James Webb is fully deployed • Hacker News Board

Re: James Webb is fully deployed

#321

Post by CamperBob2 » Sun, Jan 09, 2022, 2:13 AM UTC

caconym_ wrote: post #212

WalterBright wrote: post #166

Earlier quoted context omitted.

> Yes, but the data has diminishing returns as well. I find that hard to believe considering there's literally a universe of things to look at. We find surprising things everywhere we look.

It's not quite the same thing, but as an analogy: should we have built two CERNs (edit: LHCs, not CERNs) to "find" the Higgs boson faster? Or was it better just to build one, expecting that it had a good chance of finding the particle and other new physics, and then put future funding toward different/more advanced and capable instruments that will give us a window into even higher energies/entirely new observation s…

It's not quite the same thing, but as an analogy: should we have built two LHCs to "find" the Higgs boson faster?

Depends. Is experimental time at the LHC anywhere near as competitively-rationed as it is for a space telescope like Hubble or Webb?

Re: James Webb is fully deployed

#322

Post by Sebb767 » Sun, Jan 09, 2022, 2:14 AM UTC

newman8r wrote: post #278

bichiliad wrote: post #250

Earlier quoted context omitted.

One thing they mentioned that kinda sends it home to me is that the telescope is aimed at the dark and away from the sun, and the other side is especially reflective[0]. In other words, one side is too dark to see, and the other is too bright to see. [0]: https://twitter.com/NASAWebb/status/1479161991252131841

Couldn't they just use an image intensifier tube for night vision? I think they should just stick with the excuse of it being costly and unnecessary.

We're talking about "see the faintest light from stars millions of lightyears away"-dark (for that reason you also can't shine a light on it), with our sun in the background. To see something on that side, you'd basically need the vision capabilities the telescope itself has and that's obviously not going to happen.

Re: James Webb is fully deployed

#323

Post by tnle » Sun, Jan 09, 2022, 2:15 AM UTC

asteroidbelt wrote: post #103

No mention of ESA again, looks like it is solely NASA project, which it is not. Shame.

From the article, near the very top:

"A joint effort with the European Space Agency (ESA) and Canadian Space Agency, the Webb mission will explore every phase of cosmic history – from within our solar system to the most distant observable galaxies in the early universe."

Re: James Webb is fully deployed

#324

Post by dTal » Sun, Jan 09, 2022, 2:16 AM UTC

Sebb767 wrote: post #322

newman8r wrote: post #278

Earlier quoted context omitted.

Couldn't they just use an image intensifier tube for night vision? I think they should just stick with the excuse of it being costly and unnecessary.

We're talking about "see the faintest light from stars millions of lightyears away"-dark (for that reason you also can't shine a light on it), with our sun in the background. To see something on that side, you'd basically need the vision capabilities the telescope itself has and that's obviously not going to happen.

It obviously needs a selfie mirror.

Re: James Webb is fully deployed

#325

Post by digitalsushi » Sun, Jan 09, 2022, 2:17 AM UTC

stolsvik wrote: post #289

BurningFrog wrote: post #236

Earlier quoted context omitted.

In your body, the brain, heart and lungs are all single points of failure. If either one fails, you die.

You have two lungs, though. One can fail and you will still live. As with kidneys. Strange that there is only one heart.

It's strange but we're still pretty bad at using more than a single computer core on average.

Re: James Webb is fully deployed

#326

Post by Sebb767 » Sun, Jan 09, 2022, 2:18 AM UTC

heavenlyblue wrote: post #271

idealmedtech wrote: post #266

Earlier quoted context omitted.

How can it make out galaxies at billions of light years away, but not a truck sized craft at a few million miles? I haven't done the math myself, so I'm certain one side of that equation is wrong, but that seems hard to believe!

It’s interesting that you are expressing an opinion about something that you could calculate in the same amount of time it took to write down that opinion.

To be fair, for someone who is not well-versed in either optics or space physics, calculating the answer is not that straight-forward.

Re: James Webb is fully deployed

#327

Post by samstave » Sun, Jan 09, 2022, 2:19 AM UTC

JshWright wrote: post #313

samstave wrote: post #310

Earlier quoted context omitted.

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.

I have a few questions about extending a tethered "selfie bot"

If you have a tethered camera which uses the tether as its power source which is out in front of the scope, wouldn't it be able to "stare" back at the Business Side of the mullet and stream the Party back to earth?

Or does a teathered bot risk messing with the orbit of the scope?

