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The US Navy is concerned about the survivability of Navy surface ships in potential combat situations against adversaries, such as China, that are armed with large numbers of missiles, including advanced models, and large numbers of UAV. In response, the Navy surface evolved a new organizing for the Navy’s surface fleet called distributed lethality. Under distributed lethality, offensive weapons such as anti-ship cruise missiles (ASCMs) are to be distributed across a wider array of Navy surface ships, and new operational concepts for Navy surface ship formations are to be implemented.
The aim of distributed lethality is to boost the surface fleet’s capability for attacking enemy ships and make it less possible for an enemy to cripple the U.S. fleet by concentrating its attacks on a few very high-value Navy surface ships (particularly the Navy’s aircraft carriers), according to Congressional Research Service Report.
“Although Navy surface ships have a number of means for defending themselves against anti-ship cruise missiles (ASCMs) and anti-ship ballistic missiles (ASBMs), some observers are concerned about the survivability of Navy surface ships in potential combat situations against adversaries, such as China, that are armed with advanced ASCMs and with ASBMs,” observes CRS report: Navy Lasers, Railgun, and Hypervelocity Projectile: Background and Issues for Congress.
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 antiship cruise missiles (ASCMs).
The Navy since 2005 has been developing EMRG, a cannon that uses electricity rather than chemical propellants (i.e., gunpowder charges) to fire a projectile. In EMRG, “magnetic fields created by high electrical currents accelerate a sliding metal conductor, or armature, between two rails to launch projectiles at [speeds of] 4,500 mph to 5,600 mph,” or roughly Mach 5.9 to Mach 7.4 at sea level.
Electromagnetic Rail Gun, EMRG , is a cannon that uses the thrust from magnetic force rather than chemical propellants (i.e., gunpowder charges) to launch projectiles at distances over 100 nautical miles – and at speeds exceeding Mach 5. In EMRG, “magnetic fields created by high electrical currents accelerate a sliding metal conductor, or armature, between two rails to launch projectiles at [speeds of] 4,500 mph to 5,600 mph,” or roughly Mach 5.9 to Mach 7.4 at sea level.
The speed of projectiles in conventional or light gas guns, both are limited by the acceleration of the expanding gas it uses. As EMRGs convert electrical energy into kinetic energy, effectively instantaneously, they are not limited by a maximum acceleration. Though EMRGs themselves tend to only be about 2% efficient, theoretically they have no limit to how much energy can be input to the system and thusly no maximum velocity the system can attain.
The railgun platform has advantages of large firepower input, large bomb storage and flexible combat use. Therefore, its military application potential is very large, and it has become an increasingly important part in the future weapon systems.
The Railguns provide revolutionary military capabilities. They provide Long range artillery (in excess of 200 Km) with increased penetration because of high impact speed and simultaneous impacts via rate of fire and velocity control. Railgun-equipped warships can fire hypersonic projectiles to shoot down stealth aircraft and ballistic missiles, or bombard enemy ships and land targets from hundreds of miles away. They can be employed for Anti-surface (naval), Anti air and anti missile defense (including against hypersonic threats).
The United States (Office of Naval Research, Naval Surface Warfare Center Dahlgren Division and BAE Systems), India (DRDO), the UK (DRA), Japan (ATLA), Russia as well as China all have electromagnetic railgun research projects at various stages of advancement. None so far has been fielded, but China appears to have conducted at sea tests of its prototype.
Railgun System
A railgun is a device that uses electromagnetic force to launch high velocity projectiles, by means of a sliding armature that is accelerated along a pair of conductive rails. A railgun consists of two parallel metal rails (hence the name).
