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James Webb is fully deployed

nasa.gov

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Re: James Webb is fully deployed

#411

Post by bmitc »

bichiliad wrote: post #250
JohnBooty wrote: post #208

Earlier quoted context omitted.

Great blog post from NASA themselves explaining it: https://blogs.nasa.gov/webb/2022/01/06/why-doesnt-webb-have-... the post is really not very long and I would suggest getting it straight from the horse's mouth, but for those not willing to devote a click here are arguably the most relevant bits! "deployment surveillance cameras would not add significant information of value for engineering teams commanding the spac…

One thing they mentioned that kinda sends it home to me is that the telescope is aimed at the dark and away from the sun, and the other side is especially reflective[0]. In other words, one side is too dark to see, and the other is too bright to see. [0]: https://twitter.com/NASAWebb/status/1479161991252131841

It seems to me that that isn't quite right. "Dark" just means no visible light, but an infrared or thermal camera could see stuff. The article above mentions this possibility and the problems, which are harnessing and operating at cryogenic temperatures.

Re: James Webb is fully deployed

#412

Post by histriosum »

WalterBright wrote: post #330
histriosum wrote: post #235

Earlier quoted context omitted.

There are certainly single points of failure in airliner design. An example that springs to mind is the stabilizer trim jackscrew. There are supporting systems which try to mitigate the risk of failure or the likelihood of failure, but bottom line, if the jackscrew fails, there is no redundancy. You've lost stab trim, potentially making the situation unrecoverable. Of course Alaska 261 is one such example of a jacksc…

I worked for 3 years on the design the 757 stab trim jackscrew. We considered every failure, and had redundancy for it. The AL flight cracked its nut, and the balls fell out. I don't know the details of that design, but on the 757 the ice scrapers on both sides of the nut will hold the nut in place if the balls fall out. If I recall correctly, if the AL pilot had simply left the trim system alone after it failed, and…

I fully agree that the risk tradeoffs made on these designs are highly unlikely to fail. The point is, though, that if they DO fail there IS NO redundancy. There aren't two jackscrew mechanisms. It's a single point of failure. Highly reliable single points of failure don't become redundant because of their high reliability -- they are still single points of failure. And sometimes those must be accepted -- even in safety critical systems.

Re: James Webb is fully deployed

#413

Post by dev_tty01 »

WalterBright wrote: post #319
porsupah wrote: post #281

Earlier quoted context omitted.

They did: "Unlike Hubble, Webb isn't designed to be fixed by astronauts. But it can be refueled robotically. Zurbuchen says that 'once this telescope is deployed, I'm going to put all the effort towards developing that technology, and so within the 10-year lifespan, we can go refuel it'" https://nitter.42l.fr/marinakoren/status/1474367236244750345... https://nitter.42l.fr/Dr_ThomasZ/status/1474398711505580032#...

The astronauts had some serious, unexpected difficulties fixing the Hubble in orbit, and had to improvise. I'm skeptical that blasting a fuel coupling into space, and then trying to figure out how to connect it to a robot, will end well.

I don't know. If the fuel coupling design is compatible with robotic access, it might be doable. That would seem easier than the dozens of repairs that astronauts did with Hubble. I assume we learned a lot with the Hubble servicing missions, some of which will be applicable to robotic work. The full list of Hubble service/repairs is quite remarkable if anyone is interested:

https://hubblesite.org/mission-and-telescope/servicing-missi...

Re: James Webb is fully deployed

#414

Post by ryanSrich »

dreamcompiler wrote: post #410

To me the second most exciting idea about JWST is that it might give us fairly definitive proof that other intelligent life exists in the galaxy. The most exciting idea is if that happens we'll realize they might have built their own version of JWST and proven we exist.

How so? What technology specifically would give the JWST an advantage in discovering new life? Genuinely curious.

Re: James Webb is fully deployed

#415

Post by claaams »

bmitc wrote: post #411
bichiliad wrote: post #250

Earlier quoted context omitted.

One thing they mentioned that kinda sends it home to me is that the telescope is aimed at the dark and away from the sun, and the other side is especially reflective[0]. In other words, one side is too dark to see, and the other is too bright to see. [0]: https://twitter.com/NASAWebb/status/1479161991252131841

It seems to me that that isn't quite right. "Dark" just means no visible light, but an infrared or thermal camera could see stuff. The article above mentions this possibility and the problems, which are harnessing and operating at cryogenic temperatures.

