Battleships move sideways on broadsides?


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ZekeLuvs1911
February 26, 2003, 01:18 AM
I've seen this question brought several times and I just had to post the answer again. :D
Moderators, it is gun related...........;)

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



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To calculate the velocity of the USS New Jersey moving sideways, what you need to consider is conservation of momentum. A 16" Mark 8 APC shell weighs 2,700 lbs. and the muzzle velocity when fired is 2,500 feet per second (new gun). The USS New Jersey weighs about 58,000 tons fully loaded (for ships, a ton is 2,240 lbs.). All weights must be divided by 32.17 to convert them to mass.

If the battleship were standing on ice, then:

Mass of broadside * Velocity of broadside = Mass of ship * Velocity of ship

9 * (2,700 / 32.17) * 2,500 = 58,000 * (2,240 / 32.17) * Velocity of ship

Solving for the ship's velocity:

Velocity of ship = [9 * (2,700 / 32.17) * 2,500] / [58,000 * (2,240 / 32.17)] = 0.46 feet per second

So, ship's velocity would be about 6 inches per second, ON ICE.

This analysis excludes effects such as (1) roll of the ship, (2) elevation of the guns (3) offset of the line of action of the shell from the centre of gravity of the ship and (4) forces imposed by the water on the ship. These are variously significant, and will all tend to reduce the velocity calculated above.

Greg Locock



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I need to point out that in Greg's masterful analysis he assumes that the guns are at zero degrees elevation, that is, the guns are pointed directly at the horizon. In actuality, they are almost never fired at this elevation as it would mean that the shells would only go a short distance before they struck the water. At a higher, more realistic elevation, the force of the broadside would also have to be multiplied by the cosign of the angle of elevation. This means that the horizontal velocity imparted to the ship would be even less than the numbers calculated above.

Tony DiGiulian

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Art Eatman
February 26, 2003, 01:41 AM
Yeah, well, the cosine of 25 degrees is 0.90, so you gotta be shooting at a pretty good upward angle before it's significant. :) That's why uphill/downhill isn't much of a range-estimation factor in most hunting shots.

The big problem is persuading folks that "little motion" isn't the same as "no motion".

:), Art

Zander
February 26, 2003, 01:47 AM
This means that the horizontal velocity imparted to the ship would be even less than the numbers calculated above.Which assumes a non-reactive medium...and salt water isn't.

Simple physics...there is indeed a lateral movement, something the fire-control computers would take into account.

The formula is a constant; it's the same for 16" naval rifles as it is for a three-pound 1911A1 being fired from a human platform. Take the variables into account and report accordingly.

Tamara
February 26, 2003, 01:51 AM
Which assumes a non-reactive medium...and salt water isn't.

It's hardly a frictionless environment, either. As a matter of fact, I can't imagine a much better hydraulic brake than trying to push an 800'x30' steel wall through the water. ;)

Blackhawk
February 26, 2003, 02:00 AM
A 16" Mark 8 APC shell weighs 2,700 lbs. and the muzzle velocity when fired is 2,500 feet per second (new gun). Hmmm.... A 16 APC... Anybody sell a CCW holster for that pistola? :rolleyes:

UnknownSailor
February 26, 2003, 02:35 AM
I asked this question of a BB gunners mate, and he said hell no.

Zander
February 26, 2003, 02:48 AM
It's hardly a frictionless environment, either. -- TamaraAgreed...but doesn't change my point.

Let's assume a projectile weighing a ton fired at 2700 fps...

The formula for muzzle energy is:

(MVxMV ÷ 7000) ÷ 64.32 x BW

MV = muzzle velocity

BW = bullet weight in grains [7000 grains to the pound]

What does your calculator spit out?

Three sixteen-inchers fired simultaneously aren't going to change the rotation of the earth, but they are darn sure going to affect the attitude and course of a battleship.

Simple physics...

Tamara
February 26, 2003, 03:01 AM
No need to drag out my calculator, the equation's in the first post of the thread. In a frictionless environment, the ship would be accelerated to .46 fps. Figure the resistance of incompressible water into the equation, and that acceleration is reduced to "not worth measuring". ;)

tex_n_cal
February 26, 2003, 03:16 AM
Not worth measuring, and besides that, battleships have been decommisioned anyway:(

Lancel
February 26, 2003, 03:42 AM
Yeh, well the recoil might add up to nothin'; but what about the knock down power.:D

Larry

ZekeLuvs1911
February 26, 2003, 03:50 AM
Actually, the New Jersey, Missouri and Wisconsin have been converted to floating museums. The Iowa is currently in inactive status with her repair materials for her #2 turret stored inside. She can come back if notice is given.

Here's a link for interesting info:
http://www.warships1.com/

mons meg
February 26, 2003, 05:38 AM
There was a show in these big boats on TLC recently, I want to say they quoted an operational cost of $1 million per *day* for one Iowa class. Easier to mothball them and then bring them back later if they need...at a billion or so a year to keep all 4 operational.

Neil Casper
February 26, 2003, 05:57 AM
BOATS!!!
They are ships my friend. And if you don't get the terminolgy right I'm going to throw you through that little round window over there!;)

redneck2
February 26, 2003, 07:10 AM
but how well do they perform on goats???

I'm not gonna believe any of it until I see a goat test.

griz
February 26, 2003, 07:48 AM
We need an icon for how many angels can dance on the head of a pin ;)

ZekeLuvs1911
February 26, 2003, 08:01 AM
My, my !!!! Aren't we all uppity today? :D

Red, they did do a goat test......that's why you see no goat.....:p

Double Naught Spy
February 26, 2003, 10:03 AM
As with the point brought up here and that I have seen elsewhere, it appears illogical that the guns could generate enough force to move such a big ship, right?

As such, it would make sense that I could not push a 55 ft ocean-going fishing boat loaded down with gear and people for an extended trip away from the dock with one arm, but I did. I could never do that on dry land, but water offers a unqiue environment for the drill. Similarly, I watched a 60 lb. little kid push a pickup truck (GMC) several feet with his daddy behind the wheel and the vehicle in neutral. It would appear that a 60 lb kid could not generate enough force to move such a heavy object (and his daddy wasn't exactly lean, either), but he did. Amazing.

BigG
February 26, 2003, 10:04 AM
The question appears to be moot anyway. I seem to remember that one of my old navy buddies said they have an interlock system where they can't fire all nine at once. I think one gun per turret at a time was what he said. :confused:

Tamara
February 26, 2003, 10:21 AM
They can fire full broadsides, but I think individual tubes next to eack other are staggered fractions of a second apart so that the shockwave from the muzzleblast and wake turbulence from the shell don't affact the trajectory of the nxt tube over...

BigG
February 26, 2003, 10:25 AM
Thanks, Tam! I knew there was some lil thang that stopped em from all goin off at oncet. :cool:

griz
February 26, 2003, 10:58 AM
Here is a picture just to stir the pot a bit:
http://battleshipnewjersey.org/photoGallery/?fa=viewPhoto&photoId=45

BigG
February 26, 2003, 11:06 AM
Flashhider ain't workin too well. :neener:

Leatherneck
February 26, 2003, 12:08 PM
I controlled a few fire missions from New Jersey in Vietnam. They were quite accurate at about fifteen miles range, adjusting fire as I called for it, firing for effect (!) at bunkers. I ran out of fuel before they ran out of ammo. :D

TC
TFL Survivor

Ullr
February 26, 2003, 12:58 PM
griz,

Nice! We ought to start dropping full-color leaflets of that kind of thing (Army artillery, Air Force cruise missile strikes) all over Iraq. Maybe give a few of those "hardened veterans" something to think about...
:evil:

mons meg
February 26, 2003, 01:49 PM
BOATS!!!

Heh...Neil, I was in the USMC. I wodnered if that use of the word would attract some attention.

Leatherneck: I was a fire controlman during Desert Storm. One thing I envied the Navy....they had the biggest guns. :mad:

Although in restrospect, I guess they don't make a truck big enough to tow a 16" piece.

Greybeard
February 26, 2003, 02:12 PM
It seem that lots of us are snowed/iced inside today with not a lot to do ... ;)

Blackhawk
February 26, 2003, 02:28 PM
Leatherneck, I had three interfaces with the NJ during those months.

1) Before missions, we'd be briefed where it was when it was in our AO.

2) The AF controllers would warn me about the areas it was operating in real time if they saw me heading toward them.

3) Listening to its guns firing and the shells exploding when it was working over the area near where we were based on the coast.

Never did have a good idea of how effective its Naval fire was, but it was a "neat" aspect of being there.

Blackhawk
February 26, 2003, 02:30 PM
It seem that lots of us are snowed/iced inside today with not a lot to do ... And that's saying a lot considering that you're in Texas! :D

braindead0
February 26, 2003, 02:43 PM
Forget about it, Zeno already proved that motion is impossible anyway :D

4v50 Gary
February 26, 2003, 03:01 PM
Without referencing my books, I think the Iowa class is over 850 feet long (maybe about 875) and about 98 feet wide - just narrow enough to squeeze through the canal.

Tamara
February 26, 2003, 03:32 PM
Question: (http://ussnewjersey.com/voyl_12b.htm) 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?

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

:D

bountyhunter
February 26, 2003, 03:35 PM
"The big problem is persuading folks that "little motion" isn't the same as "no motion"."

EXACTLY: I remember taking part in the thread at the 1911 forum where the starter asked: When the battleships fire their guns, do they move in the water: The answer I gave (which is correct) is absolutely YES.

The eventual outcome of the thread was that I was branded a moron and subjected to a littany of ridicule. One noteworthy imbecile told me that I didn't understand that the recoil absorbers convert the recoil energy to heat so it has no effect on the ship. In fact, if the recoil absorbers are bolted to the ship, they are part of it. The assembly still has to "push back" against the recoil force of the gun. Since they are connected to the ship, the energy is still applied to it.

The truth is, the ship absolutely must move in response to the gun firing as required by Newton's law: for every action there must be a reaction. It is entirely possible that because of the ship's enormous mass, the movement of the ship is small enough that people on board don't notice it. However, sensitive instruments like the ones used to detect earth movement would see it easily.

Another point is what type of movement? If the "line of force" of the guns recoil (as determined by where it is pointed) is above the center of mass of the ship, it generates both a lateral acceleration as well as a rotational torque. What provides the "resistance force" against these forces? The water. Put your hand in water without moving and you feel nothing (forces equal on all surfaces). Move your hand through the water and you feel it "pushing" on your hand as the water tries to remain at rest. The enormous surface of the ships hull means it doe not have to move much to generate the required resistance force to balance out the recoil from the gun.... but it does have to move.

Ebbtide
February 26, 2003, 03:55 PM
Bountyhunter,

I read all that mess on the 1911forum. I don't think you are a moron.

However, if I bolt 10/22 to the side of the battleship and fire it, should the battleship move according to newton's law. Is it not possible that the ship absorbs all of the recoil, and therefore does not move (changes it position on the earth) at all?

Just wondering and trying to make all this math stuff make sence.

BigG
February 26, 2003, 03:58 PM
You are correct that some movement has to occur but it would be on the magnitude of a pissant vs a boxcar when you compare the projo and ejecta with the mass of a USS NJ. :neener: it is so little it is virtually nil. Not only that, but a ship is continuously moving because the sea is continuously moving. If the movements are synched just right they may cancel each other out. You are perhaps assuming the ship is in a vacuum sealed chamber with no forces working on it except the recoil? :confused:

citizen
February 26, 2003, 04:17 PM
So, the ship may move; minutely.

BFD

Can anyone post what the TARGETS look like???
Do they move?:rolleyes:

gun-fucious
February 26, 2003, 04:39 PM
being one inclined towards the duct tape and string system of proof

it would seem a military GPS on the ship might tell you if you moved

Drjones
February 26, 2003, 04:43 PM
Can you suppress that puppy?

:D

How accurate are they? (16 inchers, that is...)

Thumper
February 26, 2003, 05:18 PM
Deja vu all over again.

http://www.thefiringline.com/forums/showthread.php?s=&threadid=102622&highlight=battleships+sideways

Robby from Long Island
February 26, 2003, 05:24 PM
It seems to me I read somewhere that at a range of 20 miles they could put a 16" shell within 100 yards of their target.

Now that's shooting.:cool:

bountyhunter
February 26, 2003, 05:52 PM
"You are correct that some movement has to occur but it would be on the magnitude of a pissant vs a boxcar when you compare the projo and ejecta with the mass of a USS NJ. it is so little it is virtually nil. Not only that, but a ship is continuously moving because the sea is continuously moving. If the movements are synched just right they may cancel each other out. You are perhaps assuming the ship is in a vacuum sealed chamber with no forces working on it except the recoil? "

No, I'm just not in favor of teaching bad physics or things that are not true. It is a fact the forces in the example are tiny, but sometimes tiny forces are important. In fact, they built the universe we live in. The stars where the elements which make us up were born condensed from scattered clouds of hydrogen molecules whose garvity acting on each other drew them slowly together over billions of years.

It's important to understand a principle: that any force has an equal (and opposite) reactive force. It may be silly to think that firing a pistol affects the speed the earth rotates, but it does. We just can't measure it.

Zander
February 26, 2003, 05:59 PM
Figure the resistance of incompressible water into the equation, and that acceleration is reduced to "not worth measuring". I suppose that would be so if you don't care where those 2700 lb. shells are going to land when you fire the next string.

We're talking about 787 million foot-lbs. of energy from one broadside. Seem impossible?

Per shell...

(2500x2500/7000) / 64.32 x (2700x7000) = 262,360,075 fpe

If you doubt the formula, here's a more believable example:

For Cor-Bon's lightest .40Auto load...

(1300x1300/7000) / 64.32 x (135) = 506 fpe

Would hundreds of millions of pounds of muzzle energy affect a battleship of 58,000 tons of displacement? Of course it would...enough so that, as mentioned before, the fire-control computers would have to take it into account.

...if I bolt 10/22 to the side of the battleship and fire it, should the battleship move according to newton's law. -- ehenzWell, the simple answer is 'yes', but how about a more realistic example?

Have a man sit in a canoe [combined weight of 250 lbs., let's say] floating on a pond and fire a .44Mag carbine broadside three times as quickly as he can. Will the canoe move sideways?

Tamara
February 26, 2003, 06:18 PM
787,000,000 ft/lbs, acting on more than 100,000,000 lbs of ship, dissipated through recoil buffers, firing at an angle, and having its horizontal motion slowed by trying to force a 24,000+ sq/ft steel wall through water.

Your argument is convincing, Zander, but the arguments of, you know, actual battleship captains and gunnery officers is even more convincing yet. ;)

Zander
February 26, 2003, 07:50 PM
You guys have been cheating...you're just pulling stuff from a previous thread on TFL. :mad: C'mon! :)

...but the arguments of, you know, actual battleship captains and gunnery officers is even more convincing yet. -- Well, now that I have had the chance to review the TFL thread, I'd say that there was no clear consensus.

At any rate, there's no arguing with the numbers or the physics; Take my man/canoe/pond/carbine example and let's be a little more precise by scaling down the weight and reaction to FPE (ME) in our battleship example.

If the assumption is 58,000 tons at a displacement weight of 2,240 lbs./ton, we're looking at an FPE:weight ratio of a little more than 6:1.

Let's change the weight of the canoe and passenger to the weight of a rowboat [deeper draft] and three people instead of one. How 'bout a total weight of 1,000 pounds?

Using our ratio, let's have a Barrett 82A1 .50BMG semi-auto mounted to the center seat of said rowboat. We'll remove the muzzle brake and adjust the load/velocity of the Barrett to yield a ME of 6,000 ft.lbs. or so. With me?

Now, have one of the three on-board row the boat across the pond [or, what the heck, fire up a 5-horsepower Evinrude] until a decent velocity is attained and have someone else trigger the Barrett, pointed starboard at 90º to the rowboat's heading, at an elevation of...oh, 30º or thereabouts.

Is there any movement to port? Will the occupants notice that the Barrett has been fired? :)

BigG
February 26, 2003, 08:10 PM
Seem impossible? Does that one come in scandium yet? :neener:

Tamara
February 26, 2003, 08:11 PM
Some physicist will be along shortly, no doubt, to tell us that your experiment is off due to some problems with linear scaling of the forces involved.

Nevertheless, I'm game to try. Especially if beer is somehow involved.

"Hey, y'all! Watch this!" :D

Zander
February 26, 2003, 08:25 PM
Some physicist will be along shortly, no doubt, to tell us that your experiment is off due to some problems with linear scaling of the forces involved.Ah...then the laws of physics aren't really immutable?

Nevertheless, I'm game to try. Especially if beer is somehow involved.As long as all participants are really good swimmers. :)

"Hey, y'all! Watch this!"LOL! If only you had a sense of humor...

BigG
February 26, 2003, 08:41 PM
How many grains of powder to they use to launch one of those 2700 pound payloads?

Tamara
February 26, 2003, 08:56 PM
Hey, I'm not kidding...

There's a lake in my front yard, a johnboat in the shed, a boat ramp fifty yards down the road, and beer in the fridge; I'm pretty sure I can scare up the extra passenger (lendringser's usually up for loony stunts in the name of science).

You gotta bring the Barrett, though... ;) :D

Drjones
February 26, 2003, 09:05 PM
"Hey, y'all! Watch this!"

No, no, NO, Tam!!!

The proper way is:

"Hold muh beer and watch this!"

(Usually the "infamous" last words... :rolleyes: :D )

:neener:

Tamara
February 26, 2003, 09:10 PM
The proper way is:

I live in Tennessee, you live in California; you're just gonna have to trust me on this 'un, h'mkay? ;) :D

Zander
February 26, 2003, 09:14 PM
You gotta bring the Barrett, though...Oh, please...

Just dip into that bottomless firearms-acquisition fund of yours.

I do have one request...can we wait until the sun actually shines on the Free Republic of Tennessee again? <sigh>

Oh, one more request...can we mount some outriggers to the john boat? :cool:

Stevie-Ray
February 26, 2003, 09:28 PM
How many grains of powder to they use to launch one of those 2700 pound payloads? 400 lbs. It's extruded powder each grain about the size of a 12 guage shotshell in 100 lb silk bags which are consumed in the fire.

The ship also moves at broadside. Can't remember if it moves laterally to notice, but has a pronounced list due to recoil. I'll check my archives, but this was one of the things brought up on one of the specials on the history of the Dreadnought on the History Channel. I'll see if I can find it in my books.

BigG
February 26, 2003, 11:28 PM
OK, Stevie Ray, what we need to do to make the killer Tyrannosaurus rifle of the 21st century is build a cartridge that will hold one grain of that 12 ga shotshell sized powder and cap it with the largest bullet we can find. It will put the 50 cal BMG to shame for horsepower and probably recoil, too! :eek: Even Dick Casull oughta be impressed! Ouch!

TexasVet
February 27, 2003, 01:39 AM
Naw, he just proved that you can't get there from here.:neener:

rick458
February 27, 2003, 05:13 AM
One of my Buds was in Beruit when the New Jersey was firing on the Druse Militia up in the hills he said it was very cool when She fired you would see a flash from over the horizon, hear the rounds scream over head, hear the boom of the firing, see the splash of the rounds impact and then hear the Boom of the impact,and a big ole chunk of the mountain would be gone.
You just gotta love a weapon like that:evil:

M1911
February 27, 2003, 11:35 AM
I saw the New Jersey twice. Once it was at anchor in San Francisco Bay and the other time it was steaming under the Golden Gate Bridge. Very impressive sight.A while back I went aboard one of the Iowa class in SF. They were tied up and allowing the public on board, though only one the main deck. What beautiful ships.

KelBench400
February 27, 2003, 12:01 PM
I was on board the Jersey last fall. It was $10 dollars well spent. We got to walk all over the ship (within boundaries) on a self-paced tour.

One of the guides was asked if the ship was moved due to recoil. His answer was no. The guns' recoil system absorbs most of the recoil. The picture with the water being disturbed is caused by muzzle blast only. These guides were highly knowledgeable about every facet of the ship...so I don't doubt his answer.

M1911
February 27, 2003, 02:54 PM
KelBench400: I'm jealous. When I went on board, the ship was still in active service, so we weren't allowed below decks. I've visited the USS Massachusetts (http://www.battleshipcove.org), which is a smaller, older ship. Quite impressive.

Wakal
February 27, 2003, 03:15 PM
The average Iowa-class (they were slightly different lengths, with the New Jersey being the longest by an inch and a half) was 887 feet 3 inches, width 108 feet 2 inches. The tightest of the Panama Canal locks is 110 feet :uhoh:

Full powder load was six bags at 110 pounds per bag.

And since their full draft (just ask Captain "Run Aground" Brown) was 29 feet, remember that the "wall of water" she is pushing against has just under twice the pressure at the keel as at the waterline ;)

From empirical data (ship's level indicator and GPS), she did list one degree from TDC with a full 9-round volley, but didn't move enough to deflect the numbers on the GPS.





Alex

Gnull
February 27, 2003, 03:20 PM
I stayed on board the Massachusetts for a couple days when I was about 14.. was a visit to Battleship cove by our Air Cadet Squadron(845 Avro Arrow). Kinda funny to have a Canadian Air-force based youth paramilitary group visit an American NAVAL Ship.. but it wa definatly an amazing sight, and I felt almost like I could crawl into one of those big 16" Cannons.

Heh.. gotta love the old battle-wagons

bountyhunter
February 27, 2003, 06:02 PM
The person who mentions the recoil absorber brings up a good point: a recoil absorber is a spring type device that absorbs recoil energy as it compresses. An important thing to undertsand is that the recoil absorber does not reduce the amount of recoil energy directed into the mount of the gun turret (ie, the ship) by even one iota. That energy is conserved. What a recoil absorber does for any gun is spread out the time over which the recoil impulse is applied to the "mount". For handguns, that is your hand. For a battleship, that's the deck.

People would feel much less "shock" through their feet from the deck at fire with a recoil absorber because the peak of the pulse is lower in amplitude.

As to the ships reactive motion in the water as a result of the recoil (and Newton's Law of motion), would a recoil absorber change the distance it moved? No. The water applies variable resistance based on how fast you try to move through it (try it with your hand in the bathtub). So a sudden sharp pulse gets more resistance, the longer rolling pulse from the effect of the recoil absorber gets less resistance but over a longer time. So, the final amount the ship moves as result would be the same.. although, we have already established it would be quite small.

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