The railgun mainly consists of one power source, two parallel long straight conductive rails, and a small mass armature which places between the rails as a conductive projectile, which completes the circuit. When the two rails are connected to the power supply, a strong current is injected from one rail and flow back from the other rail through the armature to generate a strong magnetic field, as shown in Fig.. Meanwhile, the armature is accelerated by Ampere’s force generated by electromagnetic fields
EMRGs are made up of a few subsystems: an electrical subsystem, an injector, a pair of supported conductive rails, and a projectile. The two industry-built prototypes are designed to fire projectiles at energy levels of 20 to 32 megajoules, which is enough to propel a projectile 50 to 100 nautical miles. (Such ranges might refer to using the EMRG for NSFS missions. Intercepts of missiles and UAVs might take place at much shorter ranges.)
1. Electrical Subsystem
The EMRG electrical subsystem is composed of three subsystems that output a pulse of current: a power source, a storage system; and a delivery system. The power source provides the storage system with electricity that is then stored. When the EMRG is fully charged and ready to fire the storage system sends the electricity as quickly as possible through a delivery system, a system of electrical cabling, and to the conductive rails.
2. Injector
The injector subsystem is required to accelerate the projectile before it reaches the electric rails. If the projectile enters the electric rails with no or a low initial velocity, the projectile will weld to the rails. To combat this, an injector system must be used to give the projectile an initial velocity. The more initial velocity obtained using the injector is also energy that the electric rails do not have to impart onto the projectile; ideally an injector that provides as much velocity as possible should be used.
3. Supported Conductive Rails
The conductive rails are the most important subsystem in the EMRG. They are the system responsible for converting electrical energy into kinetic energy using Lorentz force. Based on the size and distance between the rails the rate of conversion between electrical and kinetic energy is controlled. This conversion creates a large amount of force on the projectile but also on the rails themselves. To ensure that the rails do not fail due to the induced force, they are supported by a rigid structure.
4. Projectile
The projectile itself must be conductive. This allows the current to pass through the projectile and convert the electric energy into a force on the projectile. High melting points will maintain their shape better under firing conditions, but will also tend to do more damage to the barrel when they fragment.
Railgun Challenges and Technology requirements
There are three major problems in the development of electromagnetic railguns, namely erosion protection of rail, miniaturization of the energy storage system, and integrated guided projectile for continuous firing. Erosion protection of rail, as the first problem facing the engineering of electromagnetic railguns, is a bottleneck that must be solved in its application. The performance of the conductive rail material determines the lifetime of erosion protection. Many researches were focused on the design of advanced rail materials.
During the launching operation, the rails experience high electrical current density, large electromagnetic loads and huge mechanical and thermal shock. Under these extreme physical conditions, the forms of rail failure are accompanied by gouge, grooving, transition, and arc ablation, etc. These failures greatly reduce the service life of the rail and have become a bottleneck restricting the development of electromagnetic railgun technology.
Crucially, the weapon currently requires a 25-megawatt power plant of its own to fire at all. The vast power consumption can so far be supported by only three US destroyers being built. Another problem here is that the longer the distance to the target the weaker the impact of this shot as air resistance keeps slowing the projectile down as it travels to its target. Another major challenge is the guidance system, which is to be based on GPS, and the sensitive electronics that should be modernized to withstand the gravity in order not to crumble.
CHINA is loading its warships with monster generators that will power high-energy weapons strapped to the vessels, according to reports in July 2020. The 20 megawatt power units are required to operate lasers and rail guns that will destroy long-range targets and shoot down incoming missiles. The generators were completed in 2018 but loaded onto warships recently, according to the generators’ developers, as reported by the South China Morning Post (SCMP). “They will quadruple the power-generating capacity on the warships, making full electric propulsion possible,” the state media site said. “The generators will also be used for electromagnetic rail guns that can fire high-speed projectiles and laser weapons.”
US Navy found Railgunes, ‘not suitable for integration aboard a ship’ and were too big to fit the latest Zumwalt-class destroyers, Thomas Beutner, head of ONR’s Naval Air Warfare and Weapons Department, said during a July event in Washington, according to Defence One. To get around the issue, ONR researchers developed their own capacitors, which are far smaller, but can supply 20 megajoules per shot, with a goal of 32 megajoules by next year. According to ONR, ‘you can think of a megajoule as about the same, energy-wise, as a one-ton vehicle moving at 160 mph.’ These new capacitors ‘represent a new generation of pulse power, with an energy density of over a megajoule per cubic meter,’ said Beutner. The current version is now capable of firing multiple shots in succession, the group is also aiming to ramp the firing rate up to 10 shots per minute by 2018, the report said.
