“Unknown, sir. The flare could burst out any time within the next twenty-four hours.”

“The radiation could increase to killing levels within a few hours afterward,” the other astronaut said.

It was annoying to be talking to the backs of two helmets. Greg still could not tell from the voices in his earphones which astronaut was speaking.

“Can’t we get to Moonbase before the flare erupts?” he asked.

“Standard safety procedure is to return to the orbital station we started from.”

“The space stations orbit below the geomagnetosphere,” said the other voice.

“What’s that got to do with it?” Greg demanded.

“The geomagnetosphere is like a magnetic umbrella, sir. It offers protection from the heaviest levels of radiation.”

“Still, all personnel on each station have to evacuate to the ECPM during the peak radiation influx.”

Before Greg could ask, the other astronaut explained, “Emergency Crew Protection Module, that is.”

“I see,” said Greg. “But if the flare is still a day or so away, why can’t we go on to Moonbase?”

“There’s no telling when the flare will burst out”

“Could be in another few minutes.”

“But even so,” Greg insisted, “you said it would be several hours after that before the radiation levels got dangerous.”

They hesitated before one of them answered, “That’s true, but standard procedure—”

“Can’t we juice this vehicle and get to Moonbase sooner?”

Again they hesitated. Then, “We’d have to re-light the main engine.”

“But that would actually cost us less delta-vee than reversing back to LEO.”

Greg tried to sort out their jargon. “You’re saying that it would be easier to speed up and get to Moonbase?”

“Yessir.”

“But we’d have to file a new flight plan and get it approved by traffic control.”

“And undergo another three or four gees of thrust for a few minutes.”

The takeoff from Earth had been slightly less than three gees for several minutes, Greg recalled.

“I can crunch the numbers and then check ’em out with ground control.”

“Do that,” Greg commanded.

For several minutes the two astronauts hunched their helmeted heads together, fingers flicking over the keyboards in their control panel. Greg realized they were talking to ground control, back at Savannah. He tapped the channel selector on the wrist of his suit until he found their frequency. Listening in on their chatter was pretty much a waste of time, though: Greg could barely understand half of their technospeak.

But at last he heard, Trajectory alterations are approved. You are cleared for high-thrust bum to Moonbase.”

“Cleared for Moonbase. Roger,” said the pilot.

Greg heard the radio link click off. Then, “Yahoo!” yelled one of them, loud enough to make Greg’s ears ring.

“Light ’er up and move ’er out!”

As a heavy hand of acceleration pressed Greg back in his seat, he realized that the astronauts were more than happy with his insistence on pushing ahead to the Moon.

Killifer’s main assignment was to remain inside the headquarters shelter of the expedition’s base camp and monitor all surface activities. Thus the communications center was his principal station.

He had quite deliberately erased Moonbase’s warning message from the comm system’s computer memory. He waited calmly underground until Brennart came in. Then Killifer hurried to the airlock, where Brennart was carefully removing his suit and vacuuming the dust from it.

Sitting on the slim-legged bench next to Brennart, he spoke just loudly enough to be heard over the buzz of the hand vacuum.

“We got a warning of an imminent solar flare.”

“When?”

“About two hours ago. I didn’t say anything about it; didn’t want to shake up the team.”

Brennart looked down at him, his brows knit in thought. They made an odd pair: the tall, golden-haired leader and his dark, lantern-jawed aide.

“I might have exceeded my authority,” Killifer confessed. “I erased the warning from the log.”

“Why?”

“I didn’t want anyone but you to know about it. You’re the expedition commander. You should be the one who makes the decision on what to do. If the comm tech or Doug Stavenger or somebody else found out about the warning, they’d be blabbing it to everybody and nobody’d want to be outside.”

Brennart nodded slowly. “That’s true enough.”

“I hope I did the right thing,” Killifer said, with as much humility as he could muster.

“Yes, you did. A warning of an imminent flare poses no immediate danger and we still have a lot of digging to do out there.”

“The connectors?”

With a shake of his head, Brennart said, “We’re behind schedule, I know. You don’t have to remind me. The ground out there is all rock. Hardly any regolith over it at all.”

Without the tunnels to connect them, the expedition members would be stuck in the four separate buried shelters when the flare’s radiation reached them.

“What do you plan to do, then?” Killifer asked.

Frowning, Brennart said, I’d better put everybody into the digging. We don’t even have enough rubble to adequately shield the four shelters yet, let alone the connecting tunnels.”

For the first time, Killifer felt alarmed. But he hid it and said merely. “You always know what’s best.”

It was dark out on the surface, menacingly, cryogenically dark with the high mountains blocking out any chance of light or warmth. Yet Doug found it thrilling. More than thrilling; it was the most exciting thing he had ever known. To put your bootprints down where no human being has ever stood before. To see what no human eyes have ever gazed on. Danger and wonder and the lure of the unknown, all mixed together. That’s what the frontier is all about Doug told himself. God, it must be habit-forming, like a drug.

He took a deep breath of canned air, realizing with a grin that it was an artificial mixture of oxygen and nitrogen at unnaturally low pressure. Every breath we take, every step we make, all depends on the machines we’ve developed.

So what? he asked himself. How long do you think humans would’ve survived on Earth if they hadn’t developed fire and tools? We’re machine makers, and with our machines we can expand throughout the universe.

Then he chuckled to himself. Throughout the universe, huh? Maybe you ought to just concentrate on this little base camp you’re building here at the south pole of the Moon. Get that done before you start challenging the rest of creation.

Starlight guided his steps across the rocky ground. The hard unblinking stars were strewn across the black sky like dust; even through his heavily tinted visor Doug could see thousands of them staring back at him. They lit the ground like pale moonlight on Earth.

He walked to the edge of the ice field. Staring at its dark flat expanse, Doug felt disappointed that the dust-covered ice did not reflect the stars. It looked almost like a dead calm sea, flat and still and gleaming slightly, as if lit from within. Then he looked up as high as he could from inside his helmet and realized that he could not see the Earth. From Moonbase the Earth was always hanging overhead, warm, beckoning, friendly. The sky down here was empty, lonely.

Turning, he saw Mt. Wasser, its flat-topped curving peak bathed in glowing sunlight, shining against the darkness like a disembodied beacon. Tomorrow we start up the mountain, Doug told himself. With the nanomachines. With any luck, we’ll be building the power tower within thirty-six hours.

We’re making history here! The thought exhilarated him. Kids will read about this expedition in their schoolbooks.

He looked out at the ice field again and suddenly, without even deciding consciously to do it, he ran to the edge of the softly gleaming ice with long, loping lunar strides; almost like flying. Then he felt his boots on the ice and he glided along like a skater, spinning and turning, laughing inside his helmet like a boy at play.