PDA

View Full Version : Does a battleship move in the water when it shoots a full salvo?


swabjocky
February 16, 2002, 10:13 PM
Just a little bit of naval info to let you digest.i know the answer, do you?



swab

Vladimir_Berkov
February 16, 2002, 10:27 PM
I would say no. I am sure that the amount of recoil force generated by the main armament firing is impressive, but likely not enough to make a difference considering the ship's incredible mass.

Also, considering that a full salvo would be fired broadside, the rearward force of the salvo would be dissipated across the entire opposite hull of the ship. The energy required to move the ship side to side is far more than it would take to move the ship forward and backwards considering the same acceleration.

Aion
February 16, 2002, 10:31 PM
Are the screws turning?

- Aion

Coronach
February 16, 2002, 10:35 PM
Yes

-Mike

Scott Conklin
February 16, 2002, 10:36 PM
It depends on what you mean by "move". The force is sufficient to create a wave on the opposite side so the ship has moved, technically. :p

Ed Brunner
February 16, 2002, 10:39 PM
I don't know anything about naval artillery... I doubt that it would move much , but I would guess that it would move. BTW, in the old fashioned artillery, a salvo is fired one round at a time, not all at once.

Crimper-D
February 16, 2002, 11:07 PM
But have seen a Fletcher Class DD (5 5" mounts) let off all it's mounts at once while underway... that sucker rolled and skidded sideways visibly. Of course, Tin Cans displace considerably less mass than a BB, but I'd say the same principles would apply with both.:)

bdhawk
February 16, 2002, 11:12 PM
yep, when they touch off the 16 inchers she moved sideways through the water. projectiles weighed 'bout the same as a compact car and they used over 200# of powder for each shot. there is a video of it on the missouri's websight. www.ussmissouri.com

Mike Irwin
February 16, 2002, 11:41 PM
Yes. Slightly.

Theoretically, a single person simply PUSHING on a ship, even one as large as the Missouri, should be able to move her if she's not hard tied.

C.R.Sam
February 17, 2002, 12:00 AM
Yep

Tamara
February 17, 2002, 12:25 AM
...huge naval rifles is incredible.

The IJN BB Yamato needed some work after it was determined that the blast from her 18" rifles caused serious damage to the rangefinding optics of her small AA and DP mounts.

Aion
February 17, 2002, 12:42 AM
He already said the screws were turning. So the answer is obviously "yes," whether the ship is rolling as a result of recoil or not.

- Aion

TexasVet
February 17, 2002, 12:47 AM
2000lb Projectile X 2000fps = 4,000,000fpe.
4,000,00fpe X 12 guns = 48,000,000 fpe.
48,000,000 / 2000lb per ton = 24000 TONS of recoil energy!
At 60,000 tons per your average big BB, that is 40% of the mass of the ship being imparted. Bet your bippy it's gonna move. About 6 feet, IIRC.

When I was on a 2,200 ton tin can, we figured the impact of a dud 16 incher (assuming it transferred all its energy) would be the equivalent of holding an identical destroyer two feet off the deck, and dropping it.

Mike Irwin
February 17, 2002, 01:14 AM
Uh, TexVet?

I think your calculations are just a little bit off...

By a couple hundred million foot pounds of energy.

Projectile weight for the armor piercing shell was 2,700 pounds.

Multiply that by 7000 grains in a pound, and get 18,900,000 grains projectile weight.

Square the muzzle velocity of 2,500 fps. = 6,250,000.

Multiply weight by MV and get 118,125,000,000,000.

Divide that by the constant 450,400 = 262,266,873 foot pounds of energy.

Divide that by 2,000 to get foot tons of energy = 131,133 foot TONS of energy at the muzzle.

That's for a single gun. Multiply that by 9 for all 9 guns going in unison (which they rarely did because it stressed the ship so much), and you get 1,180,197 foot tons of energy per broadside.

Pretty sobering to think about, eh?

Tam,

You ever wonder where the ship's boats were on Yamato and Musashi?

They had to be stowed in protective recesses under the main deck due to the muzzle blast from the main guns.

herr bean
February 17, 2002, 01:16 AM
Of course it will. If I remember my physics than even shooting a pistol would move it, albeit imperceptably.

C.R.Sam
February 17, 2002, 01:22 AM
Decelerator recoil pad that big?

Sam

Vladimir_Berkov
February 17, 2002, 04:40 AM
First we need to find the force of the guns firing. The weight of one shell is 2,700 pounds. We need to convert this to mass. Weight=mass*acceleration due to gravity. Converting pounds to Newtons and adding gravity we get

12015=mass*9.8

mass=1226kg

Now, force=ma. We need force and acceleration, we have mass.

