Making of the Atomic Bomb
Pathfinders started dropping yellow markers and bombs at fifty-five minutes past midnight on July 28. Five minutes later the main bomber stream arrived. Marking was good and creep-back was slow. Later arrivals began to notice a difference between this raid and others they had flown: “Most of the raids we did looked like gigantic firework displays over the target area,” a flight sergeant remarks, “but this was ‘the daddy of them all.’ ”1826 A flight lieutenant distinguishes the difference:
The burning of Hamburg that night was remarkable in that I saw not many fires but one. Set in the darkness was a turbulent dome of bright red fire, lighted and ignited like the glowing heart of a vast brazier. I saw no flames, no outlines of buildings, only brighter fires which flared like yellow torches against a background of bright red ash. Above the city was a misty red haze. I looked down, fascinated but aghast, satisfied yet horrified. I had never seen a fire like that before and was never to see its like again.1827
The summer heat and low humidity, the mix of high-explosive and incendiary bombs that made kindling and then ignited it and the absence of firefighting equipment in the bombed districts conspired to assemble a new horror. An hour after the bombing began the horror had a name, recorded first in the main log of the Hamburg Fire Department: Feuersturm: firestorm. A Hamburg factory worker remembers its beginning, some twenty minutes into the one-hour bombing raid:
Then a storm started, a shrill howling in the street. It grew into a hurricane so that we had to abandon all hope of fighting the [factory] fire. It was as though we were doing no more than throwing a drop of water on to a hot stone. The whole yard, the canal, in fact as far as we could see, was just a whole, great, massive sea of fire.1828
Small fires had coalesced into larger fires and, greedy for oxygen, had sucked air from around the coalescing inferno and fanned further fires there. That created the wind, a thermal column above the city like an invisible chimney above a hearth; the wind heated the fury at the center of the firestorm to more than 1,400 degrees, heat sufficient to melt the windows of a streetcar, wind sufficient to uproot trees. A fifteen-year-old Hamburg girl recalls:
Mother wrapped me in wet sheets, kissed me, and said, “Run!” I hesitated at the door. In front of me I could see only fire—everything red, like the door to a furnace. An intense heat struck me. A burning beam fell in front of my feet. I shied back but, then, when I was ready to jump over it, it was whirled away by a ghostly hand. I ran out to the street. The sheets around me acted as sails and I had the feeling that I was being carried away by the storm. I reached . . . a five-storey building in front of which we had arranged to meet again. . . . Someone came out, grabbed me by the arm, and pulled me into the doorway.1829
The fire filled the air with burning embers and melted the streets, a nineteen-year-old milliner reports:
We came to the door which was burning just like a ring in a circus through which a lion has to jump. . . . The rain of large sparks, blowing down the street, were each as large as a five-mark piece. I struggled to run against the wind in the middle of the street but could only reach a house on the corner . . . .1830
We got to the Löschplatz [park] all right but I couldn’t go on across the Eiffestrasse because the asphalt had melted. There were people on the roadway, some already dead, some still lying alive but stuck in the asphalt. They must have rushed on to the roadway without thinking. Their feet had got stuck and then they had put out their hands to try to get out again. They were on their hands and knees screaming.
The firestorm completely burned out some eight square miles of the city, an area about half as large as Manhattan. The bodies of the dead cooked in pools of their own melted fat in sealed shelters like kilns or shriveled to small blackened bundles that littered the streets. Or worse, as the woman who was once the fifteen-year-old girl horribly recreates:
Four-storey-high blocks of flats [the next day] were like glowing mounds of stone right down to the basement. Everything seemed to have melted and pressed the bodies away in front of it. Women and children were so charred as to be unrecognizable; those that had died through lack of oxygen were half-charred and recognizable. Their brains had tumbled from their burst temples and their insides from the soft parts under the ribs. How terribly these people must have died. The smallest children lay like fried eels on the pavement.1831
Bomber Command killed at least 45,000 Germans that night, the majority of them old people, women and children.
