NASA - James Webb Space Telescope - Discussion and Updates

[speedevil]

the big question here is what happens if Webb turns out to be a Hubble...ie there is some flaw in it that makes it less "generational"

then what?

Much loud noises, fingerpointing, and little else.
It is if not impossible to service JWST - practically so, without getting it back to earth which would be expensive and damaging.
If it is impacted seriously enough, there would be a modest saving due to no operations budget.

[Blackstar]

https://asd.gsfc.nasa.gov/luvoir/resources/docs/LUVOIR_Interim_Report_Final.pdf

[redliox]

https://asd.gsfc.nasa.gov/luvoir/resources/docs/LUVOIR_Interim_Report_Final.pdf

Reading this; LUVOIR had my greatest interest out of the various post-Webb telescopes.

[Blackstar]

https://asd.gsfc.nasa.gov/luvoir/resources/docs/LUVOIR_Interim_Report_Final.pdf

Reading this; LUVOIR had my greatest interest out of the various post-Webb telescopes.

Wait until you see the cost estimate...

[TripleSeven]

the big question here is what happens if Webb turns out to be a Hubble...ie there is some flaw in it that makes it less "generational"

then what?

Much loud noises, fingerpointing, and little else.
It is if not impossible to service JWST - practically so, without getting it back to earth which would be expensive and damaging.
If it is impacted seriously enough, there would be a modest saving due to no operations budget.

a total failure will be catastrophic for the agency in my view

[Don2]

a total failure will be catastrophic for the agency in my view

That's why the ground tests are important. If the Hubble mirror problem had been found before flight then it could have been fixed, although it would have caused a major delay.

Why is JWST so expensive? A big reason is the cryogenic operating temperature. That requires beryllium rather than silicon carbide construction. Several telescopes were proposed for the last Discovery round, and proposals for 1.5 m room temperature telescopes cost about the same as 0.5 m cryogenic ones. The cryo requirement seems to boost the cost per unit mirror area by about tenfold.

However, JWST's ability to go far into the infra-red will be useful for looking at strongly red-shifted objects such as the first galaxies to from in the universe. JWST will do fantastic science if it works as intended.

[Don2]

Reading this; LUVOIR had my greatest interest out of the various post-Webb telescopes.

Wait until you see the cost estimate...

From telescope proposals in the last Discovery round, non cryogenic proposals seem to cost $250 million per square meter of mirror.

JWST is also about $250 million per square meter of mirror, although that is cryogenic.

At that rate LUVOIR-A will cost $44 billion. LUVOIR-B will cost $13 billion.

NASA needs to junk this study and look at flying $600 million to $1billion astrophysics missions. The Europeans had some good proposals in that price range. That would help to restore diversity to the program after JWST.

[RotoSequence]

Reading this; LUVOIR had my greatest interest out of the various post-Webb telescopes.

Wait until you see the cost estimate...

From telescope proposals in the last Discovery round, non cryogenic proposals seem to cost $250 million per square meter of mirror.

JWST is also about $250 million per square meter of mirror, although that is cryogenic.

At that rate LUVOIR-A will cost $44 billion. LUVOIR-B will cost $13 billion.

NASA needs to junk this study and look at flying $600 million to $1billion astrophysics missions. The Europeans had some good proposals in that price range. That would help to restore diversity to the program after JWST.

Who do we need to smack around for a while until they come up with a price tag per square meter that's even remotely acceptable? 

More seriously, I can't see anything in the LUVOIR-A class getting off the ground without halving that cost, at bare minimum.

[TripleSeven]

a total failure will be catastrophic for the agency in my view

That's why the ground tests are important. If the Hubble mirror problem had been found before flight then it could have been fixed, although it would have caused a major delay.

Why is JWST so expensive? A big reason is the cryogenic operating temperature. That requires beryllium rather than silicon carbide construction. Several telescopes were proposed for the last Discovery round, and proposals for 1.5 m room temperature telescopes cost about the same as 0.5 m cryogenic ones. The cryo requirement seems to boost the cost per unit mirror area by about tenfold.

However, JWST's ability to go far into the infra-red will be useful for looking at strongly red-shifted objects such as the first galaxies to from in the universe. JWST will do fantastic science if it works as intended.