The length of the 16 gun is 20.32m.

Finalvelocity^2=Initialvelocity^2+(acceleration)(displacement).

(762m/s)^2=0+2a(20.32)

a=14287.5m/s^2

Remember F=ma

So now

F=1226kg*14287.5m/s^2

multiply it by nine guns, and you get

F=157648275 Newtons

Assuming this entire force is transfered to the hull, we can use the same equation to find the acceleration of the hull.

mass of hull=58994285kg

157648275=58994285kg*a

a=2.6722m/s^2

That is not much at all. We also must remember that this is in a frictionless environment. The friction, from both the "suction" action of the side of the hull facing away from the motion, and the resistance of water on the other side, plus the friction produced by the bottom of the hull and of air over the entire portion of the ship above sea level is immense. I have no idea on how to calculate it.

This calculation also disregards any elevation of the guns. If the guns were all fired at a 45 degree angle, the force vectors would result in a force acting both to the side but DOWN as well. Te acceleration side-to-side would be reduced signifigantly.

In addition the guns 48" of rearward recoil movement obviously uses a hydraulic-type system to store much of the recoil energy from the gun barrel. I also have no data on this system and cannot calulate how much it accounts for.

What I would expect is that the ship rotates slightly on its axis if anything, considering the position of the elevated guns relative to the center of mass.


P.S. I was just thinking about this equation, and actually the acceleration number might be wrong as well, as I assumes the shell acceleration as constant, and as reaching max velocity at the exact moment it exits the muzzle of the gun. I also didn't figure in the length of the powder bags, which I do not know.

Art Eatman
February 17, 2002, 05:43 AM
Went on an R&R trip out of Korea to Hong Kong on the USS St. Paul in late 1954. Got to talking gunnery to some navy guys. Aside from, "Yes, a broadside moves the ship sideways.", what I found interesting is that not even a cruiser with "only" 12-inch guns fires straight ahead.

BBs and suchlike angle off course to fire during, say, a stern chase. I don't recall the minimum angle. I was told the reason was to avoid damage to the ship from the recoil.

The St. Paul covered our pullout from Wonsan after the Chosin Reservoir debacle. Part of the outfit I was stationed in had evacuated through there...

(I'll sell my share of Frozen Chosen for a nickel...Okay, do I hear two cents?)

:), Art

Vladimir_Berkov
February 17, 2002, 08:52 AM
These sites, however, state otherwise.

http://www.battleship-newjersey.org/journal/23septpm.html

QUESTION -- I noticed in an aerial photo of the NEW JERSEY firing a broadside that the water next to the ship is roiled. Do the guns cause that or does the ship move sideways after firing a broadside?

The ship does not move. The roiled water is caused by the concussion of the guns firing.

http://www.warships1.com/W-Tech/tech-022.htm

What looks like a side-ways wake is just the water being broiled up by the muzzle blasts. The ship doesn't move an inch or even heel from a broadside.

The guns have a recoil slide of up to 48 inches and the shock is distributed evenly through the turret foundation and the hull structure. The mass of a 57,000 ton ship is just too great for the recoil of the guns to move it. Well, theoretically, a fraction of a millimeter.

But because of the expansive range of the overpressure (muzzle blast), a lot of the rapidly displaced air presses against the bulkheads and decks. Those structures that are not armored actually flex inwards just a bit, thus displacing air quickly inside the ship and causing loose items to fly around. Sort of like having your house sealed up with all windows and vents closed and when you slam the front door quickly the displaced air pops open the kitchen cabinets.

R. A. Landgraff

Art Eatman
February 17, 2002, 09:58 AM
Given the 2,700 lb/projectile, that's roughly 12 tons for a 9-gun broadside. 57,000 tons of ship means roughly 1/5,000th of its mass leaving home rapidly.

Okay, 1/5,000th of the mass of a 190-pound man on an innertube in a pond, with a 10-pound rifle, firing a 280-grain bullet: Roughly equal mass:mass comparison test.

Somebody with a .375, come warmer weather, you mission is...

:), Art

Jager1
February 17, 2002, 10:01 AM
I remember when the New Jersey was shelling positions in Lebanon, there was much ado about her having to stage salvoes to encompass the "rocking effect" and sideways displacement when firing. IIRC, the media claimed it was something along the order of 12 feet with the guns elevated at 45 degrees?

Vladimir_Berkov
February 17, 2002, 10:12 AM
The reason why battleships do not fire multiple turrets at once, is not because of displacement, but because the firings are not perfectly simultanious, the very slight "rocking" effect of the the firing on the lateral axis of the ship screws with the firing computer solutions ever so slightly. However, that would translate to a big error over a long distance.


