what will it take to sink a medium sized cruise ship

To answer OP's original question - loads of water in the wrong place (i.e. inside the ship).

How that water gets there is a whole different story - we have had various suggestions: torpedoes; stupid captains; rocks; icebergs etc..

I don't think that a BFO ship like Anthem of the Seas is going to get swamped by the sea per se - it would need something else to contribute to the ingress of sea water - hitting rocks would be most likely.

Capsizing might be a possibility, but the centre of gravity of these mega-ships is very low so capsizing is very unlikely (or so we are told).

(posted as a total landlubber whose experience of ships is as somewhere to get stuffed and drunk whilst on holiday:D)

Sorry --- while a likely contributing factor, not necessarily - a destroyer, USS Kearney, while on Neutralaity Patrol near Iceland before state of war existed, was torpedoed by a German U-boat and survived, as did battleship North Carolina hit by a Japanese torpedo in 1942 Solomons campaign. Torpedoes don't sink ships (although they certainly help) - only loss of bouancy sinks ships.

I think that one of today's torpedos would have sunk the Kearney and I also think it would sink a cruise ship.

Oh yeah! I just remembered something else....

Loose lips sink ships.

I remember when Louis Lipps played football against Warren Shipp (these are real guys)......could been a great headline there....:D

Basically lots of you are close. As Flatbush Flyer says, you have to fill the void in the hull with water to sink. As to rolling over, as opposed to capsizing for the purists, what causes that is free water in the hull. With everything in its place on the ship, and bolted/welded down or contained in a tank, a ship is like the punching clown. A very small weight at the bottom keeps the very tall clown coming back up for another punch. Until the weight in the bottom of the clown breaks free and can slide around inside the clown, and then he will go over and stay over. This is called "free surface effect" in ship stability. When a ship rolls one way the interaction between the center of buoyancy and the center of gravity will create a "righting arm" that creates a force to counteract the force causing the roll (wind and wave) to bring the clown back to upright, but then inertia keeps it moving, so it rolls the other way, until the righting arm again gets strong enough to bring the ship back upright.

Water in a space like an engine room, however, is "uncontained", so it will flow to the lowest point, which is the "down" side of the roll. This changes the center of gravity and affects the righting arm. So, free flowing water will negate the inherent stability of the ship, and can cause her to roll over, as the Herald and Estonia did.

Funny that people bring up the Normandie. She sank at the dock in NYC from just this effect: free surface. She caught fire while being converted to a troopship, and the NYFD responded with fire boats and hoses from shore, and poured so much water into her hull that she rolled right over on her side, sitting at the dock, close to where the ships now dock in Manhattan.

Basically, that is what would sink a ship. A breach of the hull that allows free flowing water.

A great big hole.

Basically lots of you are close. As Flatbush Flyer says, you have to fill the void in the hull with water to sink. As to rolling over, as opposed to capsizing for the purists, what causes that is free water in the hull. With everything in its place on the ship, and bolted/welded down or contained in a tank, a ship is like the punching clown. A very small weight at the bottom keeps the very tall clown coming back up for another punch. Until the weight in the bottom of the clown breaks free and can slide around inside the clown, and then he will go over and stay over. This is called "free surface effect" in ship stability. When a ship rolls one way the interaction between the center of buoyancy and the center of gravity will create a "righting arm" that creates a force to counteract the force causing the roll (wind and wave) to bring the clown back to upright, but then inertia keeps it moving, so it rolls the other way, until the righting arm again gets strong enough to bring the ship back upright.

 

Water in a space like an engine room, however, is "uncontained", so it will flow to the lowest point, which is the "down" side of the roll. This changes the center of gravity and affects the righting arm. So, free flowing water will negate the inherent stability of the ship, and can cause her to roll over, as the Herald and Estonia did.

 

Funny that people bring up the Normandie. She sank at the dock in NYC from just this effect: free surface. She caught fire while being converted to a troopship, and the NYFD responded with fire boats and hoses from shore, and poured so much water into her hull that she rolled right over on her side, sitting at the dock, close to where the ships now dock in Manhattan.

 

Basically, that is what would sink a ship. A breach of the hull that allows free flowing water.

Agreed.

And an inherent problem with roll-on roll-off vehicle ferries.

