Thursday, August 23, 2018

Dogfighting 2: Jet vs Tank

One thing I’ll need to handle if I get into fighters vs cap-ships, I need to see how high-speed craft work against slower, sea-bound craft, but I don’t have sea-bound craft that I can compare the standard TL 8 fighter to. However, I do have tanks. High-Tech has a TL 8 main battle tank, but I’m pretty sure I know how that fight will end, which is with a dead tank on turn one, because the fighter will get a missile lock, fire, and kill. The only real disadvantage is that the fighter isn’t carrying any missile that easily punches through armor, but the top of a tank is only DR 100, and the missile deals 200 damage; it wouldn’t necessarily be a one shot kill, but the tank sure wouldn’t be happy. Thus, I’d like to propose using the TL 9 “Light Battle Tank” from GURPS Ultra-Tech. It’s more advanced than the fighter, but at least it can fight back and make things interesting.

Surely,” I hear you say, “GURPS Action doesn’t handle things like a fighter jet ‘chasing’ a tank.” Oh, but it does! It calls this mobility pursuit. The fighter is able to operate on three dimensions and can treat the tank as static. Of course, it must pursue in ways that the tank cannot compensate for. Just chasing the tank over flat ground is not mobility pursuit, but if the tank must go over rough, rocky ground that the fighter can just soar over, then it becomes a mobility pursuit. Similarly, if things go bad for our fighter, it can use a mobility escape, simply climbing beyond the range of the tank.
It should be noted that the tank and a Psi-Wars capital ship aren’t precisely the same, because a fighter can’t use superior mobility against a capital ship, as both operate in three spatial dimensions, but we have some additional ways we can simulate it in Psi-Wars, if it comes to that.

The Craft

The fighter will be Maverick, once more: pilot-18, all other pertinent skills at 16. He’ll fly an advanced Viper (an “F-18”-ish craft).

Our tank will be a dangerous, experimental tank in the hands of some hyper-advanced criminal cartel. The Light Battle Tank (UT 226) comes with a tank cannon (which won’t be useful), a coaxial chaingun (which also won’t be useful), a “strike laser” which will be useful, and a rack of 10 missiles, which will also be useful. Among other things, it sports a tactical ESM (+1 to dodge if locked on). It has no radar or, despite its description, radar stealth. I am, however, going to borrow the Radar Stealth from the hover tank on the same page. At TL 9, this gives a -4 to radar, so we’re going to treat it, altogether, as ECM -4, for simplicity (we can argue it has thermal cloaking to prevent IR locks, etc).

The strike laser is on UT 116 and is, surprisingly, a TL 10 item on a TL 9 tank. Interesting. Let’s replace it with the Point Defense laser at TL 9, which weighs the same, just has halved damage. It has an accuracy of 18, and halved damage at farther than 9,000 yards (so, beyond visual). I’m not sure how it’ll handle “point defense.” I see no special rules anywhere, so for here, I propose we treat it like a parry. I might not use that rule for Psi-Wars, but we’ll use it here.

The Missiles are TMLs from UT 146. They have an accuracy of 3, and we’ll make them homing, but just treat them like the homing missiles from Dogfighting: they’re as vulnerable to ECM as any missile. Their minimum range is 3000 yards so, like the missiles from Dogfighting, they cannot hit closer than Distant, but can reach out to Beyond Visual. It’ll use proximity detonation HE rounds, so benefit from the +4 to hit, and will deal 6dx5 damage, which is less than the fighter’s missiles, but it’s also a smaller warhead (100mm vs ~160mm); the closeness in damage is no accident, as I used the TL 9 HE warhead as the base for my new missile. I could probably have worked out a more “realistic” version.

(The realistic version would use HMX from GURPS High-Tech, which has an REF of 1.7. If my calculations are correct, such a weapon would give 6dx7 cr ex, rather than the 6dx10 that I used; I could transition to this, but the LBT has a side/top DR of 200, which means it would be virtually impossible for our fighter to damage it).

The LBT can move at a top speed of 50 miles per hour, giving it a +6 to chase rolls.
The Tank is driven by the Claw, a nefarious agent up to no good; he has Gunnery and Artillery 18, and Drive (and all other pertinent skills) 16.

The Fight

Turn 1: Distant

Step 1: Quarry Chooses Maneuver

Step 2: Pursuer Chooses Maneuver

This is an interesting question, as our fighter really occupies a different scale than the tank does; this matters most for radar, as it’s much easier to pick up a jet, silhouetted by the sky, than it is to pick up a tank driving in a radar-noisy landscape. Nonetheless, we’re going to start with Maverick chasing the Claw, as the reverse is absurd, and Maverick wants to stop the Claw before he can get to some civilians and deal some real damage.
We’ll start at Distant, mainly because I don’t believe you could pick out a tank in cluttered terrain without visual confirmation, not well enough to target anyway, and I don’t have decent “sensor” rules yet, so we’ll go with this.

