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The James Webb Space Telescope has passed the final mission analysis review

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Re: The James Webb Space Telescope has passed the final mission analysis review

#281

Post by thereddaikon »

Gustomaximus wrote: post #275
arp242 wrote: post #259

Earlier quoted context omitted.

According to the NASA website there is fuel for 10 years, and the five years is just the "minimal" mission time for which it's tested. https://jwst.nasa.gov/content/about/faqs/faq.html#howlong

Question if anyone knows: ~9.5 years any reason to not push it out of orbit into space and continue to get signals back for years longer as it floats off? Like the voyagers?

JWST isn't a probe like Voyager. It's job isn't to go to other worlds and see what's there. Its a space observatory. It does exactly the same job a telescope on earth would do, just in space. The reason why is to avoid light pollution and the interference from earth's atmosphere.

So that fuel isn't used for going places, its for aiming the telescope and keeping it steady. Once the fuel is gone it can no longer control where its pointing. If you cant aim a telescope then its useless.

Re: The James Webb Space Telescope has passed the final mission analysis review

#282

Post by vimacs2 »

gccs wrote: post #264
wolverine876 wrote: post #220

Earlier quoted context omitted.

> This documentary was produced by Northrop Grumman Corporation -- the builders of JWST under a NASA contract. Is it promotional material?

Propaganda

Considering that they themselves made the telescope, do you consider all forms of self expression propoganda?

Re: The James Webb Space Telescope has passed the final mission analysis review

#283

Post by vimacs2 »

minitoar wrote: post #273
xref wrote: post #234

Earlier quoted context omitted.

Because some component bays designed to be swapped out were swapped out? Far as I know they haven’t replaced the 2.4m main mirror or the housing, you know, the “ship”

Yes, that is the joke I was making. Thank you for explaining it.

I think their point was your joke doesn't make much sense when only a small subsection of the entire telescope was ever replaced.

Re: The James Webb Space Telescope has passed the final mission analysis review

#284

Post by minitoar »

vimacs2 wrote: post #283
minitoar wrote: post #273

Earlier quoted context omitted.

Yes, that is the joke I was making. Thank you for explaining it.

I think their point was your joke doesn't make much sense when only a small subsection of the entire telescope was ever replaced.

In my opinion that's part of what makes it funny, and is also a core issue in the Ship of Theseus problem -- who's to say how much it can be changed and is still "the same thing"? Maybe the thing that was replaced was very small but was very important to the identity.

Re: The James Webb Space Telescope has passed the final mission analysis review

#285

Post by anticensor »

ckozlowski wrote: post #227
bumby wrote: post #121

Earlier quoted context omitted.

Are you speaking to the reliability of the launch vehicle or of the satellite? The launch itself is typically not a primary cost driver of a satellite mission. Complexity may be, due to constraints of the fairings but the manufacturing and quality checks drive quite a bit of the cost

I think they mean reliability of the satellite. The JWST is going to be parked at a Lagrange point that's going to put it out of reach of most everything. At the time it was conceived, robotic servicing was even further off. A crewed mission was right out. Costs went far up in part because unlike Hubble, servicing was going to be virtually impossible.

Starship has a sufficient delta-v to service it.

Re: The James Webb Space Telescope has passed the final mission analysis review

#286

Post by spaetzleesser »

bumby wrote: post #280
jasonwatkinspdx wrote: post #224

Earlier quoted context omitted.

I can understand not liking how bureaucratically onerous it is, but we don't really have a choice. It's imperfect but it's the only way we've found to manage highly complex large scale engineering projects. You certainly aren't going to build something like JWT with a just YOLO agile process unless you're literally willing to fail like 50 times before you get one right (aka the USSR approach to rockets). The upside i…

> The upside is automation is making it go smoother and be less burdensome, because simulated testing truly is high enough fidelity I agree to an extent, but there's also a risk of simulation breeding a false sense of security even when simulations are conducted well. The investigation of the CST-100 "anomalous" test flight had 21 findings related to software simulations and testing, some related to lack of fidelity.…

The good thing about simulations is that once you have figured out a problem it won’t make the same mistake again. That’s the strength of computing

Re: The James Webb Space Telescope has passed the final mission analysis review

#287

Post by dreamcompiler »

thereddaikon wrote: post #281
Gustomaximus wrote: post #275

Earlier quoted context omitted.

Question if anyone knows: ~9.5 years any reason to not push it out of orbit into space and continue to get signals back for years longer as it floats off? Like the voyagers?

JWST isn't a probe like Voyager. It's job isn't to go to other worlds and see what's there. Its a space observatory. It does exactly the same job a telescope on earth would do, just in space. The reason why is to avoid light pollution and the interference from earth's atmosphere. So that fuel isn't used for going places, its for aiming the telescope and keeping it steady. Once the fuel is gone it can no longer contro…

You can aim it with reaction gyros which rotate the telescope and require only electricity. What you cannot do with electricity is translate the telescope along a vector to compensate for orbital decay and keep it on station. That's what fuel is for.

Re: The James Webb Space Telescope has passed the final mission analysis review

#288

Post by dreamcompiler »

bane wrote: post #191

It's my personal belief that these massive R&D space telescope programs are nearing their end. Computational approaches among multiple sensors, combined with good 'ol factory mass manufacturing powered by low-cost reusable launch technology allows for the money spent on one-shot programs like this to be spent and allocated in radical different ways. Instead of building one huge short life-span spacecraft, why not lau…

> Use some computational methods to combine the sensor collection from dozens, hundreds, or thousands of these kinds of spacecraft and you could end up with planet sized instruments pretty efficiently.

This kind of thing cannot currently be done at optical wavelengths no matter how much computational power you throw at it; the frequencies are simply too high to do phase capture and syncing digitally.

It's done on a limited basis at the very large telescope (VLT) in Chile but the phase combiners there are optical and analog.

Re: The James Webb Space Telescope has passed the final mission analysis review

#289

Post by qubitcoder »

anticensor wrote: post #285
ckozlowski wrote: post #227

Earlier quoted context omitted.

I think they mean reliability of the satellite. The JWST is going to be parked at a Lagrange point that's going to put it out of reach of most everything. At the time it was conceived, robotic servicing was even further off. A crewed mission was right out. Costs went far up in part because unlike Hubble, servicing was going to be virtually impossible.

Starship has a sufficient delta-v to service it.

Yes, but Starship is a prototype at the moment. And it'd require the Super Heavy to even reach orbit, which will soon begin testing [0].

Additionally, the engineering requirements for long-term life support are significantly more involved than the Dragon capsule.

There's also the testing and certification process for crewed-missions; in non-Elon time, this is likely several years, conservatively speaking [1]. (I'd love to be proven wrong, however!).

[0] https://www.space.com/spacex-starship-super-heavy-booster-ro...

[1] https://arstechnica.com/science/2021/04/five-reasons-why-nas...

Re: The James Webb Space Telescope has passed the final mission analysis review

#290

Post by wolverine876 »

vimacs2 wrote: post #282
gccs wrote: post #264

Earlier quoted context omitted.

Propaganda

Considering that they themselves made the telescope, do you consider all forms of self expression propoganda?

> self expression

This isn't art. And yes, I don't trust corporate press releases (though I'm not sure "propaganda" is the right term); do you?

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