The end of the line for the Arecibo radio telescope - Page 1
Forum section: electronics / general

author: Homer J Simpson
author_rank: Super Contributor
timestamp: November 19, 2020, 10:18:53 pm
content: https://www.space.com/arecibo-observatory-radio-telescope-to-be-destroyed

author: CJay
author_rank: Super Contributor
timestamp: November 20, 2020, 08:49:01 am
content: Damn shame and it looks like it might not be rebuilt but it seems demolition is the right decision.I wonder if they'll auction off bits of it as memorabilia

author: Gyro
author_rank: Super Contributor
timestamp: November 20, 2020, 12:29:06 pm
content: That's really sad. I would have thought that its construction would have made it ideal for cost-effectiveupdatingor at least replacement of the entire suspended section. It's an iconic structure.

author: Zbig
author_rank: Frequent Contributor
timestamp: November 20, 2020, 03:17:53 pm
content: I want off this fucked-up timeline so I went "Google, restart the simulation". She said she didn't understand

author: BravoV
author_rank: Super Contributor
timestamp: November 20, 2020, 03:38:22 pm
content: Well, at least its now covered by ->FASTand bigger, comparison of Arecibo's size vs FAST.

author: Kleinstein
author_rank: Super Contributor
timestamp: November 20, 2020, 05:16:53 pm
content: AFAIK the FAST dish is used under a relatively low angle, and not with the receiver suspended on top. This reduces the effective area quite a bit. So the actual effective aperture is not that much larger.With that type of damage and an already old structure the demolition is probably the only sensible decision. Chances are there will not be money for a quick rebuild. The last extension of support was already a close call.

author: BravoV
author_rank: Super Contributor
timestamp: November 20, 2020, 05:41:59 pm
content: Quote from: Kleinstein on November 20, 2020, 05:16:53 pm

author: coppercone2
author_rank: Super Contributor
timestamp: November 20, 2020, 10:49:37 pm
content: is that thing made of aluminum?I wonder why they can't fix it with careful welding and epoxy (reinforce with a epoxied frame then weld it up after its more secure. You would think they could put jacks (cranes) under it and weld it up and not let china have RF astronomy dominance.I wonder if you can 3d-print a concrete support under it with those new 3d printer machines that make the stupid looking round concrete houses so you can work on it safely. I assume when you drill out all the cracks in the aluminum and make sure the brackets are solid you can resuspend it with stainless cable. If you could figure out how to get a printer to make that temporary support that could be demolished later it might save scientists overall money in the long run by making more weird science stuff repairable. At 900 tons its well outside of helicopter support and it looks like you would need to cut out alot of the structure on the bottom to put a bunch of cranes there. Maybe just put a new receiver up and fix the reflector later? You could probably cut out sections carefully and reuse them so you can drive equipment down there.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: November 20, 2020, 11:38:38 pm
content: Reading several different articles about this, it appears to be another case of "penny wise and pound foolish". Between the instruments and location there is a great deal of good science that could still have been done with Arecibo, and some of it is non-overlapping/complementary with FAST. But maintenance costs were deferred for years and now it is too late. Some of those maintenance costs were deferred in favor of instruments that are now unusable and un-recoverable.

author: coppercone2
author_rank: Super Contributor
timestamp: November 21, 2020, 12:30:35 am
content: lets paint that rust and patch those holes with our good willKeep in mind that is also a multi terrawatt radar, not just a telescope. It could be used to find asteroids that are heading towards earth. Now the CCP will be in charge of that

author: BravoV
author_rank: Super Contributor
timestamp: November 21, 2020, 04:29:33 am
content: Quote from: coppercone2 on November 20, 2020, 10:49:37 pmC'mon ...Here an idea, why not turn the whole metal structures into bulk metal scraps, sell it to the Chinese to feed your fellow poor Puerto Ricans that have been abandoned by the current POTUS.Here, few moreinformationalpropaganda videos to enlighten you ...Btw, she used Fluke DMM, at least something you can be proud of.

author: coppercone2
author_rank: Super Contributor
timestamp: November 21, 2020, 05:01:45 am
content: Quote from: BravoV on November 21, 2020, 04:29:33 amyea if you climb up there you can stabilize the structure with a glue scaffolding before you start grinding it and dressing welds etc. It probobly got messed up when the line tore out and hundreds of tons started to shake. I expect lots of deformation, damaged bolts and some tearing. Not to mention it probobly draws lots of rich smart people with lots of disposable income to a country thats not doing so well. You don't really want (especially high power RF signals radar experts *cough* stealth detection *cough*) those people going to china. That thing did alot more for the world then just generating some data for the duration of its existence. CCP seti is more like search for 'capitalist objects of party interest'.

author: magic
author_rank: Super Contributor
timestamp: November 21, 2020, 07:56:17 am
content: It's the suspended antenna platform which is in danger of falling down if the remaining cable snaps. It weights a few hundred tons and hangs 150m above ground and still tens of meters above surrounding hills, so not that easy to give it additional support. And nobody has the balls to climb it and replace the failed cables. Not sure why they couldn't do it from a helicopter or something - maybe the cables are too heavy to lift from the ground without using the structure itself for support.I wonder how they built it in the first place.

author: coppercone2
author_rank: Super Contributor
timestamp: November 21, 2020, 05:18:06 pm
content: given what they say about the rope slipping out, it sounds like a bad crimp job or bolts not being tightened. The rope should have been tied on the other side, I guess they tried to make it 'neat' and cut the remaining off after it was crimped into place. Then the knot should have wedged into the crimp as a secondary protection method.I guess this is the way to do it, you don't really see knots on suspension bridges either. But those HAVE to be aesthetically pleasing. When I see a project of this magnitude fail by a 'slip' it really makes me wonder. I never liked rope suspensions, the interface between the solid and the rope always seemed suspect.

author: station240
author_rank: Unknown
timestamp: November 21, 2020, 06:04:51 pm
content: Quote from: magic on November 21, 2020, 07:56:17 amThe suspended mass is 900 tons.The main problem is any replacement cables cannot be installed without putting people onto the structure, or in the path of cables should they break.ALL the cables have been found to be weaker than expected.https://edition.cnn.com/2020/11/19/world/arecibo-telescope-decommission-damage-scn-trnd/index.html"After the break on November 6, engineers inspected the rest of the cables and discovered new breaks as well as slippage from some of the sockets on the towers. Multiple engineering companies reviewed the damage. They determined that the telescope could collapse because it is "in danger of catastrophic failure" and the cables are weaker than expected.""While no direct cause for the breaks has been identified, corrosion is suspected as the main issue. The observatory has withstood hurricanes, earthquakes and tropical storms over the years.""Even if engineers could safely fix all the damage and add cables to support the telescope, it would likely have stability issues in the future."

author: David Hess
author_rank: Super Contributor
timestamp: November 21, 2020, 07:56:11 pm
content: A search turns up various articles which discuss funding problems for Arecibo starting back in 2007 and funding being directed toward support programs instead of maintenance.

author: bsfeechannel
author_rank: Super Contributor
timestamp: November 21, 2020, 08:40:58 pm
content: That'll be a helluva skateboard bowl.

author: station240
author_rank: Unknown
timestamp: November 21, 2020, 11:28:40 pm
content: Scott Manley video, about the problems with the dish, and also how it was constructed.

author: bsfeechannel
author_rank: Super Contributor
timestamp: November 26, 2020, 11:47:54 am
content: Hello wonderful person! I knew Dave watches this guy, but now I know this guy watches Dave.My sensors indicate the presence of an upcoming Amphour guest.

author: cdev
author_rank: Super Contributor
timestamp: November 26, 2020, 04:29:23 pm
content: Arecibo seems to me to be kind of a unique location and resource, but maybe the science of radio astronomy can achieve equivalent or higher resolution by using multiple smaller dishes and its more flexible.STILL, I'm always inclined to repair rather than replace. Or, why not replace the entire thing, that sounds like it mightbe cheaper than repairing, especially if they could automate as much as possible of it.This seems like an engineering problem that is likely fixable with a little innovation. An ideal candidate for a contest, "How would you fix or replace the Arecibo Radio Telescope economically" or similar. The winner and their family or a friend can get three free trips to Arecibo, and a party to be held in the winner's honor after the successful repair, as well as the satisfaction of having helped.I would guess that there must be an answer out there, and its probably not as complicated as they are making it out to be.Isn't that the whole essence of science and engineering anyway?

