Richard Rhodes
Dark Sun: The Making of the Hydrogen Bomb
Summary by Michael McGoodwin, prepared 1998

USA's Ivy Mike 10 Megaton thermonuclear detonation, Enewetak Atoll, 1 November 1952
USA's Ivy Mike 10 Mt detonation, Enewetok Atoll, 1 November 1952
(photo from HiRes

Acknowledgement: This work has been summarized using the Simon & Schuster 1995 edition (one of the Sloan Technology Series books).  Quotations are for the most part taken from that work, as are paraphrases of its commentary.   

Overall Impression: This book lifted the veil of past secrecy and mystery regarding many of the details of the development of thermonuclear (fusion) weapons--devices  which so imperil our futures today.  The earlier book The Making of the Atomic Bomb by Richard Rhodes is also of interest and tells the story of the earlier development of fission weapons.

Note: some clarifications and corrections have been added in [square brackets] from Nuclear Weapons Frequently Asked Questions (FAQ) by CAREY SUBLETTE at & from other sources

Chapter 1

Spontaneous fission of Uranium (U) discovered 1940 Georgi Flerov and Konstantin Petrzhak. [FAQ & Misc.: for U235, half-life is 710 million years (predominantly alpha), specific activity 2.1 microCi/g {calc. via Radiation Health Handbook}, fission fraction 7.0E-11, spontaneous fission rate is 0.16 fissions/sec-kg {inconsistent data} generating 0.5 neutrons/sec-kg; for U238, half life is 4.51 billion years (predominantly alpha), specific activity of 0.333 microCi/g, fission fraction 5E-7, spontaneous fission rate is 35x higher than U235 at 5.51 fissions/sec-kg; the specific activity of natural uranium is 0.67 microCi/g (split almost 50/50 between the rare U-234 isotope {.214} and U-238 {.333}]. News of 1939 German discovery of fission of U under neutron bombardment (Hahn & Strassman) reaches USSR's founder of the Inst. of Physics and technology "Fitztech", Abraham Ioffe, in 1939. He selects Igor Kurchatov to spearhead a new nuclear physics program. The possibility of making a bomb using a nuclear chain reaction with fast neutrons is obvious to them and to Robert Oppenheimer, Enrico Fermi, Leo Szilard, Rudolf Peierls, etc. [FAQ: fission of U releases 180 MeV immediately and 2.52 neutrons for U235 or 2.95 neutrons for Pu 239. Capture of even a slow n by U235 always leads to fission ("slow fission" of "fissile" material), whereas U238 must be struck by a fast neutron with KE > 1MeV to undergo fission ("fast fission" of fissionable material). The kinetic energy of fission neutrons varies from 0.5 MeV to more than 4 MeV, with a most probable energy = 0.75 MeV, the average (and median) is 2 MeV. ]. A U bomb requires separation (enrichment) of U235 from U238 (i.e., enriched from usual 0.7% to 80% or more), since a fast neutron chain reaction in natural uranium is not possible. Other interested Soviet scientists include Lev Landau, Peter Kapitza.

Khariton and Zeldovich describe in 1939-40 the requirements for a reactor: In contrast to a bomb, a reactor uses "slow" neutrons (slowed below U238 neutron capture resonance of < 25 ev by collisions with a moderator to capture excess neutrons, either deuterium [ordinary hydrogen captures too many slow neutrons] or graphite). It can be fueled with natural Uranium (or with U235 enriched to 1.3% using ordinary water as a moderator). The molar heat of U is c. 50,000,000 that of coal. Separation for HEU production requires gaseous diffusion [FAQ: the most extensively used method; has a separation factor per stage of 1.00429 for uranium. A large number of cascade stages are needed], gas centrifuge [or electromagnetic separation (Calutron, like a mass spectrometer, discontinued in 1946), thermal diffusion, aerodynamic (nozzle/vortex) enrichment, etc.].

