A Fall of Moondust

by Arthur C. Clarke

  He was in the washroom for less than fifteen seconds. When he emerged he was walking quickly, but not quickly enough to cause panic. He went straight to Pat Harris, who was deep in conversation with Commodore Hansteen, and interrupted them without ceremony.

  “Captain,” he said in a low, urgent voice, “we’re on fire. Go and check in the toilet. I’ve not told anyone else.”

  In a second, Pat was gone, and Hansteen with him. In space, as on the sea, no one stopped to argue when he heard the word “Fire.” And Johanson was not the sort of man to raise a false alarm; like Pat, he was a Lunar Administration tech, and had been one of those whom the Commodore had selected for his riot squad.

  The toilet was typical of that on any small vehicle of land, sea, air, or space; one could touch every wall without changing position. But the rear wall, immediately above the washbowl, could no longer be touched at all. The Fiberglas was blistered with heat, and was buckling and bulging even while the horrified spectators looked at it.

  “My God!” said the Commodore. “That will be through in a minute. What’s causing it?”

  But Pat had already gone. He was back a few seconds later, carrying the cabin’s two small fire extinguishers under his arms.

  “Commodore,” he said, “go and report to the raft. Tell them we may only have a few minutes. I’ll stay here in case it breaks through.”

  Hansteen did as he was told. A moment later Pat heard his voice calling the message into the microphone, and the sudden turmoil among the passengers that followed. Almost immediately the door opened again, and he was joined by McKenzie.

  “Can I help?” asked the scientist.

  “I don’t think so,” Pat answered, holding the extinguisher at the ready. He felt a curious numbness, as if this was not really happening to him, but was all a dream from which he would soon awaken. Perhaps by now he had passed beyond fear; having surmounted one crisis after another, all emotion had been wrung out of him. He could still endure, but he could no longer react.

  “What’s causing it?” asked McKenzie, echoing the Commodore’s unanswered question and immediately following it with another. “What’s behind this bulkhead?”

  “Our main power supply. Twenty heavy-duty cells.”

  “How much energy in them?”

  “Well, we started with five thousand kilowatt-hours. We probably still have half of it.”

  “There’s your answer. Something’s shorting out our power supply. It’s probably been burning up ever since the overhead wiring got ripped out.”

  The explanation made sense, if only because there was no other source of energy aboard the cruiser. She was completely fireproof, so could not support an ordinary combustion. But there was enough electrical energy in her power cells to drive her at full speed for hours on end, and if this dissipated itself in raw heat the results would be catastrophic.

  Yet this was impossible; such an overload would have tripped the circuit breakers at once—unless, for some reason, they had jammed.

  They had not, as McKenzie reported after a quick check in the air lock.

  “All the breakers have jumped,” he said. “The circuits are as dead as mutton. I don’t understand it.”

  Even in this moment of peril, Pat could hardly refrain from smiling. McKenzie was the eternal scientist; he might be about to die, but he would insist on knowing how. If he was being burned at the stake—and a similar fate might well be in store—he would ask his executioners, “What kind of wood are you using?”

  The folding door creased inward as Hansteen came back to report.

  “Lawrence says he’ll be through in ten minutes,” he said. “Will that wall hold until then?”

  “God knows,” answered Pat. “It may last for another hour—it may go in the next five seconds. Depends how the fire’s spreading.”

  “Aren’t there automatic fire-fighting appliances in that cornpartment?”

  “There’s no point in having them—this is our pressure bulkhead, and there’s normally vacuum on the other side. That’s the best fire fighter you can get.”

  “That’s it!” exclaimed McKenzie. “Don’t you see? The whole compartment’s flooded. When the roof tore, the dust started to work its way in. It’s shorting all the electrical equipment.”

  Pat knew, without further discussion, that McKenzie was right. By now all the sections normally open to space must be packed with dust. It would have poured in through the broken roof, flowed along the gap between the double hull, slowly accumulated around the open bus bars in the power compartment. And then the pyrotechnics would have started: there was enough meteoric iron in the dust to make it a good conductor. It would be arcing and shorting in there like a thousand electric fires.

  “If we sprinkled water on that wall,” said the Commodore, “would it help matters—or would it crack the Fiberglas?”

  “I think we should try it,” answered McKenzie, “but very carefully—not too much at a time.” He filled a plastic cup—the water was already hot—and looked enquiringly at the others. Since there were no objections, he began to splash a few drops on the slowly blistering surface.

  The cracklings and poppings that resulted were so terrifying that he stopped at once. It was too big a risk; with a metal wall, it would have been a good idea, but this nonconducting plastic would shatter under the thermal stresses.

  “There’s nothing we can do in here,” said the Commodore. “Even those extinguishers won’t help much. We’d better get out and block off this whole compartment. The door will act as a fire wall, and give us some extra time.”

  Pat hesitated. The heat was already almost unbearable, but it seemed cowardice to leave. Yet Hansteen’s suggestion made excellent sense; if he stayed here until the fire broke through, he would probably be gassed at once by the fumes.

  “Right—let’s get out,” he agreed. “We’ll see what kind of barricade we can build behind this door.”

