Wednesday, November 7, 2018

Dreadnoughts don't Dogfight: Thoughts on Spaceship Accuracy in GURPS Action

The playtest between the Typhoon and the Starhawk raised some oddities regarding accuracy that I want to revisit, but far more importantly, the addition of Dreadnoughts into the game are really going to play havoc with some assumptions of the Action chase system in that we’re adding a vehicle that really operates by very different assumptions than a fighter does. This motivated me to stop and rethink how we should handle accuracy so we don’t get surprised by some emergent gameplay at the table.



Fighter v Fighter Accuracy

Our playtest showed some interesting things regarding accuracy. The first was that maybe missiles were too underpowered (“They don’t seem to do anything other than add drama,” quoth Patreon Brett Tamahori), and I personally found Tobin’s attacks very accurate. Let’s see how the numbers break down

Missiles vs Blasters

Accuracy will vary at a given distance and for a given target. Let us look at the three range values most common for fighters, and compare for a typhoon (SM +4, ECM -4, Speed +15) and assuming a radar and targeting boost for blasters (so total +5)

Range

Penalty

Blaster

W Acc

Missile w Airburst

Extreme

-15

-6

+3

-0

Distant

-19

-10

-1

-0

Beyond Visual

-23

-14

-5

-0




It should be noted that most beam weapons will get a +1 or +2 from ROF. Even so, a missile is clearly superior for accuracy than any blaster, at least as long as you’re unable to add accuracy, thus for most characters without fighter ace, or who can’t make an aimed attack for whatever reason. For a fighter ace, blasters are always better at Extreme range (not necessarily a problem), may be close to as effective at Distant (and may even be better if they have a higher ROF), but are probably worse at Beyond Visual.

Missile Defense

Missiles should turn the tables when it comes to defense: they should be hard to dodge, but you should be able to jam them, while blasters can only be dodged. My justification for this is the fact that while TL 8 missiles have a skill 10 to hit their target, ultra-tech missiles have a skill 16+, so I build in a “deceptive attack” modifier. For other missiles, like plasma lance, I might change some values to reflect a weapon meant to target a relatively static opponent.

But let’s compare

Weapon

Dodge

Dodge w Decoy &ESM

Jam

Jam w Decoy

Blaster

+0

+0


--

Missile

-3

+0

+2

+4




This clearly shows that missiles are easier to defend against as long as you’re properly equipped. It should be noted that most pilots won’t be skilled jammers and handling does not assist jamming, thus their jamming parry will be inferior to dodge, but for handling 0, the best case scenario makes Electronics Operation (EW)-10 (5+4=9) the equivalent to Pilot-18 (9). This definitely means that the prime defense against missiles for capital ships will be ECM.

For the average fighter pilot, missiles have clear utility at a distance: you’d be a fool not to use a missile at ranges farther than extreme, and it’s tempting to use them even at extreme ranges. They’re only downside is that they can be relatively easily jammed. For a fighter ace, a blaster is clearly and obviously superior. In fact, anytime we can add accuracy to the blaster, it clearly pulls ahead of the missile because you can’t add additional accuracy to a missile.

We could ignore that: giving it yet another +4 to hit would balance it against beam weapons nicely, but you don’t really need that much accuracy. If you have skill 16 already, a +4 takes a sure hit and turns it into a sure hit. An increased penalty to deceptive attack would be more useful, but it’s not clear it makes sense. The penalty here represents the speed and agility of the missile, but it doesn’t become faster or more agile just because you spent more time aiming it. You can’t aim it, you just lock it and it aims, and in fact, according to GURPS Basic, for guided weapons if it takes more than 1 second to get to its target (almost always the case here), it automatically counts as aimed, while homing weapons don’t even count as attacks: they count as readying weapons. All you’d really get with extra aiming time is the chance to fire more missiles.

