With Webb Telescope's Mid-Booms Extended, Sunshield Takes Shape (nasa.gov) 45
"With the successful extension of Webb's second sunshield mid-boom, the observatory has passed another critical deployment milestone," NASA announced Friday, adding that the sunshield "now resembles its full, kite-shaped form in space..."
The completion of the sunshield cover and mid-boom deployments over the past two days marks a critical milestone for Webb: all 107 membrane release devices associated with the sunshield deployment — every single one of which had to work in order for the sunshield to deploy — have now successfully released. Webb has 178 of these 'non-explosive actuators' in all; 107 were used to keep the sunshield safe and folded prior to deployment...
While the deployments took longer than expected today, that was due to the operations team moving forward with caution and according to the protocols they laid out for dealing with unpredictable situations...
The two mid-boom arms are now locked in their final position. They will hold the sunshield membranes in their proper place, as the team turns to the final stage in the sunshield's deployment: tensioning. In the coming days, the team will separate and then individually tension each of the five sunshield layers, stretching them into their final, taut shape. This will create space between the membranes to allow heat to radiate out, making each successive layer of the sunshield cooler than the one below... Sunshield tensioning will take at least two days but may take longer, due to the complexity of the process and the flexibility built into the timeline.
Universe Today shares a video showing the complexity of the sunshield operation. Long-time Slashdot reader necro81 writes that "Unlike other nail-biting JWST events like the rocket launch, something of this size and complexity has never been attempted in space.
"After this, the telescope's optics will be in the shade forevermore, and can begin cooling to the frigid operating temperature needed to detect infrared light."
While the deployments took longer than expected today, that was due to the operations team moving forward with caution and according to the protocols they laid out for dealing with unpredictable situations...
The two mid-boom arms are now locked in their final position. They will hold the sunshield membranes in their proper place, as the team turns to the final stage in the sunshield's deployment: tensioning. In the coming days, the team will separate and then individually tension each of the five sunshield layers, stretching them into their final, taut shape. This will create space between the membranes to allow heat to radiate out, making each successive layer of the sunshield cooler than the one below... Sunshield tensioning will take at least two days but may take longer, due to the complexity of the process and the flexibility built into the timeline.
Universe Today shares a video showing the complexity of the sunshield operation. Long-time Slashdot reader necro81 writes that "Unlike other nail-biting JWST events like the rocket launch, something of this size and complexity has never been attempted in space.
"After this, the telescope's optics will be in the shade forevermore, and can begin cooling to the frigid operating temperature needed to detect infrared light."
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Not at L2.
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Just send them to L1 duh! Perfect spot!
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Or launch them at night.
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Re:Sunshield[s could have many applications] (Score:3, Interesting)
Really feeble and basically off-topic FP, and also an old idea. Why FP it?
But if we wanted to do that it should be an orbiting array of simple stretched loop mirrors that are rotated as needed, either to block some of the sun's light, to let the light pass, or even to reflect extra sunlight to other parts of the earth. But I wouldn't try it if it were the planet of us, and it would be. Our weather and climate modeling capabilities are nowhere near sufficient for the purpose. Considering the butterfly proble
Re:Sunshield (Score:4, Insightful)
If we put enough satellites with sunshields in orbit, we could prevent global warming
And if we burned off all the hydrocarbons on earth for rocket fuel, we might just be able to do that. Just call us fkd, because that would be one dark wet hole.
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I'd imagine that the sunshield material would have to be mined from asteroids or something, since lifting it all out of Earth's gravity well seems impractical.
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Blocking sunlight in bulk is probably not desirable. It would make solar panels less efficient as well as photosynthesis less efficient. Both solar panels and photosynthesis are much more useful to prevent global warming. We would be much better off building large solar arrays to collect the sunlight (which reduces our reliance on fossil fuels) and/or planting more trees to absorb the CO2 than we would be blocking the sun from getting to us. And that's before we get to whether we know how to target wh
Courage in Engineering (Score:5, Insightful)
Our society does not normally associate engineering with personal fortitude, but I look at what this team has done. To even attempt this must require cerebral self-confidence at a level few humans live with.
True they are not risking anyone's life here, but imagine what their emotional state would be if this thing falls apart and fails. I'm sure they have.
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True they are not risking anyone's life here, but imagine what their emotional state would be if this thing falls apart and fails. I'm sure they have.
^ This. The timeframes are insane, some of these people have been working on it since 1996. Really we are losing something valuable by not recording more of their response. I mean the drama of losing thousands of people’s life work simultaneously combined with the condensed moments of high stakes procedures, the anxiety must be as palatable as the profits if it’s done right. Society would be better off enjoying these like a sporting event where we all cheer on triumphs over nature.
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There's a reaction video on Youtube of the JWST launch, from an astrophysicist who's busy in the kitchen at home cooking her family's Xmas turkey while doomscrolling the live video of the launch on a tablet. It's simultaneously hilarious and nervewracking.