The Claw has some interesting options. He could Hide, which gives him a +0 due to the range involved, so he has a pretty good chance of pulling it off. This sort of makes sense: slip behind some trees and a jet-fighter cruising at mach 1 at high altitudes is going to have a pretty good chance of passing you by completely. Then you could pull out and “chase” the jet-fighter. However, since that sort of thing won’t be happening in space, and that’s really the sort of thing I want to understand, we’re not going to do that. Another good option is Attack. By stopping and taking time to aim a shot at the jet, our tank could do some real damage. I’m not going to do that either. Instead, the Claw chooses move, based on the rational that he doesn’t yet realize he’s under attack (he lacks radar, though perhaps his hyper-spectral sensors could pick up the jet, but is he even looking?) and he wants to reach his nefarious goal as soon as possible.

Maverick, of course, needs to remove this guy as quick as possible and chooses Move and Attack, firing off a missile. He’s not making a mobility pursuit, as he’s not actually cutting the Claw off in some unusual way.

Note: You can’t make mobility pursuits and attacks. Why not? Come to think of it, there’s a lot of maneuvers that look more like options. Couldn’t you do a Mobility Stunt Move and Attack, like your helicopter cuts off someone’s motorcycle while flying upside down and peppering the area with bullets? Or is that to much awesome for a single maneuver?

Step 3: Resolve Pursuer Rolls

Maverick gets to make his attack. He’s firing a missile, so he takes his:
  • Artillery 16
  • Accuracy 5
  • Target ECM -4
  • Target Speed (halved) -3
  • Target SM +5
So we need a 19 or less to hit. That ECM makes a difference, but not enough for its slow speed. Maverick rolls a 15, and hits.

The Claw gets notified the moment Maverick locks on (Tactical ESM), and begins to swear. He can dodge (he has a base dodge of 8, with a -2 from the tank’s handling, a +1 from combat reflexes, and a +1 from his tactical ESM, giving us a 8), or we can try point defense. If we treat that as a “parry” with gunnery, then we have a 9 + 3 + 1 +1 or 14, but I’m not sure this is the right approach: are all missiles equally easy to engage in point defense against? We have no rules I can find anywhere on point defense, so I don’t know what’s fair here. So, instead, let’s try a lame dodge. We need an 8 and we roll… a 9. So we’re hit. It’s a top hit (I can’t find where the rules say that its armor is located, but I’m going to assume the turret and front are DR 500, and tops and sides are 200). Maverick hits with 250 explosive damage, which means the tank takes 50 damage, out of it’s 150. That’s not enough to “stun” the vehicle, though it’ll temporarily have a -4 to its control rolls. It’s shaking and bouncing mercilessly, and the Claw’s ears are ringing, but he’s fine.

Note: the weaponry our fighter is carrying is just not strong enough to punch through armor. An air-to-surface missile might have something more like 6dx8(10) cr ex, which averages 160 damage and would punch through 1600 DR; the tank has DR 200, and is laminate with EMA, and thus has effectively 600 DR, which means it would take 100 damage from such a missile, on average, which is worse than what the air-to-air missile can do, but still isn’t a one-shot kill. Most of this is a technological disparity, though. An air-to-surface missile can generally kill a tank, and "fighter vs tank" is usually a terrible match-up for a tank.

Step 4: Resolve Quarry Rolls

No Rolls necessary

Step 5: Resolve Chase Contest

Maverick has a -2 from his move and attack, +14 from his speed, and +3 from his handling atop his skill 18, for a total of 33; he rolls an 11 and succeeds by 22. The Claw has +0 from his move, -4 from shock, -2 from handling, and +6 from speed with a drive of 16, for a total 16; he rolls a 3 and succeeds by 13, which is technically not enough, but it’s a critical success! C’mon!
Just based on results, Maverick could approach by a band, but let’s make the case that with a critical success, the Claw is able to somehow out maneuver him and stay just on the edges of Maverick’s approach. On average, though, we would expect Maverick to close a band at least once a turn, often two bands per turn.

Turn 2: Extreme; The Claw has 100/150 HP; Maverick has 5/6 missiles.

Step 1: Quarry Chooses Maneuver

The Claw is definitely the quarry, and running is futile, so we’re going to stop and Attack.

Step 2: Pursuer Chooses Maneuver

We rattled the tank last time. Another missile might get lucky again. Move and Attack.

Step 3: Resolve Pursuer Rolls

Maverick makes to make his attack. Our stats are largely the same as last time, but here they are again:
  • Artillery 16
  • Accuracy 5
  • Target ECM -4
  • Target Speed (halved) -0 (he’s static)
  • Target SM +5
So we need a 22 or less to hit, which means we’ll almost certainly hit. We roll a 10 and hit.
I don’t think I can make the case that our tank can dodge; this would be another good time to make a point defense attack; I sat down and hunted up some rules on this, and the only thing I could find was in Modular Mecha which gives point-defenses a skill of 13 or less. This is TL 10, so perhaps a TL 9 point Defense would be skill 12? If we do that, and roll an 11, then our point defense defeats the missile.

