Wednesday, August 21, 2013

Spaceships/JC: Corvettes vs a Strike Carrier Example Combat Revisited

So I've decided to start posting combat examples for GURPS Spaceships using the Jovian Chronicles conversions I recently did, more or less in response to a thread on the SJ Games forums asking for turn by turn examples of GURPS Spaceship combat. I started with a bunch of small craft fighting each other and went on to small craft against an escort ship. I tried a bunch of escort ships against a strike carrier, and it went poorly, so now I'm trying it again with some slight changes.
I'm trying to run these examples without any house rules. I'm not doing a perfect job of that, though. One issue is that technically, a single pilot/gunner can't fire two different weapons (GSS1 p53). I don't consider it at all abusive to let the pilot/gunner use both his main weapons and his point defense weapons at the same time, with appropriate multi-tasking penalties, and I didn't notice that rule on my first read through. I'm not about to go back through these examples and add a semi-competent AI gunner, but you can do that mentally if it really bothers you.
Another issue is that multiple identical weapons in a turret mount cannot fire together (GSS1 p57). I didn't notice that rule either. Tripling the number of rolls made for turret attacks is not going to make these examples shorter or easier to read and I doubt it would affect the outcome. Again, you can do it mentally if it really bothers you.
Thanks to the eagle-eyed readers of the forum and on the comments below who pointed out my mistakes. It's a learning experience and I welcome the feedback.

Scenario: The Surprise of the Vigilant

While on routine patrol of the asteroid belt, the JAF Valiant-class strike carrier Vigilant sends most of her strike-fighters and exo-armors to deal with pirates attacking a nomad ship. The Jovian pilots easily deal with the pirates and return to their carrier, except for a pair of Lancer aces who get overexcited and spend all their delta-V reserve. The Vigilant heads after them to prevent them from traveling into interstellar space.

The Vigilant's radar then picks up two new shapes coming around an asteroid: a pair of CEGA Bricriu-class corvettes! The Briks light up their drives and angle for attack vectors while signaling the Vigilant to surrender. The Jovian exo-armors are still rearming and refueling in the hangar and won't be ready to launch for another twenty minutes, but Valiant-class strike carriers are meant to handle themselves in dangerous situations, and the Vigilant prepares to see the hostiles off.

Special Rules and Command Orders

Objectives: The CEGA corvettes want to destroy the Vigilant. The Vigilant wants to destroy the CEGA forces and needs to continue on this course in order to recover her errant strike fighters.

Retreating: The Vigilant may not attempt a Retreat maneuver until she has completed five consecutive Contolled Drifts, Hold Course, Evasive Maneuver, or Closing maneuvers, since she basically needs to get past the corvettes on this path to catch up with her strike fighters.

The Briks are trying to destroy the Vigilant, and while CEGA high command might consider trading the both of them a good deal for one strike carrier, the crews of the Briks don't. After either Brik has had more than half their medium batteries disabled or have been reduced to -0 dHP or less, any remaining Briks can attempt to retreat.

Opening Turn: The Vigilant is taking a very low acceleration Hold Course maneuver to catch up with strike fighters when the CEGA corvettes appear from behind an asteroid at Long range. Her PDS gunners are taking Aim and Wait (Point Defense). Her captain has just performed Space Tactics to determine what the Briks are attempting.

Both of the CEGA Bricrius will act before the Vigilant. The CEGA start off in formation but do not have to maintain it. The Briks have to win at least one maneuver contest in order to reach neutral range with the Vigilant.

Turn Length and Scale: All of the ships have 0.5G of acceleration, and 20 mps of delta-V, but the Vigilant has several Extreme range weapons. The best scale is Close Scale and the best Turn Length is 1 minute per turn.

delta-V reserves: The Vigilant and the Briks all have 20 mps of delta-V reserves. They can spend 0.3 mps of delta-V at 0.5G to get a +1 acceleration bonus or 1.2 mps of delta-V at 1G to get a +2 acceleration bonus.

The rapid increase in delta-V reflects the doubled fuel consumption for high thrust operations.

Skill Levels and Crew Actions: All ships are fully staffed with professional crew, giving them Skill-14 at whatever they're trying to do. They can perform one of every type of task every turn without multi-tasking penalties, except for Gunnery Tasks, where they can perform 1 Gunnery Task for each of their weapon batteries.

Other Notes: These are optimized Bricrius that have swapped the Habitat and Tertiary Weapon Battery from the forward hull with the two KKC Medium Weapon Batteries in the central hull. Their KKCs have slightly worse arcs of fire, but the ships don't explode as soon as someone fires a missile at them from behind.

