The beginning of the nuclear age

August 6 marked the 80th anniversary of the first use of nuclear weapons in combat. On that day in 1945, an atomic bomb was dropped on the Japanese city of Hiroshima from an American Boeing B-29 Superfortress aircraft.

The scientific research that formed the basis for the creation of this weapon had been conducted in the United States since the late 1930s. From 1942, a large-scale national program known as the Manhattan Project was in operation, aimed at the direct development of usable atomic bombs. It was headed by General Leslie Groves, and Robert Oppenheimer became the scientific director. The main scientific center was located in the remote town of Los Alamos (New Mexico). In total, Manhattan Project facilities were built in dozens of locations across the United States, and nearly 130,000 people were involved in the work. In effect, the US created a new industry with its own science and industry.

Two types of bombs were developed in Los Alamos: implosion and artillery. In the first version, a 6-kg plutonium core was compressed to supercritical mass by implosion—a focused explosion. This was achieved using specially arranged charges of conventional explosives. Overall, the design of the bomb, called “Fat Man,” was complex, which significantly increased the risk of technical failure during use. The second bomb was called “Little Boy” and had a much simpler design—supercritical mass was achieved by firing a uranium projectile at a target made of the same material. The bomb was considered much more reliable than “Fat Man,” but it required 64 kg of very expensive and scarce highly enriched uranium-235.

On July 16, 1945, the world's first nuclear test explosion was conducted at the White Sands Proving Ground (also in New Mexico). For this, a device similar to the warhead of the Fat Man bomb was used. The explosion had a yield of approximately 21 kilotons in TNT equivalent.

After a series of amphibious operations to capture islands in the Pacific Ocean, the American military was struck by the fierce resistance of the Japanese and their high casualties. The campaign to occupy the main territory of the Land of the Rising Sun threatened to drag on for at least a year and, according to some estimates, could cost up to 2 million American lives. Proponents of the use of the new weapon insisted that it would make this avoidable. There were other arguments as well. For example, members of the committee responsible for selecting targets for atomic bombing noted in their conclusions that there were two important psychological factors: achieving maximum psychological effect against Japan and “ensuring sufficient spectacle for the first use so that the importance of the weapon would be recognized internationally.”

The 509th Composite Group was created for atomic bombing, and Colonel Paul Tibbets was put in charge of it. He personally led the bomber crew on the first mission. Just before takeoff, the commander ordered the name “Enola Gay” to be written on the underside of the nose of the aircraft in honor of his mother.

Before dawn on August 6, this B-29 took off from North Field Airfield on the Pacific island of Tinian. Enola Gay flew to Japan accompanied by two other B-29s, whose crews were tasked with filming the explosion and conducting observations using special equipment. The planes flew at an altitude of almost 9,500 meters, encountered no resistance, and reached Hiroshima without hindrance. At 8:15 a.m. local time, the Little Boy bomb was dropped. It exploded at an altitude of 530 meters. Its power was estimated at approximately 13-15 kilotons. Moreover, the efficiency coefficient turned out to be extremely low; scientists believed that less than 2% of the uranium reacted. But the consequences were terrible. According to Japanese data, the explosion destroyed 69% of Hiroshima's buildings. It was impossible to determine the exact number of victims. Initial estimates ranged from 66,000 to 69,000 deaths. According to estimates from the 1970s, this number reached 140,000, including those who died within six months from injuries and radiation exposure. According to current data, the number of victims could exceed 175,000.

Japan was shocked but did not surrender. So, on August 9, a second atomic bombing took place. This time, another B-29 was piloted by Major Charles Sweeney's crew. The main target was Kokura, but it was obscured by thick clouds, so the plane turned to its backup target, Nagasaki. There were clouds there too, but there were gaps between them, which allowed the Fat Man to be dropped accurately. The bomb exploded over an industrial area, between steel and weapons factories in the south and an artillery factory in the north. The explosion had a yield of approximately 21 kilotons. However, most of the city was protected by hills, and the consequences were less severe than in Hiroshima. Up to 44% of buildings were destroyed, and the number of deaths is estimated at 40 to 80 thousand.

Groves reported that the next Fat Man bomb could be ready on August 17-18. But shocked by the terrible destruction and the number of civilian casualties, US President Harry Truman categorically refused. Japan had already surrendered. On August 15, the Emperor's address to the nation was broadcast on the radio, in which he read his rescript on the end of the war.

Rostyslav Maraev