James Webb Space Telescope: Sun Shield Fully Deployed (bbc.com) 124
"On Tuesday morning, all five layers of the James Webb Space Telescope were fully locked into place," writes Slashdot reader quonset. The BBC reports: There were many who doubted the wisdom of a design that included so many motors, gears, pulleys and cables. But years of testing on full-scale and sub-scale models paid dividends as controllers first separated the shield's different layers and then tensioned them. The fifth and final membrane was locked into place at 16:58 GMT. "The unfurling and securing of the sun shield is part of what NASA refers to as '29 days on the edge,' writes quonset, citing an article from CNN. "During the 29 days, Webb will set up shop, unfurling its giant gold mirror and the protective tennis court-size sunshield. This process involves thousands of parts that must function harmoniously, in the right sequence. Fortunately, each step can be controlled from the ground in case there are issues."
"The next step is the unboxing of the mirror which had to be folded to fit inside the nose cone of the rocket for launch. If all goes well, by the end of the weekend, the mirror will be in place and ready for testing before full operations begin."
"The next step is the unboxing of the mirror which had to be folded to fit inside the nose cone of the rocket for launch. If all goes well, by the end of the weekend, the mirror will be in place and ready for testing before full operations begin."
Someone should point a telescope at that telescope (Score:2)
It'd be cool to actually see all this happen.
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The camera would have a weight, which would increase the telescope's propellant consumption and hence shorten its useful life. It also would need a heating device, with its own weight and energy budgets. The cam being at space specs would not be a tiny off the shelf phone one.
It would also need a lighting device if on the far side since it is in the dark.
Re: Someone should point a telescope at that teles (Score:2)
Actually the whereiswebb site used to just have animations of each deployment step, but for the sunshield they actually have timelapse video of the deployment. I presume this is either from ground testing or from their local model of Webb.
https://webb.nasa.gov/content/... [nasa.gov]
Re:Ummmmmmmmmm, No! (Score:5, Insightful)
It will be boring as shit. That thing is deploying at a snail's pace. So it will be like watching paint dry. If it could do it in under an hour, then yes.
Watching space is all about observing things that mostly happen at a snail's pace.
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It will be boring as shit. That thing is deploying at a snail's pace. So it will be like watching paint dry. If it could do it in under an hour, then yes.
Watching space is all about observing things that mostly happen at a snail's pace.
That guy got really pissed off at the Hubble Deep field - Took too much time!
I would suggest for him one of the many fine reality shows like Keeping up with the Kardashians, or Love After Lockup - much fast very pace. Him likey much!
Re:Ummmmmmmmmm, No! (Score:5, Insightful)
Time lapse photography fixes that.
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There's a timelapse available of it unfolding on Earth [youtube.com]. Most of the time is spent "inflating" to the seven layers.
So how does this remain in L2? (Score:3)
Re:So how does this remain in L2? (Score:5, Informative)
Proposed solar sails have areas starting on the order of a square kilometer and going up -- that is to say starting at roughly 5000x the area Webb's sun shield.
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I suspect there is still some effect from the sun shield, but JWST has quite a bit of maneuvering capability, too. Far more than enough to offset any minor push from the sun shield.
The thing that's worrying me is that JWST is going to be constantly pivoting to keep the shield facing the sun while the target is being tracked. That's going to take quite a bit of power for the pivoting and a lot of computational power to control the movements.
Still, I think it's a great project and I'm keeping my fingers cross
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Given the precision of the instrument, there's bound to be all kinds of crazy things they had to make provision for. From what I've heard the success of their initial launch has left them with some healthy fuel margins to complete and probably extend the planned lifespan of the mission. It's still a hell of a nailbiter though.
I don't think the poster's question was silly by any means, and I'm sorry if I gave that impression. There's no reason for anyone to have that information at their fingerprints, and
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Mostly concurrence, though your use of "fingerprints" for "fingertips" makes me wonder about your first language. Also, the reference for your "nailbiter" is a bit unclear, but I think you mean the initial assembly and deployment. However, now I think we were both pretty far off the mark.
The gravitationally interesting thing about each Lagrange point is that objects tend to stay there. I'm hoping one of the other replies includes the math, but my "mental envelope" calculation indicates that the force needed
Re:So how does this remain in L2? (Score:5, Informative)
The Webb telescope, like the ISS, Hubble, and others use gyroscopes for pointing alignment.
