
Plasma Rifle- Firing System
The weapon is essentially a railgun that accelerates plasma at extremely high velocities, to send the projectiles out to long ranges, and act like a firearm. The weapon's challenges include finding low weight, energy efficient batteries, capacitors, and electrical energy storage devices, to compensate for the drastically increased power consumption of the weapon, efficient magnetic rails, and a suitable projectile to be utilized in the weapon. While fundamentally predicated on the use of a railgun to accelerate the projectile, the weapon hopes to save on the weight of the projectiles, and thus the required energy to bring them up to velocity, by using substantially lighter plasma projectiles, which are created from either xenon or hydrogen. The propellant is stored as a gas, and then converted to plasma before it is to be accelerated, via microwave stimulation and a low pressure chamber, similiar in operation to how plasma globes work. These projectiles compensate for their low energy by being extremely hot and unstable, and thus eat their way through a target with it's high temperature before rapidly expanding. This requires less energy in regards to railgun acceleration, and more in regards to heating up the projectile. The plasma projectiles naturally paramagnetic behavior makes it ideal for being accelerated by a railgun, and xenon propellants have been used successfully in Ion thrusters in similiar manners, most notably for use in satellites, such as with the Dawn spacecraft making it up to 10 km/s, or the fastest known man made object in existence. As plasma is technically a state of matter, a plasma rifle could in theory technically accelerate any mass that was heated to the plasma state, although picking materials which are easily turned into plasma is crucial. If accelerated at high enough velocities, the theory is that plasma will stay whole, rather than dissipating in the atmosphere quickly, due to the compression of the outside air, via air resistance. Hyper velocity and it's additional effects are also aspects of the design. In particular, hypervelocity is velocity so high that the strength of materials upon impact is very small compared to inertial stresses. Thus, even metals behave like fluids under hypervelocity impact. Extreme hypervelocity results in vaporization of the impactor and target. For structural metals, hypervelocity is generally considered to be over 2,500 m/s (5,600 mph, 9,000 km/h, 8,200 ft/s, or Mach 7.3). Meteorite craters are also examples of hypervelocity impacts. It's safe to assume based on the expense of the fuels, batteries, fuel cells, and materials used in their production, that a plasma rifle would require several 10's of thousands of dollars to produce.
A Railgun is an electrically powered electromagnetic projectile launcher based on similar principles to the homopolar motor. A railgun comprises a pair of parallel conducting rails, along which a sliding armature is accelerated by the electromagnetic effects of a current that flows down one rail, into the armature and then back along the other rail. Railguns are being researched as a weapon with a projectile that would use neither explosives nor propellant, but rather rely on electromagnetic forces to achieve a very high kinetic energy. While current kinetic energy penetrators such as an armour-piercing fin-stabilized discarding-sabot can achieve a muzzle velocity on the order of Mach 5, railguns can potentially exceed Mach 10, and thus far exceed conventionally delivered munitions in range and destructive force, with the absence of explosives to store and handle as an additional advantage. Railguns have long existed as experimental technology but the mass, size and cost of the required power supplies have prevented railguns from becoming practical military weapons. However, in recent years, significant efforts have been made towards their development as feasible military technology. For example, in the late 2000s, the U.S. Navy tested a railgun that accelerates a 3.2 kg (7 pound) projectile to hypersonic velocities of approximately 2.4 kilometres per second (8,600 km/h), about Mach 7. They gave the project the Latin motto "Velocitas Eradico", Latin for "I, [who am] speed, eradicate" (in the vernacular usage, "Speed Kills".) While the railgun does not achieve the highest velocity possible with modern railguns, it does achieve the 2.4 km/s energy level, which makes it's level of energy exceed what is possible from chemical explosives, making the solid kinetic energy penetrator possess more energy, kilogram per kilogram, at those velocities, than most high explosives, such as TNT. Unlike conventional cannons, railguns do not make use of explosives to deliver high energy projectiles to the target, such as C-4, or TNT, and instead rely on the heavy mass and high velocity of the targets to deliver their energy. TNT possesses approximately 4.18 megajoules of energy per kilogram, while the railgun possesses 5.76 megajoules at a velocity of 2400 m/s.
