How a sunshield protects NASA’s James Webb Space Telescope


The James Webb Space Telescope (JWST) is hectic unwrapping itself, making a grand entryway to its brand-new house about 930,000 miles (1.5 million kilometers) from Earth. JWST will observe faint far-off items in infrared light, and due to the fact that heat likewise takes a trip as infrared radiation, JWST requires to run under extremely picky temperature level conditions.

“It can’t have other sources of heat,” states James Cooper, a NASA engineer. “It’ll just swamp the science you’re trying to get.”

The telescope’s mirror and instruments require to be kept listed below about -370°F (-223°C)—cold sufficient to freeze nitrogen. That’s no simple job when the sun’s rays and the spacecraft bus, which consists of JWST’s main computer system and interactions, can warm the telescope and its instrumentation approximately a tropical 230°F (110°C). 

Fortunately, JWST has a cooling gadget of its extremely own: a sunshield, as its developers call it. Shaped like a kite, the size of a tennis court, and made from layers less than a millimeter thick, JWST’s sunshield has the ability to cool the telescope by numerous hundred degrees.

Getting that sunshield to work has actually been a long and tortuous job. Cooper has actually assisted lead the sunshield’s advancement for more than a lots years, and he’s seen much of the trials and adversities the structure conquered in order to work.

Planning JWST took years, and its designers understood they desired a sunshield early on in the advancement procedure, even prior to Cooper came aboard. To develop the sunshield, the designers took a look at numerous plastic-like products prior to picking one called Kapton. 

Kapton isn’t a brand-new product—it’s a essential worldwide of cryogenics, considering that its thermal residential or commercial properties benefit keeping extremely cold things cool. Additionally, Kapton, states Cooper, is “tougher than most similar [materials] and it doesn’t tear as easily, and it’ll survive the space environment better.”

JWST isn’t Kapton’s very first flight into space. It was utilized to insulate the engines on Apollo’s lunar modules; people have actually actually scattered it throughout the moon. There, lunar modules had a propensity to blow it about when astronauts took off to start their return journeys. Neil Armstrong remembered that, when Apollo 11 rose from the lunar surface area, he might see Kapton “scattering all around the area for great distances.”

More just recently, New Horizons utilized Kapton to keep its temperature level steady as it travelled from Earth to zip Pluto and Charon in the planetary system’s freezing external reaches. 

JWST’s sunshield is made from 5 layers of Kapton, each the density of a human hair. The layers are separated by vacuum spaces to avoid heat from carrying out through the entire guard.

Each layer is covered with aluminum, and the 2 layers nearest the sun are likewise covered with drugged silicon. In addition to making the sunshield more reflective, these metals enhance its electrical conductivity—to prevent fixed electrical energy developing inside the sheets.

Moreover, each layer’s edges needed to line up, and each layer needed to be pulled tight and flat. The spacing required to be even to avoid heat from getting caught in the middle of the guard.

What the James Webb Space Telescope ought to appear like when it lastly unfurls beyond the Earth’s environment. Adriana Manrique Gutierrez/NASA’s Goddard Space Flight Center/CIL

When it came time to put together the sunshield, the NASA group dealt with another obstacle. “The Kapton comes in 4-foot-wide sections, and we need a 70-by-45-foot sunshield, roughly,” states Cooper. “And so we had to seam it together.” 

They did this by basically melting the edges together, and including extra strips as “rip-stops” to assist avoid tears. Even if one location tears, the rip-stops will separate the issue and enable the remainder of the sunshield to run as prepared—or so the designers hope.

Piecing together the sunshield was just half of the obstacle. For the telescope to suit the Ariane 5 rocket that released from French Guiana on Christmas Day, the sunshield required to be folded and attached with pins. It was a puzzle: the guard needed to be protected when folded, functional when unfurled, all while preventing damage to the fragile product.

“You end up with 25, 30 layers of membrane — and you have the [pin] holes all line up, so you can put a pin through them — and they have to line up every time you fold it,” states Cooper. “And developing the tools to do that was a massive challenge, because you also can’t have those holes line up with each other when you’re deployed, or the sun comes right through.”

[Related: After years of delays, the James Webb telescope is finally in space]

They required to best the system for launching the sunshield. Unfolding the guard counts on 107 various release gadgets. If even among those gadgets stops working, then the whole telescope is jeopardized. And the NASA engineers needed to make sure the tethers holding it together didn’t unintentionally snap and graze the guard. “So we had to spend a lot of effort on looking anywhere that a cable could possibly go,” states Cooper. And they needed to check all of this on the ground—far from the microgravity where the telescope’s guard will really unfurl.

But now, all of that lags them. The launch has actually gone efficiently up until now–in truth, it utilized much less propellant than anticipated, which NASA anticipates will extend the observatory’s life time by years. On Tuesday, JWST started to unwind the sunshield. If all goes according to strategy, it will continue to gingerly unfold its cooling armor till January 3.



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