Herald capsized in calm seas, a few minutes after leaving port & getting up to speed.

Her problem was that when the bow-doors were left open (un-believable !!!) it needed the ingress of only a surprisingly small volume of water caused by the bow wave to travel the length the car-deck & start the free-surface effect (your words) / water sloshing from side to side (my words). As that side to side momentum increased it then started the cars & then the trucks sliding from side to side (they weren't secured, no need in the calm seas) and eventually the ship reached its tipping point. Very slow & eerily graceful.

Cruise ships are an entirely different & much more stable design :)

JB :)

A scud missile would do it.

A scud missile would do it.

....if it was aimed about 25 miles away. ;)

and

If it wasn't a dud. ;)

and

If it hit the cruise ship's kerosene storage tanks for its aircraft ;)

and

if it hit the cruise ship's stocks of missiles or armoury. ;)

In those circumstances, yes it might sink a cruise ship :D

JB :)

Workmate and hos wife were on Costa Concordia, they assure me a rock can do it.

Interesting typo given what (or who) appears to be the cause of Captain Schettino's inattention and poor judgment.

Interesting typo given what (or who) appears to be the cause of Captain Schettino's inattention and poor judgment.

:p

Lol sorry

Plenty of passenger ships [non cruise] still sink annually, usually the old bucket ferry types. It just doesn't get reported so much in the western media.

In light of what happened recently, what will it take to sink a medium sized cruise ship of about 80000 gross tons?

Something that breaches the integrity of multiple water tight compartments. Some examples might be some big rocks off the coast of Giglio Italy, or a torpedo or anything else that breaches the hull and causes free flowing water to get inside.

Something that breaches the integrity of multiple water tight compartments. Some examples might be some big rocks off the coast of Giglio Italy, or a torpedo or anything else that breaches the hull and causes free flowing water to get inside.

Spot on with the mention of multiple compartments. All cruise ships are divided into multiple watertight compartments that go all the way up to the deck above the waterline. This is why there are so many stairs to climb on the behind the scenes tours, because from any watertight compartment, to get to their friends cabin next door (but in the next compartment) they may have to climb up 2-3 decks, walk aft 15 feet, and back down 2-3 decks.

Nearly every cruise ship out there is designed as a "two compartment" ship. This means that flooding of two watertight compartments will not sink the vessel, but if 3 are flooded, then all bets are off. The hole Schettino tore in the Concordia breached 5 contiguous compartments. The infamous cell phone audio taken on the bridge even captures him questioning the engineers to confirm that 3 compartments were flooding and saying "if only 2 are flooding, we are safe, but if it's 3 we're doomed" (not exact quote). There was no force on God's earth that was going to keep the Concordia afloat.

Spot on with the mention of multiple compartments. All cruise ships are divided into multiple watertight compartments that go all the way up to the deck above the waterline. This is why there are so many stairs to climb on the behind the scenes tours, because from any watertight compartment, to get to their friends cabin next door (but in the next compartment) they may have to climb up 2-3 decks, walk aft 15 feet, and back down 2-3 decks.

 

Nearly every cruise ship out there is designed as a "two compartment" ship. This means that flooding of two watertight compartments will not sink the vessel, but if 3 are flooded, then all bets are off. The hole Schettino tore in the Concordia breached 5 contiguous compartments. The infamous cell phone audio taken on the bridge even captures him questioning the engineers to confirm that 3 compartments were flooding and saying "if only 2 are flooding, we are safe, but if it's 3 we're doomed" (not exact quote). There was no force on God's earth that was going to keep the Concordia afloat.

It is interesting that they are only "2 compartment" vessels. I can't recall a single one of these instances that didn't involve breaching multiple compartments. Even with the Andrea Doria, she was hit side on and it still breached multiple compartments and tanks. I realize safety costs money, but perhaps the standard should be a bit higher?

It is interesting that they are only "2 compartment" vessels. I can't recall a single one of these instances that didn't involve breaching multiple compartments. Even with the Andrea Doria, she was hit side on and it still breached multiple compartments and tanks. I realize safety costs money, but perhaps the standard should be a bit higher?

