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Tugger
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James Webb Space Telescope has a launch date: Dec 18 2021

Wed Sep 08, 2021 7:48 pm

Wow, here's a topic i was thinking might never get restarted!
Now over a decade late and with a $10,000,000,000.00 price tag.

https://arstechnica.com/science/2021/09 ... unch-date/
myriad technical problems have delayed Webb's development over the last decade, leading to enormous cost overruns. Some of this is understandable, as unfurling the 20-meter-long telescope in deep space requires 50 major deployments and 178 major release mechanisms. All of these systems must work or the instrument will fail. There is no easy means of servicing the telescope at its location near a Sun-Earth LaGrange point 1.5 million km from Earth, or four times the distance to the Moon.


Can't wait to see it finally reach the skies it is to gaze into!

Image

Image

More on it:
https://en.wikipedia.org/wiki/James_Web ... _Telescope

Tugg
 
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Dutchy
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Re: James Webb Space Telescope has a launch date: Dec 18 2021

Wed Sep 08, 2021 8:24 pm

will be off the planet in December right? Indeed can't wait for the first results. Hopefully, it will work, because there will be no mission to repair it, way to far out. Fingers crossed.
 
estorilm
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Re: James Webb Space Telescope has a launch date: Dec 18 2021

Wed Sep 08, 2021 8:34 pm

Very interesting, but I was completely unaware that this was going to be launched by an Ariane 5..... why? I'm guessing something to do with its launch profile/location, and yes I know it's a joint ESA project, but... wouldn't an Atlas V offer similar performance with increased reliability? I guess the Ariane is fine, but it's tough to beat 100%.
 
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Tugger
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Re: James Webb Space Telescope has a launch date: Dec 18 2021

Wed Sep 08, 2021 8:57 pm

estorilm wrote:
Very interesting, but I was completely unaware that this was going to be launched by an Ariane 5..... why? I'm guessing something to do with its launch profile/location, and yes I know it's a joint ESA project, but... wouldn't an Atlas V offer similar performance with increased reliability? I guess the Ariane is fine, but it's tough to beat 100%.

The launch was part of ESA's contribution to the project.

Tugg
 
Newark727
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Re: James Webb Space Telescope has a launch date: Dec 18 2021

Wed Sep 08, 2021 9:00 pm

Hubble inspired a whole generation of scientists... hopefully we'll get a generation more from the Webb telescope's images.
 
mxaxai
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Re: James Webb Space Telescope has a launch date: Dec 18 2021

Wed Sep 08, 2021 10:09 pm

estorilm wrote:
Very interesting, but I was completely unaware that this was going to be launched by an Ariane 5..... why? I'm guessing something to do with its launch profile/location, and yes I know it's a joint ESA project, but... wouldn't an Atlas V offer similar performance with increased reliability? I guess the Ariane is fine, but it's tough to beat 100%.

Money.

ESA wants access to the telescope but doesn't have much to offer for the spacecraft itself. So they're paying for the launch. Also, the Ariane 5 has become pretty reliable.
 
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Tugger
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Re: James Webb Space Telescope has a launch date: Dec 18 2021

Wed Sep 08, 2021 10:30 pm

mxaxai wrote:
Also, the Ariane 5 has become pretty reliable.

There are going to be quite a few puckered sphincters in ESA the day it launches... :pray:

Tugg
 
ZaphodHarkonnen
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Re: James Webb Space Telescope has a launch date: Dec 18 2021

Thu Sep 09, 2021 3:34 am

Tugger wrote:
mxaxai wrote:
Also, the Ariane 5 has become pretty reliable.

There are going to be quite a few puckered sphincters in ESA the day it launches... :pray:

Tugg


There are going to be hundreds, if not thousands, of very well toned asses from the clenching should it get to and pass its first light tests. There is a boggling number of critical things that could go wrong and basically scupper the entire project.

I wish the team luck.
 
