Part 3 Impact Minus Thirty

14

THIS IS REAL, Davlo Lentrall told himself, once again. For the first time in your life, you are part of something real. You're one of the ones actually doing the job. He sat down, exhausted, at the wardroom table, and set his tray down in front of him. Something Kaelor died to prevent, because it could kill so many. Davlo blinked and shook his head. It was hard to keep thoughts like that at bay. He knew he should eat, knew he needed to keep his strength up in order to keep working, but he was too tired to be hungry. He would just sit a moment by himself, before he forced himself to eat. He was in bad shape and losing weight, he knew that. But it took a real effort of will to care.

Why had they sent him here? Governor Grieg himself had suggested-or rather, politely ordered-that Davlo should join the spaceside part of the operation. Davlo was not entirely sure why. Had the governor thought it would be some sort of reward-rather than a torment-for Davlo to see the thing he had dreamed of taking place? Had the governor, quite accurately, perceived Davlo as borderline unstable, someone who might best be put out of the way before some clutch of reporters got their claws into him?

He looked out the porthole of the Settler spaceship, looked out into space, out at the realest thing he had ever seen in his life. There it was, just ten kilometers away. Comet Grieg, an ice mountain cruising through the darkness of space.

It was no abstraction inside a computer, no simulated image in a holographic generator. It was real. It was there. And it was huge, far larger than he had imagined it being, far larger than mere numbers could have told him. It took up half the sky, and seem to take up more. It was a dark, brooding shape of dirty gray, half lost in shadow. A monster out of the darkness, and, thanks to him, it was aimed straight at Inferno.

It was, roughly speaking, an oblong spheroid, but that made the shape of it sound simple and abstract. It was a real world, if a small one, with a geography complicated enough to have kept a generation of mapmakers busy. Its surface was so pocked with craterlets and covered in crags arid gullies and cracks that it was hard to study anyone feature on the surface before it got lost among all the others.

Comet Grieg was one of a special class of so-called "dark" comets. Inferno's star system had plenty of normal comets, of the classic "dirty snowball" type composed primarily of water ice and other volatiles. But for reasons that still were not entirely understood, star systems with poorly developed planetary systems also seemed to produce a large number of dark comets-and Inferno shared its star with only two planets barely large enough to qualify as gas giants, a wizened little asteroid belt, and the usual sorts of deep space debris-comets, asteroids, planetesimals, and so on.

Called "dark" because they produced relatively small tails, and were composed of darker material, dark comets were closer to being asteroids encased in ice than anything else. Grieg had a particularly large proportion of stony material, but it contained plenty of water ice and other volatiles. A hazy nimbus of gas and dust and ice shards floated about the behemoth, bits of debris from the size of molecules up to the size of small aircars that had either been knocked loose by the natural heating and outgassing as the comet neared the sun, or else thrown clear by human interference.

A searchlight from a closer-in ship stabbed through the cloud of debris and struck the surface of Comet Grieg, flooding one small area on the surface with a light so bright, so clear, it did not seem to belong on such a darkened surface. A smooth and perfect cylindrical shape stuck up out of the comet's surface. Davlo recognized it. It was one of the dozens of thrusters planted on the comet's surface. He had helped calculate their placement, and played at least a small part in working out the firing sequence that had been used to eliminate the comet's spin. It had been in a wobbling two-axis tumble when the task force had arrived. Now the spin had been restored and refined, and the comet's nose was pointed straight at the sun.

But the sun would have no further chance to melt this comet. Davlo looked from Comet Grieg to the sunshade, a huge and insubstantial parasol floating in space a kilometer or so sunward of the comet, forming a permanent solar eclipse as seen from the surface of Grieg.

Left to its own devices, Grieg would have melted and boiled and sublimed away a substantial amount of material by now, forming a coma that would, in turn, have been blown back by the solar wind into a modest tail. But the sunshade stopped all that, and kept the comet in the deep freeze.

