Hitler's Terror Weapons (21 page)

Radon gas would imply the presence within the containers of radium in some form. A radium-beryllium source within a small sphere of heavy water at the centre of uranium oxide in a gold-lined cylinder would amount to a sub-reactor in miniature and meet the request of the Japanese for “a quantity of uranium oxide” in connection with their atomic research into the fissile isotopes including plutonium.

Pfaff's warning that the material must be handled like crude TNT indicates that the same precautions apply to the material as for the most unstable explosive. This is because the substance within the small cylinders becomes sensitive and dangerous on exposure to air. If these gold-lined cylinders were miniature sub-reactors, then the following dangers would present themselves when the cylinders were opened:

(1) Plutonium particles from the irradiated uranium oxide would rise into the atmosphere. The inhalation or ingestion of 1mg of plutonium will result in the lingering death of the victim within weeks and even a microgram results in a later high susceptibility to pulmonary cancer.

(2) Dangerous neutron radiation would be emitted from the reaction of the radium-beryllium source as would gamma and corpuscular radiation from the products of fission decay in the uranium powder.

This was why it was so dangerous to open the cylinders. The use of a gold lining in addition to the lead shielding is the clearest possible indication that a reaction process was continuing in the cylinders, and Professor Nishina of the Imperial Japanese Army nuclear project would have received, on the arrival of
U-234
in Tokyo, ten cases of uranium oxide containing precisely what had been requested in the Magic signals.

The cylinders though dangerous were basically nothing more than an elementary research material for the laboratory and would not have led the Americans to panic and suspect that Japan was on the verge of developing an atom bomb.

The Eighty Small Heavy Cases

To the exclusion of everything else aboard
U-234,
these eighty small containers in the custody of Major Vance, the tests performed on them by the Manhattan Project, and their ultimate disposal, are the obvious basis for further research.

They were removed from their loading tube at the end of May. Aboard the submarine there was no mystery as to where they had been stowed for probably half the crew had worked on the loading that day in February and the contents excited interest by their unusual weight. Portentous omens have been read into the meaning of the symbol “U-235” painted by Tomonaga on the wrapping of each of the small containers, but probably it served merely to identify the consignment as being uranium. I have no idea what the correct chemical formula is for natural uranium enriched with plutonium isotopes, and I doubt if Tomonaga would have known either: if on the other hand the cases actually had contained the isotope, it is unlikely in the extreme that the fact would have been advertised to all and sundry on the quayside: the Japanese, past masters of deception, even disguised their initial interest in uranium as being a sort of “catalyst”.

The New Hampshire evening paper
Portsmouth Herald
announced in the week following the capture of
U-234
that the submarine had been “headed for Japan for the purpose of aiding Japan's air war with rocket and jet planes and other German V-type bombs”. This is the first reference from a source well-connected to the US Navy to a “V-type bomb” and a “jet plane”, neither of which feature on the Unloading Manifest. And in June the same newspaper claimed that there had been sufficient uranium aboard
U-234
to produce an explosion to eradicate all of Portsmouth and its surrounding suburbs from the face of the earth. Newspaper reports must, of course, not be awarded too much credence as historical documents, but they are nevertheless useful pointers. The
Portsmouth Herald
knew about a “jet plane” aboard
U-234
which is claimed by the German crew to have been shipped, but as to which the official record on the American side is silent. And to what extent before the first Trinity test in July 1945 was the effect of fantastic explosives openly discussed, and where did the idea come from that such a substance was aboard the German submarine?

Lt-Col John Lansdale, chief of atomic security and intelligence for the Manhattan Project, admitted that he handled the disposal of the small cases aboard
U-234.
¹³⁸
He recalled that the American military authorities reacted with panic when they discovered the cargo aboard the U-boat. Lansdale went on to say that the German material was sent to Oak Ridge where the isotopes were separated and put into the pot of material used to make America's first atom bombs.

Obviously Lansdale did not mean U
²³⁵
isotopes here since they are the final result of the separation process. The only fissile isotopes which can be separated from irradiated uranium are the range of plutonium isotopes from fissioned material bred in a working reactor or sub-reactor assembly. This would have made them panic, particularly if they knew how a small-scale German atom bomb was constructed. All that was needed for detonation would be an effective implosion fuse.

Natural uranium powder in its natural state is highly pyrophorous and ignites spontaneously on contact with air, but this would not require it to be packed in eighty small radioisotope containers. It is, however, the manner in which plutonium-enriched uranium powder would need to be transported.

The thickness of lead required to reduce the initial intensity of gamma radiation by a factor of ten is 1.8 inches. The thickness of the walls, lid and base of the lead containers described by Hirschfeld would have provided an interior volume for each container sufficient for about 19 kilos of uranium metal powder, multiply by eighty = 1520 kilos: divide by 750 kilos = enough for two small-scale atom bombs.