With outbreak of war of USSR with Germany June 1941, Fitztech moves to Kazan. Georgi Flerov (December 1941) estimates that an atomic bomb with 2.5 kg of U235 could yield 100 kilotons TNT equivalent (KT) [FAQ: critical mass for 93.5% HEU U-235 are 48 kg total weight for bare sphere, 18.4 kg if surrounded by a 10 cm thick natural U8 tamper, or 14.1 kg if surrounded 10 cm beryllium tamper (acts to reflect neutrons). Critical mass of bare Pu239 sphere is 10.5 kg and 4.4 kg with natural U reflector. Pu-239 specific activity is 0.061 Ci/gm, predominantly alpha emission. Energy content of TNT is 980-1100 calories/g; megatons were redefined to be exactly 10^12 calories (4.186x10^12 joules) yielding 1000 cal/g. Fast neutrons follow a mean free path before fission of typically 13 cm traveled in 10 nanoseconds (one "shake"), and in 560 nanoseconds the reaction has proceeded through 56 generations essentially to completion. (1 MeV neutrons have mean free path for fission of 16.5 nsec in U-235, 12.7 in Pu-239). The tamper slows the rate of expansion, reflects some neutrons, and generates some of its own from fast fission of U-238].

Chapters 2-5

Spies and Soviet agents are active in the US and England, accelerating the diffusion of knowledge about nuclear weapon technology: Whittaker Chambers, Ruth Kuczynski, Harry Gold, Guy Burgess, Anthony Blunt, Donald Maclean, Kim Philby, John Cairncross, and Klaus Fuchs (a German communist who works in England initially under Peierls). The Lend-Lease program creates a free conduit of equipment and materials from US to USSR during the war, through which large quantities of industrial information and even strategic metals pass.

Flerov urges Stalin to develop the atomic bomb April 1942. Stalin concurs (May 1942), orders stepped-up spying, and puts Kurchatov in charge of development (early 1943). Lavrenti Beria is Stalin's head of secret police, deputy prime minister during the war, and becomes the non-scientific director of the bomb project. Vannevar Bush promotes the bomb project to Roosevelt early 1942-- he responds enthusiastically to proceed.

Battle of Stalinigrad ends Jan 1943, turning the tide in the USSR's favor. Kurchatov learns through espionage in 1943 (probably through Klaus Fuchs) of the preference of gaseous diffusion U separation technique in the US, the existence and potential of Pu-239 (discovered by Glenn Seaborg et al in 1941 from cyclotron synthesis, having a fission cross section for fast neutrons 3.4x that of natural U, being much easier to separate chemically, initially called eka-osmium), the heterogeneous reactor fuel design (i.e., rods embedded in moderator as conceived by Fermi and Szilard in 1940 rather than a homogeneous fluid), the possibility of breeding Pu-239, and the use of deuterium to make natural U reactor possible. He establishes Lab No. 2 in Moscow, gets a cyclotron. 

Development of US reactors at U Chicago (Fermi's CP-1, natural U and graphite, operational Dec. 1942), Argonne Forest (CP-2, by 1943), Oak Ridge (for Pu production and gaseous diffusion), as well as deuterium distilleries.

Chapter 6

Fuchs conveys important details of bomb design eventually reaching Kurchatov: 1) the centrally positioned walnut-sized bomb initiator-- consisting of the alpha-emitter polonium-210 (half-life 138.3 days) and beryllium which becomes a neutron emitter when compressed [FAQ: Uses Be-9 + He-4 -> Be-8 + n 
reaction. Modern weapons use an electronically controlled miniature linear particle accelerator called a pulse neutron tube (e.g., a scandium tritide target containing 7 curies of tritium impacted by a 0.19-0.25 amp deuteron beam). The Urchin initiator was a sphere consisting of a hollow beryllium shell, with a solid spherical beryllium pellet nested inside. The polonium was deposited in layer between the shell and the pellet. Both the shell and the pellet were coated with a thin metal film to prevent the c. 50 mCi polonium (or its alpha particles) from reaching the beryllium. The mixing was brought about by using the Munroe Effect (also called the shaped charge, or hollow charge, effect: shock waves collide, powerful high velocity jets are formed. This effect was created by cutting parallel wedge-shaped groves in the inner surface of the shell. When the implosion shock collapsed these grooves, sheet-like beryllium jets would erupt through the polonium layer, and cause violent turbulence that would quickly mix the polonium and beryllium together ]; (2) concern over premature detonation (predetonation) with Pu239 as a "gun", especially with Pu240 contaminant [FAQ: because it has higher spontaneous fission rate], leads to choice at Los Alamos of implosion design by 1944 for Pu bombs. Will use 6 Kg (5 -15 Kg) Pu239 cast in hollow hemispheres [however, the "Christy" core designed by Robert Christy uses nearly solid and barely subcritical Pl-239 hemispheres with central initiator, compressed by implosion into criticality]; (3) Implosion requires 3-dimensional high-explosive lenses made of fast [FAQ: Composition B (RDX+TNT), later octogen or HMX] and slow burning [FAQ: baratol or later boracitol] HE used to shape the detonation wave [FAQ: pressures of up to several megabars are achieved] converging inward on a central point-- this increases density of the Pu by 8x [FAQ 2-3x in the "insertion time" of 1-4 microseconds, versus 1 millisecond insertion time and no compression for a gun].