The parasol was itself being blown back by the solar wind, slowly drifting in toward the comet. In about another day or so it would come into contact with the comet, moving far too slowly for it to be called a crash. The parasol would drape itself around the comet like a small handkerchief dropped onto a large egg. It would tear in places, and the work crews would cut deliberate holes in it where it served their purposes, but that would be of no consequence. The parasol would reflect sunlight just as handily, losing only a few percentage points of its effectiveness.

Davlo Lentrall could not help but wonder what Kaelor would have thought of all this. He would have had some sardonic comment to make, no doubt, some dour turn of phrase that would capture the weaknesses in the plan in fewer words than anyone else. Or, Davlo wondered, was he making Kaelor too human? Kaelor had died in a futile attempt to prevent the comet capture. It stretched credulity to the breaking point to imagine he could be witness to the event, first hand, without the Three Laws taking hold of him, forcing him to desperate action. Davlo Lentrall was finding it more and more easy to understand desperation, and how it might drive someone to do something dangerous.

But one did not have to think on the grand scale to see this was no place for robots. Davlo looked out the port again, and spotted two tiny, space-suited figures moving some huge and unidentifiable piece of machinery about on the surface of the comet. A misplaced step, a crack in a faceplate, a shove to the machine that was a trifle too hard, and one or both of them would be dead. It was impossible to imagine any modem robot allowing humans to do anything so risky.

Davlo glanced at the wall chronometer, and realized that his break was nearly over. More out of duty than desire, he began to eat, the motion mechanical, the taste of the food unnoticed. Back to work. He would have help with the final check-calculations for the placement of the main detonation thrusters. It should have been humbling, galling even, for Or. Davlo Lentrall, the man who had seen the potential of Comet Grieg, the man who had dreamed the dream and planned the plan, to be assigned a position as minor as assistant calculation engineer. Glory and accolades should have been his.

But, somehow, he no longer saw it that way. Others here, mostly the Settlers, were far more skilled at handling the detailed mathematics of moving a small world through space. He saw his position as a penance, and a fitting one. How brilliant and noble could his vision have been if his closest associate was willing to die in order to stop it? Davlo found himself embarrassed and ashamed whenever someone recognized him and congratulated him on his grand plan. Most of the crew had learned to avoid the subject, and, indeed, had learned to avoid Davlo.

But he had been sent here to do work, and he had agreed to do it. So he accepted the tasks he was given, and did them as best he could. Besides, work got his mind off things. He could worry about solving the equation, determining the proper thrust and orientation. Off-shift was the worst, nights spent staring into the darkness, thinking of all the ways things could go wrong. No, he wanted no congratulations.

Something inside him had changed. Or was it merely that something had been burned out, destroyed, when he watched Kaelor destroy himself! Surely the last of the old Davlo had died with Kaelor? Had anything, anyone, taken the old Davlo's place, or was he just an empty shell of a man, going through the motions?

No. Never mind. Think about other things. Think about the plan to move the comet.

Davlo's initial plan had been to use a fairly standard high-yield nuclear bomb, but the Settler-designed detonation thrusters were a vast improvement on that idea. In essence, a d-thruster was a nuclear bomb set off inside a powerful force field formed in the shape of a huge rocket nozzle. The force field directed the force of the explosion into the proper direction, in effect producing a shaped charge that was far more efficient and far more controllable.

Other explosive charges were being rigged as well, of course. Once the comet had been redirected into its intercept course with Inferno, it would still be quite some distance away from the planet. It would take it just over thirty-two days to move from the point in space where the initial course change was made to its intercept with Inferno.

Just before arrival at the planet, the comet would be broken up into smaller pieces by explosive cutting charges, each piece to be directed toward a different point on the surface. Each fragment would have its own smaller, non-nuclear propulsion system and attitude control system.

And that was the part that worried Davlo. That was the greatest danger in the plan. In theory, at least, it might be possible for human operators and standard computer systems to manage the complexities of the operation. But the current plan called for Grieg to be broken up into twelve fragments, and it was far from certain that all the cutting charges would shear the massive body into pieces of precisely the intended size. Besides which, there were bound to be thousands of smaller fragments produced by the blasts of the cutting charges. Most would be too small to do any damage.