Guys, think about it logically. If the ship moved 12 feet to the side when the guns fired, people would be knocked off their feet all over the ship. It would be like an earthquake going on inside. Even a relativly small acceration of the ground under a standing human can be very disruptive. Have you ever stepped on one of those moving sidewalks, or even an escalator when you weren't paying attention?

The force of the firing is rapidly transfered to the water from the hull, if moving sideways. That would mean that the movement of 12 feet would require a very quick acceleration and hence a violant disturbance all over the ship.

Double Naught Spy
February 17, 2002, 10:14 AM
Given that the battleship is not securely fixed as a solid object, then one of the basic rules of physics would apply. For every action, there is an opposite and equal reaction.

If there is enough force to rock the ship, then it is being moved in the water.

It doesn't get any more simple than than.

swabjocky
February 17, 2002, 10:33 AM
Well people, the russians did win this gold medal.from what i read on the usnavy internet site,the ship doesnot move.the shock is absorbed by hydrolics.mr vlademir has it right.



swab

Vladimir_Berkov
February 17, 2002, 10:57 AM
Right on! Where is my prize? ;)

Tamara
February 17, 2002, 11:10 AM
Given that the battleship is not securely fixed as a solid object

Yes, except this isn't an "object in a vacuum" physics problem.

As was pointed out above, there's first the hydraulic recoil buffers to spread the shock over time, secondly, the hydrodynamics of the ship when attempting to move laterally just plain suck. As a rough measurement, the Missouri is 860' at the waterline and has a mean draft of 36'. Ignoring the slight curve to her side (slightly concave towards the bows and convex midships), we're talking a "frontal area" of 30,960 square feet that would have to be forced through rather uncompressible water. There's a reason ships are pointed at the bow. ;)

It's pointed out here (http://www.warships1.com/W-Tech/tech-022.htm) that even in a frictionless environment, a full 9-gun broadside only has enough energy to accelerate a 57,000 ton ship to 0.46 feet per second. And trying to force a rather bluff 31,000 square foot steel wall through water is about as far from a frictionless environment as you're going to find.

Now, with an earlier battleship, such as the Royal Navy's WWI-vintage Agincourt, your talking a ship that weighs 30,250 tons, is 660' at the waterline, with a mean draft of 26.5' (rough area: 17,490 square feet), yet packed a broadside of 14 (!) 12" guns. Those ships might have moved a more noticeable distance.

BTW, I came into this thread thinking "of course they move!", but thanks to the links and the essays there, I'm now pretty convinced they don't (at least not very much); the numbers just don't add up.

Tamara
February 17, 2002, 11:22 AM
...we should note that 138 years ago today, the cracker U-boat scored its' first and only victory.

Regardless of which side of the Mason Dixon Line you live on, take a moment to remember those gallant but doomed young men. It took chutzpah to crew that boat after it had alread sunk twice.

40ozflatfoot
February 17, 2002, 01:31 PM
As a boy growing up in a Navy town full of WWI and Korean War vets, both Navy and Marnie Corps, I heard many stories.

One of them I heard over and over from vets that were stationed on board battleships that had seen service against the Japanese. They told of standing orders that were strictly enforced, and what happened to those spaces that were not prepared for primary gun ops...the 16 inchers.

Everything had to be stowed as if for a severe storm at sea, and no one, not even Marine sentries, were permitted anywhere on the main decks during operations. The reasons were that, every time the guns fired, which was almost broadside during shore bombardment preparatory to amphib landings, the ship both rolled and moved sideways from the recoil. If a nine gun salvo was ordered, the ship rolled so far that the main deck opposite the side over which the guns were firing became submerged under more than six feet of water. The ship itself was also moved abeam so far that the screws and rudder had to be used to put the ship back on station, or her firing would jeapordize the surrounding escort vessels.

I remember hearing some stories of what happened in living quarters and mess decks that were not prepared for these ops. Some personal belongings were never found again, and the cleanup in the mess decks sometimes took so long that they were still picking up utensils, shakers, and so on until the next day.

One story I remember was about a cook that had seen duty on a carrier, but not on a battlewagon. He decided that the orders were a bunch of hogwash, so he ordered everything laid out for the noon meal as if they were under normal conditions. They said that, after a long talk with the captain, it never happened again.

Yes, they do move sideways, and they do roll in the water.

Tamara
February 17, 2002, 01:52 PM
With all due respect, I believe you may have heard a "sea story", embellished for its' effect on a young landlubber. (Hey, up until I started reseaching it this morning, I believed it, too. :o )

Iowa's port rail appears to be somewhat less than awash, here.