The Vigilant is also an optimized version of the normal Valiant-class strike cruiser. The 10 GJ Spinal Laser Battery is downgraded to a 3 GJ Laser fixed Main Battery in the forward hull; the forward hull Hangar bay at [4] is moved to central hull [core]; the central hull Fusion plant at [3] is removed; and the rear hull spinal battery is removed. Downgrade the armor from nancomposite to advanced metallic laminate (dDR 30) and add advanced metallic laminate to the various open spaces at forward [4], central [3], rear [6]. Change each hull's armor to 60 dDR, reduce the cost by $700M. The "spinal laser" now does 3dx10 d-damage and has a range of L/X.

Play of the Encounter

CEGA Turn 1: The Briks are starting at long range against a weapon that can blow through their armor and hulls in a single shot and outranges their guns to boot. Closing in on Vigilant is mandatory, and hopefully at short range their KKCs and particle beams can overwhelm the Vigilant.

Bricriu 1 starts off with its captain performing defensive space tactics, resisted by the Vigilant's captain. The rolls are 13 for the Brik and 12 for the Vigilant, so there's no effect. Then the navigator plots a tactical course, rolling 10 against Navigation-14 and providing a +1 bonus to the pilot. The pilot burns 1.2 mps of delta-V at 1G to get a +2 acceleration bonus and attempts a closing maneuver, rolling against Pilot-14, +2 for acceleration, -1 for handling, +1 for navigation, and getting a 15 against a net 16 (MoS 1). The Vigilant's pilot contests with a 9 against Pilot-14 and a -2 for handling, and wins his roll by 3 and the contest by 2. Bricriu 1 ends up neutral to the Vigilant, at long range with the front hull facing. Should the Vigilant survive this turn of attacks, Bricriu 1 is a likely target of the spinal laser. At this range, Bricriu 1 has no weapons that will reach, and the gunners decide to Aim and Wait on the off chance that the Vigilant decides to close with them.

Bricriu 2 sees no value in hanging out at the edge of space and being demolished by long range fire, and chooses to break formation and try to pincer the Jovians instead. She will also start with defensive space tactics, resisted by the Vigilant's captain. The rolls are 10 for the Brik and 15 for the Vigilant, so Bricriu 2 will get +1 to Dodge this turn. Then the navigator plots a tactical course, rolling 11 against Navigation-14 and providing a +1 bonus to the pilot. The pilot burns 1.2 mps of delta-V at 1G to get a +2 acceleration bonus and attempts a closing maneuver, rolling against Pilot-14, +2 for acceleration, -1 for handling, +1 for navigation, and getting a 6 against a net 16 (MoS 10). The Vigilant's pilot contests, also with a 6, against Pilot-14 and a -2 for handling, and wins his roll by 6 but loses the contest by 4. Bricriu 2 closes to Short range, with her front hull toward the enemy.

Her gunners open up with the port particle beam battery. They roll a 10 against a base Gunnery-14, +10 for target size, -3 for sAcc, -8 for range, +0 for RoF, -2 for ECM, and succeed by 1 against a net 11. Two particle beams hit, and the Vigilant tries to dodge with a 12 against a 7, +1 for ECM, +1 for turn length, missing by 3. The beam's AP modifier of (5) is reduced to (3) by the hardening of the Vigilant's armor, so the effective arrmor dDR is 20. d-damage for the two shots is 52 and 63, reduced to 32 and 43 of penetrating d-damage on locations 2 and 6. Each hit does at least 10% of the Vigilant's 150 dHP and disables the system, so the reserve fuel for the exos in location 2 and the cargo hold in location 6 are disabled. Vigilant is also reduced 75 dHP and has to make 2 surge checks against its HT of 13, all of which it passes.

Then Briciu 2's gunners open up with the starboard particle beam battery. They roll an 8 against a base Gunnery-14, +10 for target size, -3 for sAcc, -8 for range, -2 for ECM, and succeed by 3 against a net 11. 4 particle beams hit, and the Vigilant tries to dodge with a 15 against a 7, +1 for ECM, +1 for turn length, missing by 2. The beam's AP modifier of (5) is reduced to (3) by the hardening of the Vigilant's armor, so the effective arrmor dDR is 20. d-damage for the 7 shots is 53, 54, 53, and 54 which is reduced to 33, 34, 33, and 34 penetrating d-damage on locations 2, 3, 1, and 6. Each hit does at least 10% of the Vigilant's 150 dHP and disables the system, so the reserve fuel for the exos in location 2 is destroyed, the other half of the hangar bay is location 3 is disabled, the armor location at 1 is disabled, and the cargo bay is destroyed. The Vigilant is also driven to -59 dHP and has to make 4 surge checks against its HT of 13, all of which it passes.

