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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

#251

Post by mustardgreen »

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…

The Starlink fleet has been a huge problem for the field of astronomy entirely do to this "move fast and break things" ethos.

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

#252

Post by mhio »

caconym_ wrote: post #247
jasonwatkinspdx wrote: post #241

Earlier quoted context omitted.

I am giving credit. I'll call it working when they've demonstrated repeated access to orbit. Until they, they are indeed playing with flying grain silo prototypes, even if they landed one belly flop maneuver. In any case, this is the exact sort of argument I find entirely wasteful of energy, and a distraction from what we should be talking about in this thread, which is JWT.

> I am giving credit. No, you aren't. "Still trying to get hovering grain silo versions working" is not an accurate characterization of the current state of Starship development: they had hovering in the bag months ago, and have since demonstrated much more challenging and impressive capabilities. > I'll call it working when they've demonstrated repeated access to orbit. Until they, they are indeed playing with flyin…

> if you want to call rockets "grain silos", I'm not going to try to stop you, though I might caution you against erasing your ability to identify actual silos full of grain.

Agreed, they're definitely flying water tanks :)

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

#253

Post by mhio »

wolverine876 wrote: post #223
Me1000 wrote: post #186

Earlier quoted context omitted.

The Falcon 9 has had 126 missions so far and only 2 of those were failures. It's not a perfect record, but it's pretty decent. And presumably SpaceX has learned from those failures. Compare that to the Ariane 5 rockets (which will actually be launching the James Web Space Telescope) which has had 109 launches, and 5 of them ended in failure. I'm just going to assume you're referring to Starship's various explosions.…

> the Ariane 5 rockets (which will actually be launching the James Web Space Telescope) which has had 109 launches, and 5 of them ended in failure I just read that they had one failure, though I can't find it. Does anyone have any reliable data (i.e., not Wikipedia)?

http://www.spacelaunchreport.com/ariane5.html

The notes for the failures are at the bottom.

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

#254

Post by Cthulhu_ »

prox wrote: post #249
Taniwha wrote: post #245

Earlier quoted context omitted.

And it's at L2 so not that easy to get to

I take Starship could, and should be operational in some form by then.

Question is whether it'll be financially / commercially viable. I think that greatly depends on how much data the telescope gathers or whether it needs more time. Also keep in mind that the Hubble got multiple upgrades over its lifespan, which will be much more difficult with the Webb - is it feasible to do spacewalks that far out? Has any astronaut ever done a spacewalk outside of Earth orbit?

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

#255

Post by nabla9 »

pklausler wrote: post #99
nabla9 wrote: post #56

Earlier quoted context omitted.

The JWST will not orbit Earth. It will be located near the second Lagrange point (L2) over 1,500,000 km away (The Moon is just 405,000 km from the Earth). Space Shuttle could not have reached it.

It's not an orbit, per se, but... it will go around the Earth once per year.

Only in the same sense as mars goes around the Earth. Meaningless concept. It never crosses inside Earth orbit.

Maybe "co-orbits the Sun with the Earth using Earth's gravity"

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

#256

Post by GekkePrutser »

zabzonk wrote: post #236
minitoar wrote: post #232

Earlier quoted context omitted.

It’s the telescope of Theseus, though.

Sort of. The broken optics famously got fixed in the first HST shuttle mission, and there have been other replacements over time. A lot of it is the same, though. And of course, the HST is in LEO, which means it is reachable with current rocket tech, which the James Webb, being situated at L2 won't be. But that's not to say you could not have a large platform at L2 (or another Lagrange point) that could be serviced b…

But Hubble wasn't a one-off design. It shared a lot of design elements with other space telescopes that are more earth-focused :) So it had a lot more benefits of scale than JWST.

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

#257

Post by mhio »

bane wrote: post #209
whoisburbansky wrote: post #206

Earlier quoted context omitted.

Phone cameras don’t have multiple lenses working together that you can interpolate between to create a single giant virtual lens. The technique OP is referring to is already used for the largest ground based radio telescopes.

Exactly correct. And Labeyrie has a design in place for the exact type of fleet I'm talking about.

Do you have a link to the design? I'm assuming it's a radio telescope?

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

#259

Post by arp242 »

foolfoolz wrote: post #237
zabzonk wrote: post #221

Earlier quoted context omitted.

> Instead of building one huge short life-span spacecraft Short life-span? How long has the Hubble been up there?

webb needs to use thrusters to stay in position. there’s 5 years worth of fuel onboard they did design the fuel in a way that potentially could be refilled… but the refilling craft doesn’t exist. and webb timescales make that sound impossible

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

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

#260

Post by mhio »

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…

I doubt the large space telescope programs will end, there will just be other options to how they're done. Scientists will still push the state of the art (if they get the funding) which will still be expensive and might still involve big mirrors here and there for optical imaging. Building a large fleet radio telescope in space actually sounds like a good proposal for massive R&D space telescope program.

Unfortunately optical interferometry as suggested isn't a thing yet. Even the physical optical interferometry we do on the ground has only become possible relatively recently. I'm not in the field so I'm not sure what's around the corner but seems to rule out Hubble/JWST/WFIRST/LUVOIRE replacements any time soon. Maybe TESS like scanning imaging would be a good fit for a fleet?

The big change I hope will be easier, cheaper, regular access to space which hopefully means there won't be such unicorn projects that spend 4 years in systems testing because they _can't_ fail.

> Tasking the fleet could be more dynamic as well, with different researchers able to reserve different percentages of a huge fleet for their specific experiments and needs

Specific observations require specific instruments though, there's no one size fits all fit out for a fleet satellite. JWST has a very large mirror looking a near and mid infra red a long way from earth with large IR shielding. You can't do this and Kepler/Tess type imagery in a single fleet unless the sats are specifically equipped for it on the ground before launch and sent to vastly different places which kind of nullifies a really dynamic fleet.

Not saying that having a standardised, cheap satellite bus that can be quickly thrown up in space won't change things, it's just not the answer to everything.

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