Check this link (http://www.warships1.com/Weapons/WNUS_16-50_mk7.htm) for details.

Mike Irwin
February 17, 2002, 03:03 PM
OK, 40oz, I think you've just told the BEST sea story of all time. :)

Also one that is patently untrue.

The movement and roll that we're talking about is, really, barely perceptible, certainly NOT what was recounted to you.

My other concern is the concept of the recoil slides. Yes, there are, and have to be, very effective recoil absorption mechanisms for these guns.

But I'm not sure that they can totally negate the backward thrust of the guns to the point where it is totally cancelled out. I'm not at all sure that's possible.

I think we're also getting wrapped around the axel here over what qualifies as "sideways movement." Even if the ship only moves a millimeter, it's still sideways movement caused by the firing of the guns.

And finally, Tam, just for you...

http://www.warships1.com/BRbb09_Agincourt-LD1.jpg

Azrael256
February 17, 2002, 03:11 PM
According to a good friend of mine, Lt. Col. Stone, the New Jersey, at least, does slide sideways after firing a full broadside. He observed this from an RC-135 flying off the coast of Vietnam. I don't recall just how high the aircraft was flying, and I suppose it could be entirely apocryphal, but according to him, you could see a puff of smoke from the guns, and the ship would recoil from the guns, and then slide back some distance. Obviously at altitude it is impossible to observe exact distances, but just moving a ship like that is pretty impressive.

40ozflatfoot
February 17, 2002, 08:14 PM
Tamara,

I think I most assuredly heard some sea stories in those days, especially embellished for a small boy's entertainment. To be honest, I never gave it any thought until I experienced it myself, to a smaller degree, of course, on board the USS Galveston during exercises off the California coast in the early 1960s. The ship had two 6"/47 turrets with three guns each, and three 5"/38 DP mounts, with a SAM battery aft. At one point during the two week exercises, we were required to simulate shore bombardment with the "big guns." At one point, the guns were firing with just the right timing that they got the ship rocking and rolling so much that the captain had to order a check fire to allow the ship to settle.

When firing under these circumstances, the ship stops all engines, a condition known as "underway with no way on." I may have misspelled it. This gives the most stable gun platform possible. Of course, the position has to be regained with rudder and screws from time to time, but not after every salvo, since the stable element (i.e. computer) can be adjusted to compensate for the change due to recoil.

During my first hitch, I was a fire control technician. I cut my teeth on 5"/38 guns on an old WWII 2250 can, the USS Cowell, long since relegated to the scrap heap.

Mike, thanks for the compliment, but they weren't my stories. I just passed 'em on.

Gotta quit for now. Time to go to work. Maybe more later.

Vladimir_Berkov
February 17, 2002, 08:53 PM
But I'm not sure that they can totally negate the backward thrust of the guns to the point where it is totally cancelled out. I'm not at all sure that's possible.

I think another aspect we are forgetting is that even though a battleship is very solid, it is not completely so. All of the energy of recoil is not translated into a sideways vector force. The hull itself is going to absorb lots of energy before a sideways force is even exerted.

ojibweindian
February 17, 2002, 09:01 PM
Reading this post reminds me of the tricks we used to play on personel reporting to the boat from boot camp. Ever see someone spend hours trying to get a bucket of steam:)?

swabjocky
February 17, 2002, 09:47 PM
You ruined it for me,iam still looking for a lefthanded monkey wrench.

swab

Kevlarman
February 18, 2002, 01:12 AM
Pardon my ignorance, but what are "ship screws?":confused:

C.R.Sam
February 18, 2002, 02:01 AM
Screws = propellers.

Or maby seaborn cops.

Sam

skeeter
February 18, 2002, 02:27 AM
Vad Seems like impulse would be a factor here also. Moving 12 feet over time is not as disruptive as moving over a very short moment of time. And this movement would be initially a rotational movement about the axis of the ship.
On the same subject- when the mini-cannon on the Warthog is fired you can see and feel a drop in air speed.
I wonder how far I can go in my canone and a couple of cans of .50bmg's

Fred Hansen
February 18, 2002, 02:31 AM
You ruined it for me,iam still looking for a lefthanded monkey wrench. Swab,

Those items are fairly scarce, that's why they are secured in a special compartment inside of all mail-bouys. They are usually between the skyhooks and the metric crescent wrenches.:D :D :D

1goodshot
February 18, 2002, 08:55 AM
For every action the is a equal and opposite reaction

Aion
February 18, 2002, 10:34 AM
They are usually between the skyhooks and the metric crescent wrenches.
When I was a lineman, we used to do this kind of stuff to new guys all the time: skyhooks, eagle-eyes (means to look and see if everything appears OK), bring me 20' of shoreline, etc.

