—Ekatrina deployed their spare gauges, the instrumentation on the fusion reactors having been fried in the final power surge, and determined why neither fusion reactor would restart. When, starved of fuel, the reactors had sputtered to a halt, the capacitor banks to fire the lasers had ended up discharged. Drawing spare power from their small fission reactor for two days, she recharged a capacitor bank. That restarted one fusion reactor; it restarted its mate.
—Her emergency repairs complete, Ekatrina had also gone outside to study what they assumed and hoped was the Titan control center, and its connections to the mass driver.
Then the mission’s luck returned to normal.
* * *
“Calling Rescue One.”
Marcus was power sanding the recent regrowth on yet another bulkhead when the radioed summons echoed through the ship. Generalist was not a skill much in demand for characterizing the alien installation, and someone had to keep Ekatrina’s suspected AI at bay. Left to itself, the alien nanotech flourished like a weed.
“Sanding,” of course, was a euphemism. He wore out abrasive disks by the handful, disks that on some days were the primary output of their main printer, coated, not with sand, but with coarse crystals of silicon carbide. Fortunately, silicon and carbon were common enough. He tried not to think about the silicon-carbide and carbon-nanotube dust circulating and recirculating through the ventilation ducts and, despite the face mask he wore, into his lungs.
“Calling Rescue One.”
Marcus had just reached the bridge when the call changed. “Rescue One! Do you copy?”
He pulled down his face mask, let it dangle by its elastic strap. “Copy. I was all the way aft. What’s up, Yevgeny?”
“Can you join us? It will be easier to explain here.”
“Is it good news or bad?”
“Just come, please.”
Bad news, then. “Roger that. Ten minutes. Rescue One, out.”
“Copy that.”
In the end, it took Marcus closer to twenty minutes to suit up unaided and exit the ship. En route to the crater, for the hell of it, he pegged a couple fist-sized metal chunks. Even suited up, his fastball was pretty good. Reaching the crater floor and the access shaft, he awkwardly backed down the ladder and its too widely separated rungs into the large, square chamber the Titans had carved out forty meters deep within the Hammer. His team had arranged themselves into a shallow arc facing the ladder. Facing him.
Like an intervention, Marcus thought. Or a wake.
Under the radiance of portable work lamps, equipment cabinets glittered. In the corner they had left unilluminated, stacked metal boxes, welded shut with oxyacetylene torches, entombed all (they hoped!) of the starfish bots left behind by the Titans. Cable bundles snaked in all directions, most disappearing into small holes in the walls. A comparatively few cable bundles terminated at the mass driver: the polished metal column and two parallel girders that rose up the vertical shaft. Metal coils attached to the girders encircled the column without touching it. Affixed to the shaft wall alongside the mass driver was a vertical conveyor, unmoving. Far overhead, at the mouth of the shaft, unblinking stars shone like diamond chips.
Pipes as fat as storm drains ran around the periphery, and in and out of the rough-hewn walls. Those walls showed little, if any, of the alien coating he had come to fear: this asteroid was virtually all metal, virtually free of carbon.
Apart, perhaps, from which cabinets had had their access panels removed, and the specific test instruments lying about, the facility was just as he had seen it three days earlier, on his one quick trip down the rabbit hole. But judging by the stony faces, something had changed.
Marcus took a deep breath. “What’s going on?”
“It won’t work,” Ilya said. “This installation. It will not save us.”
“Just the facts, please,” Marcus countered.
“Very well,” Ilya eventually said. “In the big picture, this is a very simple operation. There is the mass driver: an enormous electromagnetic cannon that hurls large metal chunks at very high speed. A payload races up”—pointing—“that shaft and into space; the recoil nudges the Hammer in the opposite direction. Repeat. There is a control function, performed by consoles and components resembling those in what we called the control room of the lunar base. Cables from the consoles penetrate deep into the body of the asteroid. Some of the cables use the metallic mass of the asteroid as a radio antenna, just as we had surmised. And there is a power source.”
