Wednesday, October 17, 2018

Action Vehicular Combat

These rules are based on the GURPS Action Chase rules starting on Page 31 of GURPS Action 2: Exploits; this has been substantially updated to account for dogfighting and other, heavier forms of vehicular combat.  While this was designed for Psi-Wars, most of it should work for any vehicle-heavy Action game.



New Traits

Ace Fighter

25 Points

The character is an elite vehicular combatant: he gains all the benefits of a gunslinger when using vehicle-mounted weaponry (such as missiles, fixed-mount blasters, or turrets). He also gains +1 to vehicular dodge to the first attack he suffers that turn after making a successful stunt.

Range Band Table

Psi-Wars uses an expanded Range Band table, both for ranged combat and for chase scenes. Use the low range penalty for all ranged attacks.

Range Band

Starting Range

Range Penalty

Notes

Close

0-5

-0 to -2

Melee Range; Apply bulk penalty to ranged attacks at this range

Short

6-20

-3 to -6

Pistol range;

Medium

21-100

-7 to -10




Long

101-500

-11 to -14

Rifle Range

Extreme

500-2000

-15 to -18

Sniper Range

Distant

2001-10,000 (5 mi)

-19 to -22

Missile range

Beyond Visual

10,000-50,000 (5-25 mi)

-23 or more

Requires active sensors to engage

Remote

50,000+ (25+)

-27 or more

This is beyond meaningful range in any chase scene!




Rounds

Use the rules found on page 31 of Action 2.

Round Sequence

You may use the sequence noted on Page 32 of GURPS Action 2 (especially if the chase is literally a chase). Alternatively, the character with the higher Basic Speed or the character with Advantage is declares second and resolves first (like the “Pursuer”) while the other character declares first and resolves second (like the “Quarry”). This works best for dynamic “dogfight” style combat, or running gunfights.

Characters driving vehicles that have configurable options (afterburners, variable geometry wings, angular force screens etc), the configuration of the vehicle must be set when the player declares his character’s maneuver.

Chase Maneuvers

In addition to the notes on page 32 of GURPS Action 2, the following rules apply:

Advantage: A character who wins a “chase roll” gains advantage over his opponent. This represents superior positioning! Advantaged characters gain a few benefits over their opponents, noted here and in the Chase Roll resolution roll. Once advantage has been gained on a target, it cannot be lost until the character loses a chase contest or he switches targets for his chase maneuvers.

Collision Range: Any vehicle whose speed bonus is greater than the absolute value of their range penalty is at collision range. This is “close” for humans, but may be much greater for faster vehicles. “Collision Range” is important for certain Conditions.

Facing: Vehicles have 6 faces: Front (F), Right (R), Left (L), Back (B), Top (T) and Under (U). A vehicle that “pursues” its target has its Front (F) facing its opponent, while a vehicle that “evades” its target has its Back (B) facing its opponent. When a chase or fight begins, or when two vehicles which had not previous engaged one another do so, they are “Neutral” to one another, and the GM can determine what their initial facing towards one another is. Any fixed mounts on the vehicle must have the proper facing to fire. Characters who are Advantaged may make an attack at any facing of its target (Within reason: generally two ground vehicles cannot attack the “Top” or “Bottom” of the other, for example). Note that in a chase or a dogfight, facing is, in fact, highly dynamic. This represents the facing that most commonly faces your opponent.

Match Speed: Characters who are already Advantaged against their target and gain Advantage again may “match speed.” The benefits of “matched speed” are noted in the attack rules!

Pursuit or Evasion: Instead of worrying about “Pursuer” or “Quarry,” when a character chooses a maneuver, he must declare if he pursues or evades. A pursuer may not increase range between himself and his target, while an evader may not reduce range between himself and his target. Two characters may attempt to Pursue or Evade one another! A vehicle with a stall speed may not pursue a target that is Advantaged against it.

Static: Static maneuvers cannot be undertaken by vehicles with Stall Speeds unless that Vehicle has first Stopped. Static vehicles automatically lose Advantage and cannot gain it.

Specific Maneuver Updates:

Attack: Vehicles with a stall speed may not Attack. Facing: F

Disembark/Embark: May also represent boarding a vehicle or entering/departing a carrier in a fighter, or escaping a vehicle via ejection system or lifepods. Minimum necessary range is Collision range. Facing: Any(Operator choice).