Chapter 7

 Additional spy activity in US and England: Steve Nelson, Haakon Chevalier, Israel Halperin, Alan Nunn May, Elizabeth Bentley, Julius and Ethel Rosenberg, her brother David Greenglass.

Chapter 8

Efforts to locate and corner supplies of U ore. After Berlin falls, allies capture stored Belgian Congo ore in Germany. European war ends May 7, 1945. 

Chapter 9

Fuchs passes more important information on the implosion design: chemical composition of the HE, a bomb sketch, the initiator has 50 Ci of polonium, the crucial aluminum shell (to dampen hydrodynamic Taylor instability) interposed between the HE layer and the uranium tamper (500 pounds of natural U "tubealloy" which surrounds the Pu core), final weight c. 3 tons. 

First US test: a Pu implosion bomb ["Gadget"] at Trinity test site N of Alamogordo 7/16/45 c. 10 KT, witnessed by Fuchs.

First Atomic bombs dropped: Luis Alvarez invents exploding electric wire [FAQ: later, foil; electrical energy stored in high-capacitance capacitor and switched via triggered spark gaps, krytrons or thyratrons etc.] detonation system for "Fat Man" high-explosive (HE) imploded plutonium bomb used 8/9/45 at Nagasaki [FAQ: efficiency 16%] and the Trinity test explosion. The Hiroshima bomb "Little Boy" 8/6/45 was a 15 KT uranium gun bomb (a less efficient design, [FAQ: 1.4% efficiency]) using 64 Kg of U-235, design directed by Robert Serber. [FAQ: highly enriched weapons-grade uranium c. 93.5% was code-named "Oralloy = Oy" for Oak Ridge alloy.] Stalin now decides to move bomb production to a high priority. 

Chapter 10

The Smyth Report on Atomic Energy for Military Purposes declassifies certain design aspects of reactors and the bomb (does not mention implosion). Gouzenko defects to the West and describes Soviet spying. Rapid US demobilization after the war. 

David Greenglass passes info to Julius Rosenberg on improvements in or specifics of the implosion bomb design, including (1) the shape [FAQ: hexagonal and pentagonal in familiar soccer ball configuration]) of the 32 HE lens molds (he reports 36), (2) the use of capacitors to fire the detonators, (3) the use of the Munroe effect (shaped charges) with cone-shaped holes in the initiator to improve mixing, and (4) the composite core consisting of an outer sphere (the tamper) of U separated ("levitated") from the Pu core by an air gap to increase yield by increasing the outer shell's momentum before impact with the Pu core. Fuchs passes info to Gold after Trinity providing a full description, incl. Pu chemistry and physical properties [FAQ: primarily an alpha emitter, half-life is 24,360 years], size & weight of the Fat Man Pu core (90 mm, 7.3-10 Kg [actually 6.2 Kg]), method of assembly of the bomb, composition of U gaseous separation filters (sintered nickel), levitation concept of Pu core wrt tamper, the Urchin initiator design (with grooves on the inner surface of a Be ball, used on all implosion bombs for next 5 years), the U tamper (which served both as a neutron reflector and inertial restraint to premature explosive disassembly), the boron layer around the tamper (absorbs thermal neutrons to reduce predetonation), the weight of HE (2 tons), the duralumin shell, the heat generated by the Pu and Polonium (raising temp by 90 degrees C [FAQ: weapon-grade Pu-239 generates 2.4 W/kg, 14.5 W/kg in reactor grade plutonium with higher Pu-240]). Beria receives this report Oct 18, 1945. Kapitza complains of Beria's leadership on atomic bomb project and placed under house arrest August 1946.

Chapter 11

After war's end, American weapons program halts and atomic scientists are plagued by self-doubt & guilt, esp. Oppenheimer. He, Fermi, Compton, & Lawrence warn of likelihood of greater-powered weapons being developed & urge a political solution, opposing working further on nuclear weapons. Teller, an anticommunist Hungarian hawk, favors developing thermonuclear (TN) bomb (the "Super"), first suggested to him by Fermi in Dec 1941. He believes it is inevitable and needed to counter the Russian threat. Groves thinks the Soviets will be 20 years developing it. Various estimates made of time until Russian parity. Oppie leaves Los Alamos. Norris Bradbury's vigorous advocacy saves Los Alamos, urging development of more efficient and reliable weapons. 

