There were six large thumbscrews spaced around the circumference of the metal disc on which Lawrence was sitting, and he started to turn them one by one, like a drummer tuning his instrument. Connected to the lower side of the platform was a short piece of concertina-like tubing, almost as wide as the caisson, and now folded flat. It formed a flexible coupling large enough for a man to crawl through, and was now slowly opening as Lawrence turned the screws.
One side of the corrugated tube had to stretch through forty centimeters to reach the sloping roof; the other had to move scarcely at all. Lawrence's chief worry had been that the resistance of the dust would prevent the concertina from opening, but the screws were easily overcoming the pressure.
Now none of them could be tightened any further; the lower end of the coupling must be flush against Selene's roof, and sealed to it, he hoped, by the rubber gasket around its rim. How tight that seal was, he would very soon know.
Automatically checking his escape route, Lawrence glanced up the shaft. He could see nothing past the glare of the floodlight hanging two meters above his head, but the rope ladder stretching past it was extremely reassuring.
I've let down the connector, he shouted to his invisible colleagues. It seems to be flush against the roof. Now I'm going to open the valve.
Any mistake now, and the whole shaft would be flooded, perhaps beyond possibility of further use. Slowly and gently, Lawrence released the trap door which had allowed the dust to pass through the piston while it was descending. There was no sudden upwelling; the corrugated tube beneath his feet was holding back the Sea.
Lawrence reached through the valve and his fingers felt the roof of Selene, still invisible beneath the dust but now only a handsbreath away. Few achievements in all his life had ever given him such a sense of satisfaction. The job was still far from finished but he had reached the cruiser. For a moment he crouched in his little pit, feeling as some old-time miner must have when the first nugget of gold gleamed in the lamplight.
He banged three times on the roof. Immediately, his signal was returned. There was no point in striking up a Morse conversation, for, if he wished, he could talk directly through the microphone circuit, but he knew the psychological effect that his tapping would have. It would prove to the men and women in Selene that rescue was now only centimeters away.
Yet there were still major obstacles to be demolished, and the next one was the manhole cover on which he was sitting the face of the piston itself. It had served its purpose, holding back the dust while the caisson was being emptied, but now it had to be removed before anyone could escape from Selene. This had to be done, however, without disturbing the flexible coupling that it had helped to place in position.
To make this possible, the circular face of the piston had been built so that it could be lifted out, like a saucepan lid, when eight large bolts were unscrewed. It took Lawrence only a few minutes to deal with these and to attach a rope to the new loose metal disc; then he shouted, Haul away!
A fatter man would have had to climb the shaft while the circular lid came up after him, but Lawrence was able to squeeze against the wall while the metal plate, moving edgeways, was hoisted past him. There goes the last line of defense, he told himself, as the disc vanished overhead. Now it would be impossible to seal the shaft again if the coupling failed and the dust started to pour in.
Bucket! he shouted. It was already on its way down.
Forty years ago, thought Lawrence, I was playing on a California beach with bucket and spade, making castles in the sand. Now here I am on the Moon Chief Engineer, Earthside, no less shoveling in even deadlier earnest, with the whole human race looking over my shoulder.
When the first load was hoisted up, he had exposed a considerable area of Selene's roof. The volume of dust trapped inside the coupling-tube was quite small, and two more bucketfuls disposed of it.
Before him now was the aluminized fabric of the sun shield, which had long ago crumpled under the pressure. Lawrence cut it away without difficulty it was so fragile that he could tear it with his bare hands and exposed the slightly roughened Fiberglas of the outer hull. To cut through that with a small power saw would be easy; it would also be fatal.
For by this time Selene's double hull had lost its integrity; when the roof had been damaged, the dust would have flooded into the space between the two walls. It would be waiting there, under pressure, to come spurting out as soon as he made his first incision. Before he could enter Selene, that thin but deadly layer of dust would have to be immobilized.
Lawrence rapped briskly against the roof; as he had expected, the sound was muffled by the dust. What he did not expect was to receive an urgent, frantic tattoo in reply.
This, he could tell at once, was no reassuring I'm O. K. signal from inside the cruiser. Even before the men overhead could relay the news to him, Lawrence had guessed that the Sea of Thirst was making one final bid to keep its prey.
Because Karl Johanson was a nucleonics engineer, had a sensitive nose, and happened to be sitting at the rear of the bus, he was the one who spotted the approach of disaster. He remained quite still for a few seconds, nostrils twitching, then said Excuse me to his companion in the aisle seat, and strolled quietly to the washroom. He did not wish to cause alarm if there was no need, especially when rescue seemed so near. But in his professional lifetime he had learned, through more examples than he cared to remember, never to ignore the smell of burning insulation.
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?