The Railgun, which Shoots on Electric Rails at Speeds of up to Mach 6, is a Feat of Engineering and an Act of Military Artistry

U.S. Naval Surface Warfare Center - Dahlgren Division

RAILGUN: THE GUN FOR THE FUTURE

DISCLAIMER This work was produced under the sponsorship of the Department of Defense. However, any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the Department of Defense.

IMAGE INFO Cover and Page One: Source, Defense Visual Information Distribution Service, Photo by John Williams

A team of engineers at the Naval Surface War Center Dahlgren Division, in Virginia, has been working on the electromagnetically charged railgun for more than a decade. The combination of extremely fast speeds with electromagnetic power generation make the railgun a potentially revolutionary tool for the warfighter: faster, safer, less expensive, optimized for integration, and of course, lethal. The engineers believe the railgun will be the disruptive technology that will change the face of naval warfare as we know it.

Naval Surface Warfare Center Dahlgren Division Dahlgren, VA Public Affairs Contact: Alan Black, alan.black@navy.mil

Prepared for BEST by THE CENTER FOR HOMELAND SECURITY AND RESILIENCE

Submission Date March 16, 2018

OVERVIEW

NSWC Dahigren | 3DoD Lab Narrative | Railgun: the Gun for the Future, at Terminal Range

Deep behind the two-foot walls of a windowless room a team of scientists sit around an L-shaped table discussing the science of manufacturing weaponry— in this case, the world’s most sophisticated gun. Like paleontologists, they hover over the detritus of metal that has gone into this project.

On long tables, displayed like precious archeological finds, are the projectile components recovered after each firing of the gun. They’re made of aluminum, tungsten, steel and other alloys, and some have ragged protrusions and jagged edges. Like fossils, these pieces of twisted and warped metal tell a story of extremes -- of heat, of speed, of the very laws of physics.

An engineer named Chester Petry hovers nearby, explain-ing why this pile of scientific debris is one of the great technological leaps in modern warfare: a glimpse into the evolution of a futuristic weapon known as a railgun.

Petry and other engineers at the Naval Surface War Center Dahlgren Division, in Virginia, have been working on it for more than a decade, and believe it to be the disruptive technology that could change the face of naval warfare as we know it.

Unlike virtually every other gun produced since the Chinese invented the firelance, the predecessor of the modern firearm, the railgun doesn’t use gunpowder. Instead, it uses an electromagnetic pulse that fires war-heads along a pair of charged rails, like a train, at speeds reaching close to 5,600 miles an hour, or Mach 6.

The combination of extremely fast speeds with electro-magnetic power generation make the railgun a potentially revolutionary tool for the warfighter: faster, safer, less expensive, optimized for integration, and of course, lethal.

“What we always say around here is that speed...” Petry hesitates a moment, “Speed kills.”

The railgun is so futuristic, in fact, that the Navy has faced challenges trying to figure out where it fits into its existing

RAILGUN: THE GUN FOR THE FUTURE The railgun, which shoots on electric rails at speeds of up to Mac 6, is a feat of engineering and an act of military artistry

arsenal. For most of its development, the railgun’s energy requirements have been too burdensome for a mobile deployment and too advanced for the Navy’s existing fleet of ships. Nevertheless, the program has made impressive gains in the energy density of its pulsed power system, and its modular design enables a flexible approach to integration onto a surface combatant.

Petry cuts an imposing figure. Mustachioed, brisk and matter-of-fact, he’s in his late 50s but exudes a boyish enthusiasm for the possibilities of the technology. Tall and muscular, he’s an engineer’s engineer— fluent in the vocabulary of switches, force fields, and the complex mathematical equations required to pursue this advanced physics problem.

But while the science is advancing every day, what the railgun really needs, Petry says, is “a champion.”

New Life to Old Guns

When Petry joined the railgun mission in 2000, his son, Logan, was just a toddler. So Petry set himself a goal. Before Logan was old enough to become a sailor, Petry vowed to make the dream of an electromagnetic gun that could fire a projectile 200 nautical miles a reality. It was a fearsome technical challenge, and Petry, a rock climber, was ready for the job.

The railgun has been a long time in the making.

