Railguns have launched projectiles at speeds up to about 6 km/s, or roughly Mach 17, which is more than five times faster than a typical rifle bullet leaves the barrel. That figure alone makes railguns one of the fastest ground-based launchers ever built, but the science behind how they reach those speeds and what happens when a projectile arrives at its target is stranger and more complicated than the raw number suggests.
The Speed Range and What It Means
Experimental railguns have reached muzzle velocities up to 6,000 m/s, according to published research on electromagnetic launcher performance.1Applied Mathematical Modelling. Forces of rails for electromagnetic railguns To put that in everyday terms, 6 km/s is about 13,400 mph or roughly 21,600 km/h. At that speed, a projectile could cross the length of a football field in under two hundredths of a second. A conventional rifle round, by comparison, typically leaves the muzzle at somewhere between 900 and 1,200 m/s, and the fastest conventional tank guns top out around 1,800 m/s. So the upper end of railgun performance represents a threefold to sixfold improvement over what chemical propellants can deliver.
Not every railgun shot hits that ceiling. Laboratory demonstrations have covered a wide range depending on the size of the projectile, the length of the rails, and the energy fed into the system. Smaller, lighter projectiles in long-barreled research setups reach the highest figures. Military prototype tests, which fire heavier slugs designed to survive the trip and do damage on arrival, have typically reported speeds in the range of 2,000 to 2,500 m/s, still far beyond what a conventional naval gun can manage. The gap between laboratory peak and practical weapon reflects engineering tradeoffs that are central to why railguns remain difficult to field.
Why Electromagnetic Acceleration Beats Chemical Propellants
A conventional gun works by burning a chemical propellant inside a sealed chamber. The expanding gas pushes the projectile down the barrel. The speed ceiling for this process is set by the expansion rate of the gas itself, which means there is a hard thermodynamic wall. No matter how energetic the propellant or how long the barrel, the projectile cannot outrun the gas that is pushing it. That wall sits at roughly 2 to 2.5 km/s for practical gun designs.
A railgun sidesteps this limit entirely. Instead of hot gas, the driving force is an electromagnetic field. Current flows through two parallel conducting rails, and a sliding armature (which sits behind the projectile) completes the circuit between them. The current creates a magnetic field in the gap between the rails, and the interaction between that field and the current produces a force on the armature, pushing it and the projectile forward.1Applied Mathematical Modelling. Forces of rails for electromagnetic railguns Because this electromagnetic force propagates at the speed of light in principle, the theoretical velocity ceiling for a railgun is vastly higher than for any chemical gun.2IEE Review. Field’ guns: electromagnetic launchers
In practice, of course, no railgun fires projectiles at anything close to light speed. Friction, electrical resistance, rail heating, and the structural limits of the projectile and armature all impose real-world constraints well before theoretical physics runs out of headroom. But the fundamental advantage is clear: the mechanism doing the pushing is not bottlenecked by the speed of expanding gas, so the engineering limits sit much higher.
What Hypervelocity Does on Impact
Speeds above roughly 3 km/s enter the regime physicists call “hypervelocity,” and impacts at these speeds behave very differently from ordinary ballistic events. At normal bullet speeds, the outcome of an impact depends heavily on the material properties of both the projectile and the target: hardness, toughness, how the metal fractures. At hypervelocity, those properties start to matter less. The pressures involved are so extreme that both the projectile and the target material behave more like fluids than solids.
Research on this transition regime shows that between high-velocity and true hypervelocity impact, there is a gradual shift from effects dominated by material strength to effects driven by massive increases in internal energy, including thermal softening and outright melting.32022 16th Hypervelocity Impact Symposium. Transition Regime between High-Velocity and Hypervelocity Impact and Related Energy Partitioning in Metals Ideal hydrodynamic behavior, where the projectile and target flow into each other like colliding jets of water, is not fully reached until speeds of several kilometers per second.32022 16th Hypervelocity Impact Symposium. Transition Regime between High-Velocity and Hypervelocity Impact and Related Energy Partitioning in Metals This is why railgun advocates emphasize kinetic energy rather than explosive warheads: at Mach 6 or above, a solid metal slug carries so much energy that it does not need a chemical explosive to cause devastating damage. The kinetic energy alone can punch through thick armor plate, and the impact generates enough heat to vaporize material at the strike point.
This matters for both military applications and for understanding space debris. Orbital debris collides with satellites at 7 to 15 km/s, and railgun-speed projectiles are one of the few ground-based tools researchers have for simulating those impacts in the lab.
The Rail Wear Problem
If railguns are so fast, why haven’t they replaced conventional weapons? The biggest practical obstacle is that every shot damages the gun itself. The armature slides along the rails at enormous speed while carrying millions of amps of current, and the combination of extreme friction, intense heat, and electromagnetic pressure eats away at the rail surfaces.
