by Various
According to the notes he had made before coming on watch, one of the UN's weather satellites was due over shortly. A blip appeared on the screen just beyond the 83° latitude line, across the Pole. He checked the time with the satellite ephemeris. If this were the satellite, it was ninety seconds early. That was too much error in the predicted orbit of a well-known satellite. Symbols sprang into existence beside the track. It was not quite high enough for the satellite, and the velocity was too low. As the white line swept across the screen again, more symbols appeared beside the track. Probable impact point was about 40° Latitude. It certainly wasn't the satellite. Two more blips appeared on the screen, at velocities and altitudes similar to the first. Each swipe of the white line left more new tracks on the screen. And the screens for the adjacent stations were showing similar behavior. These couldn't be meteors.
The Launch Control Officer slapped his hand down on a red push-button set into the arm of his chair, and spoke into his mike. "Red Alert. Attack is in progress." Then switching to another channel, he spoke to his assistants: "Take your preassigned sectors. Launch one interceptor at each track identified as hostile." He hadn't enough interceptors to double up on an attack of this size, and a quick glance at the screens for the adjacent stations showed he could expect no help from them. They would have their hands full. In theory, one interceptor could handle a missile all by itself. But the theory had never been tried in combat. That lack was about to be supplied.
* * * * *
Harry Lightfoot heard the alarm over the intercom. He vaguely understood what would happen before his launch order came. As each track was identified as hostile, a computer would be assigned to it. It would compute the correct time of launch, select an interceptor, and order it off the ground at the correct time. During the climb to intercept, the computer would radio steering signals to the interceptor, to assure that the intercept took place in the most efficient fashion. He knew RI 276 had been selected when a green light on the instrument panel flashed on, and a clock dial started indicating the seconds until launch. Just as the clock reached zero, a relay closed behind the instrument panel. The solid-fuel booster ignited with a roar. He was squashed back into his couch under four gees' acceleration.
Gyroscopes and acceleration-measuring instruments determined the actual trajectory of the ship; the navigation computer compared the actual trajectory with the trajectory set in before take-off; when a deviation from the pre-set trajectory occurred, the autopilot steered the ship back to the proper trajectory. As the computer on the ground obtained better velocity and position information about the missile from the ground radar, it sent course corrections to the ship, which were accepted in the computer as changes to the pre-set trajectory. The navigation computer hummed and buzzed; lights flickered on and off on the instrument panel; relays clicked behind the panel. The ship steered itself toward the correct intercept point. All this automatic operation was required because no merely human pilot had reflexes fast enough to carry out an intercept at twenty-six thousand feet per second. And even had his reflexes been fast enough, he could not have done the precise piloting required while being pummeled by this acceleration.
As it was, Major Harry Lightfoot, fighter pilot, lay motionless in his acceleration couch. His face was distorted by the acceleration. His breathing was labored. Compressed-air bladders in the legs of his gee-suit alternately expanded and contracted, squeezing him like the obscene embrace of some giant snake, as the gee-suit tried to keep his blood from pooling in his legs. Without the gee-suit, he would have blacked out, and eventually his brain would have been permanently damaged from the lack of blood to carry oxygen to it.
A red light on the instrument panel blinked balefully at him as it measured out the oxygen he required. Other instruments on the panel informed him of the amount of cooling air flowing through his suit to keep his temperature within the tolerable range, and the amount of moisture the dehumidifier had to carry away from him so that his suit didn't become a steam-bath. He was surrounded by hundreds of pounds of equipment which added nothing to the performance of the ship; which couldn't be counted as payload; which cut down on the speed and altitude the ship might have reached without them. Their sole purpose was to keep this magnificent high-performance, self-steering machine from killing its load of fragile human flesh.
At one hundred twenty-eight seconds after launch, the acceleration suddenly dropped to zero. He breathed deeply again, and swallowed repeatedly to get the salty taste out of his throat. His stomach was uneasy, but he wasn't spacesick. Had he been prone to spacesickness, he would never have been accepted as a Rocket Interceptor pilot. Rocket Interceptor pilots had to be capable of taking all the punishment their ships could dish out.
He knew there would be fifty seconds of free-fall before the rockets fired again. One solid-fuel stage had imparted to the ship a velocity which would carry it to the altitude of the missile it was to intercept. A second solid-fuel stage would match trajectories with the missile. Final corrections would be made with the liquid-fuel rockets in the third stage. The third stage would then become a glider which eventually would carry him back to Earth.
Before the second stage was fired, however, the ship had to be oriented properly. The autopilot consulted its gyros, took some star sights, and asked the navigation computer some questions. The answers came back in seconds, an interval which was several hours shorter than a human pilot would have required. Using the answers, the autopilot started to swing the ship about, using small compressed-gas jets for the purpose. Finally, satisfied with the ship's orientation, the autopilot rested. It patiently awaited the moment, precisely calculated by the computer on the ground, when it would fire the second stage.
