Navy Lasers, Railgun, and Gun-Launched Guided Projectile: Background and Issues for Congress [Updated October 20, 2021] [open pdf - 2MB]
From the Summary: "This report provides background information and issues for Congress on three potential new ship-based self-defense weapons for the Navy--solid state lasers (SSLs), the electromagnetic railgun (EMRG), and the gun-launched guided projectile (GLGP), also known as the hypervelocity projectile (HVP). The Navy's proposed FY2022 budget requests research and development funding for continued work on SSLs, but proposes suspending further work on the EMRG and GLGP programs and requests no research and development funding for them. The Navy installed its first prototype SSL capable of countering surface craft and unmanned aerial vehicles (UAVs) on a Navy ship in 2014. The Navy since then has been developing and installing additional SSL prototypes with improved capability for countering surface craft and UAVs. Higher-power SSLs being developed by the Navy are to have a capability for countering anti-ship cruise missiles (ASCMs)."
CRS Report for Congress, R44175
Congressional Research Service: https://crsreports.congress.gov/