Arthur Clarke - A Fall of Moondust

“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.

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 liquid oxygen 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.