"Heywood," said Tanya, "I'm now prepared to take that message, or whatever it was, much more seriously. I'd be stupid not to after what's happened. But even if there is danger here, we still have to weigh one risk against another. Coupling Leonov and Discovery together, operating Discovery with that huge off-axis load, disconnecting the ships in a matter of minutes so we can fire our engines at the right moment; no responsible captain would take such chances without very good - I'd say overwhelming - reasons. Even now, I don't have such reasons. I've only got the word of ... a ghost. Not very good evidence in a court of law."
"Or a court of inquiry," said Walter Curnow, in an unusually quiet voice, "even if we all backed you up."
"Yes, Walter - I was thinking of that. But if we get home safely, that will justify everything - and if we don't, it hardly matters, does it? Anyway, I'm not going to decide now. As soon as we've reported this, I'm going back to bed. I'll give you my decision in the morning after I've slept on it. Heywood, Sasha, will you come up to the bridge with me? We have to wake up Mission Control, before you go back on watch."
The night had not yet finished with its surprises. Somewhere around the orbit of Mars, Tanya's brief report passed a message going in the opposite direction.
Betty Fernandez had talked at last, Both the CIA and the National Security Agency were furious; their combined blandishments, appeals to patriotism, and veiled threats had failed completely - yet the producer of a sleazy gossip network had succeeded, thereby making himself immortal in the annals of Videodom.
It was half luck, half inspiration. The news director of 'Hello, Earth!' had suddenly realized that one of his staff bore a striking likeness to David Bowman; a clever makeup artist had made it perfect. José Fernandez could have told the young man that he was taking a terrible risk, but he had the good fortune that often favours the brave. Once he had got his foot inside the door, Betty had capitulated. By the time she had - quite gently - thrown him out, he had obtained essentially the whole story. And to do him credit, he had presented it with a lack of leering cynicism quite uncharacteristic of his network. It got him that year's Pulitzer.
"I wish," Floyd said rather wearily to Sasha, "she'd talked earlier. It would have saved me a lot of trouble. Anyway, that settles the argument. Tanya can't possibly have any doubts now. But we'll leave it until she wakes up - don't you agree?"
"Of course - it's not urgent, even though it's certainly important. And she'll need the sleep. I have a feeling none of us will get much from now on."
I'm sure you're right, thought Floyd. He felt very tired, but even if he had not been on duty he would have found it impossible to sleep. His mind was too active, analysing the events of this extraordinary night, trying to anticipate the next surprise.
In one way, he felt an enormous sense of relief: All uncertainty about their departure was surely ended; Tanya could have no further reservations.
But a much greater uncertainty remained. What was happening?
There was only one experience in Floyd's life that matched the situation. As a very young man, he had once gone canoeing with some friends down a tributary of the Colorado River - and they had lost their way.
They had been swept faster and faster between the canyon walls, not completely helpless, but with only enough control to avoid being swamped. Ahead might be rapids - perhaps even a waterfall; they did not know. And in any case, there was little they could do about it.
Once again, Floyd felt himself in the grip of irresistible forces, sweeping him and his companions toward an unknown destiny. And this time the dangers were not only invisible; they might be beyond human comprehension.
45
Escape Manoeuvre
This is Heywood Floyd, making what I suspect - indeed, hope - will be my last report from Lagrange.
"We are now preparing for the return home; in a few days we will leave this strange place, here on the line between Io and Jupiter where we made our rendezvous with the huge, mysteriously vanished artifact we christened Big Brother. There is still not a single clue as to where it has gone - or why.
"For various reasons, it seems desirable for us not to remain here longer than necessary. And we will be able to leave at least two weeks earlier than we had originally planned by using the American ship Discovery as a booster for the Russian Leonov.
"The basic idea is simple; the two ships will be joined together, one mounted piggyback on the other. Discovery will burn all its propellant first, accelerating both vessels in the desired direction. When its fuel is exhausted, it will be cut loose - like an empty first stage - and Leonov will start to fire its engines. It won't use them earlier, because if it did it would waste energy dragging along the dead weight of Discovery.
"And we're going to use another trick, which - like so many of the concepts involved in space travel - at first sight seems to defy common sense. Although we're trying to get away from Jupiter, our first move is to get as close to it as we possibly can.
"We've been there once before, of course, when we used Jupiter's atmosphere to slow us down and get into orbit around the planet. This time we won't go quite so close - but very nearly.
"Our first burn, up here in the 350,000-kilometres-high orbit of Io, will reduce our velocity, so that we fall down to Jupiter and just graze its atmosphere. Then, when we're at the closest possible point, we'll burn all our fuel as quickly as we can, to increase speed and inject Leonov into the orbit back to Earth.
"What's the point of such a crazy manoeuvre? It can't be justified except by highly complex mathematics, but I think the basic principle can be made fairly obvious.
"As we allow ourselves to fall into Jupiter's enormous gravity field, we'll gain velocity - and hence energy. When I say 'we', I mean the ships and the fuel they carry.
