13 Interesting Things About Little Boy, The Nuclear Bomb That Destroyed Hiroshima

On the fateful day of August 6, 1945, the second-ever atomic device, Little Boy, detonated over the city of Hiroshima killing 90,000- 166,000 people. Nearly half of the deaths occurred immediately after the bombing on the first day itself. In days to follow, many lost their lives or quality of life due to burns, injuries, illness, malnutrition and radiation sickness. Those who were killed are considered lucky by the survivors, since they did not even have enough time know what was happening, unlike the survivors who lived to suffer the after effects both physically and psychologically.

The debate regarding the ethics of killing civilians in warfare still goes on with the critics holding their point of view that it is a crime to incinerate civilians en masse; whereas the defenders claim that the bombing was necessary to bring the war to a close, thereby saving countless American and other allies’ lives.

Let us look into incidents that led to the explosion of Little Boy, which played a big role in ending the World War II and also some interesting facts about the first nuclear weapon used in war.

13. Postdam Declaration

The allied forces had declared in Postdam that they would invade Japan if the country did not agree for unconditional surrender of all the Japanese armed forces, and to provide proper and adequate assurance of their good faith in such action. The alternative for Japan was prompt and utter destruction. Japan did not agree.

Postdam declaration

12. False Alerts

The United States Army conducted many missions over Japanese cities that were composed of very few B-29 bombers prior to the actual bombing of Hiroshima to wear down the alertness of Japanese anti-aircraft defense crew. This ensured that when the actual atomic bomb arrived, the guard was let down by the Japanese defense team.

B 29 Bomber false alerts

11. Measurement

The Little Boy weighed 9,700 pounds (4,400 kg) and measured 10 feet and 28 inches (3.71 m) in diameter.

Little Boy dropped on Hiroshima

10. Production

The Little Boy was devised by scientists and technicians at the Los Alamos Laboratory. J. Robert Oppenheimer was the leader of the project. The entire project operated under top secrecy by mobilizing top scientists and engineers and at unprecedented high costs to maintain secrecy.

Los Almos Laboratory

9. Make

Little boy was a gun-type fission weapon that used Uranium-235 which is a rare isotope of Uranium. The raw material was extracted in massive factories built at Oak Ridge in Tennessee. The subcritical material was an alloy called Oralloy.

Uranium-235 in Little Boy



8. Function

Though the detonation looks like an explosion, the functioning of the atomic bomb is highly complicated process. Inside the Little Boy, a subcritical projectile of U-235 was fired at a subcritical target of U-235 inside a shortened smooth-bore 76.2 mm naval gun. The impact created a supercritical mass triggering a nuclear chain reaction.

Little Boy

7. No Warning

Though USA had dropped leaflets on cities they intended to bomb in Japan, Hiroshima did not receive any demonstration bombs or warning leaflets because of uncertainty of a successful detonation. It was also intended to increase the shock and psychological impact of the explosion.

Bomb dropped on Hiroshima

6. Untouched Before Attack

Hiroshima was largely untouched during the earlier air raids on Japan by the Army Air Forces so that the accurate assessment of the nuclear weapon could be made after the attack.

Hiroshima before bombing

5. Transport and deployment

Little Boy left the home ground abroad the cruiser USS Indianapolis from Hunters Point Naval Shipyard, California on 16th of July. On 6th of August the 393d Bombardment Squadron B-29, with Little Boy in Enola Gay (named after Tibbets’ mother), piloted by Tibbets, took off from Tinian which was six hours flight time from Japan.

4. Other Aircrafts

Enola Gay was accompanied by Straight Flush, Jabit III, Full House, Necessary Evil, Top Secret and The Great Artiste. While the mission role of Enola Gay was weapon delivery, the other aircrafts carried the roles of Weather reconnaissance (Hiroshima), Weather reconnaissance (Kokura), Weather reconnaissance (Nagasaki), Blast measurement instrumentation, Strike observation and photography.

attack on Hiroshima

3. Explosion

At 8:15 Hiroshima time, Little boy was released at the height of 31,000 feet by bombardier Major Thomas Ferebee after being handed over the control by Tibbets. The Little Boy loaded with 64 kg of Uranium-235 took 44.4 seconds to fall from the aircraft to 580 m above the city from where it detonated. After moving ahead 18.5 km, Enola Gay felt the shock of the explosion.

Hiroshima bombed

2. The Destruction

The original aiming point was Aioi Bridge, but due to cross wind the Little Boy detonated directly over Shima Surgical Clinic creating a blast equivalent to 16 kilotons of TNT ± 2 kt. The result was total destruction for about 1.6 km, with resulting fires across 11 km2, yet only 1.7% of the material had fissioned. A bright flash (pika) was followed by a booming sound (don) according to the people who witnessed the explosion and survived.

hiroshima bomb dropped

1. The Casualties

Some 70,000–80,000 people, of whom 20,000 were soldiers, or around 30% of the population of Hiroshima, were killed by the blast and resultant firestorm and another 70,000 injured. Also, over 90% of the doctors and 93% of the nurses in Hiroshima were killed or injured. Eizō Nomura was the closest known survivor, who was only 170 meters from ground zero and Akiko Takakura was among the closest survivors to the hypocenter of the blast. A significant portion of those who were killed at Hiroshima were Korean workers. It was estimated that 10,000 to 20,000 Koreans made up of the total 70,000 to 80,000 who died in the initial few days of the bombing.

deaths in Hiroshima

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