A Technological (With Some Real Science and Hardball Politics) Appendix to Postblogging Technology, November 1952: Ivy Mike

 

In what I was brought up to call the "Bethe Cycle," but which now requires a whole Wikipedia article to describe the various branchings, a presumed homogenous substrate of deuterium (hydrogen atoms with an atomic mass of 2 due to being composed of one neutron and one proton), combined with two electrons, is fused, after multiple intermediate states and the production of "catalysts" of atomic weight up to oxygen, into an atomic weight 4 helium atoms plus 2 electron neutrons and 7 gamma ray photons, with 26.7 MeV free energy.

The CNO cycle occurs in stars, particularly larger ones. It requires less energy to initiate than the naked fusion of two monoatomic hydrogen atoms (in other words, protons), but is also less efficient. Proton-proton fusions dominate stellar processes in smaller stars, but occur at statistically lower rates, causing these stars to burn less hot than larger stars, where the CNO process predominates. By the late 1930s, these facts were understood in vague outline, although given the fact that the neutrino was still at this point a theoretical particle, and its fundamental properties still obscure, physical science's understanding of the process was obviously still incomplete. Note that this not a question of pure scientific curiosity. Neutrinos can, like neutrons, collide with uranium and plutonium nucleii and initiate atomic fission. This happens at a small fraction of the rate of fission events due to free neutrons in atomic explosions, but given that chain reactions are exponential processes, it is something that a responsible weapon designer might want to keep in mind. Ha ha who are we kidding. 

In the IVY MIKE test explosion of  1 November, 1952, the American Atomic Energy Commission released 10.4 MT of free energy and a whole lot of radioactive fallout, plus a lot of politics. Considering that the explosion occurred  three days before the 1952 Presidential Election, we might on the one  hand say that the explosion occurred in a period of great political uncertainty, on the other hand note that while the media was invested in the idea of the election outcome being open, everyone expected Eisenhower to win; and on the third acknowledge that in fact the composition of the Senate was very much in question, and that while the GOP took a two seat majority in the voting, the defection of Oregon Senator Wayne Morse to sit as an independent, reduced that majority to a potential single vote, with Vice-President Nixon voting to break the tie. IVY MIKE gets a chapter to itself in Richard Rhode's Dark Sun, a discussion which seems to inform the Wikipedia article. Rhodes reports that Soviet scientists derisively referred to IVY MIKE as a "nuclear installation," which is fair enough. The world's first thermonuclear explosive device was anything but weaponised. It consisted, as all successful thermonuclear devices since, have consisted of, a fission bomb primary (a TX-1 based on the first miniaturised American atomic device) and a separated "secondary" consisting of a can of fusible light elements surrounding a plutonium "spark plug" containing tritium booster, and surrounded by a U238 tamper. 

Schematically, a shell of high explosives initiates the implosion of a mixed uranium-plutonium sphere (possibly incorporating some tritium booster which will undergo a preliminary fusion step) until a neutron emitter initiates fission, causing the emission of high energy photons, followed by a slower wave of neutrons and free protons. The advancing wave of photons fires a layer of plastic (not to be all atomical physicist on you, but that's just a way of saying carbon and hydrogen nucleii, or, in other words, uncomplicated light elements) surrounding the can, which initiates heating/compression in both the light elements and the core "sparkplug," which heats and compresses and begins releasing neutrons, which initiate fusion in the tritium booster incorporated in the sparkplug, which in turn produces more neutrons, which initiate fission in the sparkplug, which then imparts energy, momentum  and neutrons into the light elements in the can, until they begin to experience fusion along the CNO cycle, releasing yet more neutrons, which initiate fission in the external tamper. 

In other words, when we say "hydrogen," or "fusion" bomb, what we mean is "a chemical-(potentially fusion)-fission-fusion-fission-fusion-fission bomb.  About 775 of IVY MIKE's formidable energy output came from fission reactions, which to a modern historian of nuclear weapons might seem to make all this talk of a "hydrogen bomb" out to be  a bit of cheating. I don't think that this is particularly fair. The core problem lying behind getting the most bank for buck is to make the most efficient use of all the neutrons flying around. The Teller-Ulam device does that; so if we ever find a practical use for atomic devices (interstellar scale PROJECT ORION is the only one that comes to mind), we'll definitely want to be using Teller-Ulam devices with all the trimmings. Anything else would be making inefficient use of the scarce quantity of heavy elements the universe has given us!