I heard about a new helper being sent for a bucket of volts. He went to the storeroom, and they played along, telling him he needed a stock slip signed by the foreman. Foreman told him it was a big ticket item and had to be signed by the District Manager. "Son," said the DM, "I want you to point to the man who sent you to me." Gulp... end of prank.

- Aion

Bulldog44
February 18, 2002, 10:37 AM
Sir Isaac Newton answered this question ahead of time. For every action, there is an equal and opposite reaction.

40ozflatfoot
February 18, 2002, 11:25 AM
Of the same kind at the same time.

Very important.

Tamara
February 18, 2002, 11:50 AM
For every action, there is an equal and opposite reaction.

Yes, you are right. You can see that people have done the Newtonian equations, there.

The same force that accelerates 12.1 tons of 16" shells to their muzzle velocity accelerates the 57,000ton ship to .46 feet-per-second (in a frictionless environment with the guns @ 0* elevation).

Epure sil muovo, just not very much. ;)

striderteen
February 18, 2002, 11:57 AM
Exactly.

Tamara
February 18, 2002, 12:06 PM
...a coil of flight line and a can of prop wash, please. ;)

striderteen
February 18, 2002, 12:16 PM
Hehehe.

4V50 Gary
February 18, 2002, 12:30 PM
On the Italian Littorio class BB of WW II (9 x 15" guns in triple turrets), the guns on a single turret were not fired simultaneously because the blast caused too much dispersion of the group. There was a slight delay between the two outer guns and the center gun.

Neither of the Yamato class BB of WW II ever fired a broadside. While their turrets were certainly capable of turning 90 degrees port/starboard, the ship was not designed for the resultant blast damage and stress.

The only "cruisers" the USN had with 12" guns is the Alaska (Alaska & Guam) class super heavy cruisers. While they would be rated as battlecruisers by other navies (being classified as CB - large cruisers), they were not called as such by the USN. They were very much "white elephants" built to satisfy Roosevelt's demand for ships to counter the German Scharnhorst class and the imagined Japanese super heavy cruisers/battle cruisers (planned, but never built). In a sense, they were very much a cruiser unfettered by pre-war limitations. Very handsome ships.

BTW, anybody in the SF Bay Area should stop by Suisun Bay. The battleship Iowa is part of the Reserve (ahem, "mothball") Fleet. I saw it when I passed by on Amtrack.

thisaway
February 18, 2002, 09:10 PM
What I'm wondering is if anyone will ever come up with a tougher-sounding name for a battleship than that which the British named the original "modern" battleship:

DREADNOUGHT


It just SOUNDS powerful! :eek:

Mk VII
February 20, 2002, 08:26 AM
this shot from the New Jersey's 1968 cruise shows the flash from No.1 turret developing, with two projectiles visible in the top left-hand corner of the picture. In a nominal broadside there is a 0.06 second delay between each gun in the turret firing to avoid aerodynamic interference between the projectiles

Mk VII
February 20, 2002, 08:32 AM
in this shot taken a moment later the blast pressure wave is developing on the water's surface. It is this, more than anything else, which gives the impression that the ship has moved sideways. But nine 1900 lb shells cannot make any appeciable movement of a 57,000 ton battleship

Mk VII
February 20, 2002, 08:34 AM
forgot to attach the file

4V50 Gary
February 20, 2002, 10:40 AM
Thank you MK VII. Are you a member of the INRO (International Naval Research Organization)?

ryucasta
February 20, 2002, 11:50 AM
Check out this site :eek:

ryucasta
February 20, 2002, 11:51 AM
http://www.combinedfleet.com/baddest.htm

Try again

Mk VII
February 20, 2002, 12:09 PM
"are you a member of INRO?"

no, I'm just an occasionally interested amateur. I do remember boarding the IOWA when she docked in Portsmouth in 1986. Still have some colour slides I took. You can see a Marine with an M-16 up in the spotting top, something nobody noticed at the time.

Cougar
February 23, 2002, 07:35 PM
of the firing of the main battery on the Iowas was so that the pressure wave (shockwave) from each projectile would not interfere with each other. With the .05 second delay between each gun barrel firing, the aerodynamic interference of each projectile was negated. There actulally is a preset sequence for the 'simultaneous' firing. IIRC, it is C-R-L. Now you're gonna make me go look it up again, aren't you?!

Also, reports that I have seen (read) about the various batteries on the Iowas, the crew found the blast pressure from the 5"/38s as more viscous than the main 16" guns.

And NO! The ship does not move on firing!