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Comment by dghughes | Hacker News Reader

When you get some new device and it says leave plugged in for 12 hours to charge first before using, but you don't. I have to wonder with JWST I bet there is a desire to try to have a sneak peek. But I guess calibration is automated so no way to bypass rules. And way too much to lose if something goes wrong ~30 years and $10B.

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As I understand things, without the calibration there would be 18 images overlaid each other with some shift in between. Each mirror has quite some degree of freedom, so they have to be aligned to each other until you have one sharp picture. Right now you might see each star 18 times in the picture. Probably they have taken some test images to check the operation of the cameras, but thats about it until a good degree of alignment is achieved.

I think its much more than the sunk cost we would lose. There would never be another.

Why not? You mean JWST specifically or some reason there can’t be a similar telescope?

The Nancy Grace Roman Space Telescope is upcoming. It's mirror is 'only' the size of the Hubble's [1]

[1] https://roman.gsfc.nasa.gov/

So JWST is so massive that it’s unlikely anything like it will happen again in our lifetimes?

If Starship happens, I’m guessing JWST-class telescopes become much more approachable.

I’d imagine launch cost is a fraction of the cost.

JWST is immensely complex.

I believe much of the complexity comes from having to fit it in the nose cone of the Ariane 5 rocket. With a much larger launch vehicle, you can make some different design trade offs to maybe reduce that complexity.

I guess it's a "should we build one expensive one and make sure it works, or ten cheap ones and see how many of them make it?" thing.

I very much doubt you can build a cheap 6.5m gold plated mirror aligned to a standard that it can get clear images of the farthest corners of the universe, but that can also survive a rocket launch.

Launch cost is actually a _significant_ fraction. Even more so, because a lot of the complexity arises from design and systems to get things right on the first try, since launch costs are so prohibitive.

Put another way, if launch costs were cheaper, it would also have been cheaper to design and build the telescope.

JWST is expensive for two reasons. One is the giant heat shield, as it is an infrared telescope. There is no real way around that. Secondly it is the space in the rocket, the mirror (and everything else) had to be folded to fit into the rocket. Getting this folding mechanism to reliably unfold was the big challenge - if anything had gone wrong, there would have been no recovery.

With its 8m diameter, Starship could house larger telescopes without folding. Considering how cheap a Starship by itself is, the Starship itself could be the permanent housing of a large telescope. It would just need to jettison the tip to expose the telescope inside.

So the constraint was physical volume and not really weight?

An international team including NASA has plans in development for a follow up to JWST called The Large Ultraviolet Optical Infrared Surveyor (LUVOIR) [1]. There's two versions, LUVOIR-A with a 15m primary mirror and LUVOIR-B with a 8m primary mirror (compared to JWST 6.5m primary mirror) [2]

From the Wiki "LUVOIR would be able to analyze the structure and composition of exoplanet atmospheres and surfaces. It could also detect biosignatures arising from life in the atmosphere of a distant exoplanet."

Proposed launch date 2039 (quite a wait).

[1] https://en.wikipedia.org/wiki/Large_Ultraviolet_Optical_Infr... [2] https://upload.wikimedia.org/wikipedia/commons/a/aa/Comparis...

Damn, makes me realize my mortality

I often wonder with JWST, wouldn't building another cost way less than $10B? We have detailed blueprints, the software, etc.

First rule in government spending: why build one when you can have two at twice the price?

From the movie Contact. This is probably the sentence which I will never forget and I very often think of if I need to justify buying a backup of anything.

Also if you weren't expecting it, awesome plot twist.

That later scene "...they're alive..." gave me chills.

Clever little end note on the recording.

Fantastic film.

Not only is this a precision instrument, the mirrors are guaranteed to be possible to align within a nanometer once deployed, it's going into space on top of a giant controlled explosion.

A large part of the cost is the manufacture, testing and qualification of the parts and assemblies. Things that doesn't really scale at low numbers.

I'm sure there's a flatsat somewhere, but probably without the optics or sunshield...

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