But the roar built up, and so did the vibration — every loose fitting seemed to be clattering around him — and now came the sense of acceleration he’d expected, almost comforting, pushing him hard into his couch.

The bunker spoke to Geena, and she responded, her voice deep and shaking with the vibration.

Henry wished he had a window, or a periscope. He wished he could see Kazakhstan falling away as if he was in some immense elevator; he wished he could see the great plains of central Asia opening up beneath him.

The acceleration continued to mount. He closed his eyes. Simple physics, Henry told himself. Acceleration equals force over mass. As the fuel load decreased, the mass went down, the acceleration had to grow… But knowing what was going on didn’t help relieve the pain in his chest, the heaviness of his limbs.

When he opened his eyes again he could hardly make out the instruments, so severe was the vibration.

There was a series of clattering bangs on the outside of the hull.

Geena shouted, “There goes the escape rocket. And now—”

And now another jolt, much bigger, fundamental. Henry knew that must be the clustered first-stage boosters dropping away. Now only the centrally-mounted main engine was burning.

The thrust built higher, smoothly.

“Thirty miles high,” Geena said.

Another clatter from the cabin hull, and suddenly the faring was gone. No longer needed, Henry realized, because they were already above most of the air.

The windows were clear. There was a shaft of yellow sunlight, lying across his spacesuited lap.

He looked right, through his Captain Nemo window.

There was a loose snow, drifting past his window: ice, breaking off the hull of the capsule. They were so high now there was no air friction; only the ship’s steady acceleration carried him away from the ice fragments as they spun.

The second stage rocket died with a bang.

The acceleration vanished. Henry and Geena were thrown forward against their restraints, two puppets, helpless in this steel fist. A second of drifting. The ticking of the cabin instruments, the cooling creak of the hull.

Then came another bang as the final stage lit up, and they were slammed back into their seats. The acceleration soon built to the most ferocious of the launch.

There was nothing smooth about rocket flight, Henry realized, nothing gradual. It was all or nothing.

He glanced at the clock. Less than eight minutes ago he was still sitting on his back on the pad—

The third stage cut, in an instant. Henry was thrown forward against his restraints. He gasped. His chest was sore, probably bruised. His back hurt.

One instant the stage had been burning as hard as it ever had, the next it was dead.

But there was no more rocket fire, no more lurches of acceleration. It was, it seemed, over.

The light shifted across his lap.