Somewhat quixotically, railgun efficiency and power is more dependent on the batteries than the weight of the projectiles themselves. While Xenon propellant technically is what comes into contact with the target, the electrical storage efficiency for the weapon is generally the most difficult aspect of the weapon to achieve, in term's of weight. Initial considerations for calculations include the efficiency of the railgun itself; ven high quality railguns only possesses approximately 40% efficiency, which will increase the weight of any storage system by roughly 2.5 times the amount, as a result. Railguns make extensive use of electrical energy, and due to the fact that electric energy storage is generally less efficient in terms of overall mass, or possesses lower energy densities than, hydrocarbons or other contemporary fuels, the difficulty will be in finding an appropriate power system for the weapon. (Page 9) Lithium ion battery's possess .36 Mj to .95 Mj megajoules of energy per kilogram. Lithium ion capacitor's possesses .05 megajoules. Lithium titanate batteries can be recharged significantly faster than lithium ion, but possess approximately the same amount of energy per kilogram. The discharge/charge rate is approximately 90-95% for both, which implies an approximate loss of 10% efficiency for the conversion efficiency. This automatically implies a 36% efficiency, or a need for 2.8 times the energy than will end up at the muzzle. With an energy density of .05 megajoules per kilogram, and a requirement of 50 joules per shot, to accelerate a .01 gram projectile to 3,175 m/s, or 140 joules per shot, the weapon can store approximately enough energy for 360 rounds per kilogram of material; with the additional lithium titanate battery and the container, this equates to approximately a 2.5 pound battery for the weapon to fire 360 rounds. For a .1 gram projectile, this would be 36 rounds; for a 1 gram projectile, a practical size, this would be approximately 3.6 rounds.
To provide substantially more energy, a fuel cell of some kind can be utilized. With a conversion efficiency of 60%, it's possible for a kilogram of hydrogen converted to electricity in a hydrogen fuel cell to produce 85.2 megajoules of energy, which is substantially more than lithium ion, or a lithium ion capacitor; in fact, it is roughly 1700 times more than a lithium ion capacitor, and 90 times more than the best lithium ion batteries on the market. While capacitor's are still necessary for the temporary storage of power in the weapon, and thus transfer to the weapon's rails, it is still possible to store significantly more energy in terms of weight than with lithium ion capacitor's alone. There is also the added weight of the fuel cell, itself, which more or less operates similarly to an engine in a car. Luckily, even efficient hydrogen fuel cell's are quite small, and are often stacked to form larger collective unit's, which makes them easier to miniaturize for more portable applications. Because this generates some latency however, transferring the energy of the fuel cell to the battery or capacitor can take time, and thus how much energy is present in the hydrogen does not ultimately determine how much energy can be used in a reasonable amount of time. The larger amount of fuel cells that are "stacked", the higher the charge rate usually is. An example unit could be 1.3 kilograms for 100 watts [1], all the way up to 20 for 1000 [2]. Ideally, you would utilize something such as the Aerostak 1000, which can produce 1000 watts, per second at roughly 2.3 kilograms. With ultralight versions, it's not impossible for the fuel cell to only make up approximately 3/4 to half the weight of the system, or, only double or quadruple the weight requirements for fuel. These more efficient systems often require substantially higher hydrogen purity levels, and are also substantially more expensive. Still, it is not impossible for a stand alone, hand held weapon to practically hold on to large volumes of projectiles; this would be roughly close to 6,000 rounds per detachable 3.3 kilogram magazine, at 7.5 pounds, or if the fuel cell was stored internally, 2.2 pounds if the hydrogen was stored itself. However, the weight of the pressurized container for storage could still add considerable weight. A more practical size would be the Ultralight PEM Fuel Cell, at 1.1 pounds, only producing 200 watts, per second. While substantially smaller, it would require 62.5 seconds to recharge the capacitor's per shot, compared to 12.5 seconds with the Aerostak. It would possess a larger volume of fire, in terms of overall weight, but a lower rate of fire, dependent almost entirely on the size of the capacitor's.
Methanol on the other hand, is much easier to store. Methanol fuel cells however, are substantially less efficient. At approximately 25% efficiency, and with only 19.7 megajoules of energy per kilogram, they had a much wider operating temperature, store as a liquid at room temperature, and is substantially cheaper to create, ship and obtain, but are overall much less efficient. It is still greater than most lithium ion batteries and capacitors, however. Reformed Methanol cells can provide greater efficiency, up to 40% or higher, however they come at higher expenses and an increase in required heat management.
