Chemist Don Hornig kept his hand on the switch to stop the test
IN the spring of 1944, my life became a mystery novel. I was working at the High Explosives Research Laboratory at the Woods Hole (Mass.) Oceanographic Institute when I got a call from Harvard Prof. George Kistiakowsky, a scientist whom I greatly admired. He was working at a new laboratory, he said, and needed me badly.
That was all I needed to say yes. I was advised to leave as soon as possible, without telling anyone, and report to 109 East Palace Ave., Santa Fe, N.M., where I would be given further instructions.
At Santa Fe, I was directed to Los Alamos, a former boys' school on a mesa at the base of the Jemez Mountains. I found that I was to join Kistiakowsky and others under J. Robert Oppenheimer working on the Manhattan Project, the crash program to build an atomic bomb. I was 23 years old, a physical chemist of limited experience with a newly acquired PhD who had done research on shock waves produced by large explosions.
To maintain secrecy, the project's overall director, Maj. Gen. Leslie Groves, insisted on strict compartmentalization: Scientists would have access to information only on a need-to-know basis.
Oppenheimer persuaded Groves that the only hope of resolving the enormous scientific and technical problems facing his group was to let scientists discuss these challenges with one another.
When I arrived in May 1944, two ways to create a critical mass were being considered. The first used a high velocity gun to shoot two sub-critical chunks of enriched uranium (U-235) together. This would not work with plutonium, though, which requires much faster assembly to avoid a premature explosion. The solution proposed was ''implosion'': Surround a subcritical shell of plutonium with explosive charges (called ''lenses'') shaped to focus the detonation waves toward the center of the plutonium shell and drive all segments together.