Command and Control

A naval officer at the Armed Forces Special Weapons Project suggested that the yield of a nuclear weapon accident should never exceed the explosive force produced by four pounds of TNT. The four-pound limit was based on what might happen during an accident at sea. If a nuclear detonation with a yield larger than four pounds occurred in the weapon storage area of an aircraft carrier, it could incapacitate the crew of the engine room and disable the ship. Los Alamos proposed that the odds of a yield greater than four pounds should be one in one hundred thousand. The Department of Defense asked for an even stricter definition of one-point safety: odds of one in a million.

The likelihood of a Mark 28 producing a large detonation during a plane crash or a fire, Osborne now thought, was uncomfortably high. The one-point safety tests conducted in Nevada had assumed that the most vulnerable place on a weapon was the spot where a detonator connected to a high-explosive lens. That’s why the tests involved setting off a single lens with a single detonator. But Osborne realized that nuclear weapons had an even more vulnerable spot: a corner where three lenses intersected on the surface of the high-explosive sphere. If a bullet or a piece of shrapnel hit one of those corners, it could set off three lenses simultaneously. And that might cause a nuclear detonation a lot larger than four pounds of TNT.

A new round of full-scale tests on the Mark 28 would be the best way to confirm or disprove Osborne’s theory. But those tests would be hard to perform. Ignoring strong opposition from the Joint Chiefs of Staff, President Eisenhower had recently declared a moratorium on American nuclear testing. He was tired of the arms race and seeking a way out of it. He increasingly distrusted the Pentagon’s claims. “Testing is essential for weapons development,” General Charles H. Bonesteel had argued, succinctly expressing the military’s view, “and rapid weapons development is essential for keeping ahead of the Russians.” But Eisenhower doubted that the United States was at risk of falling behind. The Air Force and the CIA had asserted that the Soviet Union would have five hundred long-range ballistic missiles by 1961, outnumbering the United States by more than seven to one. Eisenhower thought those numbers were grossly inflated; top secret flights over the Soviet Union by U-2 spy planes had failed to detect anywhere near that number of missiles.

Despite the Democratic attacks on his administration and dire warnings of a missile gap, President Eisenhower thought it was more important to preserve the secrecy of America’s intelligence methods than to refute his critics. The nuclear test ban was voluntary, but he hoped to make it permanent. In the words of one adviser, Eisenhower had become “entirely preoccupied by the horror of nuclear war.” The harsh criticism of his policies — not just by Democrats but also by defense contractors — led Eisenhower to believe in the existence of a “military-industrial complex,” a set of powerful interest groups that threatened American democracy and sought new weapons regardless of the actual need.

The Air Force was in a bind. The hydrogen bomb scheduled to become its workhorse, deployed at air bases throughout the United States and Europe, might be prone to detonate during a plane crash. And full-scale tests of the weapon would violate the nuclear moratorium that Eisenhower had just promised to the world. While the Air Force and the Atomic Energy Commission debated what to do, the Mark 28 was grounded.

Norris Bradbury, the director of Los Alamos, recommended that a series of tests be secretly conducted. The tests would be called “hydronuclear experiments.” Mark 28 cores containing small amounts of fissile material would be subjected to one-point detonations — and more fissile material would be added with each new firing, until a nuclear yield occurred. The largest yield that might be produced would be roughly equivalent to that of one pound of TNT. None of these “experiments” would be done without the president’s approval. Eisenhower was committed to a test ban, disarmament, and world peace — but he also understood the importance of the Mark 28. He authorized the detonations, accepting the argument that they were “not a nuclear weapon test” because the potential yields would be so low. At a remote site in Los Alamos, without the knowledge of most scientists at the laboratory, cores were detonated in tunnels fifty to one hundred feet beneath the ground. The tests confirmed Osborne’s suspicions. The Mark 28 wasn’t one-point safe. A new core, with a smaller amount of plutonium, replaced the old one. And the bomb was allowed to fly again.

* * *