When Poole joined him at the end of his sleep period, they spent ten minutes composing and polishing the reply. In the early stages of the mission, there had been countless requests from all the news media for interviews, discussions – almost anything that they cared to say. But as the weeks drifted uneventfully past, and the time lag increased from a few minutes to over an hour, interest had gradually slackened. Since the excitement of the Jupiter fly-by, over a month ago, they had made only three or four tapes for general release.
“Mission Control, this is X-ray-Delta-One. Here is your press statement.
“Earlier today, a minor technical problem occurred. Our HAL-9001 computer predicted the failure of the AE-35 unit.
“This is a small but vital component of the communication system. It keeps our main antenna aimed at Earth to within a few thousandths of a degree. This accuracy is required, since at our present distance of more than seven hundred million miles, Earth is only a rather faint star, and our very narrow radio beam could easily miss it.
“The antenna is kept constantly tracking Earth by motors controlled from the central computer. But those motors get their instructions via the AE-35 unit. You might compare it to a nerve center in the body, which translates the brain’s instructions to the muscles of a limb. If the nerve fails to pass on the correct signals, the limb becomes useless. In our case, a breakdown of the AE-35 unit could mean that the antenna will start pointing at random. This was a common trouble with the deep-space probes of the last century. They often reached other planets, then failed to send back any information because their antenna couldn’t locate Earth.
“We don’t know the nature of the fault yet, but the situation is not at all serious, and there is no need for alarm. We have two back-up AE-35s, each of which has an operational life expectancy of twenty years, so the chance that a second will fail during the course of this mission is’ negligible. Also, if we can diagnose the present trouble, we may be able to repair the number one unit.
“Frank Poole, who is specially qualified for this type of work, will go outside the ship and replace the faulty unit with the back-up. At the same time, he’ll take the opportunity of checking the hull and repairing some micropunctures that have been too small to merit a special EVA.
“Apart from this minor problem, the mission is still going uneventfully and should continue in the same manner.
“Mission Control, this is X-ray-Delta-One, two-one-zero-four, transmission concluded.”
22 – Excursion
Discovery’s extravehicular capsules or “space pods” were spheres about nine feet in diameter, and the operator sat behind a bay window which gave him a splendid view. The main rocket drive produced an acceleration of one-fifth of a gravity – just sufficient to hover on the Moon – while small attitude-control nozzles allowed for steering. From an area immediately beneath the bay window sprouted two sets of articulated metal arms or “waldoes,” one for heavy duty, the other for delicate manipulation. There was also an extensible turret carrying a variety of power tools, such as screwdrivers, jack-hammers, saws, and drills.
Space pods were not the most elegant means of transport devised by man, but they were absolutely essential for construction and maintenance work in vacuum. They were usually christened with feminine names, perhaps in recognition of the fact that their personalities were sometimes slightly unpredictable. Discovery’s trio were Anna, Betty, and Clara.
Once he had put on his personal pressure suit – his last line of defense – and climbed inside the pod, Poole spent ten minutes carefully checking the controls. He burped the steering jets, flexed the waldoes, reconfirmed oxygen, fuel, power reserve. Then, when he was completely satisfied, he spoke to Hal over the radio circuit. Though Bowman was standing by on the control deck, he would not interfere unless there was some obvious mistake or malfunction.
“This is Betty. Start pumping sequence.”
“Pumping sequence started,” repeated Hal. At once, Poole could hear the throbbing of the pumps as precious air was sucked out of the lock chamber. Presently, the thin metal of the pod’s external shell made crinkling, crackling noises, then, after about five minutes, Hal reported:
“Pumping sequence concluded.”
Poole made a final check of his tiny instrument panel. Everything was perfectly normal.
“Open outer door,” he ordered.
Again Hal repeated his instructions; at any stage, Poole had only to call “Hold!” and the computer would stop the sequence immediately.
Ahead, the walls of the ship slid apart. Poole felt the pod rock briefly as the last thin traces of air rushed into space. Then he was looking out at the stars – and, as it happened, at the tiny, golden disk of Saturn, still four hundred million miles away.
“Commence pod ejection.”
Very slowly, the rail from which the pod was hanging extended itself out through the open door until the vehicle was suspended just beyond the hull of the ship.
Poole gave a half-second burst on the main jet and the pod slid gently off the rail, becoming at last an independent vehicle pursuing its own orbit around the Sun. He now had no connection with Discovery – not even a safety line. The pods seldom gave trouble; and even if he got stranded, Bowman could easily come and rescue him.
Betty responded smoothly to the control; he let her drift outward for a hundred feet, then checked her forward momentum and spun her round so that he was looking back at the ship. Then he began his tour of the pressure hull.
His first target was a fused area about half an inch across, with a tiny central crater. The particle of dust that had impacted here at over a hundred thousand miles an hour was certainly smaller than a pinhead, and its enormous kinetic energy had vaporized it instantly. ‘As was often the case, the crater looked as if it had been caused by an explosion from inside the ship; at these velocities, materials behaved in strange ways and the laws of common-sense mechanics seldom applied.
Poole examined the area carefully, then sprayed it with sealant from a pressurized container in the pod’s general-purpose kit. The white, rubbery fluid spread over the metal skin, hiding the crater from view. The leak blew one large bubble, which burst when it was about six inches across, then a much smaller one, then it subsided as the fast-setting cement did its work, He watched it intently for several minutes, but there was no further sign of activity. However, to make doubly certain, he sprayed on a second layer; then he set off toward the antenna.
It took him some time to orbit Discovery’s spherical pressure hull, for he never let the pod build up a speed of more than a few feet a second. He was in no hurry, and it was dangerous to move at a high velocity so near the ship. He had to keep a sharp lookout for the various sensors and instrument booms that projected from the hull at unlikely places, and he also had to be careful with his own jet blast. It could do considerable damage if it happened to hit some of the more fragile equipment.
When at last he reached the long-range antenna, he surveyed the situation carefully. The big twenty-foot-diameter bowl appeared to be aimed directly at the Sun, for the Earth was now almost in line with the solar disk. The antenna mounting with all its orientation gear was therefore in total darkness, hidden in the shadow of the great metal saucer.
Poole had approached it from the rear; he had been careful not to go in front of the shallow parabolic reflector, lest Betty interrupt the beam and cause a momentary, but annoying, loss of contact with Earth. He could not see anything of the equipment he had come to service until he switched on the pod’s spotlights and banished the shadows.
Beneath that small metal plate lay the cause of the trouble. The plate was secured by four locknuts, and as the entire AE-35 unit had been designed for easy replacement, Poole did not anticipate any problems.
It was obvious, however, that he could not do the job while he remained in the space pod. Not only was it risky to maneuver so close to the delicate, and even spidery, framework of the antenna, but Betty’s control jets could easily buckle the paper-thin reflecting surface of the big radio mirror. He would have to park the pod twenty feet away and go out in his suit. In any event, he could remove the unit much more quickly with his gloved hands than with Betty’s remote manipulators.
All this he reported carefully to Bowman, who double-checked every stage in the operation before it was carried out. Though this was a simple, routine job, nothing could be taken for granted in space, and no detail must be overlooked. In extravehicular activities, there was no such thing as a “minor” mistake.