The Sentinel - Arthur C. Clarke [39]
“But what about the alarms? The air pressure’s normal—how could we have been holed?”
“We weren’t,” McNeil replied. “You know how the oxygen circulates night-side through the refrigerating coils to keep it liquid? The meteor must have smashed them and the stuff simply boiled away.”
Grant was silent, collecting his thoughts. What had happened was serious—deadly serious—but it need not be fatal. After all, the voyage was more than three quarters over.
“Surely the regenerator can keep the air breathable, even if it does get pretty thick?” he asked hopefully.
McNeil shook his head. “I’ve not worked it out in detail, but I know the answer. When the carbon dioxide is broken down and the free oxygen gets cycled back there’s a loss of about ten percent. That’s why we have to carry a reserve.”
“The space suits!” cried Grant in sudden excitement. “What about their tanks?”
He had spoken without thinking, and the immediate realization of his mistake left him feeling worse than before.
“We can’t keep oxygen in them—it would boil off in a few days. There’s enough compressed gas there for about thirty minutes—merely long enough for you to get to the main tank in an emergency.”
“There must be a way out—even if we have to jettison cargo and run for it. Let’s stop guessing and work out exactly where we are.”
Grant was as much angry as frightened. He was angry with McNeil for breaking down. He was angry with the designers of the ship for not having foreseen this God-knew-how-many-million-to-one chance. The deadline might be a couple of weeks away and a lot could happen before then. The thought helped for a moment to keep his fears at arm’s length.
This was an emergency, beyond doubt, but it was one of those peculiarly protracted emergencies that seem to happen only in space. There was plenty of time to think—perhaps too much time.
Grant strapped himself in the pilot’s seat and pulled out a writing-pad.
“Let’s get the facts right,” he said with artificial calmness. “We’ve got the air that’s still circulating in the ship and we lose ten percent of the oxygen every time it goes through the generator. Chuck me over the Manual, will you? I can never remember how many cubic meters we use a day.”
In saying that the Star Queen might expect to be hit by a meteor once every century, McNeil had grossly but unavoidably oversimplified the problem. For the answer depended on so many factors that three generations of statisticians had done little but lay down rules so vague that the insurance companies still shivered with apprehension when the great meteor showers went sweeping like a gale through the orbits of the inner worlds.
Everything depends, of course, on what one means by the word meteor. Each lump of cosmic slag that reaches the surface of the Earth has a million smaller brethren that perish utterly in the no-man’s-land where the atmosphere has not quite ended and space has yet to begin—that ghostly region where the weird Aurora sometimes walks by night.
These are the familiar shooting stars, seldom larger than a pin’s head, and these in turn are outnumbered a millionfold again by particles too small to leave any visible trace of their dying as they drift down from the sky. All of them, the countless specks of dust, the rare boulders and even the wandering mountains that Earth encounters perhaps once every million years—all of them are meteors.
For the purposes of space-flight, a meteor is only of interest if, on penetrating the hull of a ship, it leaves a hole large enough to be dangerous. This is a matter of relative speeds as well as size. Tables have been prepared showing approximate collision times for various parts of the Solar System—and for various sizes of meteors down to masses of a few milligrams.
That which had struck the Star Queen was a giant, being nearly a centimeter across and weighing all of ten grams. According to the table the waiting-time for collision with such a monster was of the order of ten to the ninth days—say three million years. The virtual certainty that such an