I will bet money that the "parts" of the telescope are not even 1/3 maybe less of the price of the thing

[Jim]

It certainly had a role in making the design of the heatshiled more complex.

No, it didn't.  Any large IR telescope is going to large sunshield.

[Jim]

the big question here is what happens if Webb turns out to be a Hubble...ie there is some flaw in it that makes it less "generational"

then what?

Why should this be any different than risks for Cassini, PSP, MSL, Mars 2020, Messenger, Magellan, etc?   

[Jim]

I will bet money that the "parts" of the telescope are not even 1/3 maybe less of the price of the thing

The telescope and instruments are most of the cost.  The spacecraft would be less than 1/3.

[TripleSeven]

the big question here is what happens if Webb turns out to be a Hubble...ie there is some flaw in it that makes it less "generational"

then what?

Why should this be any different than risks for Cassini, PSP, MSL, Mars 2020, Messenger, Magellan, etc?

My suggestion is that 1) far more money has been invested, 2) the thing has had endless delays and management issues which each time are "solved" only the next year not to be and 3) none of those program/projects reflect the management issues that have dogged NASA in the past

[Jim]

My suggestion is that 1) far more money has been invested, 2) the thing has had endless delays and management issues which each time are "solved" only the next year not to be and 3) none of those program/projects reflect the management issues that have dogged NASA in the past

Most of them had their problems.  MSL was delayed 26 months.  Cassini went through a complete redesign. 

Hubble was only to cost 400 million and it ended up several billion by the time it launched.

[TrevorMonty]

the big question here is what happens if Webb turns out to be a Hubble...ie there is some flaw in it that makes it less "generational"

then what?

While not designed to be serviceable, I do wonder what is possible if it could be returned to LOP-G for investigation.

[speedevil]

It certainly had a role in making the design of the heatshiled more complex.

No, it didn't.  Any large IR telescope is going to large sunshield.

More complex, due to tighter folding in a smaller package, and a more constrained mass budget for that shield.

If you have to fit a five layer 21*14m shield in a fairing that can't cope with an unfolded mirror, you're pretty much going to have to spend lots of effort making the shield actually fit.

Of course a shield is needed, but the design is simplified greatly as you relax mass budgets and volume limits, or fairing constraints.

[Blackstar]

It certainly had a role in making the design of the heatshiled more complex.

No, it didn't.  Any large IR telescope is going to large sunshield.

More complex, due to tighter folding in a smaller package, and a more constrained mass budget for that shield.

If you have to fit a five layer 21*14m shield in a fairing that can't cope with an unfolded mirror, you're pretty much going to have to spend lots of effort making the shield actually fit.

Of course a shield is needed, but the design is simplified greatly as you relax mass budgets and volume limits, or fairing constraints.

Doesn't change most of the technologies needed for the mission:

1. near and
2. mid-infrared detectors,
3. sunshield materials,
4. microshutters
5. wavefront sensing and control.
6. lightweight cryogenic mirrors,
7. cryogenic detector readout application-specific integrated circuit,
8. cryogenic heat switches,
9. a cryocooler for the mid-infrared instrument,
10. a large precision cryogenic structure.

Source:

https://www.nasa.gov/vision/universe/starsgalaxies/webb_technologies.html

[speedevil]

Of course a shield is needed, but the design is simplified greatly as you relax mass budgets and volume limits, or fairing constraints.

Doesn't change most of the technologies needed for the mission:

1. near and
2. mid-infrared detectors,
3. sunshield materials,
4. microshutters
5. wavefront sensing and control.
6. lightweight cryogenic mirrors,
7. cryogenic detector readout application-specific integrated circuit,
8. cryogenic heat switches,
9. a cryocooler for the mid-infrared instrument,
10. a large precision cryogenic structure.

Source:

https://www.nasa.gov/vision/universe/starsgalaxies/webb_technologies.html

The shield is simplified, I was imprecise, the remainder of the craft remains complex, I was attempting to keep it succinct.
If you remove the folding mirror, then the sunshade gets less complex, because it can obviously fit into the fairing better, if the mirror can.

Some aspects of wavelength sensing and control (the mirror positioning related ones) are reduced. This whole field is undergoing a revolution in terms of design of adaptive optics and similar components, driven by searching for exoplanets - reducing distortions to retain massive contrast required.