So let’s do that: any time you would have an accuracy bonus, you can forfeit it to instead get an Extra Attack with a missile only; anytime you get Accuracy +1, you can forfeit the +1 to gain an extra attack with a missile only, or the full Accuracy +1 to gain two extra missile attacks, all in addition to whatever attack you were going to make (thus a fighter with accuracy +1 could make a blaster attack with accuracy and fire a missile, or fire three missiles, etc).

We can also down decoys by 1 point. The idea behind them was to follow GURPS Spaceships with its “up to 3 ECM systems” with Stealth, Distortion Jammers and ECM making up the “Three” systems, but decoys are small and cheap, more on par with an ESM in terms of cost and mass, so should probably have similar utility. A +1 to both dodge and Jam should be enough.

Dreadnought v Dreadnought

Dreadnoughts differ from starfighters in three key ways: they are bigger, they are slower, and they can sit still. Being slower and bigger makes them an order of magnitude easier to hit, and being able to sit still means they can make an “Attack” maneuver and add their accuracy. The net result is that in a duel between two dreadnoughts, we shouldn’t think of whether the target will be hit, but how many times and how critically it will be hit.

Thus, the primary concern for a dreadnought in a dreadnought v dreadnought duel is not “how can I dodge?” but “How can I reduce the damage I suffer?” I tackled this in large part in the damage post, where I highlighted that, on average, two dreadnoughts attacking one another will probably kill each other, and the fight comes down to who attacks first unless you have some means of putting some superior DR between yourself and your target. The damage system’s intent is to make this much more manageable so we don’t have these instant one-shots. The other thing we can do is put some range between dreadnoughts, which is a topic I will come back to in a later post.

Dreadnought v Starfighter

We expect a dreadnought v starfighter duel to play out like a torpedo bombing run in WW2: the starfighters race through a barrage of exploding flak fire, losing some members of the squadron, but then fly through, drop their torpedoes and fly away while the dreadnought is rocked by explosions. We might also add another dreadnought firing broadsides just for good, dramatic measure, and escort fighters shooting the the attackers. Unfortunately, with the rules as written, I don’t think this is how it will play out.

This is where all the problems arise. Dreadnoughts and Starfighters exist as far apart on the space combat spectrum as possible, and in principle, much of the drama of the game should arise from the tension created by this difference. In practice, I worry that it will create an enormous headache of emergent problems because the systems we’ve been playing with so far don’t really think on these scales, except for GURPS Spaceships, which thinks too big.

I noted the prime differences of dreadnoughts vs starfighters above, but the critical one is the ability for a dreadnought to “sit-still.” A dreadnought cannot hope to outrun or outmaneuver a starfighter, and a starfighter is small and quick, but fortunately, a dreadnought is typically going to be armored to the point where it can shrug off starfighter attack, and it has sufficient accuracy to shoot a starfighter out of the sky from miles away.

Let me show you what I mean. Assume that on the approach to the Dreadnought, the fighters enter Distant range (-19 to hit). The dreadnought has radar (+3), targeting computers (+2) and its opponent is SM +5 (on average). Assuming skill 12, we have a skill of 3 to hit. That sounds about right to hit targets that are just barely visible, just swooping in at a far distance… except the Dreadnought has no reason to make a move and attack, but would instead make an attack, and gain it accuracy for +9, giving it a 12 or less to hit, which will hit a target ~3/4 or the time. Once the fighters reach Extreme range, prepping to make their run, this rises to 16, which is a virtually guaranteed hit: assuming one turret per fighter (which is pretty doable for a dreadnought vs a squadron) and we’re almost certain to wipe them out, especially given two full turns of shooting. If we go with the typical rule of combining all guns on the vehicle into a single high ROF attack, a dreadnought (as already designed) has about 20 shots for a +4 to hit; this means that the first round of fire will hit 4 times and the second round will hit 6 times, cutting the squadron nearly in half. And this isn’t with anti-air weapons: this is capital scale weaponry dealing thousands of damage. We can easily equip a dreadnought with 100 small-scale cannons that can each deal ~200 damage and have a high ROF; assuming 100 turrets with RoF 10, we’re looking at +10 to ROF, giving us 7 hits in the first round and 9 hits in the second round, which almost destroys an entire squadron, and this is only “so weak” because we’re using the very conservative ROF rules and treating the squadron as a single entity: if we divided our 1000 shots up among the 25 targets, we’d have 40 shots (+5 to hit, or 17 at Distant and 21 at extreme) per target.