Back in the 1970s, a group of engineers at Dahlgren led by the site’s then technical director James Colvard were working on the very same concept, known in those days as an “electric gun.” They had already discovered the electromagnetic power pulse that would thrust a projec-tile forward. But they ran into trouble with the gun itself. When they tried to fire it, the power pulse generated such heat that it melted the gun’s metal sheathing.

“The high speed motion melted the contacts on the rail because the material wouldn’t withstand the temperature

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generated by velocity of the projectile,” Colvard says. “So we put it on hold until different materials came along.”

It would take a couple of decades before the necessary metals appeared, but the dream of the railgun didn’t die. The U.S Army worked on a version that could be mounted on a tank, collaborating with British forces at a lab in Kirk-cudbright, Scotland, in the early 2000s.

The Navy got back into the railgun game around 2001, as traditional guns seemed to reach their technological limit, Petry says. “We started investigating other venues, technologies to replace or extend the capabilities of guns, to shoot bullets faster and farther.”

The Navy hoped to be able to mount the gun on a ship. Petry, then a junior systems engineer at Dahlgren, was named to help steer the Navy’s Innovative Navy Prototype (INP) program forward.

“We were taking an old gun technology and giving it a new life,” Petry says.

Dahlgren was the perfect place for this kind of revolu-tionary technology. The base had a storied history in the annals of military science; from developing the Norden bombsight and the radio proximity bomb fuze to leading the Ordnance Division of the Manhattan Project.

Dahlgren has had several firsts, including the world’s very first unmanned aerial vehicle, a specially configured N-9 utilizing a new radio-controlled system, from Dahl-gren July 24,1924. After the base, located on the Virginia banks of the Potomac River, was transformed into from a proving ground, it is now a destination for other kinds of technologies, such as directed energy, laser weaponry, and spectrum operations.

The Office of Naval Research (ONR)-sponsored Electromagnetic Railgun (EMRG) at terminal range located at the Naval Surface Warfare Center Dahlgren Division (NSWCDD). The EMRG launcher is a long-range weapon that fires projectiles using electricity instead of chemical propellants. (U.S. Navy photo by John F. Williams)

NSWC Dahigren | 5DoD Lab Narrative | Railgun: the Gun for the Future, at Terminal Range

Terminal Range

The railgun project proceeded slowly at first. Pine forests had to be cut down for the lab buildings that didn’t yet exist. The buildings themselves had to be engineered to protect the sensitive materials inside from external radio waves, which could disrupt their work by remotely trigger-ing the sensitive electromagnetic sensors stored inside.

Scientists then spent a long time simply trying to figure out if the physics of the concept would actually work. New metals had been found that could withstand the force of the electromagnetic power, but there were other basic research challenges. How to keep the gun intact under such tremendous forces? And how to build a bullet that could be guided toward a target? All of these questions swirled as the team got underway.

The Phase I Navy Prototypes laid the groundwork for the later stages that produced the Phase II prototypes operat-ing on the base today.

At first, senior Navy command staff had expressed interest in a gun that could fire a projectile 200 nautical miles, which would have extended the range of a traditional cannon by several factors, and also given warships increased standoff distances in combat situations. Over time, however, the leadership scaled back its desire for distance in favor of more mission flexibility.

One reason was that the existing canons in the Navy’s arsenal, already mounted on the fleet’s ships, were also capable of firing the sleek new rounds that the railgun’s research was also yielding. This meant the Navy could have better large caliber bullets that traveled greater dis-tances while waiting for railgun technology to mature.

Initially, the targets were stationary. Land targets like radars, tanks and infrastructure.

By 2010, the leadership had expanded the goal and decided it wanted the gun to be able to have a greater target range. “We expanded our mission set from land attack to include targets in the air and on the sea,” says Petry. “To a multimission capability, for aircraft and mis-sile threats, and surface warfare.”

The distance requirement was reduced from 200 nautical miles to 100 because the system would be smaller and require less power to operate. It was also believed the shorter range system would be less technically chal-lenging and could be developed more quickly. The Navy wanted more lethality, but also more complementary air support, a shorter range, but greater targeting capability.

Part of these ongoing changes were due to the success Petry and his team had been having in designing an improved projectile, which had been part of the project.

Explaining all this, Petry leaps up from his seat at the table inside a testing facility at Dahlgren’s Terminal Range, where the laboratory walls are two feet thick and the buildings are fiber-optically insulated from radio waves that could inadvertently trigger an unwelcome electromagnetic interaction.

