8 ms·

While I agree on an emotional level that this would be a tragedy if it fails I have serious concerns about the fact that we've invested so much in this one inst

While I agree on an emotional level that this would be a tragedy if it fails I have serious concerns about the fact that we've invested so much in this one instrument. I wonder, if the launch or the satellite was to fail would we end up firmly accepting that this was a bad idea and instead of spending 10 billion on 1 really amazing telescope we should have spent 1 billion on 10 telescopes of 500m on 20 telescopes. I definitely don't want the JWST to fail. I've never seen an image which endears such an existential crisis as the hubble deep field. I simply, paradoxically, wonder what good might come if this does fail.

holler 5y ago
I feel the same way, and I'm reminded of a quote from Elon Musk recently when discussing Starship's Raptor engine: "It's 10-100x more difficult to design the production system than the engine itself" So what we really need is to invest and innovate in the production of complex telescopes/probes/etc such that it doesn't cost $10 Billion and 20 years to build, and the loss of one wouldn't hinder the overall production. https://youtu.be/t705r8ICkRw?t=238 https://youtu.be/t705r8ICkRw?t=238
- stopping 5y ago
  The cost doesn't come from a lack of production efficiency. A significant fraction of the cost is for testing/validation of the spacecraft, which must be done for every unit you produce. Simulating operating conditions on Earth is extremely expensive and time consuming.
  - aero-glide2 5y ago
    When you build 20 scopes you can use the fail fast approach to better iterate on the next versions. It's okay if the first few fail.
    - petschge 5y ago
      Except after the second failure you have a REALLY hard time to get funding out of politicians...
      - loonster 5y ago
        Its about setting proper expectations. Its not a failure if its expected. Get the politicians to commit to all 20 launches in advanced.
        rizky05 5y ago
        How do you know it only needs 20 launches ?
  - holler 5y ago
    It's the same reason SpaceX is eating Boeing's lunch with their space program. One uses an iterative build process, and the other uses the more historical waterfall method. That's not to say waterfall didn't or doesn't have merit here, just that it seems like technology has advanced to a place where hopefully in the future we can build these things much faster and cheaper, such that the stakes aren't so high for a single unit.
    - stopping 5y ago
      I don't disagree with your point re: Boeing v SpaceX, but precision scientific instrumentation is a very, very different domain where "move fast and break things" cannot be naively applied. The sensitivity to failure is so ridiculously high that you need 6 to 7 sigmas of reliability for each of ten thousand critical components in order to even have just a 90% chance of mission success. Something as simple as an instrument bring slightly out of tolerance, faulty rad-hardening on a CPU, the sun shield having a minor tear, are all enough to completely jeopardize the entire mission. As a fully integrated system, JWST is at least an order of magnitude more complex than Starship, whose main design goals (launch, orbit, land, don't explode) tend to favor a more iterative approach.
      - gfodor 5y ago
        Pretty sure this argument could have been levied against rocketry. For scientific telescopes most likely a frame shift would be needed to break out of this mindset that would be analogous but distinct from the one applied to rocketry.
        stopping 5y ago
        There are two key differences between rockets and space telescopes (any space-faring probe, really) which prohibits "iterate to failure" as a development technique: 1. Forensics difficulty. You need extensive data to debug issues for complex systems. You can collect so much more data from terrestrial testing, which allows you to do the extensive forensic analysis required to achieve the required component reliability. Once you put a telescope in space, you can't inspect it anymore. A lot of the sensitive components which might fail on JWST have to be inspected to microscopic precision in order to perform adequate failure analysis. 2. Design requirements are far, far more precise. Many failures in deep space are effectively impossible to correct in later iterations due to point 1. Telemetry and sensor data is enough to debug rockets, but for JWST you would need to ship so much extra data/sensor infrastructure alongside the telescope that the whole project becomes recursively intractable. The system complexity is so high that you absolutely must have the ability to make arbitrary system corrections because the chance of "building everything correctly the first time" is effectively zero, even with perfect hindsight! Essentially, any time you build the thing from scratch, you will always find mission-ending statistical deviations. The objective of on-ground testing is to identify and correct those specific deviations, until the whole system is within design tolerances. If you were to totally rebuild it, the next iteration will have a totally different set of statistical deviations which will need to be corrected. This process of development involves "hardening" the entire system through extensive testing, because it impossible to build a fully-hardened system to start with, even after "learning" from previous attempts.
  - gpm 5y ago
    If you can produce them cheaply but not test them cheaply, the solution is really simple, just don't test them. Send them to space, see what happens. It's not like space telescopes need any of the valuable orbit space, and even if they did it's easy to put thrusters on board that can de-orbit them or move them to a graveyard orbit (depending on their operational orbit) in the case of failure.
    - stopping 5y ago