When the gyroscopes get to their max deflection and need to have their alignment reset, that's when the thrusters are used.
https://en.wikipedia.org/wiki/... [wikipedia.org]
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This page says JWST uses reaction wheels [wikipedia.org], not control moment gyroscopes [wikipedia.org]:
https://jwst-docs.stsci.edu/jw... [stsci.edu]
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This page says JWST uses reaction wheels [wikipedia.org], not control moment gyroscopes [wikipedia.org]:
https://jwst-docs.stsci.edu/jw... [stsci.edu]
Ahhh, you're right. Reaction wheels are doing the work.
I saw articles mentioned that gryoscopes were used for pointing and made an unwarranted assumption. It appears that the gyroscopes on the Webb are the wine glass kind for monitoring position and alignment, but they don't provide angular momentum or movement force. They're not massive control moment gyroscopes for physical movement like the ISS has.
So, I rewite my post:
The Webb telescope, like the ISS, Hubble, and others use reaction wheels for pointing
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Thanks for the additional data, but my focus was actually on the complexity of the aiming here, though the math is over my head. However, now that I think about it, maybe the math isn't so bad after all? There are two main factors they need to correct for, but they are linked fairly intimately. As the earth moves in its orbit, the angle to the sun is constantly shifting, and the sun shield of the JWST has to compensate for that continuous movement (and without fail, ever). On the other side, if the image in
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There is no price to pay for having the telescope rotate once per year in principle (as any angular orientation is equivalent in empty flat space); In reality, differential radiation pressure and buffeting by solar winds mean that the craft will have t
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Also, L2 is unstable in "distance to Sun" so there's bound to be some maneuvering to compensate for that.
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Thanks again, though now I'm wondering why the distance to the sun will be of concern. Especially if the "exposure times" are short.
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The Sun-Earth line sweeps the trajectory plan of Earth. ...)
Objects approximately in L2 will "slow down" or "accelerate" to stay on that line (initial positioning is not perfect, and there are small influences from Moon, Jupiter,
Unfortunately, we have objects that are not exactly in L2 (or that are influenced away, see lunar influence). And when they start going, they will go faster and faster.
And once far enough away from L2, the influence that keeps them "locked" into the Earth-Sun line will vanish, and t
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"JWST is going to be constantly pivoting to keep the shield facing the sun while the target is being tracked."
Assuming JWST has a "stable" orientation due to Sun gravity, it will make a 360 degrees turn in a year. To compensate for an effect of this magnitude, some small gyroscopes should be enough.
And this is a problem solved for the Hubble (keeping the same orientation for long exposures) in Earth orbit.
And, if the sun shield is "the size of a tennis court" (22 by 10 meters), the JWST's mirror of 6.5 mete
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Thanks, though a bit unclear. Some of the other replies went into much more detail about the reaction wheels.
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The thing that's worrying me is that JWST is going to be constantly pivoting to keep the shield facing the sun while the target is being tracked. That's going to take quite a bit of power for the pivoting and a lot of computational power to control the movements..
JWST will use a gyroscopic system to provide rotational control the same way other satellites do, and not use any fuel too keep the sun shield on the right side. This only uses tiny amounts of fuel to correct for accumulated variations. Adjusting the sunshield will use less power than rotating the much heavier telescope between targets at the end of each observation session. Hopefully the energy storage systems have been sized correctly so this won't be a problem.
Out at the earth-sun L2 there's no asmospher
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Again, basic concurrence and it mostly meshes with the other replies.
But of course I've thought of new things to worry about... Micrometeorites... Now I'm hoping they have lots of spare cameras that they can swap in as needed... I'll continue with the crossed fingers.
Re:So how does this remain in L2? (Score:5, Interesting)
Simply put, they always want to be on the "uphill" side of L2. Webb can only thrust uphill, never downhill. It's designed to always fall back towards the Sun with occasional thrust boosts to get it back to close to the top of the hill. The solar pressure just slows the return fall, saving fuel.
Re:So how does this remain in L2? (Score:4, Informative)
Re: So how does this remain in L2? (Score:5, Informative)
Itâ(TM)s deliberately NOT in the earthâ(TM)s shadow. It orbits L2 about 1.5 million km from L2 perpendicular to the plane of the ecliptic. Itâ(TM)s either a âoeLissajousâ orbit or a âoeHaloâ orbit; I didnâ(TM)t understand which. The shadow of earth and moon is never larger than about 1.3 million km around L2.
