So do I.

I see. Apparently, the problem has just reappeared itself on my side as well. This actually happened when I received a forum reply notification from you guys, after which the purple dot has once again refused to disappear. Ok, thanks for your responses guys. :)

I was looking at reviews for NVMe drives for a while before finally deciding on a Kioxia Exceria Plus 1TB (not as obscure as it sounds, just Toshiba with a new name). I ordered it a few days ago, but I see I bought the Exceria Plus G2. It was a lot cheaper than the non-G2, but I can't find any difference in specifications. Did I buy a kaptop-drive or something, or will it be okay? I see there's a difference in form factor, but as far as I understood, the M.2 slot is mostly universal.

A lot is riding on the successful deployment of the JWST, easily the most complexed robotic satellite ever to be launched, and one of the most important, in terms of the science it can do.

Not only is it massive and complicated, but it has to be deployed at the L2 Lagrange point, well beyond any hope of a service mission. (Hubble has been serviced five times so far.*)

To unfold, it has to perform about 140 distinct mechanical movements, like a transformer, all have to work perfectly first time, and it's never been done before.

My question:

Wouldn't it have been much better to assemble and test the JWST in low earth orbit before boosting it to L2? They could literally have built it on the side of the ISS, with all that infrastructure available. And it could have been bigger, better and simpler (cheaper?) as a result. So why send all the eggs in one basket and hope it works first time? There's a lot to lose.

*All shuttle missions. No more are planned, but if the JWST fails, it could happen.

Why are all probes assembled on Earth and then fired off? There's no system to assemble them and launch from orbit yet. And I gather that JWST needs to be away from Earth to properly "see", since it focuses on infrared, so testing in LEO wouldn't really work either.

The ISS was assembled in LEO. Assembling a lightweight structure like the JWST should be simple by comparison.

"JWST needs to be away from Earth to properly "see", since it focuses on infrared, so testing in LEO wouldn't really work either." - That's not true.

We have infrared telescopes in orbit already, and here on the earths surface. It's just a matter of sensitivity. The JWST has a large sun shield installed that protects it and allows the instruments to run at a very low temperature. The only problem would be that when the shade is facing the sun, sometimes the rest of the telescope is facing the earth, a source of IR. This of course could be compensated for by not testing it while it's pointing at the earth.

The primary reason to assemble it in orbit is to avoid the need for the robotic unfurling mechanisms, which are fragile, complicated and unnecessary points of potential failure.

I'd say that joining together a handful of large modules is actually easier than assembling a single smaller object.

Anyway, this is what NASA has to say about it:

"Why not assemble Webb in orbit?
Various scenarios were studied, and assembling in orbit was determined to be unfeasible.

We examined the possibility of in-orbit assembly for Webb. The International Space Station does not have the capability to assemble precision optical structures. Additionally, space debris that resides around the space station could have damaged or contaminated Webb’s optics. Webb’s deployment happens far above low Earth orbit and the debris that is found there.

Finally, if the space station were used as a stopping point for the observatory, we would have needed a second rocket to launch it to its final destination at L2. The observatory would have to be designed with much more mass to withstand this “second launch,” leaving less mass for the mirrors and science instruments."

Also:
"Why is Webb not serviceable like Hubble?
Hubble is in low-Earth orbit, located approximately 375 miles (600 km) away from the Earth, and is therefore readily accessible for servicing. Webb will be operated at the second Sun-Earth Lagrange point, located approximately 1 million miles (1.5 million km) away from the Earth, and will therefore be beyond the reach of any crewed vehicle currently being planned for the next decade. In the early days of the Webb project, studies were conducted to evaluate the benefits, practicality and cost of servicing Webb either by human space flight, by robotic missions, or by some combination such as retrieval to low-Earth orbit. Those studies concluded that the potential benefits of servicing do not offset the increases in mission complexity, mass and cost that would be required to make Webb serviceable, or to conduct the servicing mission itself."

Thanks Cavalary. Literally a frequently asked question ^_^

Three reasons then. ISS doesn't have the capability, space debris, thrust restrictions.

-The thrust can be tiny if you don't mind the extra journey time. It could get from the ISS to L2 on an Ion engine. And since the mirror no longer needs to unfold, it could be structurally much stronger just by design without needing to add weight. Don't forget, you are losing the weight of the hinges, cables, sliders, guides and motors required for robotic unfolding.

-Space debris is no more likely to hit the JWST than it is to hit the ISS or Hubble, and if it were damaged before launch, it could be fixed.

-The capability is, as always, provided when it's needed, by specialist equipment and training in the pool.

I'm not convinced.

Not sure how accurate this is, and it's an old page, but a quick search would say that escape velocity from the ISS is 2.9 km/s. Highly doubt a ion engine can offer that. It's great for sustained powered flight over long distances in space, but for launching, even from orbit, I'd say not a chance. And something that would provide that escape velocity will also obviously add to the stress, as they say. And launching with the mirror unfolded strikes me as adding a huge amount to the risk of damage.
And at least the ISS is designed to deal with at least the small, regular space debris it's likely to encounter.
As for that capacity, depends on what it'd entail, how much room it'd require, how many transports, what costs...

The limiting factor of Ion engines is their low thrust, and as a result, the small acceleration. It would take time, but 2.9 km/s DeltaV and more is easy*. Chemical thrusters would work too.

An 'assembly in orbit then boost' profile would require the telescope to be designed a little differently, with structural strength along the thrust line, but there's absolutely no reason why, just like many other instruments that are already out there, it wouldn't be practical.

Also, if an Ion system were employed, it would be possible to keep enough DelaV available after deployment, to bring it back for servicing, in ten years or whatever.

"how much room it'd require, how many transports" - Dude. The whole thing is going up on one launch. Why would an assemble-in-orbit kit be much bigger?

*"Spacecraft powered by these thrusters can reach speeds up to 90,000 meters per second"

One question:

* Why are web browsers (Chromium in particular) so disk intensive? (This becomes noticeable if you're using a Raspberry Pi with an SD card to browse the web, or even with an external HDD (can actually hear all the disk accesses).)

I know Firefox saves your browsing state regularly so that it can reopen most of the tabs and windows where you were in case you lose power or something. This function can be shut off in the settings. I am sure Chrome has similar functions but it also uses a lot of RAM so will start swapping to the hard drive sooner. Not sure how similar the settings in Chrome and Chromium are as I never use the former and rarely the latter.

Which do you prefer, messy sketch lineart or clean lineart? Also, if you can, please explain the reasoning behind your preference. Thanks!

Clean lines always, it invokes the artist's control over the visuals and looks less like litter.