Well, actually, the Stockholm only breached one of Andrea Doria's 11 watertight compartments. It did breach 5 fuel tanks, which were mostly empty because the ship was near the end of the voyage. These empty tanks that were breached, filled with water and caused the Doria to list. This listing eventually brought the starboard side down to where there was down flooding into other compartments. But, the Doria stayed afloat for 11 hours.

The Concordia's breaching of 5 adjacent compartments is considered to be unprecedented.

And nearly every cargo ship out there is a single compartment vessel.

What other ships do you have in mind?

Well, actually, the Stockholm only breached one of Andrea Doria's 11 watertight compartments. It did breach 5 fuel tanks, which were mostly empty because the ship was near the end of the voyage. These empty tanks that were breached, filled with water and caused the Doria to list. This listing eventually brought the starboard side down to where there was down flooding into other compartments. But, the Doria stayed afloat for 11 hours.

 

The Concordia's breaching of 5 adjacent compartments is considered to be unprecedented.

 

And nearly every cargo ship out there is a single compartment vessel.

 

What other ships do you have in mind?

I was thinking of the Titanic, Andrea Doria and Concordia. I'm sure all the ocean liners serving as troopships that were sunk in both world wars had multiple compartments breached, although hits from multiple torpedoes are an unlikely occurrence for a cruise ship unless they are also pressed into service as a troopship.

Does a modern cruse ship have similarly placed tanks that would be empty at the end of a voyage and affect the ships stability if damaged? Something you mentioned earlier, the watertight bulkheads extend to a deck or two above the waterline. Are the bulkheads not sealed above such that water cannot spill out of the compartment into another no matter what without an interior breach, or is that only the case in naval vessels?

Obviously all three are due to operator error which exposed flaws in the ships' design for the Titanic and Andrea Doria.

I was thinking of the Titanic, Andrea Doria and Concordia. I'm sure all the ocean liners serving as troopships that were sunk in both world wars had multiple compartments breached, although hits from multiple torpedoes are an unlikely occurrence for a cruise ship unless they are also pressed into service as a troopship.

 

Does a modern cruse ship have similarly placed tanks that would be empty at the end of a voyage and affect the ships stability if damaged? Something you mentioned earlier, the watertight bulkheads extend to a deck or two above the waterline. Are the bulkheads not sealed above such that water cannot spill out of the compartment into another no matter what without an interior breach, or is that only the case in naval vessels?

 

Obviously all three are due to operator error which exposed flaws in the ships' design for the Titanic and Andrea Doria.

Well, I've talked about the Doria and Concordia. The Titanic had a flaw in that the watertight bulkheads did not carry all the way up above the waterline, so you got progressive flooding from one compartment to another.

If you've ever taken a behind the scenes tour of a cruise ship, and seen the I-95 corridor, whatever deck that is on (they number decks differently on different ships) is called the "subdivision" deck. At this deck, all watertight integrity stops, so that is where the stairs in each watertight compartment have to go up to, before you can take stairs in the next compartment back down. As an example, on the Norwegian Sky, the decks start numbering at "0" and go up. Deck 0 is the inner bottom, the lowest level in the ship (only tankage below). Deck 3 is the subdivision deck. So, there are 13 watertight doors on each of Decks 0,1,&2, creating 14 watertight compartments. If a compartment floods to the level of deck 3, then yes, it can downflood into the next compartment. But this is what the two compartment designation means. If two adjacent compartments flood, they will not bring the subdivision deck down to the waterline, and therefore you cannot progressively downflood.

The Doria was in ways ahead of its time, being built with a double hull. The fuel and water tanks were in between the outer and inner hulls. The tanks therefore, went from the keel at the centerline, out to the side of the ship in the double bottom, and then extended up the side of the ship. Therefore, both what we call a "wing" tank (in the side of the ship), and a "double bottom" tank (between the bottom of the hull and the bilge of the engine room) were the same tank, and were breached. This design created some large tanks that were now free to flood, bringing in a large weight of water, plus at the beginning, it was flooding in the wide double bottom tank, which is where free surface is most apparent, in a wide (side to side) compartment.

Today's ships tend to carry the fuel in double bottom tanks, which are only about 3 meters high in the space below the engine room, and these tanks are notoriously hard to hit unless you go aground. There's a whole bunch of hydrostatics that tell you the fuel can't leak out, and emergency ways to keep water from pushing the oil out the vents. Side tanks are ballast tanks, and since the weight of "cargo" on cruise ships (passengers) doesn't vary much, these tanks are almost always kept full.