Power for the Hammer had seemed the biggest mystery. Solar panels could never have survived the eons on the surface—and indeed, they had found none. Any helium to fuel a fusion reactor would long ago have escaped, just as it had vanished from their ship’s helium tanks. Any uranium or plutonium to fuel a fission reactor would, like the plutonium that had once powered the Olympians’ tracked robots, long since have decayed to lead.
But somehow, the Hammer had responded to the order to strike Earth. It had expended enough energy to change its orbit. Whatever the power source was here, the idea had always been to harness it again.
Marcus prompted, “And what is the power source?”
“Thermoelectric generators. Not all that efficient, at least as we backward humans build them, but very reliable, converting heat energy to electricity without any moving parts to fail. Four such generators, whether for redundancy or added capacity. The heat arrives from whatever part of the asteroid is warmest, via working fluid that circulates through the massive pipes.”
Marcus gestured about the room. “And that electrical energy powers the controls, the radio, and the mass driver. All this.”
“Right.”
“Storing energy in batteries for the electronics, and in a capacitor bank that discharges to fire the mass driver?”
“Right,” Ilya repeated.
“Explaining everything,” Marcus said, “but how the accursed rock aims itself. How did it locate the Sun to aim for the slingshot maneuver? How does it know where Earth is?”
Ilya gestured at a cable bundle that disappeared into a hole in the chamber wall. “I assume, sensors on the surface, at the end of cables like this one.”
“Doubtful,” Ekatrina said. “Surface sensors would have been worn away to nothing over the eons by space weathering, just as it happened on the Moon. Instead, I think, whatever aiming and timing information was necessary came within the radio message from the Moon ordering the strike.”
“Or,” Yun argued, “the necessary sensors lie buried deep inside the Hammer. Solar neutrinos would penetrate easily enough. As for how the Hammer located Earth, I speculate—”
Ilya snapped, “You seriously think that—”
“Forget for now that I asked,” Marcus interrupted. “The Hammer was aimed. How won’t be important unless or until we restart the mass driver.” And maybe not even then. If they could speed up the Hammer along its present path, it would pass ahead of Earth rather than hit it. “So how do we do restart the damned thing?”
Silence.
He tried again. “Three generators remain operational. At least, Ilya, that’s what you reported yesterday. If the capacity of the fourth is needed, we can bring in our portable fission reactor, or run a power cable from the ship. The mass driver works; if it didn’t, we wouldn’t be here. So ….”
“So, nothing,” Ilya barked. “Suppose we learn to operate the controls. Or suppose we work out, by trial and error, to operate the mass driver under the control of our own computer. It still won’t matter.”
The big Russian marched, boot magnets snapping to the metal floor, to the base of the vertical conveyor. Nearby stood a many-jointed robotic arm and perhaps a dozen waist-high spools of golden wire. He slapped one of the spools. “This is a payload for the mass driver. It consists of superconducting wire, precisely wound around a precisely machined spool. Powerful, preci
sely synchronized currents in the coils surrounding the central column of the mass driver interact magnetically with the coil surrounding the spool. That interaction accelerates the payload up and out of the shaft.”
Marcus pointed. “And then the robotic arm clips the next spool onto the conveyor, which raises the spool to the top of the column, where the second robotic arm”—which he had passed climbing down the shaft—“positions the payload, and gives it a nudge down the column. When the payload settles into place, it discharges the capacitor banks to once more trigger the magnetic fields. Repeat. So what’s the problem?”
Ilya thumped the spool again. “The problem,” he shouted, “is the repeat part. These few spools are the only payloads we have found. They are not near enough.”
* * *
Ship’s thoughts were muddled. Reflexive rather than conscious. Reactive, rather than reasoned. It ached to lash out—and was impotent. But instinct suggested capabilities might, once more, regenerate.
And so, from helplessness more than from patience, it bided its time ….
