Rail guns are devices that convert electric energy into linear kinetic energy. Their potential applications include mass drivers for use in outer-space mining, or new military weapons systems. Currently they use solid metal rails that the projectile slides along as it is being accelerated. However because of the large (often hundreds of amperes) amount of electrical current involved, there is arcing between the rails and the projectile as well as high-temperature plasma discharges that severely reduce the lifespan of the rails (sometimes to the point where they must be replaced after every shot).

This new design uses rails that are generated -literally- from thin air. You may have seen videos or read articles about LIPC (Laser-Induced Plasma Channel) technology that is being developed by several companies. Using an ultraviolet laser tuned to the frequency of nitrogen, one can excite the particles in the air to such an intensity that they become a plasma. Since plasmas are electrically conductive, this effect coupled with a high-voltage discharge is being tried as an alternative to tasers and even as a sort of shocking "force field". However it is possible that these plasma channels could be used to transmit the high-amperage current necessary for a railgun. A projectile would be injected by an air gun into the beams from two LIPC lasers, completing the circuit and allowing the Lorentz force to accelerate it. Because of the nature of the Lorentz force (it would also push the plasma channels themselves outwards and thus dissipate them), the lasers and the high-current discharge would have to be pulsed at a relatively high frequency. Pulsed lasers however are cheaper than continuous-wave lasers for a given power, and thus this is actually advantageous. Special high-frequency capacitors will have to be used which, along with the lasers, will constitute the bulk of the price for this project. The performance of the railgun will be limited only by the size of the capacitor banks, the effective range of the lasers, and the ballistic trajectory of the object being fired (once it falls below the laser beams, the circuit will no longer be complete and no further acceleration can take place - this is one reason why it is essential for there to be a gas-injection system to pre-accelerate the projectile).

I believe that this could be a revolutionary step in railgun technology, and might finally bring it out from the laboratory into the field. Some might find it distasteful that this seems to be a purely violent weapon-type project, but just as gunpowder eventually led to the internal combustion engine and beyond, this invention could lead to uses and technologies that we have not yet even thought of.