those damned windmills.”
“It’s all ballast, save it for when we need the lift.”
The hours of the night wore on. They traded shifts at the helm, and Nadia caught an uneasy hour’s sleep. When she returned to the cockpit, she saw that the black bulk of Tharsis had rolled over the horizon ahead of them: the two northernmost of the three prince volcanoes, Ascraeus Mons and Pavonis Mons, were visible as humps of occluded stars, out at the edge of the world. To their left Olympus Mons still bulked well above the horizon, and taken with the other two volcanoes, it looked as if they flew low in some truly gigantic canyon. The radar screen reproduced the view in miniature, in green lines on the screen’s gridwork.
Then, in the hour before dawn, it seemed as though another massive volcano were rising behind them. The whole southern horizon was lifting, low stars disappearing as they watched, Orion drowned in black. The storm was coming.
It caught them just at daybreak, choking off the red in the eastern sky, rolling over them, returning the world to rusty darkness. The wind picked up until it swept them along in a muted roar from the land below. The view out the windows was of a few meters of swirling yellow dust, like a close-up of the clouds of Jupiter. Eddies twisted the dirigible’s frame and the gondola trembled and bounced.
They were lucky north was the direction they wanted to go. At one point Arkady said, “The wind should hopefully wrap around the north shoulder of Tharsis.”
Nadia nodded silently. They hadn’t gotten the chance to recharge the batteries after the night’s flight, and without sunlight the motors wouldn’t run too much longer. “Hiroko told me sunlight on the ground during a storm is supposed to be about fifteen percent of normal,” she said. “Higher there should be more. So we’ll get some recharge, but it’ll be slow. Could be that over the course of the day we might get enough to use the props a bit tonight.” She flicked on a computer to do the calculations. Something in the expression on Arkady’s face—not fear, not even anxiety, but a curious little smile—made her aware of how much danger they were in. If they couldn’t use the props, they wouldn’t be able to direct their movement, and they might not even be able to stay aloft. They could descend, it was true, and try to anchor, but they had only a few weeks’ more food, and storms like these often persisted for two months, sometimes three.
“There’s Ascraeus Mons,” Arkady said, pointing at the radar screen. “Good image.” He laughed. “Best view of it we’re going to get this time around, I’m afraid. Too bad, I was really looking forward to seeing them! Remember Elysium?”
“Yeah yeah,” Nadia said, busy running simulations of the batteries’ efficiency. Daily sunlight was near its perihelion peak, which was why the storm had started in the first place; and the instruments said that about 20 percent of full daylight was penetrating to this level (it felt to her eye more like 30 or 40); therefore it might be possible to run the props half the time, which would help tremendously. Without them they were losing altitude although that might just be the ground rising under them. With the props they might be able to hold a steady altitude, and influence their course by a degree or two.
“How thick is this dust, do you think?”
“How thick?”
“You know, grams per cubic meter. Try to get Ann or Hiroko on the radio and find out, will you?”
She went back to see what they had on board that could be used to power the props. Hydrazine, for the bomb-bay vacuum pumps; the pump motors could be wired to the props, probably. Then there were spare solar panels, and the solar panels in the emergency kit. If she could get them outside she could run whatever extra insolation they caught into the prop batteries. Also, in a sandstorm like this there was light coming from all directions, so some should probably be pointed down. As she rooted through the equipment locker looking for wire and transformer sand tools she told Arkady the idea, and he laughed his madman laugh. “Good idea, Nadia! Great idea.”
“If it works.” She rummaged through the tool kit, sadly smaller than her usual supply. The light in the gondola was eerie, a dim yellow glow flickering with every gust. The view out the side windows