Major Harry Lightfoot, fighter pilot, waited idly for the next move of his ship. He could only fume inwardly. This was no way for an Apache warrior to ride into battle. What would his grandfather think of a steed which directed itself into battle and which could kill its rider, not by accident, but in its normal operation? He should be actively hunting for that missile, instead of lying here, strapped into his couch so he wouldn't hurt himself, while the ship did all the work.
As for the missile, it was far to the north and slightly above the ship. Without purpose of its own, but obedient to the laws of Mr. Newton and to the wishes of its makers, it came on inexorably. It was a sleek aluminum cylinder, glinting in the sunlight it had just recently entered. On one end was a rocket-motor, now silent but still warm with the memory of flaming gas that had poured forth from it only minutes ago. On the other end was a sleek aerodynamic shape, the product of thousands of hours of design work. It was designed to enter the atmosphere at meteoric speed, but without burning up. It was intended to survive the passage through the air and convey its contents intact to the ground. The contents might have been virulent bacteria or toxic gas, according to the intentions of its makers. Among its brothers elsewhere in the sky this morning, there were such noxious loads. This one, however, was carrying the complex mechanism of a hydrogen bomb. Its destination was an American city; its object to replace that city with an expanding cloud of star-hot gas.
* * * * *
Suddenly the sleek cylinder disappeared in a puff of smoke, which quickly dissipated in the surrounding vacuum. What had been a precisely-built rocket had been reduced, by carefully-placed charges of explosive, to a collection of chunks of metal. Some were plates from the skin and fuel tanks. Others were large lumps from the computer-banks, gyro platform, fuel pumps, and other more massive components. This was not wanton destruction, however. It was more careful planning by the same brains which had devised the missile itself. To a radar set on the ground near the target, each fragment was indistinguishable from the nose cone carrying the warhead. In fact, since the fragments were separating only very slowly, they never would appear as distinct objects. By the time the cloud of decoys entered the atmosphere, its more than two dozen members would appear to the finest radar available on the ground as a single echo tw
enty-five miles across. It would be a giant haystack in the sky, concealing the most deadly needle of all time. No ground-controlled intercept scheme had any hope of selecting the warhead from among that deceptive cloud and destroying it.
The cloud of fragments possessed the same trajectory as the missile originally had. At the rate it was overtaking RI 276, it would soon pass the ship by. The autopilot of RI 276 had no intention of letting this happen, of course. At the correct instant, stage two thundered into life, and Harry Lightfoot was again smashed back into his acceleration couch. Almost absentmindedly, the ship continued to minister to his needs. Its attention was focused on its mission. After a while, the ground computer sent some instructions to the ship. The navigation computer converted these into a direction, and pointed a radar antenna in that direction. The antenna sent forth a stream of questing pulses, which quickly returned, confirming the direction and distance to the oncoming cloud of missile fragments. A little while later, fuel pumps began to whine somewhere in the tail of the ship. Then the acceleration dropped to zero as the second-stage thrust was terminated. There was a series of thumps as explosive bolts released the second stage. The whine of the pumps dropped in pitch as fuel gushed through them, and acceleration returned in a rush. The acceleration lasted for a few seconds, tapered off quickly, and ended. A light winked on on the instrument panel as the ship announced its mission was accomplished.
Major Harry Lightfoot, fighter pilot, felt a glow of satisfaction as he saw the light come on. He might not have reflexes fast enough to pilot the ship up here; he might not be able to survive the climb to intercept without the help of a lot of fancy equipment; but he was still necessary. He saw still one step ahead of this complex robot which had carried him up here. It was his human judgment and his ability to react correctly in an unpredictable situation which were needed to locate the warhead from among the cluster of decoys and destroy it. This was a job no merely logical machine could do. When all was said and done, the only purpose for the existence of this magnificent machine was to put him where he was now; in the same trajectory as the missile, and slightly behind it.
Harry Lightfoot reached for a red-handled toggle switch at the top of the instrument panel, clicked it from AUTO to MANUAL, and changed his status from passenger to pilot. He had little enough time to work. He could not follow the missile down into the atmosphere; his ship would burn up. He must begin his pull-out at not less than two hundred miles altitude. That left him one hundred eighty-three seconds in which to locate and destroy the warhead. The screen in the center of his instrument panel could show a composite image of the space in front of his ship, based on data from a number of sensing elements and detectors. He switched on an infrared scanner. A collection of spots appeared on the screen, each spot indicating by its color the temperature of the object it represented. The infrared detector gave him no range information, of course. But if the autopilot had done its job well, the nearest fragment would be about ten miles away. Thus even if he set off the enemy warhead, he would be safe. At that range the ship would not suffer any structural damage from the heat, and he could be down on the ground and in a hospital before any radiation effects could become serious.
