USS Fitzgerald incident

[Samez]

A freighter at 17 knots brings a lot of kinetic energy - a wonder they managed to do a 90° turn directly after the impact while slowing down about 30-50% within a mile - after that reaccelerating to cruise speed just to slow down again for the next 5 miles. It seems like the auto pilot definitely needs an emergency auto shutdown/ slowdown mode.

 

[Thorgalaeg]

Probably the 90° turn was not after the impact but along it, it is consistent with where the damage is located in both ships. It is a small freighter anyway, only 30,000 tons while the destroyer is almost 10,000 such collision could deviate the freighter abruptly from its original course.

 

[Timsup2nothin]

Probably the 90° turn was not after the impact but along it, it is consistent with where the damage is located in both ships. It is a small freighter anyway, only 30,000 tons while the destroyer is almost 10,000 such collision could deviate the freighter abruptly from its original course.

Agreed.

This incident definitely reminds me how glad I was to have served on a submarine. When submarines bump into container ships the submarine wins.

 

[timtofly]

Agreed.

This incident definitely reminds me how glad I was to have served on a submarine. When submarines bump into container ships the submarine wins.

If a freighter broadsided a submarine, would it not slice it in half?

 

[Timsup2nothin]

If a freighter broadsided a submarine, would it not slice it in half?

Based on the USS George Washington, apparently not.

 

[Kozmos]

Submarines are built to withstand great underwater pressures are they not? I'd give them the advantage every time.

 

[Thorgalaeg]

In ww2 surface ships would try and ram any enemy submarine at sight. Also the USS George Washington collided with a ship considerably smaller than itself. As a rule of thumb i would put my money on the bigger ship, and at similar size on the one impacting head-on (given both vessels are made of the same material, otherwise steel always wins!)

 

[Kozmos]

But subs were a pretty immature technology back then, I'd imagine a modern day sub, especially a SSBN say can take a bit of a beating.

 

[Timsup2nothin]

In ww2 surface ships would try and ram any enemy submarine at sight. Also the USS George Washington collided with a ship considerably smaller than itself. As a rule of thumb i would put my money on the bigger ship, and at similar size on the one impacting head-on (given both vessels are made of the same material, otherwise steel always wins!)

WW2 submarines were basically surface ships with the ability to submerge, briefly and not very far. Basically just a really clever form of camouflage. A modern submarine is an entirely different beast. And no, they aren't made out of the same thing. They are made out of steel, but not the same kind of steel. Take a hammer made of good tempered tool steel to your basic soup can and see how much damage the hammer suffers.

I will grant that a direct strike amidships by the prow of a heavy freighter could be bad news, but I'd wager even odds it would still just tear off the superstructure and push the pressure hull out of the way.

 

[Thorgalaeg]

Possibly. Submarine pressure hulls must be much stronger than normal. OTOH I am not a naval engineer or anything, but have some experience with leisure boats, and usually the bigger the ship the thicker the hull, be it steel or fiberglass. I wonder if the same rule applies to large comercial ships, in such case the hull of an ultra large freighter or tanker must be thicker than a ww2 bunker.

 

[Timsup2nothin]

Possibly. Submarine pressure hulls must be much stronger than normal. OTOH I am not a naval engineer or anything, but have some experience with leisure boats, and usually the bigger the ship the thicker the hull, be it steel or fiberglass. I wonder if the same rule applies to large commercial ships, in such case the hull of an ultra large freighter or tanker must be thicker than a ww2 bunker.

Well, the hull of the Titanic was about three quarter inch plate, and typical ship's hull plate is made from a pretty ordinary steel so yield strength around 30K psi. Pressure hull of a submarine is almost three times the thickness of HY-80 (yield strength 80K psi). So more than twice the thickness and more than twice the strength of material. Angles matter, point of impact matters, but you are starting from one plate being more than four times stronger than the other, so if other factors aren't overwhelmingly stacked against the submarine it will be a messy situation for the freighter.

