Chapter 22 Chapter 2 Installing Spare Parts

Discovery's extravehicular work craft, or "cosmic capsules," are nine-foot-diameter spheres with wide-field views from which crew members sit by windows.Its main rocket thrust can produce an acceleration one-fifth that of gravity—just enough to lumber on the moon—and some small nozzles that control altitude can be used to steer it.From a unit directly below the window projected two sets of articulated metal arms, or "Waldos," one for heavy work and the other for delicate work.There is also a tower of considerable size, which houses various power tools, such as augers, pneumatic drills, chainsaws, electric drills, etc.

The space capsule is not the most beautiful vehicle designed by humans, but it is absolutely indispensable for construction or maintenance in a vacuum.It is generally named after a woman, probably because its character is sometimes a little elusive. The three "Discovery" were named: Anna, Betty and Clara. Poole donned his personal air-pressurized suit—the last line of defense—and spent ten minutes scrutinizing the controls after climbing into the capsule.He tried the pilot jet engine, stretched the Waldo, checked the oxygen, fuel, power reserves, and when he was completely satisfied, he spoke to Hal over the radio.Although Bowman was standing right next to the console, he was reluctant to intervene except in obvious mistakes or loss of control.

"I'm Betty. Start continuous decompression." "Continuous decompression begins," Hal repeated. Immediately, Poole could hear the flutter of the pump as precious air was pumped out of the airlock.Then there was a sizzling, crackling sound on the thin metal shell of the compartment; and then.After about five minutes, Hal reported, "Complete decompression sequence." Poole made a final check of his fine dial, and everything was perfectly fine. "Open the outer door," he ordered. Hal repeated his command; at any stage, as soon as Poole yelled "Stop!" the computer would immediately abort the entire program.

At the front of the ship, the walls slide away.Poole felt the capsule shake slightly as the last breath of air escaped into outer space.Then, before his eyes was a field of stars—right in front of the little golden disk of Saturn, 400 million miles away. "Start ejecting the capsule." Slowly, the steel rails that suspend the capsule stretch out the open door, suspending the vehicle outside the hull of the spaceship. Betty was responsive to the maneuvers; Poole floated her outward a hundred feet, then reduced her forward momentum and turned her around with Poole facing the ship.So he began to walk along the air pressure of the ship.

His first target was a melted site about half an inch in size, with a small pit in the center.The dust that hit this place at more than a hundred thousand miles per hour must have been no bigger than the tip of a needle, and its enormous kinetic energy immediately sublimated it into gas.As so often happens, the crater looked as if it had been formed by an explosion inside the ship; at such speeds matter behaved strangely, and common sense laws of mechanics often did not apply. Poole inspected the spot carefully, then sprayed the spot with a sealant from a pressurized container from the capsule's standing toolbox.The white jelly liquid spread on the metal skin, covering the small pit.The air coming out of the hole blows up a big bubble, which pops when it reaches six inches in size—and then a smaller bubble—and then the quick-setting cement kicks in, and the little bubble disappears.Poole stared for a few minutes until nothing moved.But just to be extra safe, he sprayed on a second coat; then turned to the antenna.

When he finally reached the distant antenna, he took a detailed look at the situation.The bowl, twenty feet in diameter, seemed to be aimed at the sun, for the earth was now almost in line with the sun's surface.So the antenna assembly and all its aiming posts were in the dark, hidden in the shadow of the great metal bowl. Poole approached from behind; he had been careful not to go in front of the bowl reflector, lest Betty cut off the radio beam and cause a temporary but unpleasant break in contact with Earth.He couldn't see any part of the equipment he had come to repair, so he had to turn on the bay's searchlight to drive out the shadows.

Underneath that little metal plate was the cause of the trouble.The metal plate was held in place by four locking