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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

#621

Post by jcgrillo »

BWStearns wrote: post #596
jcgrillo wrote: post #555

Earlier quoted context omitted.

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 don…

Since they were still moving forward while gunning it in reverse the rudder would still operate normally. They generally have bow thrusters too. I have no idea whether they could have been operational with the broader power/engine failures but if they were available I'm sure they were being used as well.

The question is what is the velocity of the water moving over the rudder? If forward velocity and the current due to a reversing prop cancel, then the rudder can't do anything.

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

#622

Post by mcv »

jcgrillo wrote: post #594
OJFord wrote: post #497

Earlier quoted context omitted.

Apparently (this is just via someone on Reddit who supposedly heard/read it somewhere) the ship mayday'd on losing power hoping the bridge could be cleared. But why not (or did it?) also just blast its horn repeatedly, drawing attention so people on or near the bridge would notice it and realise something was wrong and perhaps even where it was headed? I'm sure it's not allowed generally and not the protocol and what…

Blasting the horn repeatedly is not a standard signal, but there are standard signals which might apply to a situation like this, for example "vessel not under command", "collision imminent", "vessel reversing", etc.

Don't expect car drivers on the bridge to understand ship signals, though.

Also, how does the driver know what to do? Stopping on the bridge, even well before the point where the ship hit, was clearly the wrong choice. Authorities need to stop new cars from entering the bridge while those on it leave, but that takes more than a handful of seconds to arrange. Unless there are traffic lights, perhaps.

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

#623

Post by marpstar »

0cf8612b2e1e wrote: post #618

Let’s say you had infinite money and no paperwork filings required. What is the fastest possible timeline in which a replacement bridge could be designed and completed? Just removing the detritus of the current bridge sounds like a multi month affair.

I'd think that a place like an international shipping port would have equipment in relatively close proximity for handling (albeit much smaller) tasks like wreckage removal and the like.

I have no idea what a practical timeline would be, but I think it's fair to say that it's less than your average 1.6 mile bridge.

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

#624

Post by hammock »

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…

>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 would hope, given the economic and humanitarian consequences of a crash, that we have simulators for this

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

#625

Post by Philadelphia »

matthewdgreen wrote: post #234
Par_Avion wrote: post #80

Oh, this makes me feel bad for Baltimore. Only bad news seem to come out of this town. Its reputation -- both domestically and internationally -- is mostly informed by The Wire, Freddie Gray/BLM, a dysfunctional city government, the 2019 ransomeware attack, the spoiled batch of J&J Covid vaccine... and now this. It's a real shame. It's a good place.

We’ve also got cherry blossoms, some good ramen and a few good breweries. Shocking lack of excellent Mexican food, however. And some world-class hospitals and universities. Don’t take TV shows so seriously.

BMore Taqueria in Fells Point is pretty good.

https://www.bmoretaqueria.com

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

#626

Post by Repulsion9513 »

JumpCrisscross wrote: post #538
hgfghj wrote: post #521

Earlier quoted context omitted.

That ship had a 10,000 TEU capacity and was actually hauling a little under 5,000 TEUs. An empty container weighs a little over 5,000lbs, and a full one can be up to 67,000lbs. If you do the math, you find that it’s just an astronomical amount of momentum, and there’s no effective defense for a bridge that needs support in more than 30 or so feet of water.

> there’s no effective defense for a bridge that needs support in more than 30 or so feet of water You deflect it. Failing at that, you direct the force into destroying the ship. Of course, the best solution is no in-water pylons. But that isn’t always feasible.

> direct the force into destroying the ship

Nice immovable object you've got there.

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

#627

Post by mc32 »

thekid314 wrote: post #597
paddy_m wrote: post #568

Earlier quoted context omitted.

On ships like this the propulsion is separate from the steering. There is a separate rudder that is close to, but not attached to the prop and propshaft. The propshaft is fixed. The rudder doesn't just "restart in a random position" it would remain in the previous position unless there was a physical piece that broke in the rudder gear. The fact that ship was able to reverse hard ( as evidenced by the slowdown), indi…

Was there a harbor pilot on board, or the normal ship pilot? Were there tug boats helping with the exit? I have often felt that the harbor protocols were overkill, but this is one of the times they could have helped.

The incident has some similarities ti the Cosco-Busan. It hit the base of the bridge piers and bounced off. The bridge wasn’t damaged.

That one was due to pilot error. The point is the pilot was still onboard but he was impaired by medication, the captain and mates kind of engaged in dereliction of duties contributing to the accident.

Obviously it’ll be a while before we know what happened in Baltimore.

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

#628

Post by db0255 »

apaprocki wrote: post #458
xoa wrote: post #296

Earlier quoted context omitted.

Just to put some numbers on this: The MV Dali (IMO#9697428) is a little over 95000 GT, or ballpark-ish probably around 114000 tons loaded (and it seems to have been loaded, which would make sense on departure). If it was going even 5kn (2.6 m/s) that'd be about 300 million newton-seconds, or about 3.3 times the momentum of a large jumbo jet like a 747 shortly at cruising speed (around 560 mph). It'd still have the sa…

"current draft is 12.2m with 116851 t DWT" and last reported speed was 6.7kt. Good estimation! :)

I saw radar that showed the ship was going 8.7 knots. And 7.6 knots before colliding.
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