Hidden Variables

by Charles Sheffield

  "Why inertia-less, Jeanie?" said McAndrew after a few minutes.

  Maybe he hadn't been listening after all. "So we can use high accelerations. So we can get people to go at the same speeds as the unmanned probes. They'd be flattened at fifty gee, you know that. We need an inertia-less drive so that we can stand that acceleration without being squashed to a mush."

  "But that's not the same thing at all. I told you that a drive with no inertia isn't possible—and it isn't. What you're asking for, now, it seems to me that we should be able . . ."

  His voice drifted off to nothing, he stood up, and without another word he left the cabin. I wondered what I'd started.

  If that was the beginning of the McAndrew drive—as I think it was—then, yes, I was there at the very beginning.

  * * *

  So far as I could tell, it wasn't only the beginning. It was also the end. Mac didn't talk about the subject again on our way in to Luna rendezvous, even though I tried to nudge him a couple of times. He was always the same, he didn't like to talk about his ideas when they were "half-cooked," as he called it.

  When we got to Luna, McAndrew went off back to the Institute, and I took a cargo out to Cybele. End of story, and it gradually faded from my thoughts, until the time came, seven months later, for the next run to Titan.

  For the first time in five years, McAndrew didn't make the trip. He didn't call me, but I got a brief message that he was busy with an off-Earth project, and wouldn't be free for several months. I wondered, not too seriously, if Mac's absence could be connected with inertia-less spaceships, and then went on with the cargo to Titan.

  That was the trip where some lunatic in the United Space Federation's upper bureaucracy decided that Titan was overdue for some favorable publicity, as a thriving colony where culture would be welcomed. Fine. They decided to combine culture and nostalgia, and hold on Titan a full-scale, old-fashioned Miss & Mister Universe competition. It apparently never occurred to the organizers—who must have had minds that could not see in straight lines, let alone around corners—that the participants were bound to take the thing seriously once it was started. Beauty is not something that good-looking people are willing to take lightly. I had the whole Assembly filled with gorgeous, jealous contestants, screaming managers, horny and ever-hopeful newshounds from every media outlet in the System, and any number of vengeful and vigilant wives, lovers and mistresses of both sexes. On one of my earlier runs I took a circus and zoo out to Titan, but that was nothing compared with this trip. Thank Heaven that the ship is computer-controlled. All my time was spent in keeping some of the passengers together and the rest apart.

  It also hadn't occurred to the organizers, back on Earth, that a good part of the Titan colony is the prison. When I saw the first interaction of the prisoners and the contestants I realized that the trip out to Titan had been a picnic compared with what was about to follow. I chickened out and went back to the ship until it was all over.

  I couldn't really escape, though. When it was all over, when the winners had finally been chosen, when the protests and the counter-protests had all been lodged, when the battered remnants of the more persistent prisoners had been carried back to custody, when mayhem was stilled, and when the colonists of Titan must have felt that they had enjoyed as much of Inner System culture as they could stand for another twenty or thirty years, after all that it was my job to get the group back on board again, and home to Earth without further violence. The contestants hated their managers, the managers hated the judges, the judges hated the news media, and everyone hated the winners. It seemed to me that McAndrew may have had advance information about the trip, and drawn a correct conclusion.

  I would like to have skipped it myself. Since I was stuck with it, I separated the Sections of the Assembly as much as I could, put everything onto automatic, and devoted myself to consoling one of the losers, a smooth-skinned armful from one of the larger asteroids.

  We finally got there. On that day of rejoicing, the whole ghastly gaggle connected with the contest left the Assembly, I said a lingering farewell to my friend from Vesta—a most inappropriate origin for that particular contestant—and settled back for a needed rest.

  It lasted for about eight hours. As soon as I called into the Com Center for news and messages, I got a terse summons on the com display: GO TO PENROSE INSTITUTE, L-4 STATION. MACAVITY.