How much actual pull strength is requireed per kilo to re-orient something in space, meaning: How easily could say an astronaught pull on a cable and change the orientation of an object of much larger mass?

What if there were a gyro-ratchet:

Gyros that spin, and are tethered to a thing. There are multiple of them and they "yank" a small amount by spinning their gyro/flywheel a bit to initiate a pull... but there are many of these extending off tethers to orient something...

What if the tethers are like a flat ribbon cable of super thin solar collecting "flat noodles" - they provide power to the orienting gyros...

but how do you untangle things in space if stuff goeas awry...

---

Maybe the craft only deploys gyros, via tethers, when it needs alignment - re-pointing... and reels the gyro back in when done...

or reels them back out when the tether should use solar to trickle re-charge the gyro battery.

Re: James Webb is fully deployed

#328

Post by dtgriscom » Sun, Jan 09, 2022, 2:20 AM UTC

terramex wrote: post #170

ak217 wrote: post #159

Earlier quoted context omitted.

JWST, like many other spacecraft, has reaction wheels to orient itself. The reason Kepler ran out of fuel when it did was that it was expending more maneuvering fuel for attitude control because two of its four reaction wheels failed. Hubble and the ISS also had similar failures. We're getting better all the time at building more reliable components (including reaction wheels and cryocoolers) though. Until a few year…

> The reason Kepler ran out of fuel when it did was that it was expending more maneuvering fuel for attitude control because two of its four reaction wheels failed. Hubble and the ISS also had similar failures. And to calm down anyone afraid of JWST sharing the same fate - construction of reaction wheels have been changed some time ago to make them significantly more reliable. The source of issues on Hubble, Kepler,…

Great info: citation? More details?

Re: James Webb is fully deployed

#329

Post by pkaye » Sun, Jan 09, 2022, 2:20 AM UTC

ArmandGrillet wrote: post #56

541 wrote: post #51

For some context around what makes this deployment so remarkable, watch this[0] video that talks about the engineering/building aspects of the James Webb [0] https://youtu.be/aICaAEXDJQQ

Thanks for the link. I am interested in knowing more about the organization behind that project: how many people took care of the deployment, how are they organized, how has quality control been done. https://www.latimes.com/business/story/2021-12-25/james-webb... gives some info but not an in-depth view of how things work at the NASA.

A couple of interesting links I've found so far on the technology of the telescope.

https://www.jwst.nasa.gov/content/observatory/ote/mirrors/in...

https://www.stsci.edu/~idash/pub/dashevsky0607rcsgso.pdf

https://ntrs.nasa.gov/api/citations/20080030196/downloads/20...

Re: James Webb is fully deployed

#330

Post by WalterBright » Sun, Jan 09, 2022, 2:23 AM UTC

histriosum wrote: post #235

WalterBright wrote: post #139

Earlier quoted context omitted.

It is entirely true. Source: I worked on 757 flight controls design for 3 years. > what if the front fell off? All structural components are redundant and have redundant attachments. The wing spars are doubled, for example.

There are certainly single points of failure in airliner design. An example that springs to mind is the stabilizer trim jackscrew. There are supporting systems which try to mitigate the risk of failure or the likelihood of failure, but bottom line, if the jackscrew fails, there is no redundancy. You've lost stab trim, potentially making the situation unrecoverable. Of course Alaska 261 is one such example of a jacksc…

I worked for 3 years on the design the 757 stab trim jackscrew. We considered every failure, and had redundancy for it.

The AL flight cracked its nut, and the balls fell out. I don't know the details of that design, but on the 757 the ice scrapers on both sides of the nut will hold the nut in place if the balls fall out.

If I recall correctly, if the AL pilot had simply left the trim system alone after it failed, and landed the airplane, it would have been fine. Instead, he kept fiddling with it, driving it up and down, until it tore the nut to pieces. The loud screech it made when running in a half broken configuration should have chilled anyone's blood to bone at 30,000 feet.

As that incident, and the later MAX crashes clearly demonstrated, once something goes wrong with the stab trim system, you move it only enough to get the airplane into a flyable state. Then, you turn it off and leave it the frack alone. Land it, and let the mechanics figure it out with it safely in the hangar.

One incident where the stab trim failed and the poor pilots were just passengers to their doom was that 747 that took off from the base, and some tank in the cargo hold broke loose, slid back, smashed through the bulkhead and broke off the whole stab trim system.

That really wasn't the stab trim system's fault, you can't really design for a tank falling on it. It was the fault of no redundancy in the straps holding the tank in place.

The video of the crash, shown endlessly on the news, makes my gut turn to water.