These options can be combined with TL9-12 or superscience beam weapons to create extremely powerful or efficient weapon systems. It’s possible to add superscience upgrades to weapons that do not themselves require superscience. For example, a laser rifle (TL10) may be upgraded with grav focus (TL10^) technology.
By spreading the time it takes to generate a energy beam or bolt over a longer period and therefor reducing the power load (the power supply has less wattage it needs to regulate, the cooling system has more time to vent waste heat, and so on), it is possible to reduce the size and cost of a given beam weapon (the main beam generator however would still have to be full sized). The trade off is a delay of several seconds between firings.
Unless you switch the weapon off, after firing the weapon will automatically begin charging up again. While charging the weapon will either have a visual indicator on it showing how much longer until it is charged or will transmit the information to your HUD. While charging you are free to do other actions. Once charged the weapon will either flash, send a message to your HUD or admit an audible tone or transmit one to any headphones you are wearing. If you are in the middle of battle or other high stress situations and do not have a clear line of sight to an indicator, you can figure time remaining by making an appropriate IQ based Beam Weapons roll.
If you have to power down the weapon without firing it, the built-up energy needs to be discharged first. This takes just as long safely discharge the weapon as it takes to charge it, except for plasma weapons, since they need to cool and vent the plasma. It takes plasma weapons 4 times as long to safely discharge, during which it will vent the cooled plasma as hot gas. This gas is vented away from the operator and is generally cool enough to be safe but can cause minor burns if your hand is held too close to the vents (treat as moderate pain, does 1d-4 burn if held against it for a full second).
Ordinary beam weapons have cooling systems, but sustained fire can overheat them. The GM can ignore heat in most situations, but have the weapon overheat if dramatically appropriate. However, for crunchier rules, read on.
For a given type of energy weapon at its TL of introduction (see here for some guidelines on what TL counts as a given energy weapons intro TL), with a standard barrel, you can sustain the following rates of fire:
Sustained Fire: Bursts of less than RoF in length, with pauses of 4-5 seconds; overheats after 600 shots.
Rapid Fire: Bursts of less than RoF in length, with pauses of 2-3 seconds; overheats after 300 shots.
Assault Fire: Long bursts or bursts of less than RoF in length, with no pauses (as in typical action-movie scenes); overheats after 150 shots.
Multiply these values by 2/3rds for early versions of a given energy weapon that are available one TL early, by 1.5 for a TL+1 version and by 2 for TL+2 and higher versions.
Note that these are estimates, and that specific weapons may be able to have slightly higher or lower levels of sustained fire.
If you exceed these values, drop the weapons Malf. rating down one level (and -2 to Acc if a plasma weapon). If you let the weapon cool down for at least 15 minutes, these penalties will pass, but if you exceed the sustainable fire limit by 3 times or more this penalty becomes permanent, and you must make a HT check for the weapon; on a failure the weapon burns out and needs to be replaced.
For a greater sustained rate of fire, heavier or more barrels are needed. We'll cover more barrels in a second but if you want an energy machine gun, use the following options.
Standard Energy Machine Gun Barrel: Increase weapon weight and cost by ×1.5 but double the weapon's sustainable rate of fire.
Heavy Energy Machine Gun Barrel: Increase weapon weight and cost by ×2 but quadruple the weapon's sustainable rate of fire.
This can be combined with Swapping Barrels, below.
One common trick used by regular machine guns to let them keep firing without risking barrel damage is to give them quick-swap barrels. If you want to design an energy weapon that can swap barrels, assume that an extra barrel or focal array is half of the weapon's weight and cost. It takes 5 ready actions to swap a barrel at TL9; at higher Tech Levels better modular technology drops this to 4 ready actions at TL10 and smart matter modules drops this to 3 ready actions at TL11+.
So what advantage does having a Gatling-style action give energy weapons? For conventional firearms, a Gatling action lets a weapon cycle rounds faster and lets it sustain fire for longer by using many barrels. With energy weapons, cycling the action isn't a problem since it's all electrical (well, with the exception of plasma weapons) with the limiting factor being how robust of a power supply it has. This leaves the increased ability to sustain fire. While this limits the usefulness of this option for energy weapons, it is is still a very viable option if you need a weapon that needs to be able to fire continuously (such as a support/suppression weapon or a point defense gun) since, while still fairly heavy, adding more barrels with the Gatling option is lighter and cheaper then making high-RoF weapons with heavier barrels.