author: Bud
author_rank: Super Contributor
timestamp: November 26, 2020, 05:52:30 pm
content: "It can't be repaired without dangers to the workers". Yes, by modern standards you can't fart when changing the bicycle wheel, as this puts you in danger.We repair truss bridges in much more dangerous conditions, why this little structure can't be repaired .

author: CatalinaWOW
author_rank: Super Contributor
timestamp: November 26, 2020, 05:57:29 pm
content: As one of my mentors used to say "YAGOTTAWANNA"

author: LaserSteve
author_rank: Super Contributor
timestamp: November 27, 2020, 12:48:57 am
content: Maybe sell it to Elon?Steve

author: Nauris
author_rank: Regular Contributor
timestamp: November 27, 2020, 03:34:21 pm
content: Quote from: Bud on November 26, 2020, 05:52:30 pmIf it did not come down on windy day, then I think it safe enought to climp on a calm day. Sounds more like of the ridiculous 'Safety First' corporate bullshit that big corporations are so full of.They could just stabilize it with hundred small cables that are easier to handle than one big. One man with a winch on each end and third one sypplying cable from ground

author: David Hess
author_rank: Super Contributor
timestamp: November 27, 2020, 03:42:03 pm
content: Quote from: Nauris on November 27, 2020, 03:34:21 pmPhotographs show that the remaining cables have already had strands break due to excessive strain. The structure could collapse at any time.QuoteIt would take too much time, and cost too much considering available funds.

author: Ian.M
author_rank: Super Contributor
timestamp: November 27, 2020, 05:54:13 pm
content: Its also a matter of access. You'd need to get heavy lifting equipment in place to relieve the load on the cables. I suspect the nearest >1000 tonne mobile cranes are in the USA or Mexico and even assuming you could get three big enough cranes on the quay in San Juan with enough time to do the work (there's only seven months till the next hurricane season), getting them up the road to the observatory (Highway 625) and emplaced just outside the rim of the dish between the towers, avoiding the danger zone would be a challenge in itself.You'd also need to design a method of grappling or getting slings on the antennae platform that doesn't put the workers at unacceptable risk.

author: Nauris
author_rank: Regular Contributor
timestamp: November 27, 2020, 07:29:46 pm
content: Quote from: David Hess on November 27, 2020, 03:42:03 pmThat must be from corrosion/fatigue or past overload. If there were strands breaking from static load it would already be on the groundQuoteBut why would it collapse at any time? I think it most probably comes down when there is some small extra stress acting on it like a gust of wind. So if it survived a windy day it is unlikely to come down following calm day and that is exactly the moment repair crew should be working on it.QuoteI don't think it takes more than a week or two. Few kilometers of steel rope and a group of brave spanish men in Puerto Rico getting things done cost way less than those worry worry engineers and managers currently overanalyzing it and making straightforward things sound impossible. After all it is still up just needs some cables reinforced.

author: Gyro
author_rank: Super Contributor
timestamp: November 27, 2020, 08:11:31 pm
content: Quote from: Nauris on November 27, 2020, 07:29:46 pmItdoesseem pretty unlikely that, with a static load of 900 tonnes, stretched out at an angle too, the additional weight of a couple of people going out to attach the end of an emergency support cable would trigger a sudden collapse.The crew could maybe be on safety lines from a helicopter too.P.S. Mind you, I'm sitting in an armchair!

author: Ian.M
author_rank: Super Contributor
timestamp: November 27, 2020, 08:29:44 pm
content: Due to the geometry, there's far more than 900 short tons (approx 820 metric tonnes) load on the cables. You can find some details of the geometry here:https://www.naic.edu/~astro/aotms/performance/StructureDynamics.pdfOne of the problems is a cable under tension will whip violently if it breaks, and anyone in the way of a steel one as large as the Arecibo platform uses when it lets go would most likely end up as a chunky bloody splatter, and any helicopter could be swatted out of the sky.Also, if the cables have been weakened enough that there is insufficient remaining redundancy, its no longer possible to slack off one cable at a time and replace it to the same anchor points, so cable replacement becomes vastly more complex, putting more people in the high danger zone for longer.

author: David Hess
author_rank: Super Contributor
timestamp: November 27, 2020, 09:43:20 pm
content: Quote from: Nauris on November 27, 2020, 07:29:46 pmThe strands were broken from the two recent overload events.QuoteIt could collapse because the remaining cables are damaged and in an uncertain condition.QuoteThe physics and engineering are straightforward. The weights are known and the geometry can be measured from a distance to calculate the strains involved. Photographs show that the remaining cables have been stressed beyond their safe limit."Management" is who allowed deterioration of the structure to proceed over the past 13 years of no maintenance.

author: james_s
author_rank: Super Contributor
timestamp: November 27, 2020, 09:50:20 pm
content: People crazier than I have certainly attempted more dangerous stunts than that, even for no more gain than having accomplished the stunt. I would be more willing to climb up onto that platform to attach some cables than to attempt to climb up Mt Everest for example. Personally I would not want to do either one, but replacing the cables to save this thing from collapse seems far more useful.How much does the suspended structure weigh? Is it within the realm of what could be lifted straight up by a large heavy lifting helicopter? If so either lift the thing up, cut the cables and then set it aside on the ground, or lift it to take the load off the cables just long enough for a crew to rush out and attach already prepared replacement cables.

author: Ian.M
author_rank: Super Contributor
timestamp: November 27, 2020, 10:11:33 pm
content: Its two orders of magnitude heavier than any helicopter can handle. I suspect the next thing that will happen is that a demolition plan will be put forward, probably by dynamiting the ground anchors of the tower restraining cables, and the tower bases to trigger an inwards collapse.

author: coppercone2
author_rank: Super Contributor
timestamp: November 27, 2020, 10:11:58 pm
content: 900 tons, you would need like 60 hinds lolyou would probobly need to build a temporary structure under it, I have my doubts even about cranes. thats why i suggested the 3d printed concrete tower

author: rdl
author_rank: Super Contributor
timestamp: November 27, 2020, 10:30:57 pm
content: There's still a lot of infrastructure there and the site is obviously ideal for a telescope of that type, why not just rebuild? Maybe the towers can be reused.

author: TerraHertz
author_rank: Super Contributor
timestamp: November 27, 2020, 11:50:02 pm
content: Quote from: David Hess on November 27, 2020, 09:43:20 pmSorry for lack of a link, but somewhere in the various videos I've watched about this recently there was a short sequence of pictures of the cables, taken by drones.They are a mess. Steel multi-stranded cables, several inches thick, in which there is a lot of internal rusting causing random bulges. The spreading of the strands causes uneven stress on the strands, and together with the corrosion, results in LOTS of broken strands. Many, many places where there are broken strands sticking out like hairs.So when they say the entire structure could collapse at any time and it's too unsafe to work on, they don't mean the extra weight of workers could make it fall. They really mean it could go at any moment. It has no remaining redundancy, and strengths of the remaining cables are continually reducing due to corrosion and ongoing strand breaks.The final failure mode would be completely unpredictable, but will likely involve huge cable whipping around, the antenna falling in some random arc, and the support towers falling over dragged by unbalanced cables. No one is going to go anywhere near it. No helicopters, no building an emergency support tower under the antenna, and even walking around under the dish meshwork is a death sport at the moment.I'd think even controlled demolition by placing cutting charges on all the cables so they can be dropped in one go, would be an extremely dangerous job.

author: coppercone2
author_rank: Super Contributor
timestamp: November 28, 2020, 02:01:10 am
content: drones can put radio charges on the wires, or haul control wires out there, so it falls right in the middle, then you can put a new transmitter on it. you could use the control system of a TOW missile connected to a drone (it is long and safe and light with a cable length of 4km). you can make them like horse shoes that are placed over the wires, and you can put two of them on each end and sequence it so the wire falls down strait rather then being cut and then dragging through the reflectors on the bottom, to minimize damage. or use helicopters to hold the wires after they are cut to bring them off to the side without damaging the reflectors on the bottom. attaching the wire to a helicopter might be dangerous because you don't know how much strain it will get rid of and how it will shake when its cut, it would need alot of slack and a protection to release itself if it tried to yank on the helicopter. the less you screw up the bottom the more economical it would be to rebuild the top part.