"And we're going to burn the fuel right there - at the bottom of Jupiter's 'gravity well' - we're not going to lift it up again. As we blast it out from our reactors, it will share some of its acquired kinetic energy with us. Indirectly, we'll have tapped Jupiter's gravity, to speed us on the way back to Earth. As we used the atmosphere to get rid of our excess velocity when we arrived, this is one of the rare cases when Mother Nature - usually so frugal - allows us to have it both ways.
"With this triple boost - Discovery's fuel, its own, and Jupiter's gravity - Leonov will head sunward along a hyperbola that will bring it to Earth five months later. At least two months earlier than we could have managed otherwise.
"You will doubtless wonder what will happen to the good old Discovery. Obviously, we can't bring it home under automatic control, as we had originally planned. With no fuel, it will be helpless.
"But it will be perfectly safe. It will continue to loop round and round Jupiter on a highly elongated ellipse, like a trapped comet. And perhaps one day some future expedition may make another rendezvous, with enough extra fuel to bring it back to Earth. However, that certainly won't happen for a good many years.
"And now we must get ready for our departure. There is still much work to be done, and we won't be able to relax until that final burn starts us on the homeward orbit.
"We won't be sorry to leave, even though we've not achieved all our objectives. The mystery - perhaps the threat - of Big Brother's disappearance still haunts us, but there's nothing we can do about that.
"We've done our best - and we're coming home. This is Heywood Floyd, signing off."
There was a round of ironic clapping from his little audience, whose size would be multiplied many million-fold when the message reached Earth.
"I'm not talking to you," retorted Floyd, with slight embarrassment. "I didn't want you to hear it, anyway."
"You did your usual competent job, Heywood," said Tanya consolingly. "And I'm sure we all agree with everything you told the people back on Earth."
"Not quite," said a small voice, so softly that everyone had to strain in order to hear it. "There is still one problem."
The observation lounge suddenly became very sile
nt. For the first time in weeks, Floyd became aware of the faint throbbing from the main air-supply duct, and the intermittent buzz that might have been made by a wasp trapped behind a wall panel. Leonov, like all spacecraft, was full of such often inexplicable sounds, which one seldom noticed except when they stopped. And then it was usually a good idea to start investigating without further ado.
"I'm not aware of any problem, Chandra," said Tanya in an ominously calm voice. "What could it possibly be?"
"I've spent the last few weeks preparing Hal to fly thousand-day orbits back to Earth. Now all those programs will have to be dumped."
"We're sorry about that," answered Tanya, "but as things have turned out, surely this is a much better -"
"That's not what I mean," said Chandra. There was a ripple of astonishment; he had never before been known to interrupt anyone, least of all Tanya.
"We know how sensitive Hal is to mission objectives," he continued in the expectant hush that followed. "Now you are asking me to give him a program that may result in his own destruction. It's true that the present plan will put Discovery into a stable orbit - but if that warning has any substance, what will happen to the ship eventually? We don't know, of course - but it's scared us away. Have you considered Hal's reaction to this situation?"
"Are you seriously suggesting," Tanya asked very slowly, "that Hal may refuse to obey orders - exactly as on the earlier mission?"
"That is not what happened last time. He did his best to interpret conflicting orders."
"This time there need be no conflict. The situation is perfectly clear-cut."
"To us, perhaps. But one of Hal's prime directives is to keep Discovery out of danger. We will be attempting to override that. And in a system as complex as Hal's, it is impossible to predict all the consequences."
"I don't see any real problem," Sasha interjected. "We just don't tell him that there is any danger. Then he'll have no reservations about carrying out his program."
"Baby-sitting a psychotic computer!" muttered Curnow. "I feel I'm in a Grade-B science-fiction videodrama." Dr Chandra gave him an unfriendly glare.
"Chandra," Tanya demanded suddenly. "Have you discussed this with Hal?"
"No."
Was there a slight hesitation? Floyd wondered. It might have been perfectly innocent; Chandra could have been checking his memory. Or he could have been lying, improbable though that seemed.
"Then we'll do what Sasha suggests. Just load the new program into him, and leave it at that."
"And when he questions me about the change of plan?"
"Is he likely to do that - without your prompting?"
"Of course. Please remember that he was designed for curiosity. If the crew was killed, he had to be capable of running a useful mission, on his own initiative."
Tanya thought that over for a few moments.
"It's still quite a simple matter. He'll believe you, won't he?"
"Certainly."
"Then you must tell him that Discovery is in no danger, and that there will be a rendezvous mission to bring it back to Earth at a later date."
"But that is not true."
"We don't know that it's false," replied Tanya, beginning to sound a little impatient.
"We suspect that there is serious danger; otherwise we would not be planning to leave ahead of schedule."
"Then what do you suggest?" Tanya asked, in a voice that now held a distinct note of menace.
"We must tell him the whole truth, as far as we know it - no more lies or half-truths, which are just as bad. And then let him decide for himself."
"Hell, Chandra - he's only a machine!"
Chandra looked at Max with such a steady, confident gaze that the younger man quickly dropped his eyes.
"So are we all, Mr Brailovsky. It is merely a matter of degree. Whether we are based on carbon or on silicon makes no fundamental difference; we should each be treated with appropriate respect."