The reason is to never be in shade, and to have uniform constant sun/heat all the time. This allows for smaller batteries that donâ(TM)t have to spend lots of energy maintaining heat during an eclipse, and are always operating at a good temperature for them, and more controlled thermals for the entire satellite. The hot side is 85 Celsius, the bus is 30 Celsius, the observing side is 30 Kelvin, and there are a load of mini heaters on the observing side to keep individual electronic components warm enough to operate.
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Itâ(TM)s deliberately NOT in the earthâ(TM)s shadow.
Ugh. I'm sorry for the unicode. I recently switched to Apple's keyboard on my iPhone, which I guess uses something other than ASCII for its apostrophes. Ugh.
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Re: So how does this remain in L2? (Score:5, Informative)
Turn off "smart quotes" to stop that. It's pretty clear that Slashdot will never fix their unicode failings. it's been shit for years.
Re: So how does this remain in L2? (Score:3)
Here is a test. I turned off a feature called "smart punctuation". Let's see if it worked...
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It did. Congrats, you can now make readable posts on this antiquated site!
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The antiquated nature of this site is one of the things I love so much about it. I browse slashdot with 100% script blocking. It renders correctly and is fast as hell compared to almost anything else. With that said, FFS support unicode slashdot.
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Turn off "smart quotes" to stop that. It's pretty clear that Slashdot will never fix their unicode failings. it's been shit for years.
Slashdot's no unicode policy has spared us from scrolling past pages of swastikas made with unicode swastikas, smiley faces, and the goatse character, Sinhala Letter Oyanna.
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Instead we scroll past all that shit made in other ways that don't involve Unicode and still aren't filtered out, and end up with unreadable posts from people using Apple devices that work with literally every other website on the planet.
I'd rather have more non-broken posts from legit users.
Re: So how does this remain in L2? (Score:3)
This is because the Earth only partially eclipses the Sun when viewed from L2, with the remaining sunlight forming a ring around the Earth.
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The Sun's angular diameter is (2*arcsin(diameter of the Sun / (2 * 1 AU))) which is 0.53 degrees. The Earth's angular diameter is (2*arcsin(diameter of the Earth/ (2 * 1.5e6 Km))) which is 0.48 degrees. You actually can't be in a true eclipse although you could blot out 82% of the Sun in the right spot. But even if you wanted to blot out the Sun with the Earth, the L2 point is not stable and the Moon, Mars, and Jupiter push any objects around a
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Propellant. Also the pressure of the sun on this sail is minuscule. And L2 is not perfect, so you can position it a bit out of the perfect spot to counter that pressure if needed. No idea whether they need to even do that.
Re:So how does this remain in L2? (Score:5, Informative)
From the JWST user documentation:
While orbits about the L2 point are inherently unstable, the orbit size is large and the orbital velocity is low (~1 km/s), so the orbit "decays" slowly. However, JWST's large sun shield, roughly the size of a tennis court, is subject to significant solar radiation pressure which results in both a force and a torque. The direction of solar force varies as the observatory's attitude changes from observation to observation. The solar torque is balanced by reaction wheels, but periodically, the accumulated momentum is dumped by firing thrusters. Because JWST operations are event-driven, the observatory attitude profile and momentum dumping cannot be accurately predicted months in advance. These two perturbations increase the acceleration of JWST from its orbit about L2, and necessitates more frequent orbit maintenance (station keeping) maneuvers than other Lagrange orbit missions (which are typically 3–4 times per year).
Thus, for station keeping JWST uses thrusters, while maintaining relative sun-pointing requirements, as follows:
Orbit perturbations along the Sun-L2 axis have the greatest impact on-orbit stability. Thrusters are mounted on the spacecraft bus on the side of the sun shield facing the Sun; those used for orbit correction are oriented as far away from the sun shield as possible, and the sun shield can support a larger sun-pitch angle1 for orbit correction than is allowed for science operations. This architecture allows thruster firing at angles up to 90 from the Sun consistent with Sun avoidance restrictions, which is sufficient to provide orbit correction in all cases.
For momentum management, JWST suffers from massive momentum buildup, as suggested in the question, described here.
