Greg Egan - The Clockwork Rocket

Yalda braced her tympanum.

“ Eight. ”

In less than a flicker the wave of compression came hurtling back up through the rock. Through the bench she felt the first insistent tremor from the nearest ignition points, then the pounding of ever more engines reached her until even the most distant were hammering at her body. For one terrified moment she could discern no change in her weight—her skin reported nothing but the bench’s vibrations—then she tried to raise an arm and was rewarded with unambiguous resistance, easily overcome but enough to banish her fears. If the engines had been too weak to lift the mountain, she would not have felt this. No amount of ineffectual flame and fury, no mere buffeting and shaking, could have mimicked the glorious signature of acceleration.

Belatedly, she checked the balance beside her, isolated in a vibration-deadening frame from the jittering floor. The polished hardstone scrood-weight was stretching the spring by close to twice the original amount, putting the thrust within a notch of its intended value. There could be no doubt that the Peerless was rising, climbing ever faster into the sky.

Chilled air flowed through the room; the cooling system was working. Not only had the mountain failed to collapse into smouldering rubble, or squat on the ground building up heat until it set the world on fire, it wasn’t even going to cook its passengers alive.

Yalda’s relief turned to exhilaration. She tried to picture the events below: flame spilling out from the hole the severed mountain had left in the ground, hot gas and burning dust swirling across the plain to engulf the empty buildings of Basetown. If she envied Eusebio anything now, it was the sight of a dazzling white streak of fire splitting the eastern sky, when all she had before her was this trembling red-lit cave. But no matter; she’d write him a note and have it carved in stone to be passed down the ages: You witnessed the launch in all its splendor, but when I looked down on your world it was small as a pebble.

The room shuddered; Yalda was thrown sideways in her restraint, her euphoria banished. She looked to the gyroscopes at the center of the room, struggling to interpret their quivering. She’d sat with Frido and Eusebio, calculating the motion of these devices under all manner of calamities, but now her mind was blank and she couldn’t match what she was seeing to any of those predictions.

Babila caught her eye with a series of symbols on an outstretched palm: One engine failed, but we’ve recovered.That made sense; if the rocket had remained unbalanced and the mountain had started tumbling, the axes of the gyroscopes would have ended up far from their starting markers. The machines feeding the other engines had detected the incipient swerve, and those positioned to compensate were doing so.

One feed had malfunctioned, out of three dozen. That was no worse than the proportion of recruits who’d pulled out. The machinists responsible for it wouldn’t even leave their benches to attempt repairs while the engines were still producing extra thrust, laboring to overcome the world’s gravity. This was failure at a level they’d anticipated, not an emergency. It could wait the six chimes until their weight became normal.

Yalda checked the clock; a single chime had passed. The Peerless would be about a separation above the ground now. She longed for a window—and some magic that would make it worthwhile by granting her a view through the flames—but even the lucky people in the highest observation chambers would only be able to see the distant horizon, gradually shrinking until it was obscured by the glare of the exhaust. By the time their path had curved sufficiently to allow them to look back on their starting point, the world really would appear as small as a pebble.

The room lurched again, a sickening swing abruptly curtailed. Yalda steadied herself and peered anxiously at the gyroscopes; the rocket remained level. Had a second engine cut out, or had the first recovered spontaneously? Even two dead engines didn’t threaten their stability, but ongoing failures at this rate certainly would. Whatever had happened, the machinists on site would leave their benches now, make inspections and report.

Yalda looked across at Frido; he signaled tersely: Patience. Until they had more information there was nothing the navigators could do. The Peerless was still under control, and still ascending at close to the target rate. If that much of their luck continued, in two more chimes they’d reach the point where they could shut down all the engines without fear of plummeting back to the ground. In a wide, slow orbit around the sun, they could assess the situation and make repairs. Dispiriting as such a setback would be, better a delay and some damage to morale than have the Peerless turn into a spiraling firework.

For a third time, the rocket staggered and then caught itself. Yalda felt as if she were back on the footbridge over the trench, paralyzed by the sight of the abyss beneath her—and watching the ropes that supported her snapping one by one. Where were the reports from the machinists? She stared at the bank of paper tape writers connected to the signaling ropes. Though the devices had never been used outside the Peerless , they’d proved invaluable during the construction phase. Only adjacent chambers were connected directly, but messages that needed to go farther could be relayed from chamber to chamber. These particular units had been tested thoroughly—most recently when the machinists had first reached their stations prior to the launch.

Finally, one writer began disgorging a message. Babila could reach it without leaving her bench; she grabbed the end of the strip and peered at it, frowning, before the message was complete. Having the thing print actual symbols would have made it too complicated, so they’d devised and memorized a simple code that could be transmitted by tugging on either of two ropes.

From chamber four, Babila wrote on her palm, stretching her hand to fit more words. Feed stopped. Waiting. Chamber four was out at the rim; the message had reached them via two intermediaries.

That would have been the first failure, with the machinist following the protocol and delaying inspection until the thrust was reduced and movement became easier. But then almost immediately, another message arrived: From chamber three. Feed stopped. Investigating.

Chamber three was also at the rim, right next to chamber four. What source of failure, Yalda wondered, could depend on proximity? Dust from construction rubble—somehow missed in all the inspections—shaken out of its hiding place and rendered airborne by the vibrations?

That made no sense, though. Coarse enough debris might jam the clockwork—delaying the feed’s opening in the first place—but Yalda was sure there was no part of the machinery where grit in the cogs could cause the feed to close once it was already open.

Chamber four, then chamber three… she wasn’t going to wait to learn where the third failure had been. She held up her hand to Babila. Message to chamber two, and all its neighbors: Make a full inspection.

Babila started working the ropes. Frido caught Yalda’s eye.

Sabotage?he asked. His face bore an expression of disbelief. This was not a scenario they’d anticipated.

Just being cautious, she replied. Whatever the cause of the first two failures, it could do no harm to test the assumption that their proximity was more than a coincidence.

Yalda turned to the clock; in a couple of lapses they would reach planetary escape velocity. The protocols dictated that three failures was the limit; one more and she’d have no choice but to shut down all the engines as soon as it was safe and let the Peerless drift around the sun until they’d diagnosed and remedied the problem.