strange interaction between radio and zinc (arecibo telescope collapse)

[coppercone2]

Also, this document is more riveting then the best horror novel


I was wondering about how that thing managed to screw off so hard.

https://gizmodo.com/jaw-dropping-report-reveals-causes-of-arecibo-telescope-collapse-2000517284

“The only hypothesis the committee could develop that provides a plausible but unprovable answer … is that the socket zinc creep was unexpectedly accelerated in the Arecibo Telescope’s uniquely powerful electromagnetic radiation environment.”

Ah zinc, aluminums drunkard cousin, always causing trouble. 

It makes me think about the common parallel of 'do it yourself mechanical engineers' making creative low cost interconnect/electromechancial 'integration' in their designs to get rid of electrical hardware and the usual hilarious results, though in this case I think it really must have been something new, its too expensive and well studied to compare to a cheap flashlight.


Full report:
https://nap.nationalacademies.org/read/26982/chapter/1#xiv


Here is a spelter socket


It was always one of those things that told me 'stay away from cranes'. Their all over and seemingly safe, but I get the hebee jebees from that design.




Some basic insight that people might not realize to help understand why zinc is used instead of lead, which we all know and trust
-zinc is actually really strong. Its the one metal that melts easy, has a high tensile strength and its angry enough to bust through alot of oxides an stuff (making it a choice for aluminum soldering). Cleans nicely with HCl to form zinc chloride, which is a great soldering flux!

so for high tensile strength applications, zinc is actually pretty good, even though its kind of nasty to work with.


One idea that popped in my head is if process changes occurred. Like trying to get rid of HCl to make assembly greener or something.
I think I saw wire pull out of a solder joint when it was yanked before. Like, there was a joint (dirty) but the wire was firmly seated, however you can 'yank' it out slowly if you did not apply too much pressure to it. I wonder if there can be a situation where there is a mechanical friction bond to a rough wire.. then you have zinc change its crystal structure over time and gradually lose the mechanical bond.

I know its difficult because it took me a while to figure out how to get DIY lead hammers correct, which initially used lead cast over a shape. in the end I drilled a hole and put a bolt through it, then cast that into place, and it was much more secure then trying to get it to 'envelop' something smooth. I wonder if you can etch steel cable so the zinc adheres to it better too. I don't think its supposed to actually wet the cable, like my observation with the solder joint, its supposed to work like that dodgy solder joint...? Lol, or little bits of zinc soldered to the cable, stuff diffused making harder rough spots, and the rocking of the wind gradually broached it loose.

But what role did the RF play???

And how did you personally experience bureaucratic delays in decaying facilities ? personally I have seen
-flickering lights
-scary motor noises
-decreased food quality
-malfunctioning doors
-intralab furniture theft



Also, this article seems to support my theory that the eifel tower is good

[LM21]

Did Arecibo  transmit  too. I thought it  was only listening, or mostly so. Listening weak signals  does not cause  strong fields IMO. Everybody knows  this or what?

[coppercone2]

its a terawatt or more microwave radar


they mapped the moon with it. very powerful.

I don't think they built it in a way that it picks up more then some gentle side lobes on the cabling because thats a gigantic waste of money


that is a interesting point though, I wonder if there could have been some alignment mishap that caused it to irradiate its own structure somehow. i think they do some very high peak power tests. maybe they blasted it by accident and no one noticed. And call me paranoid but when I think of TW transmitters I start thinking maybe someone was nervous about it, like sabotage or some experiment gone wrong. I always thought it might have something to do with stealth technology development (perhaps someone thought it might be looking for stealth satellites in its time off). It always makes me wonder when a proven technology suddenly has a ton of gremlins for no good reason.


But the reasonable explaination seems to be that zinc is electroplastic and it can weaken zinc bonds from continous low currents, possibly more so then usual based on some manufacturing change of the cable bond over 50 years.

[Andy Chee]

Did Arecibo  transmit  too. I thought it  was only listening, or mostly so. Listening weak signals  does not cause  strong fields IMO. Everybody knows  this or what?

