[house rule] Quick RoF Fix question

[apoc527]

Originally Posted by Anthony

The problem with fixing ROF is that it winds up demonstrating just how broken damage is, because it makes it a lot easier to hit that giant object with enough really really tiny hits to disintegrate it.

That tends to be less of an issue in Spaceships, where DR scales so much with SM that a whole lot of really tiny hits isn't likely to do much. And with any weapon that CAN hurt the ship, it's generally more believeable to me.

Once again, that general objection is largely one of theory--if it ever comes up in play to the point where it actually bothers me, then I'll consider the problem. Otherwise, it's a textbook case of "well, it's broken because on an infinite featureless plane with only 2 fighters..."

[Ulzgoroth]

Originally Posted by apoc527

That tends to be less of an issue in Spaceships, where DR scales so much with SM that a whole lot of really tiny hits isn't likely to do much. And with any weapon that CAN hurt the ship, it's generally more believeable to me.

Once again, that general objection is largely one of theory--if it ever comes up in play to the point where it actually bothers me, then I'll consider the problem. Otherwise, it's a textbook case of "well, it's broken because on an infinite featureless plane with only 2 fighters..."

DR scales up, but not every ship has heavy slabs of the finest protection. Civilian craft can reasonably be built with some or even all sections entirely lacking armor. (Though most Spaceships writeups won't do so.)

Consider the 300,000 ton Von Braun class station from Transhuman Spacecraft. It's SM+13, with one system of unhardened steel per section for dDR30. Struck with a 3 GJ UV laser, it loses about 90 dHP out of 500 and has one system disabled. If instead it's hit by a 30 MJ improved VRF laser and takes 100 hits (out of 200), it loses something like 600 dHP...

[ericbsmith]

Originally Posted by Ulzgoroth

Consider the 300,000 ton Von Braun class station from Transhuman Spacecraft. It's SM+13, with one system of unhardened steel per section for dDR30. Struck with a 3 GJ UV laser, it loses about 90 dHP out of 500 and has one system disabled. If instead it's hit by a 30 MJ improved VRF laser and takes 100 hits (out of 200), it loses something like 600 dHP...

Note that in order to do that it significantly limits it's range. A 3GJ UV Laser has a range of L/X (7,000/20,000 miles), and can do reasonable damage beyond it's 7,000 mile half-dam range (damage drops from 90 dHP to 37 dHP). a 30MJ Laser has range S/L (1,500/5,000 miles) and can do no significant damage beyond it's half-dam range to a ship/station with dDR30 (average damage drops to 10.5 dHP, which is below the halved dDR of 15).

Your example also begins to slip if you change any of the variables even a little. Drop the UV Laser's base size by -1 SM or reduce the Mount size to the next smaller (going from 3GJ to 1GJ) or increase the armor from Steel to Light Alloy (giving 50 dDR instead of 30dDR) and the VRF UV Laser's average damage drops to 0 no matter how many hits it scores. So, yeah, there will be certain windows where damage may increase dramatically but for many others going to RF or VRF will mean doing 0 damage to your target, even if the target is relatively lightly armored.

So basically, extremely high RoF only works to your advantage if you're shooting at tin cans; and I'm not sure that that is a serious problem. Tin cans also get obliterated by high damage low RoF weapons, it just takes slightly longer.

[mlangsdorf]

Originally Posted by JP42

Did you ever see the far less aggressive "use the Speed/Range table" option that, I think it was Doug, came up with?

I think there's two versions of that rule.

There's my simple version: your RoF bonus is the size modifier for the number of shots fire, minimum bonus of 0. So 2 shots fired is +0, 3 is +1, 30 is +7, and so forth. It's not inherently better than the normal table, but it's one less table to have to reference.

I presume Doug's rule would be that your number of shots hit scales with the table? So if your Margin of Recoil is 0 you hit with 1 shot, if its 1 you hit with 2, 4 you hit with 7, 11 you hit with 100, and so forth.

It's another good approach but it makes my brain hurt to explain and I'd have to draw up some charts to make sure that it doesn't have any funky effects.

I think the two systems, taken together, would guarantee that you never hit with a higher percentage of your shots just for firing more bullets. But again, I'll have to do some tablework today to prove it.

[lexington]

Originally Posted by Ulzgoroth

Consider the 300,000 ton Von Braun class station from Transhuman Spacecraft. It's SM+13, with one system of unhardened steel per section for dDR30. Struck with a 3 GJ UV laser, it loses about 90 dHP out of 500 and has one system disabled. If instead it's hit by a 30 MJ improved VRF laser and takes 100 hits (out of 200), it loses something like 600 dHP...

Is the station supposed to be inviolate or something? Transhuman Space is a fairly realistic setting, IIRC, so stations being extremely vulnerable could be the intention.

[vierasmarius]

Originally Posted by lexington

Is the station supposed to be inviolate or something? Transhuman Space is a fairly realistic setting, IIRC, so stations being extremely vulnerable could be the intention.

