 Neddermeyer discarded Serber and Tolman's initial concept of implosion as assembling a series of pieces in favor of one in which a hollow sphere was imploded by an explosive shell. He was assisted in this work by Hugh Bradner, Charles Critchfield, and John Streib. L. T. E. Thompson was brought in as a consultant, and discussed the problem with Neddermeyer in June 1943. Thompson was skeptical that an implosion could be made sufficiently symmetric. Oppenheimer arranged for Neddermeyer and Edwin McMillan to visit the National Defense Research Committee's Explosives Research Laboratory near the laboratories of the Bureau of Mines in Bruceton, Pennsylvania (a Pittsburgh suburb), where they spoke to George Kistiakowsky and his team. But Neddermeyer's efforts in July and August at imploding tubes to produce cylinders tended to produce objects that resembled rocks. Neddermeyer was the only person who believed that implosion was practical, and only his enthusiasm kept the project alive.
