The first effective mine detector

Land mines have existed in some form for more than a thousand years. You would think that by now a simple and safe way to find and remove the device would have been developed. But that’s not the case. In fact, until World War II, the most common way to find explosives was by poking them into the ground with a pointed stick or bayonet. The hockey puck-sized device was buried about 15 centimeters underground. If someone stepped on the ground on or near the mine, their weight would trigger a pressure sensor, causing the device to explode. So mine removal work was as dangerous as unknowingly walking through a minefield.

During World War II, land mines were widely used by both Axis and Allied forces and were responsible for the deaths of 375,000 soldiers, according to the Warfare History Network.

Józef Stanislaw Kosacki, a Polish communications officer who escaped to England in 1941, developed the first portable device that could effectively detect land mines without accidentally triggering them. This method proved to be twice as fast as previous mine detection methods and soon became widely used by Britain and its allies.

The engineer behind the portable mine detector

Before inventing the mine detector, Kosacki worked as an engineer, developing explosive detection tools for the Polish military.

After receiving his bachelor’s degree in electrical engineering from the Warsaw University of Technology in 1933, Kosacki completed one year of mandatory service in the army. He then joined the National Telecommunications Institute in Warsaw as a manager. Then, as now, the agency led the country’s communications and information technology R&D. In 1937, Kosacki was commissioned by the Polish Ministry of Defense to develop a machine that could detect unexploded ordnance and artillery shells. He completed the machine, but it was never used in the field.

Polish engineer Józef Kosacki’s portable mine detector saved the lives of thousands of soldiers in World War II. military history office

When Germany invaded Poland in September 1939, Kossacki returned to active duty. Due to his background in electrical engineering, he was assigned to the special communications department responsible for the maintenance of the Warszawa II radio station. However, that mission lasted only until the radio tower was destroyed by the Germans a month after the invasion.

While Warsaw was under German occupation, Kossacki and his unit were arrested and transported to a concentration camp in Hungary. In December 1939, he escaped and eventually made his way to England. There he joined other Polish soldiers of the Polish I Corps stationed at St. Andrews, Scotland. He taught soldiers how to use wireless telegraphy to send messages in Morse code.

Then tragedy struck.

Engineering ingenuity inspired by tragedy

The invention of the portable mine detector came about after a terrible accident on the beaches of Dundee, Scotland. In 1940, fearing a German invasion, the British laid thousands of mines along the coast. But they did not inform their allies. Soldiers of the Polish 10th Armored Brigade, who were regularly patrolling the beach, were killed or injured in landmine explosions.

This incident prompted the British military to launch a competition to develop an effective mine detector. Each participant had to pass a simple test. The idea was to detect a few coins scattered on the beach.

Kosacki and his assistants spent three months improving Kosacki’s early grenade detector. During the competition, their new detector found every coin, outperforming the other six devices that entered.

As befits technology developed under wartime security, there is some ambiguity about the exact circuitry of the detector, but our best understanding is as follows. The tool consisted of a bamboo stick with an oval wooden panel holding two coils at one end. According to a 2015 article, one received Aerospace research in Bulgaria. The soldier held the detector by a pole and passed a wooden panel over the ground. A wooden backpack containing a battery unit, an acoustic frequency oscillator, and an amplifier. The transmitting coil is connected to an oscillator that generates a current at acoustic frequencies, Mike Croll writes in his book. history of landmines. The receiving coil was connected to an amplifier, which was then connected to a pair of headphones.

The detector weighed less than 14 kg and worked much like the metal detectors we use on beaches today. Michał Bojara/National Museum of Technology in Warsaw

When the panel gets close to a metal object, the inductive balance between the two coils is broken. Through an amplifier, the receiving coil sent an audio signal to the headphones, alerting the soldier to potential mines. According to Kroll, the device weighed only 14 kg and could be operated by a single soldier.

Kosacki did not patent his technology, but instead gave the British military access to the blueprints of the device. The only recognition he received at the time was a letter from King George VI thanking him for his service.

The detectors were quickly built and shipped to North Africa, where German commander Erwin Rommel ordered his troops to build a defensive network of mines and barbed wire called the Devil’s Gardens. The minefield stretches from the Mediterranean in northern Egypt to the Katara Lowlands in western Egypt and contains approximately 16 million mines over 2,900 square kilometers.

Kosacki’s detector was first used during the Second Battle of El Alamein in Egypt in October and November 1942. The British military used this device to find explosives in minefields. A Scorpion tank followed the soldiers. As the tank advanced, heavy chains mounted on the front stirred the ground and set off mines. Kosacki’s mine detector doubled the rate at which these heavy mines could be cleared, from 100 to 200 square meters per hour. By the end of the war, his invention had saved thousands of lives.

Kosacki’s mine detector was first used in Egypt to help clear large minefields constructed by the Germans. The basic technology remained in use until 1991.National Army Museum

The basic design, with minor modifications, continued to be used in Canada, the United Kingdom, and the United States until the end of the First Gulf War in 1991. By then, engineers had developed more sensitive portable detectors as well as remote-controlled mines. -Clearing system.

Kosacki was not publicly recognized for his work until after World War II to prevent reprisals against his family in German-occupied Poland. Kosacki returned to Poland after the war and began teaching electrical engineering at the National Center for Nuclear Research in Otwock-Świerk. He was also a professor at what is now the Military Technical University in Warsaw. He died in 1990. The prototype of the Kosacki detector shown above is stored in the Museum of the Institute of Military Engineering and Technology in Wrocław, Poland.

Landmines remain a global problem

Mine detection is not yet perfect, and explosive devices remain a major problem worldwide. According to UNICEF, on average, one person is killed or injured by landmines and other explosives every hour. Today, it is estimated that 60 countries are still contaminated with landmines and unexploded ordnance.

Portable mine detectors continue to be used, but drones have become another method of detection. For example, in Ukraine, several humanitarian non-profit organizations have used this program, including Norwegian People’s Aid and HALO Trust.

Nonprofit APOPO is taking a different approach. Training rats to smell explosives. According to the organization, APOPO HeroRAT only detects the scent of explosives and ignores scrap metal. A single HeroRAT can search an area the size of a tennis court in 30 minutes, instead of the four days it takes a human to search.

part of continuing series Explore historical artifacts that embrace the infinite potential of technology.

An abstract of this article will appear in the January 2025 print edition as “The first mine detector that actually worked.”