Robert Heinlein - The Rolling Stones

"You are captain, son."

He sighed. "I suppose I knew it all along."

"Yes, but you had to struggle with it first." She kissed him. "Orders, son?"

"Let's get to it. It's a good thing we didn't waste any margin in departure."

"That it is."

When Hazel told the others the news Castor asked, "Does Dad want us to compute a ballistic?"

"No."

"A good thing - for we've got to get those bikes inboard, fast! Come on, Pol. Meade, how about suiting up and giving us a hand? Unless Mother needs you?"

"She does," answered Hazel, "to take care of Lowell and keep him out of the way. But you won't be bringing the bikes inboard."

"What? You can't balance the ship for maneuvers with them where they are. Besides, the first blast would probably snap the wires and change your mass factor."

"Cas, where are your brains? Can't you see the situation? We jettison."

"Huh? We throw away our bikes? After dragging almost to Mars?"

"Your bikes, all our books, and everything else we can do without. The rough run-through on the computer made that clear as quartz; it's the only way we can do this maneuver and still be sure of having a safe margin for homing in. Your father is checking over the weight schedule right now."

"But -, Castor's face suddenly relaxed and became impassive. "Aye aye, ma'am."

The twins were suiting up but had not yet gone outside when Pollux was struck by a notion. "Cas? We cut the bikes loose; then what happens?"

"We charge it off to experience - and try to recover from Four-Planets Transit. They won't pay up, of course."

"Use your skull. Where do the bikes end up?"

"Huh? Why, at Mars!"

" Right. Or pretty near. In the orbit we're in now, they swing in mighty close and then head down Sunside again. Suppose, on closest approach, we are standing there waiting to snag 'em?"

"Not a chance. It will take us just as long to get to Mars - and in a different orbit, same as the War God's?

" Yes, but just supposing. You know, I wish I had a spare radar beacon to hang on them. Then if we could reach them, we'd know where they were."

"Well, we haven't got one. Say! Where did you put that used reflecting foil?"

"Huh? Oh, I see. Grandpa, sometimes your senile decay is not quite so noticeable." The Stone had started out, of course, covered on one side of her living quarters by mirror-bright aluminium foil. As she drifted farther and farther from the Sun, reflecting the Sun's heat had grown less necessary, absorbing it more desirable. To reduce the load on the ship's heating and cooling system, square yards of it were peeled up and taken inside to store from week to week.

"Let's ask Dad."

Hazel stopped them at the hatch to the control room. "He's at the computer. What's the complaint?"

"Hazel, the reflecting foil we've been salvaging - is it on the jettison list?"

"Certainly. We'll pick up some more on Mars for the trip back. Why?"

"A radar corner - that's why!" They explained the plan. She nodded. "A long chance, but it makes sense. See here, wire everything we jettison to the bikes. We might get it all back."

"Sure thing!" The twins got busy. While Pollux gathered to­gether the bunches of bicycles, all but a few in good repair and brave with new paint. Castor constructed a curious geometrical toy. With 8-gauge wire, aluminium foil, and sticky tape he made a giant square of foil, edged and held flat with wire. This he bisected at right angles with a second square. The two squares he again bisected at the remaining possible right angle with a third square. The result was eight shiny right-angled corners facing among them in all possible directions - a radar reflector. Each corner would bounce radar waves directly back to source, a principle easily illustrated with a rubber ball and any room or box corner. The final result was to step up the effectiveness or radar from an inverse fourth-power law to an inverse square law - in theory, at least. In practice it would be somewhat less than perfectly efficient but the radar response of the assembly would be increased enormously. A mass so tagged would stand out on a radar screen like a candle in a cave.

This flimsy giant kite Castor anchored to the ball of bicycles and other jetsam with an odd bit of string. No stronger link was necessary; out here no vagrant wind would blow it away, no one would cut it loose. "Pol," he said, "go bang on the port and tell 'em we're ready."

Pollux walked forward and did so, rapping on the quartz first to attract his grandmother's attention, then tapping code to report. While he was gone Castor attached a piece of paper reading:

NOT FOR SALVAGE

This cargo is in free transit by intention. The undersigned owner intends to recover it and warns all parties not to claim it as abandoned. U.P. Rev. Stat. # 193401

Roger Stone, Master

P.Y. Rolling Stone, Luna

When Pollux came back he said, "Hazel says go ahead but take it easy."

"Of course." Castor untwisted the single wire that held the ungainly mass to the ship, then stood back and watched it. It did not move. He reached out and gave it the gentlest shove with his little finger, then continued watching. Slowly, slowly it separated from the ship. He wished to disturb its orbit as little as possible, to make it easy to find. The petty vector he had placed on it - an inch a minute was his guess - would act for all the days from there to Mars; he wanted the final sum to remain small.

Pollux twisted around and picked out the winking gleam of the War God. " Will the jet be clear of it when we swing ship?" he asked anxiously.

"Quit worrying. I already figured that."

The maneuver to he performed was of the simplest - point to point in space in a region which could be treated as free of gravity strain since the two ships were practically the same distance from the Sun and Mars was too far away to matter. There were four simple steps: cancellation of the slight vector difference between the two ships (the relative speed with which the War God was puffing away), acceleration toward the War God, transit of the space between them, deceleration to match orbits and lie dead in space relative to each other on arrival.

Steps one and two would be combined by vector addition; step three was simply waiting time. The operation would be two maneuvers, two blasts on the jet.

But step three, the time it would take to reach the War God, could be enormously cut down by lavish use of reactive mass. Had time been no object they could have, as Hazel put it, closed the gap 'by throwing rocks off the stern." There was an infinite number of choices, each requiring different amounts of reactive mass. One choice would have saved the bicycles and their per­sonal possessions - but it would have stretched the transit time out to over two weeks.

This was a doctor's emergency call - Roger Stone elected to jettison.

But he did not tell the twins this and he did not require them to work a ballistic. He did not care to let them know of the choice between sacrificing their capital or letting strangers wait for medical attention. After all, he reflected, the twins were pretty young.

Eleven hours from blast time the Stone hung in space close by the War God. The ships were still plunging toward Mars at some sixteen miles per second; relative to each other they were stationary - except that the liner continued her stately rotation, end over end. Dr. Stone, her small figure encumbered not only with space suit, pressure bottles, radio, suit jet, and life lines, but also with a Santa Claus pack of surgical supplies, stood with her husband on the side of the Stone nearest the liner. Not knowing exactly what she might need she had taken all that she believed could be spared from the stock of their own craft -drugs, antibiotics, instruments, supplies.