He reflected quickly on the possible temperature range of the missile components. The missile had been launched from Central Asia, at night, in January. There was no reason to suppose that the warhead had been temperature-controlled during the pre-launch countdown. Thus it probably was at the ambient temperature of the launch site. If it had been fired in the open, that might be as low as minus 70° F. Had it been fired from a shelter, that might be as high as 70° F. To leave a safety margin, he decided to reject only those objects outside the range plus or minus 100° F. There were two fragments at 500° F. He rejected these as probably fragments of the engine. Six more exhibited a temperature of near minus 320° F. These probably came from the liquid oxygen tanks. They could be rejected. That eliminated eight of the objects on the screen. He had nineteen to go. It would be a lot slower for the rest, too.
* * * * *
He switched on a radar transmitter. The screen blanked out almost completely. The missile had included a micro-wave transmitter, to act as a jammer. It must have been triggered on by his approach. It obviously hadn't been operating while the ship was maneuvering into position. Had it been transmitting then, the autopilot would simply have homed on it. He switched the radar to a different frequency. That didn't work. The screen was still blank, indicating that the jammer was sweeping in frequency. He next tried to synchronize his radar pulses with the jammer, in order to be looking when it was quiet. The enemy, anticipating him, had given the jammer a variable pulse repetition rate. He switched off the transmitter, and scanned the radar antenna manually. He slowly swung it back and forth, attempting to fix the direction of the jammer by finding the direction of maximum signal strength. He found that the enemy had anticipated him again, and the jammer's signal strength varied. However, he finally stopped the antenna, satisfied that he had it pointed at the jammer. The infrared detector confirmed that there was something in the direction the antenna pointed, but it appeared too small to be the warhead.
He then activated the manual piloting controls. He started the fuel pumps winding up, and swung the ship to point normal to the line-of-sight to the jammer. A quick blast from the rockets sent the image of the jammer moving sideways across the screen. But, of greater importance, two other objects moved across the screen faster than the jammer, indicating they were nearer the ship than was the jammer. He picked the one which appeared the nearest to him, and with a series of maneuvers and blasts from the rockets placed the object between himself and the jammer. He switched the radar on again. Some of the jammer signal was still leaking through, but the object, whatever it was, made an effective shield. The radar images were quite sharp and clear.
He glanced at the clock. Nullifying the jammer had cost him seventy-five seconds. He'd have to hurry, in order to make up for that time. The infrared detector showed two targets which the radar insisted weren't there. He shifted radar frequency. They still weren't there. He decided they were small fragments which didn't reflect much radar energy, and rejected them. He set the radar to a linearly polarized mode. Eight of the targets showed a definite amplitude modulation on the echo. That meant they were rotating slowly. He switched to circular polarization, to see if they presented a constant area to the radar beam. He compared the echoes for both modes of polarization. Five of the targets were skin fragments, spinning about an axis skewed with respect to the radar beam. These he rejected. Two more were structural spars. They couldn't conceal a warhead. He rejected them. After careful examination of the fine structure of the echo from the last object, he was able to classify it as a large irregular mass, probably a section of computer, waving some cables about. Its irregularity weighed against its containing the warhead. Even if it didn't burn up in the atmosphere, its trajectory would be too unpredictable.
He turned to the rest of the targets. Time was getting short. He extracted every conceivable bit of information out of what his detectors told him. He checked each fragment for resonant frequencies, getting an idea of the size and shape of each. He checked the radiated infrared spectrum. He checked the decrement of the reflected radar pulse. Each scrap of information was an indication about the identity of the fragments. With frequent glances at the clock, constantly reminding him of how rapidly his time was running out, he checked and cross-checked the data coming in to him. Fighting to keep his mind calm and his thoughts clear, he deduced, inferred, and decided. One fragment after another, he sorted, discarded, rejected, eliminated, excluded. Until the screen was empty.
Now what? Had the enemy camouflaged the warhead so that it looked like a section of the missile's skin? Not likely. Had he made a mistake in his identification of the fragments? Possibly, but there wasn't time to recheck every fragment. He decided that the most likely event was that the warhead was hidden by one of the other fragments. He swung the ship; hea
ded it straight for the object shielding him from the jammer, which had turned out to be a section from the fuel tank. A short blast from the rockets sent him drifting toward the object. One image on the screen broadened; split in two. A hidden fragment emerged from behind one of the ones he had examined. He rejected it immediately. Its temperature was too low. He was almost upon the fragment shielding him from the jammer. If he turned to avoid it, the jammer would blank-out his radar again. He thought back to his first look at the cloud of fragments. There had been nothing between his shield and the jammer. The only remaining possibility, then, was that the warhead was being hidden from him by the jammer itself. He would have to look on the other side of the jammer, using the ship itself as a shield.
He swung out from behind the shielding fragment, and saw his radar images blotted out. He switched off the radar, and aimed the ship slightly to one side of the infrared image of the jammer. Another blast from the rockets sent him towards the jammer. Without range information from the radar, he would have to guess its distance by noting the rate at which it swept across the screen. The image of the jammer started to expand as he approached it. Then it became dumbbell shaped and split in two.