Emergency Action: Facing: Any (Opponent’s choice).

Force: Requires Collision range, rather than Close range. Facing: Any (Operator’s choice).

Hide: Facing: Any (Operator’s Choice)

Mobility Escape: Facing: B.

Mobility Pursuit: Facing: F.

Move: You must note if you are pursuing your opponent (in which case you have F facing) or escaping your opponent (in which case you have a B facing). Note that two vehicles can attempt to pursue one another if both seek Advantage. Vehicles with a stall speed may not Pursue a vehicle which has Advantage against them (but they may Escape).

Move and Attack: Facing: F; if you have sufficient mobility to gain a mobility move, at the GM’s discretion, you may freely attack normally disallowed facings (such as the Top (T) of a ground vehicle with an aerial vehicle, or the Underside (U) of a boat with a submarine).

Reverse: Ignore this; this is better handled by the facing system and the fact that vehicles can switch between pursuer and pursued at will (and, in some cases, both are pursuers)

Ram: Requires collision range, not close range. Facing: F.

Stop: Facing: Any (Operator’s Choice). This can also be treated as a static maneuver wherein nothing happens, as opposed to surrendering a chase (especially in a space battle!).

Stunt: Facing: Any (Operator’s Choice). Vehicles with a stall speed may not Stunt against vehicles which have Advantage against them (but they may Stunt Escape). Stunts may also be High G. A High G stunt adds +1 to the chase roll, in addition to the bonuses gained from the Stunt itself, but requires an HT roll with the same prerequisites, bonuses and consequences as outlined in High-G dodge in Defenses (see below).

Stunt Escape: Any (Operator’s Choice); Stunt Escapes may be High-G, just as with Stunts above.

Chase Rolls

See GURPS Action 2 page 34, with the following update:

Chase Rolls meet in a Quick Contest. The outcome sets the range band at the start of the next round:

Victory by 0-4: No change. If your opponent had Advantage against you, they lose it.

Victory by 5-9: You may either gain Advantage against your foe or shift range by one range band. Characters who already had Advantage against their foe may Match Speed. If the character chooses to shift range, those who made a Pursuing Move or Move and Attack must reduce range while those who made an Escaping Move or Move and Attack must increase range.

Victory by 10+: You may Match Speed or shift range by one range band and gain Advantage (unless you already had Advantage, in which case, you Match Speed) or you may shift range by two bands. Shifting bands follow the rules for Victory by 5-9.

Voluntary Shifts: If both craft pursue one another and both involved agree, an additional range band shift can be freely granted. If both craft attempt to escape one another and both involved agree, either an additional range-shift can be granted or both can simply escape.

Escape

Escape occurs under the following conditions: the chased target successfully hides and elects to escape; the pursuer stops and declares their intent to resign the chase; the chased target exceeds the maximum range for attack given the current terrain; the chased target successfully shunts into hyperspace.

At the GM’s discretion, if the chase enters perfectly open terrain where further maneuvers are no longer relevant and only maximum speed matters, the GM can declare that the vehicle with the highest speed automatically wins the chase. For the chased target, this results in an escape. For the pursuer, this means that combat occurs at whatever range the chaser desires.

Static Maneuvers

See Page 34 and 35 of GURPS Action 2. Note that a static maneuver grants your opponents one free range band shift, and not victory on a chase roll! The static vehicle may still participate in the chase and may even gain Advantage, but their opponent will still gain their range-band shift!

A vehicle that has Matched Speed automatically loses its Matched Speed bonus if it engages in a static maneuver and its opponent does not.

Attacks

See GURPS Action 2 page 35 with the following clarifications:

Advantaged: If you pursued your opponent and you are Advantaged you may choose to attack any facing the GM allows.

Deceptive Attacks: Characters engaged in a chase may make deceptive attacks!

Facing: Any weapons you wish to attack with must have the option to attack in the facing you currently have. When attacking, you will attack the facing that your opponent declared. If you are Advantaged against your opponent, you may choose which facing to attack. If you have the ability to make a mobility pursuit or escape, the GM may allow you to attack normally forbidden facings. If you have the option to choose which opponent’s face you attack, this choice applies only to your attack (a different opponent might attack a different face).