Note: Is this fair? I’m not sure. We really have no logic behind point defense, and it’s not something I’d include in Psi-Wars, but it would be nice to have some official rules behind it. The idea seems to be a wait and attack with an AI controlling the point defense, but would it aim? Do we care about range? Do we care about missile SM? How is this supposed to work? It’s not something I feel the need to dive too deep into, but I know it’s something a lot of people would like to see on a tactical (not space) scale of combat.

Incidentally, the damage it took last turn, does it still affect it this turn? I would say no, but then, I'm not really clear as to how shock should impact vehicles in chase scenes at all!

Step 4: Resolve Quarry Rolls

So, the Claw gets to make his attack. He can fire his Strike Laser (but if that was used as point defense, it is still an option?) or his missile. Given the ambiguity of the point defense, a missile would make more sense, but let’s see what the Strike Laser would look like.

For the Strike Laser:
  • Gunnery 18
  • ROF +0
  • Accuracy 18
  • Range -15 (Range + Speed = -17, if we wanted to be picky)
  • Target SM +5
We would need a 26 or less to hit, which is as close to a sure thing as we’re going to get. Lasers have absurd accuracy values; if we us the Psi-Wars reduced blaster accuracy, we drop down to 17, which is a much more interesting value.

For the missile:
  • Artillery 18
  • Accuracy 6
  • Target ECM -3
  • Target Speed (halved) -7
  • Target SM +5
This brings us to a 19 or less.
Either way, we roll 10 and hit. That leaves Maverick to dodge; he has a skill of 18, so a base dodge of 9, with a handling of +3, and can make a high G dodge for +1, so he has a 13 or less. He rolls an 11 and easily dodges.

Note: In my space combat rules, I made missiles harder to dodge, the idea being that they could turn with you. It’s an interesting idea, but given that they’re so accurate already, I’m a little loathe to do that. It might be interesting to explore in the future.

What’s also interesting is how agile and able to dodge our fighter is. We really need some means of trimming that dodge down, so it doesn’t turn into an interminable exchange until someone gets a critical hit.

Step 5: Resolve Chase Contest

The Claw took a static maneuver, but still rolls. As far as I can tell, he still rolls Drive and adds Handling, but doesn’t add speed. That’s weird, didn’t he stop? Well, as best as I can tell, these involve up to a full minute of manuevering, so what likely happened is that our tank drove, stopped, aim, and then drove some more, all during this one turn. The handling handles how quickly it can stop and go, so if this was a ferrari he was driving, he’d still have a decent chance of keeping ahead… well, to some extent as we’ll see. In any case, this gives him a total of 14 to roll against; he rolls an 11 and succeeds by 3.

Maverick has a -2 from his move and attack, +14 from his speed, and +3 from his handling atop his skill 18, for a total of 33; he rolls an 13 and succeeds by 20.
This means Maverick wins by 17, again, which is enough for a +2 shift, and because his opponent is static, he gets another shift! In principle, Maverick can move from Extreme to short and pass within 6 yards of the tank. There’s no reason to do this, of course, and Dogfighting suggests we get no closer than Extreme; given our elevation, this seems to be best.

Note: This makes “Attack” an ideal maneuver for our tank. We can’t escape anyway (though we could Hide, at least as a tank). This would be the sort of behavior I would expect from Psi-Wars capital ships: shot at incoming craft, and shoot at other vehicles, but not to try to “escape” fighters. In principle, it should not be practical.

It is interesting though: what happens if you’ve got your enemy down cold, and have that much mobility on them, but you’ve reached a point where there’s nothing more you can do with that mobility? Perhaps there’s such a thing as “too much mobility,” and that’s fair and this reflects that, but I wonder. Perhaps we should have some kind of strafing maneuver?


I think I’m going to stop here, not because I’ve run into problems: we could play this fight out to the bitter end, but either Maverick runs out of missiles (either because the point defense takes them all down, or because he can’t get through the armor), or the tank gets a lucky shot on Maverick and takes him out. It’s actually fairly close at this point: each missile only has about a 50% chance of doing any damage, and a lot of it will be negligible (it got lucky on that first shot), mainly because it has the wrong armaments. With the right armaments, it’s one shot and one kill. We don’t have good rules for point defense; if we use the point defense rules from Modular Mecha, though, then the tank is pretty safe from missiles and I would hand the fight to the tank (It’s TL 9, so…).

I also note that the fight involves extremely accurate attacks, but we’re also featuring extremely competent characters, so that might be part of it. If the characters had skill 12, would this still be true?

What also jumps out at me is that at this point, the tank is actually stopped and fighting, and the rules for “Stop” in Action is that the Chase is over and you’re having “tactical combat.” This, of course, is geared towards people in cars shooting pistols at one another. The Chase rules are for chases, and what we want are vehicular combat rules. The combat rules of the rest of Action covers this for people; we need this for vehicles, which shouldn’t be too hard to put together. What the chase rules offer is an abstract form of movement which even the Combat rules of Action use for personal movement.

But what I find interesting is that this holds up remarkably well. It does some odd things, but for the most part, it works more or less as I expect, and that’s because, as noted above, we’re using standard, not simplified, vehicular combat rules, we just have an abstract movement system layered atop it.

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