Hans Bethe - Manhattan Project

Manhattan Project

When the war began, Bethe wanted to contribute to the war effort. Following the advice of the Caltech aerodynamicist Theodore von Kármán, Bethe collaborated with his friend Edward Teller, then at George Washington University, on a theory of shock waves which are generated by the passage of a projectile through a gas. This work was later useful to researchers investigating ballistic reentry. Bethe also worked on a theory of armor penetration, which was immediately classified by the Army, making it inaccessible to Bethe, who was not an American citizen at the time.

During the summer of 1942, he served as part of a special session at the University of California, Berkeley at the invitation of Robert Oppenheimer, which outlined the first designs for the atomic bomb. Initially, Bethe was skeptical of the possibility of making a nuclear weapon from uranium. In the late 1930s, he wrote a theoretical paper arguing against fission, but was convinced by Teller to join the Manhattan Project. When Oppenheimer was put in charge of forming a secret weapons design laboratory, Los Alamos, he appointed Bethe Director of the Theoretical Division, a move that irked Teller, who had coveted the job for himself.

Bethe's work at Los Alamos included calculating the critical mass of uranium-235 and the multiplication of nuclear fission in an exploding atomic bomb. Along with Richard Feynman, he developed a formula for calculating the explosive yield of the bomb. After November 1943, when the laboratory had been reoriented to solve the implosion problem of the plutonium bomb, Bethe spent much of his time studying the hydrodynamic aspects of implosion, a job which he continued into 1944. In 1945, he worked on the neutron initiator, and later on radiation propagation from an exploding atomic bomb.

During the project, Klaus Fuchs, a German scientist spying for the Russians, was also in Bethe's division (often doing work which had originally been assigned to Teller). Like everyone else, Bethe had no knowledge that Fuchs was a spy.

When the first atomic bomb (an implosion design) was detonated in the New Mexico desert on July 16, 1945, at the Trinity test, Bethe's immediate concern was for its efficient operation, and not its moral implications. He is reported to have commented: "I am not a philosopher."