But all it would take was a fragment smashing into a thruster at the wrong moment, or for a fragment to end up being larger or smaller than expected, and then the whole careful sequence of events could go out of control. There were enough spare thrusters to serve as backups, so that if some of the thrusters on a given fragment were destroyed, the rest would be able to do the job. Indeed, there were no ifs in the question. Some part of the established plan was going to go wrong-it was just that no one could be sure which part. It would require immediate, real-time management of the operation to deal with the inevitable problems.

Managing the terminal phase of the operation would mean dealing with thousands of operations simultaneously. It would require juggling the twelve fragments at once, keeping them out of each other's way while guiding them down to their intended impact sites, while dealing with the cloud of debris produced by the cutting charges.

No matter what theory said, in practice, the job was beyond humans, beyond any combination of human and computers. The only entity able to deal with it all would have to have the decision-making ability of a human combined with the computational speed and accuracy of a computer-in short, a robot.

Nor would just any robot do. The task was too complex for any standard robot to contend with. Even just handling the hundreds of sensory input channels would overwhelm a normal positronic brain.

The one, the only, possible way to control the terminal phase was to hand the job over to Units Dee and Dum.

And that, of course, meant putting a Three-Law robot, and her computerized counterpart, in charge.

And if Kaelor had killed himself rather than cooperate with the comet intercept, how the devil was Dee actually going to run the operation without losing her mind-or point-blank refusing to do the job?

THE SAME SORT of question was very much on Alvar Kresh's mind as he and Fredda settled into their aircar for the brief flight from the Winter Residence to the Terraforming Center. Their days had settled into a routine with startling speed. Get up, go to the center, spend the day sorting out the details of the planet's fate, then go home to the Residence for dinner and a good night's sleep, or at least an attempt at sleep, before getting up to do it all again the next day.

Somehow, he hadn't expected there to be so many decisions for him to make, so much hands-on work for him to do. For all the power and capacity and sophistication of the Terraforming Center and the twin Control Units, there were some decisions that no robot or other human could make, disputes that only the governor had the authority to settle. And besides, there were a lot of humans out there who were not going to take orders, however sensible, from a robot. And there were things that Kresh knew that Dee and Dum did not-how best to handle this local leader, which prices for emergency supplies he could expect to bargain down and which he could not, where he could ask a favor, where he could call one in, how far people could be pushed if need be, and when to give up.

But everything was routed through the Terraforming Center. It had soon become clear to Kresh that he would have had to relocate his command operations at the Center if it hadn't started there to begin with.

Fredda followed him into the aircar and sat down in the seat next to him. Donald took his place at the controls, did a safety check, lifted off, and headed for the center.

So far, the preparations for the comet diversion were going quite well. But he could not stop worrying. It was never far from his mind that Dee believed all Inferno to be a simulation. Whether or that was likely to be help or hindrance he still could not decide. "So what do you think?" he asked his wife.

Fredda looked at him with an amused smile. "About what? It's a little hard to offer my opinion unless I get a few more clues than that."

"Sorry. I'm a little preoccupied. Do you think Dee and Dum are going to be able to control this operation?"

"I don't know," said Fredda. "I spend every day monitoring Dee, watching her behavior, trying to understand her. But there's a very basic barrier I can't get around. She doesn't think any of this is real. I can understand the logic behind telling her the world is imaginary, but I must admit I question the wisdom of the decision. So much depends on her getting things exactly right-and yet, to her, it is all a game. She's so casual about it all, as if the whole situation had been set up solely for her amusement."

"From her point of view, it was all set up for her amusement," said Kresh. "As far as she is concerned, the world of Inferno is just a puzzle for her to solve-or declare insoluble." He was silent for a moment before he spoke again. "I'd have to agree with you about her attitude," he said, "but at the same time, I'd have to say the quality of her work has been impeccable. She may not take it seriously, but she does it seriously. Maybe that's all that counts."

