The Munroe Effect

Introduction

The Munroe effect is penetration of an explosive into a surface that is concrete or metallic in nature. The penetration into such a surface is affected by the design of the explosive material, whereby it has a hollow part at the forward end and a shape that resembles that of a cone or a hemisphere. Charles Munroe who was a great chemist and inventor discovered this effect. It is of great use in the modern world, and it is utilized in the functioning of shaped charges while focusing the energy from explosives. The shaped charges in which the Munroe effect is applied are useful in the modern world; also, it carries out various roles. This paper explicates various experiences that led to the discovery of the Munroe effect and its benefits in the modern world.

History of the Discovery of the Munroe Effect

According to the Global Security Organization (2012), the Munroe effect, which is applied in the design of explosives, was discovered in 1885. Charles Edward discovered that a highly explosive gadget with a cavity in the front part could leave an indent mark once it was directed towards a particular target. Mining engineers had been reported to utilize this concept before its discovery by Charles Munroe. Mining engineers preferred to use the blasting charge that was conical-shaped in an attempt to increase the resulting explosive effect on the mines. Using this concept, mining engineers could save on the amount of gunpowder used in their mining activities, as it was the only available explosive at that time. Later after its discovery by Charles who was a great chemist, Von Neumann rediscovered it in the year 1911. It is worth noting that until that time, no significant applications of the Munroe effect had been tried. After World War I, shaped charges were developed; they were majorly applied in the penetration of equipment in armors and tanks.

The Global Security Organization (2012) states that shaped charges were procedurally developed in four generations. The first generation of these shaped charges consisted of a charge that was cylindrical in shape, which would be laid flat against armor, and on being propelled to a target, it would make a hole on it. The second generation of shaped charges appeared due to a modification in the shape of the first generation charges. In this generation, a cone shape was used as it would channel further the force from the explosive, thus, increasing the chances of penetrating into the target object. The first and second generations are not in use today, but they laid the foundation for the best design shapes to adopt for future shaped charges. In the third generation, the charges were hollow, and an example in this group is a jet creating charge. The fourth generation was an advanced level of the third generation and was a projectile creating charge. All these generations of shaped charges utilized the concept of the Munroe effect, which had been discovered earlier.

Franz Von Baader was the first man to demonstrate the Munroe effect in 1972. Using a hollow-shaped charge, he focused the energy of the explosive on a target and observed the penetration effect on the target. Baader’s experiments were not that effective because he used black powder, which was not a reliable detonator. Von Forester carried out experiments that produced the expected results of the Munroe effect later in 1883, using a reliable detonator invented by Alfred Nobel in the year 1867. Walters (2008) affirms that Bloem of Dusserdorf developed the first shaped charge. A shell would be used for detonating caps and it took a hemispherical shape in order to boost efficiency. Munroe later carried various experiments and popularized his effect, which he had addressed in various publications.

In his famous experiments, Munroe discovered that explosives could engrave words on an object. During the experiment that was carried out to illustrate explosive engraving, he had an explosive charge with the initials USN that stood for the United States Navy opposite the point of initiation of the charge. On detonation of the charge with the target being a steel plate, the words were clearly inscribed on this surface. Later, Von Foerster carried out similar experiments, hence emphasizing them. In other experiments carried out by Munroe, he discovered that smaller amounts of explosives could produce more penetration in a steel plate when a cavity was formed in the explosive cylinder. This increased penetration resulted from the hollow cavity, focusing the products of detonation on the steel plate.

Munroe may be credited for successful development of the first line-shaped charge if Bloem is discounted. His device was made up of a tin can with dynamite sticks surrounding the can and some of them located on top of it. The open part of the tin pointed downwards, and on being initiated, it was able to make a hole on the surface of steel safely. It is vital to note that the tin played the role of a liner. Walters (2008) affirms that Germans made the earliest reference to the application of the Munroe effect between 1911 and 1912, whereby patents were made by WASAG. In their patents, they demonstrated both effects of charges that were lined and unlined. M. Neumann also demonstrated the unlined cavity effect by carrying out several experiments. The results of his experiment were that a greater penetration would be observed in a steel plate from a cylinder of explosives with a hollow and conical cavity compared to a solid cylinder of explosives.