  Not an alarming message, on the face of it, but it worried me. It was from McAndrew, and I doubt if three people knew that I had given him that nickname when I found he was a specialist on theories of gravity ("Old Possum's Book Of Practical Cats" didn't seem to be widely read among Mac's colleagues).

  Why hadn't he called me directly, instead of sending a com-link message? The fact that we were back from Titan would have been widely reported. I sat down at the terminal and placed a link to the Institute, person-to-person to McAndrew.

  I didn't feel any better when the call went through. Instead of Mac's familiar face, I was looking at the coal-black complexion of Professor Limperis, the head of the Institute. He nodded at me seriously.

  "Captain Roker, your timing is impressive. If we had received no response to Professor McAndrew's coded message in the next eight hours, we would have proceeded without you. Can you help?"

  He hesitated, seeing my confused expression. "Did your message tell you the background of the problem?"

  "Dr. Limperis, all I've had so far is half a dozen words—to go to the L-4 branch of the Institute. I can do that easily enough, but I have no idea what the problem is, or what use I could possibly be on it. Where's Mac?"

  "I wish to God I could answer that." He sat silent for a moment, chewing on his lower lip, then shrugged. "Professor McAndrew insisted that we send for you—left a message specifically for you. He told us that you were the stimulus for beginning the whole thing."

  "What whole thing?"

  He looked at me in even greater surprise. "Why, the high acceleration drive—the balanced drive that McAndrew has been developing for the past year. McAndrew has disappeared testing the prototype. Can you come at once to the Institute?"

  The trip out to the Institute, creeping along in the Space Tug from Luna Station, was one of the low points of my life. There was no particular logic to it—after all, I'd done nothing wrong. But I couldn't get rid of the feeling that I'd wasted a critical eight hours after the passengers had left the Assembly. If I hadn't been obsessed with sex on the trip back, maybe I would have gone straight to the com-link instead of taking a sleep break. And maybe then I would have been on my way that much earlier, and that would have been the difference between saving Mac and failing to save him . . .

  You can see how my mind was running. Without any real facts, you can make bears out of bushes just as well in space as you can on Earth. All I had been told by Limperis was that McAndrew had left a week earlier on a test of the prototype of a new ship. If he was not back within a hundred and fifty hours, he had left that terse coded message for me, and instructions—orders might be a better word—to take me along on any attempted search for him.

  Dr. Limperis had been very apologetic about it. "I'm only quoting Professor McAndrew, you understand. He said that he didn't want any rescue party setting out in the Dotterel if you weren't part of it. He said"—Limperis coughed uncomfortably—"we had a real need for your common sense and natural cowardice. We'll be waiting for you here as soon as you can arrange passage. The least we can do for Professor McAndrew in the circumstances is to honor his wishes on this."

  I couldn't decide if I was being complimented or not. As L-4 Station crept into view on the forward screen, I peered at it on highest magnification, trying to see what the rescue ship looked like. I could see the bulk of the Institute structure but no sign of anything that ought to be a ship. I had visions of a sort of super-Assembly, a huge cluster of electromagnetically linked spheres. All I could see were living quarters and docking facilities, and, as we came in to dock, a peculiar construction like a flat, s
hiny plate with a long thin spike protruding from the center. It looked nothing like any USF ship, passenger or cargo.

  Limperis may have spent his whole life in pure research, but he knew how to organize for emergency action. There were just five people in our meeting inside the Institute. I had never met them in person, but they were all familiar to me through McAndrew's descriptions, and from media coverage. Limperis himself had made a life study of high-density matter. He knew every kernel below lunar mass out to a couple of hundred astronomical units—many of them he had visited, and a few of the small ones he had shunted back with him to the Inner System, to use as power supplies.

  Siclaro was the specialist in kernel energy extraction. The Kerr-Newman black holes were well-understood theoretically, but efficient use of them was still a matter for experts. When the USF wanted to know the best way to draw off power, for drives or for general use, Siclaro was usually called in. His name on a recommendation was like a stamp of approval that few would think to question.