      I addressed this in another comment: https://news.ycombinator.com/item?id=28452001 https://news.ycombinator.com/item?id=28452001 To summarize, you have to have the ability to correct statistical aberrations after manufacture via extensive validation and testing, as opposed to design aberrations which can largely be eliminated through destructive iteration. Without the former process, you'll launch a million telescopes and not a single one will work.
- marcodiego 5y ago
  This is not a device that will be produced in an assembly line. Efforts to improve its production would be nullified by the fact that every unit is itself a prototype.
  - BobbyJo 5y ago
    I wonder about that. Hubble, after all, could have been looked at the same way from the outside, but it was essentially a proof of concept for a constellation of top secret satellites still in use today.
    - anonymousiam 5y ago
      https://www.americaspace.com/2012/06/06/top-secret-kh-11-spysat-design-revealed-by-nros-twin-telescope-gift-to-nasa/ https://www.americaspace.com/2012/06/06/top-secret-kh-11-spy...
    - asmithmd1 5y ago
      The opposite is true. Hubble is a stripped down version of a Keyhole spy satellite that was already in production. One of the major repairs (replace solar panels) was required because of long duration exposures used in astronomy that are not used in spying. Remember that Hubble was essentially useless until heroically repaired the first time by Story Musgrave. Many subsequent repairs were required to get the best pictures from it - like the deep field, long duration picture.
  - devnulll 5y ago
    There's another way to think of this. Let's use Starlink as an example, which is ~1300 today growing to 40k satellites in LEO. If each of these had a high-grade commercial camera lens pointed towards earth, you could have real-time viewing of the entire planet with just a little bit of math. With a bit more fun (and for each click of optics improvements), you could "Bullet Time" view a great number of things... If each of these had a high-grade commercial lens pointing outwards, what could that be used to capture? At scale, it seems like doing diff's against all the images would reveal a huge number of previously unidentified asteroids and other near-earth objects. What if you put "very good" optics on them? Or a radio antenna pointed out? Could you make earth sized optical or radio telescopes? Seems like you could. It's increasingly looking like the assumption each one needs to drive the state of the art, and each one needs to be "space grade at 100x the cost" is a fallacy simply because launching was historically so expensive.
- AdamJacobMuller 5y ago
  I largely agree, even though you're being downvoted. What we really need is to standardize as much of the telescope as possible. Communications? Don't need to be bespoke per satellite. Guidance/Navigation? Doesn't need to be bespoke. Ultimately only the actual optical payload really needs to be bespoke. Commonality of components and design can drive down prices and reduce time-to-launch.
  - Rebelgecko 5y ago
    The problem is that if you can't really just standardize every subsystem unless you're willing to give compromise your mission in the name of a one-sizw-fits-all approach. Presumably the people who built JWST passed on of-the-shelf busses for a reason. Imagine if you to tried to force JWST's bus onto every satellite: people who don't care about pointing accuracy end up spending zillions of dollars so they can have fraction of an arc-second precision satellites that are in Earth orbit have different thermal needs than one in L2 satellites that are less weight sensitive waste money on carbon fiber an instrument that needs to be cooled down to 50K doesn't need a JWST-tier cryocooler, etc. You could try having a range of things, e.g. small, medium, and large bus with a handful of interchangeable subsystems. But you're still asking designers to sacrifice their precious size, weight & power requirements
armchairhacker 5y ago
How much of the money was spent on the James Webb itself, as opposed to research, testing, etc. that we can use on future telescopes?
- nickff 5y ago
  That really depends on the configuration and architecture used for the future telescopes.
- AdamJacobMuller 5y ago
  Isn't that exactly the point of saying we should deploy more, cheaper per unit, devices? Sure some of the money went to R&D but the question is not can be it be used on a future telescope, it's will it be used? I suspect if someone wants to launch another telescope today they would look at JWST and largely say they need to start over because it doesn't make sense to start with a 20-year-old design.
  - fogof 5y ago
    Well maybe the point is that it's simply not possible to even design a telescope like this without a huge activation energy of R&D costs. If we had deployed more, cheaper devices, it might be the case that those devices, even taken together, would not have given us the information that JWST will. Take the sunshield - the huge tarp-looking thing that you always see below the telescope itself. My understanding is that this is critical for JWST to see in the deep infrared, since otherwise heat will interfere with the imaging. Probably a lot of money was spent on the development of this. But if that money had just been spent on 20 other telescopes, none of them would have been able to capture that part of the infrared spectrum that JWST will.
    - asmithmd1 5y ago
      The original sin is the lack of will to make the Webb nuclear powered. Since it is solar powered, it has to be in the sun. Since it has to be in the sun, it needs a huge shield. Since it is solar powered, it must be passively cooled to save power. Since it is passively cooled, it needs the science experiment - 5 layer shield deployed with 50 different pulleys, cables, telescoping poles and who knows what else. The power limit also requires that science data be downloaded with an experimental 26Ghz radio that only the three 100' diameter Deep Space Network dishes can receive. The projected science data download will require using the DSN for 8 hours a day, everyday for 5-10 years. They should have started over using nuclear power and then they would have had a chance.
