A few months ago, I released Voidjumpers of Space, a D&D 4E conversion of Spelljammer, the classic “Dungeons & Dragons in space” setting. Voidjumpers is an original universe that attempts to replicate the overall Spelljammer feel, so anyone can use and expand upon it.
If you’re not willing to download the whole thing (it’s free), here are rules for running ship combat in space in D&D 4E, along with a sample ship.
Combat rules for ships in space work almost exactly the same as person-to-person combat rules, except as noted in this section.
Movement and Positioning
Each ship takes up at least one square on a 1” grid. One inch on the grid is equivalent to about 50 feet.
Ships may overlap each other on the grid, representing one ship sailing above another.
You are free to simulate 3-dimensional positioning, but this is unreasonable to assume for most player groups. All these rules will work for either 2-dimensional or 3-dimensional movement.
The ship’s orientation does not affect the ability to fire any of its weapons. Players may, at any time, change the square on their ship from which their weapons are being fired. This prevents the need to track the exact location of each weapon on each ship.
You are free to assume that ships can only move forward in one direction, and must be turned as through navigating through water. For simplicity’s sake, this document assumes that ships are not limited in that way, and can move in any direction without turning.
Each ship can take several standard actions, one per weapon. The Actions stat lists the maximum number of standard actions that the ship can take per turn, as limited by the size of the crew.
There must be at least one conscious crew-member for each standard action taken by a ship each turn. If a ship can take 5 standard actions maximum, but at the beginning of its turn has 3 conscious crew members, it can only take 3 standard actions during that turn.
If the pilot is unconscious, the ship can take no actions.
Initiative and Defenses
Each ship has its own AC and Fortitude. It takes the Initiative, Reflex, and Will scores of its pilot (the magic user who is controlling the ship’s Illumar).
Each weapon takes the Initiative, Reflex, and Will scores of the character using that weapon.
If the pilot becomes unconscious during a battle, the ship’s Reflex and Will defenses are set to half their normal values. If no pilot is controlling a vessel, its Initiative, Reflex, and Will are 0.
Each weapon on-board a ship must be controlled by a sentient creature.
Each weapon on a ship can also be the target of an attack, with a negative on the attack roll equal to the smallest number of empty squares between the attacking and target ships. So, a ship 2 squares away from another would take a -2 when targeting a specific weapon on another ship.
When targeting a ship’s weapon, use the weapon’s defenses.
Ships and ship-based weapons can only be damaged by ship-based weapons, or close and area attacks that damage objects. When a ship is bloodied, all attacks made within the confines of that ship—including those made with ship-board weapons—take a -2 penalty on attack rolls.
Each hit point of ship damage can be repaired with one man-hour of work. Ships do not have healing surges, and cannot recover damage in any way other than by repair.
When a ship is reduced to 0 or fewer hit points, it cannot move and all its weapons cannot fire.
Ships do not have healing surges.
Ships can only be subject to the following ongoing conditions:
If a ship takes a condition, all weapons also take that condition. The pilot performs the saving roll to shake the condition on his or her turn, and if successful, the condition is lifted from the ship and all its weapons instantly.
Character Actions During Battle
Individual characters other than the pilot may take actions during a ship-to-ship fight (particularly while grappling with another ship). Initiative is rolled normally.
It is sometimes convenient to begin a battle by rolling initiative only for ships, and allowing all weapons on these ships to fire simultaneously during its turn. Later, when players want to get their characters into the conflict, you can roll for their initiative.
Grappling between ships literally involves grappling hooks. All ships come with at least one grappling hook.
To grapple a ship, make an attack with a bonus equal to your ship’s level against the Reflex of a ship that is 3 or fewer squares from your ship. A ship may attempt to break a grapple using its pilot’s Wisdom modifier plus half the pilot’s level against the Fortitude of the grappling ship.
Characters on a ship that is grappling another (no matter which ship initiated the grapple) automatically gain access to the leap power. At the beginning of a character’s turn, a successful Athletics check with a moderate difficulty allows the character to leap onto a grappled ship as a move action. That character must place him or herself on a square on-board the enemy ship as close as possible to the ship from which that character leaped. The character may then act normally while aboard the other ship.
If the leap fails, the character lands on his or her own ship, and takes damage as though falling one square.
If a creature is using a ship-board weapon, a successful personal grapple check can be used by another creature to pull that creature 1 square away from the weapon, freeing it for anyone’s use.