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bikerthai
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Re: James Webb Space Telescope has a launch date: Dec 18 2021

Thu Sep 09, 2021 2:58 pm

Remember Hubble with the warped lense? The puckering won't stop until after the first few observations are verified and calibrated.

bt
 
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Tugger
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Re: James Webb Space Telescope has a launch date: Dec 18 2021

Thu Sep 09, 2021 3:23 pm

bikerthai wrote:
Remember Hubble with the warped lense? The puckering won't stop until after the first few observations are verified and calibrated.

bt

Not a warped lens, rather a "Spherical Aberration"... Heck of a read: https://spaceflightnow.com/2015/04/23/f ... ry-vision/

I definitely wish JWST a successful mission and will, like everyone, be waiting for that "first light" image. All the other "science" and spectro-wavelength-emission-sublimation-whatever stuff is great and may be perfect, but we humans want pictures! :biggrin:

Tugg
 
texl1649
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Re: James Webb Space Telescope has a launch date: Dec 18 2021

Thu Sep 09, 2021 6:03 pm

Tugger wrote:
mxaxai wrote:
Also, the Ariane 5 has become pretty reliable.

There are going to be quite a few puckered sphincters in ESA the day it launches... :pray:

Tugg


I think it bears noting how the launch itself is…almost the easiest/safest part of this launch. It is a quite complicated deployment. But don’t take my word for it, take the NASA science chief;

https://arstechnica.com/science/2021/08 ... bout-webb/

For most missions, launch contributes the majority of mission risk," explained Thomas Zurbuchen, the associate administrator for science missions at NASA. "If the spacecraft is in space, most risk is behind us."

However, there are exceptions to this rule, Zurbuchen explained in a new blog post for the space agency. For the Mars Perseverance mission launched last summer, for example, only about 10 to 20 percent of the mission's risk was retired once the spacecraft reached orbit. The remainder lay ahead of the vehicle, particularly with its daring landing on Mars, and then performing a technically challenging sample acquisition and analysis.

The $10 billion James Webb Space Telescope, due to launch on a European Ariane 5 rocket late this year, offers an even more extreme example. In his blog post, Zurbuchen offers a frank and revealing analysis of Webb's launch and assessment of the risks.

Once in space, Webb will need to travel about 1.5 million km from Earth to the L2 Lagrange Point beyond the Moon where it will be able to maintain a stable position without using much on-board propulsion. Along the way, and once there, some 50 deployments of the large, folded-up telescope will be necessary to prepare for scientific observations. This process will involve nearly 350 single-point failures, and if something goes wrong, it would scuttle the deployment without hope of repair. The number of single-point failures for Webb, by comparison, is a factor of three greater than the seven-minute landing of Perseverance on Mars.

It will take about three weeks to deploy Webb, and scientists will be on edge the entire time, Zurbuchen said.

"Those who are not worried or even terrified about this are not understanding what we are trying to do," Zurbuchen wrote. "We have worked hard to build the team for this task and it has been a tough journey at times. This mission has a very troubled story with chapters that were disappointing, or even baffling. We are where we are because Webb has some of the best engineers and leaders I have ever met, and they have continued when others were ready to give up."
 
ZaphodHarkonnen
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Re: James Webb Space Telescope has a launch date: Dec 18 2021

Thu Sep 09, 2021 9:34 pm

The biggest positive of a failure is that with the new generation of heavy lift vehicles coming online like Superheavy/Starship and Vulcan. Launching a replacement would require just building a new scope. Possibly with less fiddly bits due to the bigger fairings available.
 
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bikerthai
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Re: James Webb Space Telescope has a launch date: Dec 18 2021

Thu Sep 09, 2021 9:39 pm

ZaphodHarkonnen wrote:
Launching a replacement would require just building a new scope.


Building a new scope may not as easy as you say. Specifically, I doubt that any of the computer chips used would still be available. Unless they stash an extra set as backup.

bt
 
mxaxai
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Re: James Webb Space Telescope has a launch date: Dec 18 2021

Thu Sep 09, 2021 10:16 pm

bikerthai wrote:
ZaphodHarkonnen wrote:
Launching a replacement would require just building a new scope.


Building a new scope may not as easy as you say. Specifically, I doubt that any of the computer chips used would still be available. Unless they stash an extra set as backup.

bt

I would assume that the engineering / qualification models are still around. Knowing other NASA missions, they should have at least one complete second set of the electronics for tests on the ground, even after launch.
 
texl1649
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Re: James Webb Space Telescope has a launch date: Dec 18 2021

Fri Sep 10, 2021 10:11 am

mxaxai wrote:
bikerthai wrote:
ZaphodHarkonnen wrote:
Launching a replacement would require just building a new scope.


