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I'm not sure you're correct. Consider fabbing chips. Fabs spend an awful lot of time verifying the produced chips. I've seen estimates that verification cost e
by jmyeet 4y ago
I'm not sure you're correct.
Consider fabbing chips. Fabs spend an awful lot of time verifying the produced chips. I've seen estimates that verification cost exceeds fabrication cost.
How much of the development cost of JWST 2.0 would be spent on verification? I honestly don't know but I would guess it's high.
Another factor: part of making a production process is predicated on how many you'd build. We had a process for making Saturn-V rockets based on the number of Apollo missions we planned for. If you then up and decide you need 500 Saturn-Vs you might have to go through a whole new process for something that will scale that high.
Yet another factor: the launch vehicle. If you decide to do JWST 2.0 in 10 years, what launch vehicle will you use? The same one might not exist so the new mission will have to be designed for what is available.
And another: materials science changes. We don't make the same materials that we did 50+ years ago for good reasons but those materials are a key part of the design of something like Saturn-V.
So I imagine JWST 2.0 would be cheaper but 90% cheaper? I'm not convinced.
- dylan604 4y agoI can't wait for JWST 2.0, but we're only talking about JWST #2. We're not talking about upgrades, just another copy. I mean, it should be easy, right? It's in the cloud so to speak, so just spin up another instance and push to a different region. No problemo.
- saalweachter 4y agoThe obvious number to make is 5; currently we only have one at L2. What about L1, L3, L4 and L5?
- MereInterest 4y agoThe advantage of L2 is that is stays in Earth's shadow at all times. None of the other Lagrange points have this benefit.
- WalterBright 4y agoWhy does it need the sun shield, then?
- dylan604 4y agoAsk the moon why during an eclipse it isn't completely shadowed out. It's much closer than L2
- WalterBright 4y agoGood answer! Although the Earth is also much larger than the Moon.
- dylan604 4y agoAnd the JWST is much smaller than the moon
- polishTar 4y agoEarth is not big enough to fully eclipse the sun at the L2 point, but it doesn't matter anyways since JWST was deliberately put in an orbit around the L2 point that never enters the earth's eclipse for energy reasons since the solar panels are not large enough to provide sufficient power during an eclipse. https://space.stackexchange.com/a/57378 https://space.stackexchange.com/a/57378
- MereInterest 4y agoThank on that, and I stand corrected.
- saalweachter 4y agoSo we're back to one for each Lagrange point?
- amluto 4y agoL3 may have some challenges with its Earth uplink, and we wouldn’t be able to see a satellite there very easily. L3, L4, and L5 might need separate shielding from the Earth and the sun.
- WalterBright 4y agoWhat are the odds of two objects at L2 colliding? The telescope does have maneuvering capability, as L2 isn't stable.
- Andrew_nenakhov 4y agoThe odds are astronomically small. ESA has at least 5 other missions aimed at L2. [1] [1]: https://www.esa.int/Science_Exploration/Space_Science/Herschel/L2_the_second_Lagrangian_Point https://www.esa.int/Science_Exploration/Space_Science/Hersch...
- WalterBright 4y ago> astronomically small That's what I supposed.
- dylan604 4y agoThey aren't exactly at L2 as they are orbiting a point that is L2. So just put each one in their own orbit. Hopefully it doesn't get congested that we have to fear a Kessler Syndrome incident at L2
- duskwuff 4y ago> Hopefully it doesn't get congested that we have to fear a Kessler Syndrome incident at L2 Not a concern. First: The Sun/Earth L2 is a big place. JWST's orbit around L2 is substantially larger than the Moon's orbit around Earth, and its orbit moves around in multiple dimensions -- it isn't constrained to a single dimension, like a geosynchronous orbit around Earth is. Even if there were debris in the vicinity, the odds of hitting it would be negligible. Second: Orbits around L2 are inherently unstable -- it's a "saddle point", not an attractor. JWST has to maneuver a bit to keep itself in orbit, so any debris that ended up around L2 would naturally drift away.
- dylan604 4y agoyeah, um, i didn't really mean that with any seriousness, like, at all
- rdevsrex 4y agoIt will be so cool, if eventually we could deploy telescopes on other plants, like in Ad Astra.
- dylan604 4y agoIf we could put one in the orbit of something out around Neptune's orbit, would the distance from Sol be enough that the instruments would not need to be liqued cooled (which supplies is what limits lifespan for JWST)?
- albertsondev 4y agoIt's not the liquid helium that limits JWST's lifespan (as that's in a closed loop), but rather the propellant needed to keep it in a stable orbit. I'm no rocket scientist, but I don't imagine that would be much less of a concern around a further, possibly less stable Lagrange point.
- BurningFrog 4y agoIt has to be L2, because Webb needs the shade. That still leaves the L2s of Venus, Mars, Jupiter etc. And you can probably fit a few more into Earth L2.
- Hikikomori 4y agoIt's actually not in the shade, its orbit around L2 is quite wide. That's why it has the massive sunshield and solar array, it needs a lot of power.
- dreamcompiler 4y agoThere's already a telescope at L1. It always points at the earth. https://epic.gsfc.nasa.gov/ https://epic.gsfc.nasa.gov/
- jmyeet 4y agoThe other 4 Earth Lagrange points are unsuitable for various reasons: L1: between the Sun and the Earth. The Sun reflecting off the Earth would interfere with instruments. L3: This is suitable for positioning but impractical because of distance from a communication and perspective. L4 & L5: these are unsuitable because they're stable. Distance is an issue too. Why are stable Lagrange points unsuitable? Because things tend to collect there. Over the eons a whole bunch of crap has built up there and will continue to do so. That's not what you want when dealing with sensitive instuments. Now you could say that you could orbit L4 or L5 like JWST orbits L2 and that's true but you still expend energy for stationkeeping. At L2 you spend energy to stay around the L2 point. At L4 and L5 you spend energy to avoid falling into the Lagrange point. According to [1][2] it's more expensive (in delta-V terms) to get to L4/L5 than L2 but not hugely so. [1]: https://space.stackexchange.com/questions/27010/how-does-the-delta-v-to-reach-and-orbit-l4-and-l5-compare-to-entering-orbit-arou https://space.stackexchange.com/questions/27010/how-does-the... [2]: https://space.stackexchange.com/questions/57463/what-is-the-delta-v-required-for-insertion-to-sun-earth-l2 https://space.stackexchange.com/questions/57463/what-is-the-...
- Teever 4y agoI don't know if your chip fab comparison is correct. It would be more comparable if you included the cost of building the chip fab itself as well as the R&D cost of several of the key technologies in the fab. Also, the entire Apollo infrastructure was actually designed for many more launches than occurred, that's why some of that infrastructure is still in use to this day. It's been a few years since I read a biography of Von Braun but I remember him making design decisions for Apollo that anticipated many more launches and manned missions to Mars and Venus in the 1970s with a manned Mars base by the early 80s.