I nodded. “I see. Since everything in the Moon has to be sealed airtight, you’ve got to watch out for quakes. These airlocks are to confine your losses.” I started visualizing myself as one of the losses.
“Yes and no. The airlocks would limit an accident all right, if there was one-which there won’t be-this place is safe. Primarily they let us work on a section of the tunnel at no pressure without disturbing the rest of it. But they are more than that; each one is a temporary expansion joint. You can tie a compact structure together and let it ride out a quake, but a thing as long as this tunnel has to give, or it will spring a leak. A flexible seal is hard to accomplish in the Moon.”
“What’s wrong with rubber?” I demanded. I was feeling jumpy enough to be argumentative. “I’ve got a ground-car back home with two hundred thousand miles on it, yet I’ve never touched the tires since they were sealed up in Detroit.”
Knowles sighed. “I should have brought one of the engineers along, Jack. The volatiles that keep rubbers soft tend to boil away in vacuum and the stuff gets stiff. Same for the flexible plastics. When you expose them to low temperature as well they get brittle as eggshells.”
The scooter stopped as Knowles was speaking and we got off just in time to meet half a dozen men coming out of the next airlock. They were wearing spacesuits, or, more properly, pressure suits, for they had hose connections instead of oxygen bottles, and no sun visors. Their helmets were thrown back and each man had his head pushed through the opened zipper in the front of his suit, giving him a curiously two headed look. Knowles called out, “Hey, Konski!”
One of the men turned around. He must have been six feet two and fat for his size. I guessed him at three hundred pounds, earthside. “It’s Mr. Knowles,” he said happily. “Don’t tell me I’ve gotten a raise.”
“You’re making too much money now, Fatso. Shake hands with Jack Arnold. Jack, this is Fatso Konski-the best sandhog in four planets.”
“Only four?” inquired Konski. He slid his right arm out of his suit and stuck his bare hand into mine. I said I was glad to meet him and tried to get my hand back before he mangled It.
“Jack Arnold wants to see how you seal these tunnels,” Knowles went on. “Come along with us.”
Konski stared at the overhead. “Well, now that you mention it, Mr. Knowles, I’ve just finished my shift.”
Knowles said, “Fatso, you’re a money grubber and inhospitable as well. Okay-time-and-a-half.” Konski turned and started unsealing the airlock.
The tunnel beyond looked much the same as the section we had left except that there were no scooter tracks and the lights were temporary, rigged on extensions. A couple of hundred feet away the tunnel was blocked by a bulkhead with a circular door in it. The fat man followed my glance. “That’s the movable lock,” he explained. “No air beyond it. We excavate just ahead of it.”
“Can I see where you’ve been digging?”
“Not without we go back and get you a suit.”
I shook my head. There were perhaps a dozen bladder-like objects in the tunnel, the size and shape of toy balloons. They seemed to displace exactly their own weight of air; they floated without displaying much tendency to rise or settle. Konski batted one out of his way and answered me before I could ask. “This piece of tunnel was pressurized today,” he told me. “These tag-alongs search out stray leaks. They’re sticky inside. They get sucked up against a leak, break, and the goo gets sucked in, freezes and seals the leak.”
“Is that a permanent repair?” I wanted to know.
“Are you kidding? It just shows the follow-up man where to weld.”
“Show him a flexible joint,” Knowles directed.
“Coming up.” We paused half-way down the tunnel and Konski pointed to a ring segment that ran completely around the tubular tunnel. “We put in a flex joint every hundred feet. It’s glass cloth, gasketed onto the two steel sections it joins. Gives the tunnel a certain amount of springiness.”