difference between the orbit of such asatellite and the trajectory of an ICBM. Fortunately most satelliteorbits were catalogued and available for comparison with incomingtracks. However, once in a while an unannounced satellite was launched,and these could cause trouble. Only the previous week, at a station downthe line, an interceptor had been launched at an unannounced satellite.Had the pilot not realized what he was chasing and held his fire, theinternational complications could have been serious. It was hard toimagine World War III being started by an erroneous interceptorlaunching, but the State Department would be hard put to soothe thefeelings of some intensely nationalistic country whose expensive newsatellite had been shot down. Such mistakes were bound to occur, but theLaunch Control Officer preferred that they be made when someone else,not he, was on watch. For this reason he attempted to anticipate allknown satellites, so they would be recognized as soon as they appeared.
According to the notes he had made before coming on watch, one of theUN's weather satellites was due over shortly. A blip appeared on thescreen just beyond the 83 deg. latitude line, across the Pole. He checkedthe time with the satellite ephemeris. If this were the satellite, itwas ninety seconds early. That was too much error in the predicted orbitof a well-known satellite. Symbols sprang into existence beside thetrack. It was not quite high enough for the satellite, and the velocitywas too low. As the white line swept across the screen again, moresymbols appeared beside the track. Probable impact point was about 40 deg.Latitude. It certainly wasn't the satellite. Two more blips appeared onthe screen, at velocities and altitudes similar to the first. Each swipeof the white line left more new tracks on the screen. And the screensfor the adjacent stations were showing similar behavior. These couldn'tbe meteors.
The Launch Control Officer slapped his hand down on a red push-buttonset into the arm of his chair, and spoke into his mike. "Red Alert.Attack is in progress." Then switching to another channel, he spoke tohis assistants: "Take your preassigned sectors. Launch one interceptorat each track identified as hostile." He hadn't enough interceptors todouble up on an attack of this size, and a quick glance at the screensfor the adjacent stations showed he could expect no help from them. Theywould have their hands full. In theory, one interceptor could handle amissile 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 understoodwhat would happen before his launch order came. As each track wasidentified as hostile, a computer would be assigned to it. It wouldcompute the correct time of launch, select an interceptor, and order itoff the ground at the correct time. During the climb to intercept, thecomputer would radio steering signals to the interceptor, to assure thatthe intercept took place in the most efficient fashion. He knew RI 276had been selected when a green light on the instrument panel flashed on,and a clock dial started indicating the seconds until launch. Just asthe clock reached zero, a relay closed behind the instrument panel. Thesolid-fuel booster ignited with a roar. He was squashed back into hiscouch under four gees' acceleration.
Gyroscopes and acceleration-measuring instruments determined the actualtrajectory of the ship; the navigation computer compared the actualtrajectory with the trajectory set in before take-off; when a deviationfrom the pre-set trajectory occurred, the autopilot steered the shipback to the proper trajectory. As the computer on the ground obtainedbetter velocity and position information about the missile from theground radar, it sent course corrections to the ship, which wereaccepted in the computer as changes to the pre-set trajectory. Thenavigation computer hummed and buzzed; lights flickered on and off onthe instrument panel; relays clicked behind the panel. The ship steereditself toward the correct intercept point. All this automatic operationwas required because no merely human pilot had reflexes fast enough tocarry out an intercept at twenty-six thousand feet per second. And evenhad his reflexes been fast enough, he could not have done the precisepiloting required while being pummeled by this acceleration.
As it was, Major Harry Lightfoot, fighter pilot, lay motionless in hisacceleration couch. His face was distorted by the acceleration. Hisbreathing was labored. Compressed-air bladders in the legs of hisgee-suit alternately expanded and contracted, squeezing him like theobscene embrace of some giant snake, as the gee-suit tried to keep hisblood from pooling in his legs. Without the gee-suit, he would haveblacked out, and eventually his brain would have been permanentlydamaged from the lack of blood to carry oxygen to it.
A red light on the instrument panel blinked balefully at him as itmeasured out the oxygen he required. Other instruments on the panelinformed him of the amount of cooling air flowing through his suit tokeep his temperature within the tolerable range, and the amount ofmoisture the dehumidifier had to carry away from him so that his suitdidn't become a steam-bath. He was surrounded by hundreds of pounds ofequipment which added nothing to the performance of the ship; whichcouldn't be counted as payload; which cut down on the speed and altitudethe ship might have reached without them. Their sole purpose was to keepthis magnificent high-performance, self-steering machine from killingits load of fragile human flesh.
At one hundred twenty-eight seconds after launch, the accelerationsuddenly dropped to zero. He breathed deeply again, and swallowedrepeatedly to get the salty taste out of his throat. His stomach wasuneasy, but he wasn't spacesick. Had he been prone to spacesickness, hewould never have been accepted as a Rocket Interceptor pilot. RocketInterceptor pilots had to be capable of taking all the punishment theirships could dish out.
He knew there would be fifty seconds of free-fall before the rocketsfired again. One solid-fuel stage had imparted to the ship a velocitywhich 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 thethird stage. The third stage would then become a glider which eventuallywould carry him back to Earth.
Before the second stage was fired, however, the ship had to be orientedproperly. The autopilot consulted its gyros, took some star sights, andasked the navigation computer some questions. The answers came back inseconds, an interval which was several hours shorter than a human pilotwould have required. Using the answers, the autopilot started to swingthe ship about, using small compressed-gas jets for the purpose.Finally, satisfied with the ship's orientation, the autopilot rested. Itpatiently awaited the moment, precisely calculated by the computer onthe ground, when it would fire the second stage.
Major Harry Lightfoot, fighter pilot, waited idly for the next move ofhis ship. He could only fume inwardly. This was no way for an Apachewarrior to ride into battle. What would his grandfather think of a steedwhich directed itself into battle and which could kill its rider, not byaccident, but in its normal operation? He should be actively hunting forthat missile, instead of lying here, strapped into his couch so hewouldn'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 andto the wishes of its makers, it came on inexorably. It was a sleekaluminum cylinder, glinting in the sunlight it had just recentlyentered. On one end was a rocket-motor, now silent but still warm withthe memory of flaming gas that had poured forth from it only minutesago. On the other end was a sleek aerodynamic shape, the product ofthousands of hours of design work. It was designed to enter theatmosphere at meteoric speed, but without burning up. It was intended tosurvive the passage through the air and convey its contents intact tothe ground. The contents might have been virulent bacteria or toxic gas,according to the intentions of its makers. Among its brothers elsewherein the sky this morning, there were such noxious loads. This one,however, was carrying the complex mechanism of a hydrogen bomb. Itsdestination was an American city; its object to replace that city withan expanding cloud of star-hot gas.
* * *
* *
Suddenly the sleek cylinder disappeared in a puff of smoke, whichquickly dissipated in the surrounding vacuum. What had been aprecisely-built rocket had been reduced, by carefully-placed charges ofexplosive, to a collection of chunks of metal. Some were plates from theskin and fuel tanks. Others were large lumps from the computer-banks,gyro platform, fuel pumps, and other more massive components. This wasnot wanton destruction, however. It was more careful planning by thesame brains which had devised the missile itself. To a radar set on theground near the target, each fragment was indistinguishable from thenose cone carrying the warhead. In fact, since the fragments wereseparating only very slowly, they never would appear as distinctobjects. By the time the cloud of decoys entered the atmosphere, itsmore than two dozen members would appear to the finest radar availableon the ground as a single echo twenty-five miles across. It would be agiant haystack in the sky,