During science observations, the observatory will be pointed at a target, in an orientation at which the sun shield center of pressure is not aligned with the observatory center of mass. As solar photons hit the large sun shield, they place a torque on the observatory as a whole. The attitude control subystem (ACS) counteracts this torque by appropriately changing the spin rate on the reaction wheels, with the consequence that angular momentum accumulates in the reaction wheels. Momentum accumulation depends on the solar pitch angle, the roll orientation of the telescope, and the visit duration at a particular pointing position. The angular momentum (spin rate) of the reaction wheels must be managed to be kept within operational limits.
Mission planners are creative in using a technique for momentum management that is passive:
Momentum changes can be managed at some level by the way a sequence of observations is planned; this is done by observing at an orientation that builds momentum in a particular reaction wheel, followed by an observation at an orientation that removes momentum from that wheel.
But, not always, as some need-based science require a quicker slew and orientation which overrides the above momentum management program, and hence "momentum dumping" is performed by unloading the wheels as required.
However, managing momentum is only one of a number of planning constraints. At some point, one or more wheels will need to be adjusted to stay within operational bounds. The planning and scheduling system inserts planned momentum unloads into the schedule as needed, based on the modeling of expected momentum buildup, currently expected to be 1–2 times per week. Each unload activity takes a few hours, in which the observatory slews to a particular orientation to minimize the impact on the orbit and then fires thrusters as needed to allow the spin rate of the reaction wheels to be adjusted.
The orbit will be biased to compensate for mean outward forces associated with gravitation of the planets and radiation pressure on the sun shield.
Above quoted passages are all from the PDF JWST Cycle 1 Documentation for Telescope and Spacecraft found on this page
Re:So how does this remain in L2? (Score:4, Funny)
From the JWST user documentation:
Which, judging from the assembly procedure, comes from IKEA.
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If even one of the thousands of cam nuts on the telescope blows out of its particleboard hole, it's going to be $10 billion down the drain.
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Umm... Whoosh?
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So why the shield does not act as a sun sail to blow it out of L2?
Engineers thought of this problem and designed a counter for it. There is a piece that sticks out at an angle and provides a counter force to balance out the solar sail effect.
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So why the shield does not act as a sun sail to blow it out of L2?
It does! The problem is actually that it torques the craft around, not that it pushes the craft back.
There is a comparatively small flap of shield at the aft end of the spacecraft, which torques the craft in the opposite direction of the torque produced by the main shield. I'm not sure how the mechanics of that work, I believe that it was explained in either a Scott Manley video or a Marcus House video.
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See
https://solarsystem.nasa.gov/r... [nasa.gov]
for more details.
JWST goes to L2 ("behind" Earth) and it will keep Earth, Moon and Sun behind its single "sun shade". This keeps it close enough to Earth, at 5 light-seconds away - Moon is at 1.3 light seconds.
Not to mention that the mind enslaving effect of 5G, 6G, mmWave towers is reduced at L2. Also, people on Earth won't be able to use high power lasers to "blind" it (like they do to airplanes).
JWST will only make observations "away" from the Sun. Fortunately, Earth r
Current Status (Score:5, Informative)
This page shows the telescopeâ(TM)s current status and what it looks like. https://www.jwst.nasa.gov/cont... [nasa.gov] It looks like the side mirrors have to unfold and the secondary mirror struts have to move into place too.
Re: Current Status (Score:3)
There is also a cool link on that page that shows all the deployment steps: https://youtu.be/RzGLKQ7_KZQ [youtu.be]
Re: Current Status (Score:2)
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It will be unfortunate if either (or both) of the side mirrors fails to unfurl, but even if both fail the telescope still has 2/3 of its collecting area.
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And now that is successfully done!
Is the future of telescopes giant or tiny? (Score:2)
Is the future of space telescopes (or any, actually) a large number of small telescopes deployed into space and then aimed at the same spot and their images stacked together (think of each of JWSTs hexagon mirrors free floating in space as an array of independent telescopes?) Or is it massive telescopes as one structure (like JWST?) I think it is the former. I have seen what great images image stacking can produce using a small telescope on Earth even though it has to deal with the Earthâ(TM)s rotation
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At some point you want all the photons you can muster to hit the same detector to get readings above the noise floor. If you can make quiet enough detectors then stacking will work fine too.