Matched Speed: If you have Matched Speed, you gain the benefits of Advantaged; Additionally, instead of using the Range (and Speed) modifier below, use the higher of the absolute value of the range penalty or your Stall Speed as your Range/Speed penalty. Finally, you may add accuracy to your attack even if making a Move and Attack (or any other attack that does not normally grant accuracy).

Movement: Gunslingers never suffer movement penalties for firing with hand-held weapons. Vehicle mounted weaponry never suffer a penalty for move and attack. Passengers aboard a vehicle suffer a -1 for hand-held weapons only; vehicle mounted weapons (such as stabilized turrets) suffer no penalty.

Range (and Speed): Always use the highest of the absolute value of your range penalty, your own speed penalty, or your opponent’s speed penalty as your range penalty. In most cases, range will be the most important concern, but as very quick vehicles get closer to one another, their speed matters more and more. If your own speed bonus exceeds the absolute value of your range penalty, then you’re said to be “in collision range.”

Sensor Lock: Gain +3 to all attack rolls if you have a sensor lock.

Targeting Computer: Gain +2 to all attack rolls if you have a targeting computer.

Gunslingers and Ace Pilots: Most characters an only attack during the maneuvers stated on page 35 of GURPS Action 2. However, some characters have additional flexibility when attacking from a vehicle. Gunslingers may attack during the following maneuvers with hand-held weapons and Ace Pilots may attack during the following maneuvers with vehicle-mounted weapons:

  • No Attack Allowed: Disembark/Embark (Ace Pilots Only), Emergency Action, Hide

  • Attack without Accuracy: Mobility Escape, Mobility Pursuit, Move, Stunt, Stunt Escape

  • Attack with Accuracy: Disembark/Embark (Gunslinger only!), Force, Move and Attack, Ram

  • Attack with Accuracy +1: Attack

Missile Attacks

When making a missile attack, ignore the above rules for deceptive attacks, range, sensor locks and targeting computers, and ace pilots never add their accuracy to the attack. Instead, when rolling to hit, add accuracy, size modifier, your opponent’s ECM penalty and half of your opponent’s speed modifier as a penalty (rounded up). Explosive weapons without armor divisors may attempt an “air burst” for a +4, and treat a miss by 1 on an explosive weapon as a “near miss”: a hit but with 1/3 damage and no armor divisor.

Missiles have a static dodge penalty of -3.

You may make a missile attack in any circumstances in which you can make a normal attack. With an Attack, add +1 to accuracy.

Defenses

See GURPS Action 2 page 35. In addition, characters with Ace Pilot gain +1 to their first vehicular dodge if they chose a Stunt maneuver (Whether or not it succeeds, the erratic motion is enough to throw off your opponent’s attack).

Advantaged: If you attempted to escape and you gained Advantage, add +1 to all Defense rolls this turn.

High-G Dodge: If the vehicle has an acceleration of 40 or more, or has a move of 400+, it can make a High-G Dodge. This adds +1 to the dodge, but the pilot must make an HT roll. This HT roll gets +2 if the vehicle has a G chair or if the pilot wears a G-suit. On a failure, the pilot loses fatigue equal to the mari

Missile Defense

If the attack is a missile, apply a dodge penalty of -3. If the vehicle is equipped with a Tactical ESM, add +1 to dodge missiles. If the vehicle has a decoy launcher, they may use it to add a further +2 to dodge. Alternatively, the defender may attempt to jam the missile. Treat this as a parry using (Electronics Operation (EW)/2), with a bonus equal to half the vehicle’s ECM rating, and +2 if the vehicle is equipped with a decoy launcher and uses it.

Decoy launchers have only so many charges. If the GM declares that the decoy launcher is “running low,” roll 1d6: the result is how many times you may benefit from the decoy launcher rules.

If the missile is explosive (without armor divisor) and the vehicle defends with a margin of 0, treat the attack as a “near miss”: a hit that inflicts 1/3 damage. If the attack was already a near miss, then it misses entirely.

