There is a secret to designing an explosive device that penetrates heavy armor. More than a hundred years ago designers discovered a munitions device is more powerful when the explosive material is pressed into a concave shape on the open end of the casing, creating a cavity. When detonated, at just the right distance from the target, the force of a shaped charge can penetrate the thickest armor. When the cavity is covered by a copper or glass liner, the force from the explosive is much stronger. While in use for decades, the properties of this phenomenon were not fully understood. Pioneering work from the world-renowned Lawrence Livermore National Laboratory now allows the properties of the supersonic jet that escapes from lined shaped charges upon detonation to be accurately modeled. Detonation forces the liner to collapse inwardly with tremendous force, projecting a tightly focused jet of liner material with enormous energy.
These specialized explosives have many applications, including precision demolition of buildings and a host of military applications such as safely destroying obsolete ordinance and buried land mines. Millions of shaped charges are detonated each year to complete and improve Oil and Gas wells. Guns with horizontal arrays of charges called perforators are dropped into well shafts lined with concrete and metal casings at precise depths to pierce the shaft and create horizontal tunnels and fractures to initiate flow from surrounding deposits.
The design of shaped charge liners has evolved over decades. Engineers used years of empirical tests to determine the exact shape and size of the liner and the most effective materials to use for the liner for various applications. The ultimate goal is to increase the speed of the pressure jet’s tip and its effective length while controlling the distribution of mass at the jet’s tip. Concave shapes have morphed into precisely formed shapes such as tapered inverted cones. Finely powdered metals such as tungsten have replaced copper. The pressure jet from modern shaped charges can penetrate more than a foot of hardened steel or tunnel several feet into rock. While effective, high-performance charge liners are difficult to manufacture and are expensive.
Glass also makes an excellent and inexpensive charge liner. It has an amorphous molecular structure that allows liners to collapse uniformly, creating long, coherent jets with great penetrating power. Wine and Champagne bottles have often been used to create improvised explosive devices because of the concave bottom of the bottle and the excellent ductility of molten glass. However, silica lacks the mass of metal, limiting its effectiveness.
Paul Wilkins from Lawrence Livermore National Laboratories is exploring the effectiveness of the latest Liquidmetal alloys as a charge liner. Liquidmetal has the mass of metal with the amorphous structure of glass that can be precision injection-molded. Providing the best properties of metal and glass, Liquidmetal offers the promise of mass produced, highly effective liners at a reasonable cost.
The largest market for shaped charges is Oil and Gas, replacing fragile and expensive powdered metal liners for millions of shaped charges detonated each year in perforating guns. These guns are the most effective tools available to increase the flow of established wells and are used in fracking. Liquidmetal’s promise of increased performance is highly valuable: adding just 2 inches to the length of a perforating tunnel can dramatically increase the volume of oil flowing into the well.
But there is more! Because of its amorphous structure, Liquidmetal either shatters into fine particles or liquefies upon detonation, forming the powerful penetrating jet that tunnels into bedrock. As a result, Liquidmetal does not leave a metal slug in the tunnel that impedes oil flow. This slug is a property of all other solid metal liners. Liquidmetal perforators are extremely rugged, and will not crack, shrink or expand while stored or during handling. They are also manufactured to tolerances within .002 inches in every dimension, with unmatched consistency from one part to the next.
Liquidmetal Technologies are testing specialized high-density alloys that will likely boost performance even further. Oil and Gas well completions may prove to be an ideal application for Liquidmetal, harnessing its pyrophoric and reactive potential to dramatically improve production.