by Hal Clement
“Worth trying,” was Takoorch’s laconic answer.
Together they approached the frosty barrier. Beetchermarlf built a small cairn of stones leaning against the ice, and set the light, adjusted for full brightness, at its top. They both crowded close, their front ends part way up the heap of pebbles, and watched the space between the lamp and the ice.
“Come to think of it,” Takoorch remarked as they waited, “our bodies give off some heat, don’t they? Shouldn’t our just being here help melt this stuff?”
“I suppose so.” Beetchermarlf was dubious. “We’d better watch to make sure that it doesn’t freeze at each side and around behind us while we’re waiting here.”
“What will that matter? If it does, it means that we and the light together are enough to fight the freezing, and we should be able to melt our way out.”
“That’s true. Watch, though, so we’ll know if that’s happening.” Takoorch gestured agreement, and they fell silent again.
The older helmsman, however, was not the type to endure silence indefinitely, and presently he gave utterance to another idea.
“I know our knives didn’t make much impression on the ice, but shouldn’t it help if we did some scraping right here where it’s nearest the light?” He unclipped one of the blades they carried for general use and reached toward the ice.
“Wait a minute!” exclaimed Beetchermarlf. “If you start working there, how are we ever going to know whether the heat is having any effect?”
“If my knife gets us anywhere, who cares whether it’s the heat or the work?” retorted Takoorch. Beetchermarlf found no good answer ready, so he subsided, muttering something about “controlled experiments” while the other Mesklinite went to work with his tiny blade.
As it happened, his interference did not spoil the experiment, though it may have delayed slightly the appearance of observable results. Body heat, lamp heat, and knife all together proved unequal to the job; the ice continued to gain. They had to remove the lamps from the cairn at last, and watch the latter slowly become enveloped in the crystalline wall.
“It won’t be long now,” Takoorch remarked as he swung the lights around them. “Only two of the power units are free, now. Should we charge up the lights again before they go, or isn’t it worth the trouble?”
“We might as well,” answered Beetchermarlf. “It seems a pity that that’s the only use we can get out of all that power—four of those things can push the Kwembly around on level ground, and I once heard a human being say that one could do it if it could get traction. That certainly could chip ice for us
if we could find a way to apply it.”
“We can take the power box out easily enough, but what we’d do afterward beats me. The units put out electric current as one choice, but I don’t see how we could shock the ice away. The mechanical torque you can get from them works only on the motor shafts.”
“We’d be more likely to shock ourselves away if we used the current. I don’t know very much about electricity—it was mostly plain mechanics I got in the little time I was at the College—but I know enough of it can kill. Think of something else.”
Takoorch endeavored to comply. Like his young companion, he had had only a short period of exposure to alien knowledge; both had volunteered for the Dhrawn project in preference to further classwork. Their knowledge of general physics might have compared fairly well with that of Benj Hoffman when he was ten or twelve years old. Neither was really comfortable in thinking about matters for which no easily visualized model could be furnished.
They were not, however, lacking in the ability to think abstractly. Both had heard of heat as representing a lowest common denominator of energy, even if they didn’t picture it as random particle motion.
It was Beetchermarlf who first thought of another effect of electricity.
“Tak! Remember the explanations we got about not putting too much power into the trucks until the cruiser got moving? The humans said it was possible to snap the treads, or damage the motors, if we tried to accelerate too fast.”
“That’s right. Quarter power is the limit below a hundred cables per hour.”
“Well, we have the power controls here where we can get at them, and those motors certainly aren’t going to turn. Why not just turn power on this truck and let the motor get as hot as it wants to?”
“What makes you think it will get hot? You don’t know what makes those motors go any more than I do. They didn’t say it would make them hot, just that it was bad for them.”
“I know, but what else could it be? You know that any sort of energy that isn’t used up some other way turns into heat.”
“That doesn’t sound quite right, somehow,” returned the older sailor. “Still, I guess anything is worth trying now. They didn’t say anything about the motor’s wrecking the rest of the ship, too; and if it ruins us—well, we won’t be much worse off.”
Beetchermarlf paused; the thought that he might be endangering the Kwembly hadn’t crossed his mind. The more he thought of it, the less he felt justified in taking the chance. He looked at the relatively tiny power unit nestling between the treads of the nearby truck, and wondered whether such a minute thing could really be a danger to the huge bulk above them. Then he remembered the vastly greater size of the machine which had brought him and his fellows to Dhrawn, and realized that the sort of power which could hurl such immense masses through the sky was not to be handled casually. He would never be afraid to use such engines, since he had been given a chance to become familiar with their normal and proper handling; but deliberately misusing one of them was a different story.
“You’re right,” he admitted somewhat inaccurately—Takoorch had been, after all, willing to take the chance. “We’ll have to work it differently. Look, if the tracks are free to turn, then we can’t damage the motor or the power box; and just stirring up water will warm it.”
“You think so? I remember hearing something like that, but if I can’t break up this ice with my own strength it’s hard to see how simply stirring water is going to do it. Besides, the trucks aren’t free; they’re on the bottom with the Kwembly’s weight on them.”
