Terminal Run

“Captain, we have nothing to lose. Order it to search and if it fails, have it come back to an aim-point range and detonate.”

“Give me a range to aim-point.”

“Twenty miles, Captain.”

“No, closer.”

“Fifteen?”

“Ten,” Lien decided, and dialed in the aim-point.

“Sir, if the incoming torpedo misses, the Tsunami will take us out at ten.”

“Fine, twenty miles.” The Tsunami had a full line of green lights. “Tsunami auto-sequence in five seconds, Mr. First.”

Zhou waited, biting the inside of his lip, wondering what the incoming torpedo was doing. It should have arrived by now. The deck trembled as the torpedo tube’s gas generator detonated, ejecting the Tsunami.

“Tube six fired, Mr. First, and the Tsunami is on its way. A pity we don’t have more.”

“Perhaps we should put the Dong Feng units in tubes one through five down the bearing line, sir—”

Zhou never finished the sentence.

After a flight time of four minutes, the missile hit the southern boundary of the TPC, and the arming circuit in the plasma warhead energized. The warhead was a fusion weapon — a hydrogen bomb — encased in the materials that would interact in the hundred-million-degree temperatures of the detonation to act to contain the blast to a small volume plasma, a tiny spoonful of the center of the sun, and that plasma would vaporize a third of the target and blow the rest of it to shrapnel. The seeker searched in the wide and narrow search cones as the missile flew through the TPC, but there was no target. The missile continued on past the TPC by a diameter, then turned and came back. The north-south grid search continued through the TPC over the next four minutes, but came up empty.

There was no target.

The missile executed an east-west grid search of the TPC, this time above the layer depth of two hundred feet, on the off chance that the target had come above layer and that the thermal layer might be interfering with blue laser reception. The missile was careful to avoid coming within a hundred feet of the surface, since the suction from the interface between water and air could pull the missile into an unstable angle of attack, and the missile could tumble faster than the control system could correct it. Some of the test units had even rocketed out of the water and spun out of control and broken up on impact with water. Above the layer, there was still no target.

The missile realized it was about to run out of fuel, and it was time to execute the default detonation. Had the missile been programmed, it would have removed the plasma enhancements from the warhead casing, making the warhead a wider distribution fusion bomb, but this had been strictly prohibited by the Mod Echo designers. All it could do was detonate a plasma at a default point. The default detonation point had been selected as the centro id of the northern third of the TPC, under the assumption that the probability held that the target would have run away from the missile rather than toward it. The missile timed its arrival at the default point so that it would still have two minutes of fuel remaining, in case as it prepared to default detonate it found the target. But there was still nothing.

The missile dived back below the layer to a depth of five hundred feet, sailed toward the default detonation point, and seeing nothing, executed the default routine. The low-explosive initiator train ignited, setting off the medium explosives, which detonated the high-explosive shaped charges that caused separated pie-shaped elements of plutonium to collide and form a critical mass. The combined plutonium exploded in a nuclear blast that vaporized the tritium bottles, which then in the millions of degrees of the small high-energy blast reacted to fuse together into helium molecules. The resulting helium was slightly lighter than its reactants, because the mass loss was converted into pure energy, and the fission explosion became an even more powerful fusion explosion. Had the reaction continued from there, the sea would have erupted in a five-mile-wide mushroom cloud with radiation scattering over the seascape, but instead the plasma-containment chemicals fused and reacted and surrounded the blast in the most powerful magnetic field ever invented by human hands. The mag bottle contained the nuclear blast and focused its energy into a three-meter-diameter sphere of high-energy plasma. The mass inside the bottle rose to hundreds of millions of degrees while the exterior — for a few tens of microseconds — remained undisturbed.

But soon the plasma envelope collapsed, and the blast effect began. The explosion was still powerful when viewed from the surface, but nothing like the weapon’s nuclear ancestors. The pressure pulse, the shock wave, from the explosion traveled through the water and blew the surface into a rising cloud of spray, then traveled sideways in all directions, eventually reaching the hull of a surfaced shape of high-yield low-magnetic steel that had been given the name Nung Yahtsu.