Developing an effective railgun presents a number of technical challenges that industry and the Defense Department have been working to overcome. “Years ago … the pulse power for this system was so large that the Army kind of lost interest because they couldn’t fit it on a typical Army vehicle, certainly not something that could maneuver with the force or be part of the mobile force,” Nick Bucci, vice president of General Atomics, missile defense and space systems said. Major progress has been made since then, he noted. General Atomics subsequently built much more efficient systems that have reduced the footprint by a factor of eight, he said.
Precision-guided projectiles is another critical technology area where a number of capabilities have to come together for the weapons to function effectively. The projectiles need components that enable the required amount of computing, sensing and maneuverability, Bucci noted. They must also be able to withstand the launch loads and the electromagnetic fields inside the launcher. Over the last three years, the company has demonstrated through testing that the technology is viable, he said.
Durability is another critical factor that has bedeviled railgun development. One of the challenge is that the high muzzle velocity quickly wears out their “barrels” (which are actually two conductive metal rods along which the projectile is driven), requiring frequent replacement. “You could get a few shots out of it, and in between the wear on the rails and the stresses on the barrels you were pretty much done after handfuls of shots,” Bucci said of older systems. But today’s prototypes could probably fire 1,000-plus rounds before wearing out, he said.
The medium-range prototype that the company has built has a range of more than 60 miles and is expected to fire about 20 rounds per minute. But as technology and materials improve that capability could be increased, he said. However, efforts to enhance railgun capabilities have implications for size, weight and power, an engineering challenge known as SWAP, he noted.
“Say I want either more velocity or I want more muzzle energy, which then means I need to grow the components of the system like the pulse power and power generation and things like that,” he explained. “The challenge … is how do I get more capability and still keep it in the box from a SWAP perspective for Army vehicles.”
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…. 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.
New capacitors, more resistant materials and better pulse power storage systems could all contribute to making the railgun more efficient. Computer-aided design, 3D printing techniques and better dielectric materials—materials that don’t conduct electricity but can store energy in the form of an electrostatic field—could all lead to making the EM railgun viable.
The Office of Naval Research recently identified several key “research opportunities” to make the railgun a success, including better thermal management for the gun’s launch rails; extending the service life of the equipment; developing high-strength dielectric structural materials; and reducing the size of associated power systems and control electronics. Experts say that the limited durability of a railgun’s rails under the stress of repeated firing is an especially serious challenge for the technology – one that rapid-fire testing may help address.
While the weapon is currently configured to guide the projectile against fixed or static targets using GPS technology, it is possible that in the future the rail gun could be configured to destroy moving targets as well, Capt. Mike Ziv, Program Manager for Directed Energy and Electric Weapon Systems said.
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.
Rep-rate adds new levels of complexity to all of the railgun sub-systems, including thermal management, autoloader, and energy storage. A new test facility capable of supporting rep-rate testing at full energy level is coming on line at the Terminal Range at the Naval Surface Warfare Center, Dahlgren, Virginia. A new demonstration launcher (DL1) has been delivered and installed at the Terminal Range to commission the new facility. Additional rep-rate composite launchers (RCLs) capable of rep-rate are in various stages of design and fabrication
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.
Remaining development challenges for EMRG involve items relating to the gun itself (including increasing barrel life to desired levels), the projectile, the weapon’s electrical power system, and the weapon’s integration with the ship
Following tests with early Navy-built EMRG prototypes, the US Navy funded the development of two industry-built EMRG prototype demonstrators, one by BAE Systems and the other by General Atomics.
