The territory above these three floors was forbidden to passengers. Going upward, the remaining levels were Life Support, Crew Quarters, and-forming a kind of penthouse with all-round visibility-the Bridge. In the other direction, the four levels were Galley, Hold, Fuel, and Propulsion. It was a logical arrangement, but it would take Duncan some time to discover that the Purser’s Office was on the kitchen level, the surgery next to the freight compartment, the gym in Life Support, and the library tucked away in an emergency airlock overlapping levels Six and Seven…. During the circumnavigation of his

new home, Duncan encountered a dozen other passengers on a 61 similar voyage of exploration, and exchanged the guarded greetings appropriate among strangers who will soon get to know each other perhaps all too well. He had already been through the passenger list to see if there was anyone on board he knew and had found a few familiar Titanian names, but no close acquaintances. Sharing cabin L.3, he had discovered, was a Dr. Louise

Chung; but the parting with Marissa still hurt too much for the “Louise” to arouse more than the faintest flicker of interest.

I In any event, as he found when he returned to L.3, Dr. Chung was a bright little old lady, undoubtedly on the far side of a hundred, who greeted him with an absent-minded courtesy which, even by the end of the voyage, never seemed to extend to a complete recognition of his existence. She was, he soon discovered, one of the Solar System’s leading mathematical physicists, and the authority on resonance phenomena among the satellites of the outer planets. For half a century she had been trying to explain why the gaps in

Saturn’s rings were not exactly where all the best theories demanded.

The two hours ticked slowly away, finally seeming to move with a rush toward the expected announcement: “This is Captain Ivanov speaking at minus five minutes. All crew members should be on station or standby, all passengers should have safety straps secured. Initial acceleration will be one hundredth gravity-ten centimeters second squared. I repeat, one hundredth gravity. This will be maintained for ten minutes while the propulsion system undergoes routine checks.”

And suppose it doesn’t pass those checks? Duncan asked himself. Do even the mathematicians know what would happen if the Asymptotic Drive started to malfunction? This line of thought was not very profitable, and he hastily abandoned it.

“Minus four minutes. Stewards check all passengers secured.”

Now that instruction could not possibly be obeyed. There were three hundred twenty-five passengers, half of them in their cabins and the

other half in the two lounges, and there was no way in which the dozen harassed stewards could see that all their charges were behaving. They had made one round of the ship at minus thirty and minus ten minutes, and passeligers who had cut loose since then had only themselves to blame. And anyone who could be hurt by a hundredth of a gee, thought Duncan, certainly deserved it. Impacts at that acceleration had about the punch of a large wet sponge.

“Minus three minutes. All systems normal. Passengers in Lounge B will see

Saturn rising.”

Duncan permitted himself a slight glow of self satisfaction. This was precisely why, after checking with one of the stewards, he was now in Lounge B. As Titan always kept the same face turned toward its pr tary the spectacle of the great globe climbing abe the horizon was one that could never be seen from the surface, even if the almost perpetual over cast of hydrocarbon clouds had permitted.

That blanket of clouds now lay a thousand kilometers below, hiding the world that it protected from the chill of space. And then suddenly-unexpectedly, even though he had been waiting for it-Saturn. was rising like a golden ghost.

In all the known universe, there was nothing to compare with the wonder he was seeing now. A hundred times the size of the puny Moon that floated in the skies of Earth, the flattened yellow globe looked like an object lesson in planetary meteorology. Its knotted bands of cloud could change their appearance almost every hour, while thousands of kilometers down in the hydrogen-methane atmosphere, eruptions whose cause was still unknown would lift bubbles larger than terrestrial continents up from the hidden core.

They would expand and burst as they reached the limits of the atmosphere, and in minutes Saturn’s furious ten-hour spin would have smeared them out into long colored ribbons, stretching halfway round the planet.

Somewhere down there in that inferno, Duncan reminded himself with awe,

Captain Kleinman had died seventy years ago, and so had part of Grandma

Ellen. In all that time, no one had attempted to return. Saturn still

represented one of the largest pieces of unfinished business in the Solar System-next, perhaps, to the smoldering hell of Venus.

The rings themselves were still so inconspicuous that it was easy to overlook them. By a cosmic irony, all the inner satellites lay in almost the same plane as the delicate, wafer-thin structure that made Saturn unique. Edge on, as they were now, the rings were visible only as hairlines of light jutting out on either side of the planet, yet they threw a broad, dusky band of shadow along the equator.

In a few hours, as Sirius rose above the orbital plane of Titan, the rings would open up in their full glory. And that alone, thought Duncan, would be enough to justify this voyage.

“Minus one minute…”

He had never even heard the two-minute mark; the great world rising out of the horizon clouds must have held him hypnotized. In sixty seconds, the automatic sequencer in the heart of the drive unit would’ initiate its final mysteries. Forces which only a handful of living men could envisage, and none could truly understand, would awaken in their fury, tear Sirius from the grip of Saturn, and hurl her sunward toward the distant goal of

Earth. “.. . ten seconds… five seconds … ignition!”

How strange that a word that had been technologically obsolete for at least two hundred years should have survived in the jargon of astronautics!

Duncan barely had time to formulate this thought when he felt the onset of thrust. From exactly zero his weight leaped up to less than a kilogram. It was barely enough to dent the cushion above which he had been floating, and was detectable chiefly by the slackening tension of his waist belt.

Other effects were scarcely more dramatic. There was a distinct change in the timbre of the indefinable noises which never cease on board a spacecraft while its mechanical hearts are operating; and it seemed to

Duncan that, far away, he could hear a faint hissing. But he was not even sure of that.

And then, a thousand kilometers below, he saw the unmistakable evidence that Sirius was indeed breaking away from her orbit. The ship had been

driving 64 into night on its final circuit of Titan, and the wan sunlight had been swiftly fading on the sea of clouds far below. But now a second dawn had come, in a wide swathe across the face of the world he was soon to leave.

For a hundred kilometers behind the accelerating ship, a column of incandescent plasma was splashing untold quintillions of candlepower out into space and across the carmine cloud scape of Titan. Sirius was falling sunward in greater glory than the sun itself.

“Ten minutes after ignition. All drive checks complete. We will now be increasing thrust to our cruise level of point two gravities-two hundred centimeters second squared.”

And now, for the first time, Sirius was showing what she could do. In a smooth surge of power, thrust and weight climbed twenty-fold and held steady. The light on the clouds below was now so strong that it hurt the eye. Duncan even glanced at the still-rising disc of Saturn to see if it too showed any sign of this fierce new sun. He could now hear, faint but unmistakable, the steady whistling roar that would be the background to all life aboard the ship until the voyage ended. It must, he thought, be pure coincidence that the awesome voice of the Asymptotic Drive sounded so much like that of the old chemical rockets that first gave men the freedom of space. The plasma hurtling from the ship’s reactor was moving a thousand times more swiftly than the exhaust gases of any rocket, even a nuclear one; and how it created that apparently familiar noise was a puzzle that would not be solved by any naive mechanical intuition.