Arecibo has transmitted before in the past, most notably;

https://en.wikipedia.org/wiki/Arecibo_message



But Arecibo mainly functioned as a receive only antenna for radio astronomy.

For transmitting signals to Mars rovers, Voyager, or New Horizons Pluto, a separate dedicated network of dishes that comprise the Deep Space Network, is used to maintain communications, which avoids tying up radio astronomy dishes.

[coppercone2]

The average power is approximately 150kW with instantaneous power in the megawatts and focused peak power in the terrawatts (antenna power)

But if it was due to instantaneous peak effects I think they would see some shit go down there like in a microwave oven and it would be loud and sparky and there would have been soot inside of their cross section cutaways

[johansen]

They probably built it to map russian satellites.

[Andy Chee]

They probably built it to map russian satellites.

A fixed dish set into the ground like Arecibo, only has a 40 degree view of the sky at any one time.  Not sure such a limited view is useful for mapping spy satellites.

[coppercone2]

you can test your own though

[Andy Chee]

On a bit of a tangent, I don't know whether it's widely known that China commissioned a big fixed dish in 2020:

https://en.wikipedia.org/wiki/Five-hundred-meter_Aperture_Spherical_Telescope

It remains to be seen whether it is also subject to the detrimental effects that Arecibo suffered (obviously the Chinese telescope won't get hit by a hurricane).

[Andy Chee]

Also, FWIW there is a difference between radio astronomy and radar astronomy, the latter requiring transmitters.

[coppercone2]

I wonder if resistor VCR is related to EP

measure zinc resistor VCR

may be a interesting component if the property can be tuned, kind of like a bootleg limiter 

I thought about buying zinc for a very long time but I can never bring myself to do it. Maybe this is interesting to measure.

[CaptDon]

Remember the 'terawatt' figure is based on E.R.P. and at no point is there any power actually higher than the input power to the antenna. Any demise related to R.F. could come about in one of two ways. There will be a point along a radiator where the effective impedance is in the milliohms, therefore the theoretical current is insanely high and could do real damage. There is also a point where the impedance approaches infinity and the voltage gets insanely high causing arcing and pitting. Remember the old MFJ SuperLoop magnetic loop antenna which with 100 watts of R.F. input could approach 20KV across the resonantly tuned gap. The flipside to that is we could also surmise at some point in the base of the loop there could be predicted 20 Kilo Amps. But in the long run, RF probably had very little to do with the collapse!

[coppercone2]

They are saying the low RF current effected the zinc electroplasticity. The report basically says its the only thing that caused the collapse. Most other stuff was ruled out.

I think I noticed this myself when bending metal, I believe that maybe that 10% they are talking about is the difference that you feel while bending metal thats passing current (without undoing the clips) and bending metal after undoing the clips. For bending modest steel bars that are resitively heated by hand. but that is very high currents (kA). But I think I noticed it bends smoother if you run juice through it, rather then knocking off the clips and then bending it. I used to think it might just be cooling very quickly but I think that the 0.5 seconds it takes to knock off a big alligator clip might not be enough time to totally blame this on cooling.

While it is known to make things slightly weaker at high currents, it seems that zinc creeps more when its passing electrons. To me it make sense. I think I read some where that zinc wire was not suitable for fuses for some reason ( I wondered why they used solder alloy for this). Naturally you would think a high strenght zinc alloy with resistance might make for a better fuse then using lead (mechanically, shock resistance ,etc), and if the only problem was with overload at high currents, then you could still 'tune' a zinc wire to work in a fuse.. so that might imply there was some other consideration. I always figured that having a bunch of electrons going through something must do something, that it can't be totally isolated from mechanical properties.



The only data they have on zinc EP is on very high currents. This report suspects that low currents effect... a quantary or further parameter of zinc plasticity over a long time scale.

I know test engineers HATE this kind of long term experiment, everyone wants to 'proof' everything with a overload because its economical.


It may be of interest to people that setup their own low frequency antennas and stuff on a budget. It might be wise to invest in a crimp tool for cable rather then using zinc potting. 