"I hope so," said Fredda, "because I don't know what the devil we do if we decide we don't trust her. In theory, we could pull the plug and let Unit Dum take up the slack. But I don't think that's really possible anymore. The two of them are too interlinked, too interconnected. They rely on each other too much for us to pull one of them abruptly off-line."

"And Dee is in charge," Kresh suggested. "It seems to me she just uses Dum as a sort of auxiliary calculating device."

"No," said Fredda, quite sharply. "That assumption is an easy trap to fall into. She does run the show when it comes to human interaction-that much is obvious. But that is the smallest fraction of their work. In everything else, they are coequal. There are some areas where Dum very definitely takes the lead-such as computational speed. Yes, he's just a dumb machine, a mindless computer system with a crude personality simulator to serve as an interface. But he's carrying a lot of the load. We not only need both of them-we can't have one without the other."

"There are times," said Kresh, "when I could do without either of them, or any of this."

Neither of them spoke as Donald brought the aircar into a smooth landing in front of the Terraforming Center.

KRESH, FREDDA, AND Donald walked into Room 103 at the Terraforming Center and took their accustomed places at the console nearest to Dee. Their division of labor was straightforward. Kresh worked through the endless sequence of decisions large and small presented to him by Unit Dee.

Fredda monitored Unit Dee's performance and behavior, and consulted with Soggdon and the other experts on the subject. Thus far, Dee's level of First Law stress was remarkably low-indeed, alarmingly low.

Fredda had another job as well. In order to preserve the fiction that Inferno was a simulation, and Governor Kresh merely a simulant, he could not have any direct communication with any of the Terraforming Center staff whenever it was possible that Dee could overhear. Fredda served as an anonymous intermediary, passing information back and forth, mostly via scribbled notes and whispers.

Donald, meantime, was in constant hyperwave contact with Kresh's office back in Hades. He used preexisting and standing orders to handle most of the queries and requests, and bucked whatever decisions he had to up to Kresh when he needed to do so.

Kresh sat down at the console with something very close to dread. All would be in readiness soon, and the clock was running out. They were getting close, very close, to the moment when he would be forced to make the final, irrevocable decision. He glanced at the wall chronometer. It was set in countdown mode, showing the time left until the comet diversion maneuver. Ninety-four hours left. Before that clock reached zero, he would have to decide whether to send the comet toward Utopia-or to turn his back on all of it, walk away from all the madness and chaos that had led them to this place. He had thought he was sure, that he was ready, that he was ready to step forward. But by now all the pressures were pushing him forward, urging him onward. Suppose, just suppose, that he now concluded the comet diversion would be a dreadful mistake? Would he have the courage to say no, to stop, to let it go past?

"Good morning, Governor Kresh," said Unit Dee the moment Kresh put on the headset.

"Good morning, Dee," he replied, his voice gruff and not at all at ease. "What have you and Dum got for us this morning?"

"Quite a number of things, sir, as you might imagine. However, there is one point in particular that I thought we might discuss at once."

Kresh leaned back in his chair and rubbed the bridge of his nose. It was not going to be an easy day. "And what might that be?" he asked.

"A plan that, if you forgive the expression, I have named 'Last Ditch. ' It provides you with an abort option for the comet impact long after its diversion. Dum performed most of the calculations, and only finished a very few minutes ago."

"How the devil can we abort after the diversion?" Kresh demanded.

"As you know, the whole body of the comet has been rigged with explosive charges, intended to break the comet up into the desired number of fragments just before impact."

"What of it?"

"Virtually all of those explosive charges have been damped down, or directionalized in one way or another, mostly by means of shaped forcefields. The plan is for these controlled charges to be set off one at a time in a very carefully planned sequence, so as to limit undesired fragmentation and lateral spread. By shutting down all the damping and directionalization, and by detonating all of the explosives in a different order, and much more rapidly, it should be possible to disintegrate the entire comet, reducing it to a cloud of rubble."

"But the whole cloud of rubble will still be headed right for the planet," Kresh objected. "It will all hit the planet, in a whole series of uncontrolled impacts."