Building a new scope may not as easy as you say. Specifically, I doubt that any of the computer chips used would still be available. Unless they stash an extra set as backup.

bt

I would assume that the engineering / qualification models are still around. Knowing other NASA missions, they should have at least one complete second set of the electronics for tests on the ground, even after launch.


LOL, knowing NASA it would take 10 to 15 years to validate/budget/contract/execute such a plan.
 
tommy1808
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Re: James Webb Space Telescope has a launch date: Dec 18 2021

Fri Sep 10, 2021 3:12 pm

Tugger wrote:
estorilm wrote:
Very interesting, but I was completely unaware that this was going to be launched by an Ariane 5..... why? I'm guessing something to do with its launch profile/location, and yes I know it's a joint ESA project, but... wouldn't an Atlas V offer similar performance with increased reliability? I guess the Ariane is fine, but it's tough to beat 100%.

The launch was part of ESA's contribution to the project.

Tugg


Paper exercise essentially since NASA can not pay non-US lunch providers to launch payload paid for full or in part by the US taxpayer.

Best regards
Thimas
 
bajs11
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Re: James Webb Space Telescope has a launch date: Dec 18 2021

Sat Sep 11, 2021 8:03 am

tommy1808 wrote:
Tugger wrote:
estorilm wrote:
Very interesting, but I was completely unaware that this was going to be launched by an Ariane 5..... why? I'm guessing something to do with its launch profile/location, and yes I know it's a joint ESA project, but... wouldn't an Atlas V offer similar performance with increased reliability? I guess the Ariane is fine, but it's tough to beat 100%.

The launch was part of ESA's contribution to the project.

Tugg


Paper exercise essentially since NASA can not pay non-US lunch providers to launch payload paid for full or in part by the US taxpayer.

Best regards
Thimas


https://www.cnbc.com/2019/11/19/nasa-co ... soyuz.html
the cost per astronaut for flying with the Russians has steadily climbed, with the most recent contracts coming out to $86 million per astronaut.
 
tommy1808
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Re: James Webb Space Telescope has a launch date: Dec 18 2021

Sun Sep 12, 2021 5:05 am

bajs11 wrote:
tommy1808 wrote:
Tugger wrote:
The launch was part of ESA's contribution to the project.

Tugg


Paper exercise essentially since NASA can not pay non-US lunch providers to launch payload paid for full or in part by the US taxpayer.

Best regards
Thimas


https://www.cnbc.com/2019/11/19/nasa-co ... soyuz.html
the cost per astronaut for flying with the Russians has steadily climbed, with the most recent contracts coming out to $86 million per astronaut.


I wouldn't consider astronauts payload, but NASA needs a waiver from Congress to pay for Soyus.

Best regards
Thomas
 
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Francoflier
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Re: James Webb Space Telescope has a launch date: Dec 18 2021

Tue Oct 19, 2021 6:23 am

The JWST is on the final stretch before launch. It has arrived in French Guiana and is being readied to leave Earth in December:

https://www.bbc.com/news/science-environment-58960575

I thought it might be shipped by air, but it seems it sailed there instead.
 
texl1649
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Re: James Webb Space Telescope has a launch date: Dec 18 2021

Tue Oct 19, 2021 2:13 pm

Really hope this goes smoothly. Incredible project, we all I believe realize the launch/getting it deployed at the Lagrange point is exceptionally complicated, with the booster phase a relatively low risk part of the sequence.
 
ThePointblank
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Re: James Webb Space Telescope has a launch date: Dec 18 2021

Mon Nov 22, 2021 11:27 pm

And it appears that the James Webb Space telescope is cursed, as the launch date has slipped to no earlier than December 22 due to the need for additional testing after a clamp that secures the spacecraft to its rocket adapter suddenly released sending vibrations throughout the observatory:

https://blogs.nasa.gov/webb/2021/11/22/ ... pe-launch/

The launch readiness date for the James Webb Space Telescope is moving to no earlier than Dec. 22 to allow for additional testing of the observatory, following a recent incident that occurred during Webb’s launch preparations.