And its a good lesson for all E engineers, that is, just because you see a mechanical assembly everywhere, it does not guarantee that it is the correct choice for electricity, and high lights the dangers of using something because it was 'proven' with use in unrelated systems with appealing performance data.

[ejeffrey]

But in the long run, RF probably had very little to do with the collapse!

It's a wonder the even bothered doing a study and writing a report when they could have just asked here for someone who didn't even take the time to read the summary page of the 100 page report before declaring the answer!

[Andy Chee]

I thought about buying zinc for a very long time but I can never bring myself to do it. Maybe this is interesting to measure.

How much zinc do you actually need in order to experiment with?  Zinc is readily available in the outer casing of carbon-zinc (unused fresh) batteries.



The video shows D size batteries, but I might suggest 6V lantern batteries.

[coppercone2]

a spool of fine zinc wire is expensive

wire rollers are also very expensive actually.

[Andy Chee]

Do you actually need zinc wire to perform experiments?

As I said, zinc pieces are readily available from carbon-zinc batteries.

[coppercone2]

I guess you can do bend tests but I wanted resistance tests and its hard unless its fine to measure resistance well

probobly never going to do that because its mega boring

The best test would be to get a temperature regulated bar of zinc that is measured in temperature and do hardness test on it with impactor , if you really want to measure electroplasticity. It should show up as a bigger impact with the electricity at the same temperature

[CaptDon]

Because it couldn't possibly be a C.Y.A. job for piss poor preparation, impurities, insufficient flux action and on top of that a style of termination that never should have been used in the first place. To say it was 'entirely' an R.F. related failure seems to be a bit of a stretch. Funny that there was no notice of the brush slowly working out of the choke. We inspect every aspect of our guy supports bi-annually. Usually spring time to examine damage from water/ice ingress during the winter months and in the fall check for rust / wind load / lightening damage that may have occurred during the summer. I am surprised they found RF to be 100% of the cause and not an 80/20 or 70/30 mixture of multiple factors. Was it insured? Some things just don't want to be found.

[coppercone2]

its pretty complicated you need to read the report to understand why they behaved the way they did

[CaptDon]

I had an 820 ft resting on one common pivot, 4 X 247 ft each on a pivot and a 450 ft three legged tower and so many towers at Vatnsendi it looked like a porcupine. Not one used any of that zinc pour stuff. Sad to think, what was the number '10% give way' caused the failure? Seems like in wind and weather it would have been engineered to survive constant stress in excess of 150% and transient stress of 200+%. Oh well, live and learn. I guess we won't see that mistake again outside of third world countries and under engineered shoddy workmanship and poor choices of components. B.T.W., I do see the rain water and ice slowly displacing our zinc coated components with the results staining the concrete pedestals at the guy anchors which eventually leads to guy wire rusting and cause for replacement. Most of our guy lines incorporate 'moose balls' or some call 'moose nuts' to absorb wind driven guy line resonances. I retired from that field about 20 years back with pension so I could go play with helicopters and trains, and earn another pension while also serving as a Merchant Mariner to this day.

[coppercone2]

no, the 10% is a figure quoted for material weakening on heavy current. Like if you pass 5000 amps through something and try to bend it. that is easy to measure. I think it goes normal when the electricity stops flowing. or mostly normal.


They said there is no data or figures for how low currents slowly effect the joint. it makes the zinc slowly fail. No one ever did the experiment in a way that you can get a 'table' from it.

I think they mentioned they wanted better grounds on it, and some of it has to do with shitty grounds (paint, repaint, again and again) that lead to stray paths

[johansen]

Testing this weird theory is going to take a decade.

[coppercone2]

If you scroll down here to Arecibo section, you will find a most interesting "what could have been" about the Arecibo telescope.


I wonder if they did the alternative design, would it still be standing
https://en.wikipedia.org/wiki/General_Bronze_Corporation

It could have potentially gotten 4 legs, or potentially even been made with a tower form (restricting its capabilities). I do wonder though, would the utility of it having been built in tower form, potentially lasting many more years, would it have provided more scientific insight then the 'better for rf' design.