One particularly damaging phenomenon is rail gouging. As the armature accelerates, it can tilt or lean toward one side of the bore, driven by uneven forces or vibrations. This creates an oblique impact between the armature and the rail surface, which digs grooves into the rail material.4International Journal of Applied Electromagnetics and Mechanics. Armature dynamics – an aspect of rail gouging mechanisms in electromagnetic railgun Over repeated firings, these gouges accumulate and degrade the bore, reducing accuracy and eventually making the gun unsafe to fire. A conventional naval gun barrel can last for hundreds or even thousands of rounds before it needs replacing. Early railgun prototypes showed serious degradation after far fewer shots.
The rails also suffer from arc ablation, where electrical arcing between the armature and rail surface vaporizes and erodes the metal. This is compounded by the sheer thermal load: the rail surface heats up dramatically during each shot and does not have time to cool between rapid firings, which means the material weakens progressively.
How Materials Science Is Trying to Solve It
The conducting rails of most electromagnetic launchers have been made from copper alloys, including copper-chromium, copper-chromium-zirconium, and copper-tungsten blends, chosen for their excellent electrical and thermal conductivity.5Defence Technology. Research progress on advanced rail materials for electromagnetic railgun technology Good conductivity means more of the electrical energy goes into accelerating the projectile rather than heating the rails. But copper alloys, despite their conductivity, have not been durable enough to sustain many shots without significant wear.5Defence Technology. Research progress on advanced rail materials for electromagnetic railgun technology
The current research focus has shifted toward surface coatings and treatments that let engineers keep copper’s conductivity while borrowing hardness and wear resistance from other materials. Techniques under investigation include electroplating, cold spray deposition, supersonic plasma spraying, and laser cladding, all aimed at applying a tough outer layer to the copper rail surface.5Defence Technology. Research progress on advanced rail materials for electromagnetic railgun technology The ideal rail material would combine high electrical conductivity, high hardness, high thermal conductivity, and strong resistance to both abrasion and arc ablation. No single material checks all those boxes easily, which is why the coatings approach, layering properties from different materials, has become the main avenue of research.
Progress has been real but incremental. The challenge is that a coating which holds up beautifully in a static test can delaminate or crack under the extreme and rapidly cycling conditions inside a railgun bore. Solving durability is widely considered the gating issue for fielding a railgun that can fire enough rounds to be militarily useful.
The Power Supply Challenge
Speed is only half the engineering problem. The other half is generating and storing enough electrical energy to fire the gun in the first place. A single railgun shot at weapon-relevant energies requires tens of megajoules delivered in a pulse lasting just a few milliseconds. For comparison, a typical American household uses about 30 kilowatt-hours of electricity per day, which works out to roughly 108 megajoules spread over 24 hours. A railgun needs a comparable chunk of energy dumped into the rails almost instantaneously.
This demands specialized pulsed power systems: banks of capacitors, rotating machines called compulsators, or a combination of both, all sized to charge up between shots and discharge in a sharp burst. The systems are physically large and heavy, which is one reason railguns have been tested primarily on ships (where space and power generation are more available) rather than on trucks or aircraft. The U.S. Navy’s prototype testing involved purpose-built power conditioning systems that occupied a significant footprint alongside the gun itself.
Firing rate is constrained by how quickly the energy storage can recharge. A conventional automatic cannon can fire several rounds per second because each round carries its own chemical energy. A railgun depends on an external power plant and energy bank, and the recharge cycle between shots is measured in seconds at best. Faster recharge means bigger and heavier power systems, which pushes back against the goal of making the weapon compact enough to deploy.
How Railguns Compare to Other Hypervelocity Launchers
Railguns are not the only way to push objects to extreme speeds. Two-stage light gas guns, which use compressed hydrogen or helium heated by a powder charge, can reliably accelerate small projectiles to velocities between 1.5 and 8+ km/s.6engrXiv. Empirical Models for Predicting Two-Stage Light Gas Gun Muzzle Velocity That upper range actually exceeds the demonstrated performance of most railguns. Light gas guns achieve this by using a light gas (hydrogen is preferred because its molecules move fast) as the accelerating medium, sidestepping the speed-of-sound limitation of heavier propellant gases.
So why bother with railguns at all? The difference is in what each technology is suited for. Light gas guns fire very small projectiles, often just a few grams, and are primarily research tools for studying hypervelocity impact in laboratory settings. They are single-shot devices with elaborate setup procedures. A railgun can, at least in theory, fire larger and heavier projectiles repeatedly, which makes it interesting as a weapon system. The tradeoff is that a light gas gun at the high end of its performance envelope can outrun a railgun in pure velocity, but it cannot do so with a projectile heavy enough to serve as a weapon or in a form factor that could be mounted on a vehicle.