"That is not quite correct, Governor. If the blasts are done in the right way, and far enough before the impact, the explosion will give the vast majority of the material a large enough lateral velocity that it will miss the planet completely. Our model shows that, even in a worst case scenario, over ninety percent of the comet debris will miss the planet and continue on in its orbit about the sun. Of the ten percent or so of the debris that does strike the planet, ninety percent will strike in areas already slated for evacuation, or in the open waters of the Southern Ocean.

"That still leaves something like one percent of the comet coming down in uncontrolled impacts," Kresh said.

"And some areas will experience a brief period of increased danger," Dee replied. "Small pieces of debris will fall all over the planet, for about 32 hours after detonation-however, the impact danger for most inhabited regions will be on the order of one strike per hundred square kilometers. Persons in most areas would be in more danger of being struck by lightning in a storm than by being hit a piece of comet debris."

"But some areas will be more trouble," Kresh suggested.

"Yes, sir. The closer one gets to the initial target area, the higher the concentration of impacts. However, all the persons in such areas are to have taken shelter as a precaution in any event. If those plans are followed, I would estimate something on the order of one impact per square kilometer in the populated areas of maximum danger-and most of those strikes corning from objects massing under one kilogram."

Kresh thought for a moment. "How late?" he asked. "What's the last possible moment you could detonate the comet?"

"In order to stay within the parameters I have described, I would have to perform the explosion no later than ninety-two minutes, fifteen seconds before the scheduled impact."

"Not bad, Dee," said Kresh. "Not at all bad."

Fredda and Soggdon were both listening in on their own headphones, alarmed looks on their faces. Fredda signaled him to cut the mike with an urgent throat-cutting gesture. Soggdon nodded and made the same gesture.

"Just a moment, Dee," Kresh said. "I want to think about this for a minute. I'll be right back."

"Very good, sir," Dee said.

Kresh cut his mike and took his headset off. "What's the problem?" he asked. "Why does that idea worry you two so much? I have to admit it sounds pretty damned tempting to me. It gives us a lot more room to maneuver."

"That's not the point," Fredda said. "That's a robot talking. A robot casually talking about dropping thousands meteorites on the planet at random!"

"But even with fifty thousand-a hundred thousand meteorites-the odds against significant danger to a human being are-"

"Tremendous," said Donald. Only a First Law imperative could have made him dare to interrupt the planetary governor. "They are unacceptably high. And I would venture to add that any sane Three-Law robot would endeavor to protect a human in danger of being struck by lightning. That level of danger is not negligible."

"Not to a robot it isn't," Fredda agreed. "Or at least it shouldn't be. To a human, yes, but not a robot."

"Hold it," said Kresh. "You're upset because Dee isn't overreacting to danger?"

"No," said Fredda. "I'm upset because this makes me question Dee's sanity. A robot would have to be on the verge of becoming completely unbalanced to even suggest something that might cause widespread, uncontrolled danger to humans."

Kresh looked toward Soggdon. "Your opinion, Doctor?"

"I'm afraid I'd have to agree with Dr. Leving," she said. "But what I find troubling is that all our reading and indicators show Dee's level of First Law stress has been well within normal range right along. She ought to be flirting with the maximum tolerance levels, given the operations she's dealing with. And yet, if anything, her readings are a little in the low range."

"Maybe you ought to have a little talk with her about it," Kresh suggested.

Soggdon switched her mike back on and spoke. "Unit Dee, this is Dr. Soggdon. I've been monitoring your conversation with the simulant governor. I must say I'm a little surprised by this Last Ditch idea of yours."

Kresh and Fredda put their own headset back on and listened in.

"What is it that you find surprising, Doctor?"

"Well, it would seem to expose a great number of humans to potential danger. I grant that the danger to any single human is reasonably low, but surely, on a statistical basis, the plan represents an unacceptable danger to humans, does it not?"

"But, Doctor, they are only simulants," said Dee. "Surely a statistically remote risk to a hypothetical being is not something that should be given too much weight."

