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The analogy - I'd rather have 1 sharp knife than 100 dull ones - seems apt.

I'm not smart enough to know if something like Webb can be horizontally scaled into 100 or 1000x small sats to produce the same result.

My guess is not.

I think we need a super sharp knife and it's worth the investment.

I agree with that, but still it's sometimes worthwhile to have a few dull knives around as well as backup. I mean, Hubble isn't huge; it's a 2.4 meter aperture. Building and launching something equivalent shouldn't be that big a deal these days, especially if you can launch a couple different versions with slightly different capabilities rather than trying to build one space telescope that tries to do everything well.

The argument today is, additional Hubble(s) won't get "more science" per dollar put in. i.e. it's better to put those dollars elsewhere.

We've basically maxed out what Hubble can do. While a sharper visible light telescope would be nice, we need longer wavelengths to see "further back" in history. i.e. Webb

Another thing Hubble did was kick off Dark Energy, but then we needed different instruments to know more about the things that Hubble started. GAIA, Plank satellites are doing nutso things in that space.

All to say, Hubble is f'ing great, let's bring it home and put it in a museum to help inspire the next generation.

> We've basically maxed out what Hubble can do.

My understanding is that all major observatories, and certainly Hubble, are overbooked by a factor of 3 or more for months, and sometimes years, in advance.

Which implies that having 3 Hubbles would allow us to do more research than we can do today. It's not ready for the museum while astronomers still battle over who gets to use it.

An instrument doesn't have to be cutting edge in order to be useful and produce valuable results. Even today, amateur astronomers are still making discoveries (asteroids, sometimes comets) with telescopes that major observatories would have laughed at 100 years ago already.

"The telescope that ate astronomy" (Webb) will undoubtedly make important discoveries. Whether it will be worth its cost considering what we could have built for the same price (such as 10 ELTs!) remains to be seen.

This makes a lot of sense. Imagine being able to afford on a reasonable research budget to schedule within a few days notice the use of a visible light space telescope the equivalent of a Hubble but much cheaper due to optics advancements and miniaturization.

I do have to believe that any satellite designed specifically for one type of measurement would be more robust and cost less than something that did more than one, but I suppose that's not really true. Sometimes multiple measurements simply complement each other too much not to use.

We don't need to replicate Hubble exactly; I'm just suggesting we should put up some cheaper space telescopes with smaller mirrors than James Webb, if such a thing makes sense. Maybe give them a variety of different focal ratios too.

Usually with telescopes you need a huge aperture to see dim things, unless you're willing to wait a long time for an image to resolve. Not everything is super dim, though, so maybe having telescopes with an aperture much smaller than 6.5 meters would make sense for those tasks.

I don't know if there's some other reason James Webb needs a huge aperture than being able to resolve and image quickly. (Maybe the lower wavelengths don't behave on small mirrors?) If that's it, though, it seems like having backup would be good.

The point isn’t dimness. It’s resolution (well angular, the number of pixels also doesn’t matter that much). If you want to resolve things that are close together you physically can’t separate the signals. And what is too close depends inversely on the aperature, so yeah you really need the size, for some observations.

Fun fact for dimness: We are pretty much at “we can count every photon that comes” so if you want to pick up far away things, increasing the aperature is also one of the few things you can do. But at that point you’d probably prefer multiple telescopes if you can align them properly

Is it just that infrared light doesn't focus as easily as visible light unless you scale up the size of the telescope accordingly? (For instance, at some point light stops behaving like light and starts behaving like radio waves.)

The wave length of the photons also goes into it yes. I’d have to look up the precise formula. But it’s basically larger aperature -> smaller angle of separation. Longer wavelengths -> larger angle of separation.

From a physics point of view there really isn’t much difference between light and radio waves. Both is just em radiation. But the absorption by matter (well really gas, there is nothing else) changes with wavelength too. And you’d optimize the ccds for whatever you want to look at. So that would be the primary consideration and keep in mind these things tend to also be build as tech demos (which also means you typically don’t get to realize all design capabilities in action). So “because it’s the most we could get away with” is a reasonable reason

I don't see this as a valid analogy. You can't aggregate the dull knives in order to almost replicate or even improve the cutting performance of a sharp one.