By 1946, Soviet physicists receive high priority and privilege. Reactor F-1 in Moscow is still being planned and a major production site on the Techa river, Chelyabinsk-40, is also planned. The Russians translate and publish the Smyth report Jan 1946. They learn of Xenon-135 buildup in high-flux reactors poisoning the reaction. Bohr believes all countries should have the atomic bomb to prevent nuclear war.

Chapter 12

An implicit policy of first-strike nuclear strike capability against the USSR prevails in the USAAF-- offense would be the best means of defense. Truman opposes "preventative" war, finds it repugnant. Missiles will be needed. Missile attacks cannot be deterred, only retaliated against, thus providing deterrence. Rand Corp proposes satellites 1946. Nuclear weapon assemblies (with Fat Man=Mark III cores) are being stockpiled. LeMay recruits former Third Reich's Werner von Braun and Walter Dornberger. Nuclear effects of atomic attack on ships to be tested at Bikini atoll. The Acheson-Lilienthal report (March 1946) advocates nuclear proliferation with tight controls by an international body (it fails to garner support). George Keenan's highly influential telegram 2/22/46 describes need to contain USSR, its paranoia, no possibility of peaceful coexistence. Churchill gives Iron Curtain speech in Fulton, MO 3/15/46 stating need to oppose Soviet expansionism and for nuclear superiority (a call for an all-out arms race). Bernard Baruch presents US views on enforcement and punishment for nuclear violations to UN, offending Soviets and fails. Soviets begin Sarov test facility (like Los Alamos), 400 miles east of Moscow, eventually headed by Pavel Zernov.

Chapter 13

Further espionage by Fuchs at Los Alamos, possibly aided by courier Lona Cohen. Canadian arrests of 22 spies incl Israel Halperin and in England of Alan May. Fuchs passes more info on Pu, cores, breeder reactor, and thermonuclear reactions and possibility of a TN bomb. 

The Mark IV bomb design incorporated levitated composite core.

History of fusion: Rutherford (with Marcus Oliphant and Paul Harteck) discover (1934) fusion reaction when bombarding D + D -> Helium-3 plus n + gamma rad + 3.27 MeV overall energy released. [FAQ: The neutron receives 2.45 MeV. Can also have D+D-> T + p + 4.03 MeV, occurs with equal probability]. The high bombardment energy (or temperature of 400 million degrees) of reactants required to overcome electrical repulsion leads to term "thermonuclear". Bethe proposes H -> C sequence as mechanism of stars 1938. Proposals for TN weapons by Japanese Hagiwara May 1941 (no followup made) and Fermi -> Teller September 1941. Energy/weight for D is 8x that of U235 [FAQ: 82.2 Kt/kg versus 17.6 Kt/kg]. 1 gram D undergoing fusion = 150 tons of TNT; 12 Kg of D = 10 MT TNT [sic, inconsistent]. Possibility of a TN weapon discussed at length at Los Alamos summer 1942. Teller devotes full-time to it as of autumn 1943. Need for massively complex calculations (to elucidate the behavior of massive neutron flux "neutronics", heat released "thermodynamics", and fluid flow of the particles and radiation "hydrodynamics") employs Stanislaw Ulam and John Von Neumann and eventually the ENIAC and MANIAC computers. Desirability of tritium ("T", half-life 12.5 years): the D+T fusion cross-section is 100x that of the two D+D reactions combined and ignition temp is lower at 40 million degrees [FAQ: Total energy is 17.588 MeV and the n is 14.06 MeV]. Klaus Fuchs attends the April 1946 Super conference. Teller asserts the present knowledge indicates reasonable certainty a weapon can be made. He proposes at various times two alternative designs: (1) His "classical Super" design consisted of a fission bomb at one end of a cylinder of D; (2) another design with massive imploded enveloping spherical layered shells-- the "Alarm Clock" (so named because it will awaken the world). A pure fission weapon has an upper limit of about 1 MT due to size and weight limitations whereas there is no theoretical upper physical limit to the size of a TN weapon. Need for a beryllium tamper to release neutrons. Possibility of compressing D with radiation mentioned. Teller seems overly optimistic to Serber etc. 

Soviets begin TN quest 1946 after report of Gurevich, Zeldovich, Pomeranchuk, and Khariton. 

Two US fission bomb tests (with Christy cores) at Bikini 1946 present confusing message of US intentions and undermine talk of disarmament. British begin their own atomic program.

