A multicolored map appeared on the smart screen on the galley’s far bulkhead. Thin yellow lines looped across its gridwork background. Pauline realized that they were the orbits of major asteroids. A pulsing red dot was at its center.
“The red clot is us,” Theo explained. “And here’s our current trajectory…”
A blue curve arced outward. The view enlarged to show
“I’ve gone through all the numbers a dozen times—”
“We both did,” Angela said, without a hint of rancor.
He dipped his chin in acknowledgement of his sister. “And here’s what we might be able to do.”
A dotted blue curve appeared, much shorter than the solid one.
Theo explained, “The nav program shows that we can get back to Ceres in a little more than four years if we fire the main engine and decelerate the ship.”
“Four years, two months and sixteen days,” said Angela, looking almost happy about it. “Right, Thee?”
“Right. Give or take an uncertainty of five percent.”
“Couldn’t we make it less than that?” Pauline asked.
Theo grimaced, then answered, “We don’t have the fuel for a longer burn, Mom. This maneuver’s gonna use up our last drop of hydrogen.”
Pauline thought about that for a moment. “You don’t mean
“All of it, Mom. Down to the last molecule.”
“But how will we generate electricity if we use all the fuel? The reactor needs hydrogen.”
“That’s the risky part.”
“We can’t run for four years without electricity! We couldn’t last four days.”
“I know. But we have water.”
“Drinking water,” Pauline said. “Which we need.”
“We recycle it,” said Angela.
“But what’s our drinking water got to do with hydrogen for the fusion reactor?” Pauline asked. She was fairly certain she knew the answer but she wanted to hear what Theo had come up with.
Theo gnawed on his lip for several heartbeats. With a glance at his sister, he explained, “Here’s what Angie and I have figured out. Water contains hydrogen. We electrolyze some of our water and feed the hydrogen to the reactor to keep it going.”
“We use the electricity that the reactor generates to split the water into hydrogen and oxygen,” Angela added.
Pauline felt confused. “Now wait a second. You use electricity from the reactor to produce hydrogen fuel for the reactor?”
They both nodded.
“It sounds…”
“It’s a bootstrap operation, I know,” said Theo. “But the numbers show that it could work.”
Angela said, “The hydrogen fusion produces a
“Something about this doesn’t sound right to me,” Pauline insisted.
“Angela’s right, Mom,” Theo replied. “The fusion process produces a lot more energy than it takes to electrolyze the water. We’ll be on the happy side of the curve.”
“You’re certain of this?” Pauline asked.
Again Theo hesitated. Then he said, “That’s what the numbers show.”
“Then why can’t we produce enough hydrogen to feed the main engine and get us back to Ceres sooner?”
“Propulsion needs reaction mass, Mom. Our hydrogen doesn’t just generate electrical power; we use most of it to push through the engine’s jets and provide thrust.”
“That’s what most of the hydrogen in our tanks was for,” Angela chimed in. “Reaction mass. Only a fraction of it goes to generating electricity.”
To make sure she understood what they were telling her, Pauline said, “So you think you can generate electrical power for the ship even after you’ve used up all the hydrogen in the fuel tanks.”
“Yes.”
“And cut our trip time in half.”
“Just about.”
“And the risk is…?”
Angela said, “The risk is that we might use up too much of our drinking water to keep the reactor generating electricity.”
“The reactor doesn’t need all that much fuel to generate electricity,” Theo explained. “A glassful of water can produce enough electricity to keep the ship running for a month, just about.”
“Fusion’s a powerful thing, Mom,” said Angela. “It’s what powers the stars, y’know.”
Pauline looked from her daughter’s eager face to her son’s more somber expression. Theo looks so much like his father now, she thought.
“We can do it, Mom!” Angela urged. “We can get back to Ceres in four years!”
She’s so anxious to get back to civilization, Pauline thought. But what if we use up all our water before we get back?
“Theo,” she asked, “do you really think this will work?”
“That’s what the numbers show,” he repeated.
“But what do
“I think we can do it, but it’s not just up to me. We all have a vote in this.”
“Let’s do it!” Angela said.
Realizing she would be outnumbered if she decided to vote against the scheme, Pauline made herself smile at her children.
“All right,” she said slowly. “Let’s try it.”
CARGO SHIP
INFIRMARY
It was weird, knowing that the medic was the captain’s cloned daughter. Victor allowed her to put him through the scanners for a thorough physical, then sat in a soundproofed cubicle for more than an hour with the psych computer, answering questions while hooked up to blood pressure, voice analysis and other stress sensors. Finally he went through the thoroughly unpleasant experience of having his blood pumped out of his arm, through a detoxifying dialysis machine, and back into his arm again.
The medic said barely a word to him through the whole long procedure. At last she pulled the tubes from his arm and sealed his wounds with medicinal spray-on patches.
“You’re free to go now,” she said in her near-whisper.
Victor swung his legs off the gurney, got to his feet and took a deep, testing breath. He felt good, no shakes, no weakness.
“I’m sorry I got you into trouble,” he said to the medic.
“It was my own fault,” she replied, hardly looking at him. Then a tentative smile emerged on her face. “She doesn’t stay angry very long.”
“Your mother?”
The medic nodded. “The captain.”
“Well,” he said, “thanks for everything.”
Her eyes evaded his. “Good luck.”
It wasn’t until Victor had left the infirmary and was halfway along the passageway that led to the ship’s galley that it struck him that “Good luck” was a strange thing to say. What did she mean by that? he