Also, let's pause for a second and meditate on the fact that we came up with what is still our most (only?) effective interstellar drive 70 years-and-three-months-delayed ago. Ever accelerating technological progress into the future my left asscheek. 

So, anyway, speaking of, I of course put a lot of emphasis above on all the neutrons being freed from durance vile and, perhaps, allowed to go free to fly off and ionise living organic matter with what effects we cannot yet guess, on account of Sony being allowed to buy the X-Men franchise[!]. If not allowed to go free, and you'll pardon me for getting a bit comic book here, the neutron density in the middle of an exploding IVY MIKE hits 10 to the 23rd power neutrons per cubic centimeter instantaneous flux, corresponding to a gram of neutron per cubic centimeter. We know this, by the way, because IVY MIKE fall out included samples of the heaviest and most isotopes of plutonium, einsteinium, and fermium, indicating that the r-process had eventuated in the heart of the fireball. Astrophysicists are still looking for "sites" in nature spicy enough to experience the r-process, with favoured candidates being neutron star/neutron star (black hole) collisions, core-collapse supernovas being now suspected to be too placid. We need a lot of these exotic events to explain the quantity of r-processed-produced heavy elements in the universe, which might suggest that the universe is either a great deal more dangerous than we realise, or at least used to be. 

Or we don't know as much as we think we do. It turns out that fermium runs right up on something called the "neutron drip lines" where atom nucleii assembled by neutron capture dismantle themselves as quickly as they are built, which is why we haven't been able to make heavier transuranic elements in nuclear explosions yet, although the Blowed-Up-Real-Good crowd think we might be able to get reasonably stable heavy isotopes of copernicium out of a multiple-stage fusion explosion if we were ever to start doing those again. There's a great deal of obscurity to the r-process, which involves cramming a volume with beta particles as well as neutrons, with the possibility that if you can keep the beta particle influx high enough, long enough, you can prevent the dismantlings by occupying all the eligible spaces for the new particles to inhabit (this is already how regular r-process fusion works). So maybe we really will have unobtanium in quantities some day. 

All of this is kind of beside the point in the context of 1952. There was some suspicion that r-process nucleosynthesis would happen, although the theory predicting it had hardly got beyond the point of stating the necessary neutron flux. The IVY MIKE test site had been ringed with neutron targets, but these were mainly sited to confirm that the explosion included a fusion stage that lasted long enough to confirm the usefulness of the design. Filters were flown through the blast cloud, and it was in these that the heavy plutonium and novel transuranic isotopes were found, but that was not the specific intent of the flights, in which the USAF contrived to lose an F-84 and its pilot.  Given that IVY MIKE went off at twice the predicted power, albeit half the worst case scenario estimate, I would say that that was confirmed even before scientists began looking at their assorted tv-broadcast images of almost-immediately disintegrated monitoring cameras. 

IVY MIKE was not a viable bomb, and not just because of its size. I have been vague about the contents of the fusion can because the test used cryogenic, gaseous deuterium held at 20 degrees Kelvin, a completely impractical war load --although Los Alamos did engineer an "emergency" cryogenic bomb if the alternative, a load of lithium deteuride used in the Castle Bravo test, fizzled. That didn't happen, and it looks like I'll be talking about that on my 60th birthday, so we'll skip it for today. American nuclear scientists like to point out that the Russians, British and French all tried to skip directly to the more practical lithium deteuride warload, and that all of test blasts failed, although that's a bit harsh on the French. IVY MIKE was clearly a useful experiment from that point of view, informing the CASTLE BRAVO design so that the AEC could get it right(-ish) out of the gate.  