It was strange, thought Floyd, how Chandra - much the smallest person in the room - now seemed the largest. But the confrontation had gone on far too long. At any moment Tanya would start to issue direct orders, and the situation would become really nasty.
"Tanya, Vasili - can I have a word with you both? I think there is a way of resolving the problem."
Floyd's interruption was received with obvious relief, and two minutes later he was relaxing with the Orlovs in their quarters. (Or 'sixteenths', as Curnow had once christened them because of their size. He had soon regretted the pun, because he had to explain it to everyone except Sasha.)
"Thank you, Woody," said Tanya, as she handed him a bulb of his favourite Azerbaijan Shemakha. "I was hoping you'd do that. I suppose you have something - how do you put it? - up your sleeve."
"I believe so," Floyd answered, squirting a few cubic centimetres of the sweet wine into his mouth and savouring it gratefully. "I'm sorry if Chandra is being difficult."
"So am I. What a good thing we have only one mad scientist aboard."
"That's not what you've sometimes told me," grinned Academician Vasili. "Anyway, Woody - let's have it."
"This is what I suggest. Let Chandra go ahead and do it his way. Then there are just two possibilities.
"First, Hal will do exactly what we ask - control Discovery during the two firing periods. Remember, the first isn't critical. If something goes wrong while we're pulling away from Io, there's plenty of time to make corrections. And that will give us a good test of Hal's... willingness to cooperate."
"But what about the Jupiter flyby? That's the one that really counts. Not only do we burn most of Discovery's fuel there, but the timing and thrust vectors have to be exactly right."
"Could they be controlled manually?"
"I'd hate to try. The slightest error, and we'd either burn up, or become a long-period comet. Due again in a couple of thousand years."
"But if there was no alternative?" Floyd insisted.
"Well, assuming we could take control in time, and had a good set of alternative orbits precomputed - um, perhaps we might get away with it."
"Knowing you, Vasili, I'm sure that 'might' means 'would'. Which leads me to the second possibility I mentioned. If Hal shows the slightest deviation from the program - we take over."
"You mean - disconnect him?"
"Exactly."
"That wasn't so easy last time."
"We've learned a few lessons since then. Leave it to me. I can guarantee to give you back manual control in about half a second."
"There's no danger, I suppose, that Hal will suspect anything?"
"Now you're getting paranoiac, Vasili. Hal's not that human. But Chandra is - to give him the benefit of the doubt. So don't say a word to him. We all agree with his plan completely, are sorry that we ever raised any objections, and are perfectly confident that Hal will see our point of view. Right, Tanya?"
"Right, Woody. And I congratulate you on your foresight; that little gadget was a good idea."
"What gadget?" asked Vasili.
"I'll explain one of these days. Sorry, Woody - that's all the Shemakha you can have. I want to save it - until we're safely on the way to Earth."
46
Countdown
No one would ever believe this without my photos, thought Max Brailovsky as he orbited the two ships from half a kilometre away. It seems comically indecent, as if Leonov is raping Discovery. And now that he came to think of it, the rugged, compact Russian ship did look positively male, when compared with the delicate, slender American one. But most docking operations had distinctly sexual overtones, and he remembered that one of the early cosmonauts - he couldn't recall the name - had been reprimanded for his too vivid choice of words at the - er, climax of his mission.
As far as he could tell from his careful survey, everything was in order. The task of positioning the two ships and securing them firmly together had taken longer than anticipated. It would never have been possible at all without one of those strokes of luck that someti
mes - not always - favour those who deserve them. Leonov had providentially carried several kilometres of carbon filament tape, no bigger than the ribbon a girl might use to tie her hair, yet capable of taking a strain of many tons. It had been thoughtfully provided to secure instrument packages to Big Brother if all else failed. Now it wrapped Leonov and Discovery in tender embrace - sufficiently firmly, it was hoped, to prevent any rattlings and shakings at all accelerations up to the one-tenth of a gravity that was the maximum that full thrust could provide.
"Anything more you want me to check before I come home?" asked Max.
"No," replied Tanya. "Everything looks fine. And we can't waste any more time."
That was true enough. If that mysterious warning was to be taken seriously - and everyone now took it very seriously indeed - they should start their escape manoeuvre within the next twenty-four hours.
"Right - I'm bringing Nina back to the stable. Sorry about this, old girl."
"You never told us Nina was a horse."
"I'm not admitting it now. And I feel bad about dumping her here in space, just to give us a miserable few extra metres per second."
"We may be very glad of them in a few hours, Max. Anyway, there's always a chance that someone may come and pick her up again, one day."
I very much doubt it, thought Max. And perhaps, after all, it was appropriate to leave the little space pod there, as a permanent reminder of Man's first visit to the kingdom of Jupiter.
With gentle, carefully timed pulses from the control jets he brought Nina around the great sphere of Discovery's main life-support module; his colleagues on the flight deck barely glanced at him as he drifted past their curving window. The open Pod Bay door yawned before him, and he jockeyed Nina delicately down on to the extended docking arm.