began to blur, and the urge to break something grew almost irresistible, he called it a day and slept two or three hours. After the second period, he couldn't sleep either.
Really, he was undeservedly lucky. One of the radiometers reacted after only eighteen hours of blind search. His near hysteria vanished instantly, washed away in a flood of relief; and with hands once more reasonably steady he swung the little ship until the emanations registered on the bow meter. He noted the strength of the reading, cut in the second-order fields for five seconds, and read the dial again. He knew the inverse square law, at least; he figured for a moment, then drove forward again for eleven more seconds, and cut the fields between twenty and thirty million miles from the source of the radiation.
It was visible to the naked eye at that range, which, in a way, was unfortunate. Had it not been, La Roque would have had a few more happy minutes. As things were, he took one look at the forward plate, and for the next ninety seconds used language which should really have been recorded for the benefit of future sailors. He had some excuse. The star was listed in the chart reference as single; La Roque had chosen it for that reason. However, plainly visible on the plate, revolving evidently almost in contact, were two smoky red suns — a close binary system.
Of course, no one would normally be greatly interested. The Astrographic Survey vessel which had covered the section had probably swept past fifty billion miles out, and noted the system's existence casually as its radiometers flickered. Size? Mass? Companions, if any? Planets? Who cared!
La Roque, of course.
The stars were red dwarfs, small and dense. They would have been seen to be irregular variables, if anyone had looked long enough; for their surface temperatures were so low that “cirrus” clouds of solid carbon particles formed and dispersed at random in their atmospheres. The larger sun was perhaps a hundred thousand miles in diameter, the other only slightly smaller. Their centers were roughly half a million miles apart, and the period of revolution about eight hours. In spite of their relatively high density, there were very noticeable tidal bulges on both.
All these facts would have been of absorbing interest to an astronomer seeking data on the internal structure of red dwarf stars; La Roque didn't know any of them, and at first didn't give a darn. He was wondering how a stable orbit could be established close enough to this system to keep him from freezing without using ship's power. The near-circular one he had planned was out; it would have had to be less than a million miles from a single sun of such late type, and the doubling of the heat source wasn't much help.
He thought of doubling back to one of the other systems which the chart had said to be single; but the nerve-racking search and disappointment he had suffered the first time made him hesitate. It was while he hesitated that memory came to his aid.
There had been an episode in his experiences which had occurred on Hector, one of the Trojan asteroids. Circumstances had caused him to remain there for some time, and a friendly jailer had explained to him just where Hector was and why it stayed there. It was in the stability point at the third corner of an equilateral triangle whose other corners were Sol and Jupiter; and though it could — and did — wobble millions of miles from the actual point, gravitational forces always brought it back.
La Roque looked out at the twin suns. Could his ship stand the temperature at the Trojan points of this system? More important, could he stand it?
He could. His instruments gave the energy distribution curve of the suns; one of the reference charts contained a table that turned the curves into surface temperatures. He was able to measure the distance between the centers of the suns, from the scale lines on the plate and his distance, which he knew roughly. Half a million miles from the surface of a star whose radius was fifty thousand miles and whose effective radiating temperature was a thousand degrees absolute, the black-body temperature was, according to his figures, about thirty degrees Centigrade. The presence of two stars made it decidedly warmer, but his ship was well insulated and the surface highly polished. It would eventually reach an equilibrium temperature considerably above that of an ideal black body, but it would take a long time doing so.
It seemed, then, that the Trojan point was the best place for him. He could find it easily enough; getting the centers of the stars sixty degrees apart would put him at the right distance. He could find the proper plane by moving around until the two suns appeared to move across each other in straight lines. It would not take long; by varying his distance from the system he could, in a few minutes, observe it through half a revolution.
It took him, in fact, less than an hour to find the orbital plane of the suns. It took him five and a half hours of first-order acceleration at one gravity to get rid of the hundred and twenty mile per second velocity difference between Sol and this system — fortunately, the chart had mentioned the high relative velocity, or La Roque would never have thought of such a thing. In a way, he didn't mind the necessity; it was good to have weight for the first time in nearly a month. He was, of course, a little worried at the amount of time consumed; he wished he had not wasted so much of the commodity in putting Sol so far behind.
He cut the first-order drive the instant his clock told him the speeds should be equal, headed for the twin suns, and hopped for his Trojan point. Since moving bodies were involved, he had to make five legs out of the short trip — he failed to allow for the short period of the system and the fact that he started the first leg several light-hours from his goal.
He got there eventually, however. He suddenly realized that he would have to use first-order power again, to give his ship something like the proper orbital velocity; but even he was able to understand the proper magnitude and direction of this new vector; the only unjustified assumption he had to make was that the suns were of equal masses, and this happened to be nearly the case. He wasn't too worried; he understood that in a Trojan orbit such small variations are opposed, not helped, by the gravity of the primary bodies. He was quite right.
He cut all his power except the detector relay currents, which did not radiate appreciably. To these he connected an alarm, and set them to synchronize with the low-frequency waves which form the “wake” of a vessel cruising at second-order speeds. Then, abruptly feeling the reaction of the past days, he drifted over to a “bunk,” moored himself, and was instantly asleep.
It is impossible to say just how long he slept; he was exhausted mentally and emotionally, and when weightless the human body can approach a condition near to suspended animation, if given the chance. It couldn't have been for very many hours, but the alarm rang for minutes before its sound penetrated to his consciousness. When it did, he had to wait several moments before he could move a muscle.
Recovered at last, he unmoored himself and kicked his body across the narrow cabin to the instrument board, and cut the alarm, cursing. He had forgotten that the bell would radiate, and was not sure that the hull would shield its waves. The detectors were reacting violently, the needles wobbling rapidly from positive to negative limits. He knew that a ship had driven past in second-order flight, but that was as far as he could interpret the readings. It would have required an expert to compute the speed, type, and distance of the ship creating the disturbance.
After a few minutes, the needles quieted. La Roque remained at the board, judging that the ship had not left for good. He was right. The disturbances started again half an hour later, and kept up for hours thereafter — sometimes so feeble as to cause a barely visible quiver of the needles, sometimes slamming them against the stop pins with audible clicks. La Roque was incapable of reading any meaning except changing distance into this phenomenon.
The “wake” of a ship in straight-line, second-order flight consists of a few low-frequency electromagnetic waves, the wave-front being, as can easily be seen, coneshaped, with the ship at the apex. The cone expands radially at the speed of light, and its tip moves forward with the ship — in the case of a military craft, at anywhere up to something like a million light velocities.
If the ship is not in straight-line flight, but cutting its fields and changing direction every few minutes or seconds, the shape of the wave front becomes rather complex. A standard search path spirals around the surface of a torus, and after a few hours the traces of such a flight would be the despair of a competent mathematician, let alone an amateur at a comparatively fixed observation post. The space for billions of miles around that binary sun was quivering with crisscrossing wave fronts. Each set the needles of La Roque's detectors quivering in tune as it passed him, and each quiver brought beads of sweat to the runaway's brow. His own ship, he realized, had left similar fronts; and he had shaved his margin of escape much too fine. Had they been given a week, or even three or four days, for expansion at the speed of light, he could have ceased to worry about their being used to trail him.
