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Comment by skurtcastle | Hacker News Reader

That's awesome to hear.

I'm excited for Dec 22nd when the James Webb launches. Crossing fingers big time.

I’m looking forward for some of the photo series NASA probably has planned, like a simultaneous observation of the same object with Hubble and Webb.

30 days off terror for it to transit and unfold. Scary times!

Even longer for it to actually power up and start "working." Really excited for it, but feel like something akin to this hubble issue happening with the JW would be disastrous.

What's the timeline to being fully operational?

Roughly 6 months after launch for all systems to cool to operational temperature.

More like JFCT

It'll be a Starship mission with astronauts to go work on it at L2 in 2023/4 then.

Unfortunately, even if we do develop the capability to get astronauts out there, the Webb is constructed with a lot of adhesive and layered components and is basically impossible to service in space.

I think the best we could hope for is maybe being able to drill into the liquid helium tank and refill it - which is the ultimate determinate of its useful lifetime (that and propellant, but I'm led to believe the liquid helium will run out first).

Probably a moot point though: by the time we can get people out to do such an operation, I suspect a reduction in launch costs might lead to a much cheaper space telescope you could just drop off instead.

There is no consumable liquid helium. Past space telescopes have used consumable coolant, but JWST has a closed refrigeration system to cool the one instrument that requires active cooling.

If all goes as planned, the limiting factor is propellant. And the propellant tanks have the ports for on-orbit refueling, in case there is ever a desire to develop a robotic servicing mission for the task.

Huh...seems like this was misreported in a bunch of places, but you're right. It is in fact closed loop on cooling.

And not just disastrous for James Webb, disastrous for the possibility of future funding of space missions in the near future. Congress would be much more hesitant to fund anything as large as the James Webb in the future if it failed.

Not if China starts funding such things as many in the US Congress would not want China to have more advanced assets in orbit and would authorize funding to make it work.

How much of the cost is the R&D vs. actual construction and launch?

(In other words, how expensive would be fixing an issue and trying again actually be?)

It's hard to say, but for the JWST the design and R&D seems to have been the easier part [1].

In general it's uncommon to build a replacement satellite after an issue. Either you make a backup from the start, or you start over after failure. Making a one-off component often isn't all that much simpler just because you've already done it once a decade ago (and some parts of the JWST should be about a decade old by now). And if you commit to doing that all over again, might as well update the entire design to new capabilities and requirements.

1: https://space.stackexchange.com/questions/48902/are-there-an...

NASA could have built two or more as backups, as most of the cost was in R&D it would have been (comparably) cost effective to do so.

If the R&D is done anyway, why not just wait and build a second telescope if the first one fails? I don't see why that would be any more expensive than building a backup ahead of time, and it means if the first one fails due to an undetected design flaw, they have a chance to correct it.

It’s cheaper to build two at the same time than shutting down production for years and trying to build another one. Tooling doesn’t last forever, and the process and skills required to build one can help you build the second one cheaper. But if you wait, that knowledge is often lost. For example, we have no way to build a Saturn V rocket today even having spent R&D and NRE decades ago.

I don't see why not. They did the same exact thing in the movie Contact.

Same reason NASA built the Space Shuttle Endeavour with spare parts left over from the others, instead of building it from scratch. People move on with their lives, and the facilities that manufacture these things do too. Assuming everything was well documented it should be possible to recreate the tooling and train new people, but that's much more expensive than building two in the first place.

The vibration incident was solved?

This launch is going to be so scary as it represents the scientific promise and investments of a generation.

The fixed fairing has been successfully launched twice.

Yeah, vibration turned out to be a non-issue, everything is go for launch.

*if

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