The subject of large-caliber shells and their interaction with armor plate is a topic which has become sort of all-consuming for me of late. Why? Because if you're gonna have the audacity to put up a Battleship page that purports to have any shred of credibility whatsoever, you've got to understand how the armament and protective systems of these beasts worked. In pursuit of that goal, I hunted down the elusive Nathan Okun, the Godfather of Terminal Ballistics, and humbly beseached him to enlighten me. Fortunately for me, Nathan likes to talk, and he told me a lot I hadn't known before. Better yet, he sent me a lot of really cool stuff, and I have reproduced as much of it as I can on this page. I will be posting additional articles on the topics of ballistics and armor penetration as time allows.
ARMOR PROTECTION OF KM BISMARCK© by Nathan Okun. In this article, the author examines the protective schemes of not only the Bismarck, but also the Yamato, South Dakota, King George V, Richelieu, and Vittorio Veneto. The analytic 'tool' used is Bismarck's 15"/47 gun, which is fired at each ship through every applicable amidships trajectory, both belt and deck armor. The results are sometimes surprising: for instance, for all her vaunted combat power, Bismarck has the weakest side protective system of any contemporary battleship. On the other hand, South Dakota has a better belt armor design than even the mighty Yamato! This article is the most comprehensive, detailed analysis of battleship protective schemes I have ever read.
MAJOR HISTORICAL NAVAL ARMOR PENETRATION FORMULAE© by Nathan Okun. This article examines the progression of formulae used to quantify the phenomenon of armor penetration.
TABLE OF METALLURGICAL PROPERTIES OF NAVAL ARMOR AND CONSTRUCTION MATERIALS© by Nathan Okun. This article lays out the physical properties of the major types of homogeneous and face-hardened armor steels from the 1800's to the present.
MISCELLANEOUS NAVAL-ARMOR-RELATED FORMULAE © by Nathan Okun. A a compilation of formulae, data tables, and related information that can be used to develop rules for ascertaining ship damage when hit by gun projectiles and aircraft bombs of various types .
NATHAN OKUN'S FACE-HARDENED ARMOR PENETRATION CALCULATOR. Wanna find out what might have happened if Kirishima had hit South Dakota in her belt, instead of on her curved barbette? Or whether or not Prinz Eugen actually could have sunk HMS Hood? This here is the software you need. With this calculator, and a good reference book (like Campbell's "Naval Weapons of World War II"), you can calculate the armor penetration, exit angle, remaining velocity and shell condition, and the size and velocity of the armor plugs thrown off by any shell hit against practically any variety of face-hardened armor plate, from Gruson chilled in the 1800's up to and including the Krupp KC n/A that armored the hide of the Bismarck!
Included are three programs: FACEHARD.EXE, OBLICALC.EXE, and BRUN45.EXE. FACEHARD.EXE is the actual penetration calculator. OBLICALC.EXE is an obliquity calculator, which will calculate the final obliquity of an incoming shell, taking into account the target's course, roll, yaw, inclination of armor plates, and so on. BRUN45.EXE is the runtime Basic engine that runs both of the programs. Simply download the files to a directory and run the programs from a DOS-Prompt. Have at 'em!
Incidentally, I have the source code for these programs, if anybody wants them.
There are some collateral materials you will find useful if you want to get serious about this sort of thing. As I mentioned, Campbell's book is very useful for getting things like ballistic and shell data, because Nathan's program requires inputs like velocity, angle of impact of the shell, weight of shell, and so on. In addition, I grabbed a curve-fitting program off the Web, CurveExpert 1.2, for fitting curves to the ballistics data I got out of Campbell, so that I could calculate reasonable velocities and fall angles for a given shell at any range. The final thing you'll need will be good reference books on the ships you're shooting at, in order to get an idea of their internal layout, armor belt inclination, spacing of armor decks, and so on. I'm a big fan of Dulin & Garzke's works on the subject; they have excellent cross-sectional diagrams.