caconym_ 5y ago
Setting aside the question of whether one telescope-sized duck is more formidable than ten duck-sized telescopes, is it really plausible that the funding and management processes that produced the JWST might learn from past mistakes and evolve toward more efficient use of time and money? If we're going to make that shift at all, I personally think sending ~$10B up in smoke will hurt rather than help. We're arguably already on a good trajectory (heh) with increased competition in the launch services market threatening to break up the pork party, and that kind of loss would be a big PR blow for NASA.
- sandworm101 5y ago
  >> that the funding and management processes that produced the JWST might learn from past mistakes and evolve toward more efficient use of time and money? Nope. This is a generational project. At all levels, but more so at the top, the people involved have spent significant blocks of their working lives on this project. Many have begun and ended decade-spanning carriers totally within this one program. It has taken so long that few will be around to contribute to the next. The institutional knowledge will have all retired or moved on by the time we are ready to fund the next epic telescope. This problem has parallels other programs such as the F-35. Nobody lives/works long enough to see the project from beginning to end. Everyone at the start moves on/up/out. Those present at the end joined in the middle after major decisions were already set in stone. Priorities shift. Deadlines measured in decades start to seem unreal. Everything slips into bloat and delay because so few expect to still be around on D-day. It's a problem with no good solution.
ddevault 5y ago
The thing about telescopes is that bigger is always better, and bigger is always more expensive. 10 small telescopes will do less useful science than one large telescope. The optical capabilities of a telescope are a function of the mirror diameter.
- cedilla 5y ago
  That isn't always true, for longer wavelength in particular it's very feasible to use many smaller telescopes with interferometry to reach effective aperture sizes we could never reach with a single telescope. However in regards to JWT I expect that a lot of its missions will collect miniscule amounts of light, making interferometry infeasible.
creato 5y ago
Why don't we just build several identical copies of things like this during development? Surely most of the cost is in the engineering, the added cost of fabricating a few of everything must not be that high. Then if it does fail for some reason, we can just try again.
- rich_sasha 5y ago
  This is in fact done (effectively). All components have a "flight spare", which is just a second copy. It can be swapped should any component fail before take-off. It doesn't get assembled into the whole thing though. Other uses include debugging already-launched kit with the easily accessible copy, reusing in other projects, and ultimately, museum artifacts. It is also worth saying that producing anything, from mirrors and cameras, to boring screws and nuts, that end up going into space, is no small endeavour. It's not the case that you can just mill something out of aluminium, then do it N more times. Here's a nice video about it: https://www.youtube.com/watch?v=QlASewYMDsg https://www.youtube.com/watch?v=QlASewYMDsg (in fact in the specific context of JWST)
doctor_eval 5y ago
If JWST was designed today, with F9 reusable and Starship on the horizon, would/could it have been cheaper to have multiple launches and assembly on orbit, rather than the super complex unfolding system and all-eggs-in-one-basket launch?
- sandworm101 5y ago
  >> cheaper to have multiple launches and assembly on orbit This has only been done a handful of times outside of Kerbal. Apollo was one of the very few times that two spacecraft launched separately and then continued onto another orbit (as opposed to space stations that are built and stay where they are). Connecting two objects and then blasting them into a transfer orbit ... even Apollo didn't do that. I don't think it has ever been done. It would mean strong docking hardware and deep structural analysis to handle flexing while under even moderate thrust, something far more than aligning a couple docking ports. Getting a delicate craft to escape velocity would require multiple burns over multiple orbits, necessitating engines that could relight many times. Electric drives could work, but they lack the thrust for a final definitive escape towards an L point.
  - polytely 5y ago
    I think it would be very valuable for humanity to start learning how to do assembly in orbit, I think china is planning to do that for their next space station. not sure if that will actually happen, but it would be cool if that sparked a new space race. I think you would be a bit disadvantaged as a superpower when the other superpower can build stuff in orbit while you can't.
    - doctor_eval 5y ago
      Once we build the first large, pressurised hangar in space, then we will be able to start assembling stuff up there far more easily. That's the kind of space station I'm looking forward to. I'm sure assembling a spacecraft while wearing T-shirts in 0G will be far easier than working in 1G. If only building a large, pressurised hangar in space was easy!
cblconfederate 5y ago
Will it cost 10 billion to build it again?
gorgoiler 5y ago
At this scale and level of tech, projects such as this are employment and research programs just as much as they are a means to get a nice telescope at the end.
sandgiant 5y ago
This is a pretty strong claim to make without any arguments to back it up. Do you have scientific arguments as to how 10 telescopes at 1/10 the cost would have been better?

