“...it was technically the second atomic bomb...” [D_Idaho, post 37]
“It wasn’t the world’s first atomic bomb.” [ifinnegan, post 45]
Technically, neither statement is correct.
The device detonated on 16 Jul 1945 was not a bomb, just an experimental warhead put together to test the feasibility of a basic concept.
The warhead still had to be fit inside a munitions case capable of being loaded onto an aircraft, to withstand any shock & vibration of transport to the launch site, more shocks & vibrations of takeoff and flight to the target, and - finally - to function reliably when the dropped weapon’s fuze ordered it to go off. The technical term is weaponization.
B-29s with special modifications had to be built, to employ the weapons. These were produced on the assembly line of the Martin bomber plant at Bellevue, Nebraska. Paul Tibbets was sent to choose the aircraft; the story has been told that after he made his first choice, he was advised to change his mind - his first pick was guessed to be unlucky, as it had been through final assembly on the day before the weekend. Or the day after.
Fortunately, some very good people realized all this from the outset and worked alongside the scientific teams, to render everything compatible and available when the moment came.
Even after the successful test of the plutonium core on 16 July 1945, risks remained very high. A sample size of one is better than nothing, but few were sure what might happen. Estimates covered a broad range, from “fizzle” to “the entire atmosphere of the planet will go up in flames.”
The weapon dropped over Hiroshima was of substantially different design, using uranium instead of plutonium. The experts deemed that it involved less risk and so declined any further testing. Its first live test was thus the combat drop on 6 August 1945.
509 CG had dropped a number of inert bomb-cases beforehand, to test out the aerodynamic stability of the munitions, and the function of subsystems. One subsystem never functioned correctly in all those rehearsals: the proximity fuze, which used radio waves to sense when the weapon approached the ground sufficiently close, and then sent the triggering signal.
So the first successful test of that system came in action.
So if the proximity fuse had never worked in all of those tests, I’m guessing they must have had a backup fuse? Like when it hit the ground it would have gone boom?
REF: My post 199
Oops.
I left out two important requirements of weaponization:
1. Safe separation of the weapon from the aircraft. Repeated inflight tests are conducted, under a variety of attack angles, pitch angles, airspeeds, and other conditions within the flight envelope.
2. Ability of the aircraft to escape effects of weapon detonation. Rarely a problem with “conventional” munitions launched from high altitudes, but a huge problem of great concern to aircrews when it came to the atomic bombs. Since it was not possible to conduct any live-drop tests before their employment in action, educated guesswork had to be applied, to work out the best airspeed, bank angle, turn rate, etc. Special protective gear was also issued to the crews.
Nice history lesson.
When was it Oppenheimer quoted Hindu scripture to himself?