Pesquisador's extravehicular capsules or bolas were spheres about 9 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 1/5 of a gravity---just enough 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 coletores, one for heavy duty, the other for delicate manipulation. There was also an extensible turret carrying a variety of power tools, like screwdrivers, jackhammers, saws, and drills.364Please respect copyright.ＰＥＮＡＮＡqJleXmOWaK
Bolas were not the most elegant means of transport devised by man, but they were absolutely necessary for construction and maintenance work in vacuum. They were usually christened with feminine names, maybe in recognition of the fact that their personalities were sometimes slightly unpredictable. Pesquisador's trio were Ana, Isabel, and Clara.
Once he had put on his personal pressure suit---his last line of defense--and climbed inside the bola, Quarlos spent ten minutes carefully checking the controls. He burped the steering jets, flexed the coletores, reconfirmed oxygen, fuel, power reserve. Then, when he was completely satisfied, he spoke to H.A.L. over the radio circuit. Though Dhala was standing by on the control deck, he would not interfere unless there was some obvious mistake or malfunction.
"This is Isabel. Begin pumping sequence."
"Pumping sequence started," repeated H.A.L. At once, Quarlos 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 5 minutes, H.A.L. reported:
"Pumping sequence concluded."
Quarlos made a final check of his tiny instrument panel. Everything was perfectly normal.
"Open outer door," he ordered.
Again H.A.L. repeated his instructions; at any stage, Quarlos had only to call "Hold!" and the computer would stop the sequence immediately.
Ahead, the walls of the ship slid apart. Quarlos 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 ship's hull.
His first target was a fused area about 1/2 an inch across, with a tiny central crater. The particle of dust that had impacted here at over 100,000 m.p.h. was surely smaller than a pinhead, and it's 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 within the ship; at these velocities, materials behaved in strange ways and the laws of common-sense mechanics never applied.
Quarlos 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 6" across, then a much smaller one, then it subsided as the fast-setting cement did its job. He watched it intently for several minutes, but there was no further sign of activity. However, to make doubly sure, he sprayed on a second layer; then he set off toward the antenna.
It took him some time to orbit Pesquisador's spherical pressure hull, for he never let he pod build up speed of more than a few feet one 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 delicate equipment.
When at last he reached the long-range antenna, he surveyed the situation carefully. The big 20-foot diameter bowl seemed to be pointed directly at the Sun, as the Earth was now almost parallel 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.
Quarlos had approached it from the rear; he had been careful not to go in front of the shallow parabolic reflector, lest Isabel break the beam and cause a momentary, but irritating, loss of contact with Earth. He could not see anything of the equipment he'd come to service until he switched on the pod's spotlights and banished the shadows.
Beneath that little metal plate lay the cause of the trouble. The plate was secured by four lugnuts, and as the whole BF-46 unit had been designed for easy replacement, Quarlos didn't foresee any problems.
It was obvious, however, that he could not do the job while he stayed in the bola. Not only was it risky to maneuver so close to the delicate, and even spidery framework of the antenna, but Isabel's control jets could easily buckle the paper-thin reflecting surface of the big radio mirror. He would have to park the bola 20 feet away and go out in his suit. In any case, he could remove the unit much more quickly with his gloved hands than with Isabel's remote manipulators.
All this he carefully reported to Dhala, 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 EVA, there was no such thing in as a "minor" mishap.
He received the O.K. for the procedure, and parked the bola some 20 feet away from the base of the antenna support. There was no danger that it would drift off into space; nonetheless, he clamped a manipulator hand over one of the many short sections of ladder rung strategically mounted on the outer hull.
Then he checked the systems of his pressure suit, and, when he was quite satisfied, bled the air out of the bola. As Isabel's atmosphere hissed away into the vacuum of space, a cloud of ice crystals formed briefly around him, and the stars were dimmed momentarily.
There was one more thing to do before he left the bola. He switched over from manual to remote operation, putting Isabel now under the control of H.A.L. It was a standard safety precaution; though he was still secured to Isabel by an immensely strong spring-loaded cored little thicker than cotton, even the best safety lines had been known to fail. He would look like a fool if he needed his vehicle---and was unable to call it to his assistance by passing instructions to H.A.L.
The door of the pod swung open, and he drifted slowly out into the silence of space, his safety line unreeling behind him. Take things easy---never move fast---stop and think---these were the rules for EVA. If one obeyed them, there was never any trouble.
He grabbed one of Isabel's external handholds, and removed the spare BF-46 unit from the carry-pouch where it had been stowed, kangaroo style. He did not stop to collect any of the pod's collection of tools, most of which were not designed for use by human hands. All the adjustable wrenches and keys he was likely to need were already attached to the belt of his suit.
With one gentle push, he launched himself toward the gimbaled mounting of the big dish that loomed like a huge saucer between him and the Sun. His own double shadow, thrown by Isabel's spotlights, danced across the convex surface in fantastic patterns as he drifted down the twin beams. But here and there, he was surprised to notice, the rear of the great radio mirror sparkled with dazzlingly bright pinpoints of light.
