That in itself could be an answer. Joe said sharply, "Hold it, Chief! Somebody watch Sanford! All we've got to do is find which lock he came out of. He couldn't get out until he pumped it empty—and that unlocks the outer door!"
But Sanford laughed once more. He sounded like someone in the highest of high good humor.
"Heroic again, eh? But I took a compressed air bottle in the lock with me. When the outer door was open, I opened the stopcock and shut the door. The air bottle filled the lock behind me. Naturally I'd fasten the door after I came out! One must be intelligent!"
Joe heard Brent muttering, "Yes, he'd do that!"
"Somebody check it!" snapped Joe. "Make sure! It might amuse him to watch us die while he knew we could get back in if we were as smart as he is."
There were clankings on the hull. Men moved, unfastening the lines which held them to the hull to get freedom of movement, but not breaking the links which bound them to each other. Joe saw Haney go grimly back to the task of throwing away the stuff that they had brought out for the purpose. Then Mike's voice, brittle and cagey: "Haney! Quit it!"
Sanford's voice again, horribly amused. "By all means! Don't throw away our garbage! We may need it!"
A voice snapped, "This lock's fastened." Another voice: "And this...." Other voices, with increasing desperation, verified that every airlock was implacably sealed fast by the presence of air pressure inside the lock itself.
Time was passing. Joe had never noticed, before, the minute noises of the air pressure apparatus strapped to his back. His exhaled breath went to a tiny pump that forced it through a hygroscopic filter which at once extracted excess moisture and removed carbon dioxide. The same pump carefully measured a volume of oxygen equal to the removed CO2 and added it to the air it released. The pump made very small sounds indeed, and the valves were almost noiseless, but Joe could hear their clickings.
Something burned him. He had been standing perfectly still while trying to concentrate on a way out. Sunshine had shone uninterruptedly on one side of his space suit for as long as five minutes. Despite the insulation inside, that was too long. He turned quickly to expose another part of himself to the sunlight. He knew abstractedly that the metal underfoot would sear bare flesh that touched it. A few yards away, in the shadow, the metal of the hull would be cold enough to freeze hydrogen. But here it was fiercely hot. It would melt solder. It might—