Dark Sun: The Making Of The Hydrogen Bomb

then, Wechsler's group had to dump the excess liquid hydrogen in the transport dewars:

How do you get rid of liquid hydrogen? You burn it. How do you burn it? You've got to flare it off into vapor first. You open a nozzle and you flare it off at a given pressure and you light it. We used a broom, a regular straw broom. Light the broom, reach up and light the gas stream, flaring and burning thousands of liters of liquid hydrogen. That's a tremendous amount of energy. Once it starts burning you don't see any vapor trails of water vapor condensing out of the air. There's nothing. There's a roaring noise that sounds like a huge blow torch and it's invisible. If there's any dust in the air you can see a little waviness, but the flame is invisible. When we flared off the extra, the day we were going to leave to get on a ship out there on the Mike site, it was funny. We had two of these dewars sitting there flaring off, couldn't see a thing, just this roaring noise and all these terns flying around. They'd fly along about a hundred feet in the air above you and they'd hit that spot where this invisible hot air was going and whoa, talk about getting your tail feathers singed. That was a real hotfoot.

After the Mike secondary had been filled with liquid deuterium, Wechsler recalls, “we waited a few days to see that everything was stable.” The last step in the assembly process was inserting the new primary core. Schreiber was in charge of the pit crew. “They knew what they were doing,” he says lightly; “I provided moral support.” The Mike casing had a manhole near the top end. “You could use the manhole for loading.” The primary pit and core went in on the afternoon of October 31. “Then they buttoned the Mike gadget up.” A final dewar of liquid hydrogen to top off the reflux cooler came over at nine-thirty that night. The arming team completed its checklist shortly after midnight on the morning of November 1, 1952, and boarded the Estes, which sailed from Eniwetok lagoon at 3:15 a.m. to a point about ten miles beyond the southern rim of the atoll, thirty miles from ground zero. The wind, which had been only marginally favorable on October 31, shifted to southerly at midnight, a direction that would blow the fallout away from the atoll into the unpopulated Pacific north of ground zero, ideal for the shot.

Two primitive but state-of-the-art television cameras broadcast images of the gauges monitoring Mike's systems — monitor dials and timing-signal and go-no-go indicators — to the firing room aboard the Estes. “I sat there all that night watching those damned things,” Wechsler recalls, “taking notes. We made tables ahead of time of what the pressure balances would be and what this meant in terms of temperature and how full things were. So we knew what we wanted it to be and we knew when a deviation might be excessive. Nothing was moving. Your eyes play tricks on you after a while. We'd had lots of discussion about whether we might get a little bubble. If we did, we needed to know how big it might be, because it might affect the yield. But as near as we could tell that night, [the secondary] was full and it stayed full. Everything worked just the way it was supposed to.”

H-hour for the Mike shot was 7:15 a.m., November 1, local time (October 31 in the United States). Before then, B-29 canister-drop, C-54 photo and B-47 and B-36 effects aircraft began orbiting at altitudes from ten to forty thousand feet at prescribed distances and compass headings from ground zero. Three 250-watt Motorola independent radio links communicated manual timing signals, automatic-sequence-timer start and emergency stop signals between the Estes and Elugelab. Automatic countdown sequencing began at H — 15 minutes. Two sniffer F-84 jets flew into position at forty thousand feet two minutes prior to H-hour, ready to flank the Mike cloud and take samples. At H — 1 minutes, loudspeakers aboard the ships of the task force instructed the thousands of military and civilian personnel to put on high-density goggles or turn away and cover their eyes. A momentary power failure aboard the Estes threw off the timing sequence by half a second, an unnerving stutter; Mike fired at 0714:59.4 ± 0.2, November 1, 1952.

