Hitler's Terror Weapons by Brooks, Geoffrey (life books to read .txt) 📗

bomb to set it off if he had an implosion fuse. To separate 50 to 100 kilos of U235 is fantastically expensive and wasteful of resources and takes nearly three years to amass with (at today’s money) an investment of about 200,000 million dollars. Depending on the factor by which the uranium material is compressed, the U235 rationally needed for an implosion bomb would have been, at the most, just over ten kilos.

Explaining the Delays in Producing the U235 Bomb

Early in 1944, the head of the Manhattan Project, General Groves, had indicated that he would have “several” U235 bombs ready, but it would be the end of 1945 before they were available for use. What this means is that if the United States had had an implosion fuse in early 1944, three or four bombs would have been available for use against Germany. He expected to have the material for three or four devices for implosion, but if no implosion fuse were forthcoming, then it would be fifteen months or so before there was enough material to set off one ‘gun-type’ bomb. This explains how it was possible for Groves to dictate to the Secretary for War, Stimson, on 23 April 1945 that the target was, and was always expected to be, Japan. Groves was not the maker of State policy; it was simply the fact that his scientists could not produce the goods within the time scale which determined the policy.

Since the autumn of 1943 the Los Alamos experts had been working without success on how to compress a sphere the size of an orange uniformly over its surface area using 32 detonators fired within the same three-thousandth of a second. They had not progressed beyond a thermoelectric fuse taking 0.5 micro-seconds, which was too slow. In the hope of finding a solution, in October 1944 Robert Oppenheimer set up a three-man committee headed by physicist Luis Alvarez.

The technical portfolio being taken to Japan by U-234 passenger Dr Heinz Schlicke was a substantial one. He was an expert in explosives, detonators and fuses, in very high technology radar and radio systems, in the field of high frequency light waves, guided missile development and the V-2 rocket. Before leaving Germany he had met with numerous scientists to receive instruction in their technologies for later dissemination in Japan where he would serve as a scientific advisory liaison officer. A nuclear physicist with whom he had consulted was Professor Gerlach, Reich Plenipotentiary for Nuclear Science.

The fusing system to fire multiple detonators simultaneously was developed in the seven weeks between Schlicke arriving and the beginning of July. The solution was probably some kind of fuse in which a high-tension electrical impulse vaporized a wire to activate all 32 charges in 0.04-0.08 microseconds. The type of impulses involved, e.g. Thyratrons and Krytons, are produced in special high-tension and high-efficiency vacuum tubes notably in the field of HF radar in which Dr Heinz Schlicke was a specialist.

Three days after the Trinity test on 16 July 1945 Dr Schlicke delivered a lecture to the Navy Department on the subject of detonator fuses and afterwards shared the platform with Luis Alvarez for a question and answer session from the scientists present.

The likelihood exists that the Hiroshima device was detonated by an implosion fuse. The first mock-up version of the U235 bomb was so large that it would not have fitted into the bomb-bay of a B-29140, but the B-29 carrying the Hiroshima bomb had room in the bomb bay for several to fit in easily.

The Oak Ridge records show a large increase in enriched uranium stocks occurring in the third week of June 1945, at about the time when the implosion fuse suddenly became available. As this could be used to detonate a U235 bomb with far less material, one assumes that the bomb was split down and the surplus returned to store, thus radically increasing the amount available. This, and the smallness of the bomb, increases the probability that the Hiroshima device was imploded. The sudden increase in U235 stock has led people to speculate that it must have been of German origin, leading to claims that “the bombs dropped on Japan came from German arsenals”, but that was not, and logically cannot have been, the case.

Did the U-234 Cargo Influence US Policy?

The weight of evidence available suggests that the decision to use the atomic bomb against Japan occurred as the result of some hitherto unexplained factor occurring between 16 and 30 May, 1945, which dictated the chief aim of American strategic atomic policy to be the military defeat of Japan at the earliest possible opportunity.

As at 16 May, no executive decision had been taken to use the bomb, and Secretary for War Stimson advised President Truman that the rule of sparing the civilian population “should be applied, as far as possible, to the use of any new weapons”.141

On Saturday 19 May 1945 the German submarine U-234 berthed at Portsmouth New Hampshire: her specialist passengers were interrogated during the week beginning 24 May: Major Vance of the Manhattan Project arrived on 30 May to inspect the cargo and take away the heavy water and eighty little cases of “uranium powder”.

At a meeting of the Interior Committee on the morning of 31 May 1945:

“Mr Byrnes recommended and the Committee agreed that the Secretary for War should be advised that, while recognizing that the final selection of the target was a military decision, the present view of the Committee was that the bomb should be used against Japan as soon as possible, that it be used on a war plant surrounded by workers’ houses, that it be used without prior warning.”

Arthur H. Compton of the scientific panel noted of that morning’s decision that “it seemed to be a foregone conclusion that the bomb would be used”142, and when the meeting reconvened that afternoon the agenda had been amended so that consideration could be given to the question of the effect of the atom bomb