Force Screens

If the vehicle is equipped with a Force Screen, the DR provided by the Force Screen is ablative. Every point of damage it absorbs reduces the total DR of the force screen by 1. The Force Screen automatically recharges to full power between manuevers! Adjustable force screens may choose to double the DR of a single facing, at the expense of halving the DR of all remaining faces; the facing configuration of an adjustable force screen must be determined when your maneuver is chosen.

Damage

GURPS Spaceships offers fairly detailed rules for damage which this new system does not. To compensate, the following table can be used whenever someone achieves a critical hit, or when a major wound against a vehicle is achieved.

3d

Damage

3

Critical System Damage: Inflict triple damage. If the vehicle is Flammable or Explosive, roll HT (-3 for Explosive). If the roll fails, the vehicle explodes next turn.

4

Cascading failure: Inflict double damage. Roll twice more.

5

Gaping Armor Hole: apply only half DR to this attack; further attacks may attack this point for -5, and if they hit, they may ignore DR.

6

Damaged Controls: -2 Handling until repaired and the ship has a “Close Call” Wipeout and must make an Emergency Action next turn.

7

Wounded passenger: choose one of the pertinent (player character or named NPCs) to take damage as though caught in an explosion (including a dodge roll, if that’s possible). If numerous nameless passengers exist, 10% of them die or are injured.

8

Wipeout: The vehicle has a “Close Call” wipeout and must make an emergency Action next turn.

9-11

Normal Damage only, no additional effects

12

Explosion: if the vehicle is Flammable or Explosive, roll HT (-3 for explosive). On a failure, an internal explosion occurs and damage is tripled.

13

Wounded Passenger: choose one of the pertinent (player character or named NPCs) to take damage as though caught in an explosion (including a dodge roll, if that’s possible). If numerous nameless passengers exist, 10% of them die or are injured.

14

Disabled Engine: power and engines fail. They can be restored with a passenger action and a roll of Piloting(Starship) -4, Spacer, or Electrician, provided the vehicle has Access space. This also causes a “Close Call” Wipeout.

15

Damaged Weapons: Half of all weapons (rounded up) are disabled until repaired

16

Force Screen Disabled: the ship loses Force Screen DR and will not regain it until repaired

17

Cascading failure: Inflict double damage. Roll twice more.

18

Critical System Damage: Inflict triple damage. If the vehicle is Flammable or Explosive, roll HT (-3 for Explosive). If the roll fails, the vehicle explodes next turn.





Thrill of the Chase

Pyramid #3/112 “Action” has Kelly Pedersen’s excellent “Thrill of the Chase” article, which adds all sorts of interesting complications we can use in chase scenes. I highly recommend it, and will borrow a simplified version for space.

Note that “space” in Psi-Wars is a very cinematic form of space. Asteroids aren’t remote mountains isolated by thousands of miles, but patches of densely packed boulders smashing into one another, and these patches might be scattered throughout an area near a planet, defying all astrophysics. Nebulas have ionic lightning churning in its stormy depths. Psi-Wars isn’t trying to offer realistic space combat (hence the use of aerial performance rules for its starfighters) but a fun form of space combat.

Space Terrain

Open Space is always Open Terrain. The maximum practical range for all fights within open space is Beyond Visual (once one reaches “Remote” territory, the combat/chase becomes more strategic, a long march with distant artillery bombardment rather than the cinematic, nail-biting combat of closer ranges).

Nebulas are Open Terrain but reduce the maximum range to Distant. Sensors require active use (no automatic detection) and suffer a -4. All missiles suffer a -4 to accuracy.

Debris Fields such as asteroid fields, ice patches or junk fields, are Normal Terrain. Maximum range is Extreme, and while fighters can operate normally, anything larger than a fighter treats it as rough terrain. Especially dense debris fields count as Rough for everyone!

The tunnels or canyons of an asteroid or an especially large battle station count as Tight Terrain. Fighters can fit, but treat it as rough terrain, and larger ships cannot fit at all. Maximum range is Long making these sorts of battles very close “knife fights”

Space Chase Events

Space is vast and empty and thus painfully boring, but not in Psi-Wars! While perhaps less dynamic and jam-packed than a planetary environment, a GM can use the rules from Thrill of the Chase to spice up a dog fight too!

