using spaceships for battletech-style tactical mecha combat

[muduri]

As a break from Dungeon-ish Fantasy, our group has played a couple games of tactical TL10^ Spaceships demolition derby. I did some tweaking (costs, damage, Acc, DR, HP, thrust and burn) to increase playability and fun for this scenario in particular, at the expense of wider applicability.

So now we'd like to do something similar, ground-based at say SM+4 and TL10 (not that different from the old Battletech) - use Spaceships to build mecha and maybe some tanks, pair them up with infantry squads, and go at it. Have some preliminary thoughts; also curious if others have tried combat at intermediate scales and with ground-based Spaceships, and what your experience / suggestions are.

1) For scale I'm thinking something much smaller than Spaceships or tactical Mass Combat but still a little bigger than traditional combat - maybe 2 seconds and 5m hexes? My thought is it would let tracked or wheeled vehicles use Enhanced Move without racing across the board, but also have infantry make some progress.

2) If I remember correctly, ultra-tech weapons (realistically) have a huge range, probably several mapboards even with 5m hexes. At the expense of realism, would it increase playability to divide ranges of most weapons by say 10? Battletech-style, your first dash from cover to close the gap wouldn't be your last and there's a chance of getting into melee range.

3) Multiply characters' and vehicles' HP by 10 or even 100? The hammer-and-eggshell binarism of ultra-tech is of course pretty realistic but a little less fun. Given TL10 damage, DR and armor divisor values, say, I'd just like to use a number where a mecha could get hit by a particle beam, or an moderately-armored infantryman could take a UV laser hit, and be injured enough to change tactics but was still likely to survive.

4) Justifying mecha - the age-old problem. Was thinking of making the terrain hilly so a lot of terrain that's problematic for tracks or ATVs, and maybe a munitions factory where (what a coincidence) SM+4 craft with arms can swap out their major batteries for the cooler ones they find lying around. Anything else that could help justify sacrificing four system spots to arms and legs?

5) We were thinking of keeping it quick for characters, so probably stripping things down a lot from real tactical combat, but anything for squad tactics that's essential, should be dropped, or optional but would add fun, playability or even (dare I say it) realism, much appreciated. Thanks!

[Fred Brackin]

2 is probably not as necessary as you might think. Just try and _hit_ anything at a UT weapon's maximum range and you'll probably see that there isn't that much change needed. If you didn't alter ACC no change to Range would matter much anyway.

To run some numbers, an Aimed shot with a TL10 ACC 18 Laser Cannon hits at base Skill at 2000 yards so it looks like you might want to use a larger scale for that but that's the most accurate type of weapon in UT and its' 1/@ D is 72,000 yards. The TL10 Blaster Canon is only ACC 15 which compensates for 700 yards and the Plasma Cannon at ACC 12 does so at 200 yards.

Guided missiles are the exception to this. They ignore Range penalties.

You probably don't want to run vehicle (or even rifle) combat at a literal 1 yard per hex of Tactical Melee combat but whatever scale you choose base it off of ACC rather than theoretical maximum range.

[muduri]

Originally Posted by Fred Brackin

...If you didn't alter ACC no change to Range would matter much anyway.

To run some numbers, an Aimed shot with a TL10 ACC 18 Laser Cannon hits at base Skill at 2000 yards so it looks like you might want to use a larger scale for that but that's the most accurate type of weapon in UT and its' 1/@ D is 72,000 yards. The TL10 Blaster Canon is only ACC 15 which compensates for 700 yards and the Plasma Cannon at ACC 12 does so at 200 yards...

Thanks, very good point - will apply. For the purposes of this one-off then maybe we could reduce Acc by say 6 rather than doing it with range - would I have it right that that would then give you:

laser cannon - Acc 12 = 200 yards to roll at skill±0, 40 hexes at our hypothetical new scale
blaster cannon - Acc 9 = 70 yards, 14 hexes
plasma cannon - Acc 6 = 20 yards, 4 hexes

Those numbers seem quite playable for making movement meaningful. As you point out, unless we're dividing 1/2D and Max ranges by 500 it's Acc that really makes the difference.

[muduri]

...Again ignoring for the moment the fact that this would scupper wider applicability, it's also tempting to modify Accel and Max Move numbers to the legs and drivetrain tables based on SM - e.g., -10% for each SM over 3 - in line with the old "small maneuverable vs heavy and armored" trope.

I remember there were good reasons this didn't apply in space, and that the math of atmospheric lift and drag got very complicated for flight, but would this seem playable, if not necessarily realistic, for mecha and tanks?

[johndallman]

For tanks, on the scales they've been built so far, speed is basically a function of power-to-weight ratio. 15KW/ton gets you a tank as fast as seems to be useful.