“Right. You wanted to dig. Start moving rocks; that ice is getting close.”
Beetchermarlf set the example and began prying the rounded cobbles from the edges of the treads. It was a hard job even for Mesklinite muscles. Smooth as they were, the stones were tightly packed; and when one was moved, there was not too much room in which to put it. The ones under the treads, which, of course, were the ones that really had to be shifted, could not even be reached until the ones at the sides were out of the way. The two labored furiously to clear a ditch around the truck, and were frightened at the time it took.
When the ditch was deep enough they tried to pry stones from under the treads, and this was even more discouraging.
The Kwembly had a mass of about two hundred tons. On Dhrawn, this meant a weight of sixteen million pounds to distribute among the fifty-six remaining trucks, and the mattress did a good job of distributing. Three hundred thousand pounds, even if it is a rather short three hundred thousand, is rather too much even for a Mesklinite—whose weight even at Mesklin’s pole is little over three hundred. It is a great deal even for some eight square feet of caterpillar tread; if Dhrawn’s gravity had not done an equally impressive job of packing its surface materials, the Kwembly and her sister vehicles would probably have sunk to their mattresses before traveling a yard.
In other words, the rocks under the tread were held quite firmly. Nothing the two sailors could do would move one of them at all. There was nothing to use as a lever; their ample supplies of spare rope were useless without pulleys; their unaided muscles were laughably inadequate—a situation still less familiar to Mesklinites than to races whose mechanical revolution lay a few centuries in the past.
The approaching ice, however, was a stimulus to thought. It could also have been a stimulus to panic, but neither of the sailors w
as prone to that form of disintegration. Again, it was Beetchermarlf who led.
“Tak, get out from under. We can move those pebbles. Get forward; they’re going to go the other way.” The youngster was climbing the truck as he spoke, and Takoorch grasped the idea at once. He vanished beyond the next-forward truck without a word. Beetchermarlf stretched out along the main body of the drive unit, between the treads. In this foot-wide space, beneath and in front of him, was the recess which held the power converter. This was a rectangular object about the same size as the communicators, with ring-tipped control rods projecting from its surface and guide loops equipped with tiny pulleys at the edges. Lines for remote handling from the bridge were threaded through some of the guides and attached to the rings, but the helmsman ignored them. He could see little, since the lights were still on the bottom several feet away and the top of the truck was in shadow, but he did not need sight. Even clad in an airsuit he could handle these levers by touch.
Carefully he eased the master reactor control to the “operate” position, and then even more gingerly started the motors forward. They responded properly; the treads on either side of him moved forward, and a clattering of small, hard objects against each other became audible for a moment. Then this ceased, and the treads began to race. Beetchermarlf instantly cut off the power, and crawled off the truck to see what had happened.
The plan had worked, just as a computer program with a logic error works—there is an answer forthcoming, but not the one desired. As the helmsman had planned, the treads had scuffed the rocks under them backward; but he had forgotten the effect of the pneumatic mattress above. The truck had settled under its own weight and the downward thrust of the gas pressure until the chassis between the treads had met the bottom. Looking up, Beetchermarlf could see the bulge in the mattress where the entire drive unit had been let down some four inches.
Takoorch appeared from his shelter and looked the situation over, but said nothing. There was nothing useful to say.
Neither of them could guess how much more give there was to the mattress, and how much further the truck would have to be let down before it would really hang free, though, of course, they knew the details of the Kwembly’s construction. The mattress was not a single gas bag but was divided into thirty separate cells, having two trucks in tandem attached to each. The helmsmen knew the details of the attachment, of course—both had just spent many hours repairing the assemblies—but even the recent display of the Kwembly’s underside with the weight of nearly all the trucks left them very doubtful about how far any one of them could extend by itself.
“Well, back to the stone lugging,” remarked Takoorch as he worked his nippers under a pebble. “Maybe these have been jarred loose now; but it’s going to be awkward, getting at them only from the ends.”
“There isn’t enough time for the job. The ice is still growing toward us, and we might have to get the treads a whole body-length deeper before they’d run free. Leave the trucks alone, Tak. We’ll have to try something else.”
“All I ask is to know what.”
Beetchermarlf showed him. Taking a light with him this time, he climbed once more to the top of the truck. Takoorch followed, mystified. The younger sailor reared up against the shaft which formed the swiveling support of the truck, and attacked the mattress with his knife.
“But you can’t hurt the ship!” Takoorch objected.
“We can fix it later. I don’t like it any better than you, and I’d gladly let the air out by the regular bleeder valve if we could only reach it; but we can’t, and if we don’t get the load off this truck very soon we won’t do it at all.” He continued slashing as he spoke.
It was little easier than moving the stones. The mattress fabric was extremely thick and tough; to support the Kwembly it had to hold in a pressure more than a hundred pounds per square inch above the ambient. One of the nuisances of the long trips was the need to pump the cells up manually, or to bleed off excess pressure, when the height of the ground they were traversing changed more than a few feet. At the moment the mattress was a little flat, since no pumping had been done after the run down the river, but the inner pressure was, of course, that much higher.
