for his laboratory and deferment from military service for his young men, the bare record does not reveal. On the occasion of the November 17 conference he once again complained of the lack of sufficiently powerful vacuum tubes for his cyclotron and told Nobuuji, contrary to the evidence of experiment, that the Riken's efforts at isotope separation were “now at a midpoint in their practical solution.” Nobuuji might have been more helpful if he had understood even the most basic facts of the work. An exchange between the two men late in the meeting indicates the military liaison was as innocent of nuclear physics as a stone:
A B-29, specially modified, first dropped an atomic bomb — a dummy Thin Man — at Muroc Army Air Force Base in California on March 3, 1944. Restrained by sway-bracing, a bomb hung singly in the B-29's bomb bay from a single release, and the first series of tests ended ignominiously that season when a release cable loosened and dumped one onto closed bomb-bay doors at 24,000 feet. “The doors were then opened,” a technical report notes, “and the bomb tore free, considerably damaging the doors.” A second series of tests in June went better. Word that Fat Man would be heavier than previously estimated encouraged Norman Ramsey's Delivery group to replace the original bomb-release mechanism, which had been modified from a standard glider tow release, with a sturdier British Lancaster bomber design.
Lessons learned, the Air Force began modifying seventeen more B-29's at the Glenn L. Martin plant in Omaha, Nebraska, in August; that month the service prepared to train a special group to deliver the first atomic bombs. The 393rd Bombardment Squadron, then based at Fairmont, Nebraska, in training for Europe, would form the nucleus of the new organization. Late in August Henry H. (“Hap”) Arnold, the commanding general of the U.S. Army Air Forces, approved the assignment of an Illinois-born lieutenant colonel, Paul W. Tibbets, twenty-nine years old, to be group commander.
Tibbets may well have been the best bomber pilot in the Air Force. He had led the first B-17 bombing mission from England into Europe, had carried Dwight Eisenhower to his Gibraltar command post before the invasion of North Africa and had led the first bomber strike of that invasion. More recently he had been test-piloting the B-29, which in 1944 was just beginning to come on line, working with the physics department of the University of New Mexico in Albuquerque to determine how well the new bomber could defend itself against fighter attack at high altitude. He was a man of medium height and stocky build with dark, wavy hair and a widow's peak, full-faced and square-jawed, a pipe smoker. His father was a candy wholesaler in Florida and a disciplinarian from whom Tibbets probably acquired his reserved perfectionism; he was closer to his mother, the former Enola Gay Haggard of Glidden, Iowa. He had chosen an Air Force career, he told a postwar interviewer, after his mother had supported him in that choice against his father's opposition:
When I was in college, studying to be a doctor, I realized that I had always wanted to fly. In 1936, my desire to do something about it reached the point where a family showdown on the subject developed. During the discussion, a few tempers flared, but my mother never said a word. In the end, still undecided, I got her off” to the side and asked her what she thought. Despite the things that had been said on the subject, and the fact that most of the people in the discussion had included the statement, “You'll kill yourself in an airplane,” Mother said, quite calmly and with positive assurance, “You go ahead and fly. You will be all right.”
So far he had been, and now he had won a new assignment. He flew to Second Air Force headquarters in Colorado Springs at the beginning of September 1944 to report to commanding Major General Uzal Ent. An aide installed him in the general's anteroom. An officer came out, introduced himself, took Tibbets aside and asked him if he had ever been arrested. Tibbets considered the situation and decided to answer honestly to this stranger that he had been, as a teenager in North Miami Beach, caught
The Air Force chose Wendover Field, Utah, as home base for the new organization. Tibbets flew to Utah early in September, looked the base over and liked what he saw. It was sited between low mountain ranges on the desert salt flats in gritty and secure isolation 125 miles west of Salt Lake City near the Utah-Nevada border; the flat basin, the sink of an ancient and enormous freshwater lake of which the Great Salt Lake is a brackish remnant, offered miles of desolation for bombing practice. Pioneers bound for California had suffered the crossing once — their wagon ruts could still be viewed nearby. The 393rd moved to Wendover in September and with the addition of troop-carrier and other support components became the 509th Composite Group. In October it began receiving its new B-29's.
A Boeing product, the B-29 was a revolutionary aircraft, the first intercontinental bomber. It was conceived in the late 1930s by ambitious officers within what was then still the Army Air Corps as the vehicle of their vision of wars fought at great distance by strategic air power. As early as September 1939 they proposed its use from bases in the Philippines, Siberia or the Aleutians in the event of war against Japan. It was the world's first pressurized bomber and at 70,000 pounds the heaviest production bomber ever built, 135,000 pounds loaded, a weight that required an 8,000-foot runway to lumber airborne. In appearance it was a sleek, polished-aluminum tube 99 feet long intersected by huge 141-foot wings — two B-29's would fill a football field — with a classic sinusoidal tail nearly three stories tall. Four Wright 18-cylinder radial engines that each developed 2,200 horsepower propelled it at altitude at 350 miles per hour maximum speed — it cruised at 220 — and it was designed to fly a 4,000-mile mission with up to 20,000 pounds of bombs, though 12,000 pounds was nearer its operational load. It could cruise above 30,000 feet, out of range of flak and of most enemy fighters. Turbosuperchargers boosted engine power; out-sized 16.5-foot propellers turned more slowly than those of any other aircraft; wing flaps, the world's largest, adjusted a fifth of wing area to adapt the high-speed, long-range, low-drag wing for takeoff and landing.
On the ground the B-29 rested level on three point landing gear: retractable wheels at the nose and under each wing. The plane's eleven-man crew occupied two pressurized sections within the five joined sections of the fuselage; tandem bomb bays fore and aft of the wings separated the nose section from the waist and tail, and to pass back from the nose to the waist required crawling through a pressurized one-man tunnel. The standard B-29 crew counted pilot, copilot, bombardier, flight engineer, navigator and radio operator in the nose section, three gunners and a radar operator in the waist and another gunner in the tail. Because electrical wiring was less vulnerable to battle damage than pneumatic or hydraulic tubing, the aircraft systems with the exception of the hydraulic wheel brakes operated entirely on electric motors, more than 150 in all, with a gasoline-powered donkey engine in the rear fuselage supplying current on the ground. Analog computers ran a central gun-control system, but all the guns were stripped from 509th bombers except the 20-millimeter cannon in the tail.
If the B-29's engines were powerful they were also notoriously susceptible to fires. To improve their horsepower-to-weight ratio Wright had used magnesium for their crankcases and accessory housings. Engine cooling was inadequate and exhaust valves tended to overheat and stick; an engine would then sometimes swallow a valve and catch fire. If the fire reached the magnesium, a metal commonly used in incendiary bombs, the engine would usually burn through the main wing spar and peel off the wing. To prevent such disasters Boeing improved engine cooling but the basic design fault persisted; there was no time to develop a new power plant if the aircraft was to serve the war for which it was invented. (One Delivery group physicist remembers skimming along at Wendover for miles after takeoff, mowing sagebrush, to cool the engines before climbing to altitude.)
Once at altitude the flight crews of the 509th practiced bombing runs, bombardiers aiming from above
