James Webb Space Telescope Launch Postponed(scitechdaily.com)
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James Webb Space Telescope Launch Postponed
https://scitechdaily.com/james-webb-space-telescope-launch-postponed-heres-why-and-the-new-launch-date/
33 comments
I still don't have faith in the absurd origami sun shield they've built. I think there is a very real chance it gets to its largange point and then runs into a problem deploying. They will spend months trying to fix it and finally give up around this time next year with all of that time and money pissed away.
At this stage I think it would have been faster, cheaper and lower risk to have either developed a launcher that could have fit it inside a fairing with a more conventional and less compact shield......Or would have been acceptable to take the performance hit to either stick this thing in Earth orbit so it could be serviced.....Or have given it a less effective but much safer and more conventional chassis so it could have gone to L2 without the massive risk of failure.
EDIT: I know that those alternatives would yield suboptimal results but you have to balance capability and cost with risk. JWST is 20 years in the making and very very expensive. This thing will only have an operational life of 10 years even if everything goes to plan. So under the best case it wont have the staying power and upgradability of Hubble unless someone figures out a cost effective way to get astronauts to L2 and back.
At this stage I think it would have been faster, cheaper and lower risk to have either developed a launcher that could have fit it inside a fairing with a more conventional and less compact shield......Or would have been acceptable to take the performance hit to either stick this thing in Earth orbit so it could be serviced.....Or have given it a less effective but much safer and more conventional chassis so it could have gone to L2 without the massive risk of failure.
EDIT: I know that those alternatives would yield suboptimal results but you have to balance capability and cost with risk. JWST is 20 years in the making and very very expensive. This thing will only have an operational life of 10 years even if everything goes to plan. So under the best case it wont have the staying power and upgradability of Hubble unless someone figures out a cost effective way to get astronauts to L2 and back.
> At this stage I think it would have been faster, cheaper and lower risk to have either developed a launcher that could have fit it inside a fairing with a more conventional and less compact shield...
They are, for a generous value of "they". For the cost of making this observatory fit on an Ariane 5, SpaceX is developing a 9-meter reusable launch system that can be run in a carbon-neutral fashion. It would still require folding, but nothing beyond conventional folding techniques that have been used since the 1970s.
They are, for a generous value of "they". For the cost of making this observatory fit on an Ariane 5, SpaceX is developing a 9-meter reusable launch system that can be run in a carbon-neutral fashion. It would still require folding, but nothing beyond conventional folding techniques that have been used since the 1970s.
By they I meant NASA, 20 years ago when the project was started. Yes Starship might be able to do that but by the time it was even conceived JWST was so far along there was no turning back.
Actually, would an RTG have fit the power requirements?
Others have explained how power is not the issue, but also RTGs are not a cure-all. This whole sunshade thing is necessary to shield the sensitive electronics from the heat and radiation of the sun - putting an active radiation source on board would present huge problems for the same reasons.
RTGs are also very heavy and do not generate much power; they are useful for the outer solar system because solar power is not viable there due to the inverse square law. At this distance from the sun, solar is a no-brainer.
RTGs are also very heavy and do not generate much power; they are useful for the outer solar system because solar power is not viable there due to the inverse square law. At this distance from the sun, solar is a no-brainer.
My understanding is the issue is not of limited power but limited in fuel for the RCS system. It uses those thrusters to aim the telescope. Once its out, it can no longer be controlled.
I meant a radioisotope thermoelectric generator. Much more dependable than a complicated solar panel fold out. (Otherwise solar panels are great just sounds like the deployment mechanism is suspect)
The foldy bit isn't a solar panel. Its a sun shade. Its job is to keep the telescope out of direct sunlight and help regulate temperature.
Normally, space telescopes will be built like Hubble or Spitzer where the mirrors are inside a cylinder which keeps light out from all directions except where the telescope is aimed. Its also insulated to keep heat from messing with measurements.