Chapter 14

Kurchatov works to develop the 10 watt F-1 Uranium-graphite test reactor in Laboratory No. 2 in Moscow, first proposed 1943-- it is a copy of Hanford 305 test reactor (design possibly passed by Alan May) and will be used to test U235 and graphite purity for the Chelyabinsk-40 production reactor. Primitive state of Russian technology: e.g. purification of calcium and graphite is a barrier. Criticality of F-1 achieved 12/25/46. It contains 27 tons of U and is air-cooled. Beria is suspicious. 

In the US, "Wigner's disease", an effect of radiation on graphite producing swelling and occlusion of U rod channels, causes reactors to be shut down. The AEC is formed by Atomic Energy act of McMahon August 1946, headed by David Lilienthal (former TVA chairman). The unpublished and inflammatory Clifford-Elsey report documents the aggressive actions of the USSR in Eastern Europe and that they represent a direct threat to the security of the US. The AEC inspectors (commissioners) determine that we have no ready-to-go bombs, though cores and parts are available for assembly, & US military preparedness is very low after extensive demobilization. Security is lax. 

Chapter 15

The prison-like setting of Sarov for Lev Altshuler, Zukerman, Pavel Zernov (chief), Yuli Khariton (scientific director). Laborers provided by zeks (prison zones). 

In US, spies Bentley, Gold, and Brothman are interrogated but not tried. Donald Maclean in high position as co-secretary of Combined Policy Committee in Britain. Truman Doctrine (3/12/47) proposes what amounts to a Cold War, supporting free peoples resisting subjugation. Secy of State George Marshall proposes Marshall Plan for Europe. US negotiates a secret modus vivendi (signed Jan 1948) with England conditioning aid to them on receiving Belgian U ore as well as nullification of British veto on US atomic bomb use. National Security Act July 1946 forms Dept of Defense, separate Air Force, CIA, and National Security Council.

Chapter 16

Ulam and Von Neumann invent Monte Carlo statistical technique for calculating TN behavior. Teller favors a U gun for the Super, not implosion for the fission component (because of interference from the HE component). Teller also proposes lithium deuteride [Li-6 + n -> He-4 + tritium + 4.78 MeV; FAQ: requires low MeV neutrons whereas Li7 requires 4 MeV neutrons], but wants to delay pending more calculations. Oppie becomes chairman of the AEC's General Advisory Council. Concerns about his security record and the past contact with Chevalier resurface-- AEC commissioner Lewis Strauss begins to despise him. Stockpiling of atomic weapons increases in 1947: 13 Pu Mark series Pu bombs plus 50 Mark series cores (9 all-Pu solid Christy cores, 36 composite Christy cores, and 5 as yet untested levitated composite cores). 35 nuclear-capable B-29 bombers also deployed. Need for capability to detect foreign tests. LeMay is commander of USAF in Europe. Soviets occupy Prague 2/25/48. Sense of war rises, and any remaining US-USSR collaboration dissolves. Three Sandstone series nuclear tests at Eniwetok 1948 (49 KT max, consisting of composite levitated cores, much more efficient than solid Christy Pu cores or U gun) mark the beginning of nuclear weapons as other than complicated laboratory apparatus. US-USSR negotiations over nuclear disarmament break down 1948. Negotiations to form NATO begin June 1948 (NATO created April 1949). Berlin blockade begins 6/24/48 when Soviets close rail traffic to West Berlin-- response is airlift June 1948 - May 1949 (the first Cold War confrontation).

Chapter 17

Buildup of cargo capacity in Europe for airlift: C54s, B-29s, etc. Formation of SAC under Curtis LeMay. Truman reluctant to use atomic weapons. Who is in charge of the weapons? Lack of readiness of US bombing forces shown at Dayton drill. LeMay drills bombing crews in bombing by radar. The FBI works to breaking Russian encrypted code, revealing the name Ethel as a spy. More spies. Truman and Stalin avert overt war and Stalin lifts rail blockade May 1949.

Kurchatov brings Chelyabinsk-40 A production reactor online June 1948 operating at 100,000 KW. Discovers U rod swelling in high flux (due to argon accumulation etc., not same as Wigner's disease). Andrei Sakharov joins Tamm at FIAN for TN research (they developed the first USSR TN device). In his "First Idea", he reinvents Teller's layer-cake (Alarm Clock) design of alternating concentric fission and light fusion elements. The Pu239 core would have an expanded U tamper with light elements that would undergo fusion, releasing high energy neutrons that would fission the U238 tamper-- a fission-fusion-fission system. In his Second Idea, he suggested LiD, lithium deuteride, as a TN fuel.

