A nuclear test, especially in the remote Pacific, involves a lot more than setting up the device and pushing a button. At peak strength, Joint Task Force 132 involved more than 9,000 military personnel and more than 2,000 civilians (not counting those remaining “stateside”); upwards of a hundred water craft, ranging from an aircraft carrier and four destroyers to scores of small boats; and dozens of aircraft, ranging from fighter jets to single-engine four-seaters for island hopping within an atoll (quite like ones I flew much later to tow gliders). Two planes were lost, one of whose pilots was killed. And a lot of money was spent, about $66 million (some $600 million in 2015 dollars).{4}
Wheeler and others who were there just for the spectacle joined Task Force 132.1, the scientific arm of the task force, headed by the physicist Alvin Graves, who, back in Los Alamos, was the leader of Los Alamos’s J Division (the test division). Under his “command” (if that’s the right term) were more than 2,000 people, a mixture of civilian and military. (The task force had three other large “arms”: 132.2, headed by an Army Colonel, with 1,200 people at its peak; 132.3, headed by a Navy Rear Admiral, peaking at more than 5,000 people; and 132.4, headed by an Air Force Brigadier General, reaching some 2,500 people.) Graves’s 132.1 was responsible for assembling Mike, handling all of the cryogenics associated with liquid deuterium, and orchestrating the myriad experiments that would monitor its performance.{4}
As the picture on the next page makes clear, Mike, weighing in at 82 tons,{5} looked more like a small factory than a bomb. The cylinder of deuterium stood vertically, with the fission-bomb trigger at the top (of course not yet there in the picture). Diagnostic experiments (the various …EX’s developed at Los Alamos) were placed near and far, some adjacent to Mike, some as much as two miles distant.{6}
Mike’s mushroom cloud reached more than thirty miles into the stratosphere and spread to a width of some 65 miles, even overspreading some of the observers.{5} Those watching, after turning away from the intense light for a few seconds, could see the boiling cloud shooting up and out, and feel its intense heat (arriving as electromagnetic radiation). All in silence. Only after several long minutes did the sound arrive in the form of a shock wave followed by rolling thunder. Harold Agnew had this to say: “Something I will never forget was the heat. Not the blast… the heat just kept coming on and on. It’s really quite a terrifying experience because the heat doesn’t go off [as it does on smaller, kiloton shots].”{5}
So far as I know, John Wheeler didn’t put his reactions to the experience down in writing. When he spoke to us about it after his return from the Pacific, the only amazement he expressed was that an entire island could be obliterated. He seemed to take delight in that indicator of Mike’s power.[86] As for me, I remember having the fleeting thought, “It’s too bad it worked.” But mostly, like my Matterhorn contemporaries, I just felt satisfaction and pleasure that our efforts had contributed to success.
When Mike, in an instant, validated the Teller-Ulam idea and the Garwin design, it was 2:15 p.m. on Friday, October, 31, in Princeton. Those of us waiting for word at Matterhorn got the news of success in the form of an open, unclassified telegram from Wheeler. Whether that came the same afternoon or the next day I can’t now remember. What I do remember is that in an excess of caution, Wheeler phrased the news in such Delphic terms that we couldn’t tell for sure whether he was announcing success or failure. Since the general tone seemed upbeat, we surmised that the test had been successful. Confirmation came soon after.
Teller, too, used an open telegram to announce the success that he inferred by watching a seismometer in the basement of a geosciences building on the UC Berkeley campus. The explosion took place at 11:15 a.m. that Friday morning in Berkeley, and the seismic waves needed about 15 minutes to travel the more than 4,500 miles from Enewetak to Berkeley.[87] Teller, by his own account, sat in front of the seismograph in the dark, waited the quarter hour after the scheduled time of the explosion, and then “saw the dot on the seismograph screen do a little dance.” He quickly had the seismograph film developed and saw a trace that was “clear, big, and unmistakable,” about the magnitude that Teller’s geophysicist friend Dave Griggs had predicted. After a short conversation with Ernest Lawrence (inventor of the cyclotron and at that time director of the Berkeley Radiation Lab), Teller composed a three-word telegram, “It’s a boy,” and sent it off to the physicist Elizabeth Graves (wife of Alvin Graves) at Los Alamos. She and her colleagues at the lab had no trouble interpreting the message. Miraculously, according to Teller, his news of success got to Los Alamos before the classified telegram bearing the official news arrived from Enewetak.{9}
Just after Mike’s explosion, its yield was estimated at 10 megatons. This was later refined to 10.4 megatons[88] (some 700 Hiroshimas), half again as much as we had predicted.{10} One published estimate is that this energy came 23 percent from thermonuclear burning and 77 percent from fission, mostly in the uranium cylinder that housed the deuterium.{11}
Not long after John Wheeler got back to Princeton after the test, he said to me, “Ken, we must have overlooked some energy-generating effect.” My response was, “John, given all of the approximations we had to make, and our seriously limited computing power, we were lucky to get within 30 percent of the right answer.” (I was counting down from 10, not up from 7.) Now, in retrospect, I have to wonder if my calculations underestimated the yield because we (the Los Alamos and Matterhorn teams combined) underestimated the compression. Perhaps the complex interplay of plasma pressure, ablation pressure, and radiation pressure (see page 157), studied with care in recent years by the independent analyst Cary Sublette,{12} added up to more than we took into account. We will never know. But it remains true that we squeezed remarkably good answers from a computer that today would be considered laughably inadequate.
By the time of the Mike test, the nuclear arms race was well under way. Mike, and H bombs soon to follow, accelerated that race. In August 1953, less than a year after Mike, the Soviet Union exploded a 400-kiloton fission-fusion weapon of “layercake” design (see page 5),{13} and followed this up in 1961 with a 50-megaton behemoth[89] just to show it could be done.{14}) On March 1, 1954 (February 28 in the US), in the Castle Bravo test, the United States detonated an H bomb fueled with lithium deuteride that yielded 15 megatons.{15} (This device was enriched in Li6 but was still mostly Li7. The Los Alamos designers apparently—and very surprisingly—forgot that Li7, not just Li6, can contribute tritons to add to the thermonuclear burning. The predicted yield, accordingly, was less than half of the actual measured yield.{15} As I discussed on page 160 that extra yield had serious fallout consequences.)
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Gordon Dean, then Chair of the Atomic Energy Commission, also focused on this measure of Mike’s muscle when, in briefing President Truman the day after Mike, he reportedly said “The shot island of Elugelab is missing.”{7} (Other reports have Dean saying essentially the same thing to President-Elect Eisenhower later in November.{8})
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About 4,950 great-circle miles, or 4,600 straight-line miles through the Earth. The speed of the leading wave was about 5 miles per second.
88
What a tribute to the experimental physicists and engineers that they can figure the energy output of such a maelstrom to 1 percent.