author: james_s
author_rank: Super Contributor
timestamp: November 28, 2020, 02:28:49 am
content: I don't understand how it got THAT bad without anyone noticing that failure was imminent. Rust of cables like that doesn't happen overnight. At least it isn't just in my country that so many people defer maintenance until it becomes a huge expensive problem. I know multiple people who kept putting off having the timing belt on their car engine changed until it snapped and destroyed the engine. People do the same thing with oil changes.

author: Ian.M
author_rank: Super Contributor
timestamp: November 28, 2020, 03:45:30 am
content: The dish reflector would be totally FUBARed if you dropped the platform onto its center. Its held up by radial suspension cables under it from the rim, and they'd all whiplash. Even if the individual panels remained attached, didn't buckle and you could splice the dish suspension cables, after nearly 60 years most of the panel adjustments would be seized, so you'd never get it back in shape.The best option with any chance of saving most of the installation would probably be a giant airbag with enough helium bladders to make it near neutrally buoyant, winched into place under the platform, and lots of smaller airbags under the middle of the dish emplaced by ROVs and inflated till the radial cables were slack enough not to whiplash.Emplacing the cutting charges on the platform cables would be challenging using aerial ROVs, but if you have that capability, attaching support lines to the main cables sufficient to stop them falling on the dish would also be possible.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: November 28, 2020, 04:03:10 am
content: If we really like the idea of Arecibo we should start surveying where we want to put its replacement, and designing what it should look like. The existing site might be the answer, in which case figuring out how best to demolish/salvage the existing structure to make way for the future makes sense. Otherwise it becomes just another one of those pitch experiments where it might be days or decades before the final failure occurs.

author: coppercone2
author_rank: Super Contributor
timestamp: November 28, 2020, 04:14:07 am
content: hanging something on it like a chirstmas ornament is much easier then trying to grip cables in any way to support 900 tons even if distributedcan you totally blow that thing to smithereens so it does not destroy the stuff it lands on (really really big boom)? if you can turn it into pop corn. practice for asteroidsyou can evacuate the surrounding area and try to blow it up so it goes outwards like a fountain and away from the crater.this comes to mind, but I am not sure how well it will work on aluminum, but I think if its all bolted together its possible to set it up so it does (I think that is a bangalor pipe filled with explosives). Put a bunch of sticks like that in the shape of a 3d * and it might work? That thing got vaporized. You would need to use shattering explosives (military) not common nice demolition explosives. You could build a replica to test it first on a tower to make sure it is sufficiently disintegrated.

author: magic
author_rank: Super Contributor
timestamp: November 28, 2020, 08:31:14 am
content: Quote from: james_s on November 28, 2020, 02:28:49 amIt's called fall of civilization and poverty.But when I say it they don't listen because they have the latest generation iShiny to distract themselves withOh, and big dreams. Never forget big dreams

author: CJay
author_rank: Super Contributor
timestamp: November 28, 2020, 10:36:16 am
content: Quote from: TerraHertz on November 27, 2020, 11:50:02 pmI think maybe you've answered the question of how to place demolition charges, I wonder if it would be possible to have drones place shaped charges, one packaged so it 'falls' into correct alignment to cut the cable...

author: CatalinaWOW
author_rank: Super Contributor
timestamp: November 28, 2020, 04:39:05 pm
content: Quote from: james_s on November 28, 2020, 02:28:49 amYeah, but this was our country. Puerto Rico isn't a state, but for all practical purposes it is part of the US. And the folk who provide funding and deferred maintenance were virtually all in the mainland.This died because it was less important to us than the military, the ISS, school lunches student loans and a myriad of other things, many of which no one really cares about.

author: james_s
author_rank: Super Contributor
timestamp: November 28, 2020, 06:55:40 pm
content: Oh I missed that it's Puerto Rico, for some reason I was thinking it was somewhere in South America. Figures. So typically American to neglect modest repairs until it turns into a huge expensive writeoff.

author: David Hess
author_rank: Super Contributor
timestamp: November 29, 2020, 09:27:31 pm
content: Quote from: james_s on November 28, 2020, 02:28:49 amMaintenance was limited (halted?) by budget reductions after 2007 if not sooner.

author: Ian.M
author_rank: Super Contributor
timestamp: November 29, 2020, 09:37:58 pm
content: All for want of a small team of high rope access trained riggers tasked to permanent maintenance, a magnetic wire rope tester and a few barrels of anhydrous lanolin per annum!The average wage in Puerto Rico is about 20K USD per annum and there's historically in excess of 10% unemployment, so I bet the cables could have been kept greased (against rust) and inspected for appox. 100K USD per annum budget. If you cant raise >$20 per hour above base access costs from selling access time on one of the largest radio telescope dishes in the world to fund routine maintenance, then your management team is criminally incompetent.

author: coppercone2
author_rank: Super Contributor
timestamp: November 29, 2020, 11:21:09 pm
content: management: what do we need that thing again for? (asks same question every year)

author: nfmax
author_rank: Super Contributor
timestamp: December 01, 2020, 04:10:15 pm
content: ...and it's gone:https://www.theguardian.com/world/2020/dec/01/arecibo-radio-telescope-collapses-puerto-rico

author: MadTux
author_rank: Frequent Contributor
timestamp: December 01, 2020, 04:37:10 pm
content: Sad

author: CatalinaWOW
author_rank: Super Contributor
timestamp: December 01, 2020, 04:37:35 pm
content: That certainly validates the risk assessment. Too bad they didn't use those same skills when allocating maintenance funds.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: December 01, 2020, 05:02:42 pm
content: Aw crap.

author: CJay
author_rank: Super Contributor
timestamp: December 01, 2020, 05:08:12 pm
content: Awhh hell.Now, do we clean it all up or leave it for a few dozen generations later to re-discover

author: coppercone2
author_rank: Super Contributor
timestamp: December 01, 2020, 05:13:54 pm
content: drones were the only way it looks like this job could have been approached

author: David Hess
author_rank: Super Contributor
timestamp: December 01, 2020, 05:14:53 pm
content: Quote from: Nauris on November 27, 2020, 07:29:46 pmhttps://www.sciencemag.org/news/2020/12/arecibo-telescope-collapses-ending-57-year-run

author: LaserSteve
author_rank: Super Contributor
timestamp: December 01, 2020, 05:39:06 pm
content: Aw Crap Squared...Rebuild It!How many other of our great infrastructure facilities are now ticking away at failure?Steve

author: CatalinaWOW
author_rank: Super Contributor
timestamp: December 01, 2020, 06:45:23 pm
content: Now the questions are:1. Is it too risky to go in and try to salvage any of the equipment?2. Is there any way to stop locals from wildcatting this salvage?

author: schmitt trigger
author_rank: Super Contributor
timestamp: December 01, 2020, 07:32:01 pm
content: Like some other poster mentioned, if the government had allocated only 0.1% of what has been spent on the Middle East wars, not only this would not have happened, additional facilities would have been built.

author: SeanB
author_rank: Super Contributor
timestamp: December 01, 2020, 07:33:06 pm
content: Quote from: CatalinaWOW on December 01, 2020, 06:45:23 pmWhatever was on the observing platform is now splashed all over, and not really salvageable, as it is likely all buckled from the impact, with only small parts likely to have survived. The rest is just scrap steel, so really heavy to move away, and thus not much will go missing.

author: coppercone2
author_rank: Super Contributor
timestamp: December 01, 2020, 07:41:26 pm
content: lol give them the severance package the economy over there just got screwed

author: TerraHertz
author_rank: Super Contributor
timestamp: December 02, 2020, 12:10:36 am
content: Grab some google maps 'as it was' aerial views before they get updated.https://goo.gl/maps/RdVBXcomEEUDHiYd8Before and after views by a local (700K):

author: David Hess
author_rank: Super Contributor
timestamp: December 02, 2020, 03:21:04 am
content: I was chatting with someone on IRC and they said that someone at Arecibo Tweeted that since the initial damage, they could hear strands of the cables breaking every few minutes.

author: aseok
author_rank: Contributor
timestamp: December 02, 2020, 01:15:34 pm
content: observatory collapsed on dish.