holler 5y ago

I feel the same way, and I'm reminded of a quote from Elon Musk recently when discussing Starship's Raptor engine: "It's 10-100x more difficult to design the production system than the engine itself" So what we really need is to invest and innovate in the production of complex telescopes/probes/etc such that it doesn't cost $10 Billion and 20 years to build, and the loss of one wouldn't hinder the overall production. https://youtu.be/t705r8ICkRw?t=238 https://youtu.be/t705r8ICkRw?t=238

stopping 5y ago
The cost doesn't come from a lack of production efficiency. A significant fraction of the cost is for testing/validation of the spacecraft, which must be done for every unit you produce. Simulating operating conditions on Earth is extremely expensive and time consuming.
- aero-glide2 5y ago
  When you build 20 scopes you can use the fail fast approach to better iterate on the next versions. It's okay if the first few fail.
  - petschge 5y ago
    Except after the second failure you have a REALLY hard time to get funding out of politicians...
    - loonster 5y ago
      Its about setting proper expectations. Its not a failure if its expected. Get the politicians to commit to all 20 launches in advanced.
      - rizky05 5y ago
        How do you know it only needs 20 launches ?
- holler 5y ago
  It's the same reason SpaceX is eating Boeing's lunch with their space program. One uses an iterative build process, and the other uses the more historical waterfall method. That's not to say waterfall didn't or doesn't have merit here, just that it seems like technology has advanced to a place where hopefully in the future we can build these things much faster and cheaper, such that the stakes aren't so high for a single unit.
  - stopping 5y ago
    I don't disagree with your point re: Boeing v SpaceX, but precision scientific instrumentation is a very, very different domain where "move fast and break things" cannot be naively applied. The sensitivity to failure is so ridiculously high that you need 6 to 7 sigmas of reliability for each of ten thousand critical components in order to even have just a 90% chance of mission success. Something as simple as an instrument bring slightly out of tolerance, faulty rad-hardening on a CPU, the sun shield having a minor tear, are all enough to completely jeopardize the entire mission. As a fully integrated system, JWST is at least an order of magnitude more complex than Starship, whose main design goals (launch, orbit, land, don't explode) tend to favor a more iterative approach.
    - gfodor 5y ago
      Pretty sure this argument could have been levied against rocketry. For scientific telescopes most likely a frame shift would be needed to break out of this mindset that would be analogous but distinct from the one applied to rocketry.
      - stopping 5y ago
        There are two key differences between rockets and space telescopes (any space-faring probe, really) which prohibits "iterate to failure" as a development technique: 1. Forensics difficulty. You need extensive data to debug issues for complex systems. You can collect so much more data from terrestrial testing, which allows you to do the extensive forensic analysis required to achieve the required component reliability. Once you put a telescope in space, you can't inspect it anymore. A lot of the sensitive components which might fail on JWST have to be inspected to microscopic precision in order to perform adequate failure analysis. 2. Design requirements are far, far more precise. Many failures in deep space are effectively impossible to correct in later iterations due to point 1. Telemetry and sensor data is enough to debug rockets, but for JWST you would need to ship so much extra data/sensor infrastructure alongside the telescope that the whole project becomes recursively intractable. The system complexity is so high that you absolutely must have the ability to make arbitrary system corrections because the chance of "building everything correctly the first time" is effectively zero, even with perfect hindsight! Essentially, any time you build the thing from scratch, you will always find mission-ending statistical deviations. The objective of on-ground testing is to identify and correct those specific deviations, until the whole system is within design tolerances. If you were to totally rebuild it, the next iteration will have a totally different set of statistical deviations which will need to be corrected. This process of development involves "hardening" the entire system through extensive testing, because it impossible to build a fully-hardened system to start with, even after "learning" from previous attempts.