Point Defense: Dreadnoughts Attacking Fighters and Missiles

So how do we fix this problem? At the core, we need to bring our game’s reality close to the cinematic vision that we described earlier and taken more cohesively, it looks something like this:

  • Capital ships slug it out with other capital ships, struggle with corvettes and use flak to kill fighters

  • Corvettes make hit-and-run attacks on capital ships, fight over corvettes, and fend off fighters with directed fire with some success

  • Fighters dodge agilely through capital ship attacks and corvette attacks (to a lesser extent), struggle with flak fire but can survive it after taking maybe a hit or two, and have no trouble hitting corvettes or capital ships, but need to make an effort to really damage them.

Turret Accuracy

GURPS Spaceships has a fix for a lot of this in GURPS SS 4 with its Relative Size Modifier. The principle here is that larger ships have a harder time hitting smaller ships. Using this suggested rule has some problems, though, in that it uses relative size (which requires some additional recalculations every time you want to fire at a different target) and makes some assumptions about the size of turrets using GURPS Spaceships terminology, which we won’t have. The core of it is this: big ships always have a hard time hitting smaller ships; their biggest turrets suffer the most, but their smaller turrets have less of a penalty.

This isn’t crazy. Turrets have a speed at which they can move and track a target. Bigger, heavier turrets take more time to turn and track a target than a smaller, lighter turret. EVE uses a similar principle in giving fighters a role in their game against giant capital ships. It should be noted that speed and size probably matter here: an unmoving car can be easily hit by a battleship, and a tank might struggle to track a fast fighter despite being smaller than it.

Before we adopt this rule, let’s look at the current situation and contemplate what the ideal situation would be.

Let us assume a fighter is SM +5, a Corvette is SM +9, and a Capital Ship is SM +13. For range, assume Extreme (-15); for skill, assume 12; for dodge, assume the fighter has +4 handling, the corvette +0, and the capital ship -4. This means that a dreadnought will never dodge, a corvette will dodge on a 10% of the time, and a fighter will dodge 50% of the time.

If we use the GURPS Spaceships optional rule, a Capital ship should hit a fighter with a -8 penalty (-4 for “small” turrets), and a Corvette should hit a fighter with a -4 penalty (-2 for “small” turrets). Alternatively, we could introduce a flat -10 for capital ships shooting at fighters, and a flat -5 for corvettes doing the same, and halve that penalty (round down) for “smaller turrets;” this requires less recalculation.

The combining everything, we see:



Capital

SS4

Flat

Corvette

SS4

Flat

Fighter

SS4

Flat

L Cap turret

98%

98%

98%

89%

89%

87%

49%

13%

5%

S Cap Turret

98%

98%

98%

89%

89%

89%

49%

37%

31%

L Corv Turret

98%

98%

98%

89%

89%

89%

49%

37%

31%

S Corv Turret

98%

98%

98%

89%

89%

89%

49%

45%

49%

Fighter

98%

98%

98%

89%

89%

89%

49%

49%

49%

Fighter
(No Acc)

95%

95%

95%

57%

57%

57%

8%

8%

8%





No system really makes a meaningful difference for corvettes: a capital ship will blow them out of the water, though it should be noted that as we use various optional rules, it goes from “Lots of hits with a rapid fire weapon” to “One or two sure hits with a rapid fire weapon.” The big problem that corvettes face is insufficient dodge. +1 or +2 dodge goes a long way to improving avoiding a hit!

The main advantage of a fighter is that 50% dodge chance, but at the extremes, they really see a benefit from their smaller size. Note how much its accuracy drops off if denied accuracy. “Attack” is a really powerful option when compared to move and attack, though it should be noted that high skill makes a difference. A skill 15 pilot is nearly as likely to hit a fighter on a move and attack as a small capital ship cannon will with an aim.

