Navy Lasers, Railgun, and Hypervelocity Projectile: Background and Issues for Congress [November 30, 2017] [open pdf - 2MB]
"The Navy is currently developing three potential new weapons that could improve the ability of its surface ships to defend themselves against enemy missiles--solid state lasers (SSLs), the electromagnetic railgun (EMRG), and the hypervelocity projectile (HVP). Any one of these new weapon technologies, if successfully developed and deployed, might be regarded as a 'game changer' for defending Navy surface ships against enemy missiles. [...] Although the Navy in recent years has made considerable progress in developing SSLs, EMRG, and HVP, a number of significant development challenges remain. Overcoming these challenges will likely require years of additional development work, and ultimate success in overcoming them is not guaranteed. The issue for Congress is whether to approve, reject, or modify the Navy's funding requests and proposed acquisition strategies for these three potential new weapons."
CRS Report for Congress, R44175
Federation of American Scientists: http://www.fas.org/sgp/crs/index.html