Baltimore's Key Bridge struck by cargo ship, collapses • Hacker News Board

Re: Baltimore's Key Bridge struck by cargo ship, collapses

#681

Post by munificent » Tue, Mar 26, 2024, 7:50 PM UTC

OJFord wrote: post #536

munificent wrote: post #532

Earlier quoted context omitted.

> But why not (or did it?) also just blast its horn repeatedly, Hard to blow your electrically driven horn when you've lost power.

I suppose I assumed it was compressed air, that once you had a 'full' (at pressure) tank, you could do a certain amount of blowing even without power. But fair point, I don't really know how they work, and if they are actively electric I certainly didn't know that and obviously that wouldn't have worked and so there's the answer.

> I assumed it was compressed air, that once you had a 'full' (at pressure) tank

Even so, it probably still requires electricity to activate the solenoids to open the valves or whatever. I'm speculating since I don't know how large boat horns work, but I wouldn't be surprised if they require power.

Re: Baltimore's Key Bridge struck by cargo ship, collapses

#682

Post by shagie » Tue, Mar 26, 2024, 7:50 PM UTC

brewdad wrote: post #647

shagie wrote: post #516

Earlier quoted context omitted.

https://en.wikipedia.org/wiki/Maritime_pilot#Compensation > The Florida Alliance of Maritime Organizations reported that Florida pilots' annual salaries range from US$100,000 to US$400,000, on par with other US states that have large ports. Columbia Bar pilots earn approximately US$180,000 per year. A 2008 review of pilot salaries in the United States showed that pay ranged from about US$250,000 to over US$500,000 pe…

Columbia Bar pilots are grossly underpaid.

Having visited the Columbia River Maritime Museum (I would strongly recommend if there) https://www.crmm.org - that is 100% correct. Its a place that they send other pilots to do things like rough water training.

Re: Baltimore's Key Bridge struck by cargo ship, collapses

#683

Post by phyzome » Tue, Mar 26, 2024, 7:51 PM UTC

theluketaylor wrote: post #415

master_crab wrote: post #364

Earlier quoted context omitted.

Also want to highlight this for another reason. At slow speeds rail and boats suffer from far less “moving” friction than road vehicles. So once off there is very little slowing them down vs cars and trucks that suffer from high rolling friction.

Grady Hillhouse of Practical Engineering recently did a great demo of this. He was able to pull his car in neutral and an empty train car on rails with roughly the same force. https://www.youtube.com/watch?v=nGhBHrr5CYQ

I think it's actually in an earlier video, and he wasn't able to actually pull the train car due to track irregularity -- but according to calculations he should have been able to if there was a safe way to give it a bit of a nudge.

Re: Baltimore's Key Bridge struck by cargo ship, collapses

#684

Post by wlll » Tue, Mar 26, 2024, 7:52 PM UTC

mcv wrote: post #616

wlll wrote: post #573

Earlier quoted context omitted.

> in my experience with a 40ft sailboat with a single propeller you have absolutely no rudder authority while reversing. In general it depends on the rudders and the boat. Longer keeled boats don't respond well in reverse at all but more modern boats (like mine, 1990) will do better but will still need some way to have steerage. I can certainly manouver around the marina in reverse, it's just harder than forwards and…

Going backwards in the marina I often steer on the engine rather than the rudder (though I keep the rudder aligned with the engine of course). Obviously that's in a tiny sailing boat with an external engine, but I thought large ships also often have a steerable front propeller to assist with steering and mooring. Although maybe these very large ships use tugboats for that.

My boat has an inboard diesel so no ability to direct the prop. It does have a bow thruster, but it's only really used at slow speed, usually right at the point of docking and undocking in tight spaces, once you get the boat moving in forward or reverse you don't need it.

I have no idea about container ship sized boats, though I'd imagine a bow thruster of steerable prop might not be practical at that scale.

Re: Baltimore's Key Bridge struck by cargo ship, collapses

#685

Post by amluto » Tue, Mar 26, 2024, 7:55 PM UTC

moritonal wrote: post #586

bastardoperator wrote: post #494

Earlier quoted context omitted.

The video is surreal, it looks like it barely bumps the bridge and 2 seconds later the entire thing is gone. I don't know what I was expecting, the bridge just looked extremely fragile, makes me wonder what other bridges are at risk of an event like this.

When you play about with game engines long enough, you start to realise that momentum is the key metric to track rather than speed. Especially in water magnitude can be very deceiving but to give some quick math, this vessel had a momentum at impact of about 154,000,000kg⋅m/s. For a car to have equivalent momentum it'd have hit the bridge at 156,580 mph. Humans are just less adept at appreciating mass vs velocity.

Energy matters, too. That hypothetical car has the order of 1 kiloton of TNT of kinetic energy. The resulting blast would have been large.

(This is about the estimated yield of the Beirut explosion.)

I would rather get hit by a slow moving object than a fast one with equal momentum.

