JF Ptak Science Books Post 1523
The names of Col. Paul Tibbets and the Enola Gay are instantly recognizable, instantly placeable in the history of the twentieth century. Fact is though that Tibbets didn't pilot his (well, Capt. Robert A. Lewis')1 B-29 all the way to Hiroshima and back, and wasn't at the controls when the bomb was released. Tibbets (also known as "Old Bull") shared some of the tactically flawless mission with his co-pilot Capt. Lewis, and also with George. Well, its actually "George", the personified names for the autopilot of the aircraft, and I guess on the long road to splitting the atom it doesn't matter much who did what at the final moments, especially if you were on the ground in Hiroshima.
It was Tibbets who flew the Enola Gay most of the way, through perfect skies, nothing to stand in the way of the aircraft and the completed mission--no Japanese fighter aircraft to haunt and hunt, and no anti-aircraft coming from the ground, at least not at their low altitude.2 "George" was at the controls at 0815 on 6 August 1945--Tibbets would take control of the plane as the bomb fell away3, ripping the plane into a steep bank in trying to put as much distance between the aircraft and the bomb in the 43 or so seconds that they had before the explosion. Everything else about the bomb and the mission at the moment of release was controlled by a human--except for the flying of the aircraft. "
"Archie"4 is the other name not so much remembered on this morning. This was the name given to the apparatus (there were actually four of them on the bomb) that would initiate the final arming sequence for the MK1 bomb, "Little Boy", one of a component of a fusing system that triggers the firing system. It was a nicer handle I guess than its official name, which was AP-13.
1. Lewis was the original pilot of the aircraft until Tibbets was chosen to lead the mission against Hiroshima. Tibbetts was named on 5 August and acted very quickly to get a painter to paint a name on the fuselage of B-29 82--so quickly that the guy who painted Tibbets' mother's name on the plane had to be pulled out of a baseball game to do the job. When Lewis saw it, saw his plane with "Enola Gay" on it, he reacted badly, as he was mighty pissed. He confronted Tibbets about it, but the Colonel informed the Captain that there was nothing to discuss.
2. Intelligence reported that the only antiaircraft resistance that could be expected were from heavier guns, which also happen to be very ineffective at the low altitude at which the Enola Gay flew. This also benefited another aspect of the flight plan, which was fuel consumption--coming in low meant a big fuel savings, which in this case was very important because of the enormous load that the aircraft was hauling.
3. The Enola Gay would climb at last to 31,000 feet to release the bomb, which exploded at about 1980 feet above the ground.
4. An interesting document from General Groves sums up the Archies nicely: "Memorandum dated 24 August 1944 to Major General L. R. Groves from R. N. Brode, subject: Personnel with Radar Experience. According to the latter, the APS-13 was originally called the "Charlie" and those units to be adapted to atomic bombs were to be rigged to operate at selectable frequencies between 250 and 500 megahertz. By 1 January 1945, the "Archies," with a "natural" range of 405 to 435 MHz, could be tuned between 325 and 485 MHz. ("Interim Report Archie Frequency Range," Lt. Leo Gross, 1 January 1945)--The History of U.S. Electronic Warfare, by Alfred Price, Association of Old Crows, Alexandria, Virginia, 1984, p. 232."
"By the spring of 1944, the APS-13 "tail warning device" was under study for use as a radar fuse. Originally designed to warn a pilot of another aircraft approaching the rear of his plane, the "Archie" had an effective range of about 2,000 to 2,500 feet." Source: The Swords of Armageddon: U.S. Nuclear Weapons Development since 1945, Chuck Hansen, September 4, 1995, vol. VIII, pp. 3-45.
"Four "Archies" were used on each bomb, with a network of relays so that when any two of the units signaled, stored current was sent into the detonators (one on the MK I and 32 on the MK III). The antennas for the "Archies" were attached to the sides of the bomb casings.
"A barometric pressure-sensing switch closed when the bomb passed 7,000 feet; the bombs were dropped from altitudes between 31,000 and 32,000 feet. A bank of clock-operated timer switches, started by arming wires pulled out when the bomb was dropped, closed 15 seconds after release to prevent the "Archies" from being triggered, in case of baroswitch short-circuit, by radar signals reflected from the delivery aircraft.
"The arming and firing sequence for the first two atomic bombs was (1) 15 seconds after release, when the weapon had fallen 3,600 feet, the timer switches closed part of the firing circuit; (2) at an altitude of 7,000 feet, the barometric switch closed another part of the firing circuit and allowed electrical current from batteries in the bomb to charge a number of capacitors and turn on the radar fuses; (3) at an altitude of about 1,800 feet, radar signals emanating from the "Archies" and reflecting from the ground completed the last part of the firing circuit and triggered the detonation signal."