Spaceship Feasibility

[Caiaphas]

First off, please don't lambast me for anything I'm about to say. I do believe that my ineptitude in physics has been established elsewhere, and looking things up on Wikipedia and Google sure as hell ain't going to teach me anything worth a damn about it.

Righty then. I'm writing up a scifi short story involving a battle between two opposing forces, separated by about 5 or six lightseconds. These ranges, in my universe, are status quo for most battles. The essential data is defined thusly:

Light Fighters: designed for anti-ship work, as in swarms of them v. one larger ship, not fighter-on-fighter
Dimensions:
-20 m long
-8 m high
-7 m wide
-2 m armor plating (plating is usually layered ceramics, titanium, and a relatively thin layer of DU thrown in for variety. If anyone has any suggestions as to what would make better armor, please post. Thanks.)
-1.344e7 kg
-capable of sustaining 15G for one minute

Armaments:
-1 25mm coilgun capable of accelerating a 340 g DU projectile to nearly 3km/s
-1 underslung missile launcher
-6 antiship missiles, w/rails allowing 3 more to be mounted
-3 antimissile laser arrays

Destroyers: primarily intended to blow up any incoming enemy missiles or fighters
Dimensions:
-100 m long
-700 m high
-100 m wide
-10 m armor plating
-9.1e10 kg
-capable of 10G for five minutes

Armaments:
-25 antimissile laser arrays (10 on each side of the ship, 2 on the bow, 3 on the stern)
-15 antifighter laser arrays (ditto)
-3 95mm point-defense coilguns

Cruisers: primary assault vessels
Dimensions:
-800 m long
-150 m high
-150 m wide
-20 m armor plating
-2.34e11 kg
-capable of sustaining 4G for an hour

Armaments:
-10 antimissile arrays (short-range)
-3 antifighter arrays (also short-range)
-1 main laser cannon
-10 missile bays (each with 20 missiles)
-8 105mm point-defense coilguns

Standard design as a part of any ship armor is a rapidly self-healing polymer buried in between layers of ceramic/metal/yadda yadda. It's kept under constant pressure; when that pressure is released, such as when a projectile manages to breach the hull, the polymer foams up and seals the breach.

Laser arrays have three lasers in them that are each capable of putting out a good 16+ MW on a target. Short-range ones simply decrease power output per laser and are programmed to focus all three lasers on one single target. They aren't intended for ship-to-ship combat, but can be effectively used against larger ships, if you know where to hit.

Missiles are still in use because that quick-foam polymer I mentioned earlier? Yeah, it doesn't conduct hear all that well, won't melt, and won't heat up too appreciably in the first place. You need missiles to blast gaping holes in ship armor, but there are those pesky antimissile lasers to deal with.

I still haven't managed to figure out a rationale for fighters. Help?

So how would you modify the specifications given above, and what would be your strategy for carrying out this battle, as either the aggressor or the defender?

Thanks, y'all.

[Ghost Rider]

Y'know...write the story first. Keep all this for yourself or people you just want to understand some of the mechanics, but write the story first.

Having all of this is useless for us because there is no context to place it against. Sure, some will place in a realistic construct of their choosing(a likely mere 5-10 year thought) but that doesn't give anything but that. If you made the history, industry and civilization of your universe to think this way...keep that consistent and write the story with that in mind.

All this is no more then RPG stats at best.

[Caiaphas]

Y'know...write the story first.

Got it.

[Havok]

Yeah, like GR said. Leave all the nerdy figuring to the readers if they feel like doing it.

[Simon_Jester]

Well, you can salt in a very few figures to give some concept of speeds and sizes to aid the imagination... but the technical specs of the equipment are best kept off the table, because they will rarely do anything to make the story more plausible.

[Ford Prefect]

1.344e7 kg

Your fighters mass ten thousand tons?

[GrandMasterTerwynn]

First off, please don't lambast me for anything I'm about to say. I do believe that my ineptitude in physics has been established elsewhere, and looking things up on Wikipedia and Google sure as hell ain't going to teach me anything worth a damn about it.

Righty then. I'm writing up a scifi short story involving a battle between two opposing forces, separated by about 5 or six lightseconds. These ranges, in my universe, are status quo for most battles. The essential data is defined thusly:

Light Fighters: designed for anti-ship work, as in swarms of them v. one larger ship, not fighter-on-fighter
Dimensions:
-20 m long
-8 m high
-7 m wide
-2 m armor plating (plating is usually layered ceramics, titanium, and a relatively thin layer of DU thrown in for variety. If anyone has any suggestions as to what would make better armor, please post. Thanks.)
-1.344e7 kg
-capable of sustaining 15G for one minute

Your fighter is the size of a space shuttle orbiter and masses roughly 100 times as much. And you've wrapped it in an insane amount of armor. As has been mentioned, your light fighters also have only 8.82 km/sec of delta-V. They'd about 56 hours to cross six light-seconds from a dead stop.

Armaments:
-1 25mm coilgun capable of accelerating a 340 g DU projectile to nearly 3km/s

Each shot from this coilgun will push the ship in the opposite direction at 0.477 m/s. Which is to say that in 19 shots, you completely deplete your fighter's delta-V (assuming no funky recoil energy absorption/deflection system.)

Destroyers: primarily intended to blow up any incoming enemy missiles or fighters
Dimensions:
-100 m long
-700 m high
-100 m wide
-10 m armor plating
-9.1e10 kg
-capable of 10G for five minutes

The physics hilarity grows. This ship weighs 91 million metric tons. Where does all that mass come from? Another thing, this implies a density of some 13,000 kg/m^3. Which is greater than the density of a solid block of lead! (Which only manages 11,300 kg/m^3) You've asked us not to lambast your lack of physics knowledge. Which is why I'll reiterate what has been written before: Don't mention your stats anywhere in-story.

[Havok]

See, just write the story and let the nerds froth over the details man.

[Caiaphas]

Whoops.

Note to self: reconfirm calcs before posting next time.