By Richard Weitz
01/02/2011 – Although the concept of a rail gun is not a novel idea, and has been considered by militaries and science fiction writers for decades, only in the last few years has the technology developed sufficiently to allow fiction to become fact. This progress became evident in December, when the Office of Naval Research (ONR) broke kinetic energy performance records with a test of its Electromagnetic Railgun (EMRG) laboratory launcher at its Naval Surface Warfare Division in Dahlgren, Virginia on December 10.
The widespread use of rail guns on modern-day big-gun dreadnaughts is still in the future. Despite its record-breaking qualities, the recent test had only half of the power that the Navy wants for a militarily effective rail gun. The Navy estimates that a rail gun might be tested at sea by 2018 and might begin appearing on operational warships by around 2025, providing the substantial technical and cost barriers can be overcome.
Nonetheless, rail guns could fundamentally transform how navies fight one another and how they provide ground support for their army, marine, and even air force colleagues.
A rail gun uses rapid electric pulses to create a magnetic field to shoot a projectile that accumulates sufficient kinetic energy through its flight path to obliterate anything it impacts. It consists of two long metal rails. The rail gun works by moving large quantities of electricity from one rail to the other through an armature that connects the two. When switched on, the current moves up one rail, across the armature or projectile, and down the other. The resulting magnetic field forces the armature down the rails and out of the gun at supersonic speeds, as much as seven times the speed of sound (Mach 7), or 2-3 times faster than a conventional ship gun. The projectile could be the armature itself or something attached to it.
These properties make rail guns safer in several ways. Since neither the projectile nor the firing of the gun itself require any explosive charges or chemicals, both the ship and the rail gun itself are safer to operate — and keep in port or sail through constricted maritime passages — than conventional weapons and missiles.
And the projectiles fired by rail guns would leave no unexploded ordinance or “duds” on the battlefield to be destroyed by troops later — or that, if unattended, would inflict casualties on local civilians for years to come. Finally, supply chain management becomes easier and safer with rail guns since logisticians need only handle inert projectiles rather than explosive warheads and propellants.
In the recent EMRG test, the projectile breached Mach 7 and carried a potential energy of 33 megajoules (MJ). A megajoule is a measurement of energy for a mass traveling at a certain velocity. One MJ is equivalent to the energy released when a one-ton vehicle rams into a wall at 100 miles/160 kilometers an hour. The EMRG laboratory entered into service in 2006. The previous record, also established by the Navy, was set in 2008, with a 10 MJ shot.
Another advantage of a rail gun is its extended range. These electromagnetic cannons can launch a projectile approximately 20 times further than the conventional cannons now in use. This extremely long range of the rail gun also enables ships to support ground operations that occur much farther inland than the existing conventional guns on vessels. The estimated range of a ship-mounted 33 MJ rail gun would be about 110 nautical miles at an impact speed of around Mach 5 (3,840 miles/6,180 kilometers per hour).
These figures mean that a projectile could obliterate a target located 100 miles away in six minutes, which is faster than a cruise missile, and with the same pinpoint accuracy thanks to GPS. The ONR wants a laboratory test to achieve a range of 200 miles and power of 64 MJ before attempting to construct a real prototype. The enhanced range a power would further decrease the ship’s vulnerability to adversaries’ potential access-denial strategies.
The use of rail guns for combat could prove to be a revolutionary weapon for a number of reasons, giving its operators unique capabilities. Thanks to their technologies, GPS and other support, rail guns can be extremely accurate.
As in the case of missiles, where their “circular error probable” is very important, higher accuracies can boost destructive power much more than increases in explosive yields. The Chief of Naval Research, Rear Admiral Nevin Carr, has remarked that, due to its high accuracy, “the gun could be aimed at a magazine on an enemy ship and ‘let his explosives be your explosives.’” Carr also wrote in his report on the test that “the high velocities achievable are tactically relevant for air and missile defense.”
One of the main goals behind the development of rail gun technology is to create a weapon that could provide close-fire support for friendly ground forces from a greater distance. Besides allowing the ship to cover a wider range of potential targets, the enhanced distance provides greater protection against anti-ship weapons. Furthermore, a ship-mounted rail gun could be directly used against enemy ships.
In theory, with much further technological progress, smaller rail guns could even be mounted on airplanes to provide a substitute for the stand-off capabilities now offered by air-launched ballistic and cruise missiles.
Some missile defense experts believe that rail guns could also shoot down ballistic missiles. For that reason, they were in the roster of weapons included in President Reagan’s “Star Wars” Strategic Defense Initiative.
Despite these revolutionary capabilities, the concept and design of rail guns date back to World War II. As with many modern weapons used by militaries today, the first and earliest design of rail guns were developed by German scientists and technicians during the Nazi era. The Soviets created a bureau to study the feasibility and potential design of such a project, but decided not to pursue it.
More recently, the Iraqi Survey Group discovered when it entered Iraq after the March 2003 war that Saddam Hussein’s regime had sought in the late 1990s to produce rail guns to create better antiaircraft weapons — presumably to challenge the various no-fly zones the coalition forces established after the 1991 Persian Gulf War — and be able to attack Israel with additional weapons besides the SCUD ballistic missiles. The fact that the same scientist in charge of Iraq’s rail gun research, Dr. Khalid Ibrahim Sa’id, also led Iraq’s pre-1991 nuclear weapons program has encouraged speculation that Iraq’s rail gun project was a cover to study and harness technology that was applicable to both rail guns and nuclear weapons. Regardless, Iraq was unable to develop either unconventional weapon.
Iraq’s motivation to develop rail guns may have been inspired by Russia. Iraq’s pursuit of rail gun technology began in 1993, after an Iraqi scientist returned from his studies in Russia and wrote a paper heavily advocating the development of rail guns. Russia’s research into rail gun technology began a century ago, but apparently never reached the level where its government sought to invest enough resources to develop the technology. The progress demonstrated by the U.S. Navy may reinvigorate Russian interest in electromagnetic weapons. The Chinese almost certainly will seek to develop these weapons.
Developing an effective and practical rail gun requires overcoming substantial technological and logistical challenges. For example, further advances are needed to develop improved cladding and compaction technologies to reduce the wear on rail gun barrels, which remains a persistent problem given the friction created by moving objects at such high speeds along the rails. The strong current will melt even the sturdiest materials in a couple of shots.
The ONR anticipates that the current laboratory gun could only be used 2-3 times before the rails would be destroyed by the rapid passage of the armature along them. But perhaps the most complex problem is that Congress has mandated that the next generation of Navy cruisers be nuclear powered, but utilizing nuclear power creates incompatibility issues with the electric transmission needed to energize a rail gun.
Furthermore, designing a platform from which a rail gun, which has the size of a bus, can be successfully mounted is difficult. Because of the nature of the rail gun and the need to utilize large amounts of space and electrical power, about the only mobile weapons platform that could carry an electronic rail gun would be a large warship.
In addition, the U.S. Navy must design a ship from the start to house and power a rail gun. Given the slow pace of U.S. Navy shipbuilding, this means that it could take decades before the entire fleet is equipped with rail guns.
Before assuming office, Under Secretary of the Navy Robert O. Work recommended that, “The Navy should immediately begin designing a new modular large battle network combatant (LBNC). The new combatant should have a spacious hull, with plenty of installed electric power (so as to employ future weapons such as electromagnetic rail guns and lasers), a modular combat system suite, room for a substantial VLS battery, and an ability to employ a variety of offboard systems.” Work calculated that these new combatant ships could be built for less than $2.5 billion per vessel.
Rail guns differ from directed-energy weapons (DEWs) like lasers, which destroy targets by transferring a concentrated beam of energy to the target. DEWs have a number of advantages over traditional projectile weapons such as missiles. For instance, since a laser beam travels at the speed of light, there is no need to compensate for target movement when firing over long distances. The lack of kinetic effects also allows for more precise targeting, which can minimize collateral damage.
As with rail guns, the Navy has assumed a lead role in deploying DEWs, but primarily as weapons for close air defense rather than long-distance power projection, and mainly as a complement rather than substitute for existing kinetic weapons, which for at least a while will remain more effective at attacking faster manned warplanes as well as ground-based targets.
The main problem with moving DEWs from the laboratory to the fleet has been their enormous energy requirements, the high temperatures they produce, and their delicate construction and maintenance. Modern Navy ships have enormous power-generation capacity, readily available coolant in the form of water, and typically sail with skilled maintenance crews in charge of well-integrated combat, communications, logistics, and other integrated systems.
It is perhaps no accident that supporters of the rail gun recommend integrating rail guns and DEWs on new ships. The Navy sees rapid-fire DEWs as especially useful in countering the growing threat of anti-ship missiles, high-speed small boat attacks, and other close-in threats.
And the longer-range of the rail gun will enable the ship to operate from much greater distances from these potential threats, reducing the quantity of threats the DEWs and other defensive ordinance will need to address as well as giving them more time to do so.
Finally, the high speed and accuracy of a rail gun could also allow them, with adequate targeting information, to destroy a hostile ship or plane at much greater distances than DEWs, potentially even while they are moving as well at stationed on base.
The Royal Navy’s new Type 45 destroyers are the first warships to employ electric transmission for their main full-speed propulsion. This electrical power source is more than compatible with rail gun requirements and can supply more than 40 megawatts of electricity. If a rail gun in its current proposed state were mounted on one of these ships, the electric power plant on the ship could recharge the gun in a mere second and a half after firing. The caveat is that at this firing rate, the ship would not be able to move or navigate as all power would be directed towards the rail gun. But if a rail gun dreadnought were constructed to the same size as the largest ship afloat, a U.S. Navy Nimitz-class carrier but with electric transmission rather than the Nimitz’ twin 550-megawatt nuclear reactors, it could in theory fire 15 Mach-7 projectiles every second while still moving (an important capability if the Chinese and others are able to develop anti-ship ballistic missiles).
Even so, the high costs of the large platforms required by rail guns could pose a greater barrier than the technical obstacles to their widespread use on Navy ships in coming years. (The gun complexes themselves are fairly inexpensive; the Navy has spent only $211 million so far on its rail gun demonstration project.)
The Pentagon has decided to cut back purchases of the multipurpose Zuwait-class DDG-1000 destroyers, which are potentially ideal platforms for rail guns. The U.S. Navy now plans to purchase only three such ships, which can better overcome increasingly lethal, land-based, maritime reconnaissance and strike systems than existing Navy ships.
But these kinds of large, modular surface combatants have copious hull and considerable electric power for DEWs and rail guns. The absence of expensive missiles and munitions could make rail guns and lasers more cost effective than many conventional warships. And the greater survivability and more effective striking power of ships armed with rail guns means that a fleet of such vessels could be smaller in number but more powerful in application.