Take a copper coil, mount it on a shaft and connect both ends to brushes sliding on ring contacts connected to an ammeter. Spin up the coil using a high speed electric motor, then abruptly stop it. At that exact moment, the ammeter will record a short but perfectly detectable pulse of electric current. Where does this current come from, given that there is nothing in this setup that produces an electromotive force?

The answer is that it comes from electron inertia. In a metal, electrons can be figuratively imagined to form an electron liquid sloshing around between the atomic nuclei of the metal’s crystal lattice. When the coil is spun up, they gain speed together with the protons and the neutrons forming the atomic nuclei. Unlike the nuclei, they are not bound to the crystal lattice and can travel some distance by inertia after the object is abruptly stopped. (For those who forgot, inertia is mass times velocity: p=mv.) Since electrons are (negatively) charged, they generate an electric current when they move. This is what the ammeter registers when the rotation of the coil is stopped.

It doesn’t take much electron motion to produce a large effect. At an electric current density of 10 amperes per square millimeter, the electrons drift through a copper wire at just 1 millimeter per second, but this is sufficient to melt the wire. Now imagine the effect if the speed is not 1 millimeter but 3 kilometers per second (or Mach 10), which is 3000000 times faster, as is the case when the warhead of an Oreshnik missile slams into the ground. Hard to imagine?

Here is a hint: the metal will explode.

But that’s not all.

The stability of a metal crystal lattice is preserved by the equilibrium of the Coulomb forces between the positive ions of the atomic nuclei and the surrounding negatively charged “electron liquid” of free electrons. Now imagine that all the free electrons have escaped. What happens to the atomic nuclei of the metal once the force holding them within the crystal structure disappears is that they all begin to repel each other and an explosion occurs.

Around a century ago it was noticed that when a fast-flying lead bullet or shell hits steel armor, it releases an amount of heat many times greater than the kinetic energy of the projectile (which is half the mass times its velocity squared, E_k=1/2 mv^2) — enough heat to burn a hole right through a steel plate. The reason for this anomaly is the same: electron inertia.

The binding energy in the crystal lattice of metals is approximately twice as large as that released during the explosive oxidation of TNT. At first glance, the explosion should not be much larger than that produced by a conventional explosive — about twice as large. The difference is that the time it takes to release this energy is hundreds of times shorter than during the chemical oxidation reaction in TNT and the energy from it is much more concentrated. Because of this, the destructive power of a Coulomb explosion can be 1000 times greater than that of a conventional explosive. Of course, this is not a nuclear explosion: no atomic nuclei are in any way damaged during this experiment. But it is comparable in its effects, which are much greater than what can be achieved using TNT.

For a bit of perspective, consider that 1 kg of uranium-235 can in theory (if every single atom of it undergoes nuclear fission) result in an explosion equivalent to 20 million kg of TNT. In reality, uranium is never enriched to 100% U-235 (anything above 90% is considered weapons-grade) and only a few percent of the U-235 have time to participate in a nuclear chain reaction before the whole contraption blows up. More realistically, a 1 kg nuclear charge is equivalent to about a million kg of TNT (or 1 kiloton). Meanwhile, 1 kg of metal in a Coulomb explosion will release energy equivalent to about a thousand kg of TNT (or 1 tonne). Nevertheless, these are still huge numbers.

And now we can address the question of what Oreshnik most likely is. Here is what has been publicly announced about it:

Warhead temperature: 4000ºC

Speed: Mach 10 (2.5–3 km/s)

Mass of warhead: ~1.5 tonnes

Perusing Dmitry Mendeleev’s Periodic Table of Elements we find just one candidate for warhead metal: tungsten. It melts at 3422ºC and boils at 5555ºC. Taking the mass of the warhead (which, we assume for the sake of simplicity, consists entirely of a single shaped piece of tungsten) at 1,500 kg, it produces the equivalent of 1,500,000 kg of TNT or 1,5 kilotons — a respectable amount for a small tactical nuke.

But there is more: unlike a nuke, which explodes prior to impact (or it smashes into little bits and just makes a big mess) and expends only some of its energy on producing a destructive shockwave while much of the rest radiates out as heat, heating the atmosphere, the stratosphere and outer space, the tungsten warhead penetrates the ground to a maximum depth given its momentum (E_k = 1,613 kg of TNT) and only then does it explode, producing the equivalent of a very short highly localized and intense earthquake. The effect at ground zero is that the ground and anything on it or in it is turned to fine dust. This is what was reported to have happened at Yuzhmash factory near Dniepropetrovsk, which the Russians had used as an Oreshnik test range.

Thus, Oreshnik is not a nuclear device, since no atomic nuclei are in any way damaged by its operation. It is, however, an atomic device because the basis of its explosive power is not chemistry (oxidation of TNT or some other explosive) but the atomic physics of a Coulomb explosion.

While this part of the Oreshnik story can be puzzled out based on the available evidence, other parts of it remain enigmatic. Specifically, it remains a well guarded secret how Oreshnik can precisely maneuver its warheads as they approach the target. Another well guarded secret is how the warhead manages to penetrate the atmosphere at Mach 10 without burning up. Nobody else has anything even remotely similar to these two technological advances and the Russian military is unlikely to divulge them any time soon — at least not before coming up with an even more awesome weapon.