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James Webb Space Telescope emerges successfully from final thermal vacuum test

phys.org

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Re: James Webb Space Telescope emerges successfully from final thermal vacuum test

#81

Post by NikolaeVarius »

teraflop wrote: post #74
NikolaeVarius wrote: post #7

Man, I really want this telescope to succeed its mission, but I just can't get over how complex its deployment procedure is. I am extremely pessimistic about it actually managing to deploy as planned.

That's what I thought about Curiosity's skycrane, and that ended up working out pretty well. Yes, it's complicated, but I'm willing to accept that my intuitions about whether something is too complicated are wrong when we're talking about something that actual rocket scientist have spent millions of hours planning.

I don't recall ever saying it was too complicated. I only indicated extremely complex, which it is. Millions of man hours have been lost to bad units. Rocket scientists are human.

Re: James Webb Space Telescope emerges successfully from final thermal vacuum test

#82

Post by JudgeWapner »

mdorazio wrote: post #38
jcadam wrote: post #37

Earlier quoted context omitted.

Just a bit of warning: Software Engineering in Aerospace is NOT fun. You're basically in a supporting role to the hardware and system engineers designing the spacecraft. It's pure drudgery... process to the point of absurdity, specs and tasks being spoon fed to you with little room for creativity and/or problem solving, etc. The pay, benefits, and level of respect on the job reflect all of that. If you really want to…

To be fair, the reason for this is that if you try to be creative and don't follow strict processes, things fail a million miles from Earth or blow up entirely.

You mean the strict processes that strictly demanded mixing imperial and SI units ?

Re: James Webb Space Telescope emerges successfully from final thermal vacuum test

#83

Post by zanny »

jjoonathan wrote: post #76
NikolaeVarius wrote: post #45

Earlier quoted context omitted.

We also can't fix this, because it was designed to be unfixable. Making it fixable would counter productively make the design more complex.

With a $10 billion telescope dead in the water and the clock ticking, Louis Rossman leads a crack team of Apple repairmen -- specialists in fixing sytems designed to be unfixable -- through accelerated astronaut training for a last-chance human mission to L2! Will they save the day? Or will the inky clutches of space doom the mission and leave them stranded farther from civilization than any human in history?

Starring Bill Nye and Neil deGrasse Tyson as Bill Nye and Neil deGrasse Tyson.

Re: James Webb Space Telescope emerges successfully from final thermal vacuum test

#84

Post by zanny »

sandworm101 wrote: post #30

Obligatory xkcd: https://xkcd.com/2014/ 2026? Probably not. 2021? I doubt it. My money is on 2023-24.

They already built the damn thing, how hard could it be to land it in stable orbit 1.5 gigameters from the planet? This ain't rocket science, people. Wait a second.

Re: James Webb Space Telescope emerges successfully from final thermal vacuum test

#85

Post by warent »

NikolaeVarius wrote: post #81
teraflop wrote: post #74

Earlier quoted context omitted.

That's what I thought about Curiosity's skycrane, and that ended up working out pretty well. Yes, it's complicated, but I'm willing to accept that my intuitions about whether something is too complicated are wrong when we're talking about something that actual rocket scientist have spent millions of hours planning.

I don't recall ever saying it was too complicated. I only indicated extremely complex, which it is. Millions of man hours have been lost to bad units. Rocket scientists are human.

I'm not sure why you're splitting hairs on this. GP is merely addressing your "extreme pessimism" but now for whatever reason you're either arguing semantics or showing some kind of cognitive dissonance.

Re: James Webb Space Telescope emerges successfully from final thermal vacuum test

#86

Post by neurostimulant »

NikolaeVarius wrote: post #7

Man, I really want this telescope to succeed its mission, but I just can't get over how complex its deployment procedure is. I am extremely pessimistic about it actually managing to deploy as planned.

For a project this magnitude, I think they should build a spare telescope or two to account for launch failures. Or is it not how the space industry operates?

Re: James Webb Space Telescope emerges successfully from final thermal vacuum test

#87

Post by java-man »

neurostimulant wrote: post #86
NikolaeVarius wrote: post #7

Man, I really want this telescope to succeed its mission, but I just can't get over how complex its deployment procedure is. I am extremely pessimistic about it actually managing to deploy as planned.

For a project this magnitude, I think they should build a spare telescope or two to account for launch failures. Or is it not how the space industry operates?

exactly my sentiment!

why not build two, given the fact that most of the budget is likely to be R&D costs.

Re: James Webb Space Telescope emerges successfully from final thermal vacuum test

#88

Post by falcrist »

teraflop wrote: post #74
NikolaeVarius wrote: post #7

Man, I really want this telescope to succeed its mission, but I just can't get over how complex its deployment procedure is. I am extremely pessimistic about it actually managing to deploy as planned.

That's what I thought about Curiosity's skycrane, and that ended up working out pretty well. Yes, it's complicated, but I'm willing to accept that my intuitions about whether something is too complicated are wrong when we're talking about something that actual rocket scientist have spent millions of hours planning.

I can't let go of my intuition that complex deployment procedures carry an inherent additional risk to the mission.

Now, maybe that additional risk is less than the risk of doing it a different way, but that just means the mission is particularly risky. That appears to be the case with the JWST in any case.

Space is hard. We've failed many times. It seems rational to be concerned in this case.

Re: James Webb Space Telescope emerges successfully from final thermal vacuum test

#89

Post by ziotom78 »

CydeWeys wrote: post #75
rakoo wrote: post #56

Earlier quoted context omitted.

Minor nitpick, but the L2 point is selected so it doesn't need fuel to stay there. It's like a gravity well of the earth/sun system, any object getting a little further from it will get back to it.

L2 is unstable. There are stable Lagrange points that would be much better for this purpose if that was the reason. The unique thing about L2 is that it's the only Lagrange point where the Sun is always blocked by the Earth. That's what they're going for here.

Not entirely true. Spacecrafts orbiting L2 do not stay still with respect to the Earth; rather, they follow a Lissajous orbit, which is quite efficient given the gravitational properties of the L2 point. Therefore, they will observe the Sun quite often. (The apparent size of the Sun from L2 is roughly the same as Earth's, so eclipsing the Sun would be too complicated.) And this is not bad, because otherwise solar panels could never produce the power necessary for the spacecraft to work!

The real reason why L2 is so interesting is that it violates Kepler's third law: despite being farther from the Sun than Earth, the orbital period is still the same as Earth, because of the gravitational attraction of Earth itself. This allows the spacecraft to keep the same distance from Earth during the year, which eases communications with ground stations.

(Disclaimer: I have been part of the Core Team of the ESA Planck mission, which flew around L2 like JWST will do.)

Re: James Webb Space Telescope emerges successfully from final thermal vacuum test

#90

Post by topspin »

NikolaeVarius wrote: post #7

Man, I really want this telescope to succeed its mission, but I just can't get over how complex its deployment procedure is. I am extremely pessimistic about it actually managing to deploy as planned.

Yes, the deployment looks like a lengthy and risky operation. But the risks don't end there. The Northrop Grumman cryocooler has been a major problem for JWST, requiring years of development and rework. If it fails then some of the most crucial instruments are useless.
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