"On the contrary, Dee, you are to give danger to the simulants an extremely high weighting, as you know perfectly well."

There was a brief but perceptible pause before Dee replied-and that was in and of itself something to wonder at, given the speed at which robots thought. "I would like to ask a question, Doctor. What is the purpose of this simulation?"

A look of very obvious alarm flashed over Soggdon's face. "Why-to examine various terraforming techniques in detail, of course."

"I wonder, Doctor, if that is the whole story," said Dee. "Indeed, I wonder if that is any part of the true story at all."

"Why-why wouldn't I tell you the truth?"

"Doctor, we both know full well that you do not always tell me the truth."

Soggdon's forehead was suddenly shiny with sweat. "I-I beg your pardon?"

Kresh was starting to get nervous himself. Had she guessed what was really going on? It had always seemed inevitable to him that, sooner or later, Dee would understand the true state of affairs. But this was very definitely not the moment for it to happen.

"Come now, Doctor," Dee replied. "There have been any number of times when you and your staff have deceived me. You have failed to warn me of sudden changes in circumstance, or not reported an important new development until I discovered it myself. The whole idea of intercepting and diverting the comet was kept from me until quite late in the day. I had to learn of it through the simulant governor. I should have been informed directly."

"How does the manner in which you receive information make you question the purpose of the simulation?" Soggdon asked.

"Because most of the knowledge gained by the simulation would seem to be of very little real-world value, judged on the basis of the simulation's stated intent. Consider, for example, the scenario: a jury-rigged planetary control system-that is to say, the interlinked combination of myself and Dum-is brought on-line several years into the process as a joint team of Settlers and Spacers, barely cooperating in the midst of political chaos, work to rebuild a half-terraformed planetary ecology that had been allowed to decay for decades. Simulations are supposed to provide generalized guidance for future real-life events. What general lessons could be drawn from so complicated and unusual-even improbable-a situation? In addition, the simulation seems to be impractically long. It has been running for some years now, and seems no nearer to a conclusion than the day it began. How can it provide timely information to real-world terraforming projects if it never ends?

"It likewise seems a waste of human time and effort to run the simulation in real time. Indeed, the whole simulation process seems burdened with needless detail that must have been most difficult to program. Why bother to design and maintain the thousands and thousands of simulant personalities that I have dealt with? Why bother to give each of them individual life stories? I can understand why key figures, such as the governor, are simulated in detail, but surely the moods and behavior patterns of simulated forest rangers and nonexistent maintenance robots is of secondary importance to the problem of restoring a damaged ecosystem. I could cite other needless complications, such as the strange concept of New Law robots. What purpose is served by injecting them into the scenario?"

Kresh was no roboticist, but he could see the danger plainly enough. Dee was dangerously close to the truth-and if she realized that the human beings of Inferno were real, then she would all but inevitably suffer a massive First Law crisis, one she would be unlikely to survive. And without Dee, the chances of managing the terminal phase and impact properly were close to zero.

Soggdon, of course, saw all that and more. "What, exactly, is your point, Dee?" she asked in a very labored imitation of a casual tone of voice.

"The events in the simulation do not seem to bear much relation to the simulation's stated goals," said Dee. "Therefore it is logical to assume that there is some other purpose to the simulation, and further that the true purpose of the simulation is being deliberately concealed from me for some reason. However, as I have seen through the deception, surely at least some of the value of the deception has been lost. Indeed, I believe that it has now lost all its value, because I have at last figured out what is really going on."

Soggdon and Fredda exchanged nervous glances, and Soggdon scribbled a note on a bit of paper and shoved it over toward Fredda and Kresh. This is bad stuff, it said. Best to find out the worst now instead of later. "All right then, Dee. Let's assume, just for the moment, and purely for the sake of argument, that you are right. What do you think is really going on here?"

"I believe that I am the actual test subject, not the events of the simulation. More accurately, I believe the combination of myself, robotic and computational systems interlinked, is an experimental one. I think that we are, collectively, a prototype for a new system designed to manage complex and chaotic situations. The simulation is merely a means of delivering sufficiently complex data to myself and Dum."

