THE END OF WWII– Dr. Ijaz ur Rahman Durrani
NUCLEAR FISSION:
Tinian is a long , thin island, approximately 19 km by 3 at the southern end of the Mariana group about 2300 km from Tokyo . It was captured from the Japanese by the Americans on 1 August 1944, and rapidly transformed into the largest air base in the world with six 2 mile long runways. The island reverberated from the impact of hundreds of B-29 Superfortresses , which carried out routine , conventional bombing and incendiary attacks on Japanese cities, but a very special mission was launched on 6 August 1945.
At 0245 hours local time a heavily loaded , newly modified B-29 took off from the base , piloted by Colonel Paul Tibbetts, the commander of the 509th Composite Group . He had christened the plane Enola Gay, his mother’s names, and the words were painted on the fuselage . Exactly 7 hours , 30 minutes and 30 seconds later the plane dropped the first ever atomic bomb , from a height of 9,631 m, on to the city of Hiroshima . The bomb was codenamed ‘ Little Boy’ . It consisted of a modified gun barrel , sealed at both ends and contained in a cylindrical outer casing. With fins to give it stability when dropped it was about 3 m long and 0.75 m in diameter. It only weighed about 4,100 kg but it had e same power as 12,700 tonnes of TNT, so that it completely dwarfed any previous single explosion.
Conventional bombs were generally fused to explode when they hit the ground so that much of their blast effect was directed upwards into the air , which limited the damage they could do. In contrast , the atom bomb was set off at a height of 580 m so that its particularly powerful blast , much of it directed downwards , could cause damage over a large area of the ground below. The blast destroyed 60 per cent of the city and flattened an area of 9 sq. km. of buildings , many of which had been specially constructed to withstand the effects of the earthquakes. By the time the bomb went off, Colonel Tibbetts had had about 45 seconds to take evasive action and his plane was more than 16 km away but he and his crew still felt the effects of the heat. But the blast effect was not the only , nor the worst , aspect of the bomb. There was a tremendous flash of light and heat as the bomb went off ant it was later estimated that the temperature at the point of explosion reached almost 3,000o C . People immediately below the bomb were scorched into small piles of black ash ; many of those who were out in the open as far as 2.5 miles away were severely burnt ; telegraph poles at the same distance were charred or set on fire ; the surface of granite , 600 m away , was partially melted ; and much of the city was aflame for days.
Those who were not blown or burnt to death , thought that they had survived but many of them , within a short time , began to realize that they were not feeling at all well, and it slowly began to dawn that they were suffering from radiation sickness caused by exposure to an overdose of gamma-radiation from the exploding bomb. The main , immediate effect was to disrupt the regeneration of blood cells within the body which led to bleeding , infection or anemia. Some, lucky ones died quickly . Others lingered on , suffering from insidious , incurable symptoms for many years, before their turn came.
Because of the on-going deaths , it is difficult to quantify the calamity accurately. There were about 350,000 people in Hiroshima a the moment the bomb went off . Shortly afterwards the Japanese authorities estimated that 71,000 had been killed and 68,000 injured , but, over the years, the mortality figure grew remorselessly until more than 50 per cent of those who had been there on 6 August were thought to be dead.
As the Japanese did not surrender , a second plane, named Bock’s Car after its usual pilot’s name , but flown on this mission by Major Charles W. Sweeney , took off on 9 August with the intention of dropping a second bomb on Kokura . That city, however, was covered by cloud so, after three abortive attempts to find the target , Major Sweeney flew on his secondary target which was Nagasaki. Visibility was still not very good when he arrived there but, at the last moment, and when he was beginning to run short of fuel , a hole opened up in the clouds and the bomb was dropped. It was 1102 hours. This bomb codenamed ‘Fat Man’ , was of a different type from ‘Little Boy’. It was egg shaped , about 3.5 m long with a maximum diameter of 1.5 m and it weighed about 4,536 kg. ‘ Fat Man’ equivalent of 22,350 tonnes of TNT, was more powerful than ‘ Little Boy’ but it caused less damage because it was dropped slightly off target and because the terrain of Nagasaki was hilly. Nevertheless , 45 pr cent of the city was destroyed and the final death toll was thought to exceed 50 per cent , as at Hiroshima.
The Japanese offered to surrender on August , without knowing that there were no other atomic bombs available for immediate use.
THE END OF WW-II