[Spaceships] Conventional and EM Gun ranges in atmosphere?

[vicky_molokh]

Originally Posted by Humabout

Using DouglasCole's formulas, I get a 2cm shell with a 1 mps muzzle velocity having the following stats:

Damage: 69d+2 pi++
Range: 3,800/26,000 yd

This assumes an aspect ratio of 3:1, and DU slug. Increasing the aspect ratio to the upper end of modern 20mm shells (6:1), you get:

Hmm. A 2½cm conventional slug from SS does 3d(2) dDamage, i.e. 30d normal damage.

Originally Posted by Humabout

Damage: 99d+2 pi++
Range: 9,700/48,000 yd

Running with a muzzle velocity of 2mps, you get the following:

3:1 Aspect Ratio
Damage: 142d+3 pi++
Range: 3,800/35,000 yd

6:1 Aspect Ratio
Damage: 205d pi++
Range: 9,700/64,000 yd

Again 2cm VRF EM Gun does 60d, i.e. your guns seem to be better.

Just saying.

[Varyon]

Originally Posted by vicky_molokh

Hmm. A 2½cm conventional slug from SS does 3d(2) dDamage, i.e. 30d normal damage.

Again 2cm VRF EM Gun does 60d, i.e. your guns seem to be better.

Just saying.

SS conventional shells appear to be 50% propellant, and the projectile itself loses about 50% of its mass (based on damage) before hitting the target. EM just lacks the propellant. This second loss is likely in the form of reaction mass, decoys, etc. The mass given for Gauss/Grav shells corresponds to a 2:1 ratio of lead or steel (I calculated masses for the unguided rounds of my setting by figuring out the mass of lead/steel of a sphere of the right caliber, then doubling it; my numbers were almost exactly what you see in SS, so I went with those instead). So, use the ballistics spreadsheet with a 2:1 ratio and then halve damage (to account for mass loss). Assume the increased range from using a rocket and the decreased range from weighing less for part of the travel time cancel out.
That, or just use Anthony's quick-and-dirty rule.