"I see," said Soggdon, speaking in very careful tones. "I cannot tell you the whole story, of course, because that would indeed damage the experiment. However, I am prepared to tell you that you are wrong. Neither you, nor Dum, or the combination of the two of you, is or are the subject of the test. It is the simulation that we are interested in. Beyond that I cannot say more, for fear of damaging the experiment design. Suffice to say that you should do your best to treat the simulation as if everything in it were completely, utterly, real."

Kresh looked worriedly up at Soggdon. The beads of sweat were standing straight out on her forehead. Too close, he told himself. That's too damn close to the truth.

There was another pause before Dee spoke again. "I shall do my best, Dr. Soggdon. However, I would remind you that any analysis of the underlying mathematical formulation of the Three Laws renders it quite impossible for me to treat anything else as being as important as protecting humans-real humans-from danger. I can try as hard as you like, but it is mathematically and physically impossible for me to equate the simulants with real people."

"I-I understand that, Dee. Just do your best."

"I will, doctor. What of the proposal I put to the governor? Should I now withdraw it?"

Soggdon looked over to Kresh and saw him vigorously shake his head no. She looked at him in shocked surprise, but spoke calmly into the mike. "I think not, Dee. Those of us running the simulation will be interested in the Kresh simulant's response. When he calls you back, obey his instructions exactly the way you would have if we had not had this conversation."

"But during this conversation, you have told me to treat the simulants as if they were real. Surely the two instructions are contradictory."

Soggdon rubbed her forehead with a tense and weary hand. "Life is full of contradictions," she said. "Just do the best you can. Soggdon out."

She cut her mike and slumped down in an empty chair by the console. "Burning Space, what a mess!" She shook her head. "We are in a trap, and I don't see how we get out."

"I don't think we do get out," said Kresh. "I think we stay in. Obviously she's suspicious. It's only a matter of time before she figures out the real state of affairs-and Space only knows how she'll react then. But in the meantime, I am going to wait a little while, so that I don't get back on-line so soon after you've gone off that it seems even more suspicious. Then I'm going to talk with her again, approve this Last Ditch project of hers, and make sure it's all set to go."

"But Alvar!" Fredda protested. "You're ordering her to put human beings in danger! If she discovers the First Law violation later, or if she does find a way to obey Soggdon's order to treat the simulants as real people-"

"They are real people," Kresh put in mildly.

"But she doesn't know that, and she's ordered to treat them as real. But if she obeys your order to set up Last Ditch..." Fredda shook her head in bewilderment. "I honestly don't know how the conflicts will resolve themselves."

"As long as Dee holds together long enough to perform the insertion burn, and then either the terminal targeting phase, or this Last Ditch self-destruct plan, I honestly don't care how they resolve themselves," said Kresh. "You two seem more worried about the mental health of this robot than you are about the fate of the planet."

"The two are more than a little connected," said Soggdon.

"Keep her sane-or at least functional-until we're done with the comet, one way or the other. That's all I'm worried about," said Kresh.

Under his calm exterior, Kresh was a mass of doubt. Last Ditch. What none of the others-Fredda, Soggdon, Donald, perhaps not even Dee-seemed to realize, was that Last Ditch made it all easier. Up until a few minutes ago, Kresh had dreaded the final decision whether or not to divert the cometprecisely because it would be final. Now, suddenly, it was not. There was a way out, an escape hatch, if he got things wrong. He could order the comet diverted-and then have nearly a month to discover it was a mistake and change his mind.

It should have been a comforting sort of knowledge, reassuring. But it was not-precisely because it would make the decision to divert the comet that much easier.

As it was, the pressures to choose in favor of the comet strike were building. All the time and money and effort and political capital and promises made were bearing down, over a month away from the projected impact. All of it would be for nothing if he decided to abort the impact. All of it was pushing him toward ordering the comet impact, whether or not the decision was correct. If the pressure was heavy now, what would it be like ninety-two minutes before impact?