The following is the Oct. 15, 2020, Congressional Research Service report, Navy Lasers, Railgun, and Gun-Launched Guided Projectile: Background and Issues for Congress.
From the report
Three new ship-based weapons being developed by the Navy—solid state lasers (SSLs), the electromagnetic railgun (EMRG), and the gun-launched guided projectile (GLGP), also known as the hypervelocity projectile (HVP)—could substantially improve the ability of Navy surface ships to defend themselves against surface craft, unmanned aerial vehicles (UAVs), and eventually anti-ship cruise missiles (ASCMs).
The Navy has been developing SSLs for several years, and in 2014 installed on a Navy ship its first prototype SSL capable of countering surface craft and UAVs. 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 ASCMs. Current Navy efforts to develop SSLs include
the Solid State Laser Technology Maturation (SSL-TM) effort;
the Optical Dazzling Interdictor, Navy (ODIN);
the Surface Navy Laser Weapon System (SNLWS) Increment 1, also known as the high-energy laser with integrated optical dazzler and surveillance (HELIOS); and
the High Energy Laser Counter-ASCM Program (HELCAP).
The first three efforts above are included in what the Navy calls the Navy Laser Family of Systems (NFLoS) effort. NFLOS and HELCAP, along with technologies developed by other parts of DOD, are to support the development of future, more capable shipboard lasers.
The Navy has been developing EMRG for several years. It was originally conceived as a naval surface fire support (NSFS) weapon for supporting Marines and other friendly forces ashore. Subsequently, it was determined that EMRG could also be used for air and missile defense, which strengthened Navy interest in EMRG development. The Navy is continuing development work on EMRG, but it is unclear when production-model EMRGs will be installed on Navy ships. The Navy’s FY2021 budget submission requests $9.5 million in FY2021 for continued development of EMRG, but does not appear to program any additional development funding for EMRG in FY2022-FY2025.
As the Navy was developing EMRG, it realized that the guided projectile being developed for EMRG could also be fired from powder guns, including 5-inch guns on Navy cruisers and destroyers and 155 mm artillery guns operated by the Army and Marine Corps. The concept of firing the projectile from powder guns is referred to as GLGP and HVP. One potential advantage of HVP/GLGP is that, once developed, it can be rapidly deployed on Navy cruisers and destroyers and in Army and Marine Corps artillery units, because the powder guns in question already exist.
In addition to the question of whether to approve, reject, or modify the Navy’s FY2021 funding requests for SSLs, EMRG, and HVP/GLGP, issues for Congress include the following:
whether the Navy is moving too quickly, too slowly, or at about the right speed in its efforts to develop these weapons;
the Navy’s plans for transitioning these weapons from development to procurement and fielding of production models aboard Navy ships; and
whether Navy the Navy’s shipbuilding plans include ships with appropriate amounts of space, weight, electrical power, and cooling capacity to accommodate these weapons.