantech are building the sunshield.
So John, you are the chief process engineer for the sunshield, can you tell us a little
bit about what kapton is.
(John Cranston/Process Engineer ñ Sunshield) Yes, you have some of the material in your
hands here.
Kapton starts out with this amber color.
This is raw kapton as weíd call it.
After that, kapton has another process where we put the metal coating on it so as you can
see here on one side, thereís the aluminum coating and then we have an aluminum coating
on the other side because on three layers of the sunshield, it has the aluminum coating
and on two layers, it has a silicon coating and thatís what weíd have on the backside
here, we have a silicon coating.
Youíre not going to find this off the shelf, right?
You canít say ëorder some of this thatís the size of a tennis courtí.
Yeah, yeah thatís a real problem because we buy 50 inch wide pieces and itís got to
be the size of a tennis court so we have to put those pieces together and we have a special
process in which we do that and thatís over at our facility just 5 minutes from here.
So can we take a look?
Yes, letís go!
Alright!
What weíre cutting here is individual pieces and theyíll be seamed together.
There are at least 55 pieces per layer of the sunshield
Right and they will match the gold sides to each other to seam itÖ.
Now weíve brought them over to the spot bonding machine.
The adhesion comes out of the tips and into the material to fuse it together but not so
much that it burns through the bottom.
So why do you use a thermal weld?
Youíre not exactly sewing the sunshield together in a traditional sense.
You want to maintain the strength as much as possible to the parent material but have
it sill stay together, not have any glues or anything else that adds weight.
You know, now that Iím looking at it closely, it kind of looks like one of those potato
chip bags, no?
Yeah, like the one I carry around in my pocket?
How convenient!
Well I thought that yíall might have had some Doritos and you always looked on the
inside and you notice the shiny surface?
Yeah, yeah.
Well thatís to protect the insides from contamination.
Because this is a plastic material, it canít meet the requirements of outer space environments.
Kapton has the aluminum coating on it is made specifically for space environments.
Weíve been using it for several decadesÖ.
This is what a sample has to look like.
Itís one inch wide here, two inches wide here.
Hereís hydraulic pressure.
So why this shape?
Thatís the standard that we have to use to test this so that the information we get is
the same when anybody does this test.
They can compare the resultsÖ So now the machineís set up.
Itís ready to go.
Thereís a certain rate that itís pulling it and itís steady.
Now you donít expect to see those kinds of forces on the sunshield.
No weíre going way beyond itís going to be stretched at.
Ok
This is good.
This is a great seam.
Look at this.
31Ö almost 32 pounds.
It far exceeds what JWST needs.
This is great.
This is perfect!
Well, thanks John for showing us how you make the layers of the sunshield so large.
Sure, no problem.
But putting together the sunshield is much more than making it the right size.
Weíll talk more about what else needs to be done on another episode of Behind the Webb.