A Fall of Moondust

He reported this to Lawrence, who received the news with thankfulness. Now that he was reasonably sure that Selene would not shift again, he was confident that he could get these people out. Exactly how, he was not yet certain, but the plan was beginning to form in his mind.

It took shape over the next twelve hours, in conferences with his brains trust and experiments on the Sea of Thirst . The Engineering Division had learned more about the dust in the last week than during the whole of its previous existence. It was no longer fighting in the dark against a largely unknown opponent. It understood which liberties could be taken, and which could not.

Despite the speed with which the changed plans were drawn up and the necessary hardware constructed, there was no undue haste and certainly no carelessness. For this was another operation that had to work the first time. If it failed, then at the very least the caisson would have to be abandoned and a new one sunk. And at the worst—those aboard Selene would be drowned in dust.

“It's a pretty problem,” said Tom Lawson, who liked pretty problems—and not much else. “The lower end of the caisson's wide open to the dust, because it's resting against Selene at only one point, and the tilt of the roof prevents it from sealing. Before we can pump out the dust, we have to close that gap.

“Did I say 'pump'? That was a mistake. You can't pump the stuff; it has to be lifted. And if we tried that as things are now, it would flow in just as fast at the bottom of the tube as we took it out of the top.”

Tom paused and grinned sardonically at his multimillion audience, as if challenging it to solve the problem he had outlined. He let his viewers stew in their own thoughts for a while, then picked up the model lying on the studio table. Though it was an extremely simple one, he was rather proud of it, for he had made it himself. No one could have guessed, from the other side of the camera, that it was only cardboard sprayed with aluminum paint.

“This tube,” he said, “represents a short section of the caisson that's now leading down to Selene—and which, as I said, is full of dust. Now this—” with his other hand, he picked up a stubby cylinder, closed at one end—“fits snugly inside the caisson, like a piston. It's very heavy, and will try to sink under its own weight. But it can't do so, of course, while the dust is trapped underneath it.”

Tom turned the piston until its flat end was toward the camera. He pressed his forefinger against the center of the circular face, and a small trap door opened.

“This acts as a valve. When it's open, dust can flow through and the piston can sink down the shaft. As soon as it reaches the bottom, the valve will be closed by a signal from above. That will seal off the caisson, and we can start scooping out the dust.

“It sounds very simple, doesn't it? Well, it's not. There are about fifty problems I haven't mentioned. For example, as the caisson is emptied, it will try to float up to the surface with a lift of a good many tons. Chief Engineer Lawrence has worked out an ingenious system of anchors to hold it down.

“You'll realize, of course, that even when this tube has been emptied of dust, there will still be that wedge-shaped gap between its lower end and Selene's roof. How Mister Lawrence proposes to deal with that, I don't know. And please don't send me any more suggestions; we've already had enough half-baked ideas on this program to last a lifetime.

“This-piston gadget—isn't just theory. The engineers here have built and tested it during the last twelve hours, and it's now in action. If I can make any sense of the signals the man's waving at me, I think we're now going over to the Sea of Thirst , to find out what's happening on the raft.”

The temporary studio in the Hotel Roris faded from a million screens; in its place was the picture that, by this time, must have been familiar to most of the human race.

There were now three igloos of assorted sizes on or around the raft; as the sunlight glinted from their reflecting outer surfaces, they looked like giant drops of mercury. One of the dustskis was parked beside the largest dome; the other two were in transit, still shuttling supplies from Port Roris.

Like the mouth of a well, the caisson projected from the Sea. Its rim was only twenty centimeters above the dust, and the opening seemed much too narrow for a man to enter. It would, indeed, have been a very tight fit for anyone wearing a space suit—but the crucial part of this operation would be done without suits.