Industry-Built EMRG Prototype Demonstrator General Atomics prototype
Requirements of the rail materials
The rail environment consists of large electrical currents, high local temperatures, large electromagnetic loads, and high sliding velocities. When choosing rail material, two objectives for railgun must be met. One is maximizing magnetic efficiency, and the other is maximizing durability. The magnetic efficiency can be maximized by minimizing the electrical resistivity, and the rail durability is dependent on different forms of rail failure. Based on the analysis and failure mechanism, Researchers have obtained the performance requirements for the rail material: high electrical conductivity, high hardness, high thermal conductivity and high resistance to abrasion and arc ablation.
During the research of electromagnetic guns for more than 50 years, many researchers have tried single materials and composite materials as electromagnetic launch rail. A series of research progresses are obtained to deepen the learning of the service characteristics of electromagnetic launch rail. The conducting rails of most electromagnetic launchers have historically been copper-based, such as electrolytic tough pitch copper and oxygen-free high conductivity copper which are relatively pure metals.
Pure copper is rather soft with coarse grains and many methods are adopted to refine the grain to strengthen pure copper. High-pressure torsion and nano-twinning are two effective strengthening manners. Considering there is large thermal shocking during electromagnetic emission, the relative low softening temperature is another bottleneck for the application of pure copper. Improved performance has been sought through alloys such as Cu-Cr, Cu-Cr-Zr, Cu–Mo, Cu–W with an alloying method, Cu/Al2O3 with a composite method and application of appropriate coatings on the copper
Raytheon delivers pulse power containers for US Navy’s railgun programme
Raytheon has started delivering pulse power containers (PPCs) to support the US Navy’s railgun programme. In January 2012, the US Naval Sea Systems Command awarded an initial $10m contract to Raytheon for the preliminary design of a large power system, Pulse Forming Network (PFN).
‘Pulse Power Containers’ (PPC) consist of huge banks of capacitors or rechargeable batteries packed inside standard ISO containers. Developed by Raytheon, each container packs enough energy to discharge 18 kilowatts for each shot. To enable the railgun to fire ten such shots per minute the PPC must recharge from the host ship in seconds and be able to store and discharge the energy in very short time while managing the thermal load generated by the process.
The PFN will provide the electromagnetic energy for the railgun projectile to travel without the use of an explosive charge or rocket motor. The containers will be included in the navy’s railgun test range for additional development and testing. According to Raytheon, these PPCs, when combined, produce enough power to trigger an electromagnetic launch of a railgun’s high-velocity projectile, at speeds of more than mach 6.
Raytheon Integrated Defense Systems Business Advanced Technology vice-president Colin Whelan said: “Directed energy has the potential to redefine military technology beyond missiles and our pulse power modules and containers will provide the tremendous amount of energy required to power applications like the navy railgun. The US Navy’s railgun uses an electromagnetic force, known as the ‘Lorenz Force’, to fire a projectile at six or seven times the speed of sound.
The Navy, in addition to developing the railgun itself, is working on a hypervelocity projectile (HVP) that will support both the railgun and conventional 5-inch guns. The GPS-guided round will fly at hypersonic speeds, but the Navy is still working with the Pentagon’s Strategic Capabilities Office to close the fire control loop between the gun and the projectile.
EDA Launches ‘PILUM’ Research Study On Electromagnetic Railguns
The European Defense Agency (EDA) and the French-German Research Institute of Saint-Louis (ISL) launched in May 2020, a research study on electromagnetic railguns in which 5 European countries are taking part. The study has been dubbed ‘PILUM’.
Electromagnetic railguns are launchers using very high electrical energy by using the Lorentz force to obtain significantly higher initial velocities than those of chemical guns. The EDA-PADR PILUM Project will cover a period of two years in order to show the feasibility to construct such an electromagnetic railgun for artillery applications which can reach standoff distances up to 200 km. A possible integration into ships and other military platforms shall also be investigated. Experimental, simulation and modelling work will be part of the studies to proof the feasibility for the use of theses railguns. These studies shall be the basis for the definite construction of a Demonstrator within a 8 years term.
