Railguns

the-red-scare · 02-02-2021, 03:32 PM

The space railguns are weird, man.

In Deep Beyond they are described as extremely-long barreled 155mm guns, and the weight and volume match building the same weapon in VE2 at 3e TL9. Now if we just built the weapon normally in VE2, it would do 744d damage with a 140 lb. projectile and draw 840 MJ per shot. 0.1 space of ammunition would hold 53 shots.

The Deep Beyond weapon does 3,000d damage (6dx(5+RV) cDAM) with a 22 lb. "burst" and draws 1,700 MJ per burst. 0.1 space of ammunition holds 26 bursts. Penetrating damage is then multiplied by 10 to account for the fact that a "shot" is several rounds. It appears shot and burst are interchangable, but it never says specifically.

The text says it fires at more than 10 mps, a good ~5x faster than the standard VE2 coilguns appear to fire. And that's fine, it helps explain a lot. For example, 22 lb. at 10 mps has about 1,300 MJ of kinetic energy, so 1,700 MJ is reasonable accounting for waste heat. We just assume they have more energy-dense rail designs than VE2 uses.

But the weirdness remains. I can conceive of math and projectile design that would give a 22 lb./10 mps shot 3,000d of damage, but that 22 lb. is actually at least ten rounds that each do 3,000d damage. That seems wildly out of scale unless they're going way faster than 10 mps, but that would blow up the energy figure.

Then there's ammunition massing 0.28 tons and taking up 0.1 space. That is a density of 0.18 g/cc, compared to something like tungsten at 19 g/cc. The railgun is practically firing balsa wood shells. Interestingly, if we drop the decimal and call it 28 tons, the density is 18 g/cc and it makes perfect sense. But that throws everything else off.

I suspect there was a math error somewhere that cascaded, but where? What should the ammunition and burst situation really be?

AlexanderHowl · 02-02-2021, 05:26 PM

THS is unrealistically generous to spacecraft, especially when it comes to combat. In general, I would use Spaceships instead, with the 4e conversion. The same railgun in 4e would deal 6d×40(2) d-damage (using 16cm is a substitute for 155mm), which is a lot more reasonable (bursts give +4 to hit, not bonus damage), and each round weighs 100 lbs and costs $5,000.

the-red-scare · 02-02-2021, 06:34 PM

Sure, I don’t really plan to use the railgun. I just want to understand the intention behind it. For, like, fun.

02-02-2021, 03:32 PM	#1
the-red-scare Join Date: Sep 2014	Railguns The space railguns are weird, man. In Deep Beyond they are described as extremely-long barreled 155mm guns, and the weight and volume match building the same weapon in VE2 at 3e TL9. Now if we just built the weapon normally in VE2, it would do 744d damage with a 140 lb. projectile and draw 840 MJ per shot. 0.1 space of ammunition would hold 53 shots. The Deep Beyond weapon does 3,000d damage (6dx(5+RV) cDAM) with a 22 lb. "burst" and draws 1,700 MJ per burst. 0.1 space of ammunition holds 26 bursts. Penetrating damage is then multiplied by 10 to account for the fact that a "shot" is several rounds. It appears shot and burst are interchangable, but it never says specifically. The text says it fires at more than 10 mps, a good ~5x faster than the standard VE2 coilguns appear to fire. And that's fine, it helps explain a lot. For example, 22 lb. at 10 mps has about 1,300 MJ of kinetic energy, so 1,700 MJ is reasonable accounting for waste heat. We just assume they have more energy-dense rail designs than VE2 uses. But the weirdness remains. I can conceive of math and projectile design that would give a 22 lb./10 mps shot 3,000d of damage, but that 22 lb. is actually at least ten rounds that each do 3,000d damage. That seems wildly out of scale unless they're going way faster than 10 mps, but that would blow up the energy figure. Then there's ammunition massing 0.28 tons and taking up 0.1 space. That is a density of 0.18 g/cc, compared to something like tungsten at 19 g/cc. The railgun is practically firing balsa wood shells. Interestingly, if we drop the decimal and call it 28 tons, the density is 18 g/cc and it makes perfect sense. But that throws everything else off. I suspect there was a math error somewhere that cascaded, but where? What should the ammunition and burst situation really be?

02-02-2021, 05:26 PM	#2
AlexanderHowl Join Date: Feb 2016	Re: Railguns THS is unrealistically generous to spacecraft, especially when it comes to combat. In general, I would use Spaceships instead, with the 4e conversion. The same railgun in 4e would deal 6d×40(2) d-damage (using 16cm is a substitute for 155mm), which is a lot more reasonable (bursts give +4 to hit, not bonus damage), and each round weighs 100 lbs and costs $5,000.

02-02-2021, 06:34 PM	#3
the-red-scare Join Date: Sep 2014	Re: Railguns Sure, I don’t really plan to use the railgun. I just want to understand the intention behind it. For, like, fun.