author: jogri
author_rank: Frequent Contributor
timestamp: December 02, 2020, 02:02:24 pm
content: Quote from: LaserSteve on December 01, 2020, 05:39:06 pmWell, if you want to rebuild it you'd probably have to disassemble almost the entire dish and remove the towers with their foundations... The gregorian dome was assembled where the dish is now and then winched up, so you can't even save the remainder of the dish as you need the space to assemble the dome.And call me a pessimist if you must, but imo almost all infrastructure suffers from a lack of maintenance: The budget is either too small from the beginning or the costs explode, so you have to "save money" somewhere-> you cut back on maintenance as it doesn't mean directly firing people (bad PR). And then you just give yourself a pat on the back for being a genius and blame others for not giving you money if it fails (hopefully when you are long gone and another sucker has your job).I wouldn't be surprised if such occurences become the norm in a few years, quite a lot of the stuff that was build in the 60s and 70s is already starting to fail... Here in germany, nearly 15% of all highway bridges are classified as "dilapidated". And that is certainly not going to get better anytime soon.

author: edy
author_rank: Super Contributor
timestamp: December 02, 2020, 05:14:26 pm
content: The death star suffered the same fate.... but not from lack of maintenance.

author: tom66
author_rank: Super Contributor
timestamp: December 02, 2020, 05:46:27 pm
content: RIP. Looks like they were right to not attempt to repair it, it was truly well past safe limits.Rebuilding is surely the only option now but what is the likelihood of that?

author: schmitt trigger
author_rank: Super Contributor
timestamp: December 02, 2020, 07:56:16 pm
content: One of the side effects of the Cold War was that “big science” projects, if they even provided the remotest opportunity of enhancing “the National Security”, whatever that meant, would be funded. Large scale funding, no buts or ifs.Neither the USA nor Russia have the political will to commit to such projects nowadays. In this instance the baton is solidly in China’s hands.

author: Ian.M
author_rank: Super Contributor
timestamp: December 02, 2020, 08:40:23 pm
content: Its worth looking athttps://history.nasa.gov/SP-4218/ch4.htmwhich covers the earlier history of the Arecibo dish.The only comparable dish for long range deep space radar is in southern China:https://en.wikipedia.org/wiki/Five-hundred-meter_Aperture_Spherical_TelescopeIts only been online since 2017 and wasn't fully operational till the beginning of this year. We are lucky not to have had a critical gap in Earth's planetary radar capabilty.Can the Western world really afford to leave accurate orbit characterization of Earth crossing asteroid threats to the Chinese? There aren't that many near equatorial suitable sites in countries that are firmly under Western world control, so IMHO rebuilding at Arecebo is well worth considering - its already got most of the ancillary infrastructure required and a prepared depression that just needs the scrap cleared out.The dish was originally wire mesh (literally chicken wire) and was upgraded to aluminum panels in the early '70s to extend its capability to S band operation. A wire mesh dish (or partially wire mesh with a high quality aluminum reflector in the center, elongated on its north-south axis) might be a cheap way of getting reasonable capability back into operation on the site. Its possible that significant areas of the reflector panels could be salvaged safely for reuse.The Arecibo feed platform needed to be as massive as it was because it was built with 1960's technology. Modern composites would permit a much lighter structure, and modern electronics would permit a significantly smaller structure, so it could reasonably be lowered onto composite pylons protruding through the reflector to 'dock' it for maintenance and to withstand hurricanes. Initially it could be lofted by a commercially available tower crane with its base located in the eastern or western quadrants of the reflector. As funds allow, it could be upgraded to a suspension system similar to the previous one, but built with corrosion resistant materials.

author: David Hess
author_rank: Super Contributor
timestamp: December 02, 2020, 10:07:06 pm
content: Quote from: Ian.M on December 02, 2020, 08:40:23 pmThe Chinese dish lacks radar capability. The article you linked even says so and I have heard the same from other sources:Fifth, Arecibo's larger secondary platform also housed several transmitters, making it one of only two instruments in the world capable of radar astronomy.

author: Ian.M
author_rank: Super Contributor
timestamp: December 02, 2020, 10:16:24 pm
content: Thanks, David.For effective radar, it isn't essential to transmit from the same antenna - one can use a phased array of much smaller remote dishes to form the transmit beam. The downside is more wasted power and bigger side-lobes. OTOH you *DO* need real dish surface area to improve the signal to noise ratio of the radar receiver.Whether or not that capability could easily and quickly be added to FAST would depend on what high bandwidth comms links they have to sync large steerable transmit capable dishes in the region. Before Arecibo's failure there wasn't a great incentive to do so.However I really shouldn't complain about your correction as it makes the case for an improved Arecibo rebuild with a fully movable feed platform (at least on a North/South axis) even stronger.

author: David Hess
author_rank: Super Contributor
timestamp: December 02, 2020, 10:49:14 pm
content: Quote from: Ian.M on December 02, 2020, 10:16:24 pmYou could have just said "bistatic radar".https://en.wikipedia.org/wiki/Bistatic_radarQuoteThe antenna aperture is just as important on transmit as receive. If they had suitable transmitting dishes with enough aperture, then they would not need the larger dish. I suspect in the case of radar it is more cost effective to use a larger dish with one large transmitter than to replicate the transmitters for many separate dishes.QuoteOr China will add that capability to their dish, although I get the feeling after reading various discussions that that will not be easy because it was not designed for it.

author: jmelson
author_rank: Super Contributor
timestamp: December 03, 2020, 02:18:10 am
content: Quote from: jogri on December 02, 2020, 02:02:24 pmIt has actually been going on for quite some time. I work in the basic nuclear science area. When I got started, there were ion accelerators all over the place. Now, a whole bunch of them have been shut down, or available only to commercial customers, etc. So, the old cyclotron at Oak Ridge national lab was shut down, then the Van de Graff there was shut down (highest voltage Van de Graff in the world, 50 MV), the 88" cyclotron at Lawrence Berkeley Labs was made only available to cash customers, right now the superconducting cyclotrons at MSU are being shut down and scrapped. A bunch of other facilities have also been shut down. All due to a VASTLY shrinking science budget in the US.Jon

author: 0culus
author_rank: Super Contributor
timestamp: December 03, 2020, 03:08:58 am
content: Quote from: BravoV on November 20, 2020, 03:38:22 pmThe thing is Arecibo was also a radar....FAST to my knowledge is a receiver only.

author: BravoV
author_rank: Super Contributor
timestamp: December 03, 2020, 03:10:27 am
content: Quote from: jmelson on December 03, 2020, 02:18:10 amThe Chinese FAST dish cost US$171 millions (excl.data processing center) (->Reference), for US, say mark it up 3 times as more expensive labour, more advanced design and technology, and prolly corruption too, say at a half billion US$, this figure still like a drop of water in the lake compared to military budget.

author: BravoV
author_rank: Super Contributor
timestamp: December 03, 2020, 03:33:05 am
content: Can this FAST morpheable dish have advantage if used for radar ?

author: BravoV
author_rank: Super Contributor
timestamp: December 03, 2020, 03:59:28 am
content: Quote from: 0culus on December 03, 2020, 03:08:58 amJust guessing, when in design stage, someone there or an entity (military maybe ?) should have thought of this ?

author: 0culus
author_rank: Super Contributor
timestamp: December 03, 2020, 04:01:21 am
content: Not sure what you're getting at, but Arecibo definitely had military applications in it's early life.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: December 03, 2020, 04:16:44 am
content: Quote from: jmelson on December 03, 2020, 02:18:10 amWhile I am generally in favor of research spending, and do think there is still good science to be done at a facility like Arecibo was, and could be again, not all facilities need to continue. While I am sure there are uses for them today, Van de Graff generators and cyclotrons are the doddering old grandparents of the high energy particle accelerators at CERN. While we can be fond of them it is somewhat like railing against the decommissioning of an old 400 kHz oscilloscope or a seventy five pound signal generator that can hit 950 MHz on a good day.

author: msuffidy
author_rank: Frequent Contributor
timestamp: December 03, 2020, 04:38:04 am
content: Well they saved some money on the demo. At least it ripped out ALL the cables somehow and no buildings were destroyed. If they are really interested they could just rebuild something like it there as it is an escavated site with maybe reusable towers.

author: LaserSteve
author_rank: Super Contributor
timestamp: December 03, 2020, 04:51:04 am
content: What we just lost was the high power transmit waveguide, two independent transmit feeds, a variable power splitter and part of theDish. As well as the astronomy feed horns. The 430 Mhz transmitter is in the building on the hill.While Arecibo had seven receive feeds, it was also a dual beam radar, both the Gregorian and the linear array could be used at the same time if desired.Arecibo had six auxiliary feedhorns for 430 Mhz receive, More often the VLA / Deep Space networks / other telescopes were used as multiple parallel receive sites , giving the asteroid network the benefits of a phased array and synthetic aperture. Goldstone has an eight gigahertz transmitter, but is not as available as Arecibo was.So not only could it transmit, it was a seven pixel imager by itself.Contrary to popular belief, it could also scan in a limited manor by moving the feeds. and the cables had active tensioning.In other words, the site was more capable then one might think.