We always operated from the assumption that if we got in a collision our only fatal outcome would be if we got tangled in the wreckage and dragged below test depth, or ruptured the external ballast tanks so they wouldn't hold air. The San Fransisco hit a mountain while running at flank speed and didn't break the pressure hull, so I really don't think a freighter has much of a chance.

 

[Kozmos]

A bit off-topic but you ever played any of the sub-sim games Tim?

 

[FriendlyFire]

Agreed.
This incident definitely reminds me how glad I was to have served on a submarine. When submarines bump into container ships the submarine wins.

Wasnt there in incident when a Soviet sub didnt check it blind spot when surfacing and then surfaced right in front of a US cruiser which rolled over the sub ?
IIRC the soviet sub was total lose but most of the crew escaped alive if somewhat embrassesd.

 

[Timsup2nothin]

A bit off-topic but you ever played any of the sub-sim games Tim?

Yes, but I can't say I particularly like them. Accelerating naval warfare to fit it into a game timeframe turns it into a flight simulator with weird planes.

Wasnt there in incident when a Soviet sub didnt check it blind spot when surfacing and then surfaced right in front of a US cruiser which rolled over the sub ?
IIRC the soviet sub was total lose but most of the crew escaped alive if somewhat embrassesd.

I know there was one that bounced off the Kitty Hawk, which is an aircraft carrier. They weren't surfacing unaware though; just playing cold war games. Stories of "ran into something, must have been a fish" didn't happen often, but they were not uncommon enough back in the day. Both sides played the brinksmanship game pretty hard. My boat missed a soviet sub by an estimated hundred yards or less one time...and we didn't know it until after the pass. Based on their complete lack of reaction we figured they never knew it at all.

 

[Ajidica]

@Timsup2nothin question about submarine pressure hulls. Do they extend into the conning tower/sail? If so, doesn't that damage the integrity of the pressure hull as it is no longer a perfect tube?


EDIT: As long as we are on the subject of sub sims, anyone have any thoughts on this Cold War themed one that came out recently, Cold Waters?
http://store.steampowered.com/app/541210/Cold_Waters/

 

[Kozmos]

Yes, but I can't say I particularly like them. Accelerating naval warfare to fit it into a game timeframe turns it into a flight simulator with weird planes.

I see your point. All I played was Silent Hunter 3, where it felt less pronounced due to being a U-boat sim. You also had some speed modifiers until you sighted a contact. I remember it being a lot of fun although I was pretty terrible at it with the higher realism settings.

 

[Timsup2nothin]

@Timsup2nothin question about submarine pressure hulls. Do they extend into the conning tower/sail? If so, doesn't that damage the integrity of the pressure hull as it is no longer a perfect tube?

That's all superstructure, though the access passage inside the sail is its own pressure container...sort of like an air lock. Anywhere there's a hatch on top of the boat it goes into a little pressure tight bubble with another hatch to get into the boat proper.

 

[FriendlyFire]

What was the food like in the Sub ?
I watch a UK sub and they had reasonable food for 30 days, thats when the eggs and fresh vegetables were all gone, next 30 days were all can and preserved foods before they had to come back to resupply
The storage room were stacked to the roof with a tiny access space for the cook. They had a fry up for every breakfast (fatty english breakfast) and most of the crews were overweight

Everything was so, claustrophobic and for the crews meant no space to exercise, dark environment, with few luxuries available
So the cook provided comfort foods, especially fired foods to keep up morale.

 

[Thorgalaeg]

And no, they aren't made out of the same thing. They are made out of steel, but not the same kind of steel. Take a hammer made of good tempered tool steel to your basic soup can and see how much damage the hammer suffers.

Been researching a bit about ship building and found that moder large freighters hulls are made of YP390 and YP460 steel, which stands for 460 mPa yield, about 66K psi, (very close to HY80) with thickness from 50 to 90mm. Dont know what the thickness of a pressure hull would be though. In any case, the can/hammer analogy does not seem of much use here.

@Ajidica, i purchased Cold Water yesterday. Will briefly comment if i have time to test it.

 

[r16]

even nuclear subs gotta have snorkels . What happens if it gets broken ? Assume it has valves on the bottom , too . Likewise with the periscobes ?