It was also a beyond industrially-goofy design, featuring a purpose-built (by the National Bureau of Standards) cryogenic facility in Boulder, Colorado, for making the deuterium; an American Car and Foundry-made "tank" for the explosion; cryogenic dewars made by Arthur B. Little, and a formidable level of mobilisation of the country's still-scarce supply of tanker-tractor-trailer rigs to get everything to the South Pacific in time. If you've ever been tempted to wonder why Gordon Dean became a director at Fruehauf after leaving the AEC (and, admit it, you've always wondered), that might be why. Rhodes also makes an interesting point in pursuing the theme of the difficulties of project management and design in getting IVY MIKE ready in time. His participant interviewees emphasise how hard it was to do these things when you could not talk on the phone or post Xerox copies around. They don't talk about calculators and other office machines, but that's what we have elections for. 

Rhodes spends a great deal of time in the next two chapters discussing the Rosenberg trial and executions; the Oppenheimer witch hunt, and some deliriously crazy comments from the archives from various American nuclear physicists who were sure that the Soviets were about to pull ahead of America on the fusion bomb front. It's a decent reminder that, HUAC Hollywood hearings aside, the frenzies of the so-called McCarthy era hit their peak in the first half of Eisenhower's first term. If everything in American politics is about race, the fact that the case that became Brown vs Board of Education had been referred to the Supreme Court, and everyone was expecting a desegregation order in the wake of the blatant collapse of "separate but equal," might have some subterranean relevance; but, in the end, it all comes down to the GOP being the party that it was, and Eisenhower perhaps less of the congenial moderate he has been portrayed as being. (

Or, perhaps, less able to direct his party. Truman was not above playing to the right, and the first and most important fact about IVY MIKE was Truman's decision not to delay the test until after the election. By suppressing an immediate announcement, the outgoing president at least managed to avoid playing politics, but he was too good a politician not to have taken in the unedifying spectacle of "Mr. Churchill's bomb" just a month before, as the British Conservative leader sat back and allowed the more unsavoury elements of the British press (hello, Economist!) turn Labour's effort into a Tory accomplishment. Eisenhower couldn't claim the hydrogen bomb as his own, but he could, as part of his general effort to well, govern after a Republican victory with a Republican Administration, go all out for hydrogen. Unfortunately for him, he inherited an almost uniquely-weak position in Congress. Wayne Morse left the Republican Party after Eisenhower selected Nixon as his running mate, and joined the Democrats in 1955. Meanwhile, no fewer than nine deaths and one resignation in the Senate left control of the upper chamber in the wind through the 1954 midterms. 

Willis Smith (D-NC; 66, coronary thrombosis, 26 June 1954)

Charles Tobey (R-NH; 73, coronary thrombosis, 24 July 1953)

Robert Taft (R-Oh; 64,  pancreatic cancer, 31 July 1953)

Dwight Griswold (R-Ne; 61, heart attack, 12 April 1954)

Clyde R. Hoey (D-NC; 77, unspecified causes, 12 May 1954)

Lester C. Hunt (D-Wyoming; 62, suicide, 19 June 1954)

Hugh Butler (R-Ne; 76, stroke, 1 July 1954)

Burnet R. Maybank (D-SC; 65, heart attack, 1 September 1954)  

Pat McCarren (D-Nevada; 78, heart attack, 28 September 1954)

This is quite the list. Both McCarran and Taft were legitimate giants of the Senate, and Lester C. Hunt's suicide, after being blackmailed by McCarthyites with the threat of public revelation of his son's arrest for homosexual activity, was a scandal at the time. (It is particularly upsetting to see conservative political thriller writer Allan Drury's career thrive on the basis of a thriller in which he switched the political orientations of the participants.) McCarthy was (finally) condemned by the Senate during the lame duck session, too late to prevent the Democrats taking the Senate back for the back half of Eisenhower's first administration. The United States has been more performatively unstable before and since, but for foreigners it was particularly unnerving period to see the country waving a hydrogen bomb around. 

In the end I can only point to Suez, the fall of Stalin, and the Great Leap Forward as evidence that there was something seriously wrong with people in the Fifties. The unprecedented death list makes me wonder if tobacco consumption might have had something to do with it? Anyway, we got away without a nuclear war, so that's good. Maybe the people who thought that the hydrogen bomb was a good idea because it was just so freaking scary actually had a point. 

 

(Remember how William F. Buckley used to whine about this?)