Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

James Webb is fully deployed

nasa.gov

Post reply on HN
Print view View original

311–320 of 522 posts

Re: James Webb is fully deployed

#311

Post by WalterBright »

hypertele-Xii wrote: post #154
WalterBright wrote: post #119

Earlier quoted context omitted.

Assuming your figures are correct, you'll get double the data for another 30% cost. If you wait a month before launching #2, if problems appear in #1 (like the telescope mirror was ground improperly) it can be fixed in #2. The operational cost will not double. The same ground facility, equipment, and staff can manage both. If you're buying two identical launches, you can get a quantity discount. > the benefits of a s…

Doubling the data will also double the processing requirements for that data. The observatory is just the remote part of this operation. The data doesn't do squat unless stored, analyzed and interpreted by expensive professionals on expensive equipment. It's like saying if you're gonna build a chip fab, why not build two while you're at it? Well because the building isn't the operation.

Why do I have to do all the thinking?

1. Grad students and computers are cheap.

2. Crowd source it. Make the data (and the programs that process it) freely available. Let anyone who wants to analyze it - if they find something cool, they can be famous. They'll do it for free.

3. Processing doesn't have to be done in real time. There's no problem with taking 5 years to analyze 1 year of data.

Re: James Webb is fully deployed

#312

Post by WalterBright »

WalterBright wrote: post #75

Since 90% of the cost is probably in R+D of the telescope, one could build and deploy another for another 10%. Why isn't this done? Why is every space telescope completely unique?

After reading all these replies, I'm glad Musk never listened to people who said he couldn't make a cheap, reliable rocket that could land on its tail.

grump, grump, grump

Re: James Webb is fully deployed

#313

Post by JshWright »

samstave wrote: post #310
jl6 wrote: post #192

More great news. Congratulations to all who have worked on the project. I understand the reasons for not putting a camera on or near the JWST, but I’m still a little sad that we’ll probably never get to see the thing in situ in all its operational glory. Maybe one day when it finally expires, we can launch a “sample return” mission to tow it back.

Why dont we deploy a smaller sat in the same-ish orbit thats only job is to be the RING Doorbell for the JWST -- all it does is stream a live-stream back of the JWST -- if we can freaking deploy streams of Starlink (SKYNET) devices - we can certainly place tele-photo-capable sats that can then provide streaming video back of the things they are walking -- and they can FN relay off the starlink (SKYNET) devices...

All you would be able to see is the sunny side of the sun shield, none of the cool (both literally and figuratively) bits, which are all in darkness.

Re: James Webb is fully deployed

#314

Post by michaelwilson »

behnamoh wrote: post #285
JohnBooty wrote: post #208

Earlier quoted context omitted.

Great blog post from NASA themselves explaining it: https://blogs.nasa.gov/webb/2022/01/06/why-doesnt-webb-have-... the post is really not very long and I would suggest getting it straight from the horse's mouth, but for those not willing to devote a click here are arguably the most relevant bits! "deployment surveillance cameras would not add significant information of value for engineering teams commanding the spac…

they could have sent a temporary camera along with the craft to take a picture of it at the final position and send back to earth.

Sadly one of the the problems is, it's dark where it is. The mirror side is in complete darkness (because of the sunshield), and the sun side is blazingly bright (because of the reflective sunshield).

This is the unfortunate reality of space: The images we see from the Hubble, et al, are exposed for minutes if not hours, and processed to bring out colors invisible to the human eye. An astronaut flying to see the Webb, or one of many other "well known" astronomical landmarks would see either nothing or a faint smudge without a telescope or other enhancements.

The aforementioned NASA blog post goes into the many other reasons this wasn't practical.

Re: James Webb is fully deployed

#315

Post by weaksauce »

xvector wrote: post #280
weaksauce wrote: post #272

Earlier quoted context omitted.

the plan as i understand it is to have a drone refuel it after about 10 years or so... that might have a camera on it perhaps?

I thought there were no plans for any refuel or repair mission.

I guess the videos I watched made it seem more sure than it is... at the very least they left themselves open to the possibility of it if it makes sense to do.