- gpm 5y ago
  If you can produce them cheaply but not test them cheaply, the solution is really simple, just don't test them. Send them to space, see what happens. It's not like space telescopes need any of the valuable orbit space, and even if they did it's easy to put thrusters on board that can de-orbit them or move them to a graveyard orbit (depending on their operational orbit) in the case of failure.
  - stopping 5y ago
    I addressed this in another comment: https://news.ycombinator.com/item?id=28452001 https://news.ycombinator.com/item?id=28452001 To summarize, you have to have the ability to correct statistical aberrations after manufacture via extensive validation and testing, as opposed to design aberrations which can largely be eliminated through destructive iteration. Without the former process, you'll launch a million telescopes and not a single one will work.
marcodiego 5y ago
This is not a device that will be produced in an assembly line. Efforts to improve its production would be nullified by the fact that every unit is itself a prototype.
- BobbyJo 5y ago
  I wonder about that. Hubble, after all, could have been looked at the same way from the outside, but it was essentially a proof of concept for a constellation of top secret satellites still in use today.
  - anonymousiam 5y ago
    https://www.americaspace.com/2012/06/06/top-secret-kh-11-spysat-design-revealed-by-nros-twin-telescope-gift-to-nasa/ https://www.americaspace.com/2012/06/06/top-secret-kh-11-spy...
  - asmithmd1 5y ago
    The opposite is true. Hubble is a stripped down version of a Keyhole spy satellite that was already in production. One of the major repairs (replace solar panels) was required because of long duration exposures used in astronomy that are not used in spying. Remember that Hubble was essentially useless until heroically repaired the first time by Story Musgrave. Many subsequent repairs were required to get the best pictures from it - like the deep field, long duration picture.
- devnulll 5y ago
  There's another way to think of this. Let's use Starlink as an example, which is ~1300 today growing to 40k satellites in LEO. If each of these had a high-grade commercial camera lens pointed towards earth, you could have real-time viewing of the entire planet with just a little bit of math. With a bit more fun (and for each click of optics improvements), you could "Bullet Time" view a great number of things... If each of these had a high-grade commercial lens pointing outwards, what could that be used to capture? At scale, it seems like doing diff's against all the images would reveal a huge number of previously unidentified asteroids and other near-earth objects. What if you put "very good" optics on them? Or a radio antenna pointed out? Could you make earth sized optical or radio telescopes? Seems like you could. It's increasingly looking like the assumption each one needs to drive the state of the art, and each one needs to be "space grade at 100x the cost" is a fallacy simply because launching was historically so expensive.
AdamJacobMuller 5y ago
I largely agree, even though you're being downvoted. What we really need is to standardize as much of the telescope as possible. Communications? Don't need to be bespoke per satellite. Guidance/Navigation? Doesn't need to be bespoke. Ultimately only the actual optical payload really needs to be bespoke. Commonality of components and design can drive down prices and reduce time-to-launch.
- Rebelgecko 5y ago
  The problem is that if you can't really just standardize every subsystem unless you're willing to give compromise your mission in the name of a one-sizw-fits-all approach. Presumably the people who built JWST passed on of-the-shelf busses for a reason. Imagine if you to tried to force JWST's bus onto every satellite: people who don't care about pointing accuracy end up spending zillions of dollars so they can have fraction of an arc-second precision satellites that are in Earth orbit have different thermal needs than one in L2 satellites that are less weight sensitive waste money on carbon fiber an instrument that needs to be cooled down to 50K doesn't need a JWST-tier cryocooler, etc. You could try having a range of things, e.g. small, medium, and large bus with a handful of interchangeable subsystems. But you're still asking designers to sacrifice their precious size, weight & power requirements