The incident occurred during operations at the satellite preparation facility in Kourou, French Guiana, performed under Arianespace overall responsibility. Technicians were preparing to attach Webb to the launch vehicle adapter, which is used to integrate the observatory with the upper stage of the Ariane 5 rocket. A sudden, unplanned release of a clamp band – which secures Webb to the launch vehicle adapter – caused a vibration throughout the observatory.

A NASA-led anomaly review board was immediately convened to investigate and instituted additional testing to determine with certainty the incident did not damage any components. NASA and its mission partners will provide an update when the testing is completed at the end of this week.

Webb was previously scheduled to launch Dec. 18 on an Arianespace Ariane 5 rocket from Kourou.

The Webb Space Telescope is an international partnership with the European and Canadian space agencies. It will explore every phase of cosmic history – from within our solar system to the most distant observable galaxies in the early universe, and everything in between. Webb will reveal new and unexpected discoveries, and help humanity understand the origins of the universe and our place in it.


Poll time everyone! Who else thinks the launch date is going to slip even further?
 
744SPX
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Re: James Webb Space Telescope has a launch date: Dec 18 2021

Tue Nov 23, 2021 12:31 am

Further slippage would be in keeping with the program as a whole.
 
ZaphodHarkonnen
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Re: James Webb Space Telescope has a launch date: Dec 18 2021

Tue Nov 23, 2021 1:31 am

 
zanl188
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Re: James Webb Space Telescope has a launch date: Dec 18 2021

Tue Nov 23, 2021 12:37 pm

744SPX wrote:
Further slippage would be in keeping with the program as a whole.


Better a launch delay if it reduces the risk of the spacecraft not functioning as intended. No in flight repairs or second chances with this spacecraft.
 
wingman
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Re: James Webb Space Telescope has a launch date: Dec 18 2021

Tue Nov 23, 2021 3:25 pm

This stuff is way beyond my scope of knowledge but one comment in the Ars article asks how worried they'll be about launch vibration if they're this worried about vibration in the loading process. Probably "very" is the answer. To me the real question is what the price point difference is between the telescope and the failed clamp. The little things..
 
TangoandCash
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Re: James Webb Space Telescope has a launch date: Dec 18 2021

Tue Nov 23, 2021 4:15 pm

"there are more than 300 single points of failure aboard" https://arstechnica.com/science/2021/11 ... -occurred/

Do the bookies in Las Vegas have odds on whether this will all work as designed once launched?
 
meecrob
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Re: James Webb Space Telescope has a launch date: Dec 18 2021

Tue Nov 23, 2021 7:24 pm

wingman wrote:
This stuff is way beyond my scope of knowledge but one comment in the Ars article asks how worried they'll be about launch vibration if they're this worried about vibration in the loading process. Probably "very" is the answer. To me the real question is what the price point difference is between the telescope and the failed clamp. The little things..


The article states that the clamp that is used to secure the JWST had an uncommanded release that caused vibrations. The satellite was not attached. Also, to assume that in the intervening time between contract in 1996 and now, NOBODY thought to figure out if the satellite can handle the vibration is kinda selling those engineers short. Some enthusiast commenting on Ars Technica knows better than hundreds of NASA engineers, right...

Chances are there is a line or 10,000 of code that need to be debugged with regards to the release script of that clamp.

Edit: 300 points of failure? I check 300 points on a walkaround of a bugsmasher Cessna. I know those aren't all points of failure, but the majority are engine and flight controls...so to me this sounds pretty un-complicated for the mission this craft is designed to do.
 
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Francoflier
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Re: James Webb Space Telescope has a launch date: Dec 18 2021

Fri Nov 26, 2021 4:00 am

We can all breathe again... No boo-boo.

https://spacenews.com/jwst-undamaged-fr ... -incident/

Launch's back on. December 22nd.
 
texl1649
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Re: James Webb Space Telescope has a launch date: Dec 18 2021

Fri Nov 26, 2021 2:36 pm

meecrob wrote:
wingman wrote:
This stuff is way beyond my scope of knowledge but one comment in the Ars article asks how worried they'll be about launch vibration if they're this worried about vibration in the loading process. Probably "very" is the answer. To me the real question is what the price point difference is between the telescope and the failed clamp. The little things..