Re: Baltimore's Key Bridge struck by cargo ship, collapses

#686

Post by shaboinkin » Tue, Mar 26, 2024, 7:55 PM UTC

bmitc wrote: post #668

dathinab wrote: post #202

Earlier quoted context omitted.

At least in the links with the video now you can see that the container ship directly hits one of the two main (and in the central area only) pillars completely collapsing it. No matter(1) the engineering there is no pretty much way to not lose the whole large middle area and left area leading to the destroyed pillar in that situation. Such a collapse crates so much force (tension vibrations etc.) so that the collaps…

I mean, yes, everybody is pointing out about the mass of the container ship, but that's actually to the point of the above question and my question. Because the ship's size and weight are obvious. Were ships this size regularly passing by or under this bridge such that this scenario was effectively bound to happen given a ship failure and/or pilot error? That's my question. I'm not familiar with port activities, so i…

That was my thought. The supports look like toothpicks relative to the ships that routinely pass through. I don't know enough about the forces involved here, but I'd like to think when they rebuild, they will add some sort of deflection capabilities around the supports that ships must past in between. But again, I don't know what that would take to deflect a massive ship like this. In hindsight, the bridge looks terribly exposed given the persistent risk of ships passing through.

Re: Baltimore's Key Bridge struck by cargo ship, collapses

#687

Post by pixl97 » Tue, Mar 26, 2024, 7:56 PM UTC

OJFord wrote: post #518

themerone wrote: post #506

Earlier quoted context omitted.

Why would a driver think a ship's horn was signaling them?

AIUI most souls on the bridge were construction workers filling potholes, not drivers. But either way I'd have thought a certain amount of horn blowing would catch my attention just for being out of the ordinary, even though it's also not ordinary for ships to (need to) signal me.

Ya the people on the bridge would have less than 4 minutes to figure out the ship is crashing then to clear 2500 feet of bridge. When you're working with construction equipment you'd probably not notice till you had seconds left.

Re: Baltimore's Key Bridge struck by cargo ship, collapses

#688

Post by doer1984 » Tue, Mar 26, 2024, 7:56 PM UTC

TaylorAlexander wrote: post #66

Somehow I find it surprising how completely the bridge collapsed after the damage. I understand that a container ship collision is serious, but you could imagine a scenarios where the bridge slumps or buckles but doesn’t just disintegrate like that. It’s surprising that ships capable of doing this damage were probably regularly driving past it, and its safety as a thoroughfare depended entirely on those collisions no…

Ironically, simply bulking up the ground around the piers would have had the ship run aground; at 8 knots the ship would have slowed to a stop within several yards, and suffered minor damage, maybe would have required being tugged back into clear waters. Running aground puts the majority of impact into a downward force absorbed by the earth. It's hard to build a bridge pier that will withstand 200,000 tons of direct impact, no matter how slowly that's moving.

Re: Baltimore's Key Bridge struck by cargo ship, collapses

#689

Post by joelshep » Tue, Mar 26, 2024, 7:57 PM UTC

traceroute66 wrote: post #649

araes wrote: post #541

Earlier quoted context omitted.

Current personal suspicion after watching your linked video (excellent discussion by the wgowshipping author) is: Catastrophic engine failure (1:24) causing wide scale power loss. No rudder control, rudder drift, and ship alignment drift (1:24-1:25:30) Power restored and ship reengages prop with bad ship/ruddder alignment (1:25). However, ship is now pushing itself into a further bad turn. Pilot likely stomps the bra…

> How many pilots, trained or not, really have any experience with a 100,000 ton ship in a crash situation with responses where seconds matter? I think you are missing the point. Clearly I am speculating, but I don't think any more experience would have helped in this event. Why ? I think what happened today was almost entirely down to not being able to fight the basic Laws of Physics. Its a well known fact that enor…

To continue the speculation ... as a ship that size is slow to turn or halt, that seems to suggest that even if the ship hadn't suffered a power failure then it would have passed quite close to the bridge pier anyway. Was that expected?

Re: Baltimore's Key Bridge struck by cargo ship, collapses

#690

Post by doer1984 » Tue, Mar 26, 2024, 7:58 PM UTC

TaylorAlexander wrote: post #66

Somehow I find it surprising how completely the bridge collapsed after the damage. I understand that a container ship collision is serious, but you could imagine a scenarios where the bridge slumps or buckles but doesn’t just disintegrate like that. It’s surprising that ships capable of doing this damage were probably regularly driving past it, and its safety as a thoroughfare depended entirely on those collisions no…

Simply bulking up the ground around the piers with loose fill or monolithic concrete would have had the ship run aground; at 9mph (the recorded impact speed) the ship would have slowed to a stop within several yards, and suffered minor damage, maybe would have required being tugged back into clear waters. Running aground puts the majority of impact into a downward force absorbed by the earth. It's hard to build a bridge pier that will withstand 200,000 tons of direct impact, no matter how slowly that's moving.