* * *
They’re exhausted, Marcus told himself. I’m exhausted. But the one guaranteed way to fail is to quit trying. “Then we make more spools.” Somehow. “We’re surrounded by metal. Take apart any Titan spool to tell us the mass and physical size to make our own.”
Yun shook his head. “We considered this. I do not know how we would mine the ores, or how smelting would be done in vacuum and almost without gravity, or whether we have the necessary tools. I cannot imagine that we few can undertake such a project in the time that is left. But none of those is our biggest obstacle.”
“What is?” Marcus asked.
Ilya gestured at the shining midriff of a spool. “This. The superconductive coil. How do we make that?”
Marcus’s gut lurched. He had … nothing.
“It is time to go home,” Yevgeny said softly.
Home? Home was about to become a charnel house. Because they had failed. Unless …. “We have plenty of superconductor.”
In the ship’s reactors. In the main drive.
Yun and Katya exchanged startled glances.
Marcus said, “We can die on Earth among billions. Or we can strand ourselves on this rock—yes, and in all likelihood die here—just maybe saving billions. Which is it?”
Yevgeny muttered something in Russian.
“What?” Marcus asked.
Katya laughed. “A rather obscene concurrence.”
“Anyone else?”
One by one, they agreed.
Marcus had just arrived, but the others had been in this pit for most of a day. “Back to the ship, guys. You’ll need more oh-two soon, anyway. Maybe, if we sleep on it, we’ll come up with another option.”
* * *
From their rumpled looks, neither physicist had slept a wink. But when Marcus came upon them in the engine room—drink bulbs in their hands, jittery from untold coffees, datasheets unfolded and dense with abstruse-looking math—they had been up to something.
Marcus downed a healthy swig of coffee from his own drink bulb. “What do you guys have for me?”
“They would not let us bring bombs,” Ilya began. “Fine. We can make a big blast.”
“Build our own nuke?” Marcus guessed. “Impossible. The uranium fuel pellets”—sealed inside their portable reactor, intended not to be accessible—“aren’t enriched to anything near weapons-grade.”
Because why would they be? And if all their uranium were of weapons grade, it would still only amount to a few kilos. That would not produce much of a bang, even if they had the precision tools to machine the fissionable core of a nuke. And even if Ilya or Yun had the necessary expertise. Certainly Marcus had only the vaguest concept of what was involved in triggering a fission explosion. And if those hurdles weren’t insurmountable? No way did they have enough time.
“Fission.” Ilya laughed. “You are thinking too small. We have fusion reactors.”
Yun jumped in. “What was the original plan? To deliver eighty megatons? Of course, we cannot achieve anything close to that yield. Laser implosion of the helium droplets is a technology designed not to make big explosions. But we have each had several ideas how we might overcome that. For example, it seems plausible—”
“Assume you succeed.” Because, Marcus had decided while he was not sleeping, that the five of them whipping up a payload factory for the mass driver was absurd. “Then what?”
Ilya said, “We position the ship wherever the explosion will have the best effect. That might be where we are now docked or, with a more complete survey, we might find someplace better suited. An explosion right on the Hammer, or very near to it, has to be more effective than a warhead exploded at a distance, on a rocket streaking past.”
They were grasping at straws. What else could they do?
Ekatrina and Yevgeny joined them as Yun and Ilya resumed their manic—and incomprehensible to Marcus—debate over which alien safety interlocks might be defeated, and how, and whether both reactors could be rigged to explode simultaneously, or one would go a split-second earlier and destroy the other.
Katya, looking haggard, interrupted. “And us? Is there any hope for us?”
Neither Ilya nor Yun would meet her eye.
Her shoulders slumped. “Well, it will be a fast death. But it would be nice to know first if we had succeeded.”
“Maybe ….” Marcus stopped. The idea sounded loony tunes even for him. But it would be a shame not to know. “Maybe we can offload some supplies and burrow into the rock somewhere. Shelter in a crevasse elsewhere on the Hammer.” And get jellied by the concussion? Or die horribly within hours from radiation? Maybe. Probably. “You and I can hunt for a place to lie low while Ilya and Yun finalize their details.”