Re: James Webb is fully deployed

#317

Post by godelski »

sailingparrot wrote: post #254
godelski wrote: post #213

Earlier quoted context omitted.

Instead of comparing to other telescope projects maybe better to compare to other mega science projects. Or better yet, other government costs. Though of course we'd need to run a cost benefit analysis. The thing is that these numbers are big for us and most companies, but these are government numbers and decades of work. Both factors are important. It's $11bn over 24 years, or 458m/yr. I'm happy to pay an extra $3/y…

> I'm happy to pay an extra $3/yr for this project. Yes, I think many of us would be happy to. But the reality is that NASA has to fight a pretty ferocious budget battle every year, and often (not always) delay and increase in JWST cost has meant postponing or cancelling other missions. For example the Nancy Grace Roman Space Telescope, which was deemed the top priority by the decadal survey in 2010 almost got cancel…

This isn't so much a limited resource problem as an allocation problem. If US, and western, interest increases in science then funding more missions like these will be more popular and Congress will increase budgets. But budget allocations are low because they are unpopular. We talk about the high costs of these missions but they are close to rounding errors in the US yearly budget. It's weird to me that we argue over pennies when we're spending hundreds with no question. We'd say that's insane if we were trying to set budgets for ourselves. The reason it works it because the total numbers are large and we aren't scaling properly. It's a distraction.

Re: James Webb is fully deployed

#318

Post by michaelwilson »

terramex wrote: post #82
WalterBright wrote: post #72

What puzzles me is the maneuvering fuel. When that fuel runs out, the telescope can no longer orient itself. This ended the life of the Kepler telescope. But aren't there other ways to orient in space? 1. use pressure from the solar wind 2. have 3 electric motors on 3 axis. Wouldn't spinning those motors rotate the craft? Electric power to do it would come from solar panels, giving it plenty of fuel.

Pressure from solar wind will constantly put some torque onto telescope as its center of pressure is offset from center of mass. This torque will be counteracted by reaction wheels but they have maximum rotation speed and need to be unloaded using thrusters periodically.

Thus, the "Aft Momentum flap":

https://www.jwst.nasa.gov/content/webbLaunch/deploymentExplo...

Re: James Webb is fully deployed

#319

Post by WalterBright »

porsupah wrote: post #281
ThinkBeat wrote: post #189

Earlier quoted context omitted.

They should have made a port for refueling it. An internal fuel tank and a high-capacity tank externally Once the fuel is getting low, launch a refuel. when the new supply gets closed, eject the previous tank, dock the new one. Easy. When they managed to du an in air refuel of a SR71 in 1970s . Surely we can dock a fuel tank in 2022?

They did: "Unlike Hubble, Webb isn't designed to be fixed by astronauts. But it can be refueled robotically. Zurbuchen says that 'once this telescope is deployed, I'm going to put all the effort towards developing that technology, and so within the 10-year lifespan, we can go refuel it'" https://nitter.42l.fr/marinakoren/status/1474367236244750345... https://nitter.42l.fr/Dr_ThomasZ/status/1474398711505580032#...

The astronauts had some serious, unexpected difficulties fixing the Hubble in orbit, and had to improvise. I'm skeptical that blasting a fuel coupling into space, and then trying to figure out how to connect it to a robot, will end well.

Re: James Webb is fully deployed

#320

Post by WalterBright »

terramex wrote: post #160
WalterBright wrote: post #134

Earlier quoted context omitted.

Being a telescope, what matters is where it is pointing, not where it is.

It matters a lot, L2 is unstable point so if it ventures beyond L2 there would be no way to bring it back and it would enter a heliocentric orbit. Communication between Earth and telescope would become impossible after some time as gimballed antenna can only rotate so far and stray light reflected from Earth would limit its field of view. Due to that JWST will always be on 'close side of L2' and technically in slow f…

> as gimballed antenna can only rotate so far

That's a fixable design problem. Or you can rotate the telescope.

> stray light reflected from Earth would limit its field of view

What? The earth and the moon are nearby anyway. What about that reflected light? And heck, what about the sun limiting its field of view?

Post reply on HN