[HN Gopher] Neutrons prove 'Bond villain' did not cause Arecibo ...
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Neutrons prove 'Bond villain' did not cause Arecibo telescope
collapse
Author : dcminter
Score : 122 points
Date : 2023-08-29 11:20 UTC (11 hours ago)
(HTM) web link (www.ornl.gov)
(TXT) w3m dump (www.ornl.gov)
| simonhamp wrote:
| It's cool that something good can still come out of this
| "disaster" - it's a shame that it wasn't kept up, but if this
| sort of forensic analysis reveals ways to improve cable
| manufacturing or maintenance routine improvements, that feels
| like a pretty good win
| adrian_b wrote:
| It is well known that zinc, like all metals with low melting
| temperature, flows slowly under high stress.
|
| So this failure was easily predictable. I assume that the
| cables have been designed for a much shorter lifetime, so it
| was expected that either the cables would be replaced or the
| radiotelescope would be decommissioned many years ago.
|
| Nevertheless, the choice of pure zinc for the cable sockets is
| somewhat weird, because it guarantees a short lifetime. Had a
| zinc alloy been used, like ZAMAK (Zn-Al alloy), the flowing
| speed would have been much less and the lifetime of the cables
| would have been greater.
|
| Alloys are much more resistant to plastic deformation and
| flowing than pure metals, because the atoms with different
| sizes cause defects in the crystal structure that prevent the
| easy slipping of the atom planes over each other.
| nullc wrote:
| https://www.nsf.gov/news/special_reports/arecibo/Arecibo-
| Tel... Go to pdf page 53-ish.
|
| They show the zinc doesn't continue to creep if the load is
| below a threshold-- technically the zinc doesn't creep if
| it's not subject to persistent shear forces, which is won't
| be if the cable load is below a threshold as the wires take
| up the load. This essentially results in a long term capacity
| which is different from the short term capacity.
| Unfortunately the ratio between the two depends on the wire
| splaying geometry which isn't well controlled, resulting in
| wide differences.
|
| The report concludes that if it had been built to a safety
| factor of 3 rather than 2, the issues wouldn't have been
| experienced. Alternatively, the failure could have been
| avoided by reacting to flow over some threshold (which was
| noticed well in advance, but not reacted to)
|
| Presumably we don't see similar failures in sockets in
| suspension bridges because they're built at a safety factor
| of 5+ and usually that's a SF over their rarely reached
| maximum load rather than a factor over their 24/7 load.
| roberthahn wrote:
| Could you cite sources? Specifically, when was it discovered
| that zinc flows under high stresses? By whom?
|
| (Not a materials engineer so I'm not sure what to search for)
| adrian_b wrote:
| Any handbook about the strength of materials has a chapter
| about creep a.k.a. cold flow.
|
| The handbooks from immediately after WW2 already included
| such a chapter, but I believe that the first studies of
| this problem must be much older.
|
| When any metallic structure is designed, it must be
| verified that it will not fail in any of the possible
| modes, including due to flow over the intended lifetime.
|
| See in:
|
| https://en.wikipedia.org/wiki/Creep_(deformation)
|
| at "Temperature dependence".
|
| By the approximate rule mentioned there, zinc begins to
| have non-negligible creep already above minus thirty
| Celsius degrees, so at normal ambient temperatures you must
| always compute the creep of zinc for any structural design.
|
| On the other hand, metals like iron or copper have
| negligible creep at room temperature, even when pure.
|
| Aluminum and magnesium begin to have non-negligible creep
| at temperatures only a little above normal ambient
| temperatures.
|
| Hard alloys can have much lower flowing speeds than the
| metals included in their composition.
|
| In integrated circuits, the metal connections are affected
| by electromigration, which is the flowing of the metal due
| to electrical current instead of mechanical stress.
|
| The electromigration properties and creep properties of a
| metal are closely related. In the beginning, the ICs used
| pure aluminum for interconnections, but when their size was
| reduced, the connections began to fail after a too short
| lifetime.
|
| The first solution for this problem was the replacement of
| pure aluminum with harder aluminum alloys, including small
| quantities of copper and/or silicon.
|
| When the ICs became even smaller, the aluminum alloys had
| to be replaced with a metal having a higher melting
| temperature, i.e. copper, which fortunately also has a
| lower resistivity.
| roberthahn wrote:
| Thank you for the information!
|
| Sometimes it's worth pausing a moment when seeing a "It's
| well known that..." to check the timeline because the
| construction of Arecibo might well have taken place (or
| planned) before it was known (let alone well known).
|
| Edit: a bit more searching suggests that this was studied
| in 1947 (Andrade's Creep Law and the Flow of Zinc
| Crystals, by AH Cottrell)
| RajT88 wrote:
| This feels like the facility was in operation for so
| long, that the people who knew about this potential
| problem all retired and with them went that knowledge.
