At five miles above the ground, the little furnace was glowing white hot, judging from the amount of light striking the photocell inside the nose compartment. Atmospheric pressure was quite measurable, though far from sufficient from the Sarrian point of view, if the Bourdon gauge could be trusted; and Feth claimed to have worked out a correction table by calibrating several of them on the dark side of Planet One.
“Can you hold it at this height for a while?” Ken asked. “I’m going to let this titanium act up here, if I possibly can. There’s atmosphere, and we’re high enough not to be visible, I should think.” Allmer gestured to the reading of the photocell.
“The door is open, and that furnace is shining pretty brightly. You’d do better to shut the door, only that would keep air pretty well out. A light like that so far from the ground must show for scores of miles.”
“I never thought of that.” Ken was a trifle startled. He thought for a moment, then, “Well, let’s close the door anyway. We have a pressure reading. If that drops, we’ll know that some sort of action is taking place.”
“True enough.” Allmer snapped the toggle closing the door and waited silently while Ken manipulated his controls. Deprived of the opening through which a good deal of heat had been radiating, the compartment temperature began to climb. By rights, the pressure should have done the same; but to Ken’s intense satisfaction, it did not — it fell, instead. At his request, the door was opened for an instant and promptly closed again; results were consistent. The pressure popped back to its former value, then fell off once more. Apparently the titanium was combining with some gaseous component of the surrounding atmosphere, though not violently enough for the reaction to be called combustion.
“If you’re far enough to one side of the beam, let’s go down to the surface,” the investigator finally said. “I’d like to find out what percentage of the air will react this way, and for any sort of accuracy I’ll need all the atmospheric pressure I can get to start with.”
Feth Allmer gave the equivalent of a nod.
“We’re a couple of miles to one side,” he said. “I can drop straight down whenever you want. Do you want the door open or closed?”
“Closed. I’ll let the sample cool a little, so we can get normal pressure after landing without using it all up. Then I’ll warm it up again, and see how much of the air in the compartment is used up.” Feth gestured agreement, and a faint whistling became audible as the torpedo began to fall without power — like the others, it had speaker and sound pickups, which Allmer had not bothered to remove. Four miles — three — two — one — with deceptive casualness, the mechanic checked the plunge with a reading of one hundred fifty feet on the altimeter, and eased it very cautiously downward. As he did so, he gestured with one tentacle at another dial; and Ken, after a moment, understood. The projectile was already below the level of the homing station.
“I suppose the transmitter is on a mountain, and we’re letting down into a valley,” Feth elaborated, without taking his eyes from his work.