6 ms·
no
by NikolaeVarius 5y ago
no
- Zealotux 5y agoI'm wondering why is that, which part of the effort was dedicated to research and how much time and money would it cost to build a new JWST?
- guerrilla 5y agoThe reasoning that I heard (and I hope I'm relaying this right) was that if it doesn't work then it will most likely be because of something that needs to be redesigned, so there's no point in producing an exact replica.
- mikepurvis 5y agoI think this assumes a successful launch and some kind of issue with the deployment. The other concern is, of course, what happens if it blows up on the launchpad.
- guerrilla 5y agoPresumably they've actually quantified these probabilities and think that the chance of that is relatively very low compared to the chance of something going wrong in the design. These things are not cheap, so it makes sense not to have to make three if the launch succeeds and design fails.
- mikepurvis 5y agoOh yes, I totally agree— this is a very proven rocket, and the deployment sequence is very, very much not proven. So it absolutely makes sense to have gone this way.
- CamperBob2 5y agoThat's assuming that anything that goes wrong in the deployment sequence necessitates a clean-sheet redesign of the whole thing. No reason to think that.
- mikepurvis 5y agoBut with so many things that could go wrong in such a tightly integrated system, it's impossible to predict which components or assemblies may be affected by a partial redesign.
- CamperBob2 5y agoIf you say so.
- Kaibeezy 5y agoAriane 5 appears to have 96% mean reliability. Source: 2021 Space Launch Report – Launch Vehicle by Success Rate (spacelaunchreport.com) - https://www.spacelaunchreport.com/log2021.html#rate https://www.spacelaunchreport.com/log2021.html#rate https://news.ycombinator.com/item?id=29554274 https://news.ycombinator.com/item?id=29554274
- JumpCrisscross 5y agoThe footnote about Lewis Point Estimates is super interesting. "Lewis Point Estimate Determined as Follows. Maximum Liklihood Estimate (MLE)= x/n where x=success, n=tries For MLE<=0.5, use Wilson Method = (x+2)/(n+4) For MLE Between 0.5 and 0.9, use MLE = x/n For MLE>=0.9, use Laplace Method = (x+1)/(n+2) Lewis, J. & Lauro, J., "Improving the Accuracy of Small-Sample Estimates of Completion Rates", Journal of Usability Studies, Issue 3, Vol. 1, May 2006, pp. 136-150."
- Kaibeezy 5y agoConcur. You have to see this thread on it in the NASA Spaceflight forum - https://forum.nasaspaceflight.com/index.php?topic=39928.0 https://forum.nasaspaceflight.com/index.php?topic=39928.0
- sho_hn 5y agoI think OP means "what if the rocket fails". The answer is that building another telescope specimen would be quite expensive, even without any changes to the design. The supply chains aren't set up for volume and integration and testing is very involved. I can't put a number on "the second telescope would be x% cheaper", but it would be very disappointing.
- revax 5y agoAlso Ariane 5 is one of the most reliable rocket capable of launching JWST on the correct orbit.
- cbm-vic-20 5y agoIt's also going out pretty far (the L2 Lagrange point on the other side of the moon), so they also won't be able to perform any manned post-launch repair missions like they did with Hubble.
- guerrilla 5y agoActually I have a question about this. What happens if it fails at L2? Is that position like occupied or more difficult to deal with from then on?
- huntsman 5y agoThe L2 point is unstable do energy needs to be expended to maintain position there.
- Out_of_Characte 5y agoSolar wind will push it out of L2 and into an orbit around the sun. This is already going to happen once JWT runs out of fuel to maintain its position.
- messe 5y ago> so they also won't be able to perform any manned post-launch repair missions like they did with Hubble. In terms of hardware that's readily or soon to be available, it is technically possible. Starship, if it gets off the ground, is the obvious choice. Orion could do it, but it would mean dumping another two billion into JWST. If it really came down to it, Falcon Heavy launched with a Crew Dragon sitting on top of it could probably reach it, although it might need an additional kick stage (I haven't done the maths), and it would need to be crew rated first (and SpaceX don't currently have an interest in doing that).
- bumby 5y agoIf you consider the human to be part of that hardware, it's over 4x the distance that a human has ever travelled. There would still be a lot of technical problems to be figured out.
- throwaway64643 5y agoI'd imagine they just cannot fabricate the mirrors as many as they want. The mirrors, arguably the most important parts of any telescope or optical instrument, need delicate manufacture due to the required precision. At the end of the day, this is not automobile industry.