Raindrop

by Hal Clement

  This worried him, since Silbert had become firmly attached to the notion that the Raindrop plan was an essential step to keeping the human race fed, and he had as good an appetite as anyone.

  He knew, as did any reasonably objective and well-read adult, how barely the advent of fusion power and gene tailoring had bypassed the first critical point in the human population explosion, by making it literally possible to use the entire surface of the planet either for living space or the production of food. As might have been expected, mankind had expanded to fill even that fairly generous limit in a few generations.

  A second critical point was now coming up, obviously enough to those willing to face the fact. Most of Earth’s fourteen billion people lived on floating islands of gene-tailored vegetation scattered over the planet’s seas, and the number of these islands was reaching the point where the total sunlight reaching the surface was low enough to threaten collapse of the entire food chain. Theoretically, fusion power was adequate to provide synthetic food for all; but it had been learned the hard way that man’s selfishness could be raised to the violence point almost as easily by a threat to his “right” to eat natural—and tasty—food as by a threat to his “right” to reproduce without limit. As a matter of fact, the people whom Silbert regarded as more civilized tended to react more strongly to the first danger.

  Raindrop had been the proposed answer. As soon as useful, edible life forms could be tailored to live in its environment it was to be broken up into a million or so smaller units which could receive sunlight throughout their bulks, and use these as “farms.”

  But power units, lights, and what looked like prefabricated living quarters sufficient for many families did not fit with the idea of breaking Raindrop up. In fact, they did not fit with any sensible idea at all.

  No one could live on Raindrop, or in it, permanently; there was not enough weight to keep human metabolism balanced. Silbert was very conscious of that factor. He never spent more than a day at a time on his sampling trips, and after each of these he always remained in the normal-weight part of the station for the full number of days specified on the AGT tables.

  It was all very puzzling.

  And as the day wore on, and more and more material was taken from the low-weight storage section of the station and netted together for the trip to Raindrop, the spaceman grew more puzzled still. He said nothing, however, since he didn’t feel quite ready to question the Weisanens on the subject and it was impossible to speak privately to Bresnahan with all the spacesuit radios on the same frequency.

  All the items moved were, of course, marred with their masses, but Silbert made no great effort to keep track of the total tonnage. It was not necessary, since each cargo net was loaded as nearly as possible to an even one thousand pounds and it was easy enough to count the nets when the job was done. There were twenty-two nets.

  A more ticklish task was installing on each bundle a five hundred pound-second solid-fuel thrust cartridge, which had to be set so that its axis pointed reasonably close to the center of mass of the loaded net and firmly enough fastened to maintain its orientation during firing. It was not advisable to get rid of the orbital speed of the loads by “pushing off” from the station; the latter’s orbit would have been too greatly altered by absorbing the momentum of eleven tons of material. The rockets had to be used.

  Silbert, in loading the nets, had made sure that each was spinning slowly on an axis parallel to that of Raindrop. He had also attached each cartridge at the “equator” of its net. As a result, when the time came to fire it was only necessary to wait beside each load until its rocket was pointing “forward” along the station’s orbit, and touch off the fuel.

  The resulting velocity change did not, in general, exactly offset the orbital speed, but it came close enough for the purpose. The new orbit of each bundle now intersected the surface of Raindrop—a target which was, after all, ten miles in diameter and only half a mile away. It made no great difference if the luggage were scattered along sixty degrees of the satellite’s equatorial zone; moving the bundles to the lock by hand would be no great problem where each one weighed about three and a half ounces.

  With the last net drifting toward the glistening surface of Raindrop, Weisanen turned to the spaceman.

  “What’s the best technique to send us after them? Just jump off?”

  Silbert frowned, though the expression was not obvious through his face plate.

  “The best technique, according to the ACT Safety Tables, is to go back to the rim of the station and spend a couple of days getting our personal chemistry back in balance. We’ve been weightless for nearly ten hours, with only one short break when we ate.”

  Weisanen made a gesture of impatience which was much more visible than Silbert’s frown.

  “Nonsense!” he exclaimed. “People have remained weightless for a couple of weeks at a time without permanent damage.”

  “Without having their bones actually turn to rubber, I grant. I don’t concede there was no more subtle damage done. I’m no biophysicist. I just believe the tables; they were worked out on the basis of knowledge gained the hard way. I admit they have a big safety factor, and if you consider it really necessary I won’t object to staying out for four or five days. But you haven’t given us any idea so far why this should be considered an emergency situation.”

  “Hmmm. So I haven’t. All right, will you stay out long enough to show Brenda and me how to work the locks below, so we can get the stuff inside?”

  “Why—of course—if it’s that important we’ll stay and do the work too. But I didn’t—”

  Silbert fell silent as it dawned on him that Weisanen’s choice of words meant that he had no intention of explaining just yet what the “emergency” was. Both newcomers must have read the spaceman’s mind quite accurately at that point, since even Bresnahan was able to, but neither of them said anything.