To add a Gatling action, simply design an energy weapon as normal. Just keep in mind that you'll want a high rate of fire, and keep in mind that gatling weapons don't need super heavy barrels, so to save weight, a normal or a standard energy machine gun barrel is all you usually need.
For safety reasons as well as maximizing the weapon's usable lifetime, beam weapons often only fire shots at half their barrel and cooling systems' max output. Due to this, it is possible to “hotshot” your weapon, modifying it to increase its performance at the expense of making it more likely to malfunction.
Beam weapons can be modified to fire hotshots. A hotshot counts as two shots. Multiply damage (or radius of effect, or HT/Will penalty) by 1.3, or add +1 damage per die, and multiply range by x1.7. When firing a hotshot, the weapon has a base malfunction number of 14 (modified upwards if Reliable).
Plasma guns that use power cartridges cannot fire hotshots, but can be loaded with “hot” power cartridges (p. 127) which have the same effect.
Effects of Overheating: If a beam weapon has overheated, it can still be fired, but will malfunction on a 14 or more (12 or more if firing hotshots while overheated) until it has been allowed to cool for at least a minute.
If a beam malfunctions, roll on the table on p. B407.
Modifying for Hotshots: To modify a beam weapon for hotshots, choose whether you want the weapon to always shoot in hotshot mode or if you can switch it off and on.
To set it to always on requires a relatively simply procedure; it takes 10min and roll against Armoury (Small Arms)+1. If you want modify it so that can switch the hotshot effect off and on, this is an average procedure and it then takes 12hrs and a roll against Armoury (Small Arms). It takes a ready action to switch between modes unless you have the Lightning Fingers Perk. Alternately, either option can be built at the factory for no additional charge (beyond any costs for Reliable weapons, to reduce the chances that it'll blow up…)
Legality of hotshotting depends on where and when it was performed, but generally has an LC one less than the base weapon.
Weapons with extended cooling systems can fire hotshots without overheating, although the Malf chance is still there; see Cooling Systems under Beam Weapon Design.
Many science fiction settings assume beam weapons can fire continuously for extended periods. The superscience power cell option multiplies the weapon’s number of shots by 5. Note that the Shots listed for all beam weapons in the GURPS Basic Set assume superscience power cells; divide Shots by 5 if using mundane cells.
A field-jacketed beam is enclosed in a force field or space-folding effect that prevents interference with atmosphere (or lack of atmosphere, as the case may be). This technology allows ultraviolet, X-ray, and gamma-ray lasers to be effective in atmosphere, and charged particle beams, electrolasers, and sonic weapons to work normally in vacuum. Beam weapons that cannot otherwise function underwater also do so at normal efficiency. At the GM’s option, field-jacketing a laser or other beam may make it visible, even in vacuum. This may explain the pretty colors observed in space opera movies! Field-jacketing can be added to all beam weapons (although some types may not need it). It’s a standard superscience space opera effect, and doesn’t have to cost anything. A field-jacketed weapon may also be twice as expensive as one without this feature.
This uses a hypergravity field to create a synthetic virtual lens that can focus and/or accelerate an energy beam. The technology trades beam energy for range, and permits space battles over thousands or millions of miles, rather than hundreds.
Grav-focusing is available for any type of laser, for microwave beams, and for any type of particle beam. It is usually used only on larger weapon systems, such as vehicular laser cannon.
Each level of grav-focus halves the damage but multiplies the range by 10. Up to (TL-9) levels of grav focus are possible. Gravity focus can always be turned off. If so, the weapon inflicts its normal damage. Each level doubles the weapon’s cost.
Any beam weapon may take this option. The beam travels instantly to the target at many times light speed. Treat the beam as field-jacketed (above) – that is, it ignores any of the usual environmental restrictions that might affect it (so a laser beam can travel underwater, etc.). In addition, its 1/2D range becomes the same as its max range. Accuracy does not increase, but the user suffers only half the usual speed/range penalties. For example, a target 100 yards away is -5, not -10.
These beams may be subject to setting-specific restrictions similar to those that apply to faster-than-light travel.
They usually only function in vacuum (although the GM may rule otherwise) and may only function when far away from a sizable gravity well, such as that of a planet. These beams also imply the existence of instantaneous faster-than-light communications and sensors, which would use similar technology.