Beware essays written at random. Still, less then an hour, probably worth the time spent.
A heads-up to the BSG mod folks (particularly as GameWarden refuses to send me a registration email no matter how many times I register): Galactica's main guns aren't automatic! I was watching my First Season DVDs yesterday, and in "33" Tigh says "You've got a red light in the main gun ammunition hoists right there!"
This struck me because I've been visiting NavWeps too much lately, and so have become familar with the terminology associated with turrets and such. An ammunition hoist brings ammunition from the magazine, deeper inside the ship, up to the turret. A hoist, also, is not how one describes an automatic weapon (those have feeds), and BSG has been remarkably accurate so far its usage of naval terminology. (Also those times we seen Galactica's main battery firing, the heavy upper guns as opposed to the AAS batteries on the flight pods, they appear to fire single shots at noticible interval, not near-continous streams like the AAS guns.) The closest that Galactica's main guns can come to being automatic, then, is using a "clip" or "revolver" reload system in which ammunition is in containers which allow for bursts of rapid fire before needing to reload.
Also, examining various screenshots, Galactica's main guns are definitely in the running for largest naval artillery ever. I would
conservatively call their projectiles 18". It's quite possible they're closer to 22" or 24". (Which would mean Galactica doesn't actually need the Raptors to deploy its nukes; you could easily fire the weapon seen in "Kobol's Last Gleaming Pt. 2" out of one of the main battery turret guns.)
Just for fun, let's present a figure on the armor penetration of one of Galactica's main battery rounds, at absolute minimum. For absolute minimum, we'll use the guns of another, considerably less advanced ship; the HIJMS
Yamato, whose 18" guns roughly match the size of Galactica's (at minimum), but whose rounds probably have much less impressive ballistic qualities. (
Yamato's guns had rather unimpressive ballistic qualities for the time, never mind the Colonial Fleet's weapons.)
So, we dig up a range/penetration table from
http://www.combinedfleet.com/f_guns.htm#6 and look up
Yamato's armor penetration values. Whoops, it mentions the usage of two major armor types. But never fear! We can narrow that. Cylon Basestars use curved plating, which means it is probably homogenous; face-hardened armor is almost impossible to produce in curved shapes. We can discount the figures for varying ranges, as this is in space, and gravity/air do not effect the ballistics of the projectile; its muzzle velocity will be its only velocity. Thus, only the range of zero penetration against homogenous armor figure interests us.
With this deduction, 32.7 inches makes for a good absolute minimum armor penetration figure for a round from Galactia's main battery. With all the variables involved, for 100% safety a full yard of armor is probably required. Three whole feet. That is a
lot of armor, and to completely armor a ship in it would be prohibitive in several senses (both in actual amount of material and in terms of having to get all that very heavy stuff moving at a decent clip). Galactica's main battery is therefore probably quite capable of punching through the armor on a Basestar.
But wait, there's more! Many people have commented on Galactica's odd appearance of being partially plated. From the same site mentioned above, however, comes an explanation. The partial plating is very much intentional. In fact, it's an integral part of Galactica's defensive system. Those are decapping plates. Now, why are they important? First, a little study in what gets thrown at them.
An armor-piercing projectile uses an armor-piercing cap (good diagram and picture to be found on this page:
http://www.navweaps.com/Weapons/Gun_Data_p2.htm) to help penetration. The cap is not an integral part of the projectile, but is designed to shatter on impact; nonetheless it will deliever considerable kinetic energy in the few moments before it does. The cap serves several purposes; it increases the "biting" angle, the angle at which the round will penetrate rather then deflect; it pre-stresses the plate; and it helps prevent the round from shattering by spreading the stress of the inital impact over the entire nose of the actual round. (The possiblity of shattering is quite real, actually.)
Armor-piercing explosives (read that: Cylon missiles) come in essentially one category: HEAT, High Explosive Anti-Tank. They function by superheating the outermost armor to a liquid state, and then forcing a jet of that superheated exterior armor through the rest of the armor and into whatever the armor is protecting. (A jet of several thousand degree molten metal coming through the wall of your tank is obviously A Bad Thing.) HEAT ammunition is extremely effective against homogenous forged armor plate, nearly unstoppable. (If you ever wonder why tank turrets stopped being round, here's the answer. They wanted facehardened plates. Those do better, but not by too much.) There are currently two ways known to reliably defeat a HEAT round: reactive armor, which essentially blows off when hit, presenting a gap between the exterior plate and interior plate through which the jet of molten metal cannot cross, and the Chobham ceramic used on the M1 Abrams and most other NATO tanks, which has a much higher melting point.
Now, back to those decapping plates. Though the idea occurred to many before the demise of naval artillery duels, the only ships ever to mount real decapping plates were US battleships, starting with the USS
South Dakota. This was because only the US could afford to spend the money. (The US did several things in terms of protection that nobody else could simply afford to.) The decapping plates proved their effectiveness in actual combat at least once, and the concept, proved by math and more recently computer simulation, is quite sound. By causing the armor-piercing cap to shatter prematurely, the effectiveness of the round is reduced greatly. (Gory details and high-level math:
http://www.combinedfleet.com/okun_biz.htm.)
Against a HEAT round, the effectiveness of a decapping plate lies in the fact that it is posistioned outboard of the main armor, with a gap between it and the main armor...a gap which that jet of molten metal will have a tough time crossing and retaining the heat to push through the main armor belt.
Thus Galactica's partially plated appearance, with its decapping plates. As has been noted, the AAS guns are often posistioned between the ribs, so the ship was probably never meant to be fully covered by decapping plate (although it is very concieveable that there was originally more of it). The plating, then, would have been placed over critical areas. (Whether it still is only God knows; but the engines seem to have retained their plating, so it's possible.)