| sheepshear wrote:
| Andrade is the namesake of Andrade creep due to his work in
| the early 1900s, but the existence of creep had been known
| for a long time by then. I'd imagine smiths have been aware
| of creep throughout the history of metallurgy.
|
| https://royalsocietypublishing.org/doi/10.1098/rspa.1910.00
| 5...
| eggy wrote:
| Cable tension systems are very tricky to engineer, and Arecibo
| was built quite a while ago. If you use fixed, non-adjustable
| cables, you still need to tension them again after installation
| to allow for settling to balance tension on all the wires. I
| don't know much about Arecibo, but having strain gauges on each
| wire, some can be built into the assembly, would allow monitoring
| and possible automatic tensioning systems to balance the loading.
| Even in a system of many cables, the load shifts with wind and
| geological shifting of foundations, and sometimes for brief
| periods a few of the many cables take the majority of the load
| leading to differences in strain or stress.
| WJW wrote:
| TIL that creep can even happen at room temperature (albeit
| Caribbean room temperature) if the stresses are great enough and
| the time span long enough.
|
| I always thought that it was more a thing for objects like jet
| engine turbine blades, that get very hot as well as having very
| great forces acting on them.
| thsksbd wrote:
| Transport properties all "happen" at any temperature. The rate
| is exponential with T, though, so at some point you dismiss it.
| Kinetics usually (always? Who remembers? ) is continuous with
| T.
|
| Phase changes, on the other hand can happen abruptly wrt T
| (first order, melting/boiling ice), or gradually (second order,
| curie transition, boiling mixtures).
|
| Of course, first order transitions require a pure substance
| that doesn't actually exist since the chemical potential is
| infinite at infinite dilution. But that's entirely academic.
|
| EDIT: I forgot to mention that creep has many proposed
| mechanisms and their relative contribution is not fully
| understood; however most depend on a transport phenomena,
| typically diffusion.
| WJW wrote:
| Diffusion of atoms through solid materials is one of those
| things I intellectually know happens, but still don't really
| grok. Sintering is one of the weirdest things.
|
| Why does squishing things together AND warming them up cause
| the particles to stick together more than when you just
| squish them together or just warming them up?
| imchillyb wrote:
| > Why does squishing things together AND warming them up
| cause the particles to stick together more than when you
| just squish them together or just warming them up?
|
| >> The equations describing these laws are special cases of
| the ideal gas law, PV = nRT, where P is the pressure of the
| gas, V is its volume, n is the number of moles of the gas,
| T is its kelvin temperature, and R is the ideal (universal)
| gas constant.
|
| >> https://pressbooks-
| dev.oer.hawaii.edu/chemistry/chapter/rela...
|
| The laws of thermodynamics describe how gases work, those
| laws cause the effects you're asking about.
|
| The above is a bit much for a primer on the topic, but
| provide enough key words for a Google-dive into the
| subject.
| WJW wrote:
| Did you miss the part where I was talking about sintering
| and diffusion of atoms in materials in their solid phase?
| A quick search in the article you linked shows zero
| results for either "sintering", "diffusion" or related
| terms.
|
| The ideal gas law is very nice but hardly applicable to
| describe things like creep in metals under stress, let
| alone things like the grain boundary diffusion mechanism
| for sintering metal particles together.
| salawat wrote:
| What is a solid but a, relatively speaking, very, very
| cold gas?
|
| Put two solids together with no intervening medium, and
| heat everything up, and you'll see some mixin' and
| mingling. Often, the reason you _don 't_ see more of that
| sort of thing is because everything is immersed in an
| oxygen rich fluid with a tendency to create large,
| relatively reluctant to mix and mingle oxide coatings
| before anything fun can happen. Hence why another word
| for cold welding is vacuum welding.
|
| Materials, when you really look at em' are not as 'solid'
| and 'stable' as you may think. Hence why I have a
| mechanics of materials book I peruse from time to time.
| thsksbd wrote:
| Diffusion:
|
| Its not hard to understand once you see the mechanism in
| full (vacancies, interstials, etc) but its hard to write as
| txt.
|
| Suffice to say, there's plenty of room to squeeze.
|
| "Squeezing"
|
| When you squeeze you get rid of air bubbles, right? Well,
| when you squeeze you get rid of boundaries which are really
| volumes at small scales.
|
| Well nature hates surfaces, so if you squeeze surfaces
| close enough together and hot enough you'll give the
| material an opportunity to rearrange atoms to get rid of
| boundaries.
|
| "Ostwald ripening"
|
| If you thought sintering and diffusion are hard, I had a
| respected mechanical engineering professor working on a
| refractory materials project claim, when he first
| encountered it, that Ostwald ripening cannot occur.
|
| The mtls Eng guys rolled our eyes...