"Nominal, nominal, nominal!"
https://www.youtube.com/watch?... [youtube.com]
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Real Programmers Don't Use Pascal (Score:3)
https://www.usm.uni-muenchen.d... [uni-muenchen.de]
"Allegedly, one Real Programmer managed to tuck a pattern-matching program into a few hundred bytes of unused memory in a Voyager spacecraft that searched for, located, and photographed a new moon of Jupiter."
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How would Voyager search for a moon? Take photos in random directions and discard every photo that only contains black?
Test for being a Real Programmer (Score:2)
I guess -- if someone doesn't write the code to do such a brute-force search, it won't happen.
I think the cool part wasn't also locating a moon of Jupiter, it was also locating enough memory on the spacecraft to place the search algorithm.
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I'd say courage is pretty fundamental to being an engineer, at the very least because as an engineer people depend on you having integrity, which takes courage. Engineers sometimes seem risk-averse to others, because we don't enjoy the luxury of wishful thinking.
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And lots and lots and lots of nailbiting.
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First Image - SFW (Score:5, Funny)
https://i2.wp.com/www.powerlin... [wp.com]
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More info. (Score:5, Informative)
Also: The Insane Engineering of James Webb Telescope [youtube.com]
Also: Space.com's Sunshield Deployment Explainer [space.com]
Follow along with NASA's blog [nasa.gov] and Deployment Explorer [nasa.gov]
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Do you have a link to any info on this sensor malfunction? NASA and the official JWST websites are mum on this issue.
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Re:Sensors did not trigger. NASA have not explaine (Score:4, Informative)
"Switches that should have indicated that the cover rolled up did not trigger when they were supposed to. However, secondary and tertiary sources offered confirmation that it had. Temperature data seemed to show that the sunshield cover unrolled to block sunlight from a sensor, and gyroscope sensors indicated motion consistent with the sunshield cover release devices being activated." https://blogs.nasa.gov/webb/ [nasa.gov]
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SNAFU for life, I guess. Not even worth mentioning here, I think.
Re:Sensors did not trigger. NASA have not explaine (Score:5, Informative)
First, it wasn't sensors for the sun shield, it was sensors for the shield covers. Second, it only happened a day ago, half a million miles away. Do you really think they have had time to analyze exactly why they didn't trigger? And of course they were important, or they wouldn't have been there. But also as obvious, they weren't critical, because they were able to use other means to determine the covers had rolled up. And since the shields are now deployed, it seems they were correct.
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The sensors for the sunshield did not trigger.
No-one has said why, or if that happened on the ground, or if it is important.
SNAFU for government work, I guess.
Unlike all those SNAFUs in private industry which have cost people their lives.
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You are maybe not familiar with NASA's Space Shuttle cover up ?
Wonder how often the have to counter solar wind (Score:2)
One aspect of a solar shield like this is, it seems like it would act a bit like a solar sail... I'm sure they designed it to minimize the effect but I wonder how often they have to correct for the movement generated by the sunscreen being in the path of solar wind?
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There's an "aft momentum flap" on the end of one shield boom that counteracts solar pressure on the shield and negates the turning moment caused by the asymmetric pressure. It was deployed successfully a couple of days ago, spring-loaded like a lot of other things on the JWST.
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There's an "aft momentum flap" on the end of one shield boom that counteracts solar pressure
Wow thanks, I'll have to look up some details on that! Pretty cool tech, seems like a pretty complex thing to put in orbit but I guess it works!
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The aft momentum flap is actually incredibly simple, a fold-out reflective panel that's just the right size and fixed at the right angle to provide a few extra milliNewtons of thrust from the solar wind to one side of the spacecraft to counteract the extra solar wind pressure on the other, larger side of the solar sunshield. That saves the spacecraft's attitude management system from having to expend energy via the reaction wheels to push back and keep the telescope stable, for the cost of a few grams of ex
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Sunshield doesn't mainly "radiate heat" (Score:5, Insightful)
This will create space between the membranes to allow heat to radiate out, making each successive layer of the sunshield cooler than the one below..
While there may be a little contribution from radiation from between the layers, the sunshield works from a different principle. Multilayer insulation does not require a side opening where the extra energy can "radiate out." cf. Liquid helium containers, which use multilayer insulation wrapped entirely around the inner container.
Multilayer insulation works because radiative power between two surfaces of different temperatures goes like the fourth power of the temperature. Each intermediate layer radiatively comes to an equilibrium temperature lower than the one next to it, closer to the heat source, and that fourth power of the temperature takes over and dramatically reduces the radiative load. The radiative power is additionally reduced by using high-reflectivity (i.e. low-emissivity) coatings on the layers.
JWST has the additional advantage that the telescope itself is facing deep space, so that it radiates power away. That's why everything on the cold side (excluding the mirror) is black; it maximizes the radiated power.
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JWST has the additional advantage that the telescope itself is facing deep space, so that it radiates power away. That's why everything on the cold side (excluding the mirror) is black; it maximizes the radiated power.
I had not thought about the fact that the radiator on the back of the main mirror is black, so I was curious about the physics. Here's more detail on black body radiation [stackexchange.com]