He picks up a sleek oblong warhead, called a Hyperveloc-ity Projectile, or HVP, and cradles it proudly. At 23 pounds, it’s heavy, but far lighter than comparable powder-driven projectiles. Part of the railgun testing included designing a new kind of projectile that would fit the gun’s parameters. This new round could go faster and farther, and at greater speed, than anything else they had. When the Navy real-ized the dual-use capability of HVP, the railgun’s future was less certain since resources may not be available to support both gun applications.

The Debate

Petry recalls the day the engineers found out the Navy was thinking of putting this new and improved projectile into the same old powder-driven weapons. The scientists had gathered to debate the Navy’s seemingly shifting priorities. Some were in favor of urging the leadership to keep going full steam ahead with the railgun project. They had poured themselves into the work for months, even years, and they didn’t want it overshadowed by an older, increasingly out-of-date technology.

Others saw the short-term advantages that could come with this more intermediate step. The group discussed the issues at great length. Analytical and circumspect, Petry isn’t prone to drama, but even he concedes that the scientists were at a momentary loss about the best course of action.

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the barrel in short, extremely rapid bursts that cascade down the length of the barrel, propelling the warhead out in one highly energetic and powerful burst.

“There’s a rippling,” Petry says, fluttering his fingers.

But Petry and his colleagues knew from the beginning that these “ripples” of energy took an immense toll on the physical machinery. Merely keeping the two sides of the barrel together was a problem that required some serious engineering. The scientists were concerned primarily with a law of physics called the Lorentz Force, which threat-ened to pull the rails apart once the pulse was introduced into the barrel.

Engineers knew that if the barrel wasn’t fused under enough pressure, the electromagnetic pulse would destroy it. So they used a hydraulic pressure system to, in a sense, push the two sides together with huge force.

Then, the two sides were sewn together with long and large insulated bolts about the diameter of a coffee cup, all pressurized at the same time to exert the desired force upon the gun. The battery-stored energy was connected to the gun with coaxial cables, like old TV cables, which have inner and outer conductors, canceling out the elec-tromagnetic field.

“It’s the same force as if there were two ships sitting on it,” says Petry. “It literally squeezes the two halves of the barrel -- the gun -- together.”

He chuckles, marveling at the beast of a gun in his lab. “Yeah, there’s a lot of pressure sitting on that thing.”

If that kind of pressure seems extreme, consider the kind of energy that a single blast from the batteries is going to deliver. One push on the railgun “fire” button and 3 to 5 million amps of electricity pulses into the barrel. By com-parison, one lightning bolt is about 100,000 amps. That’s nine orders of magnitude stronger than your average high school circuit board.

“I don’t know of anything out there that deals with these kinds of currents,” says Petry. “It’s one of the most power-ful electrical devices in existence.”

The result was lethal.

“It got pretty heated,” Petry says. “By 2010, we’ve got a lot of Navy 5-inch guns in the fleet. The Navy said it wanted to take the technology from this railgun and use it in these other guns. It was a big turning moment, and there was a heated debate around here. There were a lot of questions, primarily: do we want to suboptimize our tech for these old guns?”

It was around that time that Petry’s engineers also made another technological breakthrough that would have lasting effects. They began pursuing a “convex shape” instead of a “round bore gun,” which changed the shape of the rails inside the gun, allowing for far greater contact with the projectile and thus more speed. The scientists, Petry says, “weren’t constrained by the traditional gun barrel design.”

The Navy’s decision cut both ways. The new projectiles would be used in the old powder guns. But work on the railgun would also proceed as planned.

Eventually, work on the railgun moved ahead. And the team focused its efforts on making the tech go into both the old 5-inch guns and the railgun. Petry and the other engineers were slowly working out the kinks. From 2010 to 2017, they worked on modeling, interface for bullets, simulation, and predicting what they needed to design for the next big challenge: a repetition-rate capability.

They wanted to engineer the railgun in such a way that it could fire multiple rounds, at a high rate of speed, on its own. Traditional guns did plenty of that, but the tremen-dous electricity and heat involved in each railgun shot made it an enormous challenge.

‘Ripples’

The railgun itself was a feat of physics engineering.

The main barrel of the INP test gun at Dahlgren’s range is ten meters long, and is comprised of two sides that have been bolted together under enormous pressure. Connected to this barrel by a series of cables is a bed of batteries and capacitors, which store vast amounts of electromagnetic energy.

When the gun is fired, many pulses of energy funnel from the batteries and capacitors, through the cables, and into

NSWC Dahigren | 7DoD Lab Narrative | Railgun: the Gun for the Future, at Terminal Range

In tests on Dahlgren, Petry’s team placed a “typical truck” in the weapon’s path.

Petry won’t go into details, but says, “We were effective.”

“You wouldn’t trade it out at a dealership,” says Alan Black, director of communications at the division.

Similar results can be seen outside one of the labs at Terminal Range, where four giant slabs of rusted metal, each with a jagged hole torn through the middle sit in testament to the railgun’s sheer power.

When asked how the railgun would work on an airborne target, such as a plane, Petry explains that when the payload opens, it creates a wall of shrapnel traveling at hypervelocity, each small fragment bearing a huge amount of kinetic energy, the “speed kills” aspect of the equation. For an airborne target racing toward this wall of shrapnel, the results would be devastating.

“If there’s a wall of pellets coming your way,” says Petry, “It’s the closing speed that counts, not the absolute speed.”

Turning Dream into Reality

In early summer 2017, the scientists made another major breakthrough.

It was June, and the scientists had gathered at Dahlgren to watch the gun fire itself, Petry describes it as a “key-stone moment.”

They gathered inside a safety shelter near the test stand where the railgun was mounted and ready to roar. Petry says he was nervous and excited as he sat in an adjacent room where video monitors had been set up to record the event. He wanted the gun to perform, he says, and though he didn’t voice his concerns, he wasn’t quite sure what to expect. As the team ramped up the charge, Petry, seated

Abstract 3D form of electromagnetic wave.

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at a conference table where the signals were being fed into a video system, waited anxiously for the test shot.

Whereas before each test had required an engineer to feed the projectile into the barrel, and then press the fire button, now a robotic arm was reaching down to pick up the projectile and feed it into the barrel.

But when it came, he almost missed it, he says.

They finally engineered the long desired repetition rate. The sheer power generated by even one shot of the gun could be awe-inspiring, “like managing multiple strokes of lightning with every shot,” says Petry.

Luckily for Petry, live video feeds captured everything.

In one way, the improvements in robotics was a small advance, but it was exactly the kind of thing that would enable the Navy to eventually install the railgun onto a future naval surface combatant with enough electrical power to generate the energy necessary to fire the railgun at 32 megajoules of muzzle energy with a high repetition rate, at speed, and the requisite 100 nautical miles.

“I couldn’t even keep up with all the screens,” Petry says. “Things were happening so fast. By the time I did, the gun was charged, loaded and ready to fire again. The com-puter was making the decisions.”

The team did a two-round salvo that day, and felt extremely proud.

If all goes well, they’ll eventually work up to a 50-round salvo.

If the development of a future naval surface combatants occur in tandem with the railgun project, it would pave the way for the kind of systems integration that Petry and the other early railgun pioneers have long desired.

“We’d be tied to the ship’s electrical systems more than any other weapon,” he says. “For example, the Zumwalt class with its large power generation capability is like Star Trek’s ‘Scotty, more power to the weapons’ idea.”

“Why is the railgun so disruptive?” Petry asks. “Because it’s not an incremental change. It’s changing gunpowder

for pulsed power. It’s going from unguided to guided. And it’s using a bullet that will go in both today’s and tomor-row’s guns.”

The engineers have already set up testing sites at the White Sands proving grounds, in New Mexico.

“We have a team regularly going there. We’re trying to bring this capability to the fleet as soon as possible. “We do feel like we have a— all the team members feel like they have a stake in the technology, they want to see it move forward.”

The dream Petry had for the railgun when Logan was a boy hasn’t yet materialized. Now Logan is in college. He’s not going to be a sailor; he’s following the engineering path.

Petry is proud of the success of the Railgun Program. “We have developed materials, rail geometries, and computer models of the in-barrel physics—we have used these developments to advance barrel life and demonstrate repetition-rate capability. One day, the Navy will embrace the future of electric weapons.” Petry has a few more years before he’s going to retire -- years he plans to spend making the railgun dream a reality for the Navy and Sail-ors of the future.

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