  Conversation for the next few minutes consisted entirely of Silbert’s instructions for shoving off in the proper direction to reach Raindrop, and how to walk on its not-quite-zero-gravity, jelly-like surface after they reached it. The trip itself was made without incident.

  Because fast movement on the surface was impossible, several hours were spent collecting the scattered bundles and stacking them by the lock. The material could not be placed inside, as most of it had to be assembled before it could go under water; so for the moment the lesson in lock management was postponed. Weisanen, after some hesitation, agreed to Silbert’s second request that they return to the station for food and rest. He and his wife watched with interest the technique of getting back to it.

  With four people instead of two, the velocity-matching problem might have been worse, but this turned out not to be the case. Silbert wondered whether it were strictly luck, or whether the Weisanens actually had the skill to plan their jumps properly. He was beginning to suspect that both of them had had previous space experience, and both were certainly well-coordinated physical specimens.

  According to the tables which had been guiding Silbert’s life, the party should have remained in the high-weight part of the station for at least eighty hours after their session of zero-gee, but his life was now being run by Weisanen rather than the tables. The group was back on the water twelve hours after leaving it.

  Bresnahan still had his feeling of discomfort, with star-studded emptiness on one side and its reflection on the other, but he was given little time to brood about it.

  The first material to go into the lock consisted of half a dozen yard-wide plastic bubbles of water. Silbert noted with interest that all contained animal life, ranging from barely visible Crustacea to herring-sized fish.

  “So we’re starting animal life here at last,” remarked the spaceman. “I thought it was a major bone of contention whether we ever would.”

  “The question was settled at the first meeting of the new board,” replied Weisanen. “Life forms able to live here—or presumably able to live here—have be
en ready for several years. Please be careful in putting those in the lock—just the odd-numbered ones first, please, first. The evens contain predators, and the others should be given a few hours to scatter before they are turned loose.”

  “Right. Any special techniques for opening? Or just get the bubbles through the second lock and cut them open?”

  “That will do. I assume that a few hours in the currents inside, plus their own swimming abilities, will scatter them through a good part of the drop.”

  “It should. I suppose they’ll tend to stay pretty close to the skin because of the light; I trust they can take a certain amount of hard radiation.”

  “That matter has been considered. There will be some loss, damage, and genetic change, of course, but we think the cultures will gain in spite of that. If they change, it is no great matter. We expect rapid evolution in an environment like this, of course. It’s certainly been happening so far.”

  Bresnahan helped push the proper spheres into the lock at the vacuum end and out of it at the other, and watched with interest as each was punctured with a knife and squeezed to expel the contents.

  “I should have asked about waiting for temperatures to match,” remarked Silbert as the cloud of barely visible, jerkily moving specks spread from the last of the containers, “but it doesn’t seem to be bothering them.”

  “The containers were lying on Raindrop’s surface all night, and the satellite is in radiative equilibrium,” pointed out Bresnahan. “The temperatures shouldn’t be very different anyway. Let’s get back outside and see what’s going on next. Either these water-bugs are all right, or they’re beyond our help.”

  “Right.” Silbert followed the suggestion, and the newly released animals were left to their own devices.

  Outside, another job was under way. The largest single items of cargo had been a set of curved segments of metal, apparently blue-anodized aluminum. In the few minutes that Silbert and Bresnahan had been inside, the Weisanens had sorted these out from the rest of the material and were now fitting them together.

  Each section attached to its neighbor by a set of positiveacting snap fasteners which could be set almost instantly, and within a very few minutes it became evident that they formed a sphere some twenty feet in diameter. A transparent dome of smaller radius was set in one pole, and a cylindrical structure with trap doors in the flat ends marked the other. With the assembly complete, the Weisanens carefully sprayed everything, inside and out, from cylinders which Silbert recognized as containing one of the standard fluorocarbon polymers used for sealing unfindable leaks in space ships.

  Then both Weisanens went inside.

  Either the metallic appearance of the sphere was deceptive or there were antennae concealed in its structure, because orders came through the wall on the suit-radio frequency without noticeable loss. In response to these, Bresnahan and the spaceman began handing the rest of the equipment in through the cylindrical structure, which had now revealed itself as a minute air lock. As each item was received it was snapped down on a spot evidently prepared to receive it, and in less than two hours almost all the loose gear had vanished from the vicinity of Raindrop’s entry lock. The little that was left also found a home as Weisanen emerged once more and fastened it to racks on the sphere’s outer surface, clustered around the air lock.

  The official went back inside, and, at his orders, Silbert and the computerman lifted the whole sphere onto the top of the cylindrical cargo lock of the satellite. Either could have handled the three-pound weight alone, but its shape and size made it awkward to handle and both men felt that it would be inadvisable to roll it.

  “Good. Now open this big hatch and let us settle into the lock chamber,” directed Weisanen. “Then close up, and let in the water.”

  It was the first time Silbert had caught his boss in a slip, and he was disproportionately pleased. The hatch opened outward, and it was necessary to lift the sphere off again before the order could be obeyed.

