Railgun – Weapon of the Future

The Railgun made its public debut during the Navy’s Future Force Science and Technology Expo held at the Washington Convention Center in February 2015. One senior navy official explained the impact of the projectile to “a freight train going through the wall at a hundred miles an hour.”

Issue: 4 / 2016By Lt General Naresh Chand (Retd)Photo(s): By US Navy
A prototype of BAE Systems’ electromagnetic Railgun on display aboard joint high speed vessel USS Millinocket

The EM Railgun uses high-power EM energy instead of explosive chemical propellants to fire a projectile farther and faster than any current gun. When fully weaponised, a Railgun will deliver hypervelocity projectiles on targets, at ranges far exceeding any of the current naval guns. It will be able to effectively intercept air threats, particularly anti-ship cruise missiles. Railguns also offer much larger ammunition holding capacity and lower cost per engagement as compared to missiles of similar range. They can also be employed to support land operations. In addition to military applications, the US National Aeronautics and Space Administration (NASA) has proposed to use a Railgun from a high-altitude aircraft to fire a small payload into orbit; however, the extreme g-forces involved would necessarily restrict the usage to only the sturdiest of payloads. The efficacy will only be seen when the Railgun is fully weaponised.

How it Works

Basically a Railgun is an electrically powered electromagnetic projectile launcher based on similar principle as the homopolar motor. The first homopolar motor was demonstrated by Michael Faraday during 1821 in which he used direct current to cause rotational movement. To understand the principle behind a Railgun, take a magnetic compass and place an electric wire in North-South direction over the compass. When you connect the wire to a battery, the needle will move a little. The length of the movement will depend upon how much current is flowing through the wire. This simple experiment demonstrates that electric current creates a magnetic field which interacts with the needle and makes it move. The force created is at right angles to both direction of the current and the direction of the magnetic field. This simple idea has been translated to develop a Railgun. The building blocks of a Railgun are a pair of parallel conducting rails (one acts as positive and the other as negative conductor) and a sliding armature. When current flows through the positive rail, it creates an electromagnetic field due to which the sliding armature accelerates and the current passes through it, the current then returns to the power supply through the negative rail. The projectile experiences a force which is called Lorentz force (after the Dutch physicist Hendrik A. Lorentz). The Lorentz force is directed perpendicularly to the magnetic field and to the direction of the current flowing across the armature. This phenomenon is being researched and developed to produce a super gun which does not use a propellant or explosive but a very high degree of kinetic energy. The power of the energy will depend on the length of the rail or intense current but as long length of the rails pose problems of space; thus to have an effective Railgun, a very high level of current is required. Most Railguns thus use a strong current to the degree of a million amps for generating the required force. When this force is applied to a projectile, it accelerates to the end of the rails, opposite to the direction of the power supply and leaves through an aperture. At this point the circuit is broken which ends the flow of current. Antitank projectiles like armour-piercing finstabilised discarding-sabot can achieve a muzzle velocity (MV) of about Mach 5 but Rail guns can achieve a MV of Mach 7-10. Such a high degree of MV makes projectiles fired from a Railgun more penetrating against hard targets and achieve a much longer range of about 160 km.

Development

The US Navy is vigorously pursuing the development of Railgun for air defence role. During March 2006, BAE Systems received a contract for design and production of the 32 megajoules (MJ) Laboratory Launcher for the US Navy. During February 2012, as part of Phase 1 of the Navy’s Innovative Naval Prototype (INP) programme, engineers at the Naval Surface Warfare Center successfully fired BAE Systems’ EM Railgun prototype at tactical energy levels. The gun fired a 32 MJ half-power prototype (the Navy compares one MJ of energy to a onetonne vehicle moving at about 160 kmph. The full-scale system is expected to be 64 MJ. Chris Hughes, the then Vice President and General Manager of Weapon Systems at BAE Systems stated that, “We’re committed to developing this innovative and game changing technology that will revolutionize naval warfare. The Railgun’s ability to defend against enemy threats from distances greater than ever before improves the capabilities of our armed forces.”

GA-EMS is on the forefront of maturing Railgun weapons systems to support air and missile defence, counter battery fire, and precision indirect fire

BAE Systems was again awarded a $34.5-million contract by the Office of Naval Research (ONR) for the development of the Railgun under Phase 2 of the Navy’s INP programme. The aim of the Phase 2 was to mature the technology and design of the launcher and pulsed power from a single-shot to multi-shot capability. This would also involve developing and incorporating a auto-loading and thermal management systems. Faster rate of fire is essential for achieving a higher kill probability at the target end. Phase 2 was to be completed by 2014. It was reported that tests were held during August 2014 however tests are a continuous process and will carry on during the development phase of the gun. The Railgun is likely to be delivered by 2020-25.

Public debut. The Railgun made its public debut during the Navy’s Future Force Science and Technology Expo held at the Washington Convention Center in February 2015. One senior navy official explained the impact of the projectile to “a freight train going through the wall at a hundred miles an hour.” He added that the lack of gunpowder and explosive warheads eliminates some significant safety hazards for Navy crews.

