Electromagnetic guns

We can use electromagnetism to make things move. The most familiar way to do this for many of us is to use a rotary electric motor, which turns electric power into the rotary motion of a shaft. This can be use to spin a drill bit or a saw or turn the wheels on a car. But not all electric motors are rotary in nature. Any rotary motor can be unrolled, so to speak, to turn it into a linear electric motor. Now you are using electric power to move an object back and forth. if you only move it forth, and you move it forth very quickly, and you don't bother to catch the forward moving part when it leaves the motor, you have a gun.

Common features of electromagnetic guns

There are many different kinds of electric motors. They all have gun versions. Different kinds of electromagnetic guns have different advantages and disadvantages. But there many features that are similar about them as well.

Charging equipment

An electromagnetic gun requires high power to be delivered in a very short pulse, on the order of a millisecond long. For artillery or naval canons, this can result in an instantaneous power of tens to hundreds of gigawatts! Unless the electromagnetic gun is directly plugged in to the full electrical output of a major regional power generating station (and you are willing to cause blackouts when it fires), you won't be able to directly deliver that kind of power from your main power supply. Instead, you will need to gradually build up energy over time, storing it in some kind of equipment that can deliver the stored energy in a very fast pulse. Common ways to do this include charging up capacitor banks or spinning up a compulsator (basically a flywheel attached to a generator). At least one research program used a massive inductor to store the energy. Other potential energy accumulation systems include other varieties of flywheel energy storage as well as superconducting magnetic energy storage (which is still an inductor, but a particularly useful form of inductor if you have the tech to make it convenient).

In most cases, the energy accumulator system will store enough energy for one shot. Your rate of fire will depend on the time it takes for your primary power supply to build up enough energy for one shot.

Another option are explosively pumped flux compression generators, which store the energy as high explosives and give a one-time surge of power when the explosives are detonated to drive your generator. Because the generator and associated equipment do not usually survive this process, it can be a rather expensive method to power your gun. Combined with the need to carry a magazine that could potentially explode, this starts to eat into many of the potential advantages of electromagnetic guns over conventional guns.

Flywheels, capacitors, and inductors all generally give a sudden surge of power at the beginning that decays over time. An explosively pumped flux compression generator, on the other hand, delivers a pulse that ramps up from zero to maximum power right at the end of the pulse. However, what you usually want is a specific pulse shape for your particular engineering design – for example, a constant power level for the duration of the shot. This is accomplished with a pulse forming network, which are inductors and capacitors connected in series (or certain kinds of transmission lines) to give the desired pulse profile.