He moved the rocket’s throttle to maximum thrust, and he was pushed back into his seat by four and a half Gs. X-15-1 climbed almost vertically. The sky turned from pearl blue to a rich navy. He was already so high he could see stars ahead of him, in the middle of the day; so high there were only a few wisps of atmosphere, barely sufficient for his plane’s aerodynamic control surfaces to grip.

The sensations of power, of speed, of control were exhilarating.

Ninety thousand feet; thirty-two hundred feet per second.

The Mojave, spread out beneath him, over two thousand feet above sea level, was like the dried-out roof of the world.

Less than a minute into the flight, the problems started.

He got a message from the ground. It sounded like they were losing telemetry from the bird. The trouble was, the voice link had suddenly gotten so bad that he couldn’t tell for sure what they were saying.

A warning light showed up on his panel. Another glitch. For some reason his automatic reaction control rockets had deactivated. It wasn’t too serious yet; he was still deep enough in the atmosphere that he was able to maintain control with the aerodynamics.

The X-15 flew like an airplane in the lower atmosphere. It had conventional aerodynamic surfaces — a rudder and tail planes — which Stone could work electronically, or with his pitch control stick and rudder pedals. But above the atmosphere, the X-15 was a spacecraft. The automatic RCS reaction control system — little rocket nozzles, like a spaceship’s — was controlled by an electronic system called the MH96. And there was a separate manual RCS system Stone could control with a left-hand stick.

Quickly he was able to trace through the fault. The automatic RCS had shut itself off because the gains of his MH96, his control system, had fallen to less than 50 percent. The gains were supposed to drop when the plane was in dense air; then the MH96 was designed to shut itself off, to conserve hydrogen peroxide rocket fuel. But the gains had dropped because the hydraulics which controlled his aerodynamic surfaces were stuttering. So the automatic control system couldn’t rely on the data it was getting, and it had shut down the automatic RCS.

It looked as if the electrical disturbance that had started with the radio was spreading. Looks as if we might be snake-bit, old buddy.

Well, he was close to the exhaustion of his rocket fuel anyhow. He pressed a switch, and the engine shut down with a bang.

He was thrust forward against his straps, and then floated back.

He had gone ballistic, like a hurled stone; X-15-1 would coast to the roof of its trajectory, unpowered. He lost all sensation of speed, of motion. He was weightless inside the cabin, and he felt as if his gut were climbing up out of his neck.