On 16 October 1964, China detonated a 22-kiloton nuclear weapon device at the Lop Nur test site, becoming the fifth nuclear power state in the world and the first Asian nation to possess nuclear capability. The United States had been monitoring the Lop Nur site for some time and they were aware that a test was imminent. What worried them was the unknown. How many more nations are working on nuclear weapons without their knowledge? Which country would be next to develop nuclear weapons capability? How easy or difficult it would be to accomplish that? The proliferation of nuclear-armed states was a matter of concern for it could create an unstable and perilous world. During a 1963 press conference, President John F. Kennedy predicted that in the 1970s there would be as many as 15 to 20 nuclear powers, which would pose the “greatest possible danger and hazard.”
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In order to better gauge the threat of nuclear proliferation, the Lawrence Radiation Laboratory in Livermore, California, wanted to ascertain what it would take for a determined group of extremely brilliant individuals with no access to classified research to build a bomb. They called it the “Nth Country Experiment.”
The Laboratory hired three physicists—Dave Dobson, David Pipkorn, and Rob Selden— who recently received their Ph.Ds in physics but had little to no experience with nuclear physics. They were tasked to design a credible nuclear weapon with a “militarily significant yield” using only information that’s available under public domain. The experiment commenced in May 1964, but Pipkorn soon left leaving only Dobson and Selden to complete the task, which they did in less than three years.
“It's a very strange story,” Selden told The Guardian in an interview in 2003. Back then, Selden was a lowly 28-year-old soldier recently drafted into the army, when he received a message that Edward Teller, the father of the hydrogen bomb and a commanding figure in the US atomic programme, wanted to see him. “I went to DC and we spent an evening together. But he began to question me in great detail about the physics of making a nuclear weapon, and I didn't know anything. As the evening wore on, I knew less and less. I went away very, very discouraged. Two days later a call comes through: they want you to come to Livermore.”
Dave Dobson in 1964.
Rob Selden
Dave Dobson was inducted into the project in a similarly surreal fashion. The institution's head offered him a job promising “interesting” work but refused to divulge details unless he accepted the job. He only learned afterwards what he was expected to do.
The duo was banned from consulting classified research but anything they produced—diagrams and notes—automatically became classified. Because the bomb that they were designing wouldn't actually be built and detonated, they had to come up with a way to test their design as they went along to rectify mistakes and make modifications. For this the authorities as Livermore devised an “arcane, precisely choreographed ritual”, where the designers had to explain at length, on paper, what part of their developing design they wanted to test, and then pass the documents to experts. The results would come back after a few days, but Dobson and Selden would have no way of knowing whether these results were obtained from real tests or hypothetical calculations.
Dobson's knowledge of nuclear bombs was rudimentary at best. He had never heard the terms Trinity, Little Boy, or Fat Man. His only brush with nuclear education was an exhibit he saw where a model of a chain reaction was built using mousetraps and ping pong balls. Seldan was equally clueless. He found a book on the Manhattan Project that culminated in America's development of the bomb. “It gave us a road map,” Dobson said. “But we knew there would be important ideas they'd deliberately left out because they were secret.”
One key decision they had to take early in the experiment was deciding which type of design to choose—the gun-style, like the one dropped on Hiroshima, or the technically more challenging implosion style, that was dropped on Nagasaki. The gun type device was easy but needed more fissile material, whereas the implosion type was difficult to design hut needed less material. Because procurement of material was most certainly the hardest part (the physicists didn’t actually have to procure material, they just assumed they had a requisite amount), Dobson and Selden chose the implosion type.
Implosion-type nuclear device. Image: High Point University
“Obtaining the fissile material is really the major problem - that drives the whole project,” said Selden. “But the process of designing the weapon - I'm always careful to point out that many people overstate how easy it is. You really have to do it right, and there are thousands of ways to do it wrong. You can't just guess.”
Eventually, towards the end of 1966, two and a half years after they began, the physicists submitted a document describing, in precise engineering terms, what they proposed to build and what materials were involved. The whole work was so detailed “that this thing could have been made by Joe's Machine Shop downtown,” said Selden.
For the next two weeks, Dobson and Selden were grilled by the upper echelons of Washington, who questioned them about their work and how they knew what they knew. All this time Dobson and Selden were kept in the dark about whether their three years of labor were fruitful. Finally, after a presentation at Livermore, a senior researcher named Jim Frank pulled them aside and told them that the experiment was a resounding success. Had it been constructed, Jim told them, it would have made a pretty impressive bang as large as Hiroshima.
“It's kind of a depressing thing to know, that it could be that easy,” Dobson said.
Selden and Dobson proved that there is enough freely floating information in libraries and on the internet using which any technically-savvy person with the right resources could create an atomic bomb, and this include terrorists. “Back in the 50s, there were two schools of thought - that the ideas could be kept secret, and that the material could be locked up. Now? Well, hopefully the materials can still be locked up, but we all have our doubts about that,” Dobson said.
After successfully completing the Nth Country Experiment, Selden stayed in the military and became a member of the US Air Force Scientific Advisory Board. Dobson, on the other hand, was so disturbed by his experience at Livermore that he left the sector entirely. “It was one thing to work on a project which was hopefully going to illuminate the decision makers so they could see that weapons were easily designed,” he says. “It was a rather different thing to go in and say, 'OK, for example, let's make a thermonuclear device that's only four inches in diameter.' That's an acceleration of the arms race, and I didn't really want to do that.”
References:
# How two students built an A-bomb, The Guardian
# 1960s "Nth Country Experiment" Foreshadows Today's Concerns Over the Ease of Nuclear Proliferation, the National Security Archive
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