The sum of all fears - Tom Clancy [365]
"Okay, Lieutenant." Yankevich walked inside to get another cup of coffee to keep warm, then returned to the out-of-doors he loved so much. The sun was setting behind the Rockies, and even in zero weather with a bitter wind, it was always something beautiful to watch. The police sergeant walked past the network up-link vans to watch the glowing orange ball dip through one of the blowing snow clouds. Some things were better than football. When the last edge of the sun dipped below the ridge line, he turned back, deciding to take another look at the box inside the truck. He would not make it.
CHAPTER 35
Three Shakes
The timer just outside the bomb case reached 5:00:00, and things began to happen.
First, high-voltage capacitors began to charge and small pyrotechnics adjacent to the tritium reservoirs at both ends of the bomb fired. These drove pistons, forcing the tritium down narrow metal tubes. One tube led into the Primary, the other into the Secondary. There was no hurry here, and the objective was to mix the various collections of lithium-deuteride with the fusion-friendly tritium atoms. Elapsed time was ten seconds.
At 5:00:10, the timer sent out a second signal.
Time Zero.
The capacitors discharged, sending an impulse down a wire into a divider network. The length of the first wire was 50 centimeters. This took one and two-thirds nanoseconds. The impulse entered a dividing network using kryton switches - each of them a small and exceedingly fast device using self-ionized and radioactive krypton gas to time its discharges with remarkable precision. Using pulse-compression to build their amperage, the dividing network split the impulse into seventy different wires, each of which was exactly one meter in length. The relayed impulses required three-tenths of a shake (three nanoseconds) to transit this distance. The wires all had to be of the same length, of course, because all of the seventy explosive blocks were supposed to detonate at the same instant. With the krytons and the simple expedient of cutting each wire to the same length, this was easy to achieve.
The impulses reached the detonators simultaneously.
Each explosive block had three separate detonators, and none of them failed to function. The detonators were small wire filaments, sufficiently thin that the arriving current exploded each. The impulse was transferred into the explosive blocks, and the physical detonation process began 4.4 nanoseconds after the signal was transmitted by the timer. The result was not an explosion, but an implosion, since the explosive force was mainly focused inward.
The high-explosives blocks were actually very sophisticated laminates of two materials, each laced with dust from light and heavy metals. The outer layer in each case was a relatively slow explosive with a detonation speed of just over seven thousand meters per second. The explosive wave in each expanded radially from the detonator, quickly reaching the edge of the block. Since the blocks were detonated from the outside-in, the blast front traveled inward through the blocks. The border between the slow and fast explosives contained bubbles - called voids - which began to change the shock-wave from spherical-shaped to a planar, or flat wave, which was refocused again to match exactly its metallic target, called 'drivers.'
The 'driver' in each case was a piece of carefully-shaped tungsten-rhenium. These were hit by a force wave traveling at more than nine thousand eight hundred meters (six miles) per second. Inside the tungsten-rhenium was a one-centimeter layer of beryllium. Beyond that was a one-millimeter thickness of uranium 235, which though thin weighed almost as much as the far thicker beryllium. The entire metallic mass was driving across a vacuum, and since the implosion was focused on a central point, the actual closing speed of opposite segments of the bomb was 18,600 meters (or 11.5 miles) per second.
The central aiming point