David Brin - The Heart of the Comet

—Every crew’s ahead of schedule. Even puttin’ in extra time, without me askin’.—

“We’ve finally got something to work for.” Carl said it without meeting Jeffers’s eye.

—Damn right.—

A manager-mech approached, an extra dome perched atop its carapace in a makeshift kluge. Virginia’s add-ons worked marvelously, making the mechs and robos far more versatile, but they weren’t elegant. The mech winked its lamp to attract their attention and sent,— Launcher 6 complete. Human tech Osaka states that the device is ready, for formal testing.—

Jeffers nodded.—Fire the sucker!—

Warning gongs sounded over the comm line. Everywhere on the surface, teams stopped work and climbed out of pits to watch. Their suits were scratched, worn, discolored, patched with homemade parts.

A ping ping ping of warmup rippled over the comm frequencies, thin ringing echoes of the charging now under way in the trench. Carl peered at the tip of the launcher, which jutted free of the ice nearby, pointing at the sky.

He felt prickly excitement, gathering tension. If they’d made some mistake in the design, in assembly…

A small tremor came through his feet. A rattle in the microwave, a skreee —and the unit discharged.

Simultaneously, a vague haze appeared et the mouth of the launcher. He wondered what was wrong, until he suddenly realized that the firing rate of the flinging tube was several capsules per second— and he was seeing the blur of their passing.

That was all. No roar, no belching smoke. The launchers were designed to operate with near-perfect efficiency, to generate as little waste heat as possible. If even a fraction of a percent of the launching energy seeped into the surrounding ice, it would evaporate away the structural support, producing dislocations, unbalancing the carefully configured momentum-matching of the accelerator segments. Long before the ice was gone, the ratcheting instability of the drive tubes would jerk and thrash them into twisted steel.

But the flinger functioned smoothly. A cheer rose across the comm lines. People raised their arms in victory salutes as far as Carl could see, dancing on the grimy ice, leaping high into the blackness. Only the mechs continued stoically about their tasks, oblivious that humans had at last clasped the helm of this ice ship. Halley was no longer just a tumbling dirty snowball in the long night. She was now a spacecraft.

Jeffers was babbling excitedly, repeating operating parameters as he read them off his helmet display. Carl could follow some of the rapidfire reciting— kilo-amperes surging in low-impedance circuits, voltages building to sharp peaks and then collapsing as each slug passed, leaching the energy of inductive electric and magnetic fields. Energy poured into the capsules, electrodynamic momentum flowing like a fluid at the speed of light.

Only electrical acceleration was efficient enough to avoid the waste-heat problem, to avoid slowly melting the comet itself. For the moment there were ample piles of iron at the north pole, mined in the first year of the expedition, but deep beneath each launcher was a mech mining operation, where in constricted caverns the robots dug and processed more of the comet’s natural, ancient metal.

A factory on A Level made lightweight buckets of a special superconducting polymer. These were loaded with iron and other heavy wastes. Each metal-filled dollop became a bullet. Conveyors fed these with unrelenting precision into the flinger barrel, where the surging voltages clasped each pellet and flung it to enormous speeds— ten thousand kilometers per second, nearly three percent of the speed of light. Launcher 6 was a cosmic machine gun, firing slugs that would reach the nearest stars in a few centuries.

We could have built starships, if we’d only had the nerve, Carl thought. Maybe someday.

Such was the mass of Halley that even these enormous speeds were barely sufficient for the task of piloting. Carl tuned in to an engineering frequency and herd a staccato braaap braaap braaap as each pellet picked up its miniboosts in the flinger column. Launcher 6 was the first of fifty-two that would soon ring Halley, stuttering forth their kilogram pellets for five years. Aphelion, when the comet head paused like a ballet dancer at the peak of his leap, was the most efficient time to divert Halley. Fully ten millionths of the comet’s entire mass had to be ejected. That demanded dozens of mechs supervising the mining and smelting of iron, minirobots to toil beside the endless conveyor belts, subroutines and expert programs to catch every snag, each hitch in the unending stuttering fever of the Nudge.

“Goddamn,” Carl said. “It works.” He felt a rush of relief and realized he had been clenching his hands.

The cheering went on. Even this demonstration, which would run for a mere few hours, was slowing Halley’s primordial spin, minutely altering its long gliding ellipse.

—Runnin’ smooth, too,—Jeffers said, grinning happily.

—Come on down to Launcher Five. I’ve got a nice li’1 pivot rigged there, keeps the flinger tube from comin’ unglued. We figured—

Jeffers stopped abruptly as a geyser of steam boiled from an ice tower nearby. Vidor’s intricate cross-hatching of blue and ivory exploded in a shower of fog and glinting, tumbling remnants.

—Goddamn!—

—What? What’s happenin’?—

“Laser!” Carl flattened himself against the grimy ground. “Get down everybody!”

—What the hell— who’d go and—

“Arcists!” Carl realized “They must’ve heard the successful test over comm.”

Jeffers shouted,—But why? I thought Quiverian agreed .—

“Damned if I know.”

All across the field, people were ducking for cover. An ice tower farther away dissolved silently into mist. This time Carl saw the flash of light as the beam struck.

“They’re firing from that hill— over there. South twenty-five degrees of west.”

Jeffers squinted at a distant speck atop a heap of leftover slag from one of the mining operations.

—They moved one of those big industrials. Tryin’ to hit Six, but those things, they don’t aim all that good.—

The comm rang with outrage.

A bolt gouged into ice near a crouching form and Carl heard a startled tied cry of pain.

“Takeda! Get that woman sealed and to first aid!”

Carl crouched behind a hummock and watched fierce laser bolts send fountains spurting skyward. “Bastards!”

—We gotta do somethin’.—

“I could have Virginia send some mechs around behind, outflank them…”

—Yeah, right,—Jeffers said.

“No, wait…” He checked Virginia’s channel. A hiss. It was cut off. Of course. Only an idiot would attack without cutting off the defender’s source of support.

Another wail of pain over the comm.

Carl nudged Jeffers’s shoulder. “Launcher Six-can you pivot it?”

—What?—

“Tip Six down? Aim it at the horizon?”

Jeffers looked surprised.—The safeties aren’t in. I dunno… that’s a pretty low angle.—

“Try it!”

As Jeffers crawled into the launcher trench, the ice-tower fulcrum for Launcher 5 exploded behind them, sending cables and cowlings into a slow, fluid fall to the surface. Lost components, lost construction time, hurt crew— people who were his responsibility. Carl glowered at the distant dots working around the laser cannon, a murderous anger building in him.

He tuned out the comm channels, where voices swelled and swamped one another. People called for lovers and friends, sputtering in impotent rage. Mechs asked innocently for orders. Then Virginia’s voice intruded on his private line.—What’s going on ? Somebody jammed my channels. Who…?