The Apollo missions to the Moon in the mid-twentieth century were timed to avoid periods when the Sun was likely to erupt with a flare that would drench the solar system with killing levels of hard radiation.

Later, spacecraft shuttling between the Earth and the Moon simply scurried for shelter when a solar storm struck. They either returned to the protection that the Earth’s magnetic field provides against the storm’s lashing hail of protons and electrons, or they landed on the Moon and their crews sought shelter underground. The earliest spacecraft to carry humans beyond the Earth-Moon system had no such options available to them, for their transit times to Mars were so long that they would inevitably encounter a solar storm while weeks or months away from a safe haven. Thus they were outfitted with storm shelters, special compartments in which the crew could be protected from the intense radiation spewed out by a solar flare. The first explorers sent to Mars spent days on end cooped up in their spacecraft’s cramped “storm cellar,” until the high-energy particles of the storm’s plasma cloud finally passed them by.

Starpower 1 had no storm cellar. The entire crew module was protected in the same manner that a storm shelter would have been. The module was lined with thin wires of an exotic yttrium-based compound that formed a superconducting magnet which generated a permanent magnetic field around the crew module, a miniature version of the Earth’s magnetic field. Yet the superconductor could not produce a magnetic field strong enough to deflect the solar storm’s most dangerous killers, the high-energy protons.

When faced with a vast cloud of deadly subatomic particles blasted out by a solar flare, the ship was charged to a high positive electrostatic potential by a pair of electron guns. The energetic protons in the cloud were repelled by the ship’s positive charge. The magnetic field was strong enough to deflect the cloud’s lighter, less energetic electrons — and thus keep the negatively-charged electrons from ruining the ship’s positive charge.

Safely cocooned inside the protective magnetic field, the crew of Starpower 1 watched the swift approach of the storm’s plasma cloud. “Be here in another six hours,” Pancho announced, pulling off her headset as she swiveled the command pilot’s chair to face Dan.

He frowned at the news. “That’s for certain?”

“Certain as they can be. Early-warning spacecraft in Mercury co-orbit have plotted out the cloud. Unless there’s a great big kink in the interplanetary field, it’s gonna roll right over us.”

Nodding, Dan said, “The electron guns are ready to go.”

“Better start ’em up,” she said. “No sense waitin’ till the last minute.”

“Right.” Dan stepped through the hatch, into the empty wardroom, and headed aft, where the electron guns were housed. Pancho could control them from the bridge, but Dan wanted to be there in case any problems cropped up. “And send Amanda up here, will you?” Pancho called to him. “I gotta take a break.”

“Right,” Dan shouted back, over his shoulder.

Where is Amanda? He asked himself. The wardroom was empty. The doors to the privacy compartments along the passageway were closed. And where is Fuchs? he wondered, starting to feel nettled.

He found them both in the sensor bay, where Fuchs was explaining something about the x-ray projector.

“It would be more helpful if we could use a small nuclear device,” the planetary astronomer was saying, totally serious. “That would be the most convenient way of generating x-rays and gamma rays all at the same time. But of course, nuclear devices are banned.”

“Of course,” Amanda said, looking just as intent as Fuchs.

“Pancho needs you on the bridge, Mandy.” Dan said.

She looked startled for a flash of a second, then said, “Right.” As she hurried toward the bridge, Dan asked Fuchs, “What in the name of the nine gods of Sumatra do you want a nuke for?”

“I don’t!” Fuchs said. “They’re illegal, and justly so.”

“But you just said—”

“I was explaining to Amanda about x-ray spectroscopy. How we use xrays to make an asteroid fluoresce and reveal its chemical composition. The x-rays from this solar flare would have been very helpful to us if we were only close enough to the Belt.”

“But a nuke?”

Fuchs spread his hands. “Merely an example of how to produce x-rays and gamma rays on demand. An example only. I have no intention of bringing nuclear explosives into space.”

“I don’t know,” Dan said, scratching his chin. “You might be onto something. Maybe we could talk the IAA into letting us use nukes as sources for spectroscopic studies.”

Fuchs looked aghast. Dan laughed and slapped him on the shoulder. Fuchs saw the joke and grinned weakly back.

Dan’s mood darkened as he edged down the narrow walkway in the aft end of the module. He did not like the thought of being exposed to hard radiation. He had taken a lifetime’s worth of radiation back in his earlier days, working in space. Much more of a dose would kill him, he knew. It wouldn’t be an easy way to go, either.

As he lifted the covers protecting the electron guns’ innards and checked them for the eleventh time since they’d launched out of lunar orbit, Dan thought, Maybe Stavenger’s right. Get a jolt of nanomachines, let them clean up the damage the radiation’s done, rebuild me from the inside. So I won’t be able to go back to Earth. So what? What’s down there that I’d miss so much? He knew the answer even as he asked the question. Sea breezes. Blue skies and soft sunsets. Birds flying. Flowers. Huge ugly brutal cities teeming with life. Vineyards! Dan suddenly realized that no one had yet tried to grow wine grapes off-Earth. Maybe that’s what I’ll do when I retire: settle down and watch my vineyards grow.

The intercom speaker set into the narrow walkway’s overhead carried Pancho’s voice. “Dan, you ready for me to light up the guns?”

The electron guns were just as good as they’d been all the other times he’d inspected them. Closing the cover on the one on his right, Dan answered, “You may fire when ready, Gridley.”

Pancho retorted, “I don’t know who this Gridley guy is, but I can’t rev up the guns till you close both their covers and seal ’em right and proper.”

“Aye, aye, skipper,” Dan said.

By the time he made it back to the bridge, Pancho was nowhere in sight. Amanda sat alone in the right-hand seat, and the bridge was rocking to the beat of highintensity pop music. As soon as she saw Dan come through the hatch, Amanda snapped the music off.

“Pancho’s in the loo,” she said as Dan slid into the command-pilot’s seat.

“How’s the storm?”

“Precisely on track.” Amanda tapped at one of her touchscreens; it displayed a simplified map of the inner solar system, the orbits of Earth and Mars shown as thin lines of blue and red, respectively; the position of Starpower 1 was a blinking bright yellow dot. A lopsided gray miasma was almost touching the dot. Dan’s mouth went dry. “I hate these things,” he mumbled.

“It missed the Earth completely. Mars, as well.”

“But it’s going to swamp us.”

“Actually,” Amanda said, “we’ll merely be brushed by it. A few hours, that’s all.”

“That’s good.”

“Our own velocity is helping a lot, you know. An ordinary spacecraft, coasting along the way they do, would be in the cloud for days on end.” Dan had no desire to be in the cloud for even ten minutes. He changed the subject, as much to get away from the fear building up inside him as any other reason. “How friendly are you and Fuchs?”

Amanda’s brows shot up. “Lars? He’s very earnest — about his work. Nothing more.”

“That’s all there is to it?”

“Yes.”

Dan thought it over. Two healthy young people locked in this sardine can for a couple of weeks. Of course, there’s Pancho and me to chaperon them. Dan grinned to himself. Damn, it’s like being a teenager’s father.