Coilguns (also called Gauss guns) represent another electromagnetic approach. Instead of sliding the projectile along energized rails, a coilgun pulls the projectile through a series of electromagnets switched on and off in sequence. Coilguns avoid the rail-contact problem entirely, since the projectile never touches the barrel walls, but they have generally achieved lower velocities than railguns in practice. The timing precision required to switch coils at very high projectile speeds is an extreme engineering challenge.
Beyond Weapons and Ballistics Testing
The public image of a railgun is a futuristic naval weapon, but the same technology has been explored for purposes that have nothing to do with warfare. One of the more surprising applications is in nuclear fusion research. Tokamak and other fusion reactors need to inject fuel pellets, tiny frozen hydrogen pellets, into superheated plasma at high speed. If the pellet is too slow, it ablates and breaks apart before reaching the plasma core. Researchers have developed small-scale railgun systems specifically to accelerate hydrogen pellets for injection into fusion experimental devices.7Fusion Engineering and Design. Railgun pellet injection system for fusion experimental devices These are miniature, low-energy railguns compared to military prototypes, but they exploit the same electromagnetic principle to achieve the speed needed for effective fueling.
Space launch is another concept that has attracted periodic interest. If you could build a railgun long enough and powerful enough, you could in theory launch cargo (not humans, the acceleration forces would be lethal) into orbit without a rocket. The energy requirements and barrel length needed are staggering, and atmospheric drag at launch altitude would be a serious problem, but the concept has been studied seriously enough to generate engineering analyses. The appeal is economic: electricity is far cheaper per joule than rocket fuel, so a ground-based electromagnetic launcher could slash the cost of putting bulk cargo, like water or construction materials, into low Earth orbit.
Materials testing is the most mature non-military use. Researchers studying how spacecraft shielding, armor, or geological samples behave under extreme impact conditions need a way to throw small objects at several kilometers per second under controlled laboratory conditions. Railguns and light gas guns serve this purpose, and railguns offer the advantage of being electrically tunable: you can adjust the speed shot-to-shot by varying the current, which makes it easier to map out impact behavior across a range of velocities.
Why Military Programs Have Stalled
Despite decades of research and hundreds of millions of dollars in development funding, no military has fielded an operational railgun. The U.S. Navy, which ran the most prominent program, scaled back its efforts in the early 2020s after years of testing at facilities in Virginia. The reasons tie back to the engineering problems described above: rail wear limited the barrel’s useful life, the power systems were bulky and slow to recharge, and conventional missiles had meanwhile grown cheaper and more capable. The cost-per-shot advantage of a railgun (a solid metal slug is cheaper than a guided missile) erodes quickly when you factor in the cost of the gun itself, the power infrastructure, and the frequency of barrel replacement.
China has continued publicized testing, including what appeared to be a railgun mounted on a naval vessel in 2018, though detailed performance data has not been made public. Several other countries maintain research programs at various scales. The technology is not dead, but the timeline for practical deployment keeps stretching. Improvements in energy storage, particularly from advances in capacitor technology and compact power generation driven by broader trends in electrification, could eventually shift the calculus. For now, the railgun remains a technology that works impressively in the lab and stubbornly resists deployment in the field.
The Atmospheric Problem at Extreme Speed
Even if rail wear and power supply were solved tomorrow, firing a projectile at Mach 17 through the atmosphere introduces its own set of headaches. At those speeds, the air in front of the projectile compresses into a superheated shockwave. The projectile’s surface can reach thousands of degrees within moments of leaving the barrel, and ablation, the physical removal of material from the projectile’s surface, begins immediately. A projectile that leaves the muzzle perfectly shaped can lose mass and change shape during flight, which degrades accuracy.
This is why railgun projectiles for military applications are designed with aerodynamic shrouds and heat-resistant materials, not just for penetration but for survivability in flight. The engineering overlap with atmospheric reentry vehicles is not a coincidence: a railgun projectile at 2 km/s faces thermal and aerodynamic conditions comparable to what a small reentry body experiences coming back from space, just without the benefit of a gradual deceleration profile. The projectile hits peak heating almost instantly and has to endure it for the entire flight to target.
Range is limited partly by this atmospheric drag. A projectile that starts at Mach 7 loses speed rapidly as the atmosphere saps its kinetic energy. The higher the initial speed, the higher the drag losses in the dense lower atmosphere. Proposed solutions include launching at a steep angle to get the projectile into thinner air quickly and then letting it arc down to the target, or using scramjet-like aerodynamic shaping to manage the shockwave more efficiently. Both add complexity and mass to the projectile, which pushes the required muzzle energy higher, which makes the power supply problem worse. The challenges feed into each other, which is part of why the engineering progress has been slow despite the physics being sound.