So we have a few options here to tackle this: we can use the suggested house rule as written; we can use the improved rule for greater contrast; we can use one of the previous two rules but make no distinction between large and small turrets; we can find some way to remove the accuracy bonus from the Attack rule;

Of these options, I favor the flat modifier with full distinction between small and large turret. A lot of corvettes (especially traders) will mount relatively small cannons and they should have something of an advantage against a starfighter (as we see in Star Wars). It’s also easier to compute.

The only thing we need to do is define our turrets and what we mean by a fighter, corvette, etc, because speed easily matters as much as size. For “large” turrets, any fixed mount or any turret noted as “big” counts, and likewise, a “small” turret is anything that we note as “small.” Simple. Behind the scenes, we’ll base the distinction on the effective size modifier of the turret. A “Main or Medium” battery from GURPS SS would be any turret that’s as small as 1/60th of the ship’s total volume; for SM +10 (our smallest capital ship size) that comes to about SM +8. Anything smaller than that counts as “small.” For a corvette, which are as small as SM +7, we’re looking at anything that’s as large as SM +5; anything smaller than that is “small.”

What counts as a Starfighter? What counts as a Corvette? I think a GM will just obviously know, but if we need a definition, then it’s either SM or it’s speed and handling. After all, a very slow and ungainly craft might be small, but it’ll be much more easily hit than a fighter would be. We already have an SM definition (6 or less for fighters, 7-9 for corvettes, 10+ for capital ships), but if we want a speed/handling definition, we need to look at expected performance. A capital ship will have a handling of -1 or worse, and go no faster than speed 150 (+11), which means that anything with a chase roll of 10 or less counts as a capital ship, or a “slow” ship. A corvette will have +0 to +2 on handling and a speed up to 300 (+13). Thus, anything up to a total chase roll of 11-15 counts as a “medium” ship, and anything 16+ on their chase rolls counts as a starfighter, or “fast” (+3 handling and a minimum speed of 300, or +13). I would use this as a general guideline if there are edge cases, or let the GM decide. Generally, if we call it a fighter, it’s a fighter, etc.

Note that there are no sizes that let you eliminate the penalty entirely! This means there’s no real point to making hundreds of tiny defense turrets, at least, not to get around this particular penalty (it might help for sheer ROF though).

Anti-Air Defense

Okay, but what about defenses explicitly designed to defeat fighters? We often see battleships and their like outfitted with substantial air defenses and, in fact, this greatly reduces the effectiveness of fighters. What sort of gear can we use to simulate the exploding flack and shooting rockets that fighters faced in WW2?

Just Turrets, Man

The first point is that high ROF turrets are sufficient defense. A 20 ROF gatling blaster on a “small capital turret” has a +4 to hit jumps its odds of landing a hit to ~50%, and because it’s harder to dodge, is more likely than that to hit at least once. If we put many many such turrets, the sheer volume of fire will surely take out a few fighters. This doesn’t quite give us our “flak fire” though.

Missiles

In the real world, many of our capital ships pack missiles, and why not ours as well? We actually see a missile system used as an anti-fighter weapon in the Force Awakens. Such a weapon would probably be a 160mm Heavy Modular Launch System from Pyramid #3/37, which fires the same missiles fighters use to defeat one another, and face the same difficulties that fighters would giving the two sides parity. This does allow for some substantial reach, making them a “first line of defense,” but they’re also likely to stop being useful once the fighters have come too close.

Plasma Flak

What is flak anyway? Well, in WW2, rather than try to directly hit a target, they filled the sky with shrapnel, hundreds and hundreds of tiny bomblets and hoped this “shotgun” approach would take out bombers. If we wanted to simulate that, we could use a high ROF plasma weapon that had some sort of “timed decay” on its “containing field” so it burst on command. This would give us a +4 to hit, plus the RoF bonuses, and might do a good job simulating flak.