Walters (2008) confirmed that an experiment was carried out in 1941 in Germany with the aim of illustrating the effectiveness of the Munroe effect. This experiment involved two charges that had cavities, with one being hollow-shaped and the other lined. The cavity for the hollow charge had the shape of a hemisphere and an extension at its base that was cylindrical and equal to one-half the diameter of the cavity. For the lined charge, the liner material was made of iron and the contour, which was an explosive, had the same geometry with the cavity. The thickness of the base of the liner material was 0.15 times the diameter of its cavity. The two charges were detonated from a distance to an armor plate that was made of steel. The content of explosives of the two charges was each made up of a 50% TNT and 50% cyclonite concentration. When both were from zero standoffs, the unlined charge, which was hollow, had a penetration of 0.4 D, while the lined cavity charge had 0.7 D. The lined cavity then was observed to have a penetration of 1.2 for standoffs between 0.5 and 1.5 D. D represented the inside diameter of the charge that was lined in this case. This observation indicated that there was an increased penetration when moving from hollow to lined cavity charges and making a non-zero distance standoff.

In the Soviet Union, efforts to continue with the research of the Munroe effect were made by Sukharevski. He was the first person in the country to investigate the Munroe effect between 1925 and 1926. In the United Kingdom, various people including Tuck, Mott, Pack, and Ubbelohde continued with experimenting on the Munroe effect. In the United States, efforts of further research and application of the Munroe effect were made by various people, with the Watson group and Wood being significant contributors. Walters (2008) asserts that the Watson group came up with a percussion fuse, which was patented in the year 1925. This fuse was made of a booster charger that resembled a parabola and had a cavity that was hemispherical with a metal lining on it. The cavity increased the effect that would be made from the booster charger once initiated. Findings of the fuse and its functional ability were further proven by the Munroe effect. The results revealed that the booster charger with a cavity required about one-sixth of the explosive to produce the desired effect, when compared with an unlined booster charger. The booster charger with a cavity was also reported to function effectively on a considerable level gap of air as an extra advantage.

The Global Security Organization (2012) reiterates that in 1965, efforts of a Russian scientist led to the development of a new gadget that applied the Munroe effect. The scientist suggested that the charge could adapt the concept of Munroe and would be used in the acceleration of shock waves. The device that was developed is currently called the Voitenko compressor. This device was used in separating test gas from a shaped charge. It worked according to the theory that on detonating a shaped charge, most of the energy produced would be directed towards a target, which would push the test gas that would be ahead of it.

The discovery of this important device was later followed by the United States Army Ballistic Research Laboratory’s great contributions to the development of shaped charges. Ballistic Research Laboratory scientists studied keenly the mechanics that are involved in penetration of a high-velocity jet of metal formed by a warhead. This study led to the design of light and inexpensive weapons that would be used in defending against tanks. These scientists also contributed through applications of linear technology, which helped increase jet speed and provided an opportunity for enhancing lethalness in the weapon systems.

Behrmann & Khong (2012) assert that the major discoverers of the shape of the modern charge were Franz Thomanek from Germany and Henry Mohaupt from the United States. These two individuals worked independently to perfect the concept of the hollow charge, which led to the development of a charger that was lined and had a cavity. Henry Mohaupt was a great chemical engineer who spent his life developing an anti-tank weapon that could be used by infantry soldiers during World War II. His efforts bore fruit and led to the discovery of a charge that was line-shaped. During World War II, this chemical engineer moved from Zurich, where he had established a laboratory for his research, to the United States. In 1940, as affirmed by the Global Security Organization (2012), Henry continued with his anti-tank device, which was also referred to as the bazooka project. In 1945, Ramsey Armstrong pursued this bazooka project by founding the Well Explosives Company, which was located in Texas. Ramsey established contacts with Henry Mohaupt, and in 1946, Henry moved to Fort Worth to work together with Ramsey in an attempt of discovering more the application of the Munroe effect.

Variants of Modern Day Shaped Charges

Modern shaped charges are of various types. One such type is a linear-shaped charge that is designed with a V-shaped lining along its length. Walters (2008) affirms that the lining is filled with explosives along its length and is usually detonated at a point that is above the lining apex. The explosively formed penetrator is another type and it is used in projecting and deforming a dish onto a projectile. Another type is a tandem warhead; in most cases, it is used in the design of missiles. The last known type of these shaped charges is the Voitenko compressor, and it is used in accelerating shock waves. Some modifications have also been made on this device to form a compressor that uses solid fuel instead of a gas mixture in the steel compression chamber.

Benefits of the Munroe Effect

The Munroe effect plays a great role in the oil and gas industries. The concept has been adopted in the design of charges that are used in the drilling of underground wells. With the use of the shaped charges, the penetration into thick layers of a rock in the drilling of oil and gaseous wells is much easier. The wells are well cemented with a metallic case to maintain the significance of the well. Shaped charges are then attached to a strip in the metal casing that covers the well; then, they are initiated to produce the penetration effect in the underground hydrocarbon zone. During the initiation, shock waves are produced, which propel and deform the shaped charge housing at a high velocity inside the empty space of the well. This propelled jet is in a position of cutting the metallic casing based on the shape of the space, which is void, and the standoff distance to the target wall. On penetration, hydrocarbons enter the metallic casing on the perforations made and are transmitted to the surface.

