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Baltimore's Key Bridge struck by cargo ship, collapses

wbaltv.com

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

#551

Post by throw0101b »

danpalmer wrote: post #501
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.

It's somewhat counterintuitive how much energy can be in something moving so slowly. I say somewhat, because when you're up close it's much more obvious, but you're right that on a video it doesn't look like much.

> It's somewhat counterintuitive how much energy can be in something moving so slowly.

Reminder: Kinetic Energy = ½mv^2

Squaring numbers can make them big in a hurry.

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

#552

Post by [deleted] »

purpleidea wrote: post #484
testfoobar wrote: post #10

You can look back on the livestream here to see the collision and collapse. https://www.youtube.com/watch?v=83a7h3kkgPg

Not sure how to yt-dlp a big section of that video without downloading hours and hours... I found this tool but not going to install C# for it. https://github.com/rytsikau/ee.Yrewind/

[deleted]

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

#553

Post by semi-extrinsic »

paddy_m wrote: post #445
secstate wrote: post #442

Earlier quoted context omitted.

Does that mean this was effectively captain error? Like in response to a power outage the decision was made to try to reverse and rather than arrest forward momentum it just pushed their forward vector into the piling?

I would tend to think so. The pilot should have anticipated prop walk and known that the ship had no chance of stopping before the bridge. I’m trying to find a color coded current map. Wind too. I wouldn’t expect wind or current to cause the pronounced heading change that is visible. The drift seems possible. Note: I’m an experienced dinghy/keelboat sailor, but lack virtually any experience driving boats under power,…

It seems the excellent windy.com has wind and current data from the incident still available. Looks like current was <0.2 kts and wind was 6 kts south-east. So both should be completely negligible.

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

#554

Post by paddy_m »

myself248 wrote: post #488
ianburrell wrote: post #482

Earlier quoted context omitted.

It wouldn't help with this accident, but you would think that the electronics would be on batteries. It wouldn't be too hard to have rack of batteries that would power the lights, instruments, radios, and sensors. Doesn't help if the propulsion or steering go out, but does make easier to know whats going on.

At least in small craft, bow thrusters are usually electric, with local batteries charged from the main engine room. I don't know what large craft are like, but it doesn't seem unreasonable that a bow thruster may remain operable even if the main engine fails. Clearly that's not required or they would've had it and used it, but it could be required if the regulations didn't suck. Furthermore, steering could absolutel…

The difference for a car and drive by wire system is that the failure mode of control systems on cars is normally catastrophic and dangerous. If a car loses steering or brakes, it will hit something within seconds 95% of the time.

That ship spent 1 (4:30 to 5:30) hour of a presumably 10-20 day voyage in a critical control section. The tugs left the ship right around 5:08 (43 seconds into the video). A much better policy for this case would be to have required the tugs stay with the boat until it passed the main span safely.

There were no doubt maintenance issues that led to this accident, but it is exceedingly rare for these types of failures to cause this type of catastrophic result.

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

#555

Post by jcgrillo »

araes wrote: post #541
paddy_m wrote: post #438

Youtube tracking analysis from a knowledgeable mariner. He says that at about 1:24 AM the ship loses power (from video feed) while traveling 8.5 knots. at 1:25.30 power is restored. at 12:25.59 the ship shows smoke. The ship has already drifted in the channel. It is believed that at this time the ship applied full reverse power as evidenced by the black smoke. (My analysis: the ship drifted but hasn't turned in the c…

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…

I'm not sure what configuration of props a ship like this has, but in my experience with a 40ft sailboat with a single propeller you have absolutely no rudder authority while reversing. I've read that some large ships also are direct drive--there's no transmission between the engine and the propeller, so "reversing" (if it's even possible) entails shutting down the engine and restarting it in reverse. This can be done with a two stroke engine. And yes, 8.5kt is not slow when you're displacing 100k tons, no correction will happen quickly.

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

#556

Post by vikingerik »

Retric wrote: post #370
denton-scratch wrote: post #294

Earlier quoted context omitted.

> Bridges only last for roughly 50 years. https://en.wikipedia.org/wiki/The_Iron_Bridge Opened in 1781, still in service and perfectly safe. Of course, there are no container ships nearby. But I reckon you could sail a container ship under it, given enough water; and to damage the bridge supports, the container ship would need climbing equipment. 1781 isn't many years after the Declaration of Independence.

I'll raise you: https://en.wikipedia.org/wiki/Arkadiko_Bridge But that's talking about the tail end of the bell curve not it's center.

That's also a much smaller scale. 22 ft long, 13 ft high, and carries only foot traffic or maybe horses. Much less is demanded of that structure than of a river-spanning mile-long truck-carrying bridge.

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

#557

Post by ultrarunner »

paddy_m wrote: post #438

Youtube tracking analysis from a knowledgeable mariner. He says that at about 1:24 AM the ship loses power (from video feed) while traveling 8.5 knots. at 1:25.30 power is restored. at 12:25.59 the ship shows smoke. The ship has already drifted in the channel. It is believed that at this time the ship applied full reverse power as evidenced by the black smoke. (My analysis: the ship drifted but hasn't turned in the c…

I'm once again impressed that subject matter experts are out there on every topic, and they are often capable of quickly and accurately disseminating information about an event far better than the local news.

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

#558

Post by HumblyTossed »

Amazing how many people are shocked that the bridge collapsed like that. That was one huge ship! Bridges are in a carefully balanced state of tension and compression, if anything as significant as a large container ship upsets that, I'd be shocked if it survived.

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

#559

Post by paddy_m »

semi-extrinsic wrote: post #553
paddy_m wrote: post #445

Earlier quoted context omitted.

I would tend to think so. The pilot should have anticipated prop walk and known that the ship had no chance of stopping before the bridge. I’m trying to find a color coded current map. Wind too. I wouldn’t expect wind or current to cause the pronounced heading change that is visible. The drift seems possible. Note: I’m an experienced dinghy/keelboat sailor, but lack virtually any experience driving boats under power,…

It seems the excellent windy.com has wind and current data from the incident still available. Looks like current was <0.2 kts and wind was 6 kts south-east. So both should be completely negligible.

Checks out.

.2knots/hour = 405 yards/hour

It was 4 minutes from power loss to impact.

405 yards/15 = 27 yards. And that's if the ship instantly accelerated to a 0.2 kt drift, which it wouldn't. Wind acceleration on the vessel than current.

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