Hackaday

Railguns use the Lorentz force — the same principle behind homopolar motors — to accelerate a conductive armature along two parallel rails using massive electrical currents, achieving projectile velocities of 2–3 km/s. Despite decades of R&D by the US, China, India, and Japan, widespread deployment remains elusive due to severe rail degradation: arcing, ablation, grooving, and thermal wear destroy the rails after only a few shots. Research into copper alloys (Cu-Cr, Cu-Cr-Zr) and coatings (molybdenum, tungsten) via electroplating, cold spraying, and laser cladding has yet to solve the durability problem. Japan's Ministry of Defense appears closest to a viable design, but only for a narrow defensive niche: a small-caliber (40 mm) close-in weapon system for intercepting hypersonic and ballistic missiles, where limited range and low firing rates are acceptable tradeoffs.

Railguns: Making Metal Go Fast Using The Lorentz Force