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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

#31

Post by rrss »

ur-whale wrote: post #18
amichail wrote: post #9

Why isn't SpaceX doing this?

> Why isn't SpaceX doing this? Reliability (as in: established track record). Although, if Ariane decides to explode tomorrow, this comment will look ... odd.

Important to note that the agreement was made in 2007, so reliability as a factor would be reliability as assessed in 2007, not 2021.

I think that in 2021, Falcon 9 ‘s track record arguably suggests it is more reliable than Ariane 5, but it doesn’t matter because the Falcon fairing is too small for JWST.

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

#32

Post by adgjlsfhk1 »

architravesty wrote: post #29
ur-whale wrote: post #18

Earlier quoted context omitted.

> Why isn't SpaceX doing this? Reliability (as in: established track record). Although, if Ariane decides to explode tomorrow, this comment will look ... odd.

Falcon 9 has a better track record than Ariane 5 at this point, but SpaceX wasn't really a thing at the time these contracts were signed.

also falcon heavy would be required which only has had 3 launches (all success though)

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

#33

Post by rrss »

khuey wrote: post #23
adventured wrote: post #13

Earlier quoted context omitted.

The launch partner/platform wasn't chosen recently and it's part of what ESA is providing as a partner in the program. "In exchange for full partnership, representation and access to the observatory for its astronomers, ESA is providing the NIRSpec instrument, the Optical Bench Assembly of the MIRI instrument, an Ariane 5 ECA launcher, and manpower to support operations. The CSA will provide the Fine Guidance Sensor…

"not recently" is underselling it a bit. ESA agreed to launch it before Falcon 9 (let alone the Heavy version) had ever flown.

It looks like it was even before Falcon 1’s first success.

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

#34

Post by rrss »

daenney wrote: post #27
gfodor wrote: post #22

Interesting they found a way to add a hidden risk variable to the launch, by sending it up on a day people are having to choose to not be with their families. Have a bad feeling about this :/

“They” didn’t find anything. It wasn’t originally planned for tomorrow. The weather found a way. There’s only so much wiggle room and launch windows.

> It wasn’t originally planned for tomorrow

Right, it was originally planned for 2007.

It is sorta funny that after 14 years of delays they picked the week of Christmas.

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

#36

Post by InTheArena »

ur-whale wrote: post #18
amichail wrote: post #9

Why isn't SpaceX doing this?

> Why isn't SpaceX doing this? Reliability (as in: established track record). Although, if Ariane decides to explode tomorrow, this comment will look ... odd.

This has to be launched by Ariane - it's constraints are tightly bound to what that platform can do, and it's fairing size. Ariane is optimized for GEO insertion, while Falcon is optimized for LEO orbits. You could have used a Falcon, but a payload like this was actually built around the rocket's capability, and this was designed prior to Falcon being a thing.

All that said it's worth nothing that SpaceX's flight success rate is 98.5 (135/137), while Ariane V's is 95.5 percent (106/111).

The really gobsmaking thing about that is that this is that SpaceX's rate is over 11 years, while Ariane's is over 25 years.

It's time to stop thinking of SpaceX as the plucky, untrustworthy startup.

In the future space telescopes like this really need to be built in LEO, and then boosted to Lagrange points. The number of failure modes beyond the typical rocket / stage / fairing, secondary burns that the folding mechanism and the lack of a ability to test a ton of new technology in zero-g orbit makes this far more likely to fail then anyone is comfortable with, given the overall cost to this.

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

#37

Post by jacquesm »

foobarian wrote: post #3

Decades of meticulous planning and they couldn't give their teams a day off on Christmas? Of course it could be that consensus was this beats any other kind of activity that day in which case fair enough. :-)

If you start planning your rocket launches around religious holidays then that is going to be a bit of a problem, there are just too many of them:

https://nationaltoday.com/religious-holidays/

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

#38

Post by Ostrogodsky »

malermeister wrote: post #19
foobarian wrote: post #3

Decades of meticulous planning and they couldn't give their teams a day off on Christmas? Of course it could be that consensus was this beats any other kind of activity that day in which case fair enough. :-)

Lots of European countries celebrate Christmas Evening (Dec 24) more than Christmas Day (Dec 25).

Yeah, 25th is the day to nurse the hangover

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

#39

Post by krisoft »

mortenjorck wrote: post #21
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.

True, though it’s also worth considering that Webb is going far beyond “orbit“ as we generally think of it. I don’t know how much has been launched all the way out to L2 before, but it’s probably an order of magnitude less than what’s in Earth orbit.

> I don’t know how much has been launched all the way out to L2 before...

There is a handy list on wikipedia: https://en.wikipedia.org/wiki/List_of_objects_at_Lagrange_po...

Your intuition is quite right, there is way less satellites parked around L2 than in low earth orbit for example.

But that doesn't really pose too big of a challenges in itself. It is of course far, both distance wise and energetically.

The main complication often mentioned is if something is wrong with the telescope it makes it very unlikely that a crew can visit it to fix it. The way for example how they repaired Hubble is unlikely to happen with Webb.

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