When the radio signal from the Estes control room reached Mike, the capacitors in the Mike primary, already charged by the primary battery, discharged into a harness of electrical cables around the primary that carried the high-voltage current simultaneously to the ninety-two electric detonators inserted into the primary's high-explosive shell. (The increased number of detonators in the Mike primary made it possible to shape an implosion without using bulky high-explosive lenses, one way the TX–V device was made smaller and more transparent to radiation.) All ninety-two detonators fired with microsecond simultaneity; a detonation wave spread from each detonator, met other spreading donation waves moving inward and concentrating, emerged from the explosives as a shock wave, crossed to the aluminum pusher shell vaporizing as it passed, rocketed the pusher inward, crossed next to the primary's heavy uranium tamper, liquefied and vaporized the tamper, moved the material to the uranium shell of the core, hammered the uranium shell inward across an air gap to the plutonium ball levitated within, hammered the plutonium ball and crushed the Urchin initiator levitated at the center of the assembly. At that moment of maximum compression, with the vaporizing mass of uranium and plutonium supercritical, the shock wave shaped by the Munroe-effect grooves in the beryllium shell of the Urchin sliced through the shell and mixed beryllium with the polonium plated onto the ball of beryllium inside; alpha particles from the radioactive polonium knocked half a dozen neutrons from the beryllium; the neutrons ejected into the surrounding supercritical mass of uranium and plutonium and a chain reaction began.

Eighty generations later — a few millionths of a second — X-radiation from the furiously heating fission fireball hotter than the center of the sun escaped the primary mass entirely, began to ablate the blast shield over the Mike secondary and flooded down the cylindrical radiation channel inside the Mike casing. Instantly the radiation penetrated the thick polyethylene lining of the casing and heated it to a plasma. The plasma reradiated X rays that shone simultaneously from all sides inward onto the surface of the heavy uranium pusher, heating it instantly to ablation. The ablating surface of the pusher drove it explosively inward even as it liquefied and vaporized. The intense pulse of pressure concentrated as it moved inward, closed the first vacuum gap, compressed the floating thermal shield, closed the next vacuum gap, compressed the outer and inner dewars, encountered the deep, cold mass of liquid deuterium, compressed the deuterium inward and started to heat it. As the pressure pulse that was heating the deuterium to thermonuclear temperatures converged upon itself down the long axis of the secondary, it encountered the fission sparkplug, imploded that cylindrical system and activated a second fission explosion boosted with high-energy neutrons from fusion reactions in the tritium gas the sparkplug compressed.

Sequence of events in two-stage radiation implosion (Mike device).

^{1. Primary fissions. X rays from primary pass through primary fireball ahead of blast and flow down radiation channel.}

^{2. X rays from primary vaporize polyethylene lining of Mike casing and heat it to a plasma. Plasma reradiates longer-wavelength X rays that ablate surface of secondary pusher, causing rocket effect that implodes secondary, compressing and heating deuterium to fusion temperature and pressure and imploding fission sparkplug.}

^{3. Sparkplug fissions, further compressing and heating deuterium from within. Full-scale thermonuclear fusion follows. Neutrons from fusion start fission reactions in U238 pusher shell, generating most of Mike's yield.}

^{4. Fireball breaks through casing. In microseconds before entire casing vaporizes, light pipes (not shown) carry hotspot breakthrough light (Teller light”) to streak cameras to measure progress of explosions.}

^{5. Fireball completely vaporizes Mike and quickly expands to more than 3 miles in diameter. Yield: 10.4 megatons.}

All these processes, proceeding through microseconds, prepared Mike for thermonuclear burning. Now the escaping X-radiation of the fissioning sparkplug heated the compressed deuterium at its boundaries; the increasing thermal motion of the deuterium nuclei pushed them together until they passed the barrier of electrostatic repulsion between them and came within range of the nuclear strong force, at which point they began to fuse. Some fused to form a helium nucleus — an alpha particle — with the release of a neutron, the alpha and the neutron sharing an energy of 3.27 MeV. The neutron passed through the electrified mass of fusing deuterons and escaped, but the positively charged alpha dumped its energy into the heating deuterium mass and helped heat it further.

Other deuterium nuclei fused to form a tritium nucleus with the release of a proton, the triton and the proton