emerged from the shadow of the bomber’s wing, at forty-five thousand feet, into a shock of brilliant sunshine. He was already so high that the morning light was electric blue, more like dusk. The chase planes were little points of silver light around him, with their contrails looping through the air.
The land curved below the plane’s nose, as if the Mojave was some huge, smooth dome. He could see the worn hump of Soledad, the Lonely Mountain, brooding over Rogers Dry Lake, half a mile above sea level. Everywhere the dried-up salt lakes glistened like glass, speckled with gray-green sagebrush and the twisted forms of Joshua trees. It was a flat, desolate, forbidding place. But every summer the desert sun baked the damp lake beds to a flat and smooth surface. The whole place was like one huge runway, and you could land anywhere in reasonable safety.
It was a little after ten thirty in the morning.
Stone pushed the button to ignite the X-15’s rocket engine.
He was kicked in the back, hard. The plane’s nose was tipped up into the sky as ammonia and oxygen burned behind him, and he rode higher into the deepening blue. He could hear his own breathing inside his helmet; otherwise, there was barely a sound – he was outpacing the noise and exhaust plumes behind him.
Far ahead he saw a speck of light, like a low star. It was a high chase plane. It grew out of nowhere in a flash, and plummeted backwards past Stone, as if it was standing still.
At forty thousand feet he reached point nine Mach, and he could feel a bumping, like a light airplane flying in turbulence. He was moving so quickly now that the air molecules couldn’t get out of the way of his craft in time.
The turbulence smoothed out as he went supersonic.
Eighty thousand feet.
He moved the rocket’s throttle to maximum thrust, and he was pushed back into his seat by four and a half G. 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 got 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 for now; 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 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 fifty per cent. 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 this time 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; now 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 was climbing up out of his neck.
He tried to put the problems aside. He was still flying, still in shape. And, no matter what was happening to the MH96, he had a program to work through, a whole series of experiments for NASA and the USAF.
One minute forty-one.
He activated the solar spectrum measurement gadget, and the micrometeorite collector in his left wing pod.
Suddenly, the MH96 control system’s gains shot up to ninety per cent, for no apparent reason, and the automatic RCS cut back in.
He checked his instruments. Like most experimental aircraft, the X-15’s cockpit had a primitive, handmade feel, with rivets and wires showing. Well, it seemed he had full control ability for the first time since entering his ballistic flight path. He welcomed the return, but he was unnerved, all over again. What next?
He had very little confidence left in this battered old bird. Maybe she knows it’s her last flight; maybe she’d prefer a blaze of glory to a few decades rusting in some museum.
He would soon be going over the top, the peak of his trajectory, at two hundred sixty thousand feet.
It was time to begin the precision attitude tracking work required for the solar spectrum measurement. He needed a nose down pitch, and a yaw to the left. He was already flying at almost a zero degree angle of attack, but was yawing a little to the right, and rolling off to the right as well. So he fired his wing-mounted roll control thruster for two seconds to bring his wings level, and his yaw control thruster to bring the X-15’s nose around to the left. The X-15 was like a gimbaled platform, hanging in the air, twisting this way and that in response to his commands. To stop the left roll he fired another rocket –
He was still rolling, too far to the left. Christ. What now?
The MH96 had failed again, and had cut out the automatic RCS, just as he was completing his maneuver.
He continued to rotate. To compensate he held his right roll control for eight more seconds. But the air was so thin up here that his aerodynamic controls were degraded, and the response was sluggish. He fired his manual RCS yaw rockets.
He could feel sweat pooling under his eyes; one problem after another was hitting him, blam blam blam.
Suddenly the MH96 cut back in with its automatic RCS. That stopped his yaw, short of the correct heading. Stone fired his manual yaw again; this time as he approached the reference heading the yaw was countered by the automatics, apparently correctly – but now the damn thing cut out again, and he yawed past the reference.
And now, on top of that, his roll attitude indicator ball was rotating. He had started rolling to the left again. He tried to wrestle that back with three short pulses on the manual roll RCS, but he overshot, and started a roll to the right …
Fifty