  With Gowers there as an expert in multiple kernel arrays, Macedo as the System authority in electromagnetic coupling, and Wenig the master of compressed matter stability, the combined intellect in that one room in the Institute was overpowering. I looked at the three men and two women who had just been introduced to me, and felt like a gorilla in a ballet. I might make the right movements, but I wouldn't know what was going on.

  "Look, Dr. Limperis," I said, "I know what Professor McAndrew wants, but I'm not sure he's right." Might as well hit them with my worries at the beginning, and not waste everybody's time. "I can run a ship, sure—it's not hard. But I've no idea how to run something with a McAndrew drive on it. Any one of you could probably do a better job."

  Limperis was looking apologetic again. "Yes and no, Captain Roker. We could all handle the ship, any one of us. The concepts behind it are simple—a hundred and fifty years old. And the engineering has been kept simple, too, since we are dealing with a prototype."

  "Then what do you want me for?" I won't say I was angry, but I was uneasy and unhappy, and there's a fine line between irritation and discomfort.

  "Dr. Wenig will drive the Dotterel, he has handled it before in an earlier test. Actually, he handled the Merganser, the ship that Dr. McAndrew has disappeared in, but the Dotterel has identical design and equipment. Controlling the ship is easy—if everything behaves as we expected. If something goes wrong—and something must have gone wrong, or McAndrew would be back before this—then neither Dr. Wenig, nor any of the rest of us, has the experience that will be needed. We want you to tell Dr. Wenig what not to do. You've been through dangerous times before." He looked pleading. "Will you observe our actions, and use your experience to advise us?"

  Uninvited, I flopped down into a seat and stared at the five of them. "You want me to be a bloody canary!"

  "A canary?" Wenig was small and slight, with a luxuriant black mustache. He had a strong accent, and I think he was suspecting himself of a translation error.

  "Right. Back when people used to go down deep in the earth to mine coal, they used to take a canary along with them. It was more sensitive to poisonous gases than they were. When it fell off the perch, they knew it was time to leave. The rest of you will fly the ship, and watch for me to fall off my seat."

  They looked at each other, and finally Limperis nodded. "We need a canary, Captain Roker. None of us here knows how to sing at the right time. Will you do it?"

  I had no choice. Not after Mac's personal cry for help. I could see one problem—I'd be telling them everything they did was dangerous. When you have a new piece of technology, it is risky, whatever you do with it.

  "You mean you'll let me overrule all the rest of you, if I don't feel comfortable?"

  "We would." Limperis was quite firm about it. "But the question will not arise. The Merganser and the Dotterel are both two-person ships. We saw no point in making them larger. Dr. Wenig will fly the Dotterel, and you will be the only other person aboard. It just takes one person to handle the controls. You will be there to advise of hidden problems."

  I stood up. "Let's go. I don't think I can see danger any better than you can, but I may be wrong. If Mac's on his own out there, wherever he is, we'd better get moving. I'm ready when you are, Dr. Wenig."

  Nobody moved. Maybe McAndrew and Limperis were right about my antennae, because at that moment I had a premonition of new problems. I looked around at the uncomfortable faces.

  "Professor McAndrew isn't actually alone on the Merganser." It was Emma Gowers who spoke first. "He has a passenger with him on the ship."

  "Someone from the Institute?"

  She shook her head. "Nina Velez is with him."

  "Nina Velez? You don't mean President Velez's daughter—the one with AG News?"

  She nodded. "The same."

  I sat down again in my chair. Hard. Maybe the Body-beautiful run to Titan had been an easier trip than I had realized.

  * * *

  Wenig may have come to piloting second-hand, but he certainly knew his ship. He wanted me to know it, too. Before we left the Institute, we'd done the lot—schematics, models, components, power, life support, mechanicals, electricals, electronics, controls, and backups.

  When the ship was explained to me, I decided that McAndrew didn't really see round corners when he thought. It was just that things were obvious to him before they were explained, and obvious to other people afterwards. I had been saying "inertia-less" to Mac, and he had been just as often saying "impossible." But we hadn't been communicating very well. All I wanted was a drive that would let us accelerate at multiple gee without flattening the passengers. To McAndrew, that was a simple requirement, one that he could easily satisfy—but there was no question of doing away with inertia, of passengers or ship.