He puzzled over these for the few seconds of his silent approach, then realized what they were. During the voyage, the reflector must have been penetrated many times by micrometeorites; he was seeing the sunlight blaring through the tiny craters. They were all far too small to have affected the system's performance appreciably.
As he was moving very slowly, he broke the gentle impact with his outstretched arm, and grabbed hold of the antenna mounting before he could rebound. He quickly hooked his safety belt to the closest attachment that would give him something to brace against when he used his tools. Then he paused, reported the situation to Dhala, and considered his next move.
There was one minor problem; he was standing (floating, rather) in his own light, and it was hard to see the BF-46 unit in the shadow he cast. So he ordered H.A.L. to swing the spots off to one side, and after a little experimenting got a more uniform illumination from secondary light reflected off the back of the antenna disk.
For a few seconds, he studied the small metal hatch with its four wire-secured locking nuts. Then, muttering to himself, "Tampering by unauthorized personnel invalidates the manufacturer's warranty," he snipped the wires and began to untwist the nuts. They were a standard size, fitting the 0-torgue wrench that he carried. The tool's internal spring mechanisms would absorb the reaction as the nuts were unthreaded, so that the operator would have no tendency to spin around in reverse.
The four nuts came off without any trouble, and Quarlos and tucked them carefully away in a convenient pouch. (One day, somebody had predicted, Earth would have a ring similar to Saturn's, only composed entirely of lost bolts, fasteners, and even tools that had escaped from careless orbital construction workers.) The metal cover was somewhat sticky, and for a moment he was afraid it might have cold-welded into place; but after a few taps it came loose, and he secured it to the antenna by mounting by a large crocodile clip.
Now he could see the electronic circuitry of the BF-46 unit. It was in the form of a thin slab, postcard-sized, gripped by a slow just big enough to hold it. The unit was held in place by two locking bars, and had a small handle so that it could be easily removed.
But it was still functioning, feeding the antenna the impulses that kept it pointed at the faraway pinpoint that was Earth. If it was pulled out now, all control would be gone, and the dish would slam round to its neutral or 0-azimuth position, pointing along the axis of Pesquisador. And this could be dangerous; it might crash into him as it rotated.
To prevent this specific hazard, all that was needed was to cut off power to the control system; then the antenna could not move, unless Qualros knocked against it himself. There was no danger of losing Earth during the few minutes it would take him to replace the unit; their target would not have shifted appreciably against the backdrop of stars in such a brief interval of time.
"H.A.L.," Quarlos called over the radio circuit, "I am about to remove the unit. Switch off all control power to the antenna system."
"Antenna control power off," replied H.A.L.
"I'm pulling the unit out----now."
The card slipped out of its slot without difficulty; it didn't jam, and none of the dozens of sliding contacts stuck. Within one minute, the spare was in place.364Please respect copyright.ＰＥＮＡＮＡjd2iu0mZj7
But Quarlos was not taking chances. He pushed himself gently away from the antenna mount, just in case the big dish went wild when power was restored. When he was safely out of range, he called to H.A.L.: "The new unit should be operational. Restore control power."
"Power restored," answered H.A.L. The antenna stayed steady as a rock.364Please respect copyright.ＰＥＮＡＮＡ3uWMA6f36K
"Carry out fault prediction tests."364Please respect copyright.ＰＥＮＡＮＡuvwBmKvQwt
Now micropulses would be bouncing through the unit's complex circuitry, probing for possible failures, testing the myriads of components to see that they all lay within their specified tolerances. This had been done, of course, a score of times before the unit had ever left the factory; but that was two years ago, and more than 1/2 a billion miles away. It was often impossible to see how solid-state electronic components could fail---yet they did.364Please respect copyright.ＰＥＮＡＮＡhodr3deMTT
"The circuit is now fully operational," reported H.A.L. after only ten seconds. In that time, he carried out as many tests as a small army of human inspectors.364Please respect copyright.ＰＥＮＡＮＡ1GN1OzcHCj
"Vivo!" said Quarlos with satisfaction. "I am now replacing the cover."364Please respect copyright.ＰＥＮＡＮＡCgaliTnS9j
This was often the most dangerous part of an EVA: when a job was finished and it was merely a matter of cleaning up and getting back inside the ship---that was when the mistakes were made. But Antonio Quarlos would not have been on this mission if he had not been careful and conscientious. He took his time, and though one of the locking nuts nearly got away from him, he caught it before it had traveled more than a few feet.364Please respect copyright.ＰＥＮＡＮＡCs2adVtI4b
15 minutes later he was jetting back into the bola garage, quietly confident that here was one job that need not be done again.364Please respect copyright.ＰＥＮＡＮＡ9jeQ0OHRuj
He was wrong.364Please respect copyright.ＰＥＮＡＮＡm4Gqdsi3sG