The article states that the clamp that is used to secure the JWST had an uncommanded release that caused vibrations. The satellite was not attached. Also, to assume that in the intervening time between contract in 1996 and now, NOBODY thought to figure out if the satellite can handle the vibration is kinda selling those engineers short. Some enthusiast commenting on Ars Technica knows better than hundreds of NASA engineers, right...

Chances are there is a line or 10,000 of code that need to be debugged with regards to the release script of that clamp.

Edit: 300 points of failure? I check 300 points on a walkaround of a bugsmasher Cessna. I know those aren't all points of failure, but the majority are engine and flight controls...so to me this sounds pretty un-complicated for the mission this craft is designed to do.


I think Berger (uncharacteristically) mis-stated the 300 points of failure in that article. There are 300 single points of failure in the deployment to orbit, not within the satellite itself. The issue as I understand it is the challenge not of launching smoothly (Ariane 5 is great), but but the many steps to reach/deploy in this incredible position.

About 28 minutes after liftoff, Webb will detach from its launch vehicle and begin "the most complex sequence of deployments ever attempted in a single space mission," according to NASA. This deployment, which will see Webb unfold and unfurl its sun shield once in space, includes quite literally hundreds of "single points of failure," Mike Menzel, Webb lead mission systems engineer for NASA's Goddard Space Flight Center in Maryland, said Tuesday (Nov. 2) during a news briefing.

344 points of failure
"There are 344 single-point-of-failure items on average," Menzel said about the Webb mission, adding that "approximately 80% of those are associated with the deployment … It's hard to avoid when you have a release mechanism. It's hard to put full redundancy into that."

Webb has 144 release mechanisms "which all must work perfectly," Krystal Puga, Webb spacecraft systems engineer for Northrop Grumman, which built the spacecraft, said during the briefing.

"Like an origami object, proper folding and unfolding is necessary in order to achieve a specific shape," Alphonso Steward, Webb deployment systems lead for NASA Goddard, said during the briefing.

Menzel explained that the team decreased the number of release mechanisms as much as possible. "We found the sweet spot between getting the control that we want, with these large flexible membranes," without adding too many single points of failure, he said.

However, while the mission, and especially the deployment stage, have such a large number of single points of failure, Menzel emphasized the extensive work that the mission team has done to ensure success. "When we identify a single point failure, we give it very special treatment. We have what we call a critical item control plan, and we always throw in extra inspection points. And we've done extra offline testing on these devices," Menzel said.

He added that for every one of these items identified, NASA and Northrop Grumman have done extra inspections and tests to understand the different ways that it could fail, to be as prepared as possible. "We've given our single-point-failure items a lot of attention," he said.


Anyway, yes, backup plans are also involved in many of those, and have been a real part of the delays. More at the link;

https://www.space.com/james-webb-space- ... of-failure
 
IFlyVeryLittle
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Re: James Webb Space Telescope has a launch date: Dec 18 2021

Mon Nov 29, 2021 3:32 pm

Im sure i read somewhere years ago that the vehicle was never designed to be in earth's gravity this long, and some components had to be swapped out because gravity had rendered them outside of the design envelope. Or am I imagining this?
 
ThePointblank
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Re: James Webb Space Telescope has a launch date: Dec 18 2021

Wed Dec 15, 2021 12:39 am

Francoflier wrote:
We can all breathe again... No boo-boo.

https://spacenews.com/jwst-undamaged-fr ... -incident/

Launch's back on. December 22nd.

Launch has been delayed again, to the 24th due to a electrical interface issue:

https://twitter.com/cbs_spacenews/statu ... 7503396868

Ariane5/JWST: Launch of the James Webb Space Telescope atop an ESA Ariane 5 rocket from French Guiana is being delayed, from 12/22 to no earlier than 12/24, because of an issue seen during an electrical interface test between the rocket and the payload
 
zanl188
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Re: James Webb Space Telescope has a launch date: Dec 18 2021

Sun Dec 19, 2021 3:36 pm

In hindsight…. Given SpaceX’s, and NASA’s, emerging capabilities will it prove to be an error that JWST is not inflight serviceable? Or not equipped with berthing capability for a propulsion module?
 