The problem is not that it's vulnerable to attack, the problem is that it takes so much more damage from a rapid-fire weapon compared to a single-shot one. It's the same problem folks have with wooden age-of-sail ships being sunk by a single volley of musket fire, or modern carriers being gutted by a few bursts from a gatling gun. I suppose it's an inevitable problem we run into when we try to fix the wonky Rapid Fire rules: accumulative HP damage grossly exaggerates the danger of multiple small injuries compared to a single large one. But that's a subject that's already been pecked to death in a thousand other threads.

[mlangsdorf]

Originally Posted by JP42

Did you ever see the far less aggressive "use the Speed/Range table" option that, I think it was Doug, came up with?

I'm still not sure what you meant, but I ran with the idea and came up with something that I think is really elegant.

Size Modifiers Rapid Fire System

GURPS has never had a very satisfactory set of rules for rapid fire. The original system in 2e failed to scale at all for weapons with high rates of fire; the revised system in 2e and 3e required too many table look-ups, too many die rolls, and allowed for insanely high numbers of hits; the current version in 4e is fairly playable, but weapons with high rates of fire still get too few hits. There has to be a better solution.

Fortunately, there is. The Size Modifiers Rapid Fire system uses the same base mechanics as the 4e system, so it's a single roll to resolve all the shots fire, but it replaces the clunky and unmemorable Rate of Fire bonus table with the well-known and formulaic Size/Range modifier table. In doing so, it also creates a system that ensures that the same to hit roll will produce about the same percentage of shots on the target for weapons of the same recoil, no matter how many shots are fired.

The Size Modifier Rapid Fire system uses the same rules as Rapid Fire on B373 until you get to the RoF Bonus to Hit chart. Instead of looking the bonus up on that chart, look up the number of shots fired on the Size Modifier chart and use that bonus instead.

Example: Ted is firing an M-16 with RoF12 at full auto. 12 is more than 10 and less than 15, so Ted would get a +4 RoF bonus. If Ted were firing his semi-automatic shotgun with RoF 3x9, he would be firing a net 27 shots, for a +6 RoF bonus.

Calculate the Margin of Success for the attack normally, and then divide by the weapon's Recoil value to the get the Margin of Recoil. Subtract 1 from the Margin of Recoil and look up that bonus on the Size Modifier chart. The corresponding size measurement is the number of bullets that hit, up to the total number of bullets fired and to a minimum of 1.

Example: Firing an M-16 at RoF12, Ted makes the roll by 4. An M-16 has Rcl 2, so Ted's Margin of Recoil is 2. Subtracting 1 from 2, Ted gets a +1, which means 3 bullets hit. Had Ted made the roll by 0, his Margin of Recoil would have been 0, and he still would have hit with 1 bullet.

Example: Firing the shotgun, Ted makes the roll by 6. The shotgun has Rcl 1, so Ted's Margin of Recoil is 6. Subtracting 1 from 6, Ted gets a +5, which means 15 bullets hit. If Ted had made the roll by 8, he would have hit by all 27 bullets.

The Size Modifiers Rapid Fire System is elegant in three ways: it replaces an arbitrary table look-up with a look-up against a well-known and formulaic table; it scales up with the number of shots fired; and it ensures that firing more shots doesn't mean that a greater percentage of them hit.

There's a handle table of results by Recoil value on my blog.

[Ulzgoroth]

Here's a question: how do you have it interact with dodge?

If you don't change those rules, this means that high-RoF attacks can easily become quite impossible to fully evade, and the normal relationship between dodge and shooter skill is undone.

But if you want to keep that relation as-is, instead of subtracting MoS+1 from the number of hits on a successful dodge, subtract MoS+1 from the Margin of Recoil of the attack. And if the result is negative, the attack is entirely evaded.

[Anthony]

Actually, something I've been pondering based on the concept of adding size modifiers to weapons (see here) is to roll damage a maximum of some fixed number, and then additional successes count as bonuses to the size of the weapon, representing multiple hits, with a cap based on number of shots fired. A typical bonus would be:

Make attack roll, +(RSM for shots fired +2)/Rcl. Calculate MOS, and halve; treat values of less than 1 as 1. This is your (insert keyword here).
Cap at (RSM for shots fired +2).
Subtract (1 + amount by which defense roll was made).
If result is 1-3, roll that many hits.
If result is 4+, roll 4 hits, at +(result-4) to SM.

Thus, a 100RB from a minigun (Rcl 1) would get +12, and success by 24 would hit the cap (+12), and would be resolved as 3 hits at +9 to SM. If a minigun is normally a SM 0 attack, and you're shooting at a SM 6 container ship (HP 200), you would normally have a wounding modifier of 1/10, meaning each 6d attack averages 2 hits (expected damage from 100 hits: ~200; actually about 165 due to hits doing 19 or less rounding down). Instead, we roll 3 6d attacks, but relative SM goes from -6 to +2, for a x3 wounding multiplier, and expected damage is 4 * 21 * 2 = 168.

[Ulzgoroth]

I don't like dealing with the damage scaling issue there, since it is a problem with any source of many hits, not specifically with ones mediated through the RoF mechanic.