Thinking about what happened in Baltimore and wondered if huge ships have a way to rapidly deploy anchors if the ship becomes uncontrollable close to shore. Independent of engine power.
In: Engineering
Dropping an anchor is usually a gravity-powered event. They just release the lock on the anchor and it free-falls into the water, as far down as they need it to go.
In the case of the Key Bridge in Baltimore, the *Dali* did, in fact, drop anchor; it just didn’t do a whole lot. Anchors won’t do much of anything to stop a moving ship, *especially* one that clocks in at just under 100,000 *tons*. At best, all they could have hoped for was that the drag caused by the anchor could pull the ship in a different direction.
On the bridge, there is an emergency anchor release. However, the release system runs on power (as does everything else nowadays). In the case of a blackout, there may be no ability for a bridge drop. To release the anchors without power, you would have manually open the brake at the anchor station. It is common for crew to standby the anchors when maneuvering in confined waters in case they need to manually drop the hooks.
However, ships have emergency generators which should kick in then event of a power loss. The anchor drop is usually on the emergency switchboard. The issue then becomes if you can fire up the emergency generator in time.
Yes, any ship operating in confined waters will have a team at the anchors ready to deploy one or more if it becomes necessary. In the case of the Baltimore Collision there have been reports that at least one anchor was deployed by the crew prior to the collision.
But you simply can’t stop something that massive quickly without extraordinarily destructive consequences. This isn’t a movie where dropping an anchor magically makes your ship stop in place, you’re trying to stop something that weighs the equivalent of 5 fully loaded freight trains – the anchor serves as a brake to slow you down, but if you don’t have enough distance, it will not stop you.
Anchors don’t work in real life like they do in movies. In movies anchors act like grappling hooks, they catch on something on the sea floor and immediately the chain pulls tight and the ship stops (Battleship). In reality an anchor is just the end bit that gives a little bit of bite or resistance to allow the chain to pull out and lie in the sea floor. Hundreds of feet of really heavy chain lying on the sea floor provides a steady point for the ship to hold on to to try and stay still…ish. If the ship starts moving too much it can gain enough momentum to drag the anchor and chain, slowing the ship down but not keeping it in place.
In the case of the Baltimore ship, it was probably redirected by some fluid dynamic forces due to an intersection of channels (kind of like lane keep assist does when coming up on an exit or lane split without a dashed line). This wouldn’t have been an issue under power, but just free floating it was.
After loosing power it was going too fast for its anchors to stop it before it hit the bridge. The best case would be to use the anchors to try and steer the ship, which they did, but turning a 100,000 ton skyscraper lying on its side and moving at 8mph is going to take a lot of chain and time to make a difference, they just didn’t have that.
To put it into perspective, the ship had 1.17B Newtons of force behind it. A typical 70mph car crash might be closer to 200,000N of force.
On top of the other answers I’d add that a substantial length of anchor chain would have to be deployed before the anchor flukes would bite into the sea bed, so that boat would still travel a significant distance before the anchor would have any chance of digging in anyway.
Anchor is a parking brake. Keep something already stopped from drifting.
It’s NOT brakes, to slow/stop something already moving.
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