The bombing of Hamburg was hardly unique. It was one atrocity in a war of increasing atrocities. Between 1941 and 1943 the German Army on the Eastern Front captured and enclosed in prisoner-of-war camps without food or shelter some two million Soviet soldiers; at least one million of them died of exposure and starvation.1832 During the same period the Final Solution to the Jewish Question—the vast Nazi program to exterminate the European Jews—began in deadly earnest after the Wannsee Conference of coordinating agencies met in suburban Berlin on January 20, 1942. Whatever moral issues such atrocities raise, they resulted from the progressive escalation of the war by all its belligerents in pursuit of victory. (Even the Final Solution: because the Nazis believed the Jews constituted a separate nation lodged subversively in their midst—nationality being defined in the Nazi canon primarily in terms of race—and as such the nation with which the Third Reich was preeminently at war. It was Hitler’s particular perversity to define victory over the Jews as extermination; the Allies in their defensive war against Germany and Japan wanted only total surrender, in return for which the mass killing of combatants and civilians would stop.)
One way the belligerents could escalate was to improve their death technologies. Better bombers and better bomber defenses such as Window were hardware improvements; so were the showers at the death camps efficiently pumped with the deadly fumigant Zyklon B. The bomber-stream system and allowance for creep-back were software improvements; so were the schedules Adolf Eichmann devised that kept the trains running efficiently to the camps.
The other way the belligerents could escalate was to enlarge the range of permissible victims their death technologies might destroy. Civilians had the misfortune to be the only victims left available. Better hardware and software began to make them also accessible in increasing numbers. No great philosophical effort was required to discover acceptable rationales. War begot psychic numbing in combatants and civilians alike; psychic numbing prepared the way for increasing escalation.
Extend war by attrition to include civilians behind the lines and war becomes total. With improving technology so could death-making be. The bombing of Hamburg marked a significant step in the evolution of death technology itself, massed bombers deliberately churning conflagration. It was still too much a matter of luck, an elusive combination of weather and organization and hardware. It was still also expensive in crews and matériel. It was not yet perfect, as no technology can ever be, and therefore seemed to want perfecting.
The British and the Americans would be enraged to learn of Japanese brutality and Nazi torture, of the Bataan Death March and the fathomless horror of the death camps. By a reflex so mindlessly unimaginative it may be merely mammalian, the bombing of distant cities, out of sight and sound and smell, was generally approved, although neither the United States nor Great Britain admitted publicly that it deliberately bombed civilians.1833 In Churchill’s phrase, the enemy was to be “de-housed.” The Jap and the Nazi in any case had started the war. “We must face the fact that modern warfare as conducted in the Nazi manner is a dirty business,” Franklin Roosevelt told his countrymen. “We don’t like it—we didn’t want to get in it—but we are in it and we’re going to fight it with everything we’ve got.”1834
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The Los Alamos review committee headed by W.K. Lewis of MIT reported its findings on May 10, 1943. It approved the laboratory’s nuclear physics research program. It recommended that theoretical investigation of the thermonuclear bomb continue at second priority, subordinate to fission bomb work.
It proposed a major change in the chemistry program: final purification of plutonium on the Hill, because Los Alamos would be ultimately responsible for the performance of the plutonium bomb and because the scarce new element would be used and reused for experiments during the months before a sufficient quantity accumulated to load a bomb and would have to be frequently repurified. The Lewis committee also concurred in a recommendation Robert Oppenheimer had made in March that ordnance development and engineering should begin immediately at Los Alamos rather than wait until nuclear physics studies were complete. General Groves accepted the committee’s findings; they dictated an immediate doubling of Hill personnel.1835 Thereafter until the end of the war the Los Alamos working population would double every nine months. The dust of construction never settled; housing would always be short, water scarce, electricity intermittent. Groves spent not a penny more than necessary on comforts for civilians.
The bottom pole piece of the Harvard cyclotron had been laid on April 14; by the first week in June Robert Wilson’s cyclotron group saw signs of a beam. The Wisconsin long-tank Van de Graaff came on line at 4 million volts on May 15 and the 2 MV short-tank Van de Graaff on June 10. In July the first physics experiment completed at Los Alamos counted the number of secondary neutrons Pu239 emitted when it fissioned. “In this experiment,” says the Los Alamos technical history, “the neutron number was measured from an almost invisible speck of plutonium and found to be somewhat greater even than for U235.”1836 The experiment thus established what had not yet been confirmed despite the expensive rush of building: that plutonium emitted sufficient secondary neutrons to chain-react.
