The First War of Physics (20 page)

Speer got the message:

Rather put out by these modest requests in a matter of such crucial importance, I suggested that they take one or two million marks and correspondingly larger quantities of materials. But apparently more could not be utilised for the present, and in any case I had been given the impression that the atom bomb could no longer have any bearing on the course of the war.

Convinced that a bomb was outside their reach within the likely timeframe of the war, the Uranverein physicists had settled for relatively modest funding to continue their work on a nuclear reactor.

The physicists’ actions at this critical turning point in the German programme require careful interpretation. From the very beginning, some in the group – and Heisenberg in particular – had sought to ‘make use of warfare for physics’. The Uranverein represented an opportunity to continue research on nuclear fission at the military’s expense and with relatively little interference. Every attempt to build the project into a focused, structured programme directed towards military ends had been gently rebuffed. When pressed by Schumann, the physicists working outside Berlin had in September 1939 refused to relocate to the Kaiser Wilhelm Institute for Physics, preferring to continue their academic work at their various institutes around the country. Consequently, the programme had remained fragmented and relatively unfocused.

Like many in German industry and society, the physicists had embraced the Nazi war as a means to an end, the end in this case being the furtherance of their own academic careers and positions. Most in the Uranverein were not Nazis. They were ready to take whatever personal advantages could be gained from the war, but they had no real wish to be part of it. For these physicists, the Uranverein represented an opportunity to make
what they saw to be a valid contribution to the German war effort, with the potential promise of a decisive weapon in some ill-defined future, and without the personal risks associated with direct military service.

A request to Speer for millions of marks would have meant a highprofile military project, and a commitment to deliver an explosive device that could have an influence on the course of the war to a regime that was not known to be forgiving in the event of failure. For Heisenberg this must have been quite a gamble. He had dangled the prospect of ‘explosives more than a million times more effective that those currently available’ in front of an audience of high-ranking military advisers and Hitler’s Reichsminister for Armaments. He had then deftly downplayed the potential for a weapon, citing the huge technological challenges that stood in the way. Then, finally, he had bid for a level of funding that was perfectly reasonable for the next step in a long-term research project, but completely insufficient to fast-track a war project designed to overcome the technological challenges and build a new ‘wonder-weapon’.

There were still risks, of course. Successful construction of a working nuclear reactor would mean that element 94 could be produced, though perhaps given the scale of the experiments envisaged, the material would not be produced in the kinds of quantities required to build a bomb. Heisenberg’s gamble appeared to have paid off. The work would continue under the auspices of the Reich Research Council, a civilian organisation, and there would be little or no further reference to the possibility of a bomb, at least among the core group of physicists working under Heisenberg. The German atomic bomb project, if it had ever really existed as such, was now at an end.

Hitler had received several ‘Sunday-supplement’ accounts of the potential for an atomic bomb from various non-expert and often ill-informed advisers, and Speer was wary of having his master’s imagination captured by an idea that was plainly far from becoming a reality any time soon. On 23 June Speer advised Hitler that the nuclear programme might produce some useful things in the long term, but there was no decisive super-weapon in the offing. The German military turned its attentions elsewhere.

Success with ‘atomic fission’

On the day that Speer advised Hitler of the rather limited prospects for the German nuclear programme, the experimental pile L-IV exploded. Heisenberg and Döpel narrowly escaped serious injury, or death.

The pile had been sitting in water for more than twenty days, and had developed a leak. It began to emit a stream of bubbles which Döpel ascertained contained hydrogen gas, formed by a chemical reaction between water and the uranium metal inside the sphere. Döpel hauled the sphere out of the water tank. When a laboratory technician opened one of the sphere’s inlet valves, air rushed in, igniting the uranium powder inside which then sprayed outwards.
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The aluminium began to melt, igniting more uranium powder. Döpel and a couple of the technicians managed to put out the fire and gingerly lowered the sphere back into the water. Heisenberg was summoned to inspect the apparatus. Satisfied that everything was under control, he promptly left to deliver a seminar.

