The biconic was deep enough into the atmosphere, on this computer-generated dive, for the pressure to have rendered the forward attitude rockets useless. And the atmosphere would be almost thick enough for the biconic’s control surfaces to start biting into the air.

York realized that the biconic was a peculiar, unprecedented mix of spacecraft and aircraft.

“Dynamic pressure twenty pounds per square foot,” York said. “One hundred twenty thousand feet.”

“I got it,” Gershon said.

Then the last thrusters were switched off. The craft had become a glider, with only its aerodynamic control surfaces to maintain its attitude and trajectory.

The glow outside her window reached its peak, racking up through pink and yellow and blue-white. Actually the colors changed in visible clunks, as the computer changed over its filters.

Gershon worked at his stick and pedals, the biconic’s oddly old-fashioned aerodynamic control system. “The response seems sluggish to me.” He pushed the stick forward. “I’m trying to descend. The elevons have gone down, the rear has come up. I don’t feel a damn thing. Fucker. There we go. I overshot. Okay, bringing her up. Arresting my sink rate. Back on the stick. Elevons up, lift dumped, back end dropping down. Shit. Where’s the response… Oh. Here it is. I’m wallowing like a hog in mud.”

The biconic would be slow, clumsy, heavy to handle by comparison with most Earthbound aircraft, York knew. Flying the biconic was more like guiding a boat; you just had to rearrange your control surfaces and wait while the new configuration bit at the stream of thin air, and slowly changed your momentum.

“One hundred and three thousand feet,” she called.

“Here we go,” Gershon said. “First roll reversal coming up.”

In the electronic imagination of the computer, the biconic banked through eighty degrees to the right. York watched the tilting landscape; the plaster of paris appeared to quiver as some fault in the TV camera’s control mechanism made the tracking shudder.

The biconic was designed to go through a series of S-shaped turns in the upper atmosphere of Mars. The flight path was a question of budgeting: the craft had to shed all of its orbital energy by the time it reached its landing site, but on the other hand, at any point in its trajectory, the craft needed to maintain enough energy to reach that landing point. So the craft had to manage the lift generated by its biconic shape, together with the kinetic energy of its descent, to shed heat and reach its target…

“Overshot,” Gershon muttered. “Eighty-five degrees. Eighty-six. Banking left to compensate. Come on, SimSup. Is this where you hit us? Banking left. Okay. Here we go. Okay. First roll complete. Here we go. Second roll reversal.” Gershon’s voice was tense, his movements fast, mechanical.

He takes these games too seriously, York thought.