Behind the Reactive Materials Revolution

In 2005, U.S. Navy scientists William Holt and Wills Mock Jr. were presented with a Navy Distinguished Achievement in Science (DASA) award. It was the first time the award had been given for 14 years – for 'extraordinary and significant' achievements in developing materials that will give rise to 'an entirely new class of weapons'. You won't have heard much about these new weapons… until now. They will change everything from bunker busters hitting targets deep underground to weapons to swat satellites far overhead -- and everything in between.

Few people are willing to talk about Reactive Materials, but Danger Room will be bringing you the whole story on the Reactive Revolution and how it is changing warfare. This is a new technology which will transform everything from bombs, missiles and bullets to mines and torpedoes, as well as creating completely new weapons that are unlike anything we have today.

The DASA award was given by Rear Admiral Archer Macy, who commented:

“The citation for Drs. Holt and Mock [pictured] talks about what they did in general terms, because a lot about what they really did we can’t talk about".

Holt and Mock's work goes back to 1971, when they first started to explore the physics of high-velocity impacts. In particular, they discovered how certain types of material may start to release energy on impact. Such materials, which consist of two or more components, are inert under normal conditions and insensitive to normal methods of detonation. But the extreme forces of impact – and in particular the rapid deformation they produce -- will cause the components to react together and release more energy than high explosive.

There are several different types of reactive material, including metal-polymer, intermetallic compounds and thermites. (This is not quite your old-fashioned thermite – it releases its energy in a fraction of a second, very much like an explosive, rather than burning over a prolonged period). Mock and Holt were recognised for their work on polymer/metal combinations such as PTFE (aka Teflon) and aluminum. The effect of thereactive material on a target was dramatic – "You don't need statistics to show the difference," Holt says in the Office of Naval Research's in-house journal.

These materials can be engineered to give thermal or blast effects, or a combination:

In both classes of reactions, the white-hot products remain largely solid or perhaps become molten, but there is no great output of gaseous products, which means the materials are nonexplosive.

Energy output is comparable to that of a high explosive, but in a different form—more purely thermal, with little blast. A roughly similar amount of additional energy is released when the products of the first reaction (such as carbon liberated from the PTFE, or the individual metals in a bimetallic) burn in air. If the products are dispersed in air before this secondary reaction, it will be accompanied by a large blast pressure.

The initial work in 1971 involved building a high-velocity gas gun to do the testing. Right from the start the pair showed their ingenuity in the face of difficulties. Lacking the funding to buy a gas gun off the shelf, Mock and Holt built theirs from scratch.

…they scavenged parts from scrap heaps. The gun’s frame came from a piece of steel-I beam lying in a field. The breach was made from a three-inch gun barrel found on a range. And the gun was covered by an old water trough.

Their efforts went late into nights, and they first tested the gun on Saturday night, December 17, 1971.

Decades later, the first weapons using reactive materials are now arriving. And they will be followed by many more as the Reactive Revolution gets under way.