bomb. Beginning shortly after the war, true computers started to become available, beginning with the ENIAC, IBM's SSEC, and the National Bureau of Standards SEAC. Because these machines were on the East Coast, many of the thermonuclear calculations actually took place far from Los Alamos. Although the first hydrogen bomb could have been developed without modern computers, such development would have been substantially delayed. Final Development Because hydrogen bombs require stellar temperatures to ignite the thermonuclear fuel, the only possible way to ignite a hydrogen bomb was by using an atomic bomb. For the development of the hydrogen bomb to go forward, fission weapons had to be improved. The two wartime fission devices, Fat Man and Little Boy, were crude prototypes not capable of being adapted for use in a hydrogen bomb. A new class of fission bombs had to be designed, built, and tested. This process took years. The first testing of new fission devices did not take place until 1948, with more design improvements following in 1950. Shortly after Truman's directive, hydrogen bomb research began to bear fruit. Edward Teller and Stanislaw Ulam came up with a promising design, radiation implosion, which was translated by Richard Garwin into a working design. Once the design concept was reviewed and approved, work began on constructing the Mike device and planning for a full-scale test at the Pacific Proving Ground in the Marshall Islands. Every atmospheric nuclear test was a major undertaking.