author: coppercone2
author_rank: Super Contributor
timestamp: December 03, 2020, 07:17:13 am
content: Quote from: jogri on December 02, 2020, 02:02:24 pmit no longer needs to move NATO around in a emergency. Friendly oil relations with russia are sure to prevent an invasion now (probobly part of the reason)I kinda wonder what the hell will happen if there is WW3 in say 30 years when all the stuff is really falling apart. Whoever has more amphibious vehicles and mobile bridges wins? minor blitzkrieg repeat with whoever has more light vehicles? (if you don't know, nazi tanks only started getting beefy into the middle of the war). You used to be able to discourage that because you could put alot of nasty equipment into the right places at a quick notice. Not sure if they will be able to give the same kind of value to stuff made with the air mobility craze in the modern military (so we can send stuff to the desert). I think it all assumes that no one is going to figure out how to make something heavy scary again (new armor). There does seem to be a sizable amount of people that suggest tanks are not going to be super bypassed by modern equipment as much as we think, so politicians could be making the wrong call based on bad information when it comes to maintaining those sorts of things (from the sounds of it though, it will bring upon a gigantic argument).

author: BravoV
author_rank: Super Contributor
timestamp: December 03, 2020, 08:27:53 am
content: Quote from: coppercone2 on December 03, 2020, 07:17:13 amI thought we're discussing radio astronomy antenna here ?Pity you, so much paranoia and hatred, must be like hell living with that kinda thought.

author: magic
author_rank: Super Contributor
timestamp: December 03, 2020, 09:07:14 am
content: Offtopic being one thing, what's "hateful" about wandering how to fight WW3 on collapsing highways?

author: coppercone2
author_rank: Super Contributor
timestamp: December 03, 2020, 04:00:19 pm
content: most old big projects that engineers find cool are basically falling apart because they are said to not benefit the military anymore and most people are super cheap and military applications usually do not allow you to boil a design down to shady levels, so now that the military is left out of things and deemed not important the projects start to suck and maintenance is not had. At least, its a small part of the reason why. In America like 30-40% of the bridges are fucked up (and I shudder to think what the number would be if German engineers that live in Germany and are culturally German would rate the % at given by the quality difference of 'entry grade' German and American products!). Really thrilled to drive to certain places where you can become jam in a cement sandwich because someone does not wanna paint some stuff and replace some bolts. I feel like the people that ignore this and still drive under it every day are some really driven psychopaths (super common for people to show solidarity to people neglecting infrastructure for some reason to show that you are brave and badass. I mention it in the car driving near a suspicious object and you might as well put a fucking barbell in the car and have someone do a 500 pound lift and start gloating about it).of course its hateful, bridge collapses kill people, like the one in Italy recently. Possibly a similar principle to this telescope, ignore corrosion in load bearing members. Granted the ones in bridges are pretty insidious, I had a granite countertop crack because a metal bar potted in epoxy some how put rust pressure on the granite. You would really need to trust corrosion engineering best practices and forgo your own intuition (as you should) to see that one coming because based on 'common sense' it should not have happened, but if you read about what happens with epoxy and iron, its plainly shown as a regular occurance.these projects are really interesting if you find 'damn he really squeezed everything he could have out of the companies preferred FEA method! look how he fooled everyone into not making a real life experiment first' interesting and or cool.BTW I noticed in Poland when I was driving around too many things had a nice heavy coat of rust and dilapidated failing paint on it. All the rusty property fences looked wonderful. Old historical towns with a middle aged feel still had the same rusty moss covered roofs, its like if you plated the renaissance with cheap communism. Beautiful victorianish house with a black mold, weathered paint and rust covered soviet grain house roof right near the town hall that looks like its from a fairy tale.

author: jmelson
author_rank: Super Contributor
timestamp: December 03, 2020, 04:46:15 pm
content: Quote from: CatalinaWOW on December 03, 2020, 04:16:44 amSome Van de Graff accelerators are certainly old-school and pretty obsolete. But, the HHIRF at Oak Ridge was a 50 MV folded Van de Graff, and very sophisticated and about twice the energy of anything else ever built.Cyclotrons are also old school, but the superconducting cyclotrons at MSU NSCL were very advanced, and I think their larger one (K1200) was the highest energy of any single cycloton in the world. They were still doing research with them until this month.MSU is replacing their cyclotrons with a linear accelerator system, but it won't be fully online for a couple years.Jon

author: coppercone2
author_rank: Super Contributor
timestamp: December 03, 2020, 05:01:23 pm
content: those last alot better because its usually in a sealed container of inert gas, at least the vandergaff in the MV range.

author: MadTux
author_rank: Frequent Contributor
timestamp: December 03, 2020, 05:29:49 pm
content: Video on how it collapsed:https://vid.pr0gramm.com/2020/12/03/36fa6ec3c3b41f57.mp4

author: coppercone2
author_rank: Super Contributor
timestamp: December 03, 2020, 06:12:07 pm
content: well that sure is a embarrassing fail, I am not sure you want to let your projects end like that. It really should have been demolished I think. Literary infrastructure that crumbled to pieces on its own. The way it swings to the side like a wrecking ball is so bad.

author: MadTux
author_rank: Frequent Contributor
timestamp: December 03, 2020, 07:06:42 pm
content: Wire snaps:https://vid.pr0gramm.com/2020/12/03/2ceeb5f0ae90833b.mp4

author: tom66
author_rank: Super Contributor
timestamp: December 03, 2020, 09:17:49 pm
content: That drone was lucky to not get taken down by that snapping cable.Really interesting to see an up close of a structural failure like this. The cable gives a bit and then total failure and it's all over.

author: Sal Ammoniac
author_rank: Super Contributor
timestamp: December 04, 2020, 02:19:36 am
content: More video of the collapse:http://players.brightcove.net/679256133001/EkLWnGuil_default/index.html?videoId=6213883083001

author: LaserSteve
author_rank: Super Contributor
timestamp: December 04, 2020, 05:10:29 am
content: If you love RF, this may make you cry.. Tech details toward the end.https://youtu.be/IqGnnpwEwugSteve

author: Bud
author_rank: Super Contributor
timestamp: December 04, 2020, 07:48:23 am
content: The aliens must be scratching their heads (or whatever ) why that transmission was suddenly lost.

author: Ian.M
author_rank: Super Contributor
timestamp: December 04, 2020, 09:16:34 am
content: Its deeply suspicious that the main suspension cables were painted white near their anchors to the platform. Some dumb administrator must have decided to paint the ugly cables which would have been showing signs of surface rust, and once the paint was on them failure was inevitable.Back when Arecibo was built, there were still plenty of 'greybeards' in the rigging industry who'd served their apprenticeship working on the rigging of large square rig sailing ships, and the maintenance requirements for 'plough steel' static rigging in hostile environments were well known. However as stainless steel ropes and cables have displaced plough steel ones for most static rigging, this common knowledge has largely been lost.Its well known that wire rope in dynamic applications requires lubrication. Its far less well known that contrary to the best practices for stainless wire rigging, its *ESSENTIAL* to lubricate 'plough steel' wire static ropes and cables, preferably with a penetrating lubricant with anti-corrosion properties, to reduce corrosion and prevent the strands fretting against each other as the load varies and the cable stretches. The paint coating will have trapped water in the core of the cable, and prevented any applied lubricant from penetrating, resulting in rapidly accelerating corrosion of the strands.

author: tom66
author_rank: Super Contributor
timestamp: December 04, 2020, 09:30:42 am
content: Wasn't this a similar issue with the Ponte Morandi collapse? The cables were encased in concrete because they were 'ugly' which precluded any inspection of them. The concrete traps moisture and has a corrosive effect itself.

author: Ian.M
author_rank: Super Contributor
timestamp: December 04, 2020, 10:09:12 am
content: Each cable should have been replaced as soon as there was significant distortion or more than three broken strands in a short length or two at the terminals.https://www.unionrope.com/Portals/0/Documents/Technical/Crane/when-to-replace.pdfIts obviously been running with little safety margin for many years and in recent years, allowing personnel access to the platform or under the dish, other than for essential structural maintenance, was criminally negligent.