  He did not think they would have much time to do it; already he could hear, quite distinctly, a frying, blistering sound from the wall that was holding the inferno at bay.

  CHAPTER THIRTY

  The news that Selene was on fire made no difference at all to Lawrence’s actions. He could not move any faster than he was doing now; if he attempted it, he might make a mistake, just when the trickiest part of the entire job was coming up. All he could do was to forge ahead, and hope that he would beat the flames.

  The apparatus now being lowered down the shaft looked like an overgrown grease gun, or a giant version of those syringes used to put icing on wedding cakes. This one held neither grease nor icing, but an organic silicon compound under great pressure. At the moment it was liquid; it would not remain so for long.

  Lawrence’s first problem was to get the liquid between the double hull, without letting the dust escape. Using a small rivet gun, he fired seven hollow bolts into Selene’s outer skin—one in the center of the exposed circle, the other six evenly spaced around its circumference.

  He connected the syringe to the center bolt, and pressed the trigger. There was a slight hiss as the fluid rushed through the hollow bolt, its pressure opening a tiny valve in the bulletshaped nose. Working very swiftly, Lawrence moved from bolt to bolt, shooting equal charges of fluid through each. Now the stuff would have spread out almost evenly between the two hulls, in a ragged pancake more than a meter across. No—not a pancake—a souffle, for it would have started to foam as soon as it escaped from the nozzle.

  And a few seconds later, it would have started to set, under the influence of the catalyst injected with it. Lawrence looked at his watch; in five minutes that foam would be rock-hard, though as porous as pumice—which, indeed, it would very closely resemble. There would be no chance of more dust entering this section of the hull; what was already there was frozen in place.

  There was nothing he could do to shorten that five minutes; the whole plan depended upon the foam setting to a known consistency. If his timing and positioning had been faulty
, or the chemists back at Base had made an error, the people aboard Selene were already as good as dead.

  He used the waiting period to tidy up the shaft, sending all the equipment back to the surface. Soon only Lawrence himself was left at the bottom, with no tools at all but his bare hands. If Maurice Spenser could have smuggled his camera into this narrow space—and he would have signed any reasonable contract with the Devil to have done so-his viewers would have been quite unable to guess Lawrence’s next move.

  They would have been still more baffled when what looked like a child’s hoop was slowly lowered down the shaft. But this was no nursery toy; it was the key that would open Selene.

  Sue had already marshaled the passengers to the front—and now much higher—end of the cabin. They were all standing there in a tightly packed group, looking anxiously at the ceiling and straining their ears for every encouraging sound.

  Encouragement, thought Pat, was what they needed now. And he needed it more than any of them, for he alone knew—unless Hansteen or McKenzie had guessed it—the real magnitude of the danger they were facing.

  The fire was bad enough, and could kill them if it broke through into the cabin. But it was slow-moving, and they could fight it, even if only for a while. Against explosion, however, they could do nothing.

  For Selene was a bomb, and the fuse was already lit. The stored-up energy in the power cells that drove her motors and all her electrical devices could escape as raw heat, but it could not detonate. That was not true, unfortunately, of the liquidoxygen tanks.

  They must still hold many liters of the fearfully cold, violently reactive element. When the mounting heat ruptured those tanks, there would be both a physical and a chemical explosion. A small one, it was true—perhaps equivalent to a hundred kilograms of T.N.T. But that would be quite enough to smash Selene to pieces.

  Pat saw no point in mentioning this to Hansteen, who was already planning his barricade. Seats were being unscrewed from the rows near the front of the cabin, and jammed between the rear row and the toilet door. It looked as if the Commodore was preparing for an invasion rather than a fire—as indeed he was. The fire itself, because of its nature, might not spread beyond the power-cell compartment, but as soon as that cracked and blistered wall finally gave way, the dust would come flooding through.

  “Commodore,” said Pat, “while you’re doing this, I’ll start organizing the passengers. We can’t have twenty people trying to get out at once.”

  That was a nightmare prospect that had to be avoided at all costs. Yet it would be hard to avoid panic—even in this welldisciplined community—if a single narrow tunnel was the only means of escape from a rapidly approaching death.

  Pat walked to the front of the cabin; on Earth that would have been a steep uphill climb, but here a thirty-degree slope was barely noticeable. He looked at the anxious faces ranged in front of him and said: “We’re going to be out of here very soon. When the ceiling opens, a rope ladder will be dropped down. The ladies will go first, then the men—all in alphabetical order. Don’t bother to use your feet. Remember how little you weigh here, and go up hand over hand, as quickly as you can. But don’t crowd the person in front; you should have plenty of time, and it will take you only a few seconds to reach the top.

  “Sue, please sort everyone out in the right order. Harding, Bryan, Johanson, Barrett—I’d like you to stand by as you did before. We may need your help-“

  He did not finish the sentence. There was a kind of soft, muffled explosion from the rear of the cabin—nothing spectacular; the popping of a paper bag would have made more noise. But it meant that the wall was down—while the ceiling, unfortunately, was still intact.

