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James Webb is fully deployed

nasa.gov

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Re: James Webb is fully deployed

#121

Post by gitgrump »

davesque wrote: post #86

This feels perhaps like a silly comment, but I have this intuition that the data collected by JWST could prove to be some of the most important ever collected.

I keep telling people that, no matter what, we're going to learn something cool about the universe. I'm so excited to see these images. I mean, imagine humans 10,000 years ago, just surviving, maybe figuring out agriculture, and thinking about their place in the world. They looked up at the stars in wonder. Now, we've progressed to the point where we can polish gold down to the nanometer, and we're sending a giant hunk of origami circuits out to L2 to squint back to nearly the beginning of time as part of our eternal quest for answers.

Your comment is not silly.

Re: James Webb is fully deployed

#122

Post by WalterBright »

macintux wrote: post #89
WalterBright wrote: post #75

Since 90% of the cost is probably in R+D of the telescope, one could build and deploy another for another 10%. Why isn't this done? Why is every space telescope completely unique?

I believe in this case it's not 90%. Much of the cost here was (on the ground) assembly and testing, given the intricate nature of the setup.

What about all the costs in developing the test procedures? Obtaining the test equipment. Designing and building the test rigs. Designing, coding, and debugging the test software. Training people on how to do the tests. Endless committee meetings on if the tests are accurate and complete. Failure analysis. I bet they're enormous.

Running the same tests again on another part would be at very little incremental cost.

Re: James Webb is fully deployed

#123

Post by WalterBright »

lazide wrote: post #88
WalterBright wrote: post #75

Since 90% of the cost is probably in R+D of the telescope, one could build and deploy another for another 10%. Why isn't this done? Why is every space telescope completely unique?

When it takes so long to build, it’s already obsolete by the time it gets launched. If you made a new one every year, it wouldn’t be so bad of course, but a decade+? Oof. It was so bad they kept redesigning it mid way through to upgrade things as new discoveries were made, which caused even more delays.

> redesigning it mid way through

And that doesn't have to be redone when making a copy.

Re: James Webb is fully deployed

#124

Post by Crash0v3rid3 »

davesque wrote: post #91
emptyfile wrote: post #60

Amazing feat of engineering. NASA can be proud of achieving something that no other space agency could do. It took courage to keep shovelling money and effort into this project and some amazing science to get it deployed into space.

I agree with the sentiment, but I think some people might take issue with the suggestion that this was entirely NASA's achievement.

Who else was involved?

Re: James Webb is fully deployed

#125

Post by BurningFrog »

WalterBright wrote: post #75

Since 90% of the cost is probably in R+D of the telescope, one could build and deploy another for another 10%. Why isn't this done? Why is every space telescope completely unique?

I know nothing specific about the JWST, but here is a theory:

NASA is a government agency, which makes what it does ultimately political.

In a political "economy", the return on investments is mainly PR. Politicians aim to get voter sympathy in return for investing $B in NASA.

And voters won't much care if you put up 3 JWSTs or 1.

Re: James Webb is fully deployed

#126

Post by wolverine876 »

WalterBright wrote: post #75

Since 90% of the cost is probably in R+D of the telescope, one could build and deploy another for another 10%. Why isn't this done? Why is every space telescope completely unique?

> 90% of the cost is probably in R+D of the telescope

While I might have guessed that, IIRC someone at NASA said that most of the cost is parts, assembly, and testing of a massive, highly sensitive, highly unusual custom build. Many (most?) parts are custom made, and even finding vendors to make them again would be difficult - wasn't the manufacturing completed several years ago? Again, IIRC, they said a second one might even cost more.

Re: James Webb is fully deployed

#127

Post by adrianmonk »

jes wrote: post #70
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.

In a real chain, only one link is actually the weakest, and it is at that link where the chain will break, in the hypothetical you offer.

This assumes the environment is completely predictable.

If you know the strength of every link in the chain with perfect accuracy, and you know that the only potential cause of failure is too much weight being placed on the chain, then the only link that can fail is the weakest[1] one because no other failure can happen before that one.

But really you need to design for the idea that various things might happen. Someone else gave the example of a person choosing a link to cut with bolt cutters. The person's choice is what's not predictable in that example.

---

[1] And if you assume it's not possible to have two links that are exactly as strong as each other.

Re: James Webb is fully deployed

#128

Post by wolverine876 »

ajuc wrote: post #116
Server6 wrote: post #87

Earlier quoted context omitted.

Why would we need two? I would think the next one 20+ years from now would hopefully be exponentially better.

In 10 years we can send a bigger, simpler, cheaper, one-piece, non-foldable telescope in Starship for a fraction of the cost. The biggest saving wouldn't even be the launch costs - it would be the simple design allowed by relaxing the volume and mass constraints.

If only most of the cost was folding it (and if only Elon Musk's solutions somehow changed all the problems to fit them).

Re: James Webb is fully deployed

#129

Post by WalterBright »

irdc wrote: post #81
WalterBright wrote: post #72

What puzzles me is the maneuvering fuel. When that fuel runs out, the telescope can no longer orient itself. This ended the life of the Kepler telescope. But aren't there other ways to orient in space? 1. use pressure from the solar wind 2. have 3 electric motors on 3 axis. Wouldn't spinning those motors rotate the craft? Electric power to do it would come from solar panels, giving it plenty of fuel.

They've already mentioned having more than the of amount of manoeuvring fuel (or, as we should really be calling it, delta-v) they had planned to have left at this point. Space craft have a limited life time anyway (CCD's wear out, semiconductors are subject to electron migration, solar panels degrade), so having a limited amount of fuel to stay at Sol-Earth L2 is just part of the whole lifetime equation.

Right, but NOVA said that running out of fuel ended Kepler.

Re: James Webb is fully deployed

#130

Post by ianai »

WalterBright wrote: post #119
sailingparrot wrote: post #102

Earlier quoted context omitted.

Because it's a wrong assumption. Significant cost come from the assembly and testing of all the components itself, that you would have to redo entirely. Also if you were to build just 2 or 3 of them, you can't expect any economy of scale. On top of that, the operational cost of JWST is expected to be around 1B$ for it's lifetime, you could expect that to be similar for every single replica you have. And finally, you…

Assuming your figures are correct, you'll get double the data for another 30% cost. If you wait a month before launching #2, if problems appear in #1 (like the telescope mirror was ground improperly) it can be fixed in #2. The operational cost will not double. The same ground facility, equipment, and staff can manage both. If you're buying two identical launches, you can get a quantity discount. > the benefits of a s…

Agree. A replica wouldn’t have to be sent to L2 for that matter. Pretty sure a lot of science could be done with even a slow trajectory leaving the solar system, if orbiting something else is infeasible.
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