Robert Heinlein - The Rolling Stones

Dr. Stone came into the control room, poised near the hatch, caught her husband's eye and beckoned him to come with her.

He floated after her into their stateroom. "What is it?" he asked. "Is Lowell worse?"

"No, he's better."

"Eh?"

"Dear, I don't think he was spacesick at all."

"What's that?"

"Oh, a little bit, perhaps. But I think his symptoms were largely allergy; I think he is sensitive to the sedative."

"Huh? I never heard of anyone being sensitive to that stuff before."

"Neither have I, but there can always be a first time I withdrew the drug several hours ago since it did not seem to help him. His symptoms eased off gradually and his pulse is better now."

"Is he okay? Is it. safe to go on to Mars?"

"Too early to say. I'd like to keep him under observation another day or two."

"But - Edith, you know that's impossible. I've got to maneu­ver." He was wretched from strain and lack of sleep; neither had slept since blast-off more than twenty-four hours earlier.

"Yes, I know. Give me thirty minutes warning before you must have an answer. I'll decide then."

"Okay. I'm sorry I snapped at you."

"Dear Roger!"

Before they were ready to 'round the corner' on their swing past Earth the child was much better. His mother kept him under a light hypnotic for several hours; when he woke from it he demanded food. She tried letting him have a few mouth­fuls of custard; he choked on the first bite but that was simply mechanical trouble with no gravity - on the second bite he learned how to swallow and kept it down.

He kept several more down and was still insisting that he was starved when she made him stop. Then he demanded to be untied from the couch. His mother gave in on this but sent for Meade to keep him under control and in the bunk-room. She pulled herself forward and found her husband. Hazel and Castor were at the computer; Castor was reading off to her a problem program while she punched the keys; Pollux was taking a doppler reading on Earth. Edith drew Roger Stone away from them and whispered, "Dear, I guess we can relax. He has eaten - and he didn't get sick."

"Are you sure? I wouldn't want to take even a slight chance."

She shrugged. "How can I be sure? I'm a doctor, not a fortune-teller."

"What's your decision?"

She frowned, "I would say to go on to Mars."

"It's just as well." He sighed. "Traffic turned down my alternate flight plan. I was just coming back to tell you."

"Then we have no choice."

"You know better than that. I'd rather tell it to the judge than read the burial service. But I have one more card up my sleeve."

She looked her query; he went on. "The War God is less than ten thousand miles behind us. If necessary, by using our mass margin, in less than a week I could match with her and you and the baby could transfer. She's a "tumbling. pigeon" since they refitted her - anything from Luna-surface to a full gravity."

"I hadn't thought of that. Well, I don't think it will be neces­sary but it's a comfort to know that there is help close by." She frowned. "I would not like to leave you and the children to shift for yourselves - and besides, it's risky to use your margin; you may need it badly when we approach Mars."

"Not if we handle the ship properly. Don't you worry; Hazel and I will get it there if we have to get out and push."

Pollux had stopped what he was doing and had been trying to overhear his parents' conversation. He was unsuccessful; they had had too many years' practice in keeping the kids from hearing. But he could see their intent expressions and the occa­sional frowns; he signaled his twin.

Castor said, "Hold it, Hazel. Time out to scratch. What goes, Pol?"

"'Now is the time for all good men"." He nodded toward their parents.

"Right. I'll do the talking." They moved aft.

Roger Stone looked at them and frowned. "What is it, boys? We're busy."

"Yes, sir. But this seems like a salubrious time to make an announcement."

"Yes?"

"Pol and I vote to go back home.

"Huh?"

"We figure that there's no percentage in taking a chance with Buster."

Pol added, "Sure, he's a brat, but look how much you've got invested in him."

"If he died on us," Castor went on, "it would spoil all the fun."

"And even if he didn't, who wants to clean up after him for weeks on end?"

"Right," agreed Pol. "Nobody likes to play room steward to a sick groundhog."

"And if he did die, the rest of you would blame us for the rest of our lives."

"Longer than that," Pol added.

"Don't worry about that "negat" from Traffic. Hazel and I are working out a skew path that will let us miss the Queen Mary ,with minutes to spare - seconds anyhow. Course it may scare em a little."

" Quiet!" said Captain Stone. "One at a time - Castor, let me get this straight: do I understand that you and your brother are sufficiently concerned about your younger brother's welfare that you want to return to Luna in any case?"

"Yes, sir."

"Even if your mother decides that it is safe for him to continue?"

"Yes, sir. We talked it over. Even if he's looking pretty good now, he was one sick pup and anybody that sick might not make it to Mars. It's a long haul. We don't want to risk it."

Hazel had come aft and listened; now she said, "Nobility ill-becomes you, Cas. You were more convincing with the other routine."

"You butt out of this, Mother. Pol?"

"Cas told you. Shucks, we can make other trips"

Roger Stone looked at his sons. "I must say," he said slowly, "that it is surprising and gratifying to find so much family soli­darity in this aggregation of individualists. Your mother and I will remember it with pride. But I am glad to say that it is unnecessary. We will continue for Mars."

Hazel scowled at him. "Roger, did you bump your head on the take-off? This is no time to take a chance; we take the kid back to Luna. I've talked with the boys and they mean it. So do I."

Castor said, "Dad, if you're afraid of that skew orbit, I'll pilot. I know-"

" Silence!" When he got it he went on as if to himself, "It says right here in the book to give orders, not explanations, and never to let them be argued. So help me, I'm going to run a taut ship if I have to put my own mother in irons." He raised his voice. "All hands! Prepare for maneuvering. Departure for Mars, gravity-well procedure."

Edith Stone said softly to Hazel, "The baby is all right. Mother. I'm sure." Then she turned to her sons. "Castor, Pollux - come here, dears."

"But Dad said -"

"I know. Come here first." She kissed each of them and said, "Now man your stations."

Mead appeared at the hatch, towing Lowell behind her like a toy balloon. He seemed cheerful and his face was cheerfully smeared with chocolate. "What's all the racket about?" she demanded. "You not only woke us; you must be disturbing people three ships behind."

A gravity-well maneuver involves what appears to be a contradiction in the law of conservation of energy. A ship leaving the Moon or a space station for some distant planet can go faster on less fuel by dropping first toward Earth, then performing her principal acceleration while as close to Earth as possible. To be sure, a ship gains kinetic energy (speed) in fall­ing towards Earth, but one would expect that she would lose exactly the same amount of kinetic energy as she coasted away from Earth.

The trick lies in the fact that the reactive mass or 'fuel' is itself mass and as such has potential energy of position when the ship leaves the Moon. The reactive mass used in accelerating near Earth (that is to say, at the bottom of the gravity well) has lost its energy of position by falling down the gravity well. That energy has to go somewhere, and so it does - into the ship, as kinetic energy. The ship ends up going faster for the same force and duration of thrust than she possibly could by departing directly from the Moon or from a space station. The mathematics of this is somewhat baffling - but it works.