author: BravoV
author_rank: Super Contributor
timestamp: December 04, 2020, 11:35:14 am
content: Quote from: Ian.M on December 04, 2020, 09:16:34 amYep, just for the look, ... or .. maybe hiding the rust.

author: David Hess
author_rank: Super Contributor
timestamp: December 04, 2020, 12:02:43 pm
content: Maintenance is a rubber band which can be indefinitely stretched a small bit at a time by management and politics.Why exactly did Physicist Robert Kerr resign as director back in 2015? The articles I have read imply that after maintenance was deferred, the real condition of the structure was ignored or covered up.

author: David Hess
author_rank: Super Contributor
timestamp: December 04, 2020, 12:04:58 pm
content: Quote from: BravoV on December 04, 2020, 11:35:14 amThe other photographs I saw looked like the cables had been painted with aluminum or zinc paint however they had broken strands sticking out.

author: BravoV
author_rank: Super Contributor
timestamp: December 04, 2020, 12:18:58 pm
content: I guess, the last time they had the money to paint it, to be more "re-presentable" for big screen audiences, was from the James Bond film producer.

author: BravoV
author_rank: Super Contributor
timestamp: December 04, 2020, 12:54:04 pm
content: Quote from: David Hess on December 04, 2020, 12:02:43 pmProblem is, thing like these (and as many others) need much-much more longer time (decades ?) for the commitment and support, far more than just 4 or 8 years of elected governmental administration, which we all see & experience, that sometimes can turn up side down 180 degrees in just 4 years.

author: MadTux
author_rank: Frequent Contributor
timestamp: December 04, 2020, 01:30:49 pm
content: Quote from: BravoV on December 04, 2020, 11:35:14 amPainting cables is a dumb idea, whether it's rust or fretting. With paint, lube can't go in there and the cables can't move along each other. So they will rub against each other which causes fretting. Fretted surface likely starts corrosion and cracks so wire snaps. If the wire strands are locked in place, they also can't move along each other to share load, so some wires get higher stresses than others, until they yield and eventually break. With nough broken single wires, the whole cable snaps.

author: Marco
author_rank: Super Contributor
timestamp: December 04, 2020, 03:21:25 pm
content: Couldn't you build a radio telescope in the same way as a heliostat concentrating solar power plant? An a simple planar array of reflectors, but all concentrating on a single receiver.

author: BravoV
author_rank: Super Contributor
timestamp: December 04, 2020, 03:47:56 pm
content: Quote from: MadTux on December 04, 2020, 01:30:49 pm+1

author: fourfathom
author_rank: Super Contributor
timestamp: December 04, 2020, 03:51:40 pm
content: Quote from: Marco on December 04, 2020, 03:21:25 pmAll the reflections need to arrive at the detector in phase, which would not be the case with a planar array. If each reflector has it's own detector (as is the case with multi-dish arrays), then phases of the individual detected signals can be adjusted electronically to focus and steer the antenna beam pattern.Heliostat's don't much care about phase-coherence.

author: coppercone2
author_rank: Super Contributor
timestamp: December 04, 2020, 07:51:47 pm
content: cables are made by drawing them through this thick grease stuff. Its inside the cable, that won't paint well at all. I know in a garage door you should use cable lubricant once in a while, so the strands do not rub on each other and tear each other up, as a maintenance procedure (sold as chain and cable lube). I am guessing that it is meant to be formulated as not to draw the grease that is inside the cable from the manufacturer out.I don't know what you are supposed to do for giant cables. Probably replace them once in a while.

author: Marco
author_rank: Super Contributor
timestamp: December 04, 2020, 11:02:02 pm
content: Quote from: fourfathom on December 04, 2020, 03:51:40 pmOops, of course. Hmm, you could have a couple intermediate reflectors to add a bit of selectable phase delayGetting a bit too complex I guess.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: December 05, 2020, 12:20:26 am
content: The lead architect of Arecibo, Dr. William Gordon was one of department professors at University. If this is to be rebuilt there will have to be a similar champion who defines the benefits, outlines the plan and chases the funding. The Arecibo telescope was actually a cost saving approach to achieving the science goals. (Initially probing the properties of the atmosphere. Which had military application though it isn't clear to me that that was Dr. Gordon's interest.)

author: RoGeorge
author_rank: Super Contributor
timestamp: December 05, 2020, 09:36:56 am
content: I think a rebuild is out of the question.If there wasn't enough interest (or enough money) to maintain the former telescope, why (or how to) build a new one?

author: Kleinstein
author_rank: Super Contributor
timestamp: December 05, 2020, 10:22:28 am
content: The unique feature the old arecibo installation offered was the radar capability to measure the orbit of asteroids. It is not just the receive part but also the send part. It would absolutely make sense to get back that capability to a similar range. Not sure the arecibo location is the best choice (e.g. chance of earth quakes and hurricanes, high humidity), but it still has some benefits, like much of the infrastructure and ground work already there.The money argument is somewhat valid. The costs for a rebuild would not be that high compared to other large science projects or space missions. Chances are maintenance would be cheaper, at least for the first few years after a rebuild. It would anyway take some time for new plans - chances are the new one would not be identical.There may be alternatives, like adding radar capability to one of the arrays made from multiple smaller dishes.

author: CJay
author_rank: Super Contributor
timestamp: December 05, 2020, 05:04:40 pm
content: Quote from: RoGeorge on December 05, 2020, 09:36:56 amI think that's about the reality of it, if there wasn't money to maintain it then there won't be any money for a rebuild unless it proves to be of military significance.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: December 05, 2020, 07:09:37 pm
content: That is why a champion is required. Someone who can beat the halls of power looking for money. Who can define why it is important for each of the money sources. Someone with the imagination to sell naming rights. Someone who can articulate the economic benefits to Puerto Rico. The scientific bragging right benefits to various patriotic organizations. The educational benefits of tying this in to STEM education. The ecological benefits of a protected zone under and around the antenna. Someone who doesn't recoil at military money if there is some benefit in that direction. Someone who doesn't want to mail an anonymous grant request and hope that money flows back.If there aren't sufficient reasons to rebuild it shouldn't be. It would be a shame if the reasons are there, but it isn't rebuilt because no one can be found who can articulate and champion the cause. Replacement is a bigger job than maintenance, but I suspect the maintenance failed because there was no such champion. Champions for maintenance are hard to come by, few find it stimulating. But even someone willing to highlight what in retrospect is known would have probably done the trick. I suspect stories about how you could hear strands snapping long before the failures occurred would have been vivid enough to spring maintenance dollars free, particularly if they had been combined with drone pictures and audio recordings.

author: CJay
author_rank: Super Contributor
timestamp: December 05, 2020, 08:52:09 pm
content: Quote from: CatalinaWOW on December 05, 2020, 07:09:37 pmI wonder now the Chinese and Japanese have both launched and run highly complex and successful space missions if there might be an impetus for the US to 'compete' and thus a case to be made from that?

author: coppercone2
author_rank: Super Contributor
timestamp: December 05, 2020, 10:20:55 pm
content: its probobly related to stealth technology developments, hardware like this and world class researchers going there will bolster RF stealth and detection stuff most likely. Maybe its been milked to completion by the military and all they can hope to do is play catch up when the cutting edge game is being played on another field.They keep pounding that USA#1 stealth all the time. You probobly need better hardware now to get any benefits for the MIC with the research that has been accumulated, and you can't exactly fly planes in front of it or test it on satellites if its being used by civilians because then someone would know exactly what you are doing. All you can do is prevent mingling between top minds, but the internet makes access control kind of a moot point since this thing was made in the 60's with different communications methods.I think the #1 utility is it being used for asteroids, say a not so friendly country not mentioning some asteroid that is likely to hit some hemisphere that they don't really like as promptly as possible. Or just being able to verify information to make sure someones projections are correct. It had a interesting fact checking capability. To test planes? with it you would need to turn the place into another area 51. The last thing you need is good relations to let scientists in to study a meteor heading towards earth.. each country should have its own.And its a utterly horrible place to test stealth things because its right next to the water, making it easy for a submarine or ship to spy on the sky there. And the 'black security forces' look like the villians in any james bond movie with ships if they were to be at sea.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: December 05, 2020, 10:33:10 pm
content: Clearly since the funding sources mentioned here run from the military on through the military this thread isn't the source of the imagination to get it rebuilt. Though maybe it shouldn't be. In a few years we can hire the Starship to loft a 3 km mylar balloon, aluminized on one side that would be the reflector for a fully steerable dish.