The speck of plutonium was Glenn Seaborg’s 200-milligram sample of Met Lab oxide, which he had sent to Los Alamos at the beginning of the month. Seaborg had worked himself sick at the Met Lab that spring—an upper respiratory infection compounded with exhaustion and a persistent fever—and came to New Mexico with his wife during July to vacation. (“I guess I deliberately chose to be near the plutonium,” he muses. “I wonder why?”) Too much peace and quiet at a guest ranch threatened to exhaust him further and on July 21 he and his wife moved to the adobe-style La Fonda Hotel in Santa Fe.1837 Compartmentalization put Los Alamos off limits. The Seaborgs were ready to return to Chicago on Friday, July 30, and Seaborg proposed to carry the Pu sample, most of the world’s supply, back with him on the train. Robert Wilson and another physicist made the transfer before dawn in the restaurant where the Seaborgs were having breakfast in Santa Fe, Wilson arriving in a pickup armed Western-style with his personal Winchester .32 deer-hunting rifle to guard a highly valuable but barely visible treasure. “Then I just put it in my pocket and then into my suitcase,” Seaborg remembers.1838 He proceeded to Chicago unarmed.
To direct the expanded Ordnance Division Groves asked the Military Policy Committee in Washington to recommend a good man, preferably a military officer. Vannevar Bush knew a naval officer—would Groves mind? “Of course not,” the general humphed.1839 Bush proposed Captain William S. “Deke” Parsons, a 1922 Annapolis graduate then responsible under Bush for field-testing the proximity fuse.1
Parsons had also worked on early radar development and served as gunnery officer on a destroyer and experimental officer at the Naval Proving Ground in Dahlgren, Virginia. He was forty-three, cool, vigorous, trim, nearly bald, spit-and-polish but innovative; “all his life,” one of the men who worked for him at Los Alamos testifies in praise, “he fought the silly regulations and the conservatism of the Navy.”1840 Groves liked him; “within a few minutes [of meeting him],” the general says, “I was sure he was the man for the job.”1841 Oppenheimer interviewed the man for the job in Washington and agreed. Parsons was married to Martha Cluverius, a Vassar graduate and the daughter of an admiral; with two blond daughters and a cocker spaniel the couple arrived at Los Alamos in an open red convertible in June.
Parsons’ first order of business was the plutonium gun. Because it needed a muzzle velocity of at least 3,000 feet per second it would have to be 17 feet long. It should weigh no more than a ton, a fifth of the usual weight of a gun that size, which meant it would have to be machined from strong high-alloy steel. It would not require rifling but needed three independently operated primers to make sure it fired. Parsons arranged for the Navy’s gun-design section to engineer it.
Norman F. Ramsey, a tall young Columbia physicist, the son of a general, served under Parsons as group leader for delivery: for devising a way to deliver the bombs to their targets and drop them. In June he contacted the U.S. Air Force to identify a combat aircraft that could carry a 17-foot bomb. “As a result of this survey,” Ramsey writes, “it was apparent that the B-29 was the only United States aircraft in which such a bomb could be conveniently carried internally, and even this plane would require considerable modification so that the bomb could extend into both front and rear bomb bays. . . .1843, 1844 Except for the British Lancaster, all other aircraft would require such a bomb to be carried externally.” The Air Force was not about to allow a historic new weapon of war to be introduced to the world in a British aircraft, but the B-29 Superfortress was a new design still plagued with serious problems. The first service-test model had not yet flown when Ramsey began his aircraft survey in June; a flight-test model had crashed into a Seattle packing house in February and killed the plane’s entire test crew and nineteen packing-house workers.