[dataweaver]

The main difficulty I see here is that you're basically restricted to three sizes for your mechs because of the way Spaceship design works: 10 tons, 30 tons, or 100 tons. That said, I've been working on an idea for fractional SM, where you can measure a vessel's (or in this case, a mech's) SM in steps of 0.2 (but always rounding to the nearest number whenever you use it as an actual modifier). This would give a lot more versatility, letting you have mechs of 10, 12, 15, 20, 25, 30, 40, 50, 60, 80, or 100 tons.

The challenge here is applying this extra precision to Spaceship systems. Fortunately, the progressions used there are pretty standard; there are only a handful, plus a few systems (like the controls) that run into problems with integers near the low end.

[mlangsdorf]

I haven't done mecha-versus-mecha combat, but I ran a combat focused campaign of small mecha (~5 yards tall) versus 15'-30' giants, mostly using the stock GURPS rules. It worked pretty well.

Changing the hex scale to 5 yards is fine and saves you some hassle. You might even want to make it larger (see below).

I'm less sanguine that Fred is about weapon ranges. Taking the T-72 from High-Tech p244 as the minimum for a dedicated combat vehicle, it's firing a braced Acc 6 weapon with an Acc +3 scope, Acc +3 targeting laser, and Gunnery +1 targeting computer. After 3 seconds of aiming, you're looking at +14 to hit - and another +4 if you're firing at an SM+4 target. 2000 yards is -18, so a gunner with Gunnery-12 hits 75% out to a mile (and 98% of the time at 500 yards). Swap the 125mm gun for a TL10 Blaser Cannon with Acc 15, and you're hitting out to 7500+ yards. A lot of those targeting aids take time, so if you're firing on the move, you're a lot less accurate, but even if you only get a second to aim, +19 cancels range penalties out to 3000 yards.

It wasn't an issue in my game because I was using a virtual table-top and having maps with 1000+ hexes, but you'll need to do something if you're looking to play on a table with 30-40 1" hexes.

You might try 20m hexes and 5 second turns. Running infantry can move about a hex per long turn. Vehicles can choose between moving, aiming, and firing, something like this:

Snipe - Don't move at all, aim for 3 seconds, fire once
Double-Tap - Don't move at all, do a sequence of aim and fire twice
Fire for Effect - Don't move at all, aim for a second, fire three times at one target
Suppression Fire - Don't move at all, make four unaimed shots
Shoot and Scoot - Aim for a second, fire once, move for two seconds (can be split before or after aiming and shooting)
Walking Fire - Move for two seconds, take two unaimed shots during the movement
Run and Gun - Move for a total of 3 seconds, take an unaimed shot somewhere in there.
Zoom - Move for 5 seconds.
Zoom and Boom - Move for 5 seconds, making up to 4 Moving Attacks in the process.

1 attack per turn can be converted into a Wait, which is useful for preventing opposing Aim attempts.

In all cases, I'm assuming that everyone spends 1 second during every long turn doing situational awareness activities.

I'd also put up a lot of terrain to block lines of sight. But even so, vehicle attacks within 300 yards are going to be deadly for anyone who manages to get an Aim action in.

[Phoenix_Dragon]

Sounds like a good argument for tanks, which can do both Zoom and Snipe (Or any other "no move" fire option) at the same time.

[mlangsdorf]

GURPS mechanics really encourage having one guy do the fighting and one guy do the driving. You see it in Spaceships (multi-crew small craft beat single seat fighters), you see it in tanks versus mecha, you even see it with horse archers fighting flying monsters with ranged attacks.

I think this is pretty realistic: the reason that tanks evolved to 3-5 person crews is because having multiple doing different things works better than having a driver and a commander/gunner/loader.

My first suggestion for a mecha game would be say that tank main guns reload slowly enough that a tank has to snipe because it can't fire multiple shots in 5 seconds. That's not unrealistic for cannon without an autoloader, but doesn't work for particle cannons.

The other thing to remember is that a tank's stability rating, even with stabilizers and all that, is no where near the maximum accuracy of the gun. You may be able to theoretically snipe on the move, but since your effective SR is only 9, you're not hitting other vehicles at more than 300-500 yards.

[Phoenix_Dragon]

Originally Posted by mlangsdorf

The other thing to remember is that a tank's stability rating, even with stabilizers and all that, is no where near the maximum accuracy of the gun. You may be able to theoretically snipe on the move, but since your effective SR is only 9, you're not hitting other vehicles at more than 300-500 yards.

Maybe if you're driving a WW2 tank or an old, stripped-down export-model tank. Stabilized weapons don't have the SR limitation.

Modern tanks engage well beyond 500 meters on the move. More like 2-3 kilometers (And more likely to be limited by LoS obstructions than accuracy!).