Bricriu 2 decides not to fire the KKCs, since the Vigilant's powerful PDS suite is still available and is more than sufficient to intercept the slow-moving attacks.

Vigilant Turn 1: The Vigilant is hurting, but hopes to be able smash the Briks and still recover her strike fighters. Taking Evasive Action would be desirable, but that means turning the spinal laser away from the Briks. Instead, the captain orders increased acceleration on the current course.

The captain plots offensive tactics against Bricriu 1, rolling a 13 against a 9 to no effect. Then the navigator plots a tactical course, rolling 10 against Navigation-14 and providing a +1 bonus to the pilot. The pilot burns 1.2 mps of delta-V at 1G to get a +2 acceleration bonus and holds course. The Vigilant remains at long range to Bricriu 1 and at short range with Bricriu 2, with her front hull facing the distance foe and her central hull facing the closer enemy.

The spinal laser glitters in darkness, attempting to gut Bricriu 1. The gunner rolls a 10, against Gunnery-14, +9 for target size, +3 for sAcc, -12 for range, -2 for being below 0 dHP, and -1 for the target's ECM (halved for the tactical array), and succeeds by 1. Bricriu 1 attempts to dodge, rolling a 14 against a base 7, +1 for ECM, and +1 for turn length, but fails. The laser does 3dx10 bur d-damage, resisted by the Bricriu's dDR 40. Rolled damage is 107 against front hull location 2, and armor location 2 is destroyed and the Bricriu takes 67 dDamage of penetration. With 33 dHP, the corvette is certainly shaken but not out of the fight.

At the same time, the twin KKC turrets open up on Bricriu 2. The gunner rolls a 10, against Artillery-14, +9 for target size, -6 for sAcc, -3 for 2 mps of relative velocity, -1 for ECM, -2 for being below 0 dHP, and +1 for RoF. One projectile hits, and is trivially intercepted by 2000 point defense laser shots. The twin missile bays also belch their missiles, rolling an 11 against Artillery-14, +9 for target size, +2 for sAcc, -3 for 3 mps of relative velocity, -1 for ECM, +4 for RoF, +4 for proximity fuses, and netting an MoS18 against a net target of 28. 19 missiles hit, and Bricriu 2 zaps them with another 2000 laser shots. The point defense gunner has Gunner-14, +0 for sAcc and range, -1 for target size, and +11 for RoF, with a target of 24 and a roll of 9. MoS is 15, and though most of the missiles are intercepted, 3 get through. The missiles hit locations 5, 2, and 4 for 6dx4 d-damage each, resisted by armor dDR 40. D-damage rolled is 101, 72, and 98, and penetration is 61, 32, and 58. The defensive ECM system is destroyed, one of the KKCs and both armor locations are disabled, and and the other KKC is destroyed. In the forward hull, only the forward fusion plant and the bridge are unscathed. The Bricriu is also reduced to -51 dHP.

CEGA Turn 2: The CEGA Bricrius are in bad shape, and move to withdraw behind their asteroid. The Vigilant is in no shape to pursue and lets them depart.

Result

This is a draw. The CEGA failed to destroy the Vigilant, but the Vigilant will be under repair for months.

Conclusion

This play-through was different, but not markedly better, than the previous example. The Valiant is somewhat lightly armed and armored for a SM+10 craft, but a single salvo by a not particularly well designed SM+9 craft was enough to put it into the negatives. Only some cheesy missile tactics allowed it to damage Bricriu 2, and without those tactics, it would have been crippled on its next turn.

Missiles are still too effective for my tastes, and point defense is still too all or nothing. Particle beams also hit too hard.

I'd been enjoying the Spaceships combat system, but this fight soured it for me.

12 Hours Later: After some more thought, I'm feeling less distressed. I still don't have a solution for point defense, but I have some ideas toward reducing missile damage (which may end up just being giving everything a hardened kinetic force field for free but I'm still thinking). For particle beams, using a variant of the laminate armor rules from Pyramid 3.40 would give armor doubled dDR against them. Particle beams would still have a role as armor penetrators, but they wouldn't be so overwhelmingly good at it.

An even simpler solution would be to use the altered dHP rules from Pyramid 3.34. If dHP scales with the square root of mass, instead of the cube root, larger ships are already more survivable. It'd be pretty easy to scale disabling damage for subsystems, so it only takes damage greater than 1/300 of total dHP to disable a single weapon in a tertiary battery. That would leave a role for small craft that can force a rendezvous against a large ship, target the weak points of various weapons at rendezvous range, and disable the ship piecemeal.

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