“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 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 at even 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 travelling 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 was 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 the 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 helmsman 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 off 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 reach it; but we can’t, 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. One of the nuisances of the long trips was the need to pump the cells up manually, or to bleed off the 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 then 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.