armchairhacker 5y ago

How much of the money was spent on the James Webb itself, as opposed to research, testing, etc. that we can use on future telescopes?

nickff 5y ago
That really depends on the configuration and architecture used for the future telescopes.
AdamJacobMuller 5y ago
Isn't that exactly the point of saying we should deploy more, cheaper per unit, devices? Sure some of the money went to R&D but the question is not can be it be used on a future telescope, it's will it be used? I suspect if someone wants to launch another telescope today they would look at JWST and largely say they need to start over because it doesn't make sense to start with a 20-year-old design.
- fogof 5y ago
  Well maybe the point is that it's simply not possible to even design a telescope like this without a huge activation energy of R&D costs. If we had deployed more, cheaper devices, it might be the case that those devices, even taken together, would not have given us the information that JWST will. Take the sunshield - the huge tarp-looking thing that you always see below the telescope itself. My understanding is that this is critical for JWST to see in the deep infrared, since otherwise heat will interfere with the imaging. Probably a lot of money was spent on the development of this. But if that money had just been spent on 20 other telescopes, none of them would have been able to capture that part of the infrared spectrum that JWST will.
  - asmithmd1 5y ago
    The original sin is the lack of will to make the Webb nuclear powered. Since it is solar powered, it has to be in the sun. Since it has to be in the sun, it needs a huge shield. Since it is solar powered, it must be passively cooled to save power. Since it is passively cooled, it needs the science experiment - 5 layer shield deployed with 50 different pulleys, cables, telescoping poles and who knows what else. The power limit also requires that science data be downloaded with an experimental 26Ghz radio that only the three 100' diameter Deep Space Network dishes can receive. The projected science data download will require using the DSN for 8 hours a day, everyday for 5-10 years. They should have started over using nuclear power and then they would have had a chance.

caconym_ 5y ago

Setting aside the question of whether one telescope-sized duck is more formidable than ten duck-sized telescopes, is it really plausible that the funding and management processes that produced the JWST might learn from past mistakes and evolve toward more efficient use of time and money? If we're going to make that shift at all, I personally think sending ~$10B up in smoke will hurt rather than help. We're arguably already on a good trajectory (heh) with increased competition in the launch services market threatening to break up the pork party, and that kind of loss would be a big PR blow for NASA.

