Scientist-astronauts no longer had to slog through the hell of flight school. But they still needed to go through dynamic situations: to gain experience of microgravity and acceleration, to recognize the symptoms of airsickness and hypoxia. So, the price the scientist-astronauts had to pay was regular hours of flying backseat in a Northrop T-38, the most advanced jet trainer.

Experienced astronauts were encouraged to take up the rookie scientists. And once you were up there, they could do whatever the hell they liked with you.

But she trusted Stone. She appreciated the fact that he was taking time out of his own Moonlab/Soyuz training for this piece of nursemaiding.

“How about that,” Stone said. “Forty-eight thousand feet. Higher than you’ve ever flown before, Natalie.”

So high she was already in the stratosphere, higher than the tallest mountain, so high she couldn’t breathe unaided. The edge of space, right? Welcome to your new home, spacegirl.

“Okay,” Stone said. “Let’s start gently. We’ll slow her down. Can you read the airspeed?”

“Sure.”

“Follow what I do.”

When the jet got to under two hundred miles an hour, it bucked and juddered, as if the air had become a medium of invisible lumps.

“She doesn’t like being reined in,” Stone said. “So—”

He opened up the throttle and the plane surged forward. Sunlight gleamed from the carapace around York, and the Earth curved away beneath her, brilliantly lit.

“Slow roll,” Stone said.

The Earth started to tilt, sideways. It wasn’t as if she was rolling at all; York felt only a slight increase in the acceleration pushing her into her seat.

The horizon arced around her, tipping up, and the bruised purple of the stratosphere slid beneath the belly of the plane.

Then the plane righted itself, sharply. The roll had taken maybe fifteen seconds.

“Snap roll,” Stone said.

This time the plane twisted over in a second, land and sky and sun rolling around, the light strobing across her lap and hands. Her stomach resisted the roll as if she were suddenly filled with mercury.

After one and a half turns the plane finished upside down. When she looked up, she could see the Gulf of Mexico, set out like a huge map painted across a misty ceiling. Gravity plucked at her — one negative G — and her shoulders strained against the seat harnesses, and her helmeted head bumped against the canopy. The blood pooled in her head, making her feel stuffy, as if she were developing a cold.

“Just like the tilt table, huh, Natalie,” Stone said drily.

He snapped the plane through a fast half roll, righting it; the plane settled onto the level, rocking slightly in the air.

For a second they were still. Stone’s precision and control were remarkable, York thought -

And then Stone threw the plane down on a dipping curve, diving down toward the remote ground; the noise of the jets increased.

“Parabolic curve,” Stone called over the jet noise.

So I should be weightless. She relaxed her arm, and watched her hand drift upward. “My God.” She felt the weightlessness in her gut; it was as if her organs were climbing upward, inside her chest cavity.

“You feeling queasy?”

“A little.” She reached down, checking that she could reach the bag in the pocket on her flight suit leg.

Stone made no signs of taking the plane out of its dive. “Ah, you’ll be fine. If it gets too bad, just watch the instrument panel; don’t look out of the window.”

“Okay, but—”

Her sentence fell apart as Stone threw the plane into a ferocious S-shaped curve. She was turned every which way, and the glowing landscape wheeled around the canopy.

And then he took the plane into a straight dive, accelerating at the Gulf of Mexico. The ocean shone like a steel plate, far in front of her face.

At twenty thousand feet Stone hauled the nose of the plane upward. The jets howled, and the Gs shoved her hard into her seat; her head was pushed into her shoulders, and her vision tunneled, walled by darkness.

The T-38 leapt back up to the sky, and the light reverted to its deep purple.

She tasted saliva at the back of her throat, sharp, like rusty iron. “Phil, I don’t feel so good.”

“If you have to barf, take off your oxygen mask.”

I would if I knew how.

“And turn the mix in your mask to a hundred percent 02,” he said. “Turn on your cold air blower.”

When she tried that, taking deep breaths of the oxygen, the pressure on her throat lessened.

“Anyhow,” he said, “you wouldn’t want to miss this next part.”

“Huh?”

At forty-five thousand feet, Stone lit the afterburner. Over her shoulder York could see white condensate blossoming behind the T-38. She watched the airspeed climb up toward six hundred miles an hour, higher, higher.

And through Mach 1. Jesus.

There was the mildest of vibrations, and then the ride got a lot smoother. The noise of the jets died to a whisper; the plane was traveling so fast, York realized, it was outrunning its own sound.

The cockpit was a little bubble of serenity, of cool, easy flying; meanwhile, she knew, sonic thunder was washing down on the ground below. A few feet ahead of her there was Stone inside his own canopy, the only living thing within miles of her, and around them the plane was a little isolated island of reality, gleaming paint and warm air and hard surfaces, up here in the mouth of the sky. She felt somehow closer to Stone, as if bonded to him.

“How you doing now?” Stone asked, his intercom voice loud in the stillness.

“Oh, good, Phil,” she said. “I’m good. This is—”

“I know.” He glanced over his shoulder at her, his eyes concealed by his sunglasses. “And in orbit, you’ll fly twenty times as fast, many times higher. Maybe now you’ll understand better why some of us get so hooked on this stuff.”

She grimaced. “Is my disapproval that obvious?”

“To me it is. I don’t blame you. But you’ve got to learn to understand the other guy’s point of view.”

Suddenly she felt defensive. “What do you care?”

He laughed, evidently not taking offense. “More than you think, maybe. Natalie, I’ve seen you work around the Office. I think you have potential. I think we need people like you in the program. But you have to learn to work in a team.”

He threw the plane suddenly into a new series of dives and barrel rolls.

York pulled out her bag and sat in misery, staring at her knees, while the world wheeled around her.

The T-38 approached the runway like a falling rock. The landing, when it came, was soft and quick.

The techs helped York out of the cockpit. Her queasiness had gone already, but she felt disoriented, as if she had grown smaller, lighter; she felt oppressed by the heavy sky above her, the hot, moisture-laden air.

Stone slapped her on the shoulder. “You did good,” he said.

“I nearly threw up.”

“But you didn’t. I told you you got potential, York.”

“Yeah. Maybe.”

Standing there on the mundane tarmac of Ellington, she looked up at the lidded clouds, remembered how it had been, in those few seconds, to be weightless. She let her hands drift up from her sides.

Stone was watching her, observing, evaluating.

Embarrassed, she tucked her helmet under her arm, nodded curtly to Stone, and headed for the personal gear room.