PILUM Projectiles for Increased Long-range effects Using Electro-Magnetic railgun: Considering trends for enhanced precision and range of ammunition while seeking affordable costs, the electromagnetic railgun (EMRG) is a disruptive technology to launch projectiles over extremely long distance (more than 200 km) and a potential operational game-changer, thanks to electromagnetic acceleration instead of chemical propellants. The project lays the foundation for achieving a full-scale demonstrator by 2028.
Existing railguns by ISL: PEGASUS and RAFIRA
he French-German Research Institute (ISL) has several railguns installed, the largest of these is the PEGASUS accelerator. It is a 6m long, 4×4 cm2 caliber distributed energy supply (DES) railgun. It was was built in 1997 at ISL facility in Eastern France, close to the German border. ISL picture.
ISL’s railgun facilities are unique in Europe and already features several railgun systems including:
The 10 MJ installation PEGASUS which is being used to advance the launcher and armature technology towards a reliable half-scale long range artillery system. Recent results include the successful launch of in-house developed launch packages (mass range is kg) for hypervelocity (> 2500 m/s) projectile acceleration. The ISL launch technology sets worldwide accepted standards with regard to the efficiency of the conversion of electric energy into kinetic energy (> 35%).
RAFIRA is a railgun (25 mm2 caliber) with which a salvo up to five shots can be launched at extremely high fire rates. In single shot mode, RAFIRA can accelerate projectiles in the mass range of 100 grams to velocities of more than 2400 m/s corresponding to acceleration levels of more than 100 000 g. This launcher is used to investigate the potential use of railgun technology for anti-ship missile scenarios. Operational research analysis has led to the conclusion that fire rates of over 50 Hz are necessary to defend against hypersonic Missiles.
Russia continues R&D work on electromagnetic railgun
Laboratory head of the Shatura affiliate of the institute Vladimir Polishchuk told the newspaper that engineers succeeded to design and build a new capacitive storage. It can accelerate objects weighing 100 gram to a speed over 3 km/s. “In two years the power loading in Shatura increased six-fold – from 0.8 megajoule to 4.8,” Polishchuk said.
Experiments with a railgun powered by pulsed inductive energy storage have been prepared. “Such an electric power scheme provides rapid energy introduction into plasma which increases the temperature of the plasma piston and consequently the speed,” he said.
The Shatura affiliate uses plasma electromagnetic guns which it believes are the most promising ones. The accelerated object moves between two parallel electrodes or rails with electric current. The current goes in plasma which pushes the projectile. “The systems with hard, not plasma strap considerably reduce acceleration at a speed of 1.5-2 km/s. Record speeds for railguns of the type do not exceed 3 km/s. At maximum speed the fire rate of the accelerator comprises from one to three shots,” Polishchuk said.
Plasma piston with a 1kg striker accelerates the projectile to 6 km/s. It is believed plasma electromagnetic rail guns can produce a speed of 10-12 km/s. However, so far it is limited by available technologies to produce the channel, which has to sustain immense heat and dynamic loads. “Speeds over 7 km/s provide opportunities to study the substance at extreme parameters and obtain new materials,” Polishchuk said.
Expert Andrey Leonkov said the United States is actively studying the possibility to use railgun in combat, but the design is focused mostly on non-plasma electromagnetic guns. “The United States already uses accelerators with a hard, not plasma strap as a catapult to launch aircraft from the carrier. An electromagnetic gun has been recently tested to provide a speed of 2.5 km/s for a projectile of 10-20 kg,” he said.
Research of plasma has a smaller scope in the USA. Still there were reports that a railgun fired a plasma bunch at a speed of 100 km/s. If all technical issues are successfully resolved, such plasma objects will be able to destroy radio-electronic satellite systems, Leonkov said.
The railguns are expected to become electromagnetic artillery of the future. Installed on warships they can fire at targets at a distance of 300-400 km and even destroy objects in the near-Earth orbit, the Izvestia reported.