Re: Is the future of telescopes giant or tiny? (Score:2)
Ok but isnâ(TM)t that a function of probability that can be accounted for by deploying a larger number of small telescopes? Hopefully not an insanely larger number though. Like, say the JWST requires 18 mirrors segments. Maybe the same image can be had with 24 telescopes each having a mirror the same size as a JWST mirror segment. That would reduce the risk and also allow some observations of different areas of the sky when the full array is not needed to point at the same area. Also the chance of mis
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Let's say you have one photon/pixel/sec equivalent noise (made up numbers) it gets really hard to pull signal out if you've got fewer photons/sec coming in. Large mirrors increase the signal to noise ratio which helps you discern if your measurement is real or a processing artifact.
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Ok but isnÃ(TM)t that a function of probability that can be accounted for by deploying a larger number of small telescopes?
Unfortunately no, not for optical telescopes.
The reason is that the resolution (as in resolving power, how many degrees apart can you separate point sources) of the image is in proportion to the size of the mirror. This is because broadly speaking, waves passing through a gap (or bouncing off a mirror) diffract and so spread out, and the larger the mirror, the smaller the diffracti
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Stacking is a way to simulate a longer exposure time. This is what is already done with Hubble, for example. Some of the well known Hubble images are made of hundreds of exposures because each individual exposure is limited in time. If there were twenty Hubbles all operating at once... Yes, you could in theory make the same image in less time but it's not necessarily worth the money investment. It would be very expensive, and the size of the optics would still limit the resolution to what the Hubble can do.
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You don't use multiple space telescopes for that. You integrate images over time. That's what Hubble's deep fields are.
The point of having multiple telescopes is to spread them out and do interferometry. We'll be doing that with radio space telescopes soon, but it's much more difficult at higher frequencies, so it's unlikely we'll be doing it in space for another generation or two.
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Shorter wavelen
Show us creation! (Score:2)
Really? (Score:2)
I thought the earth would be its sun-shield, did I miss something?
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Yes, only the last 20 years of design, a dozen Slashdot articles over the years, and the last few weeks of intensive press coverage. There is AMPLE material out there on why JWST has a sunshield, why it is not in Earth orbit, and the complicated deployment after launch. Snark in a Slashdot forum is not the way to get an answer to your question
To quote Shawshank: How can you be so obtuse...is it deliberate?
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"How can you be so obtuse...is it deliberate?"
You can't possibly expect us to RTFA.
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Your response, on the other hand...
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Perhaps the constraints should have been changed to allow a simpler design, but we're 20 years too late for that to happen.
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The Curiosity rover's landing system was Rube Goldberg-esque also, and I was really concerned. NASA has been gambling with complexity, and so far it's been paying off. We'll have to see how long the streak continues.
There is a tendency with NASA to get too brave, have an embarrassing failure, and then back off and stay conservative until a couple of successes, rinse, repeat. The "gamble" in the 90's was to try for a lot on a budget, but it backfired too often.
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Leading to the phrase, "Faster, better, cheaper. Pick two."
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The Curiosity rover's landing system was Rube Goldberg-esque also, and I was really concerned. NASA has been gambling with complexity, and so far it's been paying off.
The trouble is, space is hard, and physics is implacable. It's also NASA's job to break new ground; retreading and optimizing existing ground is what private companies can do a good job at. It's also not like NASA are a bunch of nitwits who keep reaching for complexity because that's what they do.
Everyone remembers the "space pen" story where
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All reliable engineering is based on KISS.
Sure, like modern cars with several times more parts than a 1970s car are so much less reliable. Whoops, that's backwards. Sorry, more like like a solid iron part withstands the elements better than an alloy with a prepared surface and several layers of paint on it. Actually, scratch that, that's more reliable too. Sort of like how you can bend a phone charging cable a lot more times than an elbow, which has so many parts and subparts as to be almost uncountable. Oops, I did it again. Elbows are way more re
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KISS at work: Tesla moving to "one piece" rear suspension assembly: https://evannex.com/blogs/news... [evannex.com]
Basically this is an awfully complicated and expensive way of making something "simpler" - and ultimately cheaper.
Unfortunately for the KISS principle, even the "simplest" way of adhering to JWST requirements is awfully complicated (in full and in details), and if you add redundancy, long term reliability, ... into the mix it gets complexer and complicateder fast.
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Just don't try to hold a bit firmly in a keyless check. The key system provides substantial mechanical advantage (it takes many revolutions of the key to rotate the chuck once), allowing the chuck to grip the bit with far more force than a keyless chuck can provide. Which can make a huge difference when drilling through especially hard materials - especially for people without really strong grip strength.