Parallel development. General Atomics is developing a Railgun called the Blitzer System. The Electromagnetic Systems Group of General Atomics (GA-EMS) is actively working to bring Railgun technology to the Department of Defense for multiple missions to include integrated air and missile defence, surface fire support and anti-surface warfare. GA-EMS’s expertise in EM stems from GA’s long history in high power electrical systems, from developing and building both fission and fusion reactors, through the Navy’s first EM launch and recovery equipment for aircraft carriers. GA-EMS has developed, built and successfully tested two Railguns, the internally funded the Blitzer™ 3 MJ system and a 32 MJ launcher for the ONR. GA-EMS also designed and built the pulse power supply for both guns and is developing projectiles for air and missile defence and precision strike. GA-EMS is continuing the Blitzer family of Railguns with a 10 MJ system designed for mobile and fixed land-based applications. GA-EMS has announced in January this year that the projectiles undergoing firing, not only survived and operated under the 30,000 g-force and multi-Tesla magnetic field launch conditions.

Centre for Strategic and Budgetary Assessment (CSBA) Paper. During November 2014, CSBA released a paper on “Commanding the Seas: A Plan to Reinvigorate US Navy Surface Warfare.” in which they made wide ranging recommendations on capacity building, modernisation and a de novo approach for medium-range air defence for which, CSBA took a layered approach. The first layer is within the 30 nautical miles (about 55.5 km) zone which will be defended by 32 MJ Railguns coupled with Raytheon’s RIM-162 ESSM (Evolved Sea Sparrow) missiles which has a range of 50 km and a speed of Mach 4+. The logic for not using the long range of the Railgun was due to its limited manoeuvrability but compensated by its higher MV and less manoeuvring time available to the incoming supersonic missile at close ranges. In the 5 to 15 nautical miles (about 9.2 to 27.6 km) zone, a combination of laser weapon based defences (also under development) and Raytheon’s RAM (Rolling Airframe Missiles) were to be deployed. Such an approach would also release vertical launch cells for long-range offensive surface attack and air-denial weapons.

GA-EMS has developed, built and successfully tested two Railguns, the internally funded the Blitzer™ 3 MJ system and a 32 MJ launcher for the ONR. GA-EMS also designed and built the pulse power supply for both guns and is developing projectiles for air and missile defence and precision strike.

Challenges

Power supply. Both the Railgun and the laser-based weapons, require power supply which must deliver large values of sustained and stable currents. The most common components used for Railguns are capacitors and compulsators (an amalgam of the term Compensated Pulsed Alternator-originally conceived for Electromechanics to power laser flash-lamps for nuclear fusion research but since then found applications for powering experimental EM launchers). This poses a challenge for USA’s CG-47 cruisers and DDG-51 destroyers which have low power generation. Even a 32 MJ Railgun requires at least 15-30 MW of power onboard power generation, which is much more than these class of ships generate. 64 MJ Railguns, would require 40-50 MW capacity. This aspect will become one of the key factors of future design of ships having Railguns and laser-based weapons on board. In anticipation of the power demand from these weapons, the Navy’s brand-new Zumwalt class destroyer can generate up to 78 MW of power, of which it only needs 20 to operate. That means it can have lasers and Railguns that draw up to 58 MW of power. Probably in anticipation many countries are designing their ships based on all-electric configurations, which is why smaller Spanish and Australian Aegis frigates have a capacity of 40+ MW.

Recoil force. The rails need to withstand enormous recoil force (due to very high MV) during firing. This force will tend to push the projectile and rails apart and as gap increases, arcing develops which causes rapid vaporisation and extensive damage to the rail surfaces and the insulator surfaces. Thus early research was based on firing of one projectile at a time. Research is on to develop more suitable materials.

Type of materials. The rails and the projectiles must be built from strong conducive materials to withstand a very strong recoil force, force of the accelerating projectile and heating due to large currents and friction. This requires major developments in material science.

Heat dissipation. In the present configuration of the Railgun, massive amounts of heat is generated due to value of the current recoil force and the friction of the projectile leaving the system. The heat can cause thermal expansion of the rails and projectile, further increasing the frictional heat. This results in the melting of the equipment, reduced safety of the crew and easy detection by the enemy due to increased infrared signature. Thus the equipment used in a Railgun has to be higly heat resistance.

Other factors. There is an erosion of the rails after each firing and a degree of ablation (removal of material from the surface of an object by vaporisation, chipping or other erosive) of the projectile; both of which can be overcome by better material and design.

Railguns versus Coil Guns

A coil gun (or Gauss gun) is an EM gun that has a series copper coils instead of a barrel. These coils are energised sequentially, creating a moving magnetic field which attracts a ferromagnetic projectile down the barrel. Since the projectile of a coil gun floats on the magnetic field without touching any surface thus it causes less wear and tear, less heat and are completely noiseless. Coil guns have been demonstrated to propel projectiles at supersonic speeds but they are not as efficient or as capable as Railguns.

Railgun in Fiction

The Moon is a Harsh Mistress is a 1966 science fiction novel by Robert Heinlein in which lunar colonists, in his independence struggle from Earth, uses an EM launcher to fire iron containers filled with rocks at Earth. In the movie Eraser, Arnold Schwarzenegger stars as a Witness Protection Programme Agent who has by chance come across a secret government plot to sell Railguns to terrorists. Battlestar Galactica, the museum-era warship, is armed with Railguns that use both EM and conventional technologies. Railguns are also featured in video games like, ‘Quake’, ‘Metal Gear Solid’ and ‘Red Faction.’