GDB
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Re: James Webb Space Telescope has a launch date: Dec 18 2021

Sun Dec 19, 2021 6:12 pm

zanl188 wrote:
In hindsight…. Given SpaceX’s, and NASA’s, emerging capabilities will it prove to be an error that JWST is not inflight serviceable? Or not equipped with berthing capability for a propulsion module?


There is a docking port, for what kind of spacecraft I don't know, in extreme situations an Orion with attached module?
However the JWST has a limited life, around a decade, due to the station keeping and various expendables such as coolant etc, it's not like the Hubble at all not just in terms of what optics it uses or orbit.
 
zanl188
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Re: James Webb Space Telescope has a launch date: Dec 18 2021

Sun Dec 19, 2021 8:28 pm

GDB wrote:

There is a docking port, for what kind of spacecraft I don't know, in extreme situations an Orion with attached module?
However the JWST has a limited life, around a decade, due to the station keeping and various expendables such as coolant etc, it's not like the Hubble at all not just in terms of what optics it uses or orbit.


I did not know that, thank you. So there’s hope for a refueling mission. I understand fuel is the life limiting item, as coolant is recycled.

A propulsion module would seem to be a relatively inexpensive way to extend a $10B mission.
 
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N14AZ
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Re: James Webb Space Telescope has a launch date: Dec 18 2021

Mon Dec 20, 2021 8:45 pm

I have a question about Webb’s orbit around the Lagrange point no. 2 and maybe someone can explain this to me in simple words. What I simply do not get is how can Webb circle around this point. I mean, spacecrafts can orbit around planets and so on. But how does it work in case of L2, which does not have any mass.

Forgive me my ignorance. Should have been more careful during my physics lessons…

Image
Source: https://webbtelescope.org/contents/medi ... 4180-Image
 
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SeamanBeaumont
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Re: James Webb Space Telescope has a launch date: Dec 18 2021

Mon Dec 20, 2021 10:39 pm

N14AZ wrote:
I have a question about Webb’s orbit around the Lagrange point no. 2 and maybe someone can explain this to me in simple words. What I simply do not get is how can Webb circle around this point. I mean, spacecrafts can orbit around planets and so on. But how does it work in case of L2, which does not have any mass.

Forgive me my ignorance. Should have been more careful during my physics lessons…

Source: https://webbtelescope.org/contents/medi ... 4180-Image

The points are not string enough to be stable. NASA refers to themn as metastable...

It is easy for an object (like a spacecraft) at one of these five points to stay in place relative to the other two bodies (e.g., the Sun and the Earth). In fact, L4 and L5 are stable in that objects there will orbit L4 and L5 with no assistance. Some small asteroids are known to be orbiting the Sun-Earth L4 and L5 points. However, L1, L2, and L3 are metastable so objects around these points slowly drift away into their own orbits around the Sun unless they maintain their positions, for example by using small periodic rocket thrust. This is why L1, L2, and L3 don't "collect" objects like L4 and L5 do.

https://webb.nasa.gov/content/about/orbit.html

Objects that want to stay at L2, or L1 and L3, need to correct and hence why they need thrusters to maintain that position. Expect the orbit chosen minimises thruster use to extend the life of the spacecraft.
 
Catfry
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Re: James Webb Space Telescope has a launch date: Dec 18 2021

Tue Dec 21, 2021 7:53 am

This video by Scott Manley is a good explanation. There are some nice visualizations at around 5:55: https://youtu.be/7PHvDj4TDfM?t=354

The velocity you need to stay in orbit depends on your distance to the gravitational well. Satellites in low orbit are very fast, while geostationary orbits take 24 hours to complete. the moon is slower still. At the same time the necessary velocity also depends on the mass of the orbited object. The greater the mass, the faster you need to go to maintain orbit.

A satellite at L2 is in orbit around the sun, about 15 million km further out than the earth, and you would think it would take more than a year to complete an orbit.
In reality, at this special point the gravity from the sun and the Earth combine to act as a heavier body, and this means that the orbital period here is faster than you would expect at that sun distance, and it is actually the same orbital period as the Earths.

As for why JWST need to circle around the L2 point itself I don't really know, all I know is that this is common for other observatories sent here. And not only circular movements, some have moved in a figure of eight.
 
