Everything that I have just described happens before the entire assembly blows itself apart. Fortunately for the bomb-builder, the big chunks of steel (nearly fifty tons of it) and uranium (perhaps five tons) are sufficiently “sluggish” to allow much of the fission and fusion to run their courses before everything is scattered to the winds. It doesn’t take many microseconds.
So, beginning in the fall of 1951, we at Matterhorn and our colleagues in Los Alamos had a clear view of the device whose behavior we wanted to calculate. We also had about six months in which to suggest design changes, if any, since Mike’s design would need to be frozen in the spring of 1952. One change that we all knew we wanted, eventually, was to use lithium-6 deuteride rather than deuterium as the thermonuclear fuel. But this was for the more distant future. Calculating the behavior of deuterium was easier and surer. The less uncertainty the better. For a test, all of the complexity of handling liquid deuterium and keeping it super-cold was worth the trouble.
In 1951 and 1952, we at Matterhorn and at least one Los Alamos scientist, Marshall Rosenbluth (like Garwin, another young star from Chicago), did carry out some calculations of thermonuclear burning for compressed “sausages” of lithium-6 deuteride, but this was with an eye to the future beyond Mike. Our principal focus remained on deuterium.
At the same time, it wasn’t fully ruled out that deuterium might be used in an actual deliverable weapon. Here is Dick Garwin’s laconic remark about what he did in the remainder of the summer of 1951 after designing Mike.{14} “After July 25th, I had some time at Los Alamos, and so I designed a deliverable, cryogenic version of Mike that would lie down rather than stand up.” (Mike was vertical.) No easy task. To meet Air Force requirements for dealing with air turbulence or hard landings, the bomb had to withstand forces up to eight “g’s” (eight times its weight). It had to be no heavier than a B-36 bomber could carry, about 35 tons. (It ended up closer to 20 tons.) And its load of deuterium had to remain frigid and liquid for many hours without mechanical refrigeration. On the ground, until takeoff time, it could be kept cold with ground-based cryogenic equipment. In the air, until its release or until the bomber returned to base, it was probably surrounded by a larger dewar filled with liquid hydrogen (ordinary hydrogen, not deuterium)—a thermos within a thermos, so to speak. Garwin had to design it so that during a long flight the amount of deuterium allowed to escape as gas would be a small fraction of the total and the pressure within the “sausage” would be tolerable. Garwin was up to the task. His design included even innovative bolts that minimized heat flow out of the stainless-steel dewar.
About half a dozen of these “recumbent Mikes” were actually built and were ready for deployment by January 1954.{15} They were called Emergency Capability Weapons, officially designated TX-16’s, and unofficially nicknamed Jugheads. But they had hardly come into existence before they were rendered unnecessary and obsolete by the successful test on March 1, 1954 of a solid-fueled H bomb, one containing, instead of deuterium, lithium deuteride enriched in the isotope lithium-6. This Castle Bravo device, called Shrimp (who knows why?), released fifteen megatons of energy, a thousand times that of the Hiroshima bomb and, in fact, more than twice what was predicted. Reportedly, the Los Alamos designers failed to take account of the significant contribution of the isotope lithium-7 to the thermonuclear reaction.{16}
Shrimp’s unexpectedly large yield plus an unanticipated wind shift produced the worst ever fallout damage from a U.S. nuclear test. Residents of Rongelap and Rongerik atolls in the Marshall Islands were evacuated (two days later, after already suffering significant radiation harm), and the crew of the Japanese fishing boat “Lucky Dragon No. 5,” who very unluckily found themselves in the downwind fallout path, experienced serious radiation sickness. One man died, and the world took notice.{17}
In my two years as an apprentice weapons designer, I worked hard at my job (and derived a good deal of satisfaction from it). Yet at the same time I managed quite a bit of relaxation. Apart from square dancing and folk dancing, much of the relaxation involved wheels. There were the weekend outings from Los Alamos with other young people, the drive with Mici Teller, Janette Wheeler, and John Toll to Los Angeles, and the motorcycle ride across the country. Over Thanksgiving 1950, I decided to get away from the lab for a few days by driving my Carryall to Tucson and enjoying the southern New Mexico and Arizona scenery along the way. The only activity I had planned for Tucson was reading books. (I knew no one there.) By chance I stopped for gas in Socorro, New Mexico, a town to which I would move twenty five years later. At the time of my Tucson trip, a gas station just south of town stood between the road and the air strip. It pumped gas for cars on one side and gas for planes on the other side. By the time I lived in Socorro, I had become a pilot (and drove a Volkswagen). At the airstrip there was no longer service for cars, but I took pleasure in gassing up the planes I flew next to where I had gassed up my car several decades earlier.
On one of my train trips from Princeton to Los Alamos in the winter of 1951–52—probably in December 1951—I recaptured the Carryall that I had left behind and drove it back to Princeton. Since it had no heater, I opted for a southern route—across the seemingly endless miles of Texas, then through Mississippi, Alabama, and Georgia, and on up through North Carolina and Virginia to Washington, DC, and on to Princeton. As it happened, the weather that week was odd. The Deep South was in a deep freeze. It was warmer in Illinois and Indiana than in Mississippi and Alabama. I drove most of the trip wearing winter gloves and a heavy coat.
Not long after reaching Princeton, I skidded on the ice on Prospect Street and slid into the rear of a large truck. The result was a baseball-sized hole on the right side of the Carryall that thereafter funneled rain and snow onto the right knee of any passenger on the far right of the front seat. Some of my passengers took this brush with nature stoically. Some slid across the seat to the left. A few asked politely to get out.
Several months after the encounter with the truck, I was driving to Washington, D.C. on a rainy night with John Toll on board. On a stretch of four-lane highway I lost control of the car and it spun around through 180 degrees. Toll, who had been resting on the mattress in the back of the Carryall, was jarred awake. He said later, “I sat up and looked out and wondered why we were going backward.” I got the car pointed in the right direction and we proceeded without further incident to Washington—where Toll’s family lived and where I had a date with a computer. The gods are kind to the young.
The last I heard of the Carryall it was in Winnipeg. In the spring of 1953 I sold it (for $75) to my fellow graduate student and then-roommate Ken Standing, a Canadian who went on to a distinguished career as an experimental physicist. Ken drove it to his new job in Winnipeg where, I hope, he bought a heater for it.
Chapter 15
Climbing Matterhorn
For some reason, the number $20,000 has stuck in my head over the years. It is the amount I heard that the AEC was paying the National Bureau of Standards per month for the graveyard shift on the SEAC. That was about 50 times my salary at the time, so it was memorable.