The shaped charges are more effective in the drilling of these oil and gaseous wells than bulk cutters. This is because bulk cutters use the ripping effect to make penetrations, while the shaped charges utilize the Munroe effect, which makes them more reliable as they make penetrations by jet cutting on the intended target. According to Behrmann and Khong, linear-shaped charges are one of the types of charges used in oil perforation and are designed in such a manner that they do have a V-shaped void along its whole length so as to cut linearly on the target.

Another type used is conical-shaped charges, and these do have their cavity designed resembling the shape of a cone; they are majorly intended to make round holes and penetrate deeper into targets. The major application of these conical-shaped charges in the oil industry lies majorly in the making of perforating guns and extracting hydrocarbons by penetrating into the well, casing and the surrounding strata when detonated. In the casing of this charge, steel instead of zinc is used to reduce the damage that may be caused to the components of the shaped charges on detonation; this helps in reducing the associated cost of completion fluids for the shaped charges. The shaped charges in the oil industry are deployed using a perforating system that is tube-conveyed to increase the productivity of the Munroe effect in the horizontal intervals.

The concept of the Munroe effect has been used in the designing of clearing devices. One such device is a copper cone. When a charge is detonated, this copper cone produces a jet, which does form holes on a target. Thus, it may be used in the deflagration of ammunition that has a steel case without causing any possible risk of disturbance on a target before the ammunition is fired. Another similar device is an aluminum projectile that is used as an alternative in de-armoring. This projectile uses steel barrels and is considered as a cost-effective method of disposal. This projectile is very effective as a method of disposal, since it generates energy that blows fuses and bomb pistols, which creates a jam in their operation mechanisms. Another form of projectile that is utilized in disposal is copper explosively formed projectile. It is designed in the shape of a wide-angle copper cone and is used in the penetration of robust targets, which may be far from the formed jet. Due to its reliability in various ranges, it is used both as a disruptor and de-armor gadget.

This shaped charge is built taking into consideration the Munroe effect and is used in penetrating very thick armor. This charge is hollow-shaped and is comprised of a metallic outer casing, an explosive, and a metallic cone. On detonation of the explosive, a metal jet from the cone is formed which is propelled at a very high velocity and can penetrate a thick armor target. This concept is applied in designs of warheads, whereby they provide an excellent opportunity for defeating enemies by destroying their armors and weapons. In the United States, such warheads have been designed and used as part of the country’s modern war equipment. Such a warhead is the United States’ anti-armor missile designed to possess two shaped charges. The United States military army has also incorporated the use of high explosive anti-tank armor warheads in the designing of rockets, bombs, and rifle propelled grenades among other weapons.

Iraq insurgents have been reported to have utilized heavily the Munroe effect in the design of their war equipment. Various groups used improvised explosive devices that utilized this concept in World War II. Mujahiden was one of such groups, which used the devices to fight the Soviets in Afghanistan. As stated in the article “Improvised explosive devices” (2012), the improvised explosive devices were also heavily attributed to numerous deaths of American soldiers in Iraq during the Sunni anti-American insurgency. Later, during the sectarian strife in 2007, Iranian soldiers were linked to the aiding of Shiite militants in the making of deadly shaped charges to attack Americans. Due to this, the Pentagon considered this matter and sent numerous aids to Afghanistan to stop this threat. Drones, robots, and dogs were used to combat and stop the development of these deadly weapons.

The shaped charges have also been of major use in the formation and cutting of metals. Without doubt, metals play an instrumental role in the development of different aspects in people’s everyday life. The penetration effect on detonation of a charge is used to cut metals such as steel. In other instances, shaped charges are utilized in the formation of metals, which are vital in human life. Shaped charges have also played a great role in the propulsion of the fourth generation of nuclear weapons. In an attempt of reducing the lethal effects of propulsion of a nuclear weapon, shaped charges have been considered to be of great use, as they continue contributing positively to different areas of application. Gsponer (2006) asserts that the use of shaped charges has resulted in the extension of the range of penetration of the nuclear weapon, since it is initiated in an enhanced manner that does not destroy some delicate components of the nuclear weapon package.

As a result, the Munroe effect is of great use in today’s modern world, as the concept has had various useful applications in diverse fields. The success of these fields can be significantly attributed to Charles Munroe who made great strides in the discovery of the Munroe effect.