author: coppercone2
author_rank: Super Contributor
timestamp: December 05, 2020, 11:15:28 pm
content: I have a feeling that a giant mylar balloon will be less reliable then this telescope for some reasonfilled with h2 for budgetary reasons?That is going to end up looking like that scene from the movie 'red planet' where the fungus catches on fireWhat I think now is that you can get some high quality roofing out of all those panels. If you make jigs and stuff you can probobly remake like 1/2 of the bottom structure with panel beating, sanding and welding using medium low skill labor. Worlds largest body shop effort. Where are the Eastwood automotive and Miller metal working company sponsorships? Maybe they can put a lincoln electric logo on it like a race car if they supply some tools and materials. Seen from orbital telescopes and planes

author: CatalinaWOW
author_rank: Super Contributor
timestamp: December 06, 2020, 04:05:16 am
content: Quote from: coppercone2 on December 05, 2020, 11:15:28 pmFill it with H2. H2 + vacuum => bad vacuum but no combustion.You would use the Starship to launch your balloon into a beyond synchronous orbit for several reasons. Avoid occluding communications satellites in synchronous orbit. Avoid atmospheric drag and debris problems in lower orbits. And by keeping the subtense low you minimize impact on earthbound observations.Small thrusters, or possibly large gyros rotate the thing around so it can point anywhere, something Arecibo couldn't do and the Chinese one can't either. You could use perhaps 2/3 of the aperture without too much spherical aberration.But on your point an army of metal beaters can build ground based alumimum mirrors for RF. Even higher frequency stuff if you give them the time and tools to do the job. But even third world wages add up. And the logistics of allocating panel shapes and interfaces to thousands of small shops would be an interesting problem. But the idea has merit because it is a hook to get funding from large NGO aide organizations. Wages, plus skills development, plus infrastructure development are all good carrots.There are very few ideas crazy enough to throw out. The only question is which ones will develop the army to implement. Look back at cell phones. Think about the initial pitch. "We want to make a radio network that requires transmitters and receivers with 12 km spacing over the entire inhabited world. And build millions of the most complex radios that anyone can imagine. Why? So teenage girls can gab with their friends endlessly and lonely people can post pictures of cats." Sounds pretty crazy doesn't it.

author: coppercone2
author_rank: Super Contributor
timestamp: December 06, 2020, 05:11:16 am
content: they almost destroyed space though with things like project west fordi mean they can literary destroy space. Someone thought that all the people talking makes propaganda and demonizing harder so they are less likely to eradicate a country because of some memos.PR could develop the 'iron triangle' for weird manually made reflectors and such, they have good access to water for shipping too.https://en.wikipedia.org/wiki/Willets_Point,_QueensThey used to do it for 1/15th the money insurance gave you to do a simple job. Maybe it would work because those RF projects are all heavily bureaucratized so they can deal with a massive delay. Takes about a week for someone to scratch their ass.Probably better for them to develop trade skills and work for goverment money then to have that aluminum come back to haunt us in fake car hoods. mm 10$ car hood made with NASA parts and alumiweld rods. Given what I see going on with car tire markets (i.e. phillipines) its probobly gonna be turned into car parts.

author: BravoV
author_rank: Super Contributor
timestamp: December 06, 2020, 08:04:48 am
content: Quote from: CJay on December 05, 2020, 05:04:40 pmEven there is a money and interest, whats the point ? The whole Puerto Rico island was destroyed by hurricane Maria 3 years ago is still abandoned by mainland federal government with no help what so ever, the basic and major infrastructure still heavily damaged, the money better use to help these poor people 1st, and a telescope has much lower priority.Unless those Puerto Ricans are 2nd grade US citizen. Just read this carefully ->ReferenceIts like watching a poor African countries that is still struggling on basic need, but want to build rocket to send their astronaut to the moon.

author: Kleinstein
author_rank: Super Contributor
timestamp: December 06, 2020, 08:18:20 am
content: The arecibo installation was more than just a big dish an receiver. The special feature was the ability also to actively send. A large dish in space may be possible, but transmission in the MW power range would be hard from space.The radar capability is, what is needed to get accurate orbital data for asteroids. Not sure how good one could add a powerful send part to existing radio telescopes.There may have been some military (space flight related) use in the initial phase, for upper atmospheric studies, but this should by now be mainly finished and common knowledge. The atmospheric studies are more like helping understand climate change and effects of pollution.The military does not need such a dish any more.Compared to space missions rebuilding the dish would be relatively cheap. The tricky part could be more like getting the funding for the ongoing costs, so we don't get the next collapse by 2050. A chance would be if NASA decides to forgets about maned space missions - lots of money to set free.

author: CJay
author_rank: Super Contributor
timestamp: December 06, 2020, 09:16:32 am
content: Quote from: BravoV on December 06, 2020, 08:04:48 amI agree, looking in from the outside, talking to relatives and friends in the US, the 'American dream' looks like a nightmare for an awful lot of people and it all stems from a basic lack of humanity in the belief that, to quote a fictional character, "greed, for lack of a better word, is good. Greed is right. Greed works. Greed clarifies, cuts through, and captures the essence of the evolutionary spirit."

author: magic
author_rank: Super Contributor
timestamp: December 06, 2020, 09:42:11 am
content: "American dream" boils down to the concept that it's viable to relinquish responsibility for "your world" and live comfortably in "a better world".People who emigrate to Western countries will never learn

author: CJay
author_rank: Super Contributor
timestamp: December 06, 2020, 10:00:08 am
content: Quote from: magic on December 06, 2020, 09:42:11 amThere's nothing wrong with wanting better but it goes wrong when you want your own life to be better at the expense of others and that happens in every country.

author: Ian.M
author_rank: Super Contributor
timestamp: December 06, 2020, 10:17:02 am
content: Before the Arecibo site could be reused, there's a lot of work to be done scrapping the failed platform, and probably the reflector, though some of it may be salvageable. However its all near-ground so wont require more than ordinary heavy plant to do so, and could be undertaken with local labor, which would obviously benefit the local community.If a rebuild was funded internationally by a coalition of universities and other academic bodies its likely the funding would be more stable than if it relied on US government funding subject to short-term political pressures.

author: coppercone2
author_rank: Super Contributor
timestamp: December 06, 2020, 08:16:11 pm
content: the only way you can screw up local labor is have them work unsafe on a rich foreign project (don't pull a stadium job)

author: Homer J Simpson
author_rank: Super Contributor
timestamp: December 08, 2020, 12:18:01 pm
content: Tour of Arecibo from 2017.

author: TerraHertz
author_rank: Super Contributor
timestamp: March 06, 2021, 10:22:49 am
content: My son is in Puerto Rico atm, and sent this drone footage he took. Shows state of the cleanup at Arecibo.https://youtu.be/N9U_i4ktPr8Quote

author: coppercone2
author_rank: Super Contributor
timestamp: March 06, 2021, 08:34:21 pm
content: giant pizza

author: cdev
author_rank: Super Contributor
timestamp: March 06, 2021, 09:49:09 pm
content: Gorgeous solid video. Does he use GPS to control/take it? He must. How does that work? Could you share anything about his drone setup?Such a beautiful area too. That must be beautiful. scenery there. .

author: cdev
author_rank: Super Contributor
timestamp: March 06, 2021, 09:54:02 pm
content: Quote from: Ian.M on December 06, 2020, 10:17:02 amInternational procurement rules probably apply which puts local firms at a huge disadvantage. They would have to underbid firms from countries where workers are paid almost nothing. And they would probably underbid to get a job like that they they could use in their advertising.

author: Ian.M
author_rank: Super Contributor
timestamp: March 06, 2021, 10:15:38 pm
content: Quote from: cdev on March 06, 2021, 09:54:02 pmIt would be very difficult for companies using 'slave wage' foreign workers to use them on a contract in Puerto Rico. Its a US territory under US visa rules, and they'd need to getH-2Bvisa for all their 'grunts'. A company can certainly bring in a core of specialists, but they'd have to recruit the 'grunts' locally or from the USA.