Hope I haven't hopelessly confused you, but short answer is no, the ships today are designed differently than the Doria. The Concordia was opened above the double bottom, in the engineering spaces, which generally do not have tankage outboard, so the side of the engine room is the side of the hull. Schettino could not have breached the hull in a worse location.

Water in a space like an engine room, however, is "uncontained", so it will flow to the lowest point, which is the "down" side of the roll.

Would a series of "airbags", triggered by water, be able to prevent water to flow into the wrong direction? Or, with enough airbags, prevent water to enter the room in the first place?

When it comes to fatal accidents, Titanic is a must-study as to the chain of events that led to it. It remains the greatest loss of life on a ship in peace time (not war). That latter distinction goes to the German Wilhelm Gustloff.

https://en.wikipedia.org/wiki/MV_Wilhelm_Gustloff

Titanic had a chain of events leading to the sinking almost as long as its anchor chain!

The next has to do with aviation, the runway collision between Pan Am and KLM 747s at Tenerife , Canary Island in March 1977. To date, the worst aviation disaster of all times. It too had a long chain of events leading up to it.

If you manage to break a link in the chain, you have no accident, or at worst you have an incident.

Cheng, Titanic also had another fatal flaw, aside from her water tight bulkheads not extending far enough in the hull. That was the location of her coal bunkers (store rooms for those not familiar with the word).

On Titanic, they were not longitudinal along the sides on the ship, but went athwartship, thus across the ship from port to starboard. Considering the layout of the boilers, this made sense as it made coal handing much easier.

However, it removed an added layer of protection along the side of the ship where the "gash" occurred. Thus, the bunkers could have held back some of the flooding. They would have acted as a third hull, with it own top or "deck head". There would have been no overflowing from one bunker to another.

Ultimately, the final link in the chain came down to who was in command. On Titanic it was William Murdoch, first officer. On Pan AM / KLM it was Jacob Van Zanten. The Pan Am captain, Victor Grubbs, knew Van Zanten was a loose "cannon", and wanted to get off the fog shrouded runway before Van Zanten took off WITHOUT PERMISSION from the tower. "Get home-itis" often kills you every time, and this time it killed 588 people, and that final link of the chain was Van Zanten suffering from that.

With Titanic, most of the officers dealing with a new ship of that size, really had no clue. Not to mention that the Olympic class liners had rudders that were too small for their size.

When Frederick Fleet told Murdoch: "Iceberg right ahead" and Murdoch then saw it, he figured the best thing to do was to turn left, and he ordered the helmsman, Robert Hitchens to turn "hard a starboard". Hitchens turned the wheel to port as asked (yes, ask me why that sounds wrong), but then Murdoch sealed the fate of the ship with his next move.

He went to the engine telegraphs and ordered the engine room to go into reverse, to slow down the ship. MISTAKE!!

Aside from having too small a rudder, Titanic had three propellers. One of which was directly opposite the rudder. The two outboard props were run by steam piston engines (quadruple expansion to boot). The center prop was run by a Parson's steam turbine. Sadly, while the reciprocating engines could be reversed, the turbine could not, and had to be shut down.

Between the shutting down of the center prop and the turbulence caused by reversing the outer props, the too-small rudder had little water flowing past it, thus making it very ineffective, and slowing down the ship's rate of turn.

Had Murdoch just ordered the helm to turn, and not touched the engines, Titanic would just be a foot note in maritime history, likely scrapped with her sister, Olympic in the 1930s.

And therein lies the final link of an accident chain- command.

Not real sure if Titanic would have made the turn away. If he had kept the helm midships, and rammed the berg head on, he would have crumpled the bow, but the forward collision bulkhead was one that ran all the way up to the forecastle deck. Most likely he would have flooded this already partially full or full tank, and that would have been it. Reversing the engines while keeping the helm midships would also have helped, but of course the natural tendency is to not run into things head on.

a couple of technical points

Ships sink due to the loss of 'reserve' buoyancy. This is the amount of buoyancy in the hull that is in excess of what is required to keep the vessel afloat. If buoyancy equals displacement the vessel is neutral ... this is what we call a submarine. The can change their buoyancy under control.... Under normal conditions a ship has a great amount of reserve buoyancy and is "stable" Many factors contribute to this buoyancy and stability factor and there are "numbers" that can be assigned to each and are calculated relatively easily. A MAJOR job of the Captain/Master assisted by the engineer is constantly monitoring stability and reserve buoyancy; a primary factor in this is monitoring the 'liquid load'. This is the status of full/empty of every tank in the ship. An empty tank can be worse than a full tank in certain circumstances.