Obstacle

The most common space obstacle is a single instance of an asteroid, comet or giant piece of space debris. Space is wide open enough that one can fly around it, or it might float out of your way, given time. Thus it can be circumvented with a single Stop maneuver, if you’re okay with “taking the long way around” which grants your opponent a free range shift, if they want it. You can also Stunt to get around it, or through it.

Plowing through such an obstacle (or blowing it apart with a Move and Attack) is more difficult. Treat the object as having 2d×100 HP; these are fairly small asteroids, but the smallest are easily as large and heavy as a fighter, and may even rival a dreadnought in size and mass!

Dead Ends

Space is too open to truly stop anyone, but if one arrives at an even larger asteroid, those bordering on planetoids, with tunnels large enough to hide a small spaceship. Ships that move towards a giant asteroid or icey body like this treat it as a narrowing of terrain from Open or Normal to Tight.

Bystanders

Most battles take place near planets with active traffic. Threatened bystanders might be a passing freighter or a passenger liner that suddenly shunts into real-space from hyperspace, unaware that it dose so in the midst of combat. They might suddenly arrive in the path of a ship and require extra consideration to avoid, or they might be hit by a stray attack and need some immediate assistance. Useful or Involved bystanders might be the authorities or potential allies that can be called upon to join the fray (local asteroid miners irritated at the Imperial presence, but not willing to openly fight). These might literally join the battle, or pass on messages or sensory information to help assist in finding or slowing the enemy party. An especially helpful example of a Useful Bystander might be a hyperspatial beacon, which can transmit navigational information, allowing for faster hyperspatial calculations for a quicker escape.

Opportunities

These represent battle-changing moments that grant options for Hide, Mobility Escapes, Mobility Pursuits, Stunts or Stung Escapes. Space offers few of your typical examples, such as a new vehicle or a change in the road, but it offers new and unique “cosmic” opporunities. Not every part of space will have the same opportunities, as the churning singularity of the death star of Styx offers different challenges than the traffic-heavy space around Denjuku.

  • Solar Flare or Ionic lightning Strike: A sudden flare of electrical activity jams sensors and communicators. This offers an ideal opportunity to hide, if the vehicle has the ability to “hide in open space” or is in terrain (such as a nebula or debris field) that allows for hiding. Also, during such an event, fighting with missiles or maintaining radar locks become difficult, which might change the dynamic of the fight.

  • Gravitational Wake: A large body moving at high speeds, such as a comet or descending meteor or the spinning of a black hole surrounded by debris, might allow vehicles to “pass in their wake.” This disrupts and distorts the hyperdynamic medium and may allow for very quick travel along predictable paths. This might allow for a stunt through the gravitational wake, or a mobility move as one “rides” the wake. These events tend to be short-lived.

  • Shunt Event: A large vehicle, such as an enemy naval vessel or an especially large passenger freighter or liner, can suddenly appear out of Hyperspace. Ultrascanners will warn of an impeding Shunt Event, but clever dogfighters can try to use it to their advantage, either putting the impending shunt even between themselves and their pursuers, forcing their opponents to go around while they traveled straight through, or trying to herd their target towards the shunt event so that it will momentarily block their passage. This can allow stunts or (for very clever ships) hide maneuvers.

  • Explosion: In a larger battle, if a large ship is suddenly destroyed, this sends out shockwaves and creates an instant debris field. The moment of destruction has a lot of power in it, and those too close to it might, themselves, be destroyed, and the sudden arrival of a debris field can be used by a daring pilot to force his pursuers into very tight and dangerous terrain.

Chase Circumstances

“Thrill of the Chase” offers an interesting Chase Circumstances table. A modified, space-appropriate version appears below.

3d

Event

3-4

Roll twice on this table

5

Giant asteroid/ice body/hulk reduces terrain to Tight

6

Opportunity appropriate to environment

7

Debris Field (or Debris Field ends)

8

Threatened Bystander

9-11

Nothing Special

12

Asteroid/Comet/Junk Obstacle

13

Useful of Involved Bystander

14

Debris Field (or Debris Field ends)

15

Opportunity appropriate to environment

16

Giant asteroid/ice body/hulk reduces terrain to Tight

17-18

Roll twice more on this table





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