But the sphere was not under control. Some time later Heisenberg was called back to the laboratory and watched with Döpel as the sphere first shuddered, then visibly swelled. The physicists ran for the door, emerging from the laboratory seconds before an explosion tore it apart.

They had survived, but they had lost their laboratory, the powdered uranium metal and the heavy water. The chief of the local fire brigade remarked on Heisenberg’s success with ‘atomic fission’. Rumours spread, and evolved into reports that several German physicists had been killed in the accidental explosion of a uranium bomb.

Hurry up – we are on the track

Despite the loss of the Leipzig laboratory, Heisenberg had reasons to be satisfied. The reactor experiments were heading in the right direction. The meeting with Speer had concluded favourably in that the importance of nuclear physics had been recognised and modest funding had been agreed. ‘No orders were given to build atom bombs,’ he later wrote, ‘and none of us had cause to call for a different decision.’ He had been appointed director at the prestigious Kaiser Wilhelm Institute for Physics, which he regarded as a personal victory over ‘Aryan’ physics. The continuation of the nuclear programme as a civilian research project left him free to continue his academic research and build his professional and social standing in Berlin.

Heisenberg’s conscience may have been clear, but the bargain he had struck still exerted legacy effects. It is one of the great ironies of the first war of physics that, at precisely the moment the German atomic bomb project formally ceased to exist, the palpable fear of a German atomic weapon that had continued to build in Britain and the United States was about to be translated into action. The race to build the atomic bomb, such as it was, was soon to claim its first lives.

The most disturbing news came from Szilard in America. Through various contacts he had picked up the message that the German physicists had already succeeded in establishing a self-sustaining chain reaction which, by Szilard’s own reckoning, put them a year ahead of the Allied programmes. Wigner later recalled receiving a telegram from Houtermans in Switzerland urging them to ‘Hurry up. We are on the track’, but the source of Szilard’s message was not Houtermans, though it did come from Switzerland.
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Szilard alerted Compton, and during July 1942 Compton wrote letters to Conant in Washington:

We have become convinced that there is a real danger of bombardment by the Germans within the next few months using bombs designed to spread radio-active material in lethal quantities … Apparently reliable information has reached us to the effect that the Germans have succeeded in making the chain reaction work. Our rough guess is that they may have had the reaction operating for several months.

The warning was passed to the Directorate of Tube Alloys via the American embassy in London. It contradicted the intelligence that had been gathered by the SIS, which indicated that German nuclear research was still very much ‘in progress’. The British sources were varied, and included reports from Rosbaud in Berlin, conversations between Brun and Uranverein physicists Hans Suess and Karl Wirtz who had separately visited the Vemork plant in July 1942, and comments made by Hans Jensen to several physicists in Denmark and Norway, including Bohr. All the intelligence pointed to a continued effort to develop a reactor, and that the German physicists had yet to succeed in establishing a chain reaction.

Nevertheless, the possibility of warfare using weapons designed not necessarily to cause destruction but to render an area radioactive and therefore inhospitable had to be taken seriously. Alan Nunn May, a Cambridge-educated physicist now working with Chadwick, was asked to assess the feasibility of such a weapon. He concluded that the prospects for such radiation weapons were very limited.

Operation Freshman

The concerns that had been raised about German progress nevertheless brought into sharp relief discussions that had been going on within the Directorate of Tube Alloys and the British military authorities since April. The dependence on heavy water from the Vemork plant represented a significant vulnerability for the German nuclear programme. Sabotage by Brun and other engineers at the plant had certainly limited production (of the five tons that Heisenberg had estimated to be required, by June 1942 less than a ton of heavy water had actually been delivered). However, it was obvious that this kind of sabotage could not be sustained indefinitely. Better to restrict German access to heavy water altogether by taking the plant out of commission.

Discussions about plans to attack the Vemork plant had begun in the spring of 1942 and had thus far involved the War Office, Chiefs of Staff, Combined Operations, the SIS, the SOE, the Foreign Office and the Norwegian government-in-exile. The discussions had produced hundreds
of memos and telegrams and little else. The idea of an early strike against Vemork was shelved in May when it was realised that, in the land of the midnight sun, there were at this time of year only a few hours of darkness available in which to carry out a sabotage operation.

