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The Iron Sky -team is looking for your ideas and comments. Join and show your support for Iron Sky.  Types of shellsThere is another factor to consider. If the shell is armor piercing, it would behave differently than if it's an explosive round or one that is a shaped charge. The classic armor piercing shell, based upon the many photos I've seen of tanks and ships in WWII, would have an entry not unlike a puncture, with a webbed cratering around the puncture. Or else, if the armor is thick enough, create a dent. Sometimes the armored shell has a small explosive charge, but it's primary aim remains to cause internal damage. The shrapnel would be murderous. An explosive shell would normally explode on impact. A shaped charge combines the two. It uses a metal conical hollow cavity in the tip of the shell followed by the explosive. The effect is to focus the force of the explosive in a specific direction resulting in enormous pressure, multiplying the effect of the round. Today, nearly all modern anti-tank weapons use shape charges. However, if the weapons are to be used in space, the lack of oxygen in a vacuum may favor the classic armor piecing naval-type round. |
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Actually, Gauss guns and coil guns are the same thing, but both are completely different from rails guns. They produce their magnetic fields in completely different ways.
http://en.wikipedia.org/wiki/Coilgun
http://en.wikipedia.org/wiki/Railgun
Missiles could work, but they would have to be giants bigger than Russian anti-ship missiles. It's because a ship is going to have lots more fuel and probably better thrust, so you need lots of fuel in a missile to keep up with the ship's maneuvers. The saucers don't even use reaction mass, so they may have a huge advantage when it comes to evasive maneuvers.
I'm also glad you decided to go with railguns. (Railguns, gauss guns, and coilguns are the same technology implemented in different ways.) I feel those are more plausible for the reasons outlined by MajorD, but also because the designs without guided munitions would be simpler, more direct. The military mind has two sides: the part that loves technological toys and the part that lives on the battlefield and knows that simplicity wins every time. (If you get the chance, read the short story "Superiority" by Arthur C. Clarke.)
Railguns and gauss guns (which are the same as coilguns) have about the same muzzle velocity so to be honest there would be little to distinguish them apart other than the types of projectiles and manner in which they accelerate the shell. The experimental railguns I've seen use 2 to 4 kg shells although if you have enough power there should be no limit to the size of the shell.
I should note that the Germans in WWII invented the air-to-air missile, the wire guided missile, and the air-to-ship missile. The last was successfully used to sink an Italian battleship. Now that I think about it, if you can guide the hyperkinetic munitions, why bother with missiles? A missile would have longer range, but would not be as fast a projectile from a railgun.
As it happens, the U.S. Air Force and Navy do plan to have airborne and shipborne lasers deployed by 2018. The Army hopes to have truck mounted lasers in the 150 kw range out in the field by 2012.
I'm glad you're using rail guns, realistically coils guns would be too complicated. More so for the Nazis who shouldn't be able to have as wide spread a technological base. However, rail guns have plenty of issues of their own.
Not only would the Nazi rail guns not have the aid of computers as advanced as Earth's, but with a small population base, their industry has to be less diverse. That will narrow and slow the number of technologies they can research. While they may have rail guns, those rail guns may wear out faster, have less peak velocity, be larger, be heavier, charge slower, and so on.
The ammunition needing terminal guidance from a ship might depend on the size of the ammunition. Current kinetic kill vehicles are 63 kg (140 lb), is 140 cm (55 in) long and about 60 cm (24 in) in diameter. A much smaller one should be possible. Although, it would carry less fuel, that might be made up for by the launch platform's ability to better direct the round before launch through the use of predictive gunnery. The ability to correct trajectory mid-flight is a tremendous effective range extender not to be underestimated. While dumb rounds for close in combat will be useful, as will programmable smart rounds against soft targets, they can't be as effective as a round that can correct course. So, I for one want to see guided rounds, not missiles, but something like the kinetic kill round which can slide perpendicular to the target. Or, a round like AHEAD, which is programmed with range and detonation information as it leaves the muzzle break of the gun.
The AHEAD round is fired by the Oerlikon 35mm Millennium gun.
http://www.rheinmetall-defence.com/index.php?lang=3&fid=2450
But, as I mentioned, it's really for soft targets, such as missiles, and I doubt the Moon Nazis will use missiles, and I'm betting on the saucers being tank tough.
http://www.youtube.com/watch?v=7ogwfPrV1fk&feature=related
By 2018, we should also have effective lasers, so we should see them as well. But, they should be presented realistically, with no visible beam unless it passes through a debris, gas, or other particle cloud, and should cause explosive damage on targets given enough power. Or, it should look like a cutting torch being put to work on the enemy hull.
Just in case you didn't know about it, the newest version of the US Navy rail gun was shown in a video. It's a lot smaller than the test version with the same bore diameter. I guess it could be nothing more than a mock up, rather than the next version, but it still shows where they expect to be in the near future.
http://defensetech.org/2010/05/05/killer-drone-builder-general-atomics-builds-killer-electromagnetic-rail-cannon/
Main weapons we've had in mind are railguns and gauss guns, and they mainly use kinetic rounds. Hypervelocity kinetic kills have a lot more balls than explosive rounds. I think they'd use solid tungsten (Nazis would call it Wolfram I suppose) or depleted uranium ammunition. Earth technology might have more sophisticated properties to the ammunition, like in-flight adjustment to the trajectory per radar feed from the ship, but I think we'd all sooner have simple solid metal rounds rather than ammunition with guidance electronics, thrusters etc.
I think I talked about it in another post, but the kinetic energy of a coilgun would be fierce. For the sake of comparison, the kinetic energy of a 125mm cannon shell is about 1.4 megajoules per kilogram. The tungsten core slug fired from an experimental railgun has about 4.5 megajoules per kilogram of kinetic energy because it's moving at 7000 mph. That works out to the explosive force of a hectogram of TNT for each kilogram of the slug. Combine that with a shaped charge which would multiply the effect on armor and you have a devastating weapon in anyone's book.
So you could either use the coilgun to fire smaller, lighter shells to get a high rate of fire (imagine a rifle that hits like a 20mm cannon) or go for mass and pulverize your target. Either way, the effect of hyper velocities shouldn't be discounted.
Since it looks like the Moon Nazi saucers will use coil guns, explosive rounds may not be worth while since they'll be able to kick their rounds up to very high velocities. Then again, if the coil gun is only as good as a normal gun, but used to exploit better power generation, then explosive rounds may be used after all.