Donald Moffitt - Genesis 02

pointed that out.
    “You do everything by the list when you ride with me,” Lydis said. “Otherwise, you can get out and walk.”
    Grumbling, Jao complied.
    “It’s surprising, the number of things that can go wrong,” Zef said cheerfully. “Why, I saw a fellow explode once because he forgot to screw his helmet on all the way and nobody’d told him the cabin wasn’t going to be pressurized that trip.”
    “Oh, stow it,” Jao said. “I’m not falling for any more of your stories.”
    Zef laughed. “It’s not that we care about the safety of our passengers. We just don’t want a lot of helmets floating around and bumping into things.”
    Jao started to reply, but his voice was cut off as Lydis watched the passengers off the Talk circuit. Abruptly Zef dropped his smile and became all business. Bram found himself gripping the armrests of his couch. Drop must be imminent.
    He was still plugged into the Listen circuit, though. He could hear Lydis talking to Jun Davd back in the observatory.
    “I have your readout,” she said. “Please confirm.”
    “Three minutes more and you’ll be in optimum drop position. As tangent as you can get. Do you want the computer to open the trapdoor for you?”
    “No, I’d rather do it by feel. The computer doesn’t have nerves in its bottom, and it has too much faith in the invariance of mechanical systems. I’m going to have to make a lot of small burn corrections, anyway, once we’re out there. Just keep feeding me the figures.”
    It was a point of pride with Lydis to be in fingertip control. She believed piloting was an art, not a science.
    “A computer with nerves in its bottom!” Jun Davd chuckled. “My goodness. We’ll work on it.”
    By craning his neck, Bram could see one of the duplicate screens left over from the original Nar installation, next to the observation blister closest to him. In a simplified computer cartoon it showed a great dull-red disk, slightly angled to give a sense of perspective, and a jolly little green representation of Yggdrasil, much out of scale, floating above and to one side of it. Discreetly flashing and dotted lines showed the direction of rotation of both bodies and their intersecting orbits around the rice-grain sun shining through a cluster of red lobes at the center of the system.
    It obviously hadn’t been very practical to put Yggdrasil into orbit around the rim of a disk-shaped body with a circumference of two hundred seventy million miles. And parking Yggdrasil sixty degrees ahead of the disk—at the stable point which in this crazy system neatly coincided with the point of equilibrium with the disk ahead of it in orbit—would still have placed them an inconvenient forty-five million miles away from the forward edge of the disk and all of one hundred million miles away from the present “top” of the disk, which they had chosen as their likeliest base of operations.
    So instead, with Jun Davd’s help, Bram had put Yggdrasil into a solar orbit that intersected the disk’s orbit at a tilted angle. It started above and behind the disk at a distance of only a few million miles, slanted down at a tangent that almost grazed their target point on the rim, and continued on past to a point ahead of the disk in orbit that would place Yggdrasil directly “above” the spot where the disk’s own slow rotation would have brought the explorers’ base of operations by that time.
    Thus, for at least the first half year, travel time between Yggdrasil and the main landing site would be measured in days rather than months. At that point, Yggdrasil’s solar orbit could be converted into a powered orbit around the rim, which would take it back to its starting point for another such orbital stern chase.
    Bram kept his eye on the pulsing orange line that emanated from the tiny cartoon Yggdrasil on the screen and ended tangent to the disk. It represented a vector of the momentum that would be imparted by Yggdrasil’s own orbital motion plus the added kick from Yggdrasil’s rotation at the moment of release.
    Lydis would add her own increment of momentum by firing the spacecraft’s engines once she was in a position to judge how well lined up she was. Then she would have to cut it fine at the other end, killing all her pseudoorbital velocity and matching the speed of her target on the rotating edge of the disk—so that the net cancellation of both would come out even at the precise moment of touchdown.
    No wonder she didn’t