Atomic Applications:

The Railgun and Materials Engineer

By Benjamin Cheng

The Railgun: A New Class of Weapon

Guns are a technology that can be traced back to the 12th century in China. Since then, there have been numerous advances, with growing size and power, spherical bullets evolving into today's cone-like bullet, and barrels bored with twists to impart an angular momentum upon the bullet, just to name a few. However, all of these guns use explosives to create expanding gas in order to propel the projectile. Instead of using explosives, railguns use the electromagnetic force to propel a projectile.

By using the electromagnetic force, the gun no longer depends on the rate of gas expansion, and the limits thereof. Modern explosive-powered weapons can only reach a muzzle velocity of about 2 km/s, but railguns can easily reach more than 3 km/s. This speed also results in much superior range when compared to traditional weapons. Additionally, explosives do not have to be transported for use, making the railgun much safer for personnel.

The Electromagnetic Force

The theory behind the railgun is quite simple, however solving the actual math behind it is very difficult, and has only been made possible within the past 20 years.

The railgun consists of two powered rails and the armature (the projectile). The armature completes the circuit of the two rails. The current creates a magnetic field, forming concentric circles around the wire, in a direction counter-clockwise to the direction of the current. This can be modelled with a right-hand rule: if your thumb is pointing in the direction of the current, the direction your fingers curl is the direction of the magnetic field. The Lorentz force is a force that acts on a charge moving, such as an electron in a wire, in a magnetic field. The Lorentz force acts perpendicular to the magnetic field and velocity vectors, and the magnitude of which is determined by the cross-product of those two vectors. An easy way to figure out the direction of the force is to use the right-hand rule: if your middle finger is the field vector, and your index figure is the direction of current, then your thumb is the direction of the force. The Lorentz force for the armature is therefore forwards, out of the barrel of the gun.

To increase the Lorentz force, either the current or the magnetic field strength must be increased. This is why a single shot of a railgun requires around 33MJ of energy. In order to provide this power in an instant, capacitors are usually used, as a capacitor can discharge its stored energy in a short pulse. The magnetic field strength can also be augmented with external magnets and can vary on the materials used in the railgun.

Challenges in Materials

One of the hardest parts of designing the railgun is determining what materials should be used. Since current US Navy railgun designs are still classified, the actual materials used in their prototype are unknown.

As discussed, for a large force there must be a large amount of current, which means both the armature and the rails must be made of conductive materials. However, with such large amounts of current, many metals would melt and weld the armature to the rails. Even the heat created by the armature moving creates a tremedous amounts of heat, meaning that the rails need to be resistant to damage caused by heat.

As well, the Lorentz force acting on the armature also acts on the rails, pushing them apart. This means that the rails must be able to withstand this force without bending or breaking.


Graphite is a material being used in railgun armatures. The large number of covalent bonds in the graphite means that it requires a large amount of energy to break all the bonds, making it hard to melt. Because each carbon in the graphite is only bonded to three carbons, there are many delocalized electrons within each layer of graphite, making it a only good conductor within the layer. Although the sheets themselves are very strong, the bonding between the sheets is very week (London Dispersion Forces) This means as the armature travels, the graphite's weakly bonded sheets leaves a coating of graphite on the rails. Not only that, the fact that they the layers are only conductive within the layer, means that during this process, electricity through the armature is not constant.

To solve this problem, graphite can be intercalated, meaning an ion layer is inserted between the layers of graphite (graphene). With this setup, the ion layer ensures conductivity throughout the entire compound. The properties of these compounds are generally similar to that of graphite compounds, including a relatively high melting point. This makes it a good material for the high conductivity, high temperature requirements in a railgun.


As discussed, the strength of the magnetic field can be augmented with permanent magnets, decreasing the need for so much electric current. The table shows the many different alloys, with the magnetic field strength (Br), and the Curie temperature (TC). The Curie temperature is the temperature at which the magnets lose their magnetic properties. Since these magnets are not directly in the chamber of the railgun, the magnets can be more easily cooled to below the Curie temperature.

These alloys are generally a ferromagnetic metal combined with a paramagnetic metal. Neodymium ([Xe] 6s2 6s2) is a common paramagnetic metal used in these magnets, as it has 4 unparied electrons, which when aligned with an external magnetic field can generate a very strong magnetic field. To provide an external magnetic field, iron is usually added in an alloy to create a neodymium magnet.

Materials Engineer

Materials engineers research and improve on what things are made of, creating more sustainable, efficient and reliable materials. Innovations from materials engineers include carbon nanotubes, a material that is very strong, while being very light, and conductive to both heat and electricity.

Materials engineers usually spend their time researching, with experiments in the lab and modeling done on the computer. They usually specialize in one of metals, ceramics, plastics, semiconductors or composites. Most of their time are spent in labs, and occasionally offices in 40 to 50-hour work weeks. Most of the safety risks come from the lab environment, where engineers are exposed to many dangerous chemicals. However, with careful safety procedures, the job can be very safe.

To get a job as a materials engineer, you need at least a bachelor's degree, which takes 4 years. More advanced research jobs may require a master's or PhD, requiring either 2 or 4 extra years on top of the bachelor's. After a few years in the field, you can get a professional engineer license. As well, a master's in business administration can also help advance into managing engineers. Out of university, a starting salary will be around $50 000 a year, which will slowly progress up to $160 000 a year with experience. With a MBA or a PEng license, it is possible to make over $160 000 a year, in a supervisor or management position.

The End.