  Once it was open, the two men had no trouble tossing the big globe into the yawning, nearly dark hole—the sun was just rising locally and did not shine into the chamber—but they had to wait over a minute for Raindrop’s feeble gravity to drag the machine entirely inside. They could not push it any faster, because it was not possible to get a good grip on sphere and lock edge simultaneously; and pushing down on the sphere without good anchorage would have done much more to the pusher than to the sphere.

  However, it was finally possible to close the big trap. After making sure that it was tightly latched—it was seldom used, and Silbert did not trust its mechanism unreservedly—he and Bresnahan entered the lock through the smaller portal.

  “Aren’t there special suits for use inside Raindrop, a lot more comfortable than this space armor?” asked Weisanen.

  “Yes, sir,” replied the spaceman, “though the relative comfort is a matter of opinion. There are only three, and two of them haven’t been used since I came. They’ll need a careful checkout.”

  “All right. Bring them in here, and then let the water into this lock.” Silbert found the suits and handed them to Bresnahan to carry out the first part of the order, while he went to the controls to execute the second.

  “All ready?” he asked.

  “All set. Both lock doors here are shut, and the three of us are inside. Let the flood descend.”

  “Wrong verb,” muttered Silbert to himself.

  He very cautiously cracked the main inner hatch; opening it would have been asking for disaster. Even at a mere quarter atmosphere’s pressure the wall of water would have slammed into the evacuated lock violently enough to tear the outer portal away and eject sphere and occupants at a speed well above Raindrop’s escape value. There was a small Phoenix rocket in the station for emergency use, but Silbert had no wish to create a genuine excuse for using it. Also, since he was in the lock himself, he would probably be in no condition to get or pilot it.

  V

  The water sprayed in violently enough through the narrow opening he permitted, bouncing the sphere against the outer hatch and making a deafening clamor even for the spacesuited trio inside. However, nothing gave way, and in a minute it was safe to open the main hatch completely.

  Silbert did so. Through the clear dome which formed the sphere’s only observation window he could see Weisanen fingering controls inside. Water jets from almost invisible ports in the outer surface came into action, and for the first time it became evident that the sphere was actually a vehicle. It was certainly not built for speed, but showed signs of being one of the most maneuverable ever built.

  After watching for a moment as it worked its way out of the lock, Silbert decided that Weisanen had had little chance to practice handling it. But no catastrophe occurred, and finally the globe was hanging in the greenish void outside the weed-grown bulk of the lock. The spaceman closed the big hatch, emerged through the personnel lock himself, and swam over to the vehicle’s entrance.

  The outer door of the tiny air lock opened manually. Thirty seconds later he was inside the rather crowded sphere removing his helmet—some time during the last few minutes Weisanen had filled the vehicle with air.

  The others had already unhelmeted and were examining the “diving” suits which Bresnahan had brought inside. These were simple enough affairs; plastic form-fitting coveralls with an air-cycler on the chest and an outsized, transparent helmet which permitted far more freedom of head movement than most similar gear. Since there was no buoyance in this virtually weight-free environment, the helmet’s volume did not create the problem it would have on Earth. Silbert was able to explain everything necessary about the equipment in a minute or two.

  Neither of the Weisanens needed to have any point repeated, and if Bresnahan was unsure about anything he failed to admit it.

  “All right.” Raindrop’s owner nodded briskly as the lesson ended. “We seem to be ready. I started us down as soon as Mr. Silbert came aboard, but it will take the best part of an hour to
reach the core. When we get there a regular ecological sampling run will be made. You can do that, Mr. Silbert, using your regular equipment and techniques; the former is aboard, whether you noticed it being loaded or not. Brenda and I will make a physical, and physiographical, examination of the core itself, with a view to finding just what will have to be done to set up living quarters there and where will be the best place to build them.”

  Silbert’s reaction to this remark may have been expected; both Weisanens had been watching him with slight smiles on their faces. He did not disappoint them.

  “Living quarters? That’s ridiculous! There’s no weight to speak of even at Raindrop’s surface, and even less at the core. A person would lose the calcium from his skeleton in a few weeks, and go unbalanced in I don’t know how many other chemical ways—”

  “Fourteen known so far, Mr. Silbert. We know all about that, or as much as anyone does. It was a shame to tease you, but my husband and I couldn’t resist. Also, some of the factors involved are not yet public knowledge, and we have reasons for not wanting them too widely circulated for a while yet.” Brenda Weisanen’s interruption was saved from rudeness by the smile on her face. “I would invite you to sit down to listen, but sitting means nothing here—I’ll get used to that eventually, no doubt.”

  “The fact you just mentioned about people leaching calcium out of their skeletons after a few days or weeks of weightlessness was learned long ago—even before long manned space flights had been made; the information was gained from flotation experiments. Strictly speaking, it is not an effect of weightlessness per se, but a feedback phenomenon involving relative muscular effort—something which might have been predicted, and for all I know may actually have been predicted, from the fact that the ankle bones in a growing child ossify much more rapidly than the wrist bones. A very minor genetic factor is involved; after all, animals as similar to us as dolphins which do spend all their time afloat grow perfectly adequate skeletons.