Ramsey did not have to wait for access to a B-29 to begin collecting data on the long bomb’s ballistics, however. He mocked up a scale model and arranged to see it dropped:
On August 13, 1943, the first drop tests of a prototype atomic bomb were made at the Dahlgren Naval Proving Ground [by a Navy TBF aircraft] to determine stability in flight. These tests were on a 14/23 scale model of a bomb shape which was then thought probably suitable for a gun assembly. Essentially, the model consisted of a long length of 14-inch pipe welded into the middle of a split standard 500-pound bomb. It was officially known at Dahlgren as the “Sewer Pipe Bomb.” . . . The first test . . . was an ominous and spectacular failure. The bomb fell in a flat spin such as had rarely been seen before. However, an increase in fin area and a forward movement of the center of gravity provided stability in subsequent tests.1845
In the meantime Seth Neddermeyer, whose implosion experimentation group Parsons inherited, had visited a U.S. Bureau of Mines laboratory at Bruceton, Pennsylvania, to experiment with high explosives. Edwin McMillan, who was interested in implosion, went with the Caltech physicist:
At that point it was just Seth and myself with a few helpers. The first cylindrical implosions were done at Bruceton. You take a piece of iron pipe, wrap the explosives around it, and ignite it at several points so that you get a converging wave and squash the cylinder in. That was the birth of the experimental work on implosion, long before experimental work on the gun method.1846
Back at Los Alamos Neddermeyer set up a small research station on South Mesa, the next mesa south of the Hill across Los Alamos canyon. He fired his first tests in an arroyo on Independence Day, 1943, using iron pipe set in cans packed with TNT. Experimenting with cylinders rather than spheres simplified calculation. Because he wanted to recover the results he packed only limited amounts of explosive. “Those tests of course could not be very sophisticated,” says McMillan. “ . . . They did show that you could take metal pipes and close them right in so that they became like solid bars, indicating that this was a practical method.”1847 They also showed that the squeeze was far from uniform: the pipes emerged from the arroyo dust twisted and deformed.
When Parsons, a thoroughly pragmatic engineer, had time to look over Neddermeyer’s work he was openly contemptuous. He doubted if implosion could ever be made reliable enough for field use. Neddermeyer presented his initial results at one of the weekly colloquia Oppenheimer had instituted at Hans Bethe’s suggestion to keep everyone with a white badge—everyone cleared for secrets—informed of Tech Area progress. Richard P. Feynman, a brilliant, outspoken New York-bo
rn graduate-student theoretician from Princeton, summarized the opinion of the assembly in a phrase: “It stinks.”1848 In the name of lightheartedness Parsons was crueler. “With everyone grinding away in such dead earnest here,” he told the group, “we need a touch of relief. I question Dr. Neddermeyer’s seriousness. To my mind he is gradually working up to what I shall refer to as the Beer-Can Experiment.1849 As soon as he gets his explosives properly organized, we will see this done. The point to watch for is whether he can blow in a beer can without splattering the beer.” Implosion was even harder to do than that.
John von Neumann, the Hungarian mathematician who had come to the United States in 1930 and joined the Institute for Advanced Study, had been examining for the NDRC the complex hydrodynamics of shock waves formed by shaped charges, technology which was being applied to the American tank-killing infantry weapon known as the bazooka. Like Rabi, von Neumann had agreed to serve as an occasional Oppenheimer consultant. He visited Los Alamos at the end of the summer and looked into implosion theory, another warren of hydrodynamic complexity. Neddermeyer had devised “a simple theory that worked up to a certain level of violence in the shockwave.” Von Neumann, he says, “is generally credited with originating the science of large compressions. But I knew it before and had done it in a naive way. Von Neumann’s was more sophisticated.”1850
“Johnny was quite interested in high explosives,” Edward Teller remembers. Teller and von Neumann renewed their youthful acquaintance during the mathematician’s visit to the Hill. “In my discussions with him some crude calculations were made,” Teller continues. “The calculation is indeed simple as long as you assume that the material to be accelerated is incompressible, which is the usual assumption about solid matter. . . . In materials driven by high explosives, pressures of more than 100,000 atmospheres occur.” Von Neumann knew that, Teller says, as he did not. On the other hand: