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Old 04-15-2018, 05:50 AM   #21
Polydamas
 
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Default Re: [Spaceships] Missile shield vs. ramming: two questions

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Originally Posted by Agemegos View Post
The OP didn't actually express a thought about force screens: the "Missile Shield" setting switch to which he referred is an optional rule regarding defensive fire by beam weapons against ballistic warheads and ramming ships. It's in GURPS Spaceships 3 on page 35.
Ok. I do not have money to buy any of the later volumes in Spaceships, and in my view for questions like this, it is always better to start with the real world ("on the back of an envelope, how would large spaceships work?") and worry about how to model it later.

Two common phenomena in naval architecture are big for the sake of big ("mine is bigger than yours!") and ships which have to serve multiple functions (the galleons of the Indes were treasure transports and armed to fight off filthy heretical pirates; an American aircraft carrier is a base for land operations and a weapon of naval warfare). Both can be reasons why there are ships bigger than a rational in-game analysis would justify, let alone our amateur analysis through the foggy mirror of the rules on a lazy Sunday.
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Old 04-15-2018, 06:00 AM   #22
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Default Re: [Spaceships] Missile shield vs. ramming: two questions

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Originally Posted by Michael Thayne View Post
As for the big gun, that can be overwhelmed by sheer numbers.
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.

You also asked about defending such large ships against missiles and ramming. Though holding the launching ships beyond X range with the Big Gun is a start on that, you're right that the Big Gun can be swarmed. So I suggest a point defence with high rate of fire, and the use of the "Missile Shield" setting switch. Details remain to be worked out: perhaps a weapon system split into three SM +11 systems: one SM+11 tertiary battery of thirty VRF improved lasers (improved UV lasers at TL 11) for dealing 3D damage to each of 6,000 unarmoured warheads/turn out to S/L range, one SM +11 secondary battery of 10 RF UV lasers (improved at TL 11) dealing 2D5 (2) to each of 100 (200 at TL 11) SM +4 or smaller fighters or KKVs per turn, out to L range, and a medium battery of three RF UV or x-ray lasers doing 6D5 (2 or 5) to each of three cheeky pests per turn that have armour on them, out to range L, and useful fire against light targets trying to close from beyond-X to L. It's not immune to everything, but any swarm of warheads or KKVs launched from beyond the range of its Big Gun is going to have to run a hell of gauntlet, especially if you keep down to limited superscience in drive performance.

If attackers build KKV with massive plugs of hardened armour on their front sections, deploy large ships in pairs, or with escorts, that can pour rapid fire at the sides of closing KKVs.
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Last edited by Agemegos; 04-15-2018 at 06:05 AM.
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Old 04-15-2018, 06:33 AM   #23
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Default Re: [Spaceships] Missile shield vs. ramming: two questions

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.
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Old 04-15-2018, 06:41 AM   #24
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Default Re: [Spaceships] Missile shield vs. ramming: two questions

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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.
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Old 04-15-2018, 07:00 AM   #25
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Default Re: [Spaceships] Missile shield vs. ramming: two questions

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%).
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Old 04-15-2018, 09:17 AM   #26
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Default Re: [Spaceships] Missile shield vs. ramming: two questions

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Originally Posted by Polydamas View Post
Ok. I do not have money to buy any of the later volumes in Spaceships, and in my view for questions like this, it is always better to start with the real world ("on the back of an envelope, how would large spaceships work?") and worry about how to model it later.
We don't really have "the real world", though, so coming up with a plausible model and seeing what consequences it has can be helpful. And tabletop RPGs are arguably the best model we have–computer games have advantages for modeling space combat, but can suffer from AIs that use very, very stupid tactics.

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Originally Posted by Polydamas View Post
Two common phenomena in naval architecture are big for the sake of big ("mine is bigger than yours!") and ships which have to serve multiple functions (the galleons of the Indes were treasure transports and armed to fight off filthy heretical pirates; an American aircraft carrier is a base for land operations and a weapon of naval warfare). Both can be reasons why there are ships bigger than a rational in-game analysis would justify, let alone our amateur analysis through the foggy mirror of the rules on a lazy Sunday.
"Big for the sake of big" only gets you so far, I think. If the rationally optimized warship size is SM+8, the biggest one or two superpowers might build some SM+10 ships, but even then the backbone of their fleet will still probably be SM+8.

Less sure about the multi-role thing. It would be interesting to stat out a multi-role ship under the Spaceships rules, where each role would only justify say a SM+8 ship. How big could such a ship get? Not sure it would get more than 10x larger than the "single role" ship.

Last edited by Michael Thayne; 04-15-2018 at 09:23 AM. Reason: Fixed tag error
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Old 04-15-2018, 09:23 AM   #27
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Default Re: [Spaceships] Missile shield vs. ramming: two questions

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Originally Posted by Agemegos View Post
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.
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Old 04-15-2018, 09:33 AM   #28
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Default Re: [Spaceships] Missile shield vs. ramming: two questions

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Originally Posted by Michael Thayne View Post
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.
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Old 04-15-2018, 09:37 AM   #29
Michael Thayne
 
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Default Re: [Spaceships] Missile shield vs. ramming: two questions

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Originally Posted by weby View Post
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.
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Old 04-15-2018, 09:50 AM   #30
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Default Re: [Spaceships] Missile shield vs. ramming: two questions

If you use "HP and Weight: An Alternative Approach" from the same Pyramid issue as "The Square Root of Destruction", and round up generously in in canon Spaceships style, you might get an HP progression like this:

SM+4: 30 dHP
SM+5: 50 dHP
SM+6: 100 dHP
SM+7: 150 dHP
SM+8: 300 dHP

Still not sure about the warhead damage progression.
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