The U.S. Office of Naval Research (ONR) is proceeding in its electromagnetic raingun research and expects to reach a capacity of 10 rounds per minute with a 32 Mega-Joule muzzle launch for each round, officials said Thursday.
Dr. Thomas Beutner, department head of Code 35 in ONR’s Naval Air Warfare and Weapons Department, told reporters that the railgun research is going well and has made several scientific advances.
The railgun uses stored electricity in a pulsed power system. Then an electric pulse is sent to the railgun, which creates an electromagnetic force that accelerates a projectile to 4,500 miles per hour, or Mach 6. The projectile can then destroy a target using kinetic energy alone.
Beutner highlighted the benefit of using a railgun that eliminates the danger of a ships carrying gunpowder in ordnance because then can explode and damage or sink a ship in wartime or accidents.
The railgun program, called the Electromagnetic Railgun Innovative Naval Prototype (INP), began in 2005. Phase 1 successfully produced a 32 MegaJoule muzzle energy proof-of-concept demonstration. The railgun overall seeks to launch a projectile up to 100 nautical miles (nm). Phase 2, which ONR is still competing, began in 2012 and concentrates on demonstrating a 10-rounds-per-minute firing rate.
Tom Boucher, program officer at Code 35 said the ONR S&T program calls for a maturation of achieving 10 rounds per minute at 32 megajoules by fiscal year 2019. To reach that goal, ONR is building a series of barrels and incorporating lessons learned. They will achieve the full rep-rate and muzzle energy in 2018 and in 2019 demonstrate the longest life of a barrel at that muzzle energy.
After reaching these goals the S&T portion of the program should be complete. Separately the Navy’s Program Executive Office Integrated Warfare Systems (PEO IWS) will look at shipboard integration if the Navy decides to do that and that office will make any follow-on acquisition decisions, Boucher said.
Beutner said the railgun as tested currently has a range of 110 nm.
However, weapons like the railgun as well as high-power RF and high-energy lasers “pose unique demands on the power system.”
He said another ONR department, Code 33, has responsibility for researching ship power systems and has begun looking at what a ship’s power needs are for the railgun, other electricity-demanding weapons, radar systems, and regular ship demands combined.
ONR is looking in to having battery banks to charge the capacitors the railgun uses and the battery banks could be charged by the regular ship power. Those batteries could also be used by more than one weapon system to help alleviate the loads.
In the meantime, ONR’s approach for testing railguns has been a “federated approach” where they bring a separate power generation system with the railgun. The same thing was done when a high-energy laser was tested on the USS Ponce recently.
Beutner admitted that is the simplest way to conduct the tests, but is clearly not the best choice in the long term.
“And so the power generation and storage and power approaches are all part of what we’re researching as well.”
ONR has looked into modularity in capacitors, using three separate suppliers in tests. They currently work in large rectangular boxes, but the office sees an opportunity for more form-fitting containers for capacitors. These would more naturally fit into spaces in ships.
Beutner admitted this kind of electric weapon system has a cooling requirement, both for railguns barrel and the capacitors. However, he said ships can more easily alleviate this by using the ocean and feeding cooler water into a tank system.
ONR’s rep-rate composite launcher, which can repeat launches quicker than other test devices, will be able to achieve the 10 round-per-minute rate the program seeks by later this summer. ONR plans to gradually ramp up this launcher to higher rep-rate and energy levels through the end of the year, Beutner said.
He also talked about how ONR has demonstrated the ability to use pulse power, having fired 5,000 pulse shots. For the rep-rate firing, ONR has to use a larger energy farm or capacitor base resulting in pulse power using over one megajoule per cubic meter energy density.
“That’s an important scientific advance in terms of energy density in those capacitors, but even more important that’s a size factor that will fit into the ships. Both crewed combatants and future combatants," Beutner said.
Beutner also noted ONR is also making “significant advancements” on the hypervelocity projectile (HVP). The HPV is ramping up in a series of demonstration in the coming years and will be compatible with both the railgun and conventional guns. The HPV shares the same outer hull line and overall projectile with separate outer casings to fit it into railguns, 5 inch guns, and 155 mm guns.
ONR decided on 32 megajoules and 10 rounds-per-minute rep-rate as a balance between capability and technology. He said certain “sweet spots” drove these determinations, including the physical limits of any hypervelocity projectile.
Beutner said ONR does not see the railgun as a replacement for other technology and system, but an addition as part of a ship’s layered defense.