She was looking at me quizzically. "Audee," she said gently, "I already believe you're an expert on Venus."
I grinned. "But do you get the picture?"
"I think so. It looks pretty bad."
"It is pretty bad, but all the same the Heechee managed to get that little bit of oxygen Out of the mixture, cheaply and easily-remember those extra tunnels they filled-along with inert gases like nitrogen-and they're present only in trace amounts-enough to make a breathing mixture. How? I don't know, but if there's a machine that did it I'd like to find that machine. Next item: aircraft. The Heechee flew around the surface of Venus a lot."
"So do you, Audee! Aren't you a pilot?"
"Airbody pilot, yes. But look what it takes to make an airbody go. There's a surface temperature of seven-thirty-five K, and not enough oxygen to keep a cigarette lit. So my airbody has to have two fuel tanks, one for the fuel, one for the thing to burn it with. That's not just oil and air, you know."
'' . ,
It 15fl t.
"Not here, Dorotha. Not at the kind of ambient temperatures we've got. It takes exotic fuels to get that hot. Did you ever hear of a fellow named Carnot?"
"Old-time scientist, was he? The Carnot cycle fellow?"
"Right again." That was the third time she'd surprised me, I noted cautiously. "The Carnot efficiency of an engine is expressed by its maximum temperature-the heat of combustion, let's say-divided by the temperature of its exhaust. Well, but the temperature
of the exhaust can't be lower than the temperature of whatever it's exhausted into-otherwise you're not running an engine, you're running a refrigerator. And you've got that seven-thirty-five air temperature to fight, so even with special fuels you have basically a lousy engine. Any heat engine on Venus is lousy. Did you ever wonder why there are so few airbodies around? I don't mind; it helps to have something close to a monopoly. But the reason is that they're so damn expensive to run."
"And the Heechee did it better?"
"I think they did."
She laughed again, unexpectedly and once more very attractively. "Why, you poor fellow," she said in good humor, "you're hooked on the stuff you sell, aren't you? You think that one of these days you're going to find the mother tunnel and pick up a few billion dollars' worth of Heechee stuff!"
I wasn't pleased with the way she put that. I wasn't all that happy with the meeting I had set up with Vastra's Third, for that matter; I'd figured that, away from her boyfriend, I could pick this Dorotha Keefer's brains about him pretty easily. It wasn't working out that way. She was making me aware of her as a person, which was an undesirable development in itself-you can't treat a mark as a mark if you think of him, or her, as a fellow human being.
Worse than that, she was making me take a good look at myself.
So I just said, "You may be right. But I'm sure going to give it a good try."
"You're angry, aren't you?"
"No," I lied, "but maybe a little tired. And we've got a long trip tomorrow, so I'd better take you back to the Spindle, Miss Keefer."
V
My airbody was roped down at the edge of the spacepad and was reached the same way the spacepad was reached: elevator to the
surface lock, then a sealed tractor cab to carry us across the dry, rocky, tortured surface of Venus, peeling away under the high-density wind. Normally I kept the airbody under a lashed-down foam housing, of course. You don't leave anything free and exposed on the surface of Venus if you want to find it intact when you get back to it, not even if it's made of chrome steel. I'd had the foam stripped off first thing that morning, when I checked it out and loaded supplies. Now it was ready. I could see it from the bull's-'йye ports of the crawler, through the howling, green-yellow murk outside.
Cochenour and the girl could have seen it too, if they'd known where to look, but they might not have recognized it as something that would fly.
"Did you and Dorrie have a fight?" Cochenour screamed in my ear.
"No fight," I screamed back.
"Don't care if you did. Just wanted to know. You don't have to like each other, just so you do what I want you to do." He was silent for a moment, resting his vocal cords. "Jesus. What a wind."
"Zephyr," I told him. I didn't say any more; he would find out for himself. The area around the spacepad is a sort of natural calm area, by Venusian standards. Orographic lift throws the meanest of the winds up over the pad, and all we get is a sort of confused back
eddy. That makes taking off and landing relatively easy. The bad part of that is that some of the heavy metal compounds in the air settle out on the pad. What passes for air on Venus has layers of red mercuric sulfide and mercurous chloride in the lower reaches, and when you get above them to those pretty fluffy clouds tourists see on the way down, you find that some of them are droplets of sulfuric and hydrochloric and hydrofluoric acid.