This would give us a highly effective means of trying to hit starfighters, but what’s interesting is that it did more than this:

[Anti-aircraft guns] really put bomber pilots off their game. No, really, it’s that simple.
-Andrew Givens, “How did the anti-aircraft guns help in the war?

My research into flak suggests that the point of flak wasn’t actually to hit a target, but to create an area of denial, similar to the real purpose behind a grenade or suppression fire. Sure, you might hit someone, and you’re not going to complain if you do, but it’s not what you’re trying to do: you do not aim a grenade or suppression fire to hit someone, you aim it at the area you want to deny your targets.

It seemed to do other things: it distracted the bombers, it may have demoralized them, and it “made it harder to fly.” What it really did is made it so they they couldn’t afford to just hang around. We can make plasma flak worse and declare that it makes the terrain rough and applies a -2 to all piloting rolls made in its area of effect unless your DR exceeds the damage that any plasma bomblet could do, in which case you may freely ignore the effect. This makes stunts and such harder in the area of effect.

We can design a plasma flak weapon by using a variation of GURB’s work on plasma blasters here with a few minor alterations to account for timed decay fields and whatever else to get roughly the values I want. An ROF 20 “flak turret” that deals 200 damage per shot comes to about 100 tons, making it a small turret for capital ships carrying it and a large turret for corvettes. A flak turret picks a direction and can attack everyone in front of it out to Extreme Range with a flat skill of 12 + SM + ROF Bonus – Range penalty (for greater simplicity, it has a to hit of 7 out to Extreme and 11 at Long or Closer). Anyone caught in the blast area treats the terrain as “Rough” and suffers a -2 to all handling rolls. Failure on the terrain roll results in being hit by one plasma blast in addition to the wipe-out. Multiple turrets can combine ROF to improve accuracy by firing in the same direction.

Starfighters vs Dreadnoughts

Once starfighters start fighting a dreadnought, they need a few advantages of their own! Their smaller size and faster speed should give them some means of getting around the prime defense, which is their prodigious armor.

Hugging

In the previous versions of Psi-Wars, we used the “Hugging” rule from GURPS Starships 4. The idea here was that you could get so close you were flying near enough to the ship. I like this rule, and with only a few small changes, I think I can make it work.

“Hugging” requires you to be in Collision Range and you must “Match Speed” with your target. The target must be at least +3 SM larger than you (Yes, corvettes can hug capital ships; this represents flying so close that you’re hiding in the “shadow” of the bulk of the ship). If you your target is +6 SM’s larger than you, you are “beneath” their force screen and may ignore its effects! While hugging, only turrets (not fixed mount) with the proper facing weapons may fire at you, and only half of them may do so. Further, all attacks made against you are at -2, as you have “cover” from the ship you’re currently hugging. You may not be attacked by “Plasma Flak.” Missed shots made at you from other vehicles that miss or are dodged will hit the hugged craft on a 3d roll of (target SM-3).

Armor Chinks

In previous iterations, I had used armor chinks and armor gaps to attack vulnerabilities in a craft’s armor. I certainly think there’s still room for armor chinks, though I don’t think armor gaps are strictly necessary. You can include them as an optional rule at -15 rather than -10 for armor chinks.

The main purpose of armor chinks are for smaller vehicles to make an outsized impact on larger vehicles. Typically, high damage, low AP weapons like torpedoes excel at this. Assume we have an opponent with DR 2500 Armor vs a turret that does 2500(5) damage on average, and a torpedo that does 3500. On average, the turret will deal 2000 damage to such an armor, or 2250 if it hits a chink. By contrast, the torpedo will do 1000 damage if it hits the armor head on, or 2250 if it hits a chink.

I have a few concerns: first, missiles should not be able to hit chinks as it doesn’t make sense (you lock onto a vehicle and the missile will hit what it hits) and I want to keep plasma lance missiles slightly weaker than torpedoes where possible. Second, I want to make sure this is a trick that requires one to get close to a target to pull off. Finally, I want this to be the domain of fighters rather than other capital ships.

