A conductive projectile is fired from a two stage light gas gun into the railgun. The projectile slides between two parallel conductive rails and closes the electric circuit. An enormous current flowing in the circuit generates a magnetic field and Lorentz force accelerating the projectile. Cargo is subjected to extreme acceleration. Rail erosion is severe. The demand for electric power is astronomical. The cost of switches controlling the power is prohibitive. The minimum mass is 105 tons.
Direct physical contact between the projectile and the rails ablates both of them. The ablation produces plasma which short-circuits the rails and limits the maximum velocity to about 6 km/s. To reduce the ablation the railgun and its projectile are made of materials having low ionization potential. Filling the railgun with hydrogen gas also reduces the ablation.
S. C. Rashleigh and R. A. Marshall, "Electromagnetic acceleration of macroparticles to high velocities," Journal of Applied Physics, Vol. 49, No. 4, April 1978. pp. 2540-2542.
R. S. Hawke, A. L. Brooks, C. M. Fowler, and D. R. Peterson, "Electromagnetic Railgun Launchers," AIAA-81-0751, AIAA/JSASS/DGLR 15th International Electric Propulsion Conference, Las Vegas, Nevada, April 21-23, 1981.
Jerome Pearson, "Low-Cost Launch System and Orbital Fuel Depot," Acta Astronautica, Vol. 19, No. 4, 1989, pp. 315-320.
Derek A. Tidman, F. D. Witherspoon, and J. V. Parker, "A Gas-Insulated Railgun," IEEE Transactions on Plasma Science, Vol. 21, No. 6, December 1993, pp. 784-785.
January 1995 issue of IEEE Transactions on Magnetics is devoted to railguns.