For practical purposes, the power source is best stored on the unit's back, such as in a backpack. For recharge time's, it's overall substantially more efficient if you stack all the fuel cell's, rather than reload the weapon individually with separate magazine's. Thus, stacking all the fuel cell's together is generally considered superior than having several smaller one's to load into the weapon, such as with standard magazines. It also makes the equipment cheaper and easier to handle. Rather than putting this on the weapon, which would increase it's weight by the weight of the fuel cell, or for practical considerations some 30-40 pounds, it is generally better to carry this separate from the weapon, say in a backpack, or spread out over the body in the form of a tactical vest, where magazines would ordinarily go. On top of this, a pressurized container would be required, similiar to that of a scuba tank, which itself is often close to 33 pounds fully aired up. Using a carbon fiber scuba tank, the weight of the system alone can be reduced to some 6 pounds, or 8 pounds loaded.
Actual weight of the system
To determine the weight of the system, we must first determine the weight of three, key factors. First, how heavy is the storage system for our fuel and propellant, second how heavy are the batteries and capacitor's, and third, how much fuel are we storing in the device. If we decided to use a backpack, this can be substantially higher than just a single magazine, however it will require a wire and/or siphon to the backpack for it's power. In comparison, a 30 round STANAG magazine for the M16 or other 5.56mm weapon's is approximately 1 pound, a 20 round 7.62mm x 51mm NATO magazine is 1.3 pounds, and a 500 round box is around 15-17 pounds, with links included. This is closer to 30-34 pounds with 7.62mm x 51mm NATO ammunition. To reach practical levels of carry and transport, these would need to be limits that were achieved. 2.5 to 5.5 pounds per magazine is still relatively practical, given the size of some drum magazines or belt fed links.
Hydrogen gas weight is determined by a number of factors, but initially it is important to examine the container amount. Compressed hydrogen (CH2, CGH2 or CGH2) is the gaseous state of the element hydrogen kept under pressure. Compressed hydrogen in hydrogen tanks at 350 bar (5,000 psi) and 700 bar (10,000 psi) is used for mobile hydrogen storage in hydrogen vehicles. 700 bars is practical using an aluminum carbon fiber composite tank. At 700 bars, 19.75 liters of hydrogen can equal approximately 1 kilogram, or 2.2 pounds of fuel. This can be stored in a roughly 6 pounds carbon aluminum hybrid fiber tank, or for approximately 8.5 pounds. Another fuel type, methanol, is also available. Much easier to store, but with a lower energy density and efficiency, a 50% efficient fuel cell is not particularly unreasonable. The X-55, a military approved methanol fuel cell, is approximately 6.6 pounds, and 1.4 pounds of fuel and their canisters can generate approximately 440 watt/hours, or 1.58 megajoules of energy. It only produces 50 watts, however.
The weapon Itself
With railgun's, more efficiency and power can be achieved by making the weapon longer. To achieve the greatest length possible, the rail's of the railgun themselves extend almost entirely to the back of the weapon, with a few inches of clearance, to give the weapon' the longest barrel to overall-length ratio possible. A 40 inch weapon for instance would possess approximately a 38 inch barrel. A few more inches, to allow the plasma to be directed behind the barrel, are necessary to load and charge the weapon beforehand. A computer is required to accurately guage and calculate the weapon's required energy output, as well as a trigger and other human interfaces devices to start the chain reaction. First, the propellant is siphoned off from it's container and placed into the "plasma globe", to be converted into plasma. The higher chamber combined with the electrical and microwave stimulation (generated by a magnetron) causes the The chamber itself is surrounded with a faraday cage, to prevent the microwaves from leaking into the surrounding environment. This takes a moment of charging, as the plasma takes some conversion time; usually, a small amount, say, 30 rounds, are stored in the plasma chamber at any given time, to provide a reserve to reduce necessary charging time, but during the process the plasma ball will need to be routinely charged. After in a sufficient plasma state, the projectiles will be injected into the railgun at 100 m/s using air pressure (from a substantially smaller, air gun), to give the projectile a higher starting velocity. The rate of acceleration of the railgun will be incredibly fast, so fast that the temporary amount of time that the plasma stays in contact with the barrel will be too insignificant for the heat transfer to cool down the plasma, or heat up the barrel. While railgun RPM's are inherently dependent upon heating and cooling, the smaller mass of the plasma cartridges and their short time spent in the barrel should reduce this requirement somewhat, or be roughly equal to it. The amount of friction usually generated by solid projectiles is far greater than the energy imparted by the plasma to the barrel.