[Spaceships] Missile shield vs. ramming: two questions

[Agemegos]

Spaceships 8 (page 21) offers optical Phased Array lasers at TL11 and UV lasers at TL12. Only major batteries are available, and at TL11 they are only available as fixed mounts, but they can switch to rapid-fire or very-rapid-fire at will. They even function as LIDAR.

If you have TL12 (or TL 11 and play games with smaller-systems) you can equip an SM +12 ship with a phased array turret (or an SM +11 phased array in each hull section) that is a very versatile defensive weapon.

[Anaraxes]

Originally Posted by Agemegos

You didn't mention range, but it can be significant.

Also fits the "thoughtful aping of naval combat" mentioned in the OP. A chief advantage of 20th century big battleship guns wasn't just penetration versus armor or explosive power, but also greater range.

[weby]

First: Gurps HP rules are broken for large structures/vehicles. They are much harder to destroy than the cube root gives.

And related: In spaceships the beam weapon damage scales with cube root too to keep the damage scaling same as HP, but missiles and ramming do not.

The simple solution to that is: Use square root for both damage and object hitpoints. Square root is closer to real effect. This will both make beam weapons more effective against smaller targets and make larger targets tougher.

The damage square root is proposed in "The Square Root of Destruction" pyramid 3-34 page 9.

Second: Kinetic weapons are more effective due to the ability to get high speeds at higher TLs. This one is realistic but can be unsatisfying if you want large ships to survive.

The easiest solution to that is to use super science in the form of Force Screens that are silly good against kinetic threats. As example Vorsigan saga gives their Force Screens half normal dDR vs beams but fifty times normal dDR vs kinetics(so 100 times better than vs beams).

Alternative solutions include allowing smaller batteries on larger ships and not use rapid fire rules for massed batteries. Combining this with tactical combat where you have time to attack the incoming missile multiple times.

As example at TL 10, you cannot have more than DR 30 hardened as front armor and with The Square Root of Destruction a 30mj laser with 2d*10 will penetrate it easily. The battery weights 15 tons and needs 7.5 tons fusion power plant, so by using 2.25 times the drone mass(and remember that the attacker will likely use 1 2/3 times the mass to include the vehicle bays) you will get quite many shots at the drones(20+), with likely 2-3 hits needed to neutralize. So having say 1/4 the number of expected drones in defensive weapons should be enough. Under this system the automatic misses do not matter as you get so many attacks.

Alternative to beam weapon based defense is to use massed small missiles. Even a small missile will do devastating damage. Use massed Striker Missiles (UT 168) as a last ditch defense. No small target cannot have the armor to stop a 100mm High Explosive Multi-Purpose round with an effective dDR penetration of 126 against a hardened armor target(252 normal) and the missile weights only 17 lb and is a smart weapon so is independently targeting and make separate attack rolls. So launching 2 000(17 tons) to counter a 100 drone attack(1000 tons) is definitely feasible close defense. That gives 20 tries for each incoming drone by using a minimal part of the drone mass(1.7%).

[Michael Thayne]

Originally Posted by weby

First: Gurps HP rules are broken for large structures/vehicles. They are much harder to destroy than the cube root gives.

And related: In spaceships the beam weapon damage scales with cube root too to keep the damage scaling same as HP, but missiles and ramming do not.

The simple solution to that is: Use square root for both damage and object hitpoints. Square root is closer to real effect. This will both make beam weapons more effective against smaller targets and make larger targets tougher.

The damage square root is proposed in "The Square Root of Destruction" pyramid 3-34 page 9.

I'll think about this. One wrinkle: right now, kinetic damage for missiles and shells is weirdly based on cube root of mass, so if you did this really consistently you'd want to redo the "Conventional Warhead Damage Table" from Spaceships p. 68. Which isn't an argument against it, it might just take some extra work.

[Michael Thayne]

Originally Posted by Agemegos

You asked two questions. I'm sorry that I was not more clear about which one I was answering where.

"Why build big ships?" you asked, and listed some points about armour ratings and beam weapon damage. You didn't mention range, but it can be significant. Big ships carry big objective mirrors and can therefore focus a weapon at ranges where a smaller ship cannot effectively return fire. In GURPS Spaceships that effect makes a tactical difference up to a 100 GJ UV laser or X-ray laser, for which you need an SM +12 ship with a spinal mount or SM +15 with a major battery. That's another reason to build ships larger than SM +9.

I think the issue is how range scales. A 30,000x increase in mass (and more importantly, cost!) only yields a 10x increase in range. So I'm not super-excited about this strategy. It's maybe compelling when you're designing something to assault space stations, which can't close range.

[Fred Brackin]

Originally Posted by Michael Thayne

I think the issue is how range scales. A 30,000x increase in mass (and more importantly, cost!) only yields a 10x increase in range. So I'm not super-excited about this strategy. It's maybe compelling when you're designing something to assault space stations, which can't close range.

Your theories about this do not match up with my experience of Spaceships battles. My experience is that superior range wins hands down and quickly too.

The only time I have seen drone saturation work was against a space station that could not get out of the way v. a massive number of targets that had a closing velocity of 70 miles per second. This speed also allowed the vessels carrying the drones to stay out of range.

Hardening the drones played no role. If you're going to saturate the target's defenses adding missile launchers instead of armor is a much better deal.

[Agemegos]

Originally Posted by Michael Thayne

I think the issue is how range scales. A 30,000x increase in mass (and more importantly, cost!) only yields a 10x increase in range. So I'm not super-excited about this strategy.