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flyingturtle
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Re: James Webb Space Telescope has a launch date: Dec 18 2021

Tue Dec 21, 2021 9:54 am

My favorite explanation of Lagrange points is simply "Physicists hated the popularity of Kerbal Space Program, and so they invented Lagrange points and the three-body problem."

Catfry wrote:

As for why JWST need to circle around the L2 point itself I don't really know, all I know is that this is common for other observatories sent here. And not only circular movements, some have moved in a figure of eight.


I guess there are stable Lagrange points. Spacecraft can orbit around them in a stable way. Metastable Lagrange points need small corrections all the time.
 
Catfry
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Re: James Webb Space Telescope has a launch date: Dec 18 2021

Tue Dec 21, 2021 10:53 am

as SeamanBeaumonts comment says, an orbit around L2 is semistable. you need corrective periodic thrusts. Even though JWST will orbit it isn't stable long term. So I don't really know why it needs to move in a circular pattern at all.
 
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speedygonzales
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Re: James Webb Space Telescope has a launch date: Dec 18 2021

Tue Dec 21, 2021 11:44 am

Catfry wrote:
as SeamanBeaumonts comment says, an orbit around L2 is semistable. you need corrective periodic thrusts. Even though JWST will orbit it isn't stable long term. So I don't really know why it needs to move in a circular pattern at all.

These orbits are more stable than sitting still, so less fuel will be needed for station keeping. There are also several other observatories at L2, so they can't all sit at the exact spot.
 
zanl188
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Re: James Webb Space Telescope has a launch date: Dec 18 2021

Tue Dec 21, 2021 12:39 pm

N14AZ wrote:
I have a question about Webb’s orbit around the Lagrange point no. 2 and maybe someone can explain this to me in simple words. What I simply do not get is how can Webb circle around this point. I mean, spacecrafts can orbit around planets and so on. But how does it work in case of L2, which does not have any mass.



Depends upon your frame of reference. Since JWST is really just orbiting the sun think of “orbiting the Lagrange point” as irregularities in its orbit around the sun. Sometimes a little higher, sometimes a little lower, etc. Much easier to visualize that way.

Other nearby masses will perturb the orbit occasionally….
 
zanl188
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Re: James Webb Space Telescope has a launch date: Dec 18 2021

Tue Dec 21, 2021 12:46 pm

Catfry wrote:
As for why JWST need to circle around the L2 point itself I don't really know, all I know is that this is common for other observatories sent here. And not only circular movements, some have moved in a figure of eight.


JWSTs Lagrange point puts the earth between the sun and the spacecraft. This reduces the thermal load on the spacecraft and aids cooling of the infrared telescope.
 
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flyingturtle
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Re: James Webb Space Telescope has a launch date: Dec 18 2021

Tue Dec 21, 2021 4:49 pm

I'm already looking for WiFi options in order to watch the launch in spite of a family Christmas dinner.

About hundred years ago, there was the so-called Great Debate whether our galaxy was the only one, and as a consequence, whether our galaxy was the entire universe.

Then came Edwin Hubble who had access to the new 100 inch (2.5 meter) Hooker telescope, and answered that question. The way we've viewed our universe evolved in unison with developments in telescope manufacturing.

I'm eagerly looking forward to the discoveries made with the JWST.
 
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N14AZ
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Re: James Webb Space Telescope has a launch date: Dec 18 2021

Wed Dec 22, 2021 8:22 am

Thank you all for your feedback!

Seems as if the launch date has been postponed by one day, due to the expected weather on December 24.
Source: https://www.aero.de/news-41559/Hubble-N ... -fest.html
 
mxaxai
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Re: James Webb Space Telescope has a launch date: Dec 18 2021

Wed Dec 22, 2021 1:52 pm

Catfry wrote:
As for why JWST need to circle around the L2 point itself I don't really know, all I know is that this is common for other observatories sent here. And not only circular movements, some have moved in a figure of eight.

Halo orbits are solutions to the three-body-problem similar to the Lagrange points. JWST is principally in orbit around the sun, although this orbit is perturbed by Earth's gravity - three bodies in total. Halo orbits are specific solutions that satisfy two constraints:
1. The orbital period around the sun is identical to Earth's - this is also true for the L2 point itself.
2. The path in a rotating system (i. e. when looking at the L2 point from earth) resembles a periodic orbit around the L2 point.
Note that halo orbits generally aren't elliptic but more of a 3D kidney-shape.

