The Collected Stories of Arthur C. Clarke (33 page)

There is no need to go into technical details, but those who are still unconvinced might like to consider these elementary facts. A rocket-driven spaceship can, obviously, only accelerate along its major axis—that is, ‘forwards’. Any deviation from a straight course demands a physical turning of the ship, so that the motors can blast in another direction. Everyone knows that this is done by internal gyros or tangential steering jets: but very few people know just how long this simple manoeuvre takes. The average cruiser, fully fuelled, has a mass of two or three thousand tons, which does not make for rapid footwork. But things are even worse than this, for it is not the mass, but the moment of inertia that matters here—and since a cruiser is a long, thin object, its moment of inertia is slightly colossal. The sad fact remains (though it is seldom mentioned by astronautical engineers) that it takes a good ten minutes to rotate a spaceship through 180 degrees, with gyros of any reasonable size. Control jets are not much quicker, and in any case their use is restricted because the rotation they produce is permanent and they are liable to leave the ship spinning like a slow-motion pin-wheel, to the annoyance of all inside.

In the ordinary way, these disadvantages are not very grave. One has millions of kilometres and hundreds of hours in which to deal with such minor matters as a change in the ship’s orientation. It is definitely against the rules to move in ten-kilometre-radius circles, and the commander of the
Doradus
felt distinctly aggrieved. K.15 wasn’t playing fair.

At the same moment that resourceful individual was taking stock of the situation, which might very well have been worse. He had reached the hills in three jumps and felt less naked than he had out in the open plain. The food and equipment he had taken from the ship he had hidden where he hoped he could find it again, but as his suit could keep him alive for over a day that was the least of his worries. The small packet that was the cause of all the trouble was still with him, in one of those numerous hiding places a well-designed spacesuit affords.

There was an exhilarating loneliness about his mountain eyrie, even though he was not quite as lonely as he would have wished. For ever fixed in his sky, Mars was waning almost visibly as Phobos swept above the night side of the planet. He could just make out the lights of some of the Martian cities, gleaming pin-points marking the junctions of the invisible canals. All else was stars and silence and a line of jagged peaks so close it seemed he could almost touch them. Of the
Doradus
there was still no sign. She was presumably carrying out a careful telescopic examination of the sunlit side of Phobos.

Mars was a very useful clock: when it was half-full the Sun would rise and, very probably, so would the
Doradus
. But she might approach from some quite unexpected quarter: she might even—and this was the one real danger—she might even have landed a search party.

This was the first possibility that had occurred to Commander Smith when he saw just what he was up against. Then he realised that the surface area of Phobos was over a thousand square kilometres and that he could not spare more than ten men from his crew to make a search of that jumbled wilderness. Also, K.15 would certainly be armed.

Considering the weapons which the
Doradus
carried, this last objection might seem singularly pointless. It was very far from being so. In the ordinary course of business, sidearms and other portable weapons are as much use to a space-cruiser as are cutlasses and crossbows. The
Doradus
happened, quite by chance—and against regulations at that—to carry one automatic pistol and a hundred rounds of ammunition. Any search party would therefore consist of a group of unarmed men looking for a well-concealed and very desperate individual who could pick them off at his leisure. K.15 was breaking the rules again.

The terminator of Mars was now a perfectly straight line, and at almost the same moment the Sun came up, not so much like thunder as like a salvo of atomic bombs. K.15 adjusted the filters of his visor and decided to move. It was safer to stay out of the sunlight, not only because he was less likely to be detected in the shadow but also because his eyes would be much more sensitive there. He had only a pair of binoculars to help him, whereas the
Doradus
would carry an electronic telescope of twenty centimetres aperture at least.

It would be best, K.15 decided, to locate the cruiser if he could. It might be a rash thing to do, but he would feel much happier when he knew exactly where she was and could watch her movements. He could then keep just below the horizon, and the glare of the rockets would give him ample warning of any impending move. Cautiously launching himself along an almost horizontal trajectory, he began the circumnavigation of his world.

The narrowing crescent of Mars sank below the horizon until only one vast horn reared itself enigmatically against the stars. K.15 began to feel worried: there was still no sign of the
Doradus
. But this was hardly surprising, for she was painted black as night and might be a good hundred kilometres away in space. He stopped, wondering if he had done the right thing after all. Then he noticed that something quite large was eclipsing the stars almost vertically overhead, and was moving swiftly even as he watched. His heart stopped for a moment: then he was himself again, analysing the situation and trying to discover how he had made so disastrous a mistake.

It was some time before he realised that the black shadow slipping across the sky was not the cruiser at all, but something almost equally deadly. It was far smaller, and far nearer, than he had at first thought. The
Doradus
had sent her television-homing guided missiles to look for him.

This was the second danger he had feared, and there was nothing he could do about it except to remain as inconspicuous as possible. The
Doradus
now had many eyes searching for him, but these auxiliaries had very severe limitations. They had been built to look for sunlit spaceships against a background of stars, not to search for a man hiding in a dark jungle of rock. The definition of their television systems was low, and they could only see in the forward direction.

There were rather more men on the chess-board now, and the game was a little deadlier, but his was still the advantage.

The torpedo vanished in the night sky. As it was travelling on a nearly straight course in this low-gravitational field, it would soon be leaving Phobos behind, and K.15 waited for what he knew must happen. A few minutes later, he saw a brief stabbing of rocket exhausts and guessed that the projectile was swinging slowly back on its course. At almost the same moment he saw another flare away in the opposite quarter of the sky and wondered just how many of these infernal machines were in action. From what he knew of Z-class cruisers—which, was a good deal more than he should—there were four missile control channels, and they were probably all in use.