But you can use many separate mirrors with artifacts to replicate a perfect mirror, as long as you are able to do some post-processing on the array of mirrors with artifacts. And with proper post-processing you may even be capable of extracting additional information which a single perfect mirror would not be able to deliver.

You're right, the analogy has its limits.

> But you can use many separate mirrors with artifacts to replicate a perfect mirror

It is theoretically possible, but is it practically so? My argument/usage of the analogy is that it isn't today. That as the analogy says, if we put up 100x small mirrors we just get 100 dull knives and blurry science[0].

[0] https://images.ctfassets.net/cnu0m8re1exe/3grbH0eWtw0AxG3MUT...

It’s been done many times.

Some examples: https://www.dragonflytelescope.org/gallery.html is an array of telescopes (long off the shelf photographic lenses) to achieve exactly that. Photographic lenses tend to give higher image quality, but don’t gather enough light. Solution? Stack many of them and point in the same direction. It’s not just a flight of fancy, they made some breakthrough science with this.

A somewhat less relevant case is ALMA - millimetre wave array in the Atacama. Millimetre waves are a bit longer than IR, somewhat between IR and microwave, and telescopes look like radio dishes, not optical devices. Anyway, the array stacks many tens of such receivers to produce one antenna with a massive effective diameter. In this case, the key advantage is in fact resolution: by spreading the dishes around, you get much higher overall resolution than one massive dish, something we probably couldn’t achieve with IR (too computationally expensive).

Whether launching 10 satellites with 1/3 mirror diameter is cheaper is a whole different question.

Not sure why you're bringing land based solutions to the conversation with "it's been done many times".

If that's the case Webb has been done many times and is super easy.

The physics of stacking detectors doesn't depend on space vs. land. 100 "blunt" telescopes does give you a "sharp" one, on Earth and in orbit.

It does when the position of each sensor relative to the position of the others matters. On earth that's trivial, but if you're 1.5 million kms out in space you could imagine this being significantly more difficult.

Not to mention, each of these 100 units would require the same shielding from radiation as the giant one does for the same reasons. We chose L2 for a very good reason; where are these 100 going to go? What are the odds that each one will end up where it needs to be x100 attempts?

We do actually. One area in which we make enormous progress is simulation. The entire perseverance trip was almost perfectly simulated in a simulator. It's predecessor only partly. The JW launch and deploy steps are also simulated in a very detailed way. Many different (fault) scenarios are tested. I have good faith everything will go as planned.

That's sounds really interesting! Any resources for the layman that would provide more detail?

I can't even follow the news because I know how disappointed I'll be if the launch crashes. Wake me up when it's over.

Couldn’t agree more. I’m a huge space nerd and this is the LEAST I’ve followed a project because I’m so worried it’ll fail. I keep up with the headlines but I’ve found it very difficult to get excited over it as I’m pretty much expecting the worst and anything more than that will be a bonus to enjoy later.

Ditto! As we approach the launch date, the feeling in my stomach when I read about Webb is getting worse.

JWST is going to revolutionize our understanding of cosmos, but only because it's target spectrum, which requires operating temperatures around 45K(-228°C!), to completely eliminate blackbody radiation. Which means that tender layers of sunshield must... OHMY panic attack ...

I’m less nervous about a launch crash than about the hundreds of moving parts that have to perfectly unfurl the thing between the launch and L2

I have an intuition that we'll increasingly run up against practical limitations in undertaking ever more complex projects of this kind in the coming years.

This is already happening - Webb took 7 years longer than expected and cost $10b instead of the projected $5b.

Specifically for space telescopes, I am optimistic for the future because launching mass into orbit is getting cheaper and cheaper. One main reason Webb has to be extremely expensive is that it also has to be extremely lightweight. If it becomes 10x cheaper to stick things in orbit then we can save money on construction too because we won't have to optimize weight as much.

Of course, once space telescopes become cheap and normal, it'll be time to think about constructing a radio telescope array on the far side of the moon.... :D

The cost of Ariane 5 rocket is below $200m, which is a rather small fraction of the overall budget of $5-10b. If the main reason for the huge cost is to make it so lightweight, why didn't they go with more capable heavy-lift rockets to cut some R&D costs already? At least, Delta IV Heavy seems to have a significantly larger max. payload [1]. The JWST was still in re-planning phase as of 2005 and Delta IV Heavy was already operational at that point.

[1] https://en.wikipedia.org/wiki/Heavy-lift_launch_vehicle

> It's also made me wonder if there's a way for humanity to pivot to more "horizontally" scaled science.

Today with F9 (and Starship not too far) yes. Launch costs are a fraction of what they were just a few years ago.

When Webb was planned? No way. Keep in mind that it's the same agency that gave us the SLS.

> It's also made me wonder if there's a way for humanity to pivot to more "horizontally" scaled science.

We do a lot of that already.

The purpose of flagship observatories is to do what can't be done with many cheap, easily produced instruments.

SpaceX is showing the way.

No being afraid of failure allow to simplify, accelerate the process and reduce the cost by an order of magnitude

This is how the Soviets beat us to orbit. They were less afraid to blow up a few rockets.

And dogs.

Ah yes killing dogs. Much less ethical than the animals that NASA used right?

NASA did animal tests too.

If you were able to launch and rendezvous in orbit, I wonder how much cheaper something like the JWST gets if it could be built up piecemeal? The unfurling mechanism itself exists because of payload width limits. How much cost is bound up in "we can't just keep launching rockets because rockets are expensive" and how much is bound up in "precision technology for precision observations"?

I dislike this comparison because we want many of SpaceX's rockets, but we don't really want many Webbs. The rapid iteration argument isn't amazing.

I mean it'd be awesome to have many, but not realistic in any real sense.

But I 100% agree w/ the cost overruns being a massive problem.

It might be an apt comparison though.

I much rather have reusable rockets than having ISS.

I much rather have in-orbit construction infrastructure than having either hubble or JWST.

I much rather have remote repair and maintenance satellites/crafts than having a robot rover on Mars.

If you keep doing what you barely can do, you'll keep doing it for the highest price possible. Instead you can invest in the infrastructure, and do things as they get cheaper with your current infrastructure.

Send the components up over several launches and build it directly in space?

Exactly. It is so sad to see many great engineers working on decade-long projects with 300-something single failure points.

That time and money should instead be spent on reducing the cost per kg to orbit, as well as in-orbit manufacturing. Then engineers would spend the bulk of their time on actual science goals, not on tangents of fragile deployment sequences or shaving few grams from there and there.

Reducing cost per kilogram sounds like a good idea at first - but then, that means people will become less careful about what they send up, eventually leading to space debris issues. The tragedy of the commons is a thing, even in space. I guess there should be an equilibrium price on kilogram-to-orbit.

Yeah, but it is somewhat like saying as your revenue scales, so does your expenses. And it indeed does. But it is a net win at the end of the day, for 10% of a billion is much better than 10% of a million.

With space debris, come debris cleaning bots, with those bots come more space debris, and next generation of cleaning bots ad infinitum. The net profit/benefit will scale in the meantime, which is what really matters.

I think these are large vertical projects because of the nature of the problem. I.e., the data we're after is inherently obfuscated by our earthly dwelling so we need to get our instruments a long ways "out-there". And to do so incurs a lot of risk and, generally speaking, the only institutions large enough to incur a risk that large without much profit upside are governments.

Now maybe we'll find clever ways to get different data cheaply that meets similar ends, but that seems to be hinged on hope at the moment.

That's part of the problem, another part is lack of scale in the space launch market, which results in relatively small and expensive launchers. Lots of complexity and thus cost in JWST could've been avoided if it could be heavier and larger.

How would you propose to fix that problem? I suppose we could get some asteroid barons that bring in a profit motive but fundamental science rarely has a profit since, by definition, it hasn’t found an application yet

SpaceX dropping launch costs with Falcon 9 already did that. The IXPE mission launched last week went up in a gigantic, barely filled fairing, because SpaceX bid below what the previous "cheap" launch was going to be.

Two tools:

One, commoditize your complements. The complement of satellites is rockets, make rockets cheaper and you simplify the process of getting to space.

Second, build towards economies of scale. A one-off is going to be ludicrously expensive, even the Apollo program saved money by reusing technology from military missiles. SpaceX has built more than a hundred rockets and launched more than a thousand satellites. Asteroid barons launching megatons to orbit would certainly make launching a 6.5 ton payload a non-issue. The complexity in the smartphone in my pocket boggles the imagination, I bought it for $200 but if it was a one off you'd have to be Bruce Wayne to afford it.

Sometimes there just is no substitute.