Moving away from strictly 'what if the mirror wasn't folded', and onto a larger mass budget.

The cryogenic heat switches, lightweight precision mirror, and sunshade materials for example would obviously become easier if you further relaxed the mass budget and were able to launch it in a larger fairing. The cryocooler is hard for vibration reasons, and power use, as I gather, both of which could be ameliorated by a larger mass budget.
Many aspects do not change.

[jbenton]

Reading this; LUVOIR had my greatest interest out of the various post-Webb telescopes.

Wait until you see the cost estimate...

From telescope proposals in the last Discovery round, non cryogenic proposals seem to cost $250 million per square meter of mirror.

JWST is also about $250 million per square meter of mirror, although that is cryogenic.

At that rate LUVOIR-A will cost $44 billion. LUVOIR-B will cost $13 billion.

NASA needs to junk this study and look at flying $600 million to $1billion astrophysics missions. The Europeans had some good proposals in that price range. That would help to restore diversity to the program after JWST.

Who do we need to smack around for a while until they come up with a price tag per square meter that's even remotely acceptable? 

More seriously, I can't see anything in the LUVOIR-A class getting off the ground without halving that cost, at bare minimum.

Perhaps either one of these technologies could help:

https://phys.org/news/2017-09-mirror-coating-technology-telescopes.html
https://www.nasa.gov/feature/goddard/2016/nasa-eyes-first-ever-carbon-nanotube-mirrors-for-cubesat-telescope

Also in the 2030s-2040s timeline, at least one of the following rockets (or its successor) should be available
-BFR/BFS
-SLS
-New Armstrong
With their 8m fairings, they could allow for bigger mirrors with less oragami, if that helps.
https://www.teslarati.com/nasa-spacex-bfr-study-space-telescope-luvoir/

[jbenton]

what got Webb was "too much" new technology (this is a theme song today...the Dreamliner, Ford CVN, F35 etc have all been snake bit by this) ....but no new technology to me is just as bad

Was it really "too much technology" that made JWST capsize like a clown in a circus?
I haven't followed it for long at all, but in these days it is the simple standard low tech stuff that fails. Northrup-Grumman fails to deliver what they have delivered to hundreds of working satellites in orbit. The space craft bus. Their thrusters leak after having been treated by abrasive chemicals. Their washers fall off in the standard vibration test and disappears into somewhere the rest of the spacecraft. They cannot even unfold their umbrella during the very last test without tearing it up and getting it stuck. What has N-G been doing with all their billions all of these years??? I cannot imagine any alternative to blatant corruption and an attempt to charge the tax payers for incompetence.

the failure on Galileo with the antenna was not a technology failure (as the TDRSS and "other" satellites have used that antenna) but with managing the technology, particularly in the endless "road" trips.

Didn't Galileo's antenna fail to unfold because it was delayed for several years (after a Shuttle disaster)? A stay in the storage that caused the lubrication of the unfolding mechanism to evaporate or change its properties. I remember reading something to that effect in the analysis following the failure. So every delay of the JWST sounds to me like a JWST even more prone to failures.

well NG management coupled with NASA is well near incompetent on the Webb...a failure from the start

the folks who built the LM and a great stretch of Naval fighters including my old ride...are long gone

Galileo's antenna failed for two maybe three reasons.  First it was transported several times across the country where the lubricant on it suffered our bumpy roads and I dont think that they ever inspected the lubricant again.  2) storage might have made that worse...and then there was a sunshield...but I would bet all the engineering and amateur radio creds I have that the first one did it

the antennas have worked flawlessly on a lot of TDRSS and well some other satellites as well.

there is nothing wrong with the design... and it only "weighs" 50 pounds...

if it had been on Cassini it would have changed the data time enormously

This interesting conversation started up on the Ice Giants' thread ( I mentioned JWST on that non-astronomy thread first, my fault )

I saw an ad for NG on SpaceNews awhile back just before the SMAP mission launched. It was advertising NG's experence with large-scale in-space deployments, claiming that after scores of deployments, not one that they built has failed (biased source, I know). So, I was just wondering, is there any company other than NG with the experience required to perform a JWST-like mission for NASA? If NASA were to go for LUVOIR or Origins sometime in the future, who would they ask?