The first is easily done; we simply declare it so. The second just requires an analysis of the difficulty of hitting a target. Assuming SM +13 with a skill 12 pilot, we have a base difficult of 20 before applying range. This means that at Extreme Range, you have a skill 5 or less to hit! You really need accuracy or matched speed to pull something like this off.

Which brings us to our last problem: dreadnoughts attacking weakpoints. With the same results as above, and an accuracy of +9, a dreadnought can pinpoint another dreadnought’s armor chink with a 14 or less, so that seems a problem, but on the other hand, this costs them about 5 extra hits. If your attacks can already penetrate their armor, you’re better off just hitting them as often as possible. TO use our above example or DR 2500 vs 2500(5) average damage, each attack will deal 2000 damage, so 5 extra hits is 10,000 total damage, or you can get 2250 damage. With our new damage system, there may be times you want the latter, but I doubt it will be a tactic often used, so I’ll leave it be.

Torpedoes

I believe I have brought this up elsewhere, but the inspiration from which I’ve drawn isomeric torpedoes are typically slow moving (compared to fighters and missiles), unguided rockets of enormous size. Thus, they’re rockets, and as such, they use a different skill than missiles do. I propose that they use Gunner (Torpedo), which defaults to Artillery (Missile) at -2 and Gunner Beams at -4. They have an Accuracy of 4 and ignore force screens (for the same reasons fighters do: they’re essentially very small, unguided fighters with a warhead).

I have found in my calculations that in some cases, it makes a lot of sense to launch from a considerable distance away, knowing that the torpedo will arrive in the same minute and kill the target without exposing the bomber to undue flak and turret fire. As compensation, I will note that torpedoes cannot attack mobile targets farther than Distant ranges, and that for every range band beyond Long (or Collision Range) the target gets a +1 to dodge. This treats is a bit like a telegraphic attack. In general, this is meaningless to large capital ships, which often have a dodge of 3-4, but it matters for corvettes that might have a dodge of 7-8, which can mean that attacking with a torpedo from a long way off is less likely to hit than moving close.

Point Defense against Missiles and Torpedoes

If we’re going to allow corvettes and capital ships to defend against missiles, we should define what we mean by “defend.” I have proposed treating it as a parry, and that’s pretty close to what we’re literally doing here, but the math we’re going to use makes it a bit complicated to treat as a parry (You could do it, though, you just halve all the numbers I’m about to discuss). Thus, I propose treating it as a Wait and Attack, just like Spaceships does.

What values should we use? Well, the SM of the missile and its speed. In principle it should always be close enough to hit in a single action chase turn (thus, for a torpedo, you should be within 18,000 yards, which is definitely out to Distant, but perhaps not Beyond Visual, which might go to 50,000 yards), thus we don’t need to “wait” turns to hit, and that also means range isn’t relevant: you can wait for the missile to be a couple of yards away. Otherwise, you should be able to add all modifiers:

  • Your skill plus

  • +3 from radar

  • +2 from targeting computer

  • the missile SM

  • the missile speed

  • The relative size modifier (treat the missile as a fighter: -10 for large capital ship weapons, -5 for corvette, halved (round down) for smaller turrets).

  • Accuracy, if appropriate.

  • RoF, if appropriate.

What are the SM and Speed?

  • 100mm missile: SM -2, speed -14 (total Point Defense penalty: -16)

  • 160mm missile: SM 0, speed -16 (total Point defense penalty: -16)

  • 400mm Torpedo: SM +2, Speed -13 (total point defense penalty -11)

  • 640mm Torpedo: SM +3, Speed -13 (Total point defense penalty -10)

  • 1600mm missile: SM +4, Speed -12 (Total point defense penalty -8)

So missiles are largely a waste of time to shoot down; they’re harder than fighters at extreme, and won’t do enough damage to larger ships to really matter; the torpedoes are much easier, but still potentially difficult: difficulty 10 for a dreadnought to shoot down a 400mm torpedo with light turrets, and 12 for a corvette to do the same, plus ROF, of course.

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