[Spaceships] Point Defence and Missile questions

Flying Toaster · 02-10-2010, 03:26 PM

Hi all, new Gurps player here, and I have a couple of questions about the space combat system.

The first question is checking if I am running missiles and point defence correctly.

Let's assume 1 minute turns, and 2 ships. One ship, attacking with missiles, has a tertiary battery with 30 missile launchers, allowing it to launch 90 missiles per game turn (30 missiles, RoF 3 @ 1 min turns). The second ship, defending against the missiles, has a tertiary battery of 30 improved Very rapid fire lasers, giving it 600 shots per turret, or 9000 shots total.

From my reading of the rules, the 90 missiles count as a single salvo, and therefore roll a single attack roll, with every point under the to hit number giving an extra missile to hit (e.g. to hit number is 18, if a 10 is rolled 8 missiles hit). That seems fine by me.
My concern is the use of point defence: from my reading of the rules, each turret should be able to fire in point defence against the missile salvo, using its 600 shots to gain a rapid fire bonus to hit of +9, and each hit under the to hit number wiping out an extra missile (as with the missile hits). In a few playtests I've done, this results in all the missiles being wiped out easily, and also takes a while to do (potentially up to 30 rolls).
I tried giving the battery a single roll, using the rapid fire bonus for 9000 shots, and this worked, somewhat, but doesn't feel quite right. Does anyone have any suggestions or comments?

My second question is regarding missile damage. I am using 1 minute turns with 1,000 mile hexes. This means that when relative velocity modifiers are taken into account, a single missile from a tertiary mount on a SM +10 (32cm) ship can do around 90,000 damage. Calculations are: 6dx8 base damage x relative velocity (let's say 10) x scale factor (60) = average of 6 x 3.5 x 8 x 10 x 60 = 100,800 dDmg.
This seems rather high, and isn't the effect I want, so am I doing anything wrong? I tried a playtest using just the base missile damage, and this worked a bit better, especially if relative velocity is also removed from the missile accuracy calculations.

Thanks in advance for any answers.

Fred Brackin · 02-10-2010, 05:38 PM

Quote:

Originally Posted by Flying Toaster

I tried giving the battery a single roll, using the rapid fire bonus for 9000 shots, and this worked, somewhat, but doesn't feel quite right. Does anyone have any suggestions or comments?

Lumping the missiles together and then lumping the point defense together is how we did things in the playtest and I think it's the fair way to do things. Lumping is an arbitrary play convenience and not a reality simulation so you should do it symmetrically or not at all.

It does tend to produce binary results with total kills or nothing at all being separated by only small changes.

You're doing something weird about missile damage though. My copy of Spaceships makes damage a simple base damage times velocity in miles per second.

So that's 6Dx8 x 166.67 or just under 28,000 on average. Probably still a sure killer but your relative velocity is huge by any real world measure. Any shot that misses isn't stopping in this solar system unless it hits something else.

lexington · 02-10-2010, 05:55 PM

Quote:

Originally Posted by Flying Toaster

My second question is regarding missile damage. I am using 1 minute turns with 1,000 mile hexes. This means that when relative velocity modifiers are taken into account, a single missile from a tertiary mount on a SM +10 (32cm) ship can do around 90,000 damage. Calculations are: 6dx8 base damage x relative velocity (let's say 10) x scale factor (60) = average of 6 x 3.5 x 8 x 10 x 60 = 100,800 dDmg.
This seems rather high, and isn't the effect I want, so am I doing anything wrong? I tried a playtest using just the base missile damage, and this worked a bit better, especially if relative velocity is also removed from the missile accuracy calculations.

Thanks in advance for any answers.

What's a scale factor? That doesn't appear anywhere in my copy of Spaceships.

[edit] found it in Warships. Did you recalculate missile speeds? 10 one-thousand-mile hexes per minute isn't the same as 10mps.

Ulzgoroth · 02-10-2010, 07:41 PM

For the first, point defense is catastrophically broken as written. In every direction (note that you could have made those missile launchers into independent turrets). And apparently in the playtest, nobody used the rules in the book.

Also, the scale factor table is just plain wrong. Unless it's been changed since it read:

Code:

Scale Factor Table
Scales              10-mile hex 100-mile hex 1,000-mile hex
20-second turn 2                 20                200
1-minute turn   0.6              6                  60
3-minute turn   0.2              2                  20
10-minute turn  0.06             0.6                6

If not, it needs all values divided by 4.

Cernig · 02-10-2010, 09:05 PM

Quote:

point defense is catastrophically broken as written

Agreed.

Anyone got any decent - i.e. simple to understand, easily playable and moderately real-world believable - House Rules they'd like to share? If so, by all means PM me.

I'm especially interested in something that integrates ECM/ECCM too - which was partly fixed in Warships but still is too weak and isn't all that close to real-world effectiveness imho. (I've a House Rule based on quick contests and levelled ECM/ECCM that works for me and I've a hunch quick contests might help solve the whole PD problem in one integrated whole.)

lexington · 02-10-2010, 09:12 PM

Quote:

Originally Posted by Cernig

I'm especially interested in something that integrates ECM/ECCM too - which was partly fixed in Warships but still is too weak and isn't all that close to real-world effectiveness imho.