He was suddenly struck by an idea so brilliant that he was quite sure it could not possibly work. The radio on his suit was a tunable one, covering an unusually wide band, and somewhere not far away the
Doradus
was pumping out power on everything from a thousand megacycles upwards. He switched on the receiver and began to explore.

It came in quickly—the raucous whine of a pulse transmitter not far away. He was probably only picking up a sub-harmonic, but that was quite good enough. It D/F’ed sharply, and for the first time K.15 allowed himself to make long-range plans about the future. The
Doradus
had betrayed herself: as long as she operated her missiles, he would know exactly where she was.

He moved cautiously forward towards the transmitter. To his surprise the signal faded, then increased sharply again. This puzzled him until he realised that he must be moving through a diffraction zone. Its width might have told him something useful if he had been a good enough physicist, but he could not imagine what.

The
Doradus
was hanging about five kilometres above the surface in full sunlight. Her ‘non-reflecting’ paint was overdue for renewal, and K.15 could see her clearly. As he was still in darkness, and the shadow line was moving away from him, he decided that he was as safe here as anywhere. He settled down comfortably so that he could just see the cruiser and waited, feeling fairly certain that none of the guided projectiles would come so near the ship. By now, he calculated, the Commander of the
Doradus
must be getting pretty mad. He was perfectly correct.

After an hour, the cruiser began to heave herself round with all the grace of a bogged hippopotamus. K.15 guessed what was happening. Commander Smith was going to have a look at the antipodes, and was preparing for the perilous fifty-kilometre journey. He watched very carefully to see the orientation the ship was adopting, and when she came to rest again was relieved to see that she was almost broadside on to him. Then, with a series of jerks that could not have been very enjoyable aboard, the cruiser began to move down to the horizon. K.15 followed her at a comfortable walking pace—if one could use the phrase—reflecting that this was a feat very few people had ever performed. He was particularly careful not to overtake her on one of his kilometre-long glides, and kept a close watch for any missiles that might be coming up astern.

It took the
Doradus
nearly an hour to cover the fifty kilometres. This, as K.15 amused himself by calculating, represented considerably less than a thousandth of her normal speed. Once, she found herself going off into space at a tangent, and rather than waste time turning end over end again fired off a salvo of shells to reduce speed. But she made it at last, and K.15 settled down for another vigil, wedged between two rocks where he could just see the cruiser and he was quite sure she could not see him. It occurred to him that by this time Commander Smith might have great doubts as to whether he really was on Phobos at all, and he felt like firing off a signal flare to reassure him. However, he resisted the temptation.

There would be little point in describing the events of the next ten hours, since they differed in no important detail from those that had gone before. The
Doradus
made three other moves, and K.15 stalked her with the care of the big-game hunter following the spoor of some elephantine beast. Once, when she would have led him out into full sunlight, he let her fall below the horizon until he could only just pick up her signals. But most of the time he kept her just visible, usually low down behind some convenient hill.

Once a torpedo exploded some kilometres away, and K.15 guessed that some exasperated operator had seen a shadow he did not like—or else that a technician had forgotten to switch off a proximity fuse. Otherwise nothing happened to enliven the proceedings: in fact the whole affair was becoming rather boring. He almost welcomed the sight of an occasional guided missile drifting inquisitively overhead, for he did not believe that they could see him if he remained motionless and in reasonable cover. If he could have stayed on the part of Phobos exactly opposite the cruiser he would have been safe even from these, he realised, since the ship would have no control there in the Moon’s radio-shadow. But he could think of no reliable way in which he could be sure of staying in the safety zone if the cruiser moved again.

The end came very abruptly. There was a sudden blast of steering-jets, and the cruiser’s main drive burst forth in all its power and splendour. In seconds the
Doradus
was shrinking sunwards, free at last, thankful to leave, even in defeat, this miserable lump of rock that had so annoyingly baulked her of her legitimate prey. K.15 knew what had happened, and a great sense of peace and relaxation swept over him. In the radar room of the cruiser, someone had seen an echo of disconcerting amplitude approaching with altogether excessive speed. K.15 now had only to switch on his suit beacon and to wait. He could even afford the luxury of a cigarette.

‘Quite an interesting story,’ I said, ‘and I see now how it ties up with that squirrel. But it does raise one or two queries in my mind.’

‘Indeed?’ said Rupert Kingman politely.

I always like to get to the bottom of things, and I knew that my host had played a part in the Jovian War about which he seldom spoke. I decided to risk a long shot in the dark.

‘May I ask how you happen to know so much about this unorthodox military engagement? It isn’t possible, is it, that
you
were K.15?’

There was an odd sort of strangling noise from Carson. Then Kingman said, quite calmly: ‘No, I wasn’t.’

He got to his feet and went off towards the gun-room.

‘If you’ll excuse me a moment, I’m going to have another shot at that tree-rat. Maybe I’ll get him this time.’ Then he was gone.

Carson looked at me as if to say: ‘This is another house you’ll never be invited to again.’ When our host was out of earshot he remarked in a coldly clinical voice:

‘You’ve torn it. What did you have to say that for?’

‘Well, it seemed a safe guess. How else could he have known all that?’

‘As a matter of fact, I believe he met K.15 after the War: they must have had an interesting conversation together. But I thought you knew that Rupert was retired from the Service with only the rank of Lieutenant-Commander. The Court of Inquiry could never see his point of view. After all, it just wasn’t reasonable that the Commander of the fastest ship in the Fleet couldn’t catch a man in a spacesuit.’

Breaking Strain

First published in
Thrilling Wonder Stories
, December 1949, as ‘Thirty Seconds—Thirty Days’

Collected in
Expedition to Earth