I'd love to see hybrid chucks in circulation - nothing about adding nice large-diameter grippy surface
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Seems to me like a keyless chuck could be designed so that you could get a similar mechanical advantage just from rotating the keyless chuck mechanism, you just have to rotate it more. It could even potentially be designed so that you can rotate with a 1-1 ratio until it experiences enough resistance, then it switches the ratio. That would definitely be a lot more complicated, especially in a rotating drill head that needs to be both lightweight and balanced, but it would meet the requirements of the origin
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Not really - no matter how much mechanical advantage your keyless chuck has, a key will always add more on top of that. In fact, the difference gets larger the bigger and grippier the chuck
Imagine a hybrid chuck that lets you tighten it by either hand or key. Say with a "ring valley" between the two halves of the keyless chuck, in which the ring gear and key operate
If you figure you get what, 3 key revolutions for 1 ring-gear revolution? That means that right off the top you get a 3x torque multi
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“Give me a place to stand, and a lever long enough, and I will move the world. ” --Archimedes
So, I totally get it, but at some point it's tight enough and past that it's being over torqued and damaged. Consider also that you could design a drill with a chuck-tightening mode where a pin or set of pins or some other locking mechanism pops out of the drill body temporarily and then the drill motor is used to tighten it.
The real point is that there are a number of designs that are more complicated i
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I have broken some reasonably large (~1/2") bits with my Ridgid brushless subcompact cordless drill... without the chuck slipping. And it's keyless. There is nothing wrong with a quality keyless chuck. Most of them are just shit.
Re:That design _is_ too complicated (Score:5, Insightful)
All reliable engineering is as simple as possible *and no simpler*. Building something that's going to sit in direct sunlight, in space, maintain temperatures a few degrees above absolute zero, and do so for more than a decade, is a pretty stiff set of requirements. Oh, and it all has to fit in a rocket fairing and take 10 gees.
Webb isn't something some grad student cooked up on a weekend bender. It's been developed over a couple decades and has contributed to and benefitted from a couple decades worth of stuff used on lots of other spacecraft.
The designs for it's successor look pretty much like Webb but scaled up because physical reality is physical reality. The successor might not have as many motors simply because I suspect it will be assembled in orbit because there will be no reasonable way of fitting it on a rocket in one piece.
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Any links to the successor? I hadn't heard anything about that.
Seems to me that, assuming Starship is viable, all but the largest space telescopes could actually get a lot simpler. Aside from the sun-shield, the fully deployed JWST with its 6.5m primary mirror would easily fit within the 9m Starship fairing without any need for folding parts, and a 9m telescope would capture almost twice the light. Not quite as big a leap as from the Hubble to the Webb, but still a substantial improvement, and would mean
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"6.5m primary mirror would easily fit within the 9m Starship fairing without any need for folding parts"
The integral mirror would then need to withstand the 4+G acceleration of a launch. It might be an easier problem, but a problem it still is.
(and you could spend more fuel for a longer launch with lower maximum acceleration, trading one cost for another).
But yes, once Starship is a proven launch platform, a "much better in some ways than JWST" project could be done in 1/10th of the time and 1/10 (or less)
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The sun shield and solar panels still would not fit unfolded, so there would need to be some folding. Also, if you have a bigger rocket, you'll want to scale the whole thing up like you said, but the goal would probably be for even bigger than 9 meters. At that point, you're right back to needing to fold it again.
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I'm pretty sure that unfurling a flexible one-piece sun-shade (or a stack of them) is going to require a lot fewer parts and a lot less development cost than unfolding a precision mirror than requires micrometer-precision alignment. Especially since each segment of the telescoping arms could be almost 9m long.
And sure, researchers will always want bigger, but they're not the ones paying for it. Those deciding which projects to fund are (hopefully) attempting to get the most research bang for their buck -
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I'm pretty sure that unfurling a flexible one-piece sun-shade (or a stack of them) is going to require a lot fewer parts and a lot less development cost than unfolding a precision mirror than requires micrometer-precision alignment. Especially since each segment of the telescoping arms could be almost 9m long.
Maybe, but this thread started because the summary talked about doubts of the wisdom of a complicated design. From the article itself:
The deployment of the five-membrane sun shield is a triumph for the engineering teams at the US space agency (Nasa) and the American aerospace manufacturer Northrop Grumman.