  On the other side of the roof, Lawrence laid his hoop flat against the Fiberglas and started to fix it in position with quick-drying cement. The ring was almost as wide as the little well in which he was crouching; it came to within a few centimeters of the corrugated walls. Though it was perfectly safe to handle, he treated it with exaggerated care. He had never acquired that easy familiarity with explosives that characterizes those who have to live with them.

  The ring charge he was tamping in place was a perfectly conventional specimen of the art, involving no technical problems. It would make a neat clean out of exactly the desired width and thickness, doing in a thousandth of a second a job that would have taken a quarter of an hour with a power saw. That was what Lawrence had first intended to use; now he was very glad that he had changed his mind. It seemed most unlikely that he would have a quarter of an hour.

  How true that was, he learned while he was still waiting for the foam to set. “The fire’s through into the cabin!” yelled a voice from overhead.

  Lawrence looked at his watch. For a moment it seemed as if the second hand was motionless, but that was an illusion he had experienced all his life. The watch had not stopped; it was merely that Time, as usual, was not going at the speed he wished. Until this moment it had been passing too swiftly; now, of course, it was crawling on leaden feet.

  The foam should be rock-hard in another thirty seconds. Far better to leave it a little longer than to risk shooting too soon, while it was still plastic.

  He started to climb the rope ladder, without haste, trailing the thin detonating wires behind him. His timing was perfect. When he had emerged from the shaft, uncrimped the short circuit he had put for the sake of safety at the end of the wires, and connected them to the exploder, there were just ten seconds to go.

  “Tell them we’re starting to count down from ten,” he said.

  As Pat raced downhill to help the Commodore—though just what he could do now, he had very little idea—he heard Sue calling in an unhurried voice: “Miss Morley, Mrs. Schuster, Mrs. Williams . . .” How ironic it was that Miss Morley would once again be the first, this time by virtue of alphabetical accident. She could hardly grumble about the treatment she was getting now.

  And then a second and much grimmer thought flashed through Pat’s mind. Suppose Mrs. Schuster got stuck in the tunnel and blocked the exit. Well, they could hardly leave her until last. No, she’d go up all right; she had been a deciding factor in the tube’s design, and since then she had lost several kilos.

  At first glance, the outer door of the toilet still seemed to be holding. Indeed, the only sign that anything had happened was a slight wisp of smoke curling past the hinges. For a moment Pat felt a surge of relief; why, it might take the fire half an hour to burn through the double thickness of Fiberglas, and long before that—

  Something was tickling his bare feet. He had moved automatically aside before his conscious mind said, “_What’s that?_”

  He looked down. Though his eyes were now accustomed to the dim emergency lighting, it was some time before he realized that a ghostly gray tide was pouring beneath that barricaded door—and that the panels were already bulging inward under the pressure of tons of dust. It could be only a matter of minutes before they collapsed; even if they held, it might make little difference. That silent, sinister tide had risen above his ankles even while he was standing here.

  Pat did not attempt to move, or to speak to the Commodore, who was standing equally motionless a few centimeters away. For the first time in his life—and now, it might well be, for the last—he felt an emotion of sheer, overwhelming hate. In that moment, as its million dry and delicate feelers brushed against his bare legs, it seemed to Pat that the Sea of Thirst was a conscious, malignant entity that had been playing with them like a cat with a mouse. Every time, he told himself, we thought we were getting the situation under control, it was preparing a new surprise. We were always one move behind, and now it is tired of its little game; we no longer amuse it. Perhaps Radley was right, after all.

  The loud-speaker dangling from the air pipe roused him from his fatalistic reverie.

  “We’re ready!” it shouted. “Crowd at the end of the bus and cover your faces. I’ll count down from ten.

  “TEN.”

  We’re already a
t the end of the bus, thought Pat. We don’t need all that time. We may not even have it.

  “NINE.”

  I’ll bet it doesn’t work, anyway. The Sea won’t let it, if It thinks we have a chance of getting out.

  “EIGHT.”

  A pity, though, after all this effort. A lot of people have half killed themselves trying to help us. They deserved better luck.

  “SEVEN.”

  That’s supposed to be a lucky number, isn’t it? Perhaps we may make it, after all. Some of us.

  “SIX.”

  Let’s pretend. It won’t do much harm now. Suppose it takes—oh, fifteen seconds to get through—

  “FIVE.”

  And, of course, to let down the ladder again; they probably rolled that up for safety—

  “FOUR.”

  And assuming that someone goes out every three seconds—no, let’s make it five to be on the safe side—

  “THREE.”

  That will be twenty-two times five, which is one thousand and—no, that’s ridiculous; I’ve forgotten how to do simple arithmetic—

  “TWO.”

  Say one hundred and something seconds, which must be the best part of two minutes, and that’s still plenty of time for those lox tanks to blow us all to kingdom come—

  “ONE.”

  ONE! And I haven’t even covered my face; maybe I should lie down even if I have to swallow this filthy stinking dust—

  There was a sudden, sharp crack and a brief puff of air; that was all. It was disappointingly anticlimactic, but the explosives experts had known their job, as is highly desirable that explosives experts should. The energy of the charge had been precisely calculated and focused; there was barely enough left over to ripple the dust that now covered almost half the floor space of the cabin.