What real world deep space battles are you thinking of? Honestly I'm not entirely clear on how ECM is supposed to work at all.

Cernig · 02-10-2010, 11:26 PM

LOL Lexington. I was talking about modern naval/airborne ECM but you're right I didn't make that clear.

Apologies to those who know all the next bit, but a fuller explanation of modern electronic war might be in order.

ECM is jamming/spoofing/overloading the incoming missile's sensors, data communication and guidance packages or those of its launching/guiding vehicle by means of high powered electro-magnetic emissions (radio, microwave etc). ECCM uses frequency-agile datalinks, interference signals etc to prevent that happening and/or tries to jam/spoof/overload the other guys ECM before he can do it to you.

If a modern ECM aircraft were to light up its powerful ECM pods on the ground, every living thing within a few hundred yards would get cooked.

Understandably, modern militaries keep secret how effective their Electronic Combat systems are. But every major modern naval or air combatant has an ECM/ECCM suite and I presume they aren't there for show. The ALQ-161 suite on the B-1B bomber comprises 120 separate items, which weigh about 2500 kg. When its full jamming capacity is utilised, it consumes roughly 120 kW of power. It is designed to operate in a fully automatic mode, where the system receives, identifies, and jams threat radars instantaneously.

Quote:

High performance tactical jamming aircraft are a necessary part of any major air power and represent the most effective means of disrupting the control of the enemy's defensive system. Once that has occurred the individual SAM and AAA systems have no means of coordinating and concentrating their fire on specific targets. This renders them essentially ineffective when confronted by the onboard defensive jammers of the attacking strike aircraft.

Seems to me that should be worth more than a blanket -2 per system when applied to higher TL, multi-kiloton, spacecraft. And that such a blanket figure ignores the essential quick-contest nature of electronic combat.

Cernig · 02-10-2010, 11:51 PM

Nor do I think that Warships fixed the ECM problem. It introduced quick contests, but it assumes that ECCM is something you do with your sensor array, whereas ECCM should be another module like ECM. Both should also come in levels based on TL and size of warship which can either do contests automatically or be used to add to the operators skill for quick contests. IMHO, that would more capture the flavor of current ECM/ECCM tech extrapolated into the future. And all it does is reduce existing ECM effectiveness of +2 per module fitted. If the ECM wins big, it should cripple its enemies ability to fire effectively that turn - maybe even burn out sensors and other electronics. If ECCM wins big, ECM systems might be useless or even damaged.

ECM/ECCM warfare should also be a sizeable part of point defense. Those missiles are either guided by a data-link from the sensors of their launching ship, one from another ship, or by their own sensors. Meanwhile, on the other hand, the launcher's ECM is trying hard to cripple the sensors and datalinks controlling the target's PD fire. False target generation, sensor blinding, datalink disrupting and system burnouts should be important. I'd guess 40% of PD effectiveness should come from ECM/ECCM contests, about 60% from anti-missile fire, all other things being equal.

How to fix that, and then also fix the missile vs anti-missile equation so that it isn't all or nothing, while making it all easy and fast to use in play? I've no blessed clue right now, I admit. That's why I'm hoping someone else does.

Flying Toaster · 02-11-2010, 01:10 AM

Whoops! The relative velocity I'm using is from Warships, where it is base damage x speed in hexes x scale factor. Dividing the scale factor by 4 will help a lot, I think.

As an idea about ECM/ECCM, possibly declare the ECM module to be an EW (Electronic warfare) module (the B1B's EW suite seems to take about 1% of its mass, so a 5% system could be plausible). Then increase the base ECM modifier a bit, and perform a quick contest each turn to reduce it, with degree of success determining how much it's reduced by. Higher TL or larger ships could give bonuses.

Cernig · 02-11-2010, 10:13 PM

One thing about being a minor national security and foreign policy writer - you can sometimes find what you're looking for with some digging and some hints from knowledgeable people.

I've discovered that modern ECM systems, working un-opposed, can degrade missile accuracy by between 30 and 75% depending upon size, power, make etc. Obviously, ECCM can whittle that advantage away to nothing. And that a modern automatic point defense weapon can be expected to down the first missile it fires at about 60% of the time, degrading sharply if it has to switch and acquire new targets so that 5 or 6 missiles will pretty much always swamp a single PD gun. Again, attacker's ECM can sharply degrade that capability by up to 75%.

Anyone out there want to help build easy-to-play house rules to reflect this modern situation extrapolated forward into future ones?

