A “Seamless” Unfolding

• By Maggie Masetti
• October 13, 2014
• Comments Off on A “Seamless” Unfolding

Recently, there was a Google Plus hangout with NASA and Northrop Grumman to talk about the James Webb Space Telescope’s giant sunshield. This sunshield is, as someone on Twitter pointed out, big enough to host a very awkward game of tennis. (Yep, it’s for real the size of a tennis court!)

Credit: NASA/Chris Gunn

The sunshield is a really important part of the telescope – it will also point in the direction of the Sun, Earth, and Moon, keeping the optics and instruments cold. This will allow them to observe the faint heat signals of things like the most distant stars and galaxies. It is made of five layers of Kapton, a thin material not unlike what those metallic, mylar party balloons are made of. Why is this material so thin – about the thickness of a human hair? Because the satellite has to be folded up to fit in its rocket – and folding up five layers of sunshield could be quite difficult if it were too bulky!

Here’s a video that shows the timescale of JWST’s deployment:

The five layers also really do an impressive job in keeping the telescope cool. Each layer is carefully shaped and spaced to allow heat to reflect away from the spacecraft. (This is especially key when it comes to the only “hot” things on the cold side of the telescope – the electronic boxes for the instruments. The sunshield also reflects that heat safely away.) As Jon Arenberg says in the Hangout, you could boil water on the hot side of the spacecraft – and liquify nitrogen on the cold side.

Credit: Northrop Grumman/Alex Evers

Northrop Grumman is NASA’s prime contractor for the telescope and they are the ones designing and building the sunshield. A major test was conducted recently, where, for the first time, five sunshield test layers were unfolded and separated.

Credit: Northrop Grumman/Alex Evers

“These tests are critical and allow us to see how our modeling works and learn about any modifications we may need to make in our design as we move into sunshield flight production,” said Jim Flynn, JWST sunshield manager. The three-day test took place in July, taking seven engineers and six technicians about 20 hours to complete. On orbit, the sunshield will take several days to unfold.

“Tests on the ground are a little bit tricky because we have to account for gravity,” says Flynn. “Webb won’t face those same challenges in space. To overcome challenges on the ground, our technicians came up with the idea to rest the layers on a structure of metal beams covered by plastic.”

Credit: Northrop Grumman/Alex Evers

Credit: Northrop Grumman/Alex Evers

You can view more photos on Flickr.

And you can watch the Google Plus hangout in its entirety here: