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Comment by jmyeet | Hacker News Reader

The cost of launch is relatively low, meaning several hundred million out of a a $15-20B budget.

But a given launch system is deeply intertwined with designing the mission. The size, the weight and the mass distribution.

Moving parts are a nightmare for reliability. Every moving part is something that can cease up and go wrong. It's a motor that can fail and gears that can get jammed.

JWST has two key components that involve a lot of moving parts:

1. The mirror. Hubble was smaller enough to be deployed fully constructed in the Space Shuttle so didn't have to deploy in space. JWST's mirror is 3-4x larger an there's no current launch vehicle that could launch it fully assembled. That's why you have all the beryllium hex mirrors that had to deploy the mirror once in orbit. These motors, actuators, assemblies, etc need to be incredibly precise and reliable; and

2. The heat shield. JWST has to be incredibly cold to operate (5K IIRC). The only way to get rid of heat in space is to radiate it away. The heat shield separates JWST from the Sun, the Earth and Moon (each of which reflect enough light to interfere with operations). The shield is several layers and it's large, like tennis-court sized. Obviously this too had to be deployed in space.

There were like 10 technologies for JWST that had to be invented to make the mission possible. That's less than ideal. It adds to the cost, the complexity and the timelines.

In hindsight it probably would've been worth having a stepping stone between Hubble and JWST that proved some of these technologies in a cheaper and less risky way, probably with a smaller mirror. But here we are.

View on HN

A while back I raised a bit of a furor here saying that a duplicate could be made and launched at a tenth of the cost. A lot of people said I don't know what I'm talking about, that little money would be saved.

But it seems patently obvious. After all, 10 technologies don't have to be reinvented. No research would need to be redone. No test rigs would need to be redesigned and duplicated. And on and on.

The most bizarre argument against building a duplicate was there wouldn't be anything extra worth looking at. Yet I watched the NOVA episode on the scope last night, and everywhere they look where we thought there was "nothing" turns out to be crammed with 10,000 galaxies and stars.

We could probably deploy 100k of them and still see only a tiny fraction of the universe.

Taking pictures the level of the first image released, it would take about 3700 years for JWST to image the entire sky.

I take your point, but it does seem to have actually worked.

Obviously a great deal of the cost also came from making sure it would work, because there wouldn't be another.

What if 10 were built, each with only a 10% chance of success? What would that have cost? After all, it doesn't need the expense of being man-rated.

What is the measure of success though?

Successful launch and arrival at the observation point? The 6 month setup period before observations can be made?

I contend that success here is a full mission that yields science data over decades of observation. If we cut down the acceptable error rate so we can launch early, how does that impact longevity?

I think the question is, imagine we built 10 — and got an outcome like:

2x — failed to deploy, mission lost

4x — early operation error, 6mo lifetime

3x — lower performance, 3 year lifetime

1x — mission successful, 10 year lifetime

…do we get a better deal building them with larger faults, at a lower cost?

A lot of expense is in developing technologies, assembly tooling, and test rigs — all of which is easier if we don’t need them to be as assured because only 1 in 10 needs to succeed.

Right. And if they are launched serially, you've got a chance to correct mistakes in the previous launches. Odds of success increase with every launch.

Yeah, makes more sense when I think about it like that. Thanks!

> What would that have cost?

No idea. Do you? Genuinely interested, particularly regarding methodology. Not intending at all to be insulting.

Look at SpaceX's rockets. They cut costs by what, 10x? over NASA's? A part of that was not trying to build 100% the first time, but to accept failure and iterate.

My dad told me that Pratt&Whitney made the most reliable aircraft engines by putting them on a test stand and running them at full power until they broke. The engineers would figure out why it failed, redesign the part, stick that on the engine, and continued running them at full power.

It's straightforward, inexpensive, and it works.

Could it be, that iterating fast through additional failures may be harder to finance with public funds, because the general public hasn’t caught up with the recognition of failing early and often being a good thing?

Government programs fail all the time, and they just get a budget increase. Hire the salesmen who accomplish that.

lol - you do have a point there!

Surely you can see that the P&W approach is only going to discover a subset of problems that will affect the engine in the wild. For example, engines don't run at 100% power during the full flight, and they go through heating and cooling cycles. It also doesn't address failure modes due to manufacturing problems specific to a single engine- for example, turbine blades are manufactured with serial numbers and you can go back and get detailed process and QA for that specific item to understand what went wrong and why it failed and how to not do that during manufacture again.

Then there's all sorts of complex failures that aren't addressed by single engines: " Prior to this crash, the probability of a simultaneous failure of all three hydraulic systems was considered as low as one in a billion. However, statistical models did not account for the position of the number-two engine, mounted at the tail close to hydraulic lines, nor the results of fragments released in many directions. Since then, aircraft engine designs have focused on keeping shrapnel from puncturing the cowling or ductwork, increasingly utilizing high-strength composite materials to achieve penetration resistance while keeping the weight low"

(I'm not disrespecting P&W- I'm sure they have more tests than just "100% power until it breaks, fix and repeat")

> Surely you can see that the P&W approach is only going to discover a subset of problems that will affect the engine in the wild.

Keep in mind that my former job was designing gearbox parts for the Boeing 757. This included doing the math, and devising a test plan. I've spent a lot of time on "what could go wrong" scenarios in the real world.

Also, when I prepare slides for a coding presentation, the implementation code for a concept gets trimmed way down to what will fit on a slide.

What is the timescale you are thinking of for 10% chance of success? 10% first light success is different than 10% 10-year survey success.

There’s physically not enough infrastructure (clean rooms, testing facilities, vacuum chambers, etc…) nor skilled manpower available to NASA to be able to build more than one in parallel, so that would add to the cost significantly.

What's being done with that infrastructure (clean room, testing facilities, vacuum chambers, etc..) right now?

Nothing?

Of course, the sensible thing to do is to build the test equipment, procedures, train the testers. Then test #1. Then test #2. Then test #3. That's what everybody does.

The cost of the Saturn V rocket was amortized over many launch vehicles, despite a host of new technologies that had to be developed for it, despite much of it being hand-built.

But the cost of grinding the mirrors?

Consider the cost of designing the mirrors, designing a machine to grind the mirrors, testing the machine, and verifying the grind of the mirrors.

All that adds to the cost of the first mirror, and adds $0 to the second.

But the grinding machine costs (which is significant if you have 10 of them) and the grinding process takes a lot of time and cost (if you have 1 machine x 10 mirrors).

I don't think these NASA/JPL guys are quite as dim as you seem to suggest (but you have more info) and they may have done a little cost/benefit analysis before embarking on the project.

From their statements, no, I don't think any cost/benefits of making a twin were done. In particular, none of the respondents wrote anything about what the cost of R+D was relative to the manufacturing cost.

BTW, I am not suggesting they are dim. But one can be the finest physicist in the world and not be familiar with cost accounting and manufacturing.

Other telescopes are being built, at least at places like Goddard SFC. Probably WFIRST aka Nancy Roman Space Telescope) there. Other facilities (Northrop Grumman) would be competing with NatSec/OGA instruments.

We already had the discussion. Could you link to it? Is it worth having it again?

https://news.ycombinator.com/item?id=30730726

Olbers' Paradox[0] resurgent.

[0] https://en.wikipedia.org/wiki/Olbers%27_paradox

>>A lot of people said I don't know what I'm talking about, that little money would be saved.

Those are the ignorant ones.

It isn't quite a "Those who know don't speak and those who speak don't know" situation, but this is just blindingly obvious to anyone who has done any R&D to manufacturing and risk assessment. Heck, even just having a duplicate on the ground to debug could save the mission (since there isn't one, let's hope it doesn't come to that).

On one-off projects of any size, the design, prototyping, testing, & refining the design just overwhelm the cost of fabricating the final parts — and they do it by orders of magnitude. Just for the carbon fiber parts I work in daily, the initial R&D test program for a sizeable (scale of 1 m^2) part might cost $25K, the first mold $12K, the first part sells for $3K, the second part $2K and the fifth part 1.7K. To get to volume production in the 100s, there's probably another dev program & set of molds, and the 300th part out the door might sell at $1200.

When I worked in engineering at Boeing, the cost of a forged part was the cost of the tool&die machinist making the die. The incremental cost of doing the actual forging was a rounding error. The dies do wear, and the parts get larger and larger until they're out of spec and a new die is sunk.

First rule in government spending: why build one when you can have two at twice the price? Only, this one can be kept secret. Controlled by Americans, built by the Japanese subcontractors.

There should be a movie with this plot.

Never now if people are joking saying that but oh boy!

Yeah it would make for a great twist, like say if some crazy terrorist decided to blow it up.. “don’t worry we have another”

Only if there’s windsurfing with dad

The plot of the movie "Contact".

Wanna take a ride?

Didn't we do that with hubble? We built 1 hubble, but many more "hubble-like" spy satellites and found out about them when they were donated back to nasa to put toward civilian use.

Hubble's design borrowed various elements, including the primary mirror, from existing KH-11 spy satellites as a cost saving measure.

The satellites which were donated to NASA by the NRO where likely leftover from the abortive Future Imagery Architecture program which was unrelated to Hubble.

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.

I 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.

The obvious number to make is 5; currently we only have one at L2. What about L1, L3, L4 and L5?

The advantage of L2 is that is stays in Earth's shadow at all times. None of the other Lagrange points have this benefit.

Why does it need the sun shield, then?

Ask the moon why during an eclipse it isn't completely shadowed out. It's much closer than L2

Good answer! Although the Earth is also much larger than the Moon.

And the JWST is much smaller than the moon

Earth 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

Thank on that, and I stand corrected.

So we're back to one for each Lagrange point?

Spitballing, there might be issues with having one at L1 or L3, but I'd love to have one at L4 and L5.

* L1 is between the Earth and Sun, so orienting the sun-shield toward the sun would result in the cold-side being heated by reflected light from the earth. It would also have access to the same patch of sky as at L2 for any given time of year, so there wouldn't be an advantage to having it at L1 as opposed to having a second telescope at L2.

* For L4 and L5, there's a ± 60 degree orbital offset relative to Earth. That gives access to a different part of the sky at any given time, but over the course of 6 months, both locations could access any part of the sky. There's a potential for time-correlation studies, where an observation at L2 and L4 are made at the same time, with the ~150 million km between them serving either as the base of a triangle for parallax measurements or as a known distance for measuring speed of travel between the

  That said, I'm not sure how useful those would be.  The parallax measurements could be done by ground-based telescopes simply by waiting a few months between measurements, and the speed of travel measurements would primarily provide a measurement of the index of refraction inside the heliosphere.

* L3 is opposite the Sun from the Earth. This would have the best baseline for parallax studies, but would have communication issues as any direct line of sight would be blocked by the sun. There would need to be relay satellites in order to communicate back to Earth, though previous L4 and L5 satellites might be able to serve this purpose.

Overall, I'd guess the biggest scientific bang for the buck would be to load up more telescopes at L2. The proposals for the first 12 months of observations totaled about 48 months of observation time [0], so most of the proposals were rejected. The biggest advancement I can see would be to simply have more telescope time overall.

[0] https://www.stsci.edu/contents/news/jwst/2020/jwst-cycle-1-g...

L2 means that the Earth and Sun are roughly in the same direction. JWST orbits at a distance around L2 such that it's actually never in the shade, so it doesn't need energy storage and thermal controls other than constant sun in a constant direction.

It has an orbit around L2 of roughly 0.8 million km. L2 is about 1.5 million km from Earth. The moon is only 0.36 million km from Earth.

L3 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.

What are the odds of two objects at L2 colliding? The telescope does have maneuvering capability, as L2 isn't stable.

The odds are astronomically small. ESA has at least 5 other missions aimed at L2. [1]

[1]: https://www.esa.int/Science_Exploration/Space_Science/Hersch...

> astronomically small

That's what I supposed.

They 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

> 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.

yeah, um, i didn't really mean that with any seriousness, like, at all

"Space," [the Hitchhiker's Guide] says, "is big. Really big. You just won't believe how vastly hugely mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space."

Even L2 is big. I'm sure you could 10s or 100s of kilometres either side of "L2" and still have the same benefits as Webb has. In fact it you have enough objects there, and cooperate, they could effectively orbit each other.

It will be so cool, if eventually we could deploy telescopes on other plants, like in Ad Astra.

If 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)?

It'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.

It 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.

It'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.

There's already a telescope at L1. It always points at the earth.

https://epic.gsfc.nasa.gov/

The 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...

[2]: https://space.stackexchange.com/questions/57463/what-is-the-...

I 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.

I always thought they should have planed to build and launch two of them in case something happened to the first(unlike hubble we cant get people out to L2), if you are building one, then building the second is relatively cheap.

The universe at this distance seems very homogeneous. Won't looking at different parts of the sky just yield more of the same? It seems like you'll just see the same things over and over again in any patch of sky.

One of the hypotheses that can be tested better than ever by JWST is precisely this: Is the very-distant universe homogenous?

Modern cosmology assumes-so, but it need not be true.

Strongly agree, except that "assumes" can be unpacked a bit. There are various reasons why cosmologists think the distant universe is homogeneous, and some of them (not all) are closely based on evidence, most notably the approximate homogeneity of the cosmic microwave background, which is (in a sense) further away than anything the JWST can see.

JWST is not particularly well suited to testing homogeneity. Survey telescopes that observe a large fraction of the sky are much better suited to that task.

Homogeneity has been very well tested out to a redshift of a few by surveys like the Sloan Digital Sky Survey and the Dark Energy Survey, each of which have observed thousands of square degrees of sky (there are about 41k square degrees in total). And as another commenter notes, the CMB (at redshift 1100) is homogeneous (to one part in 10k).

We would like that to be true, but it seems like it might not be.

https://en.wikipedia.org/wiki/Axis_of_evil_(cosmology)

https://en.wikipedia.org/wiki/CMB_cold_spot

You got much more detailed explanations in that thread. It simply doesn't scale like that. These are extremely bespoke systems, and the entire process is gated on vendors and facilities that are both unique in the world and under high demand. There is simply no way you get a 2nd unit at the kind of discount you're assuming.

I didn't those explanations compelling. The cost of the design and development of the JWST was surely enormous, along with the design and construction of test facilities. None of that needs to be repeated for #2.

Just for fun, buy two IKEA flatpacks for, say, bookshelves. Build one, then the other. I bet you spend half the time building the second, even though you're doing exactly the same thing, by hand.

Reminds me of when in March 2020 I was also told I didn't know what I was talking about when I pointed out how a Covid vaccine could be made available in 6 months rather than the conventional 18 minimum times. The vaccines were available in 7 months.

The airplane I worked on the design of, the Boeing 757, would have cost at least 100 times as much per-plane if it was a one-off design.

I assume the 757 was designed to be produced in bulk.

It's not clear to me that designing something that needs to be assembled successfully once vs twice vs 10 times doesn't introduce some more cost tradeoffs in itself. Just around tolerances and yield even, how many pieces are required to be made to give one complete set of parts that all work together vs 10 complete sets that all work together. I could see some extra pain and assembly from having to get more permutations of part variances all working together and validated. A while back, at least, a lot of the testing processes for space components were VERY manual so you'd either need to invest more for automation or accept linear costs on all the extra production/verification.

This is partly quibbling over trivial details - I would imagine the savings is closer to 50-75% than 90% - but at a certain point those differences in tens-of-percentage points are lots of billions of dollars.

Here's the real kicker to me: why spend even an extra 10% up-front before even deploying one of them? Why not spend the marginal costs on building an additional unit only if the first fails? Then you can learn from the failure too? And if it works the first time, those billions can be spent elsewhere instead.

As one respondent here wrote, the "why" is that due to the long time it took to develop the JWST, much tooling has been scrapped and the teams who did it have dissolved. You lose a lot of the cost savings if you don't build #2 right away.

You're right that the 757 was meant to be built in bulk, and hence one has to pay attention to tolerances so the parts are interchangeable.

> Reminds me of when in March 2020 I was also told I didn't know what I was talking about when I pointed out how a Covid vaccine could be made available in 6 months rather than the conventional 18 minimum times. The vaccines were available in 7 months.

Conventional vaccines are sterilizing, have good safety records, and protection in years, or decades.

This "vaccine" is none of above.

These MRNA "vaccines" required a change in the definition of a vaccine, and have atrocious safety records.

The new Novavax vaccine [1], which is a conventional vaccine, may prove to have much longer effectiveness period, and not require boosters every 3 months. It also took much longer to develop.

[1] https://www.novavax.com/science-technology/recombinant-prote...

The vaccine probably saved a million lives in the US alone.

It's great that newer, vaccines are being developed. But in the meantime, the Novavax vaccine is not available. I'll take the one that is available. I'm not really interested in dying waiting for the perfect vaccine.

> Conventional vaccines are sterilizing

Many vaccines do not provide sterilizing immunity. Just to give one random example: flu vaccines do not provide sterilizing immunity.

> have good safety records

The various SARS-CoV-2 vaccines have very good safety records. They've been administered to billions of people, and the rates of serious side-effects are on the order on one per several hundred thousand - orders of magnitude lower than the rate of serious complications from infection.

> The new Novavax vaccine, which is a conventional vaccine

I don't know how you're defining "conventional" here, but Novavax also uses a new vaccine platform.

> The various SARS-CoV-2 vaccines have very good safety records. They've been administered to billions of people, and the rates of serious side-effects are on the order on one per several hundred thousand - orders of magnitude lower than the rate of serious complications from infection.

I know 2 people with severe adverse events from the vaxx.

Considering how many vaccinations I have received my life due to military service, that is an order of magnitude worse than any vaccination, ever.

“Why build one when you can have two at twice the price” ~ S.R. Hadden. Contact

A tenth the cost? No. Half the cost? Possibly but even that is a stretch. A huge amount of the work effort (and funding) would have to be repeated. All the testing, validation, hardware-specific characterization and calibration, troubleshooting, and attendant analysis. Not to mention partial redesign since many of the parts used are no longer produced and the tooling long gone.

Source: just my perspective after 20 years working on space systems.

> tooling long gone

But of course. I meant before that happened, i.e. planning to make some siblings.

Other elements that drives substantial cost is the move to push things to commercial industry to do fabrication, and their internal training gaps...

Case in point: When there are 3 people on a planet that know how to create a specific sensor, and they happen to be NASA civil servants, JPL employees, Professors in Academia, or from a boutique non-profit like Aerospace or Mitre...in many cases the govt will decide to push the fabrication to commercial industry to create it, instead of the elite teams that created the most recent groundbreaking sensor.

This causes huge cost overruns as the commercial teams fumble around [1] and in some cases, even get paid despite dropping a satellite [2]

One of the funny fixes to this for NPP, was assigning a government "hall monitor" experienced in safe satellite testing to oversee test operations, and gig them for every infraction of safety protocols.

[1] https://www.defensedaily.com/npoess-has-more-than-1-billion-...

[2] https://spacenews.com/another-factory-mishap-damages-noaa-n-...

What a good thought. I'm sure a second one would have been much cheaper than the first one if they'd built it at the same time. Now, many of the teams and facilities that did the work have dissolved back into the academic and industrial aether and would need to be reformed. But, as you say, they'd have less research to do a second time.

not at the same time, after the first one has been verified.

basically after the manufacturing, calibration, tuning, assembly, etc. techniques have been perfected to the required degree

plus, it would make sense to try to repeat this a few times always trying to 80-20 it. (I mean intentionally trying to "half-ass" the next iteration. spend less on it than on the previous one, and try to get the best out of that budget - with the same tech of course.)

the big problem is that ... it doesn't make much sense to do this. JWST delivers the data for the science it was intended and ... for the new questions that we'll raise we'll probably need some even more specialized observatory.

> In hindsight it probably would've been worth having a stepping stone between Hubble and JWST that proved some of these technologies in a cheaper and less risky way, probably with a smaller mirror. But here we are.

That doesn't really seem to be in NASAs DNA, to do smaller incremental improvements. Instead, they really upgrade big, in chunks with long time in-between. I don't know why they do it, but in their webcasts it been mentioned a couple of times related to James Webb.

My (minimally educated) guess is the funding model: they need to give lots of congresspeople stuff for their districts. Big projects provide much more stuff and are easier to sell if everyone can get a piece at once rather than Alabama getting this one piece one year and Colorado getting this other piece the next year.

Seems a reasonable guess, but I'd hope that if that were the main stumbling block then it wouldn't be too hard to still sell it as a multi-state project that's also multi-stage, either sharing the work at each stage or signing off up front which stage goes where.

Remember that for congresscritters, it's infinitely easier to cull $20m from NASA's budget than $5 from the DOD.

Also remember that a non-trivial amount of Americans believe the moon landing was faked, or that the earth is flat and NASA is part of some conspiracy. Or that a certain political party has spent literally three decades saying "the nerds at NASA are lying, there is no global warming" and you might start to understand the complete lack of political will to give NASA the funding to do even literally the basics.

We have more ideas for telescopes than money to build them. So to get funded, a new telescope needs to be a substantial improvement over what already exists: 10x or more, typically.

There’s typically only a chance to build a flagship every ten years or so.

I like that idea of breaking the job up. Seems like the heat shield could have been it's own seperate launch that just provides the platform, and a bigger/better one, that the scope comes along later and attaches to.

Maybe the main reflectors could be like that too. One or more packages that are just the reflector, maybe not even all of it but just sections.

I think the adjustable array of smaller sections is simply necessary to get and maintain the focus anyway, so the adjustability is not an expensive extra.

Hubble actually went up with a botched main reflector and couldn't be corrected directly. The replacement secondary optics was only a terrible patch, and really only even possible because the scope is within human reachable space to do that level of heart surgury in-situ like that.

So if the reflector has to be adjustable anyway just to work at all, then it's not a crazy extra fundamentally, and only a bit extra to have the pieces be able to be shipped individually and self-assemble on site. The inherent adjustability which was required anyway, allows for the inherent inaccuracy of connecting two parts vs one solid part.

With 2 or 3 or more smaller component missions, each project becomes not only less critical and more tolerable of a failure, but also less complex and less likely to suffer a failure.

And it seems like this project does have at least 2 or 3 natural major building block boundaries. The shield vs everything else is one for sure. That could be turned into a platform, maybe for more than one instrument added or replaced over time, and could maybe supply power as well.

Then maybe also the main reflector vs the actual instruments. And the main reflector itself could be in simpler discrete sections instead of having to fold and unfold.

With really cheap space access you can do assembling in space. No motors, just plain old human hands in space.

Tennis court sized shield? Take it up like a long and precious Persian mat and let the humans rig the thing in orbit.

From there, attach fuels tanks and you are good to go for your insertion burns.

My understanding is that not only did the heat shield have to unfurl, but construct a particular geometry such that it created a waveguide to channel the light out the sides and avoid too much entrapment or too slow of transport. Being the material it is, there’s also no way to model exactly how it will unfurl so it’s difficult to develop. Just the metrology effort on the ground to validate the shape was quite great.

The sun shield is held up as this big challenge but I don’t think they do a good job explaining why it was so difficult.

There’s a popular YouTube whose father was a metrologist working on the sun shield. https://youtu.be/Pu97IiO_yDI

> These motors, actuators, assemblies, etc need to be incredibly precise and reliable

Is it impossible to build to a lower level of reliability then have humans available to fix/adjust things in orbit?

Then once it's fully assembled in place, move it to its final location?

Don't we also have 60 years of experience with motors, actuators, and assemblies in space?

Some of the parts are so sensitive them weren't deployed until the telescope got into its final position at the moon's L2 Lagrange point. If you had humans assemble it in orbit it would still have to undergo the stresses of acceleration to get to the L2 Lagrange point.

I don't think that's possible because, if I understand correctly, many of the parts need to be adjusted periodically to maintain accuracy. It's not a set-once-and-forget type situation. Those parts need to be able to make extraordinarily precise adjustments repeatedly for the life of the mission.

"Aligning the primary mirror segments as though they are a single large mirror means each mirror is aligned to 1/10,000th the thickness of a human hair. This alignment has to be done at 50 degrees above absolute zero! [0]

[0]https://www.nasa.gov/topics/technology/features/webb-actuato...

Yes and no. It raises a bunch of questions/problems, wuch as:

1. Where doe the telescope deploy? Ideally in LEO so you have a chance fo fix things but then that complicated the launch. You have to park in orbit and restart th eengine at a later point. AFAIK JWST didn't enter a parking orbit so would've required additional fuel. That might not have been possible;

2. What if the launcher itself fails? Do you want to have the capacity to launch another rocket, have it rock with JWST and then go on? If so, that's a whole new level of complexity and a set of problesm you have to solve as well as things that can go wrong;

3. If you look at the flight plan there are a bunch of turns. How would the G-forces affect, say, the deployed heat shield?

4. JWST actually had to rotate during launch to point the instruments away from the Sun so as not to destroy them. This already added complexity. Doing this with the deployed spacecraft would probably only further complicate this.

The Webb is orbiting the Earth/Sun system at a Lagrange point. It's not in a normal Earth orbit. Astronauts have not gone that far from Earth

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