Guns! Guns! Guns! and GURPS

[GURPS Fox]

Originally Posted by Fred Brackin

UT says "probably not".

The 3D6 Laser Pistol weighs only 1 lb sans power cell. The 6D6 Laser Rifle is 8lbs (it's D cell is in a power pack). That's 8x weight for 2x damage.

The 3D6 Gauss Machine Pistol weighs 2.4 lbs without ammo or power cells (2 Bs). The 6D+2 Gauss Rifle weighs 6.6 lbs in the same condition. Not a cubed relationship.

You might get different results from Spaceships but Spaceships is very gamist in its' scaling.

From what I've been told, this is the back-engineered EM Gun equation for 4e:

EM gun weight = muzzle energy in KJ × 0.735 if RoF=1, if RoF is >1, then use KJ ×(1+(ROF/20)²) and if RoF <1, then use KJ × √(1/the number of seconds between firings).

So, a 10,000kJ EM gun firing once a second would mean 10,000 x 0.735 which means 7350lbs (roughly).

[Fred Brackin]

Originally Posted by GURPS Fox

From what I've been told, this is the back-engineered EM Gun equation for 4e:

E.

Back engineered from _what_?

[GURPS Fox]

Originally Posted by Fred Brackin

Back engineered from _what_?

From what the guy that I worked with said, Ultra-Tech although the equation doesn't 100% work with the stated stats.

[Rupert]

Originally Posted by Fred Brackin

Spaceships' Projectile base damage is linear with caliber and doubles every 4 SM or 100x mass. I don't think that's the relationship GURPS Fox was aniticipating and isn't the same one the Energy Weapons use.

I generally don't use Spacships as a primary source for tech facts. That's not what it was designed for.

I agree. It can be used to gain some insights, but should be used for this cautiously and after other sources have been found to be lacking.

[Fred Brackin]

Originally Posted by GURPS Fox

From what the guy that I worked with said, Ultra-Tech although the equation doesn't 100% work with the stated stats.

UT seems a unlikely source. It doesn't work with outputs in kj. Even Ve2 didn't.

[GURPS Fox]

Originally Posted by Fred Brackin

UT seems a unlikely source. It doesn't work with outputs in kj. Even Ve2 didn't.

Then again, 3G3 does, surprisingly enough, and that is very in line with 3e's weapons in terms of weight.

[Anthony]

VE2 does tell you the energy cost per shot for EM weapons, though it has some glitches.

[GURPS Fox]

Originally Posted by Anthony

VE2 does tell you the energy cost per shot for EM weapons, though it has some glitches.

Yeah, but the real problem is that, for my purposes (which uses high-density ammunition), that makes it insane to keep firing. The original 5k kW discharge rate is, insane when you've got a projectile that is, roughly, 13.5 kg, let alone one that is firing 40 rounds a second.

[Rupert]

Originally Posted by GURPS Fox

Yeah, but the real problem is that, for my purposes (which uses high-density ammunition), that makes it insane to keep firing. The original 5k kW discharge rate is, insane when you've got a projectile that is, roughly, 13.5 kg, let alone one that is firing 40 rounds a second.

Well if you're firing 13.5 Kg projectiles at 40/s, if they're going at any reasonable velocity you're going to have a massive energy consumption, and that's all there is to it. If the muzzle velocity is 1000 m/s (for example) that's 270 MW at 100% efficiency. Whether it comes from chemical propellants, electromagnetic drivers, or electrically generated plasma doesn't matter, it has to come from somewhere, and that's a lot of energy.

[GURPS Fox]

Originally Posted by Rupert

Well if you're firing 13.5 Kg projectiles at 40/s, if they're going at any reasonable velocity you're going to have a massive energy consumption, and that's all there is to it. If the muzzle velocity is 1000 m/s (for example) that's 270 MW at 100% efficiency. Whether it comes from chemical propellants, electromagnetic drivers, or electrically generated plasma doesn't matter, it has to come from somewhere, and that's a lot of energy.

Well, the guns are railguns (of the Gatling kind) flinging rounds at 5km/s, but the biggest problem is that using the standard electric consumption rate, you just reinforce the 'all guns in the future will be DEWs' trope, which is something I want to avoid.

The smaller weapons tend to be using far smaller (and thus lighter) rounds at 1.25 to 3km/s, depending on the weapon. To power a 32mm coilgun that flings something on the order of 10kg rounds at 3km/s, that would take a lot of electricity, requiring reactors that are impossible to fit within a vehicle even with using alternative fuels and ultratech forcefield modifier rules.

EDIT: the most powerful weapon can send metric ton projectiles at 10km/s and is able to reach 20 megameters.