Nuclear pulse propulsion-"Project Orion"-had been a product of the twentieth century, one of many notions for liberating the infant Space Age from the dismal mathematics of chemical rocketry. Conceptually, it set some kind of record for brute-force crudity: detonate a series of nuclear explosions behind you and let them kick you forward! Naturally, it required a massive shock-absorbing plate for your vehicle's rear end. Worse, however, it had faced insurmountable political obstacles in a world understandably jittery about allowing anyone to send up spaceships packed full of what were in effect hundreds of small nuclear weapons. But for a time it had seemed to offer the best hope for reaching the outer planets and-especially after the Bussard ramscoop had come to grief on the hard facts about the interstellar medium in Sol's vicinity-the stars.
Then had come the unanticipated breakthrough into reactionless drives, and the Orion concept had gone the way of Jules Verne's giant cannon. At the same time, the idea of "dinosaur killers"-asteroids used as kinetic-energy weapons against planets-had joined reaction drives in the dustbin. It just wasn't practical to enclose an entire asteroid in a drive field. And tractoring such an object would have no effect except to rip the tractor-beam projectors out of ships that instantaneously took on velocities measured in percentages of c.
No, it couldn't be done with reactionless drives . . . but Vanessa Murakuma had wanted it done anyway. When she'd put the problem to Taliaferro, he'd automatically snorted that it was preposterous. Then he'd gone off and thought about it, to the near-exclusion of eating and sleeping. And when he'd put his solution before her, she'd backed him to the hilt, selling the idea to a skeptical Joint Chiefs of Staff.
Taliaferro's moment of amusement passed.
"I tell you what, Commander," he said. "You've got precisely as long to decide whether there's a problem-and, if there is, to fix it-as there is between now and Sledgehammer Three's scheduled ignition."
"But . . but, Commodore-"
"But me no buts, Commander. I've just finished checking out all the other asteroids, and they all report that they're ready for ignition. The first of them, Hammer Four, is due to light off in-" Taliaferro glanced at his wrist chrono "-thirteen minutes and a little less than twenty seconds. After that, there's no turning back. I'm damned if I'll stop the clock now to wait for you to get your act together!"
"Commodore, I protest!"
"Protest all you want to, Yu-hsiang-later. But right now, if I were you I'd get busy on that pusher plate. Sledgehammer Three is going to get kicked out of its orbit on schedule, and if you're still there at the time . . . well, it ought to be an interesting trip to Planet III, especially with fusion bombs going off under your ass!"
Taliaferro cut the connection while Lin was in mid-splutter, and turned to the pilot.
"All right, get us back to Alfred. And raise Fleet flag."
While he waited, Taliaferro studied a two-dimensional schematic of the Home Hive Two A System out to and including the asteroid belt. Sheer habit, for he'd long since memorized it. Still, he gazed at the little lights of the nine asteroids which TF 64.1 had transformed into weapons. They were strung out over forty-odd degrees of the belt's circumference, a curving scimitar of death. That was where they'd been found, and it had been out of the question to move them together, for the same reason their drives couldn't be tested: an Orion drive in operation was something the Bugs could hardly fail to notice. So they would start moving in staggered order starting with Hammer Four, each asteroid lighting off its drive as the others came up level with it on the hyperbolic orbit that would send them careening across the inner system, terminating at one of the three scarlet planet-icons on the display. Sledgehammer Three, the tip of the scimitar, would be last, so Lin actually had a fair amount of time left. Just as well, Taliaferro thought. I wouldn't really leave him there. Probably.
He'd barely finished reporting to Murakuma across the light-minutes when a multi-megatonne fusion fireball awoke a few score meters behind Hammer Four, its brilliantly defined shock wave surging toward the asteroid but never quite touching it. Then another . . . and another . . . and slowly, ponderously, Hammer Four began to move out of its immemorial orbit, trailing what looked (or would have looked, to anyone who'd braved the sleet of gamma rays) like a trail of small suns connected by a stream of glowing gas.
Operation Cushion Shot had begun.
It had taken an appreciable amount of time for the realization of what was happening to sink home through layers of unexpectedness-not a fatal delay, perhaps, but certainly a disadvantageous one. But there was no longer any room for doubt. The orbits into which those asteroids had been moved could be projected without difficulty, and all of them intersected at the point that would then be occupied by the third planet. Calculating the kinetic energy such impacts would release was equally simple. And the Fleet knew only too well what would happen to the system's remaining defenders at the instant that planet's population died.
Abandoning the outer system to the Enemy had been an error. That it was an error grounded in flawless logic was no excuse. Neither was the totally unprecedented nature of what the Enemy was doing.
There was, however, a positive aspect to the situation. The asteroids could be deflected from their courses-or, in the case of the smaller ones, actually broken up. It would not be easy, but with antimatter weapons it could be done. And the Enemy must be as aware of that fact as the Fleet was, so his freedom of action was limited by the need to defend those incredible kinetic projectiles as they followed their immutable hyperbolic courses in free fall, at a velocity which, while high on the standards of normal interplanetary bodies, was practically stationary to vehicles using reactionless drives.
There could be no further thought of waiting in defensive posture on and around the planets. Those asteroids must be intercepted as far away as possible. All available gunboats and small craft must be fitted with antimatter loads and launched immediately. And the Deep Space Force must go with them.
"Well, we expected it, Sir."
"So we did," Vanessa Murakuma replied to Leroy McKenna's observation. The response was purely automatic. Her entire consciousness was focused on the approaching Bug formation-a classic "Bughouse swarm."
Yes, she had expected it. Not even an idiot or a politician could harbor any remaining doubts about the Bugs' capacity to reason from observed data-or, at least, to perform some process that filled the same function as reasoning. They understood what that formation of asteroids meant, and they were committing everything they had left to what they knew was their final stand against apocalypse.
She studied the readouts on the mobile force that trailed behind the tens of thousands of kamikazes: sixty-seven superdreadnoughts, fifty-two battlecruisers and a hundred and thirty-four light cruisers. At least there were no monitors; evidently intelligence was correct in supposing that the Bugs had had insufficient time to complete any new ones since she and Lord Khiniak had made their last, regrettably uncoordinated incursion into this system.
Her eyes went to the holo sphere on whose scale that formation shrank to a single scarlet icon, moving to intercept a cluster of tiny green lights representing the asteroids and the combined fleets' battle-line, together with the fighter screen spread before them by Small Fang Meearnow'raaalpha's eighty light carriers.
Finally, she let her gaze rest on another emerald icon, near the inner fringes of the asteroid belt-one which she hoped and believed appeared on no similar displays aboard the Bug ships whose course it was paralleling.