JWST's mirror is so large that they couldn't build it this way because no launcher existed at the time with a large enough payload fairing to fit it. So instead of a conventional, and otherwise superior in every other way, cylinder they came up with a clever origami folding sunshade. For comparison Hubble has a 2.4 meter main lens and JWST has a 6.5 meter lens. Its so large they couldn't reliably make it out of one element either so its actually several hexagonal elements put together. This is a popular technique for large telescopes.
For power JWST just has solar panels. L2 isn't that much farther from the sun than earth is so it gets sufficient power this way.
But unlike Hubble's reaction wheels JWST uses RCS thrusters to change its orientation. There are pros and cons. RCS is much more reliable than reaction wheels, a lot of satellites met a premature end because their reaction wheels stopped working. But RCS only lasts as long as you have fuel. They gave JWST enough for an estimated 10 years of operation.
Normally, space telescopes will be built like Hubble or Spitzer where the mirrors are inside a cylinder which keeps light out from all directions except where the telescope is aimed. Its also insulated to keep heat from messing with measurements.
JWST's mirror is so large that they couldn't build it this way because no launcher existed at the time with a large enough payload fairing to fit it. So instead of a conventional, and otherwise superior in every other way, cylinder they came up with a clever origami folding sunshade. For comparison Hubble has a 2.4 meter main lens and JWST has a 6.5 meter lens. Its so large they couldn't reliably make it out of one element either so its actually several hexagonal elements put together. This is a popular technique for large telescopes.
For power JWST just has solar panels. L2 isn't that much farther from the sun than earth is so it gets sufficient power this way.
But unlike Hubble's reaction wheels JWST uses RCS thrusters to change its orientation. There are pros and cons. RCS is much more reliable than reaction wheels, a lot of satellites met a premature end because their reaction wheels stopped working. But RCS only lasts as long as you have fuel. They gave JWST enough for an estimated 10 years of operation.
The thing folding out on JWST is not a solar panel. It is a heat shield that keeps all the detection equipment cold and completely shadowed from sunlight.
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Suggestion to append "to December 25" to the title.
I second it.
Specially because it is literally news from yesterday, already published in a better source: https://www.nasa.gov/feature/james-webb-space-telescope-laun...
Leaving the title as is may trick people into thinking it was postponed again.
Specially because it is literally news from yesterday, already published in a better source: https://www.nasa.gov/feature/james-webb-space-telescope-laun...
Leaving the title as is may trick people into thinking it was postponed again.
At this rate I half expect the telescope's rocket to collide with Santa Claus on ascent.
xkcd should do a comic about that....
At least the delays are decreasing.
Let's just hope the series converges.
Let's just hope the series converges.
Oh no, are we in Zeno's paradox, each time we halve current delay, but never reaching the launch
It could be worse. If nth delay is 1/n months, say, then the sum of delays is infinite.
Zeros paradox is at least just a paradox.
Zeros paradox is at least just a paradox.
As usual, there's an xkcd for that: https://xkcd.com/2014
This device represents so much hard work in pursuit of new technologies and new capabilities, it is absolutely worth taking an extra day or however many more to make sure things go correctly.
They've gone this long, hopefully there won't be Challenger type pressure on them to launch instead of waiting until conditions are right, even if that ends up being two weeks.
With how long this took and it’s expected lifetime, I wish it had been something like a pipeline for building these every 5 or X years that was built.
Sad to see it postponed but what is another day when it has been so many years waiting! :) Will be great to see it launch when it does
How long can we delay before they’ll need to take it off the rocket for inspection?
I stopped breathing until I reached the end of that headline
Never happened before, and now again!
The amount of delays is comical. Ofcourse the launch day itself would be subject to a few bad weather events. Lets hope for the best.
I’d be excited about it if it wasn’t taking this long. My friends and I were talking about this telescope in high school physics class in 2004.
The hype around the telescope is to the point of a down-on-his-luck divorced dad that consistently overpromises and underdelivers. (Remember that Sega Dreamcast I promised you when you were little for Christmas one year? Well, here it is now that you are all grown up.)
It’s an exaggeration, but I’ll believe it when I see it.