Analyzing Video Footage Of Collapse of Massive Arecibo Telescope

hello it's scott manley here today the national science foundation had a press conference where they revealed footage of the collapse of the large facility at arecibo and well i'm i really kind of want to talk my way through all of this this is a camera down in the control room just showing how the whole thing went down literally that was footage by carlos perez who set up a gopro to record this j in case this happened it's important to realize there were observatory staff on site when this happened they were working in the safe areas as much as possible but it wasn't without risk and we are very happy to hear that nobody was injured during this collapse i'm going to come back to this video but i want to look at the second video which is taken from a drone which was inspecting cables on tower 4. the drone was being operated by adrian who was one of the technicians on site and the drone would have been sitting like right there when things started to go wrong and i've never seen a cable failure so close remember these are three inch steel cables which are carrying hundreds of tons of load it happens really fast the center cable has a small break then it pulls itself out of the socket then the other cables start failing the cable supporting the line feed is the last one to go the drone then turns around and we get to see the platform falling into the side of the dish we get missing material falling down and yeah everything is over in less than 30 seconds i mean there's still debris fluttering down and your dust settling but you can see the massive scars left in the dish and the debris that has been smashed on the mountainside i i i don't want to turn this video into rubbernecking disaster images but i've had a lot of people ask me to talk about this and talk about the dynamics and where it can go from here but before i dive back into frame by frame analysis of the demise of this let's just take a look at what it once was in its prime this glorious monument to science able to look back to some of the earliest parts of the universe and also look at some of our closest neighbors in ways that other instruments could not the arecibo telescope is truly a unique instrument and yes there is a bigger radio telescope but it doesn't do radar it doesn't have the same uh wavelength limits but of course that's me cherry-picking the things that are sibo did very very well this is of course i say i receive what we're really meaning is the 305 meter dish at arecibo there are other instruments on site but this is clearly the most prominent one and i believe that it should be visible from space with the naked eye if you know where to look so let's talk about that footage why was there a drone there they were using drones to inspect the cables in fact they had been very actively inspecting the cables because they knew the cables were going to break soon and there's a web page here that catalogs strands observed breaking inside these large thick cables these are before and after photos and you can see the paint popping off and wires popping out these are bundled together strands of hundreds of steel wires they need to be bundled so that they're flexible and as they break they break one strand at a time so at the start of the drone shot you can see three cables hanging onto the top of tower number four the three lower cables are the primary cables that were used to support the platform these date from the 1960s the cable above is part of the cable system that supports the catwalk and the waveguide there are supposed to be four primary cables but the fourth one broke in november which ultimately led to this collapse but if you look on the saddle there are a bunch of wire sticking out of the top these are the remains of that fourth cable that broke and if you're wondering what that black strap is that's connecting two cables that's part of a pulley system which was used to lower the socket from the first cable that failed it just slipped out of its socket rather than snapping so the other two support cables were attached to a structure that was added in the 1990s so this is a frame from later in the video and one of them is missing because that's the one that fell out but the one nearest us you can see hanging down there that's after the tension has been dropped on this so that's where those cables are attached watch for them when things start moving okay so now the video is playing at one quarter speed and the cable to watch is the one in the middle the one the lower one with the black strap around it now you'll see it's lost a lot of paint that is because the cables have been snapping uh the wires have been snapping inside the cable and every time they do that they just knock the paint off the exterior so there's going to be a single break and when a single wire breaks the other ones shift a little to take up the load and so there's a bit of dynamic force going on as things the load moves around but eventually the cable appears to just pull out of its socket i mean you can see in this frame there's like one or two wires that are still there but everything else is moving to the left under the tension so the what happens at the end of these cables is they take all the wires and they spread them out into a wide bundle and put that inside like a cup shaped socket then they pour zinc inside that and the zinc of course sets and that way you have essentially a solid metal blob at the end and of course that's what's on the other side of the saddle being held in by this structure so now that load is being released you've got even more dynamic redistribution of load between the other cables and they're now handling a static load would be twice what they're supposed to handle of course dynamic loads are going to be even higher and if you look the cable behind it is already starting to come apart and it is going to snap but watch the cable nearest us that it's nice and clean and white but as it becomes the main load-bearing object just watch all those wires snapping inside of this very very quickly it had been doing such a good job up until this moment but it was more than it was designed for and now it parts ways and at this point all the main cables have snapped and the platform is beginning to fall down under the force of gravity you can also notice by the way the previously broken cable the socket has now been pushed out the other side and that those cables are sticking up over the top are now falling away down the back so as the drone backs away the auxiliary cable at the bottom of the frame you can see it wobbling and falling down the cable at the top is still trying to support the wave guide and the catwalk but that is gonna end up getting hit and so it snaps and you'll see a wave go into it now looks like it snaps from both ends because of a shock impinge uh hitting that cable and that force is basically coming from the destruction of the catwalk you can see it at the top sort of in the the curving across the cables from the platform are smashing through that and pulling the cable free so all that cabling is now falling towards the dish and it will you'll see the scars that it makes in the dish as it hits the surface but also watch carefully on the left side you can see the top two segments of the tower i believe that is like 150 feet um you know 45 meters worth of reinforced concrete falling down and equally as it pans across you can see a smaller chunk of tower number 12 falling down so anyway i think that's all the important things to see from the drone footage let's switch over to the gopro footage from the control room so again i'm going to run this at a quarter speed so looking at the triangular platform you've got the curved azimuth arm hanging underneath it and that runs on a circular rail now as the platform begins to fall and get pulled sideways by the cable tension this basically jumps off its rails and begins to fall down but it also does it with such aggression that if you watch as it fades below the bottom it actually starts to bend and break simultaneously you can see the support cables for the platform just smashing through the catwalk and the waveguide and of course that's the force that causes the final cable to snap on the distant tower the distant tower now begins to fall over because it has all the tension on those backstay cables that are used to keep the tower solid also now tower 12 comes down and you can get an idea for the scale of this by seeing the platforms and ladders that are attached to the end of this thing again this is a horrendously dangerous place to be right now those cables would be lethal if you were hit by one so again we're really lucky that nobody was injured during this very violent event so anyway after the dust settled a bunch of journalists were publishing photos and these were the best photos i saw from it this is by juan costa of notice ellen he actually early on and after arecibo's first cable failure he emailed me a bunch of links saying you know trying to help me give me clues on what i should cover these are the uh concrete towers you can see the rebar sticking up there i don't think these are up to modern standards to be honest and that's the triangular remains of the platform which was just thrown hard against the side of this hole essentially like a slingshot the conference center and a bunch of other buildings were seriously damaged by falling cables some can be repaired some will have to be demolished and rebuilt but even before the cleanup can start they're going to have to clear roads this is a tower number eight the top of this has basically blocked one of the access roads there will be a massive cleanup operation for months to come and i would love to think that in the future there is the will and the money to rebuild something in this space that is comparable and as functional and as important to not just the scientific community but to the local populace who saw this as a an important part of their island there are of course petitions already being set up to try and put some political pressure on various people to make something happen again i i think the national science foundation have pretty much said there is a standard process for you know bidding and proposing such contracts which is sort of code speak for if something comes up with this sufficient merits it might be considered but equally i think that big projects like this are very much driven by politics and in that front puerto rico has a problem because it doesn't get the same representation as the states in the united states but as a site for future projects the existing site has many advantages it's already gone through a lot of the environmental impact requirements it has the radio quiet zones already figured out and perhaps most importantly there's a bunch of local people that have already worked on such they've grown up with this telescope and they understand how to make something of this magnitude work i really hope that we will be looking forward in a few years time to what will be on this site as opposed to merely looking back at what was on this site i'm scott manley fly safe [Music] you

Channel: Scott Manley

Views: 2,841,878

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Id: 59WQIRvezzI

Length: 12min 56sec (776 seconds)

Published: Fri Dec 04 2020