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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

#141

Post by jvanderbot »

bdamm wrote: post #123
mikeash wrote: post #106

Earlier quoted context omitted.

If SpaceX’s Starship/Super Heavy (née BFR) actually pans out, it should be able to easily perform this mission.

With the irony being that if BFR pans out, this mission could have ended up being launched on it and eliminate a pile of complexity in the process. The mirrors wouldn't have to be hinged, for example.

Imagine going back to 1984, and telling the Hubble successor team "Just wait for a future heavy commercial space launch before planning any larger telescopes".

Or to 1997, and telling Goddard "Your specs will require technological development that we feel should be halted until a commercial spaceflight program develops. We're pretty sure next year someone will found a e-commerce business that will make him a billionaire, and he'll sort it all out."

Or to 2002, when tech internet tech was booming and paypal was going IPO, to tell TRW that the $824 million they just acquired should be put on a shelf until about 20 years later.

Or to 2005, 12 years before BFR was announced, when it appeared cost growth was a factor (not at all related to northrup aquisitions). Again, 2010 it passed review, 7 years before announcement. Is it really irony or somehow a waste? I don't think so.

(Full disclosure: I'm working on alternative tech to deoployables for large-aperture telescopes, but I greatly appreciate their efforts on JWST, given what we had over the last 20 years).

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

#142

Post by toomuchtodo »

petschge wrote: post #133
ATsch wrote: post #129

Earlier quoted context omitted.

wasn't there an experiment that used laser interferometry to calculate the precise distances between a constellation of three satellites? I assume something like that could work?

That was the LISA Pathfinder mission ( https://en.wikipedia.org/wiki/LISA_Pathfinder ), the preparatory step for a gravitational wave detector in space. And yes something like that could work eventually. Right now we are doing science on that concept. It takes a decade or three to get the technology mature enough that you can do astronomy with it.

In some StarLink thread on /r/spacex, someone was mentioning that you can't do IR/optical light interferometry without being able to measure the phase of light, and someone else said we're pretty close to being able to.

If you're able to deploy orbital observatories with a StarLink sort of cadence (keep throwing up cheap satellites as quickly as possible), would you think we'd reach more mature observation tech faster? Maybe observing from Earth is dead long term if you drive innovation up and costs down with the observing systems and the supporting data transport networks.

TLDR How do we make decades of progress in years instead?

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

#143

Post by petschge »

toomuchtodo wrote: post #142
petschge wrote: post #133

Earlier quoted context omitted.

That was the LISA Pathfinder mission ( https://en.wikipedia.org/wiki/LISA_Pathfinder ), the preparatory step for a gravitational wave detector in space. And yes something like that could work eventually. Right now we are doing science on that concept. It takes a decade or three to get the technology mature enough that you can do astronomy with it.

In some StarLink thread on /r/spacex, someone was mentioning that you can't do IR/optical light interferometry without being able to measure the phase of light, and someone else said we're pretty close to being able to. If you're able to deploy orbital observatories with a StarLink sort of cadence (keep throwing up cheap satellites as quickly as possible), would you think we'd reach more mature observation tech faste…

Being able to iterate rapidly might be helpful to get tech of the ground into space once we have it. But right now even Earth-bound optical interferometry is in its infancy compared to optical astronomy and radio interferometry. It is an interesting subject of research for method development, but we are far away from an instrument that is sufficiently well understood to be useful.

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

#144

Post by mturmon »

topspin wrote: post #90
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.

This is a good comment. The deployment is eye catching, but the cryocooler was the high technical risk item.

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

#145

Post by mturmon »

maxxxxx wrote: post #57
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…

Agreed. I have talked to people at JPL and all their tools are completely outdated, they have no room for creativity and everything they do is constantly watched and reviewed. Unless you are way up in leadership this doesn’t seem much fun. Maybe it works at a startup where they try do something completely new but as soon as your stuff gets close to production it won’t be much fun.

This is an over generalization.

There’s a big range of agility at JPL depending on how close your work is to spacecraft operations. Here are two current job openings placed by good groups at JPL that many people here would find challenging and innovative —

https://jpl.jobs/jobs/2018-9779-Senior-Software-Engineer-Aut... (group webpage: https://ai.jpl.nasa.gov/)

https://jpl.jobs/jobs/2019-10706-Big-Data-Analytics-Software...

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

#146

Post by azernik »

falcrist wrote: post #88
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 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.

It does absolutely increase risk, which everyone in the industry recognizes - people talk about things like minimizing separation events as a tool for reducing risk. When you're stuck doing risky stuff like this, you can compensate pretty easily by throwing an enormous testing budget at the thing, which is a big part of the ballooning cost of JWST.

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

#147

Post by FrojoS »

sanxiyn wrote: post #49
NikolaeVarius wrote: post #21

Earlier quoted context omitted.

Huge difference is that Apollo had highly trained human beings on board to fix things that could not be planned for. There were also 10 previous missions to Apollo 11 to work out the kinks, with one failing with loss of life. JW is not designed to be fixed or fail, nor are there training runs. It HAS to work first shot.

Apollo is probably the wrong thing to compare with, but sky crane did work first shot.

You are right! Sky crane still blows my mind!

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

#148

Post by azernik »

java-man wrote: post #27

what puzzles me all the time is why not build two instead. it looks like the R&D portion of the budget might be greater than the actual manufacturing cost, so building two would be less than 2x the price. if one launch fails, we've got a backup. if both launch, we have two instruments deployed. why don't we do it??

Generally they do build two - one as a ground testbed for interpreting diagnostic data, trying to reproduce issues, and testing software changes/commands.

However, at the very low rates we're talking, everything is (damn near) hand-built. Economies of scale don't kick in until higher volumes.

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

#149

Post by maxxxxx »

mturmon wrote: post #145
maxxxxx wrote: post #57

Earlier quoted context omitted.

Agreed. I have talked to people at JPL and all their tools are completely outdated, they have no room for creativity and everything they do is constantly watched and reviewed. Unless you are way up in leadership this doesn’t seem much fun. Maybe it works at a startup where they try do something completely new but as soon as your stuff gets close to production it won’t be much fun.

This is an over generalization. There’s a big range of agility at JPL depending on how close your work is to spacecraft operations. Here are two current job openings placed by good groups at JPL that many people here would find challenging and innovative — https://jpl.jobs/jobs/2018-9779-Senior-Software-Engineer-Aut... (group webpage: https://ai.jpl.nasa.gov/ ) https://jpl.jobs/jobs/2019-10706-Big-Data-Analytics-Soft…

I think what they build doesn’t run on any probe but on Earth so the world doesn’t go under if they make mistakes . It’s the same in medical. The closer you get to the patient the more regulation you get.

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

#150

Post by dzhiurgis »

zanny wrote: post #84
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.

I had !remind me in 2 years setup for it. Didn't really know why, but figured out eventually by how long it's taking them.

Also - isn't the tech behind it is going to be obsolete pretty soon?

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