Chapter 18

LeMay of SAC wants a war plan and more bombers to allow a long-range first-strike bombing capability, capable of dropping 80% of atomic stockpile in one attack. Deployment of B36s, B50s, midair refueling, high-altitude radar-directed bombing. US nuclear stockpile consists of 56 Mark III bombs (i.e., Fat Man designs that could accommodate solid Christy or composite cores). NATO created April 1949. Cold War momentum gains. Teller rejoins Los Alamos-- in part because Hungary has fallen to Soviets. William Borden predicts inevitable war and urges, along with others, confrontation with Stalin. Frank Oppenheimer, brother of Robert, exposed as a former communist. Truman favors more bombs. Military justifies need for more and more bombs against more and more targets.

Pu-239 extraction begins December 1948 in Chelyabinsk-40 with considerable personnel exposure and first Soviet cases of radiation sickness, aided by gulag labor and discharging waste into Techa River. A Soviet Pu core is made by spring 1949.

Chapter 19

The Soviet bomb components are transported form Sarov to Semipalatinsk-21 in NE Kazakhstan and exploded 8/29/49. This is a 20 KT device dubbed "Joe-1" in US and "First Lightning" or RDS-1 in USSR, a copy of the Trinity bomb. The characteristic radioactivity is detected in US and England and analyzed precisely by Tracerlab as coming from a bomb with Pu core and natural U tamper. Truman announces it publicly 9/23/49. Fuchs is discovered to be a spy Sept 1949. FBI also notes presence of a high-level mole in US-Great Britain communications (later found to be Donald Maclean). David Lilienthal has reservations about development of H-bomb but AEC commissioner Lewis Strauss urges development of H-bomb and Truman orders all-out effort to build it. Will need more tritium production (which will reduce Pu production).

Chapter 20

Ernest Lawrence and Luis Alvarez call Teller-- the three favor and promote the TN bomb project. They propose Canada convert its heavy-water reactor at Chalk River to tritium production. Teller is optimistic about the Super (cylindrical) design but more calculations are needed. The possibility of radiological warfare (using radioactive products) is raised. China's People's Republic declared October 1, 1949. In US, more D and Tritium are needed. Harvard's Conant and Lilienthal oppose development. Bethe and Fermi refuse to return to Los Alamos to work on it. The GAC led by Oppie recommends against it and for a variety of other projects October 1949. It would be a weapon of unlimited power [practically speaking limited to about 100 MT] and a weapon of genocide for exterminating civilian populations. Teller, Strauss, Sen. McMahon, and William Borden promote it. Joint Chiefs favor it. The AEC commissioners are split on the project. Truman says to proceed Jan 1950, even if it will just be a bargaining chip, starting the ultimate arms race.

Chapter 21

Fuchs confesses to espionage 1/24/50. Joseph McCarthy begins search for commies in State Dept. Teller, Ulam, & Gamow promote the Super, with development assisted by John Wheeler, Carson Mark, Marshall Holloway, Emil Knonpinski, Charles Critchfield, Marshall Rosenbluth. Teller's paper Feb 1950 outlines the classical Super and the alternate and more clearly feasible layered design, the Alarm Clock. But the Alarm Clock was limited to about 1 MT, and Teller was fixated on higher megatonnage. Bradbury objects to the costs of TN development vs improvements in other weapons. Ulam and Everett make initial preliminary Super calculations which are discouraging-- Teller blames his opponents for discouraging recruiting and accuses Ulam of bias. General Loper estimates Soviet progress may be greater than believed. Fuchs convicted March 1950, sentenced to 14 yrs in England. Gold confesses to being Fuch's contact, implicates David Greenglass, who is arrested June. The Rosenbergs are arrested July and August 1950. USSR signs alliance treaty with China Feb 1950. Kim Il Sung directs invasion of S Korea 6/25/50, with the blessing and support of Stalin and Mao. US forces enter Korea June 30. Secy of State Acheson favors this action as a means of confronting and containing Communism.