Again and again Beetchermarlf sliced at the same point on the taut-stretched surface. Each time the blade went just a little deeper. Takoorch, convinced at last of the necessity, joined him; the second blade’s path crossed that of the first, the two flashing alternately in a rhythm almost too fast for a human eye to follow—a human witness, had one been possible, would have expected them to sever each other’s nippers at any moment.
Even so, it took many minutes to get through. The first warning of success was a fine stream of bubbles which spread in all directions up the slope of the bulging gas cell. A few more slashes, and the cross-shaped hole with its inch-long arms was gushing Dhrawnian air in a flood of bubbles that made the work invisible. The prisoners ceased their efforts.
Slowly but visibly the stretched fabric was collapsing. The bubbles fled more slowly across its surface, gathering at the high point near the wall of ice. For a few moments Beetchermarlf thought the fabric would go entirely flat, but the weight of the suspended truck prevented that. The center of the cell—or at least, the point at which the truck was attached; neither of them knew just where the cell boundaries were—was straining downward, but it was now pull instead of push.
“I’ll start the engine again and see what happens,” said Beetchermarlf. “Get forward again for a minute.” Takoorch obeyed. The younger helmsman deliberately wedged a number of pebbles under the front ends of the treads, climbed the truck once more and settled between them. He had kept the light with him this time, not to help him with handling controls but to make it easier to tell how and whether the unit moved. He looked at the point of attachment a few inches above him as he started the engine once more.
The pebbles had provided some traction; the fabric wrinkled and the swivel tilted slightly as the truck strained forward. An upper socket, inaccessible inside the cell, into which the shaft telescoped prevented the tilt from exceeding a few degrees—the trucks, of course, could not be allowed to touch each other—but the strain could be seen. As the motion reached its limit the tracks continued moving, but this time they did not race free. Sound and tactile vibrations both indicated that they were slipping on the pebbles, and after a few seconds the feel of swirling, eddying water became perceptible against Beetchermarlf’s airsuit. He started to climb down from the truck, and was nearly swept under one of the treads as he shifted grips; he barely stopped the motor in time with a hasty snatch at the control. He needed several seconds to regain his composure after that; even his resilient physique could hardly have survived being worked through the space between treads and rocks. At the very least, his airsuit would have been ruined.
Then he took time to trace very carefully the control cords leading from the reactor to the upper guides along the bottom of the mattress, following them by eye to the point above the next truck forward where he could reach them. A few seconds later he was on top of the other truck, starting the motor up again from a safe distance and mentally kicking himself for not having done it that way from the beginning.
Takoorch reappeared beside him and remarked, “Well, we’ll soon know whether stirring water up does any warming.”
“It will,” replied Beetchermarlf. “Besides, the treads are rubbing against the stones on the bottom instead of kicking them out of the way this time. Whether or not you believe that stirring makes heat, you certainly know that friction does. Watch the ice, or tell me if the neighborhood is getting too hot. I’m at the lowest power setting, but that’s still a lot of energy.”
Takoorch rather pessimistically went over to a point where the cairn should be visible if it were ever freed of ice, and settled himself to wait. The currents weren’t too bad here, though he could feel them tugging at his not-too-well-ballasted body. He anchored himself to a couple of medium sized rocks and stopped worrying
about being washed under the treads.
He did not really see how merely stirring water up could heat anything, but Beetchermarlf’s point about friction was comforting. Also, while he would not have admitted it in so many words, he tended to give more weight to the younger sailor’s opinion than to his own, and he fully expected to see the ice yielding very shortly.
He was not disappointed; within five minutes he suspected that more of the stony bottom was visible between him and the barrier. In ten he was sure, and a hoot of glee apprised Beetchermarlf of the fact. The latter took the risk of leaving the control lines untended to come to see for himself, and agreed. The ice was retreating. Immediately he began to plan.
“All right, Tak. Let’s get the other units going as fast as they melt free and we can get at their controls. We should be able to melt the Kwembly loose from this thing, besides getting ourselves out from under.”
Takoorch asked a question.
“Are you going to puncture the cells under all the powered units? That will let the air out of a third of the mattress.”
Beetchermarlf was taken slightly aback.
“I’d forgotten that. No—well, we could patch them all—but—no, that’s not so good. Let’s sfee. When we get another power unit clear we can mount it on the other truck that’s on this cell we’ve drained already; that will give us twice as much heat. After that I don’t know. We could see about digging under the others—no, that didn’t work so well—I don’t know. Well, we can set one more driver going. Maybe that will be enough.”
“We can hope,” said Takoorch dubiously. The youngster’s uncertainty had rather disappointed him, and he wasn’t too impressed with the toned-down substitute for a plan; but he had nothing better himself to offer. “What do I do first?” he asked.
“I’d better go back and stand by those ropes, though I suppose everything’s safe enough,” replied Beetchermarlf indirectly. “Why don’t you keep checking around the edges of the ice, and get hold of another converter as soon as one is unfrozen? We can put it into that truck”—he indicated the other one attached to the deflated cell—“and start it up as soon as possible. All right?”
