Steve Jackson Games Forums - View Single Post - [Spaceships] Houserule: Variable Speed EM guns

kreios · 05-04-2016, 12:06 PM

Spaceships 3 gives an electromagnetic gun a ballistic impulse of one mile per second, or 1.5km/s. That's pretty low, and I'd like to increase the speed a bit.

This is, of course, easily done.

But I'd also like to be able to differentiate between guns firing large shells at low speed, and firing small shells at high speed.

Therefore, I've been thinking about introducing the following features for electromagnetic guns:

- Small Projectile
This gun fires a smaller-than-usual projectile, at only 1/4th of the mass, but at double the speed. Look up the corresponding change in caliber in SS1:47. This changes damage and quadruples available ammunition. In the advanced combat system, double ballistic impulse. In the basic combat system, double minimum velocity.

- Very Small Projectile
This gun fires a very small projectile, at only 1/16th of the mass, but at four times the speed. Look up the corresponding change in caliber in SS1:47. This changes damage and multiplies available ammunition by 16. In the advanced combat system, quadruple ballistic impulse. In the basic combat system, quadruple minimum velocity.

Why would you ever choose a smaller projectile?

Let's look at a SM+6 major battery 12cm electromagnetic gun. This gives us a dDamage of 6dx3.
The corresponding VSP gun is 5cm for 7d dDamage. Both get (probably) multiplied by their corresponding muzzle velocity. In the advanced combat system, this is 4 for the normal-sized gun, and 16 for the VSP gun. In the end, you're therefore talking about 6dx12 vs 6dx18 damage, an increase of 50%. It also gives you a higher muzzle velocity, meaning less time for the enemy to evade and more possible target vectors.

Why would you ever choose a larger projectile?

Let's take the Predator AKV from spaceships 8:12. It sports an acceleration of 0.3G and 20mps of fuel. If you give it an hour to accelerate, it's going to end up with 7mps relative velocity. Meaning our normal gun ends up doing 6dx82, and our other gun 6dx100.

Conclusion: Choose the larger gun if you're expecting many high-speed passes.

You might also keep the ammo constant, reasoning that some additional systems take more space. Makes the math easier.

05-04-2016, 12:06 PM	#1
kreios Join Date: Jul 2013	[Spaceships] Houserule: Variable Speed EM guns Spaceships 3 gives an electromagnetic gun a ballistic impulse of one mile per second, or 1.5km/s. That's pretty low, and I'd like to increase the speed a bit. This is, of course, easily done. But I'd also like to be able to differentiate between guns firing large shells at low speed, and firing small shells at high speed. Therefore, I've been thinking about introducing the following features for electromagnetic guns: - Small Projectile This gun fires a smaller-than-usual projectile, at only 1/4th of the mass, but at double the speed. Look up the corresponding change in caliber in SS1:47. This changes damage and quadruples available ammunition. In the advanced combat system, double ballistic impulse. In the basic combat system, double minimum velocity. - Very Small Projectile This gun fires a very small projectile, at only 1/16th of the mass, but at four times the speed. Look up the corresponding change in caliber in SS1:47. This changes damage and multiplies available ammunition by 16. In the advanced combat system, quadruple ballistic impulse. In the basic combat system, quadruple minimum velocity. Why would you ever choose a smaller projectile? Let's look at a SM+6 major battery 12cm electromagnetic gun. This gives us a dDamage of 6dx3. The corresponding VSP gun is 5cm for 7d dDamage. Both get (probably) multiplied by their corresponding muzzle velocity. In the advanced combat system, this is 4 for the normal-sized gun, and 16 for the VSP gun. In the end, you're therefore talking about 6dx12 vs 6dx18 damage, an increase of 50%. It also gives you a higher muzzle velocity, meaning less time for the enemy to evade and more possible target vectors. Why would you ever choose a larger projectile? Let's take the Predator AKV from spaceships 8:12. It sports an acceleration of 0.3G and 20mps of fuel. If you give it an hour to accelerate, it's going to end up with 7mps relative velocity. Meaning our normal gun ends up doing 6dx82, and our other gun 6dx100. Conclusion: Choose the larger gun if you're expecting many high-speed passes. You might also keep the ammo constant, reasoning that some additional systems take more space. Makes the math easier. Last edited by kreios; 05-04-2016 at 12:28 PM. Reason: Wrong numbers.