Double bottom hulls came into requirement as a way to prevent oil spills. Traditionally many tanks WERE on the bottom of the ship (or extended to the bottom) and since the most common place to get a hole is the bottom there was a high probability of spilling oil. (remember Valdeze) SO the use of double bottoms have been mandated, this began in oil tankers and oil barges but has expanded for obvious reasons. Using a double bottom as a fuel tank is a no no, although use for ballast or water would not be outside the law in some circumstances

When a ship is classified as a two compartment ship or a three compartment ship this is not saying breaching any two compartments will sink the ship. It means that if the RIGHT TWO are completely lost, THEN it is game over. Almost always the critical spaces are going to involve the engine rooms. This is how Concordia was doomed. They completely lost their two most critical spaces with no hope of a patch and recover. On many ship just lost of the engineering space alone is not 'the end' but requires a certain group of other spaces that contribute to a loss of buoyancy AND stability. SOLAS has been constantly improving the rules for 'compartmentalization' in passenger vessels making it harder and harder to sink (new construction)

Stabile ships roll ..... ships that don't roll tend to be less stable altho that's the ride the paying passenger wants. when approaching a disabled vessel for a SAR incident .... seeing looooonnnngggggg, slooowwwwww, deep rolls from side to side told me we had very serious situation. A vessel that rolled but snapped back upright .... that ship has decent stability

just sayin' ..... some of this discussion slid technical and IMO was pointing too some incorrect conclusions.

what I have here is some of what I still retain from three times attending Congressionally mandated training for prospective Commanding Officers of Coast Guard Cutters. Mandated after a few serious incidents where basic buoyancy and stability concepts were forgotten.

SThis is why there are so many stairs to climb on the behind the scenes tours, because from any watertight compartment, to get to their friends cabin next door (but in the next compartment) they may have to climb up 2-3 decks, walk aft 15 feet, and back down 2-3 decks.

Since you mention stairs.....wouldn't the openings for things like stairs and elevators allow the water to overflow the top of the compartments? Or since the top is supposedly already above the waterline is this considered a moot point?

Does that also mean that there are no watertight doors that could be opened/closed below this point?

a couple of technical points

 

Ships sink due to the loss of 'reserve' buoyancy. This is the amount of buoyancy in the hull that is in excess of what is required to keep the vessel afloat. If buoyancy equals displacement the vessel is neutral ... this is what we call a submarine. The can change their buoyancy under control.... Under normal conditions a ship has a great amount of reserve buoyancy and is "stable" Many factors contribute to this buoyancy and stability factor and there are "numbers" that can be assigned to each and are calculated relatively easily. A MAJOR job of the Captain/Master assisted by the engineer is constantly monitoring stability and reserve buoyancy; a primary factor in this is monitoring the 'liquid load'. This is the status of full/empty of every tank in the ship. An empty tank can be worse than a full tank in certain circumstances.

 

Double bottom hulls came into requirement as a way to prevent oil spills. Traditionally many tanks WERE on the bottom of the ship (or extended to the bottom) and since the most common place to get a hole is the bottom there was a high probability of spilling oil. (remember Valdeze) SO the use of double bottoms have been mandated, this began in oil tankers and oil barges but has expanded for obvious reasons. Using a double bottom as a fuel tank is a no no, although use for ballast or water would not be outside the law in some circumstances

 

When a ship is classified as a two compartment ship or a three compartment ship this is not saying breaching any two compartments will sink the ship. It means that if the RIGHT TWO are completely lost, THEN it is game over. Almost always the critical spaces are going to involve the engine rooms. This is how Concordia was doomed. They completely lost their two most critical spaces with no hope of a patch and recover. On many ship just lost of the engineering space alone is not 'the end' but requires a certain group of other spaces that contribute to a loss of buoyancy AND stability. SOLAS has been constantly improving the rules for 'compartmentalization' in passenger vessels making it harder and harder to sink (new construction)

 

Stabile ships roll ..... ships that don't roll tend to be less stable altho that's the ride the paying passenger wants. when approaching a disabled vessel for a SAR incident .... seeing looooonnnngggggg, slooowwwwww, deep rolls from side to side told me we had very serious situation. A vessel that rolled but snapped back upright .... that ship has decent stability

 

just sayin' ..... some of this discussion slid technical and IMO was pointing too some incorrect conclusions.