Any attack would require a detailed understanding of the layout of the plant. At Tronstad’s request, Brun obtained plans and photographs of the plant which were reproduced in microphotographs with the aid of a friend in Rjukan. The microphotographs were then concealed in tubes of toothpaste and couriered to Tronstad via Sweden.

Churchill had been briefed on the discussions and, shortly after he returned from a strategy meeting with Roosevelt in Washington in June 1942, the Vemork plant was identified as a top priority target. In July the war cabinet issued a memo to Combined Operations, under the leadership of Lord Louis Mountbatten, requesting the examination of options for an attack on the plant sufficient to destroy all existing stocks of heavy water, the plant’s electrolysis cells and the adjacent power plant.

Combined Operations turned to the SOE for help. In truth, there were few options. These included sabotage using Norwegian patriots already working at the plant, agents that could be infiltrated into the plant or a party of SOE saboteurs, a Combined Operations attack using British commandos delivered using gliders or hydroplanes, or a bombing raid mounted by the RAF. All of these options were highly precarious and fraught with considerable risks.

Tronstad argued strongly against a bombing raid. He feared that bombing would be too indiscriminate. ‘The valley is so deep,’ he said, ‘that throughout the winter the sun’s rays never reach Rjukan’s streets. If stray bombs were to hit the liquid-ammonia storage tanks at the bottom of that valley, the whole Rjukan population would be in the gravest danger.’ Given the remoteness of the plant, any British commandos landed in the region would have great difficulty getting out again, turning a sabotage operation into a potential suicide mission. Any actions taken by locals risked German reprisals against the local population. Tronstad thought that Brun might be willing to scale up his sabotage activities, but Brun was known to be away from the plant.

Discussions dragged on through August and September. In the meantime, the ranks of Norwegian patriots recruited to the SOE’s Norwegian section, under the command of Colonel John ‘Jack’ Wilson, were scoured for potential candidates for the raid. Ten men were identified, and the SOE began putting together plans for landing a small advance party onto Norway’s notoriously inhospitable Hardanger Plateau – 3,500 square miles of virtually uninhabited, frozen wilderness about 3,000 feet above sea level, on the edge of which the Vemork plant was perched.

One of those selected was Knut Haukelid, who subsequently provided a detailed account of the training that he and his comrades received in various SOE Special Training Schools – referred to by the Germans as the ‘International Gangster School’. ‘We not only learned to force locks and break open safes,’ he wrote, ‘but we were taught the use of explosives in all circumstances … We learned to use pistols, knives and poisons, together with the weapons nature had given us – our fists and feet.’

An accident with a loaded pistol during a field exercise ruled Haukelid out of the advance party, which was given the codename Grouse, led by Second Lieutenant Jens Anton Poulsson. The Grouse party included Claus Helberg, Knut Haugland and Arne Kjelstrup. Poulsson, Helberg and Kjelstrup were all natives of Rjukan (Poulsson and Helberg had been school classmates, Kjelstrup had been born in Rjukan but had lived most of his life in Oslo). All four were hardened ‘hillmen’, intimately familiar with the survival challenges of the Hardanger wilderness.

After much vacillation, a decision on the plan of attack – codenamed Operation Freshman – was finally made by Combined Operations on 13 October 1942. The Grouse party was to reconnoitre the area and identify a suitable landing site for a further party of glider-borne commandos, comprising Royal Engineers of the First Airborne Division, who would carry out the raid. After destroying the heavy water plant, the commandos were expected to make their way on foot to the Swedish border, about 250 miles away.

Both Wilson and Tronstad had argued strenuously that the plan was ill-conceived and susceptible to failure. Norway was unsuitable for a glider operation, over a towing distance longer than had ever been attempted,
even in daylight. Success would demand very favourable weather conditions, something that could not be guaranteed. They were overruled. Tronstad sent word to Brun that he should leave for Britain without delay.