  "Take it back to basics," said Wenig, when he was showing me how the Dotterel worked. "Remember the equivalence principle? That's at the heart of it. There is no way of distinguishing an accelerated motion from a gravitational field force, right?"

  I had no trouble with that. It was freshman physics. "Sure. You'd be flattened just as well in a really high gravity field as you would in a ship accelerating at fifty gee. But where does it get you?"

  "Imagine that you were standing on something with a hefty gravity field—Jupiter, say. You'd experience a downward force of about two and a half gee. Now suppose that somebody could accelerate Jupiter away from you, downwards, at two and a half gee. You'd fall towards it, but you'd never reach it—it would be accelerating at the same rate as you are. And you'd feel as though you were in free fall, but so far as the rest of the Universe is concerned you'd be accelerating at two and a half gee, same as Jupiter. That's what the equivalence principle is telling us, that acceleration and gravity can cancel out, if they're set up to be equal and opposite."

  As soon as you got used to Wenig's accent, he was easy to follow—I doubt if anybody could get into the Institute unless he was more than bright enough to explain concepts in easy terms.

  I nodded. "I can understand that easily enough. But you've just replaced one problem with a worse one. You can't find any drive in the Universe that could accelerate Jupiter at two and a half gee."

  "We cannot—not yet, at any rate. Luckily, we don't need to use Jupiter. We can do it with something a lot smaller, and a lot closer. Let's look at the Dotterel and the Merganser. At McAndrew's request I designed the mass element for both of them."

  He went across to the window that looked out from the inside of the Institute to raw space. The Dotterel was floating about ten kilometers away, close enough to see the main components.

  "See the plate on the bottom? It's a hundred meter diameter disk of compressed matter, electromagnetically stabilized and one meter thick. Density's about eleven hundred and seventy tons per cubic centimeter—pretty high, but nothing near as high as we've worked with here at the Institute. Less than you get in anything but the top couple of centimeters of a neutron star, and nowhere near approachin
g kernel densities. Now, if you were sitting right at the center of that disk, you'd experience a gravitational acceleration of fifty gee pulling you down to the disk. Tidal forces on you would be one gee per meter—not enough to trouble you. If you stayed on the axis of the disk, and moved away from it, you'd feel an attractive force of one gee when you were two hundred and forty-six meters from the center of the disk. See the column growing out from the disk? It's four meters across and two hundred and fifty meters long."

  I looked at it through the scope. The long central spike seemed to be completely featureless, a slim column of grey metal.

  "What's inside it?"

  "Mostly nothing." Wenig picked up a model of the Dotterel and cracked it open lengthwise, so that I could see the interior structure. "When the drives are off, the living-capsule is out here at the far end, two hundred and fifty meters from the dense disk. Gravity feels like one gee, toward the center of the disk. See the drives here, on the disk itself? They accelerate the whole thing away from the center column, so the disk stays flat and perpendicular to the motion. The bigger the acceleration that the drives produce, the closer to the disk we move the living-capsule up the central column here. We keep it so the total force in the capsule, gravity less acceleration, is always one gee, toward the disk."

  He slid the capsule along an electromechanical ladder closer to the disk. "It's easy to compute the right distance for any acceleration—the computer has it built-in, but you could do it by hand in a few minutes. When the drives are accelerating the whole thing at fourteen gee, the capsule is held a little less than fifty meters from the disk. I've been on a test run in the Merganser where we got up to almost twenty gee. Professor McAndrew intended to take it up to higher accelerations on this test. To accelerate at thirty-two gee, the capsule must be about twenty meters from the disk to keep effective gravity inside to one gee. The plan was to take the system all the way up to design maximum—fifty gee thrust acceleration, so that the passengers in the capsule would be right up against the disk, and feel as though they were in free fall. Gravity and thrust accelerations will exactly balance."