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James Webb is fully deployed

nasa.gov

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Re: James Webb is fully deployed

#43

Post by systemvoltage »

ISL wrote: post #27
ducktective wrote: post #26

Earlier quoted context omitted.

>344 single points of failure How can a system have more that one single point of failure?

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

But the chain itself can be considered as one component and it becomes a single point of failure. Or if we go in the opposite direction, then we can breakdown links and say "Every single grain boundary is a single point of failure".

Re: James Webb is fully deployed

#44

Post by [deleted] »

rich_sasha wrote: post #17
elefanten wrote: post #10

For those not up on the project, what are some of the earliest novel types of information we expect to receive from it?

Huge. This is the first large telescope observing in far infrared. Some things: - very early galaxies (so far that they are redshifted to far IR). Hence the “looking into the start of the Universe” talk). We know they are there, and that they are unusual and super-interesting, but just can’t see them. I think this is high on the agenda so I’m guessing some PR shots of ancient galaxies are due. - cold objects nearby;…

[deleted]

Re: James Webb is fully deployed

#45

Post by marcosdumay »

dgrin91 wrote: post #23

One of the big numbers that been thrown around is that JWST has 344 single points of failure in its mission. Now that deployment has been completed, is there somewhere that lists how many of those points we have passed?

AFAIK no single mirror segment failure would destroy the entire telescope, so the only one still on the future is the L2 insertion burn.

As always, it's useful to post this link:

https://jwst.nasa.gov/content/webbLaunch/whereIsWebb.html

Re: James Webb is fully deployed

#46

Post by mabbo »

elefanten wrote: post #10

For those not up on the project, what are some of the earliest novel types of information we expect to receive from it?

The full list of the first set of scientific missions is available here: https://www.stsci.edu/jwst/science-execution/approved-progra...

The overall idea is that JWST can see very faint objects in the infrared spectrum. The analogy I've heard is that it could pick out a bedroom nightlight on the moon from earth.

Re: James Webb is fully deployed

#47

Post by lordnacho »

ducktective wrote: post #26
dgrin91 wrote: post #23

One of the big numbers that been thrown around is that JWST has 344 single points of failure in its mission. Now that deployment has been completed, is there somewhere that lists how many of those points we have passed?

>344 single points of failure How can a system have more that one single point of failure?

I think SPF means a construction where there's no redundancy provided? Though it does raise the question of how this is counted: table with 4 legs, any of them breaks, table is still standing. Table with three legs, any of them breaks, table is broken.

Re: James Webb is fully deployed

#49

Post by ISL »

systemvoltage wrote: post #43
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.

But the chain itself can be considered as one component and it becomes a single point of failure. Or if we go in the opposite direction, then we can breakdown links and say "Every single grain boundary is a single point of failure".

Partially-agreed on the former, but not the latter.

So long as the chain is not loaded near its tensile limit, then the grain boundaries that support the load within each link do so in parallel and are therefore redundant.

The selection of the allegory of the chain was intentional -- each link must be properly formed, or the entire chain will fail. If it breaks, it is surely correct to say, "the chain broke", but in truth, it was actually link-86.

For JWST, the remarkable/audacious thing is that many links in the chain from launch to observation are potential single-point failures. Furthermore, many of them haven't ever been tested independently in space... ever. It is a hell of a triumph that JWST has gotten this far already.

If even a small fraction of the instrumentation works at this point, we are going to learn a ton about the universe, simply due to JWST's position, collecting-area, and mirror-diameter.

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