 

what I have here is some of what I still retain from three times attending Congressionally mandated training for prospective Commanding Officers of Coast Guard Cutters. Mandated after a few serious incidents where basic buoyancy and stability concepts were forgotten.

Couple of corrections, and amplifications:

Yes, a two compartment ship actually means that any two adjacent compartments can flood without losing the ship. And as I said, even if the Concordia had only flooded her two engine rooms she would have stayed afloat, but with 5 adjacent compartments breached, game over.

While you are correct with respect to double bottoms in tankers, not so much for other ships. Cruise ship fuel tanks are almost exclusively in the double bottom. When tankers were single hull, and you put a hole in the bottom (like Valdez), the oil level, which in a full tank is above the waterline, will flow out. Think of two glasses half filled with water (one is the sea, one is the tank), with a hose connecting them at the bottom (the hole in the tank). If you pinch off the hose, nothing flows, of course, so no oil leaks from the tank to the sea. Open the hose, and hold the glasses with the levels equal, and nothing flows. Raise the "tank" glass above the "sea" glass, and water will flow from the tank to the sea.

Now, here we come to double bottom tanks, or in the case of tankers, the case for "mid-deck" tankers. If my tank has a top that is below the water, no oil can flow out of this tank. Why? Pinch your hose closed, and lower the "tank" glass so the level is below the level in the "sea" glass. No open the hose (hole in the tank). Will the water flow from the lower level "tank" glass to the higher level "sea" glass? Nope. The sea water will push into the tank. All you need to do then is to blank off the vents from the tank, trapping any air or fuel from coming out the vents, and you have a "self-sealing" fuel tank. Even tankers, like the one I'm sitting on right now, US flag, have double bottom fuel tanks. OPA90 mandated against double bottom or single hull cargo tanks.

And actually, a partially full tank is worse than a full or empty one, as this tank will experience free surface effect and reduce stability.

Someone been watching The Poseidon Adventure on a continuous loop??????

Since you mention stairs.....wouldn't the openings for things like stairs and elevators allow the water to overflow the top of the compartments? Or since the top is supposedly already above the waterline is this considered a moot point?

 

Does that also mean that there are no watertight doors that could be opened/closed below this point?

The subdivision deck is the top of the watertight compartments. And, yes, since this deck is above the waterline (5-6'), there should not be any downflooding down the stairs unless the ship has too many compartments flooded to bring the subdivision deck to the water (or going down by the bow or stern brings one end of the deck to the water).

There are no watertight hatches in the subdivision deck. Below the subdivision deck, as I said, there are watertight doors between each compartment on each deck. However, these are not the watertight doors that you see in movies about the Navy, or may have seen in the Navy. These are hydraulically actuated sliding doors that physically wedge themselves into watertightness. The doors are allowed to be open when in port, but must be closed when at sea. Generally, normal crew are not authorized to operate these doors, as they can be dangerous if you think they will stop and retract like an elevator door. They won't. NCL had a crewmember, an engineer who should have known better, get his coveralls caught and was literally cut in two. The doors in the engine room remain closed at sea, except when an engineer needs to transit from one compartment to another, and they are authorized to open and close the door immediately. Doors in crew cabin areas are not allowed to be opened at all when at sea. Doors in working areas can be opened, but only after calling the bridge for permission. Frequently, if a galley is having a run on a certain entree, they call down to provisions for more meat, but the meat box is on the other side of a watertight door, so the provisions master has to get permission from the bridge to open the door. The position (open/closed) for all these doors are monitored on a panel on the bridge, and can be remotely closed all at once from the bridge. They have stored hydraulics so will work even without electrical power.