The Implosion Fuses

A final twist to the
U-234
story has been suggested.
¹³⁹
The German small-yield device could not have been properly detonated without an effective implosion fuse. For eighteen months the scientists at Los Alamos had failed to develop such a fuse. In October 1944 Robert Oppenheimer created a three-man committee to look into the problem. Luis Alvarez was on this team and became one of the heroes of the American A-bomb story when he solved it in the final days before the Trinity test at Alamogordo in July 1945.

The need was for a fusing system that could fire multiple detonators simultaneously. Harlow Russ, who worked on the plutonium bomb team, stated in his book
Project Alberta
that improvements were made to the detonator at the last moment. A new type of implosion fuse suddenly becoming available to the Manhattan Project gave a result four times better than expected at the Trinity A-test.

But did the real impetus for this success come from Luis Alvarez or German technology? Germany could not have detonated small-scale atom bombs without the most superior implosion fuse. According to the CI0S-BI0S/FIAT 20 report published by the US authorities in October 1946, by May 1945 Germany already had every kind of fuse known to the Americans –; “and then some”. Professor Heinz Schlicke, one of the passengers aboard
U-234,
was an expert in fuse technology. Infra-red proximity fuses were discovered to be aboard
U-234
on 24 May 1945, apparently as a result of the interrogation of Dr Schlicke in which he mentioned that he had fuses which worked on the principles that govern light. A memorandum by Jack H. Alberti dated 24 May 1945 states:

“Dr Schlicke knows about the infra-red proximity fuses which are contained in some of these packages. Dr Schlicke knows how to handle them and is willing to do so.”

Schlicke and two others were then flown to Portsmouth NH to retrieve the fuses. It is not suggested that these were the fuses used to explode the American plutonium bomb, but rather confirms that Schlicke knew more about fuses than the Manhattan Project did. From a transcript of a lecture given by Dr Schlicke to the Navy Department in July 1945, there seems to have been a close cooperation for some reason between Dr Schlicke and Luis Alvarez. And it is in the fact that the technological side of the Manhattan Project failed them that the real weakness of the American project is exposed.

CHAPTER 13

The Manhattan Project

T
HE MANHATTAN PROJECT was founded in order that the United States should have a nuclear capability in the event that Hitler developed the atom bomb. By the end of hostilities in Europe in May 1945 the United States did not have a bomb
which worked,
and, as that was the Project's raison d'être, it obviously failed. The American failure was in technology, for they were unable to devise an efficient implosion fuse.

How the Implosion Bomb Works

As any physicist will explain, the only economical way to detonate a Pu
²³⁹
or plutonium bomb is by the implosion method. The bomb core is made as a sub-critical sphere surrounded by a layer of non-fissile U
²³⁸
. A uniform layer of high explosive surrounds the tamper. When the thirty-two fuses are triggered simultaneously, the explosive detonates, creating a massive uniform pressure of millions of pounds per square inch which compresses the core to a supercritical density, causing the implosion. The implosion method is essential for plutonium-type bombs because the radioisotope Pu
²⁴⁰
, being more fissile than Pu
²³⁹
, would otherwise cause a premature detonation of the material known as a ‘fizzle'. The least speed required for assembly of the critical mass by implosion is in the region of 3500 feet/sec.

The U
²³⁵
bomb is more fissile than the plutonium device and the speed of assembly of the critical mass can be as low as 1000 feet/sec. For this reason an implosion fuse is not necessary for this type of bomb, but the amount of uranium material required is vastly greater.

In order to conceal the failure of the Manhattan Project, General Groves and his associates wanted people to continue to believe that ideally a plutonium bomb is detonated by an implosion fuse, while ideally the U
²³⁵
bomb is detonated by a ‘gun-type' device. The ‘gun-type' detonator is, of course, what they say was used to detonate the so-called ‘Thin Man' device used to devastate Hiroshima and which works in principle in the following manner: since one cannot assemble a critical mass without there being a reaction from it, two sub-critical lumps of highly enriched U
²³⁵
are kept apart until detonation when they are fired together within a howitzer barrel with a breech at each end. The supercritical mass assembles at a reasonably fast speed in sub-atomic terms and so achieves the explosion.

The Development of the Manhattan Project without an Implosion Fuse

Since the Americans had no effective implosion fuse to hand before the end of May 1945, no question ever arose of detonating a plutonium bomb in the preceding period. The U
²³⁵
bomb was the only possibility. Although the actual information regarding the Hiroshima bomb is probably still classified half a century later, it is known that the critical mass in the most favourable configuration as calculated by Richard Feyman was 50 kilos of U
²³⁵
. Robert Oppenheimer put it at double that. This is an awful lot of U
²³⁵
to expend in one bomb. Of course, nobody in his right mind would dream of putting half a field gun into a bomb to set it off if he had an implosion fuse. To separate 50 to 100 kilos of U
²³⁵
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 U
²³⁵
rationally needed for an implosion bomb would have been, at the most, just over ten kilos.

Explaining the Delays in Producing the U
²³⁵
Bomb

Early in 1944, the head of the Manhattan Project, General Groves, had indicated that he would have “several” U
²³⁵
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.