Inexplicably, Yevgeny smiled. “I realize I am just the chauffer. But is there not a better use for these reactors?
“Why not use this ship to push the Hammer?”
Chapter 54
While Ilya and Katya tried to devise ways of coaxing a big bang from their fusion reactors—and complementary ways for bypassing safety interlocks meant to prevent any sort of overload from happening—Yun redirected his efforts to calculating whether their ship had the oomph, and if they still had enough time, to gradually nudge the Hammer into an Earth-bypassing orbit. Marcus, assuming they would be tethering the ship along the Hammer’s main axis—and so, in the very maw of the mass driver—wrestled the remaining payloads, one by one, beyond the reach of the robot arm. Because “Even paranoids have enemies.”
And Yevgeny? He rehearsed in his mind, over and over, what must be done if Rescue One were to become a tugboat. The many ways in which things could go wrong. The … wafer thin? atom thin? … margin for any error. Because shoving around a thing more than twelve kilometers long? Massing more than two-trillion tonnes?
This was going to require serious piloting.
* * *
Pop-pop-pop, went the reactors. Hmmmm droned the ship’s main drive. And the hull, every so often, gave out a creak or a groan. Whenever the hull spoke, Yevgeny eased up on the figurative gas pedal. As soon as the sounds of protest faded, he pushed a little harder. Every second in which he managed not to crush the hull was a small triumph.
Because ever so gradually, the Hammer was accelerating. By Yun’s best estimation, a little more than four days of thrust, steadily building up speed, would do the trick.
All very slowly. The limiting factor—math confirming pilot’s intuition—turned out not to be the capacity of the fusion reactors, or the maximum force the advanced space drive could exert, but something more mundane: the stress the hull could withstand before cracking like an egg. To add to their joy, hull strength was a parameter for which they could make only the roughest of estimates.
Scant meters beyond the canopy, weakly illuminated by bridge light
s, was … rock. After two days of this, Yevgeny no longer noticed it. Instead, his eyes flitted ceaselessly from the readout of one accelerometer to that of the next. The slightest evidence of roll, pitch, or yaw meant Rescue One had slipped off the Hammer’s long axis. And then, fingers dancing over his controls, he used attitude thrusters to realign the ship.
Why did the ship tremble and wobble, misaligning the thrust he was so cautiously applying—with who knew what torsion applied to the already stressed hull? Random turbulence in the main drive’s plasma exhaust, Yun theorized. The ship’s center of gravity subtly shifting as people moved about, and water sloshed around in its tank, Marcus guessed. Inevitable rocking, Ilya supposed, as smooth hull pressed into the uneven, and to some slight degree compressible, surface of the asteroid. Tether imbalances, Katya thought, Yevgeny having snapped two of five anchor cables almost immediately, getting a feel for the ship’s responsiveness while its nose ground itself into this gigantic mass!
Useless speculations! Yevgeny eventually demanded that people keep their opinions to themselves. Because whatever the underlying cause, or causes, the factor that must continue to make the ship tilt and sway, as skilled as he was, was that his reaction time would never be zero, was that he sometimes overcorrected, and had to recover from that.
And their nattering did not help.
Bottom line: this piloting was far too delicate for anyone else aboard even to attempt, and their window of opportunity far too brief to allow him any respite. And so he chugged bulb after bulb of coffee. Toilet breaks were out of the question anyway, because he was in a counterpressure suit. They were all suited up, with helmets kept close at hand. Fractures to the hull from the unending strain were all too possible. He was too busy, too focused, to notice the state of his “maximum absorbency garment.” His diaper.
Yevgeny no longer noticed who delivered more drink bulbs and energy bars. After he had chewed someone’s head off, they stopped offering him encouragement, stopped distracting him. It was enough that food and drink did appear. And that in a corner of his datasheet the counter continued to decrement toward success. Two more days of this ….
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