“Pea-shooter,” he explained. “I am young at heart.” He aimed the tube directly up and squeezed the bulb sharply.

Ivo saw the streak as the shot went up. Then he was launched into space, somersaulting uncontrollably. The giant torus of the station careened about him, a faceless mouth, the monster bands of its segment-junctures reminding him of the vertical cracks in parched, pursed lips.

A hand caught his foot and steadied him. “You didn’t listen,” Brad said reprovingly, straight-faced within the bubble-helmet. “I told you to watch your balance.” His voice seemed to come from the depths, now conducted only via the physical contact between them.

“I didn’t listen,” Ivo agreed ruefully. He looked about and found that they were flying toward the center of the station: the fifty-foot metallic ball guyed by nylon wires extending to the inner rim of the torus. He and Brad were still rotating slowly, some of his motion having been imparted to his friend, but in free-fall this was inconvenient rather than distressing. He had to keep adjusting in order to keep his gaze on the destination.

“Don’t tell me, let me guess,” Ivo said when it was clear that Brad was not going to explain. “You popped a — a bubble, and the atmospheric pressure squirted us out. Since your airgun-spacelock is aimed at the center—”

“I see you have recovered a wit or two. Actually, I was showing off a little; that isn’t exactly the approved technique. Wastes gas and is dangerous for the inexperienced, to name a couple of objections. We’re supposed to wait for the catapult. Nobody does, of course. Even so, you’re wrong about the aim. The tube is tilted to compensate for angular momentum; otherwise we’d miss the target every time because of the spin of the torus. Apart from all that, your guess was fair.”

“Uh-huh.”

“Now watch your footing as we land.” Brad removed his hand, nudging the foot just enough to counter the remaining spin and send Ivo slightly ahead, and he fell upright toward the dark surface of the artificial planetoid.

He saw now that the guys were actually light chains. They merely anchored the mass in place, so that arrivals and departures such as theirs did not jog it out of alignment. Each hooked to a traveling roller magnetically attached, so that the rotation of the doughnut imparted no spin to the ball.

“This is the macroscope proper?” he inquired before remembering that his voice would not carry through the vacuum, now that contact was gone. Obviously it was the ’scope, painstakingly isolated from unwanted motions and intrusions. He had no doubt that their approach was being observed, or that it had been cleared well in advance.

The macroscope was the most expensive, important device ever put into space by man. The project had been financed and staffed internationally as research in the public interest: meaning that while no single government had cared to expend such considerable resources on such a farfetched speculation, none could afford to leave the potential benefits entirely to others.

Compromise had accomplished mighty things. The macroscope was functioning, and each participant was entitled to a share of its use proportionate to the investment, and a similar weighted share of all information obtained. That was most of what Ivo knew about it; exactly what hours fell to whom was classified information. Much of the result was general: details of astronomic research that had the astronomers gaping. The scope, it seemed, ground out exceeding fine pictures. Much was concealed from the common man, but the awe this instrument nevertheless inspired was universal.

He thought of it as basically nothing more than a gigantic nose, sniffing out the secrets of the galaxy. It still daunted him.

He landed at last, almost afraid his momentum would jar the machine out of line. Brad came down behind him, controlling his spin to land neatly on his feet. Ivo decided he would have to master that technique; his own touchdown had been awkward.

Brad took his hand so that they could communicate readily. “We’ll have to wait for admittance. Could be several minutes if he’s in a taping sequence. Just relax and admire the scenery.”

Ivo did. He peeked cautiously toward the sunside, knowing that Sol was much fiercer here in space than to an observer sheathed in Earth’s atmosphere.

A monster rocket floated there, similar to one he remembered.

“What’s a Saturn VI doing here? A complete one, I mean. I thought the booster-stage never got out of orbit.”

“Correct. This one’s in orbit.”

“Earth orbit, mister innocent. This is sun orbit, if I’m not totally confused.”

“Oh, it can travel far — if refueled. That’s Joseph, our emergency vehicle. Enough power there to blast us all to safety in a hurry — if ever necessary. Personally, I’d call space safer than tempestuous, seam-splitting Earth. Joseph is actually the tug that nudged the scope into this orbit. Now he’s semiretired; no point in sending the old gent home empty.”

“Must be quite a lot of oomph when you click your flint under his tail. No gravity—” The thrust, he knew, would not change; but here none of it would he counteracted by planetary drag, so the net effect had to be a much larger payload or higher velocity.

“To be sure. We’ve been tinkering with him on the QT. He still uses hydrogen as the working fluid, but stores it solid. But no ignition — combustion in a chemical engine is only a means, not an end. It is the velocity of the expelled propellant that counts, you know, rather than the per se heat of the engine, although—”

“Sorry, Brad. I don’t know. If you must get technical—”

“I can make it simple for you, Ivo. I just can’t resist bragging a little, because I was the lucky lad who happened to pick the key out of the scope.”

“You’re actually getting technology from—”

Brad moved a finger in their old-time code for caution. That implied that the question had awkward aspects that could only be cleared up more privately, which in turn implied that their present conversation might be overheard somehow. Perhaps through a pickup in the macroscope housing. And the implications of that—

Ivo shut up. Cloak and dagger did not thrill him; it brought back the restlessness in his stomach. Too much had happened in the past few hours.

“We’ve had the basic theory to adapt a gaseous-core atomic reaction to propulsion for years, but the thing is fraught with peril. We can mix the working fluid — that’s the hydrogen we belch from the tail of the rocket to make it go — directly with the fissioning uranium in the chamber. That raises the gas to a temperature that makes possible a specific impulse ten times the best we can do with chemical combustion. But it’s too hot. It melts any containing material we know of. What I discovered was a heat-shielding technique that — well, Joseph may look ordinary to you, but he’s a Saturn VI in outline only. His engine produces a thrust you’d call over ten gravities — and he can keep it up for almost a week before he runs out of hydrogen. He never runs out of heat, of course. If you could only appreciate by what factor that outperforms the best Earth has known before—”

“Brad, I am appreciating with fervent fervor. But I’m still a layman. I never had technical training. I’ll be happy to take your word it can do the job, whatever the job is.”

Speech lapsed. Ivo knew that Brad’s feelings were not hurt. They had merely taken the dialogue beyond the danger point — its relevance to the macroscope? — so that it was safe to drop it.

His attention had been on immediate things hitherto, but now he stared beyond the rim of the station, away from the uncomfortably brilliant sun, and saw the stars. He found to his surprise that they were familiar.

Ursa Major — the Big Dipper — was evident, with its dip pointing to Ursa Minor. And just who was Ursa? he always asked himself. That was no lady, that was the wife of a bear! he always replied. Draco the Dragon curled around the Little Dipper. Following the line the Big Dipper pointed on past the Pole star, he could travel at multiple-lightspeed all the way to Aquarius, perpetually chasing Capricornus. The runner was so close, but fated never to catch up. Somehow that saddened Ivo; there seemed to be a special, personal tragedy in it, though he could not determine why he felt that way.