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I can't find an answer to this anywhere: is there a backup JWST (or parts thereof) if this one fails to launch?
by lainga 5y ago
I can't find an answer to this anywhere: is there a backup JWST (or parts thereof) if this one fails to launch?
- NikolaeVarius 5y agono
- 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."
- 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.
- crate_barre 5y agoMakes me wonder if it would have been smarter to build it in a modular way with different pieces being sent up one at a time, assembled on the ISS, then launched in the direction it needed to go.
- jandrese 5y agoThen you have multiplied your launch risk by the number of launches it would take to get it up there, plus there is the difficulty of assembling it in orbit. The only other project built like that was the ISS, and it took decades and a launch vehicle that no longer flies. The biggest problem would be that it would be in the ISS orbit, which would require a lot of delta-V to get it to its final orbit.
- jbay808 5y agoAn advantage of assembling it in ISS orbit is that you have DEXTRE and a team of spacewalking astronauts available to do the unpacking and assembly!
- echelon 5y agoOr an altogether different design: thousands of cheap, totally fungible sensors in an array at the L2 point. Not only would they be replaceable, but we could increase capacity in the future.
- petschge 5y agoExcept that interferometry at IR is still extremely hard.
- dekhn 5y agohumanity has a lot of experience building reliable one-offs, actually a lot more experience and a lot better experience than with modularity and bits and pieces. I'm a software engineer by trade but every time I look into industry (ship building, skyscrapers, etc) you realize: that aphorism about software engineers, woodpeckers and civilization was absolutely right.
- echelon 5y agoThis is our only shot. They didn't replicate the build. https://www.quora.com/What-would-happen-if-the-James-Webb-Space-Telescope-launch-vehicle-were-to-undergo-a-catastrophic-failure-at-launch https://www.quora.com/What-would-happen-if-the-James-Webb-Sp...
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- mikepurvis 5y agoRelatedly, I'd be curious to know what the split has been of the $10B "program cost" in terms of development vs manufacturing. I assume that like with most things, the vast majority of the cost has been in the design and documentation over its 30 years of development. At the same time, there's obviously a ton of extremely high precision bespoke components in there, so "building another one" would definitely not be trivial.
- 0_____0 5y agoIf it's anything like the hardware engineering programs I've been involved in, at qty=1 the cost is almost all R&D. That includes development of processes to build something like 1.3m wide ultraprecise beryllium mirror segments...
- mikepurvis 5y agoOh absolutely, but I still wouldn’t be surprised if the cost for unit 2 was still another half a billion dollars. It would be fascinating to know.
- bumby 5y agoAerospace isn't necessarily like that for a number of reasons. A large driver of cost is quality control. For example, when a custom part is manufactured it needs to go through a number of tests, some of the raw material needs to be kept and tracked for future testing, etc. When they get shipped they have to be be tracked and handled differently, sometimes accelerometers are placed on the cargo to measure any shocks, etc. They need to be stored in a bonded warehouse, often climate controlled throughout its life. All of that control, testing and documentation adds to the cost even after R&D is a sunk cost.
- BurningFrog 5y agoTo me, this is a major dysfunction of the NASA model. Why wasn't 5 Hubble telescopes launched? The marginal cost for the other 4 must have been vastly smaller than the first. Observation time on the original Hubble is still, after 30+ years a scarce resource. With 5 of them, we could have gotten vastly more science done at smaller cost. I don't have a fully fleshed out theory for why, but part of it is that NASA as a government organization is ultimately a political endeavour, and it will have to optimize for what makes politicians look good in the press, rather than what gives the most science bang per buck.
- spyspy 5y agoEven in high school robotics we built a main chassis and a 1:1 spare for testing and hot swapping parts.
- sho_hn 5y agoThere was. Sort of. https://en.wikipedia.org/wiki/KH-11_KENNEN https://en.wikipedia.org/wiki/KH-11_KENNEN In particular some of the manufacturing tooling for the mirrors were shared, leading to the HST mirror being downsized to 2.4 meters.
- thereddaikon 5y agoIts surprising how many people don't know this all these years later. Hubble is repurposed spy satellite. The main cost of the vehicle isn't in the spacecraft itself though its the optics which are different from those used on KH-11. What is good for looking at Russian military bases doesn't directly translate to looking at galaxies.
- ceejayoz 5y agoIn fact, the NRO donated two Hubble-like KH-11s in 2012, on the condition that they not be used to observe Earth. https://en.wikipedia.org/wiki/2012_National_Reconnaissance_Office_space_telescope_donation_to_NASA https://en.wikipedia.org/wiki/2012_National_Reconnaissance_O... One of them forms the base of https://en.wikipedia.org/wiki/Nancy_Grace_Roman_Space_Telescope https://en.wikipedia.org/wiki/Nancy_Grace_Roman_Space_Telesc....
- kilroy123 5y agoNo, and I think they should have made two of them.
- deleted 5y ago[deleted]
- findalex 5y agoImagine having the replacement gold reflector dish in storage somewhere.
- dotnet00 5y agoIt's worth considering that nowadays we don't really do backup copies of satellites/probes because launch is pretty reliable by now, especially on rockets that have been flying for a while (which is pretty much a requirement to be chosen to launch a flagship project like JWST). Ariane 5 has a long flight record with very few failures and the design has been further carefully reviewed specifically for JWST, with the previous two launches having served as verification for any fixes that needed to be made prior to flying this mission. Basically, the chance of JWST being lost due to a rocket issue is much lower compared to the chance of it being lost due to design issues with the telescope itself.
- dgrin91 5y agoThe answer is no for mainly two reasons: 1. Prohibitive costs. Its extremely expensive (both in money and time) to manufacture many of the parts of the telescopes, such as the reflector dishes. Its even more expensive to do all the testing & certification of the manufactured parts. 2. Its all outdated anyways. The JWST project has been ongoing for literally decades (starting in '96 if I remember). If we were to start from scratch today we would make a lot of different design choices based on more recent technological developments
- gibbonsrcool 5y agoI would love to see a video where one of the engineers on the project talked about what would be different if Webb was started today. Materials, software, processes, everything!
- p_l 5y agoA huge design issue that might - or might not - be pushed would be the power system. Solar panels require that JWST stays in the sun while conducting observations, while at the same time being critically dependant on the observing equipment to be cool - and being unable to just keep it inside bigger structure like with Hubble. This means that there's a huge problematic sun shade structure which is considerable part of the SPOFs still endangering JWST even if it is inserted into orbit correctly.
- ufmace 5y agoNope. Wouldn't be a good use of money anyways. If it fails, it might be because of a design or manufacturing flaw. Better to make the new one after we have some idea what went wrong.