"Sure. Why not? Except my assistant, maybe. I believe he wants off at the next stop."

Pollux growled. "I'm feeling okay. Quit riding me."

Roger Stone said, "Edith could use your help, Mother. Buster has thrown up all over the bunkroom."

"Why, the little devil! He didn't have a thing to eat today; I rode herd on him myself."

"You must have let him out of your sight for a few minutes, from the evidence. Better go give Edith a hand."

"To hear is to obey, Master." She kicked one heel against the bulkhead behind her and zipped out the hatch. Roger turned to his son.

"How's it going?"

"I'll be all right in a couple of hours. It's just one of those things you have to go through with, like brushing your teeth."

"Check. I'd like to rent a small planet myself. Have you written up the engineering log?"

"Not yet."

"Do so. It will take your mind off your stomach." Roger Stone went forward again and looked into the bunkroom. Lowell was awake and crying; Edith had him sheeted to a bunk to give him a feeling of pressure and stability.

The child wailed, "Mama! Make it hold still"

" Shush, dear. You're all right. Mother is here,"

"I want to go home!"

She did not answer but caressed his forehead. Roger Stone backed hastily out and pulled himself forward.

By supper time all hands except Lowell were over the effects of free fall - a sensation exactly like stepping off into an open elevator shaft in the dark. Nevertheless no one wanted much to eat; Dr. Stone limited the menu to a clear soup, crackers, and stewed dried apricots. Ice cream was available but there were no takers.

Except for the baby none of them had any reason to expect more than minor and temporary discomfort from the change from planet-surface weight to the endless falling of free orbit. Their stomachs and the semicircular canals of their ears had been through the ordeal before; they were inured to it, salted.

Lowell was not used to it; his physical being rebelled against it, nor was he old enough to meet it calmly and without fear. He cried and made himself worse, alternating that with gagging and choking. Hazel and Meade took turns trying to quiet him. Meade finished her skimpy dinner and relieved the watch; when Hazel came into the control room where they were eating Roger Stone said, "How is he now?"

Hazel shrugged. "I tried to get him to play chess with me. He spat in my face."

"He must be getting better."

"Not so you could notice it."

Castor said, "Gee whiz, Mother, can't you dope him up till he gets his balance?"

"No," answered Dr. Stone, "I'm giving him the highest dosage now that his body mass will tolerate."

"How long do you think it will take him to snap out of it?" asked her husband.

"I can't make a prediction. Ordinarily children adapt more readily than adults, as you know, dear - but we know also that some people never do adapt. They simply are constitutionally unable to go out into space."

Pollux let his jaw sag. "You mean Buster is a natural-born groundhog?" He made the word sound like both a crippling disability and a disgrace.

"Pipe down," his father said sharply.

"I mean nothing of the sort," his mother said crisply. "Lowell is having a bad time but he may adjust very soon."

There was glum silence for some minutes. Pollux refilled his soup bag, got himself some crackers, and eased back to his perch with one leg hooked around a stanchion. He glanced at Castor; the two engaged in a conversation that consisted entirely of facial expressions and shrugs. Their father looked at them and looked away; the twins often talked to each other that way; the code - if it was a code - could not be read by anyone else. He turned to his wife. "Edith, do you honestly think there is a chance that Lowell may not adjust?"

"A chance, of course." She did not elaborate, nor did she need to. Spacesickness like seasickness does not itself kill, but starva­tion and exhaustion do.

Castor whistled. "A fine time to find it out, after it's too late. We're akeady in orbit for Mars."

Hazel said sharply. "You know better than that, Castor."

"Huh?"

"Of course, dopy," his twin answered. "We'll have to tack back.' :1

"Oh." Castor frowned. "I forgot for the moment that this was a two-legged jump." He sighed. "Well, that's that. I guess we go back." There was one point and one only at which they could decide to return to the Moon. They were falling now toward Earth in a conventional 'S-orbit" practically a straight line. They would pass very close to Earth in an hyperboloid at better than five miles per second, Earth relative. To continue to Mars they planned to increase this speed by firing the jet at the point of closest approach, falling thereby into an ellipsoid, relative to the Sun, which would let them fall to a rendezvous with Mars. They could reverse this maneuver, check their plunging progress by firing the jet against their motion and thereby force the Stone into an ellipsoid relative to Earth, a curve which, if correctly calculated, would take them back to Luna, back home before their baby brother could starve or wear himself out with retching. "Yep, that's that," agreed Pollux. He suddenly grinned. "Anybody want to buy a load of bicycles? Cheap?"

"Don't be in too big a hurry to liquidate," his father told him, "but we appreciate your attitude. Edith, what do you think?"

"I say we mustn't take any chances," announced Hazel. "That baby is sick."

Dr. Stone hesitated: "Roger, how long is it to perigee?"

He glanced at his control board. "About thirty-five hours."

"Why don't you prepare both maneuvers? Then we will not have to decide until it's time to turn ship."

"That makes sense, Hazel, you and Castor work the homing problem; Pol and I will work the Mars vector. First approxi­mations only; we'll correct when we're closer. Everyone work independently, then we'll swap and check. Mind your deci­mals!"

"You mind yours." Hazel answered.

Castor gave his father a sly grin. "You picked the easy one, eh, Dad?"

His father looked at him. "Is it too hard for you? Do you want to swap?"

"Oh, no, Sir! I can do it."

"Then get on with it - and bear in mind you are a crew member in space."

"Aye aye, sir."

He had in fact 'picked the easy one'; the basic tack-around-Earth-for-Mars problem had been solved by the big computers of Luna Pilot Station before they blasted off. To be sure, Luna Pilot's answer would have to be revised to fit the inevitable errors, or deviations from flight plan, that would show up when they reached perigee rounding Earth - they might be too high, too low, too fast, too slow, or headed somewhat differently from the theoretical curve which had bem computed for them. In fact they could be sure to be wrong in all three factors; the tiniest of errors at blast-off had a quarter of a million miles in which to multiply.

But nothing could be done to compute the corrections for those errors for the next fifteen or twenty hours; the deviations had to be allowed to grow before they could be measured accurately.

But the blast back to shape an ellipsoid home to Luna was a brand-new, unpremeditated problem. Captain Stone had not refused it out of laziness; he intended to do both problems but had kept his intention to himself. In the meantime he had another worry; strung out behind him were several more ships, all headed for Mars. For the next several days there would be frequent departures from the Moon, all ships taking advantage of the one favorable period in every twenty-six months when the passage to Mars was relatively 'cheap', i.e., when the minimum-fuel ellipse tangent to both planet's orbits would actually make rendezvous with Mars rather than arrive foolishly at some totally untenanted part of Mars' orbit. Except for military vessels and super expensive passenger-ships, all traffic for Mars left at this one time.