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one of the most striking features of the

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james webb space telescope is the sun

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shield probably because it's about the

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size of a tennis court now that's too

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big to be sent into space that way so at

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launch it's in a folded up configuration

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when the james webb space telescope

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reaches its destination one million

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miles from earth

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the sunshield is then deployed

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different contractors are working right

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now together on a mechanism or several

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mechanisms to control the sun shields

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deployment one of those is northrop

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grumman's astro aerospace here in

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carpinteria california

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one of the lead project engineers here

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at astro airspace is larry heinlein hey

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larry so what exactly are you guys

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working on here

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this is a mid boom assembly for the

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james webb space telescope

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so what exactly is a mid boom assembly

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so there's one base tube

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and there's five deploying tubes the

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five deploying tubes deploy out and as

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they deploy out they unfold the layers

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and you have separate tubes because

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because during lunch it needs to stow

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within about five feet of length and

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when it's fully deployed it's about 25

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feet but on the end of that boom is a

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five foot long spreader bar which the

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sun shield layers are attached to oh

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okay that puts the layers of the sun

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shield in position right that's correct

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okay kind of reminds me of a antenna of

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sorts

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yes it kind of looks like your

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old-fashioned deploying antenna

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so larry how

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do you make these tubes

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extend

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well inside the carbon graphite tubes is

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something that we call the stem deployer

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and tim martinez will help explain that

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this is called a stem deployer and this

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mounts to the bottom of the base tube

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and this is what drives the assembly and

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pushes the tubes up

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and the way it works is that it pushes

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this material called stem

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out and the concept is like a tape

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measure so

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when it's

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coming out it becomes round but when

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it's around this spool that's inside

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it's flat and there's a motor that

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drives the whole thing out

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it doesn't feel very heavy and but it's

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strong yeah it's it's made out of very

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thin sheet of corrosion resistant steel

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but that's what's what's great about it

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it's really light but it can push up 100

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pounds

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and then there's also a requirement to

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pull back and so you can actually pull

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back 400 pounds and why would you even

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pull back

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once the booms are completely deployed

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it

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pulls back and the tubes are connected

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to a cable which tensions the whole

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sunshield and separates the five

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membranes