The point of the telescope is to capture IR light from space, if the telescope itself were generating IR light itself it would disrupt the sensor and data that it collects. Part of why its going to take so long for it to begin operating is that it needs to cool down to ultra cold temperatures before beginning operation.

Re: James Webb is fully deployed

#416

Post by nocturnial »

dredmorbius wrote: post #252
ISL wrote: post #27

Earlier quoted context omitted.

If you're in a car being held above the ground by a chain, every single link is a potential single-point of failure.

The classic counterexample to the chain (where each link is a SPOF) is the braided cable or rope, in which each individual strand shares the load collectively, and loss of some fraction of the total strands won't itself cause failure. That's not to say that cables or ropes cannot fail, but when they do so, failure of many individual components is required. A recent example is the failure of support cables for the Are…

Thank you for linking to one of the invidious instances. Youtube itself has become so annoying it's no longer workable for me.

Re: James Webb is fully deployed

#417

Post by dreamcompiler »

ryanSrich wrote: post #414
dreamcompiler wrote: post #410

To me the second most exciting idea about JWST is that it might give us fairly definitive proof that other intelligent life exists in the galaxy. The most exciting idea is if that happens we'll realize they might have built their own version of JWST and proven we exist.

How so? What technology specifically would give the JWST an advantage in discovering new life? Genuinely curious.

1. Its resolution might be high enough to image [big] surface features on exoplanets, and alien megastructures if they exist[0].

2. JWST has extraordinary spectral analysis capabilities and it should be able to characterise gases in extrasolar planetary atmospheres [1].

[0] https://www.popularmechanics.com/space/telescopes/a19346/jam...

[1] https://www.jwst.nasa.gov/content/science/origins.html

Re: James Webb is fully deployed

#418

Post by bmitc »

claaams wrote: post #415
bmitc wrote: post #411

Earlier quoted context omitted.

It seems to me that that isn't quite right. "Dark" just means no visible light, but an infrared or thermal camera could see stuff. The article above mentions this possibility and the problems, which are harnessing and operating at cryogenic temperatures.

The point of the telescope is to capture IR light from space, if the telescope itself were generating IR light itself it would disrupt the sensor and data that it collects. Part of why its going to take so long for it to begin operating is that it needs to cool down to ultra cold temperatures before beginning operation.

Who said anything about generating infrared light? And I don't know what your last sentence is in reference to. Yes, it needs to cool down. Why is that relevant to this discussion other than what's already mentioned about that being a downside to operating cameras?

From the article so people can just debate NASA's own reporting:

> Although infrared or thermal-imaging cameras on the cold side could obviate the need for illumination, they would still present the same harnessing disadvantages. Furthermore, cameras on the cold side would have to work at very cold cryogenic temperatures.

Re: James Webb is fully deployed

#419

Post by voidfunc »

JohnBooty wrote: post #208
daveslash wrote: post #204

Earlier quoted context omitted.

RE>> "I understand the reasons for not putting a camera on or near the JWST" What are the reasons? I'm sorry ~ I'm ignorant on the topic, but I'd love to learn more. Why/what are the reasons?

Great blog post from NASA themselves explaining it: https://blogs.nasa.gov/webb/2022/01/06/why-doesnt-webb-have-... the post is really not very long and I would suggest getting it straight from the horse's mouth, but for those not willing to devote a click here are arguably the most relevant bits! "deployment surveillance cameras would not add significant information of value for engineering teams commanding the spac…

Once again scientists miss the entire point. It is about marketing and making people interested.

It makes it easier when you go back five years later and ask for more money if people can see the multi-million dollar toy they paid for.

Re: James Webb is fully deployed

#420

Post by ezconnect »

dev_tty01 wrote: post #345
JohnBooty wrote: post #208

Earlier quoted context omitted.

Great blog post from NASA themselves explaining it: https://blogs.nasa.gov/webb/2022/01/06/why-doesnt-webb-have-... the post is really not very long and I would suggest getting it straight from the horse's mouth, but for those not willing to devote a click here are arguably the most relevant bits! "deployment surveillance cameras would not add significant information of value for engineering teams commanding the spac…

Yes, I get all of that, but they still missed an excellent PR opportunity. NASA really could have built some engagement showing images of the deployment process, even if the images wouldn't have direct scientific benefit. Good PR leads to improved funding which leads to more science.

The data it provides is enough to get funding or not, Voyager still provide data.
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