There are other solutions that may look like a figure of eight, or a Lissajous pattern, or orbits that lie entirely in the orbital plane (Lyapunov orbits) but halo orbits are often preferable for operational reasons. Halo orbits are also slightly more stable.
You can even create paths that go from one Lagrange point to another (and back again) without using much if any fuel.
Image
Source: https://www.researchgate.net/publicatio ... int_Orbits

This video illustrates how the halo orbit becomes invisible when viewed from an inertial system: https://youtu.be/IyyQqaF4tNY
Instead, it looks like a slightly wobbly orbit around the sun; this wobbling is the result of Earth's influence. You can't just ignore the Earth and the Sun and pretend as if JWST is orbiting around 'nothing' because the entire thing only works because both celestial bodies are there. (Unlike orbits around a single body, like LEO orbits, where the influence of the sun is negligible). This also makes them relatively susceptible to perturbations from other bodies, like Jupiter, so stationkeeping is required.
 
zuckie13
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Re: James Webb Space Telescope has a launch date: Dec 18 2021

Fri Dec 24, 2021 7:37 pm

zanl188 wrote:
Catfry wrote:
As for why JWST need to circle around the L2 point itself I don't really know, all I know is that this is common for other observatories sent here. And not only circular movements, some have moved in a figure of eight.


JWSTs Lagrange point puts the earth between the sun and the spacecraft. This reduces the thermal load on the spacecraft and aids cooling of the infrared telescope.


Exactly - it's a point you can stay near by orbiting that allows the Earth to act as part of the observatories sun shielding all the time. It's the closest point to earth with that property.
 
tommy1808
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Re: James Webb Space Telescope has a launch date: Dec 18 2021

Sat Dec 25, 2021 12:13 pm

Time to knock on wood!

https://youtu.be/rhtQeqx-riI
 
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Francoflier
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Re: James Webb Space Telescope has a launch date: Dec 18 2021

Sat Dec 25, 2021 12:54 pm

Nominal launch. JWST is on its way to L2. Bon voyage and best of luck!

Talk about a brown trousers moment... I can only imagine the density of the bricks that were being ejected off the behinds of an entire community of scientists and engineers who have been working on this project for close to 25 years now.
Congrats to all involved!

It's far from over though. The most complex spacecraft deployment and commissioning (in a single mission) in human history is still to come.
 
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Nomadd
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Re: James Webb Space Telescope has a launch date: Dec 18 2021

Sat Dec 25, 2021 1:55 pm

zuckie13 wrote:
zanl188 wrote:
Catfry wrote:
As for why JWST need to circle around the L2 point itself I don't really know, all I know is that this is common for other observatories sent here. And not only circular movements, some have moved in a figure of eight.

JWSTs Lagrange point puts the earth between the sun and the spacecraft. This reduces the thermal load on the spacecraft and aids cooling of the infrared telescope.

Exactly - it's a point you can stay near by orbiting that allows the Earth to act as part of the observatories sun shielding all the time. It's the closest point to earth with that property.

You absolutely don't want the Earth to help shield the Webb. Part of the reason for the large orbit around the L2 point is to keep the scope from passing through the Earth's shadow. The thermal transitions would screw everything up.
 
texl1649
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Re: James Webb Space Telescope has a launch date: Dec 18 2021

Sat Dec 25, 2021 2:04 pm

Nomadd wrote:
zuckie13 wrote:
zanl188 wrote:
JWSTs Lagrange point puts the earth between the sun and the spacecraft. This reduces the thermal load on the spacecraft and aids cooling of the infrared telescope.

Exactly - it's a point you can stay near by orbiting that allows the Earth to act as part of the observatories sun shielding all the time. It's the closest point to earth with that property.

You absolutely don't want the Earth to help shield the Webb. Part of the reason for the large orbit around the L2 point is to keep the scope from passing through the Earth's shadow. The thermal transitions would screw everything up.


I believe the JWST will stay in the earth’s shadow the whole time. Part of the reason for L2’s selection was just that, as it helps keep it so cool?

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