Hal Clement - Close to Critical

Sakiiro, with no really objective data to go on, had about concluded that the vessel was down to gliding speed and was going to describe the location of the electrolysis controls to Easy when the motion changed. A series of shuddering jars shook the ship. The girl’s body was held in the seat by the straps, but her head and limbs flapped like those of a scarecrow in a high wind; the young Drommian for the first time failed to stay put. The jolting continued, the thuds punctuated by the girl’s sobs and an almost inaudibly high-pitched whine from Aminadorneldo. The elder Drommian rose once more to his feet and looked anxiously at the screen.

The engineers were baffled; the diplomats were too terrified for their children to have had constructive ideas even had they been qualified otherwise; but Raeker thought he knew the answer.

“They’re hitting raindrops!” he yelled.

He must have been right, it was decided afterward; but the information did not really help. The bathyscaphe jerked and bucked. The autopilot did its best to hold a smooth flight path, but aerodynamic controls were miserably inadequate for the task. At least twice the vessel somersaulted completely, as nearly as Raeker could tell from the way the Drommian was catapulted around the room. Sheer luck kept him out of contact with the control switches. For a time the controls were useless because their efforts were overridden—a rudder trying to force a left turn will not get far if the right wing encounters a fifty-foot sphere of water, even though the water isn’t much denser than the air. Then they were useless because they lacked enough grip on the atmosphere; the ship had given up enough kinetic energy to the raindrops to fall well below its stalling speed—low as that was, in an atmosphere seven or eight hundred times as dense as Earth’s at sea level. By that time, of coarse, the ship was falling, in the oldest and simplest sense of the word. The motion was still irregular, for it was still hitting the drops; but the violence was gone, for it wasn’t hitting them very hard.

The rate of fall was surprisingly small, for a three-G field. The reason was simple enough—even with the outside atmosphere filling most of its volume, the ship had a very low density. It was a two-hundred-foot-long, cigar-like shell, and the only really heavy part was the forty-foot sphere in the center which held the habitable portion. It is quite possible that it would have escaped serious mechanical damage even had it landed on solid ground; and as it happened, the fall ended on liquid.

Real liquid; not the borderline stuff that made up most of Tenebra’s atmosphere.

It landed upside down, but the wings had been shed like the speed brakes and its center of gravity was low enough to bring it to a more comfortable attitude. The floor finally stopped rocking, or at least the Drommian did—with the vision set fastened to the ship, the floor had always seemed motionless to the distant watchers. They saw the otterlike giant get cautiously to his feet, then walk slowly over to the girl’s chair and touch her lightly on the shoulder. She stirred and tried to sit up.

“Are you all right?” Both parents fairly shrieked the question. Aminadorneldo, his father’s orders in mind, waited for Easy to answer.

“I guess so,” she said after a moment. “I’m sorry I bawled, Dad; I was scared. I didn’t mean to scare ’Mina, though.”

“It’s all right, kid. I’m sure no one can blame you, and I don’t suppose your reaction had much to do with your friend’s. The main thing is that you’re in one piece, and the hull’s intact—I suppose you’d be dead by now if it weren’t.”

“That’s true enough,” seconded Sakiiro.

“You’ve had a rough ride, then, but it should be over now. Since you’re there, you might take a look through the windows—you’re the first non-natives ever to do that directly. When you’ve seen all you can or want to, tell Mr. Sakiiro and he’ll tell you how to get upstairs again. All right?”

“All right, Dad.” Easy brushed a forearm across her tear-stained face, unfastened the seat straps, and finally struggled to her feet.

“Golly, when are they going to cut the power? I don’t like all these G’s,” she remarked.

“You’re stuck with them until we get you away from there,” her father replied.

“I know it. I was just kidding. Hmm. It seems to be night outside; I can’t see a thing.”

“It is, if you’re anywhere near the robot,” Raeker replied, “but it wouldn’t make any difference to your eyes if it were high noon. Even Altair can’t push enough light for human eyes through that atmosphere. You’ll have to use the lights.”

“All right.” The girl looked at the board where she had already located the light switches; then, to the surprised approval of the engineers, she made sure from Sakiiro that these were the ones she wanted. Saki admitted later that his hopes of rescuing the pair soared several hundred per cent at that moment.

With the lights on, both children went over to the windows.

“There isn’t much to see,” called Easy. “We seem to have splashed into a lake or ocean. It’s as smooth as glass; not a ripple. I’d think it was solid if the ship weren’t partly under it. There are big foggy globes drifting down, yards and yards across, but they sort of fade out just before they touch, the surface. That’s every bit I can see.”

“It’s raining,” Raeker said simply. “The lake is probably sulphuric acid, I suppose fairly dilute by this time of night, and is enough warmer than the air so the water evaporates before it strikes. There wouldn’t be any waves; there’s no wind. Three knots is a wild hurricane on Tenebra.”

“With all that heat energy running around?” Rich was startled.

“Yes. There’s nothing for it to work on—I use the word in its physical sense. There isn’t enough change in volume when the atmosphere changes temperature, or even changes state, to create the pressure differences you need for high winds. Tenebra is about the calmest place you’ll find inside any atmosphere in the galaxy.”

“Does that jibe with your remarks about earthquakes a while ago?” It was a measure of Aminadabarlee’s revived confidence that he could talk of something besides the stupidity of human beings.

“No, it doesn’t,” admitted Raeker, “and I’ll have to admit, Easy, that there is a possibility that you will encounter some waves if you float there long enough. However, you won’t be able to call them weather, and they won’t carry you to any more interesting places. I’m afraid you’ve seen about all you can expect to, young lady; you may as well come up and be properly rescued.” “All right. Only I’d like to know just what’s going to make this thing float, and whether the trip up will be as rough as the one down was.”

“It won’t. You’ll go up vertically, and much more slowly. You’re going to ride a balloon. The atmosphere there is mostly water, with enough ions loose to make it a decent conductor. The largest part of your hull is divided into cells, and each cell further divided in two by a flexible membrane. Right now, those membranes are squeezed flat against one wall of each cell by atmospheric pressure. When you start the electrolysis units, some of the water will be decomposed; the oxygen will be piped outside the hull, but the hydrogen will be released on the other side of the membranes and gradually drive the air out of the cells. The old bathyscaphe used the same idea, only it didn’t need the membranes to keep the two fluids from diffusing into each other.”

“I see. How long will it take to make enougft gas to lift us?”

“I can’t tell; we don’t know the conductivity of the atmosphere. Once you start things going, there’s a bank of ammeters above the switches for each individual cell; if you’ll give me their reading after things start, I’ll try to calculate it for you.”