RoundShot program

[TorpX]

This is to announce the release of RoundShot_1.0 (http://www.subsim.com/radioroom/downloads.php?do=file&id=4808). I decided it was more closely related to naval models than any particular Silent Hunter game, so I'm posting it here.

It is a exterior ballistics program that calculates trajectories for any projectile, and displays results in both graphical and numerical forms. Actually, it is probably easier to see for yourself, than for me to explain what it does.

You can use it to compute trajectory parameters for a naval shell, or anything really; a baseball, arrow, rifle/pistol bullet, whatever.

A full help file is included.

It was designed for a 1680x1050 monitor, so you will probably need that, or close to it, for it to display properly.



http://i1130.photobucket.com/albums/m526/TorpX/Misc/RoundShot_zpsnqznodt0.png



If someone could provide early feedback so I know it is working as designed, I would appreciate it.

- TorpX

[Sailor Steve]

Cool!

I played with it a little, but will need some practice before I know enough to give you anything real.

Thanks for this. :rock:

[TorpX]

I'm glad you like it.

I know you have an interest in early naval battles and such. I don't have a lot of information about naval ordnance, but I have a copy of ROUND SHOT AND RAMMERS by Harold L. Peterson. It has some ballistic data. Maybe I'll post some of it. I did some computations on one of the pieces to verify the program's math was right.

[TorpX]

I did some calculations for a 6 pdr. 1840's field gun to see how the program results would stack up to what's in the book.

First, from the table of fire in the book:

solid shot

Elevation, deg. ___________ Range, ft.
0° _______________________954
1 ________________________2,022
2 _______________________2,601
3 ______________________ 3,414
4 _______________________3,768
5 _______________________4,569


Calculated with RoundShot:
using
6.1 lbs., V0 1439 ft./sec., 196,000 ft.-lbs.
LgSphere drag function C 0.522

Elevation*_ Ymax _____Range ______ Vel. ____Time ___kE
deg.______ft._________ft.________ft./sec.____sec.___ft.-lbs.
0.3_____4.8________944________1,025____0.787____99 ,712
1.3_____16.5_______1,928_______809_____1.880____62 ,130
2.3_____38.2_______2,729_______719_____2.937____49 ,057
3.3_____67.4_______3,406_______672_____3.918____42 ,825
4.3____103________4,007_______641_____4.843____39, 009
5.3____144________4,555_______619_____5.727____36, 383

10.3___420_______6,833_______562______9.767____29, 939
15.3___794_______8,636_______530_____13.467____26, 673

*Note the above was calculated on the basis of the barrel being 4 ft. above ground level, and recoil producing a 0.3 degree 'jump'.

One can see that while the shot slows quickly at the start, drag becomes much less, and velocity loss occurs very slow around 600 or so. This corresponds to the graph of the drag function I used for the large sphere, so it is not really a surprise.

I consider these results to be in good agreement.

I have no idea, offhand what kind of kinetic energy would be required for a 6 lb. shot to breach a wood hulled ship, a stone wall, or ricochet, but certainly the shot would be lethal to personnel, even at long range.

[TorpX]

Here is another sample calculation, this for a 12.3 pound solid shot fired from a 12 pdr. light field gun M1857 (Napoleon). C for LgSphere is 0.644 and V0 is 1440. Muzzle energy is 396363 ft.-lbs.

First the book values:

Elevation ______ Range
0 ______________969
1 _____________ 1860
2 _____________ 2625
3 _____________ 3600
4 _____________ 3975
5 _____________ 5040


Calculated:

Elevation*_ Ymax _____Range ______ Vel. ____Time ___kE
deg.______ft._________ft.________ft./sec.____sec.___ft.-lbs.
0 ________ 4.8 ______ 972 _______ 1077 ____ 0.788 __ 221000
1 ________ 17.0 _____ 2047 ______ 855 ____ 1.919 __ 140000
2 ________ 40.1 _____ 2929 ______ 753 ____ 3.027 __ 108000
3 ________ 71.5 _____ 3672 ______ 700 _____ 4.056 __ 93000
4 _______ 109.9 _____ 4328 ______ 667 _____ 5.026 __ 85000
5 _______ 154.5 _____ 4924 ______ 643 _____ 5.950 __ 79000

10 ______ 453.9 _____ 7391 ______ 584 _____ 10.16 __ 65000
15 ______ 858.3 _____ 9353 ______ 559 _____ 13.99 __ 60000

I used the same 4 ft. muzzle height and 0.3 degree jump in these calculations. Agreement is pretty good, but there is some disagreement for the 4 deg. line. I'm not sure how the Dept. of Ordnance did their calculations, but these predate the Siacci method.