| hansvm wrote:
| Squishing is important, else the forces involved are
| negligible. Warming them up increases their movement and
| thus the likelihood of a number of things (including random
| interactions with the thing they're squished against).
|
| You might also be interested in cold welding.
| https://en.m.wikipedia.org/wiki/Cold_welding
| mensetmanusman wrote:
| https://youtu.be/EXbiEopDJ_g?si=pXwPNdH8d-AHAf2b
|
| Dislocation motion looks cool too. Fun math behind these
| strings of holes in the atomic structure.
| aidenn0 wrote:
| Different metals behave differently. Zinc exhibits creep at a
| much lower temperature than most (all?) steels, for example.
| h2odragon wrote:
| Trying to think about the forces on the ends of the cables;
| when the wind is blowing and the big weight they support is
| bucking and the resonances of all these waves are interacting
| among all those cables... I kinda suspect there were
| instantaneous loads at times that were several multiples of the
| static weight. kinda expect that would count for more. Not that
| I know anything about it :)
|
| It stood for as long as it did, and had more weight added than
| the original design called for: thats a pretty good win for the
| original design, i think.
| sandworm101 wrote:
| At these scales, at this length of cable, they would stretch
| enough to soften most instantaneous loads.
| HPsquared wrote:
| Failures due to creep deformation are pretty common in solder
| joints - driven by residual stresses created during assembly
| which persist over a long time, and eventually lead to cracks
| forming (stress relief - but not so good for the connection).
|
| Usually not an issue at room temperature, but it can happen -
| solder has a low melting point.
|
| In the case of the observatory, the failure happened in zinc
| components, which has a fairly low melting point.
|
| Turbine blades are just one of the most extreme examples, it's
| really hard to make a metal that resists creep in that
| environment.
| toss1 wrote:
| The metal technology is outdated for this kind of structure
|
| This should be rebuilt with far lighter weight carbon fiber
| composite structures for the suspended equipment and far higher-
| strength and lighter weight carbon fiber rope/cable.
|
| Both technologies are very well developed and proven. Structural
| carbon fiber is used in everything from aircraft [2] to buildings
| to bridges [1], and it is only carbon fiber ropes that allow
| elevators to work in new kilometer-tall buildings [0].
|
| Merely reducing the weight alone reduces the stresses involved in
| supporting the required equipment, and even greater benefit and
| safety margin is gained with the higher strength of engineered
| composite materials.
|
| Time to rebuild with the next generation of technology.
|
| [0] https://www.compositesworld.com/articles/in-super-tall-
| build...
|
| [1] https://www.compositesworld.com/products/creative-
| composites...
|
| [2] https://hexagon.com/resources/resource-library/composite-
| mat...
| philipwhiuk wrote:
| If the wires snapped, surely fault was actually Bond's.
|
| Metallic Bonds' that is.
| [deleted]
| falcor84 wrote:
| Does it use 'Bond villain' rather than implicitly mention Sean
| Bean in order to avoid spoiling the demise of a character in a
| movie from almost three decades ago?
| Cthulhu_ wrote:
| I remembered it was a villain, I didn't remember it was played
| by Sean Bean so, more effective headline for me personally. I'm
| not sure why you honed in on that though.
| WJW wrote:
| Oi! Spoilers!
| moffkalast wrote:
| - guy walking into aftermarket auto parts store
| barrysteve wrote:
| They spoiled most of the movie in the trailer, back in 1995.
|
| My friend still to this day says he would have preferred to go
| in blind, not knowing who the bad guy was. It would have been
| an epic reveal.
| mrguyorama wrote:
| I don't intentionally watch movie trailers for this very
| reason.
| pimlottc wrote:
| Or they just assume most people aren't familiar with the
| characters from every random Bond movie?
| mtlmtlmtlmtl wrote:
| Fair assumption, although Goldeneye is easily one of the best
| Bond movies, if not the best. Personally I remember more
| about that movie than I do about the whole rest of the
| franchise combined.
| mcpackieh wrote:
| Goldeneye is among the best, but for my money I think
| Timothy Dalton gave us the best Bond performances we're
| likely to ever get. Brosnan did it well, but Timothy Dalton
| just oozed cool killer vibes.
| schnitzelstoat wrote:
| It's Alec Trevelyan.
|
| I played the N64 game so much as a kid I can probably name
| almost all of the characters in Goldeneye.
| mig39 wrote:
| It's not a spoiler. If Sean Bean is in a movie or TV show, he
| will die.
| c-linkage wrote:
| He didn't die in the _The Martian_ or _Ronin_, but he was
| fired from his job in both movies.
| NooneAtAll3 wrote:
| Not remembering Sharpe... Now that's not soldiering
| sideshowb wrote:
| Isn't the modern consensus that Sean Bean being cast to play a
| character carries that information implicitly?
| mjb wrote:
| Metallurgy is super interesting. The fact that metals - these
| crystals that would be super brittle and stiff except for a few
| dislocations - can creep like this is amazing.
|
| My (slightly) tongue-in-cheek proposal for Arecibo: drones.
| Instead of trying to hold one big antenna up with huge cables,
| you use an array of antennas flying above the dish on drones.
| This allows for low cost, easy beam steering (within the limits
| of the shape of the dish), adaptation for different frequencies,
| quick stowing when weather arrives, etc. Even station-keeping to
| the required accuracy doesn't seem that hard (you might have to
| do some active phase correction). Disadvantages are that you'd
| need to digitize on each drone (which might bust the whole
| scheme, SNR-wise), and that drones are quite electrically noisy.
|
| More here: https://brooker.co.za/blog/2021/08/11/arecibo.html
| adolph wrote:
| Why would you use drones rather than a flat stationary phased
| array?
| syllablehq wrote:
| Interesting - you might be on to something. Hmm, maybe it's not
| quite drones (because the limitations you mentioned like
| electronic noise, etc) maybe it's some other autonomous
| swarming unit. Maybe they are drones, but you use some kind of
| floatation like helium or hydrogen to reduce power needed and
| therefore noise. Maybe you physically connect each of them in
| some way in a compression/tension webbing that can be adjusted
| to control swam unit positions instead of using drone
| propellers. Fun idea :)
| eggy wrote:
| I think the hurricanes and storms would do more than "shake,
| not stir" the drones, especially the helium-filled drones ;)
| hwillis wrote:
| DJIs biggest drone is over 1m wide and can carry a 6 kg
| payload.
|
| If you could make a suitable receiver that weighed 6 kg or even
| 600kg, you could just suspend it from motorized plastic cables
| on space frame towers. Drones aren't going to make it cheaper
| or easier.
| mjb wrote:
| I suspect you could make the receivers weigh single digit
| grams, depending on the band.
| tbalsam wrote:
| Anyone that remotely touches any ODEs relating to this line of
| work just had a heart attack and fainted.
|
| We don't need a roaring 20's prohibition-era jiggly jazz fest
| on our energy packets, this sounds absolutely nightmarish for
| anyone below a management position having to work with it. :(|)
| phyzome wrote:
| The electrical noise from the drones is probably
| insurmountable.
| ooterness wrote:
| "If you were plowing a field, which would you rather use: two
| strong oxen or 1024 chickens?" -Seymore Cray
| dtgriscom wrote:
| Chickens apply fertilizer as they plow.
| HankB99 wrote:
| As do the oxen.
| dev_tty01 wrote:
| I wonder how well the poop/work ratio scales between
| chickens and oxen?
| atonalfreerider wrote:
| It was James Bond himself that destroyed Arecibo, not his former
| 00 partner Alec Trevelyn.
| philipwhiuk wrote:
| If you read the article you'll find it was actually his long
| time partner, Covalent.
| enkid wrote:
| Only because it was being used to control an EMP satellite set
| to destroy London.
| downvotetruth wrote:
| James admitted it was for himself rather than a bond to duty.
| gonzus wrote:
| TIL that the concave dish surface was actually spherical and not
| paraboloidal, as I had always assumed.
| jacquesm wrote:
| The main dish is fixed, they move(d) the receiver around to
| steer it, with a paraboloidal dish that would not work (because
| the focal point would be fixed).
| HPsquared wrote:
| Did they apply any corrections for the spherical aberration?
| PopePompus wrote:
| Yes. Initially the receivers had very long linear feeds,
| because a spherical mirror focuses to a line, not a point.
| Later additional mirrors were added to partially correct
| for spherical aberration.
| dcminter wrote:
| I know, I know, clickbait title - but it's an interesting read
| and the title is amusing at least!
| ourmandave wrote:
| A reference to Goldeneye (1995) that featured Alan Cumming as
| Boris Grishenko, the most obnoxious programmer on the planet.
|
| Rumored, but proven not to be, invincible.
| hef19898 wrote:
| Rumor has it he might have ultimately been defeated by brushed
| steel Parker pen. Rumor also has it that those pens became sort
| of a must have in the late 90s. Maybe those incidents are
| related, we will know more when his Majesty's Secret Service
| declassifies the files in 100 years or so.
|
| Or we ask Pierce Brosnan, I have the feeling he was involved in
| this somehow...
| pelagicAustral wrote:
| > the most obnoxious programmer on the planet
|
| hahaha Not by far... I used to work with an Erlang programmer
| (probably not really the reason he was so eccentric), and this
| guy was by far so full of oddity that was almost impossible for
| anyone else in the office to tolerate him. A brilliant
| programmer, but utterly incapable to having other humans
| around.
| dsabanin wrote:
| I think I know that guy.
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