author: cdev
author_rank: Super Contributor
timestamp: March 06, 2021, 10:39:14 pm
content: The banks want the real estate. (in Puerto Rico) And so do the real estate speculators. The land in Puerto Rico is beautiful, too beautiful for it's poor people, thats how they think. If they lend money to poor people and they default, they get to foreclose on it all in most states here, the borrowers lose their entire investment. . This is the divine right of capital, that's how it works. the coronavirus is causing a lot of families to fall off the edge of the economic map.; And likely, windfall profits for banks, wealthy investors, and many others. Just yesterday I read the story of Poshawn Brown. It's heartbreaking. She probably had cryptic covid-19 and didnt know it. She worked for Amazon. At a large warehouse they have in Virginia. They had tasked her with giving COVID tests to other workers. She has no medical training at all but she knew it was a risky situation. But they didn't give her adequate PPE. She should have said no, but she had a daughter so she just did what they asked her to. They could not even afford an autopsy for her. She leaves an 8 year old daughter.Quote from: CJay on December 06, 2020, 09:16:32 am

author: cdev
author_rank: Super Contributor
timestamp: March 06, 2021, 11:55:34 pm
content: As we agreed to let them bid, its part of the WTO, its quite likely we'll have to let them actually perform the work if they win.This is the subject of a WTO dispute. Its estimated by Princeton economist Alan Blinder that 26% up to perhaps as many as half - yes half or more of the jobs in the US and the EU are outsourceable and may be outsourced within the coming years. The financial incentive is huge. Trillions of dollars a year. So I stand by my statement. I'm not saying that foreign firms have anything wrong with them. They want the work and they are having riots over the lack of jobs. SO there is no doubt that they need them. They have large numbers of workers with engineering training, more than the US. They speak excellent English. Also, we made a deal. We now have a debt in many kinds of jobs we must repay. If they bid the lowest, they get the jobs, its an entitlement. you bring up an important issue, wage parity. Do we have a right to demand that they pay wokers a legal US wage before they come here to work, typically for a period like six years. This dispuite is - the important issue has quite a history. Recently, the US government ruled that they must pay workers at least a legal US wage for the area whee they were supposed to work. which in this case was more than eight dollars an hour. USCIS ruled that paying a quality control engineer supposed to work in the Portland area the equivalent of around $6:50 an hour in a foreign currency was too little. This is what globalization is all about, trade in services agreements. Its the main goal, vastly lowering wages and increasing profits internationally.Quote from: Ian.M on March 06, 2021, 10:15:38 pmThats not how I feel at all. I think we should pay everybody a living wage. I don't agree with neoliberal dogma which doesnt accept the concept of a 'living wage' .also indeed, the people they bring in have to have special knowledge, and they also have to prove that they tried to find local workers they typically do this by placing an ad online and having local workers interview for a job, even if they already have somebody in mind. I have placed these ads and had their purpose explained to me.The use of workers from back home in their most expensive positions saves them millions, even billions of dollars. Otherwise it would be much less profitable working in the US, and of course thats the most important thing.This all goes to show the near-futility of some kinds of regulationin the face of trade agreements. Such as minimum wage laws and laws on overtime and working conditions. When they become the subjects of trade agreements they are toast.

author: nctnico
author_rank: Super Contributor
timestamp: March 07, 2021, 01:05:19 am
content: Quote from: Kleinstein on December 06, 2020, 08:18:20 amLate reaction but from some indirect interactions with the radio atronomy community I understand that they are no longer into building really big dishes but are going to link up many smaller dishes. The advantage is that this also allows to be able to pinpoint from where signals are coming from.

author: james_s
author_rank: Super Contributor
timestamp: March 07, 2021, 05:23:36 am
content: Quote from: cdev on March 06, 2021, 09:49:09 pmThere's a huge amount of information out there about multirotor UAVs. This stuff is widespread and complete ready to fly "drones" capable of this sort of video footage have been available off the shelf for close to a decade if not more. You can walk into any hobby store and buy one for a few hundred bucks.

author: coppercone2
author_rank: Super Contributor
timestamp: March 07, 2021, 05:55:39 am
content: Quote from: nctnico on March 07, 2021, 01:05:19 amI think you will have a lower bandwidth though. But the minimum they measured is 300MHz which is only 1 meter, so this is fine. But if I recall, they had low frequency transmitters on there. 5MHz. The VLA can do 90MHz.The 300 meter dish is 22 dB at 5MHz.If you have a bunch of small dishes how does the math work out with that? Not sure if its identical.

author: David Hess
author_rank: Super Contributor
timestamp: March 07, 2021, 10:35:17 am
content: Quote from: nctnico on March 07, 2021, 01:05:19 amThe huge amounts of cheap digital processing available now allow aperture synthesis unlike back when Arecibo was built. Integration makes individual transceivers inexpensive.

author: fourfathom
author_rank: Super Contributor
timestamp: March 07, 2021, 03:59:31 pm
content: A single large dish will have a lower noise floor than an array of smaller dishes. This is because a small dish has lower gain before the preamp. In an array, each dish/preamp sends the amplified signal to a delay/combiner stage where the Synthetic Aperture beam steering is done. Assuming similar amplifier noise figures, the higher-gain antenna will have better sensitivity. But a very large array can create a smaller beam angle than a practical big dish, reducing the cosmic background noise and other off-angle pickup. The large arrays have significant operational performance advantages, just not for very weak signal work.This reminds me of a discussion I had regarding radar reflectors (used on boats), and how they compare to optical reflectors (mirrors). An X-band radar runs around 10 GHz.My 12" diameter octahedral radar corner reflector compares (in wavelengths) to an optical light mirror about 2.5 miles x 2.5 miles. There's probably some analogy here to the angular resolution of radio astronomy antennas vs optical telescopes.[edit: I got these backwards. My 12" radar reflector is wavelength-equivalent to an optical mirror 0.000188" in dia. Or, taking my 2x3" emergency signaling mirror and scaling up to radar wavelengths would give a radar reflector 2 miles x 3 miles. ]

author: CatalinaWOW
author_rank: Super Contributor
timestamp: March 07, 2021, 04:34:05 pm
content: Quote from: fourfathom on March 07, 2021, 03:59:31 pmI think you got your optical/radar comparison backwards. A 12 inch optical reflector is roughly the same number of waves across as a 2.5 mile radar reflector. Or said another way the two reflectors would have comparable beam patterns.

author: fourfathom
author_rank: Super Contributor
timestamp: March 07, 2021, 05:25:35 pm
content: Quote from: CatalinaWOW on March 07, 2021, 04:34:05 pmYes, thanks for catching that. I was grabbing quotes from a previous conversation and got things scrambled. Speaking of scrambled, I realized my error while I was eating breakfast, and rushed back here to discover that you had already found it. (I hoped I could sneak in and fix it before anybody noticed!)

author: MathWizard
author_rank: Super Contributor
timestamp: March 07, 2021, 08:41:50 pm
content: Anyone remember the early X-files episode where they went to Arecibo ?

author: coppercone2
author_rank: Super Contributor
timestamp: March 07, 2021, 09:16:36 pm
content: is reflector effiency and everything constant when dish size decreases?I.e. 5MHz is 60 meters, the dish is 300 meters, so it is large in comparison to the wavelength.If your dish is too small for the wavelength what happens? But what is the deal with that telescope, it transmits on 5Mhz but only picks up a minimum of 300MHz?

author: CatalinaWOW
author_rank: Super Contributor
timestamp: March 08, 2021, 01:36:17 am
content: Quote from: coppercone2 on March 07, 2021, 09:16:36 pmThere is no simple answer for these questions. Reflector efficiency (a term that needs some definition if you want to get down to details) tends to drop as reflector size gets small wrt wavelength. Small also requires some definition. For a visible optics person a reflector that is only five wavelengths across is extremely tiny. But at 60 meters it is actually huge. The simplest way I know to think of it is this. The beam reflected from a parabolic dish goes to a point in the ideal case. Reflectors hundreds or thousands of wavelengths across approach this ideal, with the differences from ideal often being dominated by imperfections in the geometry of the reflector (remember the Hubble kefluffle). As reflector to wavelength ratio drops the reflected wave is diffracted and departs significantly from the ideal case, even if the reflector has perfect geometry. Soon that point from the ideal case becomes a blob approaching the size of the reflector. You start to have to trade collecting the reflected energy against blocking incoming energy from getting to the reflector.I suspect you have mis-interpreted some of the publicity sheets. I am sure the active radar function of Arecibo sent and received at the same frequencies. Perhaps as low as 5 MHz, but it seems likely to me that higher frequencies were used, if for no other reason than to penetrate the Heaviside layers. Arecibo was also operated as a passive receiver for radio astronomy. No reason for that function not to have different operating bands than the active radar.