Chapter 22

SAC has 868 planes. Question arises, Who can order an atomic strike? Bombs are stored at Sandia base near Albuquerque. LeMay wants option to order atomic strike himself in extreme circumstances. Heavy bombing of N Korea includes SAC bombers and includes first use extensive use of napalm. US and Truman come close to using atomic bombs in Korea, having moved 9 Mark IV nuclear cores to USAF custody probably in Guam. One bomber crashes and explodes the HE component of a core-less atomic bomb, killing General Travis-- base is renamed Travis AFB. 5 new heavy-water reactors authorized. MacArthur lands at Inchon 9/15/50 and pushes into N Korea to border with China at Yalu R. China sends troops across Yalu R October 1950 and Soviets provide air support and tanks. Truman declares a US national emergency 12/16/50. Soviet bombers in Manchuria threaten Japan and S Korea. MacArthur fired for insubordination 4/11/51, after he called for "no substitute for victory". Truman was uncomfortable using nuclear weapons-- they appear of little use in this kind of war.

Chapter 23

New Ulam/Everett and Ulam/Fermi/Garwin calculations show Teller's classical Super design cannot work-- George Gamow also opposes the design. William Libby joins AEC, favors H-bomb, suspects Oppie. Teller is insulting, wants his own lab, has a messianic complex. Bethe concludes, after Von Neumann's additional calculations plus Ulam's, that the classical Super is dead-- the main problem is that radiation carries off the needed heat too fast and Teller had dismissed the value of compression. Ulam conceives a breakthrough design concept Dec 1950: compression implosion via a shock wave in a neutron fluid (thus "hydrodynamic") from fission primary can trigger a staged secondary explosion of nearby TN material. He shares this with Teller-- they write a paper March 9, 1951, in which Teller has added the critical concept of using photons as the source of radiation compression of the TN component rather than neutron fluid (the former type of compression make high megatonnage with reasonable size possible). Teller pushes Ulam aside afterwards and refuses to deal with him. In late March he adds a second fission component at the core of the cylinder of the TN material (the "sparkplug") consisting of subcritical U235 compressed to criticality. [FAQ: Teller-Ulam weapons can have a third separate fusion stage, such as the USSR's 50 MT 3-stage weapon Tsar Bomba exploded on 30 October 1961 over Novaya Zemlya].

5 test explosions at Eniwetok (Greenhouse series) include "Cylinder=George" 225 KT 5/9/51 and 45.5 KT "Item" tests. These confirm yield boosting via D+T reaction [FAQ: neutrons generated by D+T fusion boosting improve efficiency of the fission reaction but fusion energy released contributes negligibly to overall energy production except through its enhancement of fission; most fission bombs are boosted today, esp. small weapons]. GAC convenes 6/51, decides to promote TN bombs and no longer vocally concerned about morality (e.g., Bethe in light of Korea). Borden suspicious that Oppie is a spy. Teller resigns Sept 1951 in pique because of Bradbury's decision to put Marshall Holloway in charge of H-bomb development and presses for his own lab, which he eventually gets. 

The Rosenbergs sentenced to death April 1951. David Greenglass, Morton Sobell, and Harry Gold convicted.

Chapter 24

Soviets have tested Joe 2 Sept 24, 1951, prob. a levitated U-235 core with yield c. 40 KT. Joe 3 with composite core air-dropped October 18, 1951.

British test their first device Oct 3, 1952 Monte Bello Islands off NW coast of Australia, 25 KT detonated 90' beneath a ship.

First multistage megaton TN device assembled and exploded on Elugelab island of Eniwetok Atoll 11/1/52, 10.4 MT (Ivy Mike or "Sausage"). It is contained in a 1" thick [FAQ: 12" thick] steel cylinder 6'x20' and weighs 82 tons overall. At top is TX-5 (or TX-V) fission primary. X-radiation photons from it heat a polyethylene inner lining of the lower cylinder to plasma, causing re-emission of X-Rays of similar energy [FAQ: due to quickly achieved thermal equilibrium] (the TN component is protected by a blast shield from direct radiation from the TX-5 above). These X-Rays heat and compress the natural U pusher surrounding the D, causing it to ablate-- this produces ablation pressure directed inward [FAQ: like an inverted rocket; plasma pressure and radiation pressure do not play a significant role]. Cryogenic liquid D within is compressed [FAQ: to up to 30x], compressing the inner tritium-boosted Pu fission sparkplug [FAQ: up to 4x], triggering its fission, further compressing the D from within. The D undergoes fusion [FAQ: temp up to 300 million K vs. 50-100 million for fission reaction. Pressures achieved to initiate fusion in TN weapons are 10 to 100 gigabars]. Tritium is generated and this immediately undergoes T+D reaction releasing 14.1 MeV neutrons. These cause fission of the vaporized U-238 pusher, which contributes >80% or 8 MT of the overall yield. [FAQ: fusion reaction completed in 20-40 nanoseconds]. Another device, Ivy King tested 11/15/52 with 500 KT yield at Eniwetok [the largest pure fission bomb tested].