02-10-2010, 03:26 PM	#1
Flying Toaster Join Date: Feb 2010	[Spaceships] Point Defence and Missile questions Hi all, new Gurps player here, and I have a couple of questions about the space combat system. The first question is checking if I am running missiles and point defence correctly. Let's assume 1 minute turns, and 2 ships. One ship, attacking with missiles, has a tertiary battery with 30 missile launchers, allowing it to launch 90 missiles per game turn (30 missiles, RoF 3 @ 1 min turns). The second ship, defending against the missiles, has a tertiary battery of 30 improved Very rapid fire lasers, giving it 600 shots per turret, or 9000 shots total. From my reading of the rules, the 90 missiles count as a single salvo, and therefore roll a single attack roll, with every point under the to hit number giving an extra missile to hit (e.g. to hit number is 18, if a 10 is rolled 8 missiles hit). That seems fine by me. My concern is the use of point defence: from my reading of the rules, each turret should be able to fire in point defence against the missile salvo, using its 600 shots to gain a rapid fire bonus to hit of +9, and each hit under the to hit number wiping out an extra missile (as with the missile hits). In a few playtests I've done, this results in all the missiles being wiped out easily, and also takes a while to do (potentially up to 30 rolls). I tried giving the battery a single roll, using the rapid fire bonus for 9000 shots, and this worked, somewhat, but doesn't feel quite right. Does anyone have any suggestions or comments? My second question is regarding missile damage. I am using 1 minute turns with 1,000 mile hexes. This means that when relative velocity modifiers are taken into account, a single missile from a tertiary mount on a SM +10 (32cm) ship can do around 90,000 damage. Calculations are: 6dx8 base damage x relative velocity (let's say 10) x scale factor (60) = average of 6 x 3.5 x 8 x 10 x 60 = 100,800 dDmg. This seems rather high, and isn't the effect I want, so am I doing anything wrong? I tried a playtest using just the base missile damage, and this worked a bit better, especially if relative velocity is also removed from the missile accuracy calculations. Thanks in advance for any answers.

02-10-2010, 07:41 PM	#4
Ulzgoroth Join Date: Jul 2008	Re: [Spaceships] Point Defence and Missile questions For the first, point defense is catastrophically broken as written. In every direction (note that you could have made those missile launchers into independent turrets). And apparently in the playtest, nobody used the rules in the book. Also, the scale factor table is just plain wrong. Unless it's been changed since it read: Code: Scale Factor Table Scales 10-mile hex 100-mile hex 1,000-mile hex 20-second turn 2 20 200 1-minute turn 0.6 6 60 3-minute turn 0.2 2 20 10-minute turn 0.06 0.6 6 If not, it needs all values divided by 4. __________________ I don't know any 3e, so there is no chance that I am talking about 3e rules by accident.

02-10-2010, 11:51 PM	#8
Cernig Join Date: Jun 2007 Location: Texas	Re: [Spaceships] Point Defence and Missile questions Nor do I think that Warships fixed the ECM problem. It introduced quick contests, but it assumes that ECCM is something you do with your sensor array, whereas ECCM should be another module like ECM. Both should also come in levels based on TL and size of warship which can either do contests automatically or be used to add to the operators skill for quick contests. IMHO, that would more capture the flavor of current ECM/ECCM tech extrapolated into the future. And all it does is reduce existing ECM effectiveness of +2 per module fitted. If the ECM wins big, it should cripple its enemies ability to fire effectively that turn - maybe even burn out sensors and other electronics. If ECCM wins big, ECM systems might be useless or even damaged. ECM/ECCM warfare should also be a sizeable part of point defense. Those missiles are either guided by a data-link from the sensors of their launching ship, one from another ship, or by their own sensors. Meanwhile, on the other hand, the launcher's ECM is trying hard to cripple the sensors and datalinks controlling the target's PD fire. False target generation, sensor blinding, datalink disrupting and system burnouts should be important. I'd guess 40% of PD effectiveness should come from ECM/ECCM contests, about 60% from anti-missile fire, all other things being equal. How to fix that, and then also fix the missile vs anti-missile equation so that it isn't all or nothing, while making it all easy and fast to use in play? I've no blessed clue right now, I admit. That's why I'm hoping someone else does.

02-11-2010, 01:10 AM	#9
Flying Toaster Join Date: Feb 2010	Re: [Spaceships] Point Defence and Missile questions Whoops! The relative velocity I'm using is from Warships, where it is base damage x speed in hexes x scale factor. Dividing the scale factor by 4 will help a lot, I think. As an idea about ECM/ECCM, possibly declare the ECM module to be an EW (Electronic warfare) module (the B1B's EW suite seems to take about 1% of its mass, so a 5% system could be plausible). Then increase the base ECM modifier a bit, and perform a quick contest each turn to reduce it, with degree of success determining how much it's reduced by. Higher TL or larger ships could give bonuses.

02-11-2010, 10:13 PM	#10
Cernig Join Date: Jun 2007 Location: Texas	Re: [Spaceships] Point Defence and Missile questions One thing about being a minor national security and foreign policy writer - you can sometimes find what you're looking for with some digging and some hints from knowledgeable people. I've discovered that modern ECM systems, working un-opposed, can degrade missile accuracy by between 30 and 75% depending upon size, power, make etc. Obviously, ECCM can whittle that advantage away to nothing. And that a modern automatic point defense weapon can be expected to down the first missile it fires at about 60% of the time, degrading sharply if it has to switch and acquire new targets so that 5 or 6 missiles will pretty much always swamp a single PD gun. Again, attacker's ECM can sharply degrade that capability by up to 75%. Anyone out there want to help build easy-to-play house rules to reflect this modern situation extrapolated forward into future ones?