There were many who doubted the wisdom of a design that included so many motors, gears, pulleys and cables.
But years of testing on full-scale and sub-scale models paid dividends as controllers first separated the shield's different layers and then tensioned them.
So the topic of conversation here was the complexity of the sunshade.
And sure, researchers will always want bigger, but they're not the ones paying for it. Those deciding which projects to fund are (hopefully) attempting to get the most research bang for their buck - and if you can launch an insanely-large-array of a (few?) dozen relatively simple 9m telescopes separated by hundreds of thousands of miles, for the price of one intricate 30m telescope... you're going to need to have some pretty specific and very promising research threads to justify the 30m one.
True. Especially for supercolliders. As far as numerous "small" telescopes instead of one big one, wouldn't it be nice to have both? But yeah, there is such a thing as a budget.
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https://asd.gsfc.nasa.gov/luvo... [nasa.gov]
A 15 m mirror is being planned for LUVOIR. Now that Webb has demonstrated you can make folding mirrors, we're going to make folding mirrors for space telescopes because the aperture gain is just too compelling. And for anything that works in the IR, you've got to have the sunshade, which needs to be a lot bigger than the mirror. The other tricks people would like to implement, like starshades for directly imaging exoplanets, are even bigger.
I hope Starship won't just give us
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The successor would be LUVOIR. It is intended to work in the UV-visible-near IR spectrum, so it would be the successor to Hubble, not to JWST. It comes in two options, one with a 15m mirror, the other with a 8m mirror, both folding.
The 15m version is intended to be launched by SLS, but I guess Starship could do, they are similar sized rockets. The 8m version is intended for a more typical heavy lift rocket.
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"that's going to sit in direct sunlight, in space, maintain temperatures a few degrees above absolute zero, and do so for more than a decade, is a pretty stiff set of requirements"
Not to mention a very interesting mass limitation (every extra kilogram in "scientific" satellite mass means several weeks of station-keeping lost)
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All reliable engineering is based on KISS.
Super false. The entire idea of redundant backup systems proves you wrong. It's literally added complexity for reliability.
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All reliable engineering is based on KISS.
Super false. The entire idea of redundant backup systems proves you wrong. It's literally added complexity for reliability.
You do not understand complexity. It is not a simple number. Adding redundancy needs to reduce effective complexity overall or it makes the situation worse.
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Good grief. I just noticed that you were modded down as overrated and flamebait. I have issues with overapplication of the KISS principle, Ockham's razor, etc. but your post was a perfectly good one and not flamebait at all. I don't have any mod points at the moment and I've posted already anyway, but I wish I had some to help undo the obvious the moderation abuse. It really has gotten out of hand lately. I'm assuming that you just have a stalker with some sockpuppet accounts.
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No updates about that ?
Not that I could find with a cursory Google search. Do you have something to share, or just trolling?
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There are some switches that were supposed to indicate that the sun shade covers had rolled up. For whatever reason they didn't get that indication. They used other methods to determine the covers were indeed rolled up, and the shade is now properly deployed. This idiot keeps trying to make a big deal of this, even though it had no impact on the mission. He is just a troll.
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No, correct0r has been carping on about that for days. The tone of the comments suggests that he (she? it?) thinks that NASA is being sloppy, or is covering up some really egregious failure, or some other nefarious thing. In other words: correct0r is definitely the only one who's right - Cassandra shouting to the wind - and all the folks at NASA and Northrup Grumman who have spent
Re:thousands of parts that must function harmoniou (Score:5, Informative)
This is probably what you're talking about.
https://blogs.nasa.gov/webb/20... [nasa.gov]
https://blogs.nasa.gov/webb/20... [nasa.gov]
https://www.cbsnews.com/news/j... [cbsnews.com]
What happened was that during the shield deployment they observed it was moving slower than expected, possibly due to motor temperature not being optimal. This was one of those possibilities that was anticipated. They called a delay to verify that's what was happening. Not a big deal, right?
But the instant the delay was announced the usual "USA has failed again" trolls leaped into action and announced secret breakdowns and a coverup. And some people were stupid enough to repeat it.
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Apparently it's a delay of minutes or hours on top of the 20 years delay of the original JWST project.
Nothing to write home about, and there are basically plenty of cheap solutions to check that - DSLRs with telezooms are out, but even university level optical telescopes might be able to get good enough images.
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