Chapter 25

Russian nuclear development thrives, incl. a gaseous diffusion plant and heavy-water reactor. Li-6 deuteride made for Sakharov's layer cake [sloika] (like Teller's Alarm Clock). Stalin dies 2/28/53. Malenkov and Beria fail in power grab, foiled by Kruschev after Beria's attempt to liberalize East Germany. Rosenbergs executed 6/19/53 despite appeals for clemency-- much evidence against them. Beria killed. 

Joe-4 explosion in USSR [RDS-6s], a layer cake HE-implosion TN-boosted (c. 20%) single stage fission device with alternating layers of U and LiD 400 KT 8/12/53. Efforts to compare US and USSR capability. Teller and Borden fear that treasonable deception may engender complacency and allow the Soviets to pull ahead.

Chapter 26

New AEC chairman Lewis Strauss and William Borden push to oust Oppie. Borden sends accusatory letter to FBI Dir Hoover. Eisenhower presses to raise a wall between Oppie and govt. Strauss submits formal charges to AEC and Oppie 12/15/53. Testimony April 1954 pro Oppie (Bethe, Lilienthal, Kennan, Rabi, Bradbury, Bush) and against (Latimer, Wilson, Pitzer, and especially Teller, Pash, Borden, Alvarez). Security clearance revoked 6/29/54.

Castle series of US TN tests included Castle Bravo ("Shrimp") 15 MT on 3/1/54 at Bikini, fueled by solid LiD (lithium enriched to 40% Li-6), 23,500 pounds overall weight. This was the largest yield ever tested by the US. Series also included a 6.9 MT radiation imploded Alarm Clock ("Union"), Yankee 13.5 MT, and Nectar 1.69 MT weighing only 6250 pounds.

Chapter 27

Evaluation of relative strengths of US and USSR have evolved from overwhelming superiority to mutual destructive capability. Concepts of preventive and preemptive war considered. Proliferation of targets and nuclear stockpile. Threats of nuclear confrontation. Curtis LeMay as CINCSAC contemplates provoking war while US is stronger, and pushes provocative reconnaissance actions to the brink (e.g., US Navy PB4Y-2 shot down 4/8/90; US-sponsored British night-flying B-45s). Bombs are not fitted out with PAL Permissive Action Links until the 1960s. LeMay seems to have plans for independent action contrary to US policy. 

Soviet test of air-dropped 2-stage LiD device 11/22/55 1.6 MT with Sakharov-Zeldovich designed radiation-implosion configuration (like Teller-Ulam); also a layer-cake TN device 11/6/55. Korean armistice July 1953. Confrontations over Quemoy and Matsu (1958), in which Dulles acknowledged the US was ready to use atomic weapons-- Kruschev states an attack on China is an attack on Soviet Union. Cuban Revolution 1959. Cuban Missile Crisis October 1962 brings US closest to nuclear war ever (unknown to the CIA, the Soviets had 20 nuclear warheads at the time in Cuba for medium-range missiles that could be targeted as far north as Wash DC). Thomas Power as head of SAC and LeMay (chief of USAF) feel we lost by not using our nuclear weapons! Numerous examples of snafus in command and control which might have led to war, and the zeal of the SAC commanders hoping to provoke war. LeMay's belligerent attitude toward Kennedy, whom he believed to be as coward.


Followup on Oppie (who died 1967 a broken man), Strauss (rejected by Senate from serving as Secy of Commerce), Teller (extensive rejection and repudiation, still alive in 1998), Bethe (helped negotiation of Nuclear Test Ban Treaty forcing testing underground), Fermi (d. 1954), Von Neumann (d. 1957) Fuchs (d. 1988), other spies, LeMay (d. 1990), Kurchatov (d. 1960), Sakharov (courageous protest work helping to bring an end to nuclear arms race, d. 1988). The arms race cost the US $4 trillion and subjected the world to excess danger of omnicidal war. It was unnecessary and was promoted by political and economic factors and nuclear hawks such as Teller. Even one hydrogen bomb would have provided sufficient deterrence. Oppie concluded in 1952: "The problem which is posed by the release of atomic energy is a problem of the ability of the human race to govern itself without war. There is no permanent method of excising atomic energy from our affairs... It is hard to see how there could be any major war in which one side or another would not eventually make and use atomic bombs."