The other day one of my readers asked me if I had any ideas for stats for the Crusty starships made by Ground Zero Games. They're one of the few Full Thrust fleets I haven't painted, and they do have unofficial stats at Dean Gundberg's Full Thrust Resource page
but Jon Tuffley's comments on seeing them as using energy weapons did get me thinking about how to model a District 9-style zap gun as a starship weapon. Here's my take on the subject, along with some random images for those who are just here for the pictures.
A selection of space stations
Arc Lightning Cannons (ALC hereafter):
These weapons have exactly the same mass, cost, and firing arc options as standard beams from Fleet Book 1 from Ground Zero Games, which can be downloaded here:
ALC fire is resolved almost identically to standard beams, including number of dice rolled, range bands, and the effects of screens on damage inflicted. The difference crops up when you roll sixes. With a normal beam each six would let you roll another "penetrating damage die" for damage ignoring screens, with further sixes chaining ad infinitum.
ALCs still look for sixes (which will inflict 2 damage each on the primary target, or 1 damage if facing level 2 screens) but instead of doing further damage to the target, they produce one "arc attack" die for each six rolled, which are assigned to other enemy ships within 6MU of the original target. Arc attack dice must be spread as evenly as possible between valid targets, but you can choose which valid targets to assign "odd" dice to.
For ex, if you have three sixes on your initial attack roll and there are two enemy ships within 6MU of the original target ship your three arc attack dice must be split with 1 die on one ship and 2 dice on the other. If there were only one enemy ship in "arc" range, all 3 dice would be assigned to it. If there were no enemy ships within 6MU of the original target the arc attack dice are simply wasted.
Note that assigning arc attack dice doesn't require separate fire control systems, and both the 6MU range and line of sight are measured from the enemy ship the dice are "arcing" from, not the ship actually firing.
After assigning all arc attack dice, roll them against each affected enemy ship as though they were standard beam dice, with the exception that they never reroll sixes for extra damage, nor do they produce further arc attacks of their own. These beam dice are affected by screens and other defenses as normal.
When a single ship with ALCs is firing at multiple targets in the same turn, resolve the fire at each target (including any arc attack dice) completely before going on to the next. Ships that are reduced to zero hull from one attack are no longer valid targets for future arc attacks, obviously.
How do we still not have enough guns?
Now, let's try some practical examples of the arcing mechanic using the images below. Our Big Red sphere (on the right) has 12 class 1 ALCs with 12Mu range, 360 degree firing arcs and two fire control systems. The other ships are all enemies, and none have screens except for Gray (at the top center) which has level 1 screens. All except Blue (on the far right) are within 12MU of Big Red.
Big Red decides to shoot everything it can at Purple, the closest target. Purple has no screens, and the 12 dice come up 1,1,2,2,3,3,3,4,5,5,6,6. This scores 7 damage (3 for the 4,5,5 and 4 for the 6,6) and the sixes produce two arc attack dice. The only enemy ship within 6MU of Purple is Gray, so those two dice are assigned to it, and roll 4,4. Gray has level 1 screens, so no damage is scored. Big Red grumbles about bad luck.
In an alternate universe, Big Red decides that it really, really wants to score damage on Blue, which is on its last hull box but just out of range at 13MU. Selecting Green as a target instead, 12 dice roll 1,2,2,4,4,4,5,5,5,6,6,6. Green has no screens, so it takes 12 damage and dies since it was down to 8 hull anyway. Before it's removed, there are three arc attack dice to assign from the sixes. Big Red has to split them as evenly as it can between Gray and Blue, which are both within 6MU of Green and therefore valid targets. It chooses to assign two to Blue and one to Gray. The dice on Blue come up 3,5, scoring one damage and finishing off the last box. Big Red cheers. The single die on Gray rolls 4 and scores no damage since Gray has level 1 screens. Gray points out that it is clearly invulnerable.
In yet another universe, Big Red decides to split fire, assigning 4 dice to Green (and hoping to arc to Blue to finish it off) and 8 dice to Gray (who has a chip on its shoulder). Deciding to resolve the shot on Gray first, Big Red proceeds to roll 1,6,6,6,6,6,6,6. Gray takes 14 damage, dies despite its screens, and demands to see those dice. While Gray is occupied, Big Red has to assign 7 arc attack dice, splitting them evenly between Purple (who gets 3 of them) and Green (who gets 4). The dice on Purple come up 1,3,4 and do one point of damage. The dice on Green continue to defy probability and roll 6,6,6,6 to do 8 damage, exactly the amount of hull Green had remaining. At this point, all the fire (and arc attacks) on one target has been resolved and both Gray and Green are removed from the table. The 4 dice assigned to Green go to waste since it's (implausibly) dead so Big Red doesn't get a chance to roll (more) sixes and arc damage into Blue. Probably should've chosen to resolve the shot on Green first, but after that string of sixes who can complain?
Space stations again
Design notes and closing thoughts:
ALCs will tend to score slightly less overall damage than standard beams (since their arc attack dice have to penetrate screens and don't chain off of sixes) and the damage will be spread over more targets, with most of it hitting the main target of each shot. The amount of damage inflicted on secondary targets tends to be light but can easily finish off a cripple or badly hurt smaller ships. You can also (if your main target is positioned just right) sometimes arc damage into targets you couldn't fire at directly, either because they were slightly out of range, out of your firing arc, or hidden by line of sight blocking terrain.
Players wanting an "energy weapon" Crusty fleet can easily swap ALCs for Rocket Cannons class-for-class in the playtest stat page, since they all have the same costs and mass requirements. The arc mechanics are also good for encouraging people to spread out a bit, for punishing strikeboat swarm tactics, and for representing settings where common weapons have a "splash" effect. E.E. 'Doc" Smith's space combat is full of "coruscating plumes of lambent energy cascading from hard-driven defensive shields" as one example.
The basic arcing attack rules could theoretically also be applied to the playtest Graser rules from here:
Call them Heavy Arc Lightning Cannons, and have sixes rolled by your pseudo-graser produce arc attacks instead of doing more damage to the main target as with ALCs. Hits caused by "graser" arc attack dice turn into 1d6 damage just like the original attack. This would definitely be at least a x4 Mass cost weapon (as with the regular "reroll on six" graser) and I'd playtest it with x5 instead. The amount of arcing damage will be more meaningful, and the ability to stretch the rang by another 6MU with a good arc is likely to matter more. It would also reduce the tendency for grasers to grossly overkill smaller targets while helping them spread damage around more efficiently.