Large vehicles are vehicles that are so large that they have many weapons and these weapons are not controlled by individual characters or NPCs. For example, a space ship or an aircraft carrier would both count as large vehicles. These vehicles have different rules that apply to them that separate them from normal combat. The most important thing that separates them is that they often have many weapon systems that fire at different rates, instead of characters that often have a number of attacks per melee that they use to perform actions.
A large vehicle is divided into a number of independent sections, one section represents the vehicle itself and the other sections represent each of the weapons systems. For example, a space ship with four different weapon systems would be divided into five sections. Each section functions relatively independently of the others in most circumstances, the only exception is initiative. Regardless of the number of sections, a large vehicle only gets a single roll to initiative and this roll applies to all sections for the entire melee round. All weapons fired and actions performed by the large vehicle use this initiative roll. If using the Revised Rules for Initiative, each section would get a chance to perform the special action at the beginning of each melee.
How a large vehicle attacks is very important and it can be difficult to remember how many times each weapon has fired, especially if a vehicle has hundreds of weapons spread over a large number of weapon systems. Using the Revised Rules for Initiative system, each weapon system fires a specific number of times per melee and therefore has at specific points in a melee. For example, a laser cannon system that fires four times per melee, and doesn't take its special action at the beginning of the melee fires on the following seconds in a melee round: 3, 6, 10, and 13. If a laser cannon does not fire on the appropriate part of the melee round, such as by not having a target within its firing arc, then its attack is wasted and cannot be used later in the same melee round. At the beginning of a melee round, when a ship can perform a special attack, a ship can choose to fire any or all weapons to fire. These weapons fire simultaneously, but each section requires its own strike roll and is considered to be a separate volley.
One important aspect of large vehicle combat is that all weapons that fire from a specific section against a specific target require a strike roll and they count as part of a volley. For example, a ship has four laser cannons and five ion cannons and both weapon systems have a rate of fire of four times per melee. At the first opportunity, the ship fires three laser cannons at target A, one laser cannon at target B, two ion cannons at target A, and three ion cannons at target C. The attacking ship would have to make four strike rolls, two for each target for each weapon system. Target A is being attacked by two volleys simultaneously, a volley of three laser cannons and a volley of two ion cannons. It is not possible to separate a volley into individual cannons. For example, the attack ship could not make a strike roll for each of the three laser cannons it fired against target A, it must be done as a volley, so either all cannons hit or all cannons miss. A large vehicle must decide where it is firing all of its weapons at a given point in time simultaneously. Using the example above, the ship would have to decide where all of its four laser cannons and five ion cannons were firing before it could make its strike rolls for those weapons.
Using this system, a large vehicle does not really have attacks per melee, instead its weapon systems make the attacks, but a large vehicle may need to perform other important tasks, such as accelerating, turning, attempting to dodge, and changing what objects its targeting computers are targeting. This is why a large vehicle is given a number of combat actions that it can use for a variety of special tasks. These combat actions represent a vehicle's commander giving orders and its crew performing actions and returning that information to the vehicle's commander. A vehicle with more efficient command and control facilities would have a larger number of combat actions then a vehicle without such equipment. Just like normal attacks, combat actions can be used at the beginning of a melee round as part of a special action.
There are two types of actions that a large vehicle can perform. The first type of action is considered to be a free action that a vehicle can perform once during each segment of a melee round, in order of initiative. These actions include changing targets for a targeting computer or beginning to acceleration a space ship. The second type of action requires the use of one or more combat actions and represents more complex orders that a vehicle's commander must give, represents the commander receiving a large amount of information, or represents something that is disruptive enough to the vehicle's crew that they require a combat action to recover from it. These actions include engaging complex maneuvers or activating an electronic warfare system.
By default all large vehicles have at least one combat action per melee round, although larger vehicles and vehicles with sophisticated command and control facilities will have more. The following is a list of what combat actions can be used for:
Two spaceships are facing each other. Ship A is a command frigate equipped with a missile launcher that fires once per melee and two laser cannons that fire three times per melee. Ship A has no combat bonuses, but it can perform four combat actions per round. Ship B is a small pirate vessel with six laser cannons that fire five times per melee. Ship B has no combat bonuses, but it can only perform two combat actions per round.
During the first round of combat, the two ships roll initiative with Ship A getting a 6 and Ship B getting a 12. Since Ship B won, it has the option of firing any or all of its weapons as part of its initial, beginning of melee round attack. Ship B decides to fire three of its laser cannons in such an attack. Since all three laser cannons are being used against a single target, they are fired as a volley. Prior to the pirate making the strike roll, Ship A decides that it will use a combat action to attempt an emergency dodge. Ship B rolls a 9 to strike and Ship A's dodge result is an unlucky 2. Failing the dodge, Ship A takes the full force of the volley. It is now Ship A's turn to do a special, beginning of melee round attack, but it chooses not to. After the special attack phase, Ship A has used its first combat action and has three remaining and none of its weapons have fired. Ship B has not used either of its combat actions and has fired three of its six laser cannons once.
As the melee round progresses, Ship B has the first chance to fire with the three laser cannons that it did not fire at the first of the melee, but since only one of them is facing in the direction of Ship A, it can only fire that one cannon. Not wanting to use another combat action to dodge the incoming attack, Ship A takes the hit. Unfortunately, Ship A did not realize how quickly Ship B could fire its laser cannons, because the next to fire are the three laser cannons that Ship B fired at the beginning of the melee. Since all three laser cannons face towards Ship A, Ship B fires them all as a single volley, making only a single strike roll for all three lasers. Using another combat action to perform an Emergency Dodge, Ship A is able to avoid two of the incoming three blasts from the volley.
Following the firing of the Ship B's three laser cannons is one of Ship A's three remaining combat actions, Ship A's two laser cannons, and one of Ship B's two combat actions. Since Ship B has the higher initiative, it chooses all of its actions first. From previous experience, Ship B knows that Ship A's laser cannons are very powerful, so Ship B uses its combat action to begin Erratic Maneuvers to make itself harder to hit. Ship A chooses to fire both of its laser cannons at Ship B, but it loses its combat action because it performed an Emergency Dodge earlier in the melee round. As the melee round continues, Ship B will quickly discover that even though its laser cannons fire more quickly, the combined power of Ship A's two laser cannons and the much larger number of combat actions that the ship can perform will eventually allow it to win the encounter.