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Webb flies Ariane 5: watch the launch live on 25 December

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Re: Webb flies Ariane 5: watch the launch live on 25 December

#71

Post by CyanBird »

Symmetry wrote: post #67
BurningFrog wrote: post #65

We're told that since JWT will travel very far away before it unfolds and activates all its systems, there is no practical way to service it if something would go wrong. Why can't it unfold etc in Earth orbit, where a repair mission can be sent if needed, and then travel to its Lagrange point?

It doesn't have enough fuel onboard to go from LEO to the Lagrange point itself.

It wouldn't need to, you could park it there a secondary liquid fuel booster attached, and then after the origami shenanigans if it unfolds correctly the second booster could send it away to its final position

I saw some interviews of engineers of the jwst and few of them had similar ideas, or at least to assemble them in leo then slingshot them to their final positions/orbits

Re: Webb flies Ariane 5: watch the launch live on 25 December

#72

Post by kataklasm »

jcims wrote: post #63
dimtion wrote: post #42

I do have a question about JWST that I wasn't able to find a fine answer in other forums. A lot of people and engineers are saying that the JWST is a marvel of engineering, with truly inovative technical solutions and a giant step up compared to Hubble Telescope. And it does seems like so! However, I'm always baffled how everyone seems proud that the telescope has something like 200 SPOF during deployment, and if eve…

I think this is your earnest attempt at it but its a good place to apply the story from yesterday 'be curious, not judgemental'.

That's literally what he is doing, isn't it? He thought something was off, and instead of spewing his opinion all over the place he requested information from folks more versed in the domain than him. He is literally being curious, not judgemental.

Re: Webb flies Ariane 5: watch the launch live on 25 December

#73

Post by jacquesm »

kataklasm wrote: post #72
jcims wrote: post #63

Earlier quoted context omitted.

I think this is your earnest attempt at it but its a good place to apply the story from yesterday 'be curious, not judgemental'.

That's literally what he is doing, isn't it? He thought something was off, and instead of spewing his opinion all over the place he requested information from folks more versed in the domain than him. He is literally being curious, not judgemental.

> I'm always baffled how everyone seems proud that the telescope has something like 200 SPOF during deployment, and if even one of them fails the whole mission could fail

I see this as judgmental, am I wrong in that?

Re: Webb flies Ariane 5: watch the launch live on 25 December

#74

Post by jacquesm »

keewee7 wrote: post #45

How much did NASA, ESA and CSA each contribute to this project?

From the JWST wikipedia page:

"In the 2005 re-plan, the life-cycle cost of the project was estimated at US$4.5 billion. This comprised approximately US$3.5 billion for design, development, launch and commissioning, and approximately US$1.0 billion for ten years of operations.[18] ESA is contributing about €300 million, including the launch.[84] The Canadian Space Agency pledged $39 million Canadian in 2007[85] and in 2012 delivered its contributions in equipment to point the telescope and detect atmospheric conditions on distant planets."

https://en.wikipedia.org/wiki/James_Webb_Space_Telescope

Re: Webb flies Ariane 5: watch the launch live on 25 December

#75

Post by jacquesm »

Symmetry wrote: post #70
ajross wrote: post #8

Earlier quoted context omitted.

FWIW: given the extraordinarily complicated mechanical design, merely reaching orbit is the "easy part". The real imagined disasters won't happen until the mirrors assemble.

The Ariane 5 is batting 106 for 111 which is pretty good odds and perfectly respectable for a heavy lift vehicle... but not so much so that I don't wish it was launching on an Atlas 5 instead.

Four of those were in the first 15, the last recent one was in 2018, and was a partial failure.

Re: Webb flies Ariane 5: watch the launch live on 25 December

#76

Post by jacquesm »

argiopetech wrote: post #68
jpgvm wrote: post #47

Earlier quoted context omitted.

Yeah valid. Though the whole "hurtling upwards on top of a bomb" part is still definitely scary in it's own right.

Particularly given the launch record of the Ariane 5 platform. I did some quick research, and no modern launch platform has as high a mission failure rate (4.5%.) The Delta family comes close at 4.4%, but that's a 50yr launch history. The Delta 4 iteration has had no failures.

As I wrote elsewhere, the bulk of those failures were in the first 15 launches, after that it was a very long string of one success after another with one partial failure in 2018.

Re: Webb flies Ariane 5: watch the launch live on 25 December

#77

Post by eterm »

BurningFrog wrote: post #65

We're told that since JWT will travel very far away before it unfolds and activates all its systems, there is no practical way to service it if something would go wrong. Why can't it unfold etc in Earth orbit, where a repair mission can be sent if needed, and then travel to its Lagrange point?

How feasible is a repair mission without the shuttle?

Re: Webb flies Ariane 5: watch the launch live on 25 December

#78

Post by gautamcgoel »

jacquesm wrote: post #74
keewee7 wrote: post #45

How much did NASA, ESA and CSA each contribute to this project?

From the JWST wikipedia page: "In the 2005 re-plan, the life-cycle cost of the project was estimated at US$4.5 billion. This comprised approximately US$3.5 billion for design, development, launch and commissioning, and approximately US$1.0 billion for ten years of operations.[18] ESA is contributing about €300 million, including the launch.[84] The Canadian Space Agency pledged $39 million Canadian in 2007[85] and in…

Those numbers are completely obsolete; the final price tag was over $10B.

Re: Webb flies Ariane 5: watch the launch live on 25 December

#79

Post by jacquesm »

gautamcgoel wrote: post #78
jacquesm wrote: post #74

Earlier quoted context omitted.

From the JWST wikipedia page: "In the 2005 re-plan, the life-cycle cost of the project was estimated at US$4.5 billion. This comprised approximately US$3.5 billion for design, development, launch and commissioning, and approximately US$1.0 billion for ten years of operations.[18] ESA is contributing about €300 million, including the launch.[84] The Canadian Space Agency pledged $39 million Canadian in 2007[85] and in…

Those numbers are completely obsolete; the final price tag was over $10B.

Then maybe you should update that wikipedia page.

Re: Webb flies Ariane 5: watch the launch live on 25 December

#80

Post by beamatronic »

throw0101a wrote: post #60
dimtion wrote: post #42

I do have a question about JWST that I wasn't able to find a fine answer in other forums. A lot of people and engineers are saying that the JWST is a marvel of engineering, with truly inovative technical solutions and a giant step up compared to Hubble Telescope. And it does seems like so! However, I'm always baffled how everyone seems proud that the telescope has something like 200 SPOF during deployment, and if eve…

> Is JWST as brittle as the news want to make us think? Or are there technical reasons or acceptable failure modes that gives confidence that those steps are not as critical as the news let us people know? There is no room for redundancy in many aspects of the design, unlike, say a Boeing 777 or Airbus A350. How can you have a redundant heat shield, or primary mirror (two parts of which swing)? I'm sure some computer…

The answer to your redundancy question is: Assembly line.

Instead of ramping up a project, and building 1 of something, you would plan to do more than one, and you could iterate over time as you learn. SpaceX is doing a good job of this.

If 1 Webb telescope is valuable then wouldn't 3 or 5 also be valuable?

We have a number of proven space designs at this point: Soyuz, Spirit/Opportunity rovers.

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