What ought range to go with, realistically? Naively (i.e. ignoring the engineering of pointing the things) the diameter of the objectives ought to go with [strikethrough]the square of[/strikethrough] ship length. And spot size can go with objective diameter where the weapon is constrained by beam intensity on the objective mirror. Which means that range ought to go with the 2/3 power of ship mass, divided by wavelength.

A factor of 30,000 in ship mass ought to deliver a factor of about 900 in range.

[Agemegos]

Originally Posted by Michael Thayne

The missile shield design switch from Spaceships 3 seems essential here, to stop large warships from being missile bait. But what about ramming? A couple things are unclear to me. First, if your RoF is higher than the number of ramming ships, do you get one hit per ramming ship, or one hit per point of RoF, which can be divided freely among attacking ships? I can't quite tell from the wording of the rule ("Beam weapons that are assigned to point defense may therefore automatically hit a number of incoming ballistic weapons (or ramming spacecraft) up to their maximum rate of fire.")

I suggest that you read this rule in conjunction with "Spreading Fire" on SS1 p.58.

A gunner may choose to divide his shots
among different targets, either attacking multiple
targets, or firing at different parts of a single vessel.
All targets must be specified before rolling to
hit. It imposes an extra -2 penalty per different
target engaged (applied to all attack rolls) when
firing beams or guns, or a -1 penalty per target if
firing missiles. One attack roll is made for each
target.

So your gunner divides his RoF up among targets as he sees fit, and then each shot of group of shots fired at an "incoming ballistic weapon… (or ramming spacecraft)" is an automatic hit. "Automatic hit" as in "couldn't miss at any modifier" ought to mean that every round in the burst hit, because if you would have hit at, say, -10 and have Rcl 1 then you would have hit with ten rounds, right? It'd be foolish for an ease-of-use rules option to drastically reduce effectiveness.

[Refplace]

Originally Posted by Michael Thayne

The missile shield design switch from Spaceships 3 seems essential here, to stop large warships from being missile bait. But what about ramming? A couple things are unclear to me. First, if your RoF is higher than the number of ramming ships, do you get one hit per ramming ship, or one hit per point of RoF, which can be divided freely among attacking ships? I can't quite tell from the wording of the rule ("Beam weapons that are assigned to point defense may therefore automatically hit a number of incoming ballistic weapons (or ramming spacecraft) up to their maximum rate of fire.")

I would say one hit per ROF divided up however you want. But roll damage after assigning targets.

Originally Posted by Michael Thayne

Second, would it be reasonable to use the "missile shield" rules not just for beams but also missiles?

Unless the incoming targets have ECM or are programed/guided to evade and they are far enough away I would say yes.
But there should probably be a minimum firing distance.
They key here though is t specifies beams, not guns as usable for the option. Presumably because the beams move so fast the missiles are effectively standing still. Point Defense missiles have terminal guidance so might be able to make up for that, especially if not dealing with ECM or evasive tactics.

[Polydamas]

Originally Posted by Michael Thayne

I'm trying to figure out how to build a space combat paradigm where large warships make logical sense, as opposed to being the result of mindless aping of naval warfare. Not that we don't want to ape naval warfare, we just want to do so in a thoughtful way. Here "large" = SM+9 at a minimum, or ideally SM+10 or higher.

The basic problem here is that cost scales with volume, while damage, armor, and HP scale with length. The main thing that large warships have going for them is that (1) they can potentially have enough DR to be immune to beam attacks from smaller ships (2) they can have beam weapons powerful enough to penetrate such armor on enemy craft. Unfortunately, this logic doesn't apply so much to kinetic attacks, because kinetic attacks can do incredible amounts of damage, especially when using the tactical combat rules where you aren't arbitrarily limited to a scale-based velocity.

The missile shield design switch from Spaceships 3 seems essential here, to stop large warships from being missile bait. But what about ramming? A couple things are unclear to me. First, if your RoF is higher than the number of ramming ships, do you get one hit per ramming ship, or one hit per point of RoF, which can be divided freely among attacking ships? I can't quite tell from the wording of the rule ("Beam weapons that are assigned to point defense may therefore automatically hit a number of incoming ballistic weapons (or ramming spacecraft) up to their maximum rate of fire.")

Second, would it be reasonable to use the "missile shield" rules not just for beams but also missiles? It seems like this could be extremely helpful, because (1) dedicated suicide drones can have very heavy frontal armor, enough to bypass point-defense guns designed for unarmored missiles and (2) by the standard rules, a point-defense gunner has a minimum 5% miss chance. Point (2) means an SM+10 warship (weighing in at 10,000 tons) can easily be destroyed by a swarm of a dozen or so SM+4 drones (10 tons each).

It is always good to remember that game rules are only an approximation and that people in the setting make decisions based on their reality not the rules. The 'machine gun vs. HMS Victory' problem is a classic example.

There is a post from David Pulver around 2008 talking about how he might scale HP to better represent the properties of large vehicles in WW II and the Falklands. I think that your thoughts about force screens are on the right track: settings with many big ships, such as Star Trek or the Schlockverse, usually have some kind of 'force field' technology, and that can allow big ships with big power plants to shrug off attacks.

(Similarly, I don't know whether Spaceships assumes the kinds of armour arrangements which specialists talk about- many thin spaced plates and things like that- or the intuitive 'great solid hard masses' which 90% of gamers will envision).