then could a unit or a group of units be sealed off against the full pressure of the ocean?"
"You mean, in the way that Luna City can have its component units automatically sealed off in case of meteorite puncture in order to limit damage to a single unit."
"Yes," said Demerest with a faint bitterness. "As did not happen recently."
"In theory, we could do that, but the chances of accident are much less down here. As I said, there are no meteorites and, what's more, there are no currents to speak of. Even an earthquake centered immediately below us would not be damaging since we make no fixed or solid contact with the ground beneath and are cushioned by the ocean itself against the shocks. So we can afford to gamble on no massive influx."
"Yet if one happened?"
"Then we could be helpless. You see, it is not so easy to seal off component units here. On the Moon, there is a pressure differentia] of just one atmosphere; one atmosphere inside and the zero atmosphere of vacuum outside. A thin seal is enough. Here at Ocean-Deep the pressure differential is roughly a thousand atmospheres. To secure absolute safety against that differentia] would take a great deal of money and you know what you said about getting money out of PPC. So we gamble and so far we've been lucky."
"And we haven't," said Demerest.
Bergen looked uncomfortable, but Annette distracted both by coming in with lunch at this moment.
She said, "I hope, Mr. Demerest, that you're prepared for Spartan fare. All our food in Ocean-Deep is prepackaged and requires only heating. We specialize in blandness and nonsurprise here, and the non-surprise of the day is a bland chicken a la king, with carrots, boiled potatoes, a piece of something that looks like a brownie for dessert, and, of course, all the coffee you can drink. "
Demerest rose to take his tray and tried to smile. "It sounds very like Moon fare, Mrs. Bergen, and I was brought up on that. We grow our own micro-organismic food. It is patriotic to eat that but not particularly enjoyable. We hope to keep improving it, though."
"I'm sure you will improve it...
Demerest said, as he ate with a slow and methodical chewing, "I hate to ride my specialty, but how secure are you against mishaps in your air-lock entry?"
"It is the weakest point of Ocean-Deep," said Bergen. He had finished eating, well ahead of the other two, and was half through with his first cup of coffee. "But there's got to be an interface, right? The entry is as automatic as we can make it and as fail-safe. Number one: there has to be contact at every point about the outer lock before the fusion generator begins to heat the water within the lock. What's more, the contact has to be metallic and of a metal with just the magnetic permeability we use on our 'scaphes. Presumably a rock or some mythical deep-sea monster might drop down and make contact at just the right places; but if so, nothing happens.
"Then, too, the outer door doesn't open until the steam has pushed the water out and then condensed; in other words, not till both pressure and temperature have dropped below a certain point. At the moment the outer door begins to open, a relatively slight increase in internal pressure, as by water entry, will close it again."
Demerest said, "But then, once men have passed through the lock, the inner door closes behind them and sea water must be allowed into the lock again. Can you do that gradually against the full pressure of the ocean outside?"
"Not very." Bergen smiled. "It doesn't pay to fight the ocean too hard. You have to roll with the punch. We slow it down to about one-tenth free entry but even so it comes in like a rifle shot-louder, a thunderclap, or waterclap, if you prefer. The inner door can hold it, though, and it is not subjected to the strain very often. Well, wait, you heard the waterclap when we first met, when Javan's 'scaphe took off again. Remember?"
"I remember," said Demerest. "But here is something I don't understand. You keep the lock filled with ocean at high pressure at all times to keep the outer door without strain. But that keeps the inner door at full strain. Somewhere there has to be strain."
"Yes, indeed. But if the outer door, with a thousand-atmosphere differential on its two sides, breaks down, the full ocean