sandworm101 5y ago
>> that the funding and management processes that produced the JWST might learn from past mistakes and evolve toward more efficient use of time and money? Nope. This is a generational project. At all levels, but more so at the top, the people involved have spent significant blocks of their working lives on this project. Many have begun and ended decade-spanning carriers totally within this one program. It has taken so long that few will be around to contribute to the next. The institutional knowledge will have all retired or moved on by the time we are ready to fund the next epic telescope. This problem has parallels other programs such as the F-35. Nobody lives/works long enough to see the project from beginning to end. Everyone at the start moves on/up/out. Those present at the end joined in the middle after major decisions were already set in stone. Priorities shift. Deadlines measured in decades start to seem unreal. Everything slips into bloat and delay because so few expect to still be around on D-day. It's a problem with no good solution.

ddevault 5y ago

The thing about telescopes is that bigger is always better, and bigger is always more expensive. 10 small telescopes will do less useful science than one large telescope. The optical capabilities of a telescope are a function of the mirror diameter.

cedilla 5y ago
That isn't always true, for longer wavelength in particular it's very feasible to use many smaller telescopes with interferometry to reach effective aperture sizes we could never reach with a single telescope. However in regards to JWT I expect that a lot of its missions will collect miniscule amounts of light, making interferometry infeasible.

creato 5y ago

Why don't we just build several identical copies of things like this during development? Surely most of the cost is in the engineering, the added cost of fabricating a few of everything must not be that high. Then if it does fail for some reason, we can just try again.

rich_sasha 5y ago
This is in fact done (effectively). All components have a "flight spare", which is just a second copy. It can be swapped should any component fail before take-off. It doesn't get assembled into the whole thing though. Other uses include debugging already-launched kit with the easily accessible copy, reusing in other projects, and ultimately, museum artifacts. It is also worth saying that producing anything, from mirrors and cameras, to boring screws and nuts, that end up going into space, is no small endeavour. It's not the case that you can just mill something out of aluminium, then do it N more times. Here's a nice video about it: https://www.youtube.com/watch?v=QlASewYMDsg https://www.youtube.com/watch?v=QlASewYMDsg (in fact in the specific context of JWST)

doctor_eval 5y ago

If JWST was designed today, with F9 reusable and Starship on the horizon, would/could it have been cheaper to have multiple launches and assembly on orbit, rather than the super complex unfolding system and all-eggs-in-one-basket launch?

sandworm101 5y ago
>> cheaper to have multiple launches and assembly on orbit This has only been done a handful of times outside of Kerbal. Apollo was one of the very few times that two spacecraft launched separately and then continued onto another orbit (as opposed to space stations that are built and stay where they are). Connecting two objects and then blasting them into a transfer orbit ... even Apollo didn't do that. I don't think it has ever been done. It would mean strong docking hardware and deep structural analysis to handle flexing while under even moderate thrust, something far more than aligning a couple docking ports. Getting a delicate craft to escape velocity would require multiple burns over multiple orbits, necessitating engines that could relight many times. Electric drives could work, but they lack the thrust for a final definitive escape towards an L point.
- polytely 5y ago
  I think it would be very valuable for humanity to start learning how to do assembly in orbit, I think china is planning to do that for their next space station. not sure if that will actually happen, but it would be cool if that sparked a new space race. I think you would be a bit disadvantaged as a superpower when the other superpower can build stuff in orbit while you can't.
  - doctor_eval 5y ago
    Once we build the first large, pressurised hangar in space, then we will be able to start assembling stuff up there far more easily. That's the kind of space station I'm looking forward to. I'm sure assembling a spacecraft while wearing T-shirts in 0G will be far easier than working in 1G. If only building a large, pressurised hangar in space was easy!

cblconfederate 5y ago

Will it cost 10 billion to build it again?

gorgoiler 5y ago

At this scale and level of tech, projects such as this are employment and research programs just as much as they are a means to get a nice telescope at the end.

sandgiant 5y ago

This is a pretty strong claim to make without any arguments to back it up. Do you have scientific arguments as to how 10 telescopes at 1/10 the cost would have been better?