Projectile flying altitude

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Javier L.
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Projectile flying altitude

Post by Javier L. » Sat Nov 13, 2004 5:56 pm

How high in the air can a heavy projectile travel during its flying time? 100 meters? I suppose it will depend on the distance the guns are firing at (elevation of the barrels) and type of gun. At short range the trajectory will be very low and at long range it will be higher, but I am just curious.

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Re: Projectile flying altitude

Post by Tiornu » Sat Nov 13, 2004 8:29 pm

I'm sure you know the figure will be individualized for each weapon, but I can give you some examples. The 16in guns of the Colorado class battleships when firing 2100-lb shells at 2600f/s at the maximum elevation of 30deg would achieve a "maximum ordinate" (highpoint of flight) of just over 19,000 feet! That means the ordinate is roughly 18% of the gun range. If we move things out to a theoretical 45deg elevation (which would have been possible for the North Carolina class battleships, but they never used this ammunition), the maximum ordinate is 35,699 feet while the range is 39,600 yards, so the ordinate is now 30% of the range.

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Post by Javier L. » Sat Nov 13, 2004 9:01 pm

19,000 feet! That’s almost 6 kilometers high! :o I knew projectiles flew high when fired at long distance but this is far more than I thought. These guns could even be used as mortars and fire over a mountain when used for shore bombardment then! Anyway, what about the "minimum ordinate"? Do you have data on what the flying altitude of these 16" shells would be for short range fire? Let’s say with a 1 - 5º elevation.

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Post by Tiornu » Sat Nov 13, 2004 9:32 pm

The maximum ordinate for a range of 1000 yards is 2 feet. Gun elevation would be 25'. Of course, we need to remember that the range and ordinate figures are measured on the level with the guns, which are mounted several meters above the waterline; the shells would get as high as 2 feet above the gun mounting, then descend again to the level of the gun mounting at a distance of 1000 yards. They would take considerably more range to get from the level of the gun mounting down to the level of the water.

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Post by Tiornu » Sat Nov 13, 2004 9:44 pm

I thought of another indicator that may help put these things in perspective. I'm sure you are familiar with the concept of acceleration due to gravity. You can tie this in with the shell's time of flight. The shell fired to 1000 yards has a flight time of just 1.17 seconds. The flight time for 39,600 yards is 94.6 seconds.
The striking velocity of shells tends to be at its minimum when fired at an elevation near 30deg. Keeping to our example of the shell fired at 2600f/s, the shell at 1000 yards strikes the target at a speed of 2532f/s. At 39,600 yards, it's 1559f/s. The lowest velocity I see is 1400f/s at a range of about 30,500 yards (elevation 24deg). The maximum ordinate there is 12,622 feet with a flight time of 55.84 seconds.
These numbers look so precise, we need to remember that they are theoretical, without any consideration for wind, humidity, and many other factors.

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Post by Javier L. » Sat Nov 13, 2004 10:15 pm

Thank you for your replies. I am enjoying this conversation. So basically what you are saying is that the 16" shell were are discussing would have a greater striking velocity at 39,600 yards (45º elevation) than at 30,500 yards (24º elevation) even if the distance is greater because it flies higher and the force of gravity therefore affects more its descent accelerating the shell, right? I didn’t think about it, but it is pure physics and must apply to all shells then. However at short range of less than 10,000 yards the force of gravity would not have that much influence in the striking velocity of the shell since the angle of fall is not very big, and therefore the striking velocity at let's say 9,600 yards can't be greater than at 5,500 yards.

Could we say that at short range shells are propelled by the force of the explosion of the propellant charge inside the gun barrel, and at long range they are "propelled" only by the force of gravity?

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Post by Tiornu » Sat Nov 13, 2004 11:29 pm

No, I wouldn't go quite that far. In terms of its vertical vector, the shell at its maximum ordinate is moving at zero velocity, so all subsequent vertical speed derives from gravity; but in terms of its horizontal vector, it's still moving entirely because of the firing of the propellant. I guess that, once you get past that 24deg elevation, the acceleration due to gravity is greater than the deceleration due to air resistance.

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Post by José M. Rico » Sun Nov 14, 2004 1:08 am

The point in which the acceleration due to gravity begins to be greater than the deceleration due to air resistance varies depending on the gun used. According to 100/40 g.Kdos, the lowest striking velocity for the German 800-kg shells of the 38cm SK. C/34 gun is 457 mps (1,500 fps) at a range of 32,000 meters (34,995 yards) with a barrel elevation of 25º. The striking angle at that distance is 35º and the shell flight time 61 seconds. Longer shots have their striking velocity increased due to gravity.

Since you were talking about flight height, can anyone calculate the maximum ordinate of the German 38cm shells given the data above?

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Post by Jack B. » Sun Nov 14, 2004 3:49 am

Not much to do with naval guns, but I just had to post this info on this German gun
The Paris Gun - properly called the Kaiser Wilhelm Geschutz - was so-named for its sole purpose of shelling Paris from extreme distances starting from March 1918. A behemoth, the Paris Gun - regarded by many as the ancestor to the German V3 - was capable of firing shells into the stratosphere from locations as far as 131km from Paris.

Designed and operated by the German Navy and manufactured by the German munitions firm of Krupp, some seven 210mm guns were made using bored-out 380mm naval guns, each fitted with special 40 metre long inserted barrels. However with only two railway gun mountings actually available just three of the guns were ever in use at any one time, fired from the Forest of Coucy.

Such was the rapid wear and tear of firing its 120kg shells, each requiring a 180kg powder charge, towards Paris - the aim was often wild - that the gun's lining required reboring after approximately 20 shots. Indeed, after every firing the succeeding shell needed to be of slightly greater width.

An undoubted sensation when first deployed (at 7.18 on the morning of 21 March 1918) the appearance of heavy shells in Paris caused initial and widespread alarm among its inhabitants which nevertheless quickly subsided. Once fired a shell took 170 seconds to reach Paris, rising as high as 40 km above the earth.

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Post by marty1 » Sun Nov 14, 2004 11:44 pm

I have the 1935 range tables for USN 16-inch gun. Mv = 2000-fps. Projectile Wght = 2100-lbs

For Range Setting = 24,000-yrds
Launch Angle = 34-deg 59.9-minutes
The Maximum Ordinate (i.e. max height of trajectory) is indicated as being 15,096-feet. That's a maximum trajectory height of about 4.6-km

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Post by Tiornu » Mon Nov 15, 2004 1:41 am

That would have to be a table for reduced charges. No naval gun had a service charge producing such a low MV. The lowest velocity for any dreadnought gun was for the Italian 15in gun of WWI; the exact figure, I believe, was 700m/s or 2297f/s, barely edging out the 2300f/s of the US 16in/45 firing a 2700-lb shell. There's some irony in the fact that the Italian 15in gun of WWII fired at 870m/s, which is about as fast as you'll find, especially for last-generation battleships.
The Americans apparently had plans for using reduced charges in the anti-ship role. I don't know of any other navy that did this. The stated intent was to achieve more and deeper deck hits. The Japanese had three ratings--service, weak, and reduced--but only service charges were to be used against ships.

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Post by marty1 » Mon Nov 15, 2004 2:17 am

There are two sets of tables for 16-inch -- one for Mv=2600-fps and one for reduced-charge Mv=2000-fps.

Max Ordinate for Mv=2600-fps for a range set of 24000-yrd is 6,320-feet.

Same again for 14-inch range tables. There are two sets of range tables -- one for 2000-fps (reduced charge) and one for mv=2600-fps.

However I think the question was regarding max trajectory ordinate for a heavy projectile. For USN 16-inch fired at mv-2000-fps -- and range set of 24000-yrds the maximum projectile trajectory height is indicated as being a tad over 4.6-kilometers.

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Post by marty1 » Mon Nov 15, 2004 2:31 am

one more observation unrelated to the original thread subject. sorry -- not trying to hijack the thread. however the reduced charge range tables cover ranges 1000-yrds to 4000-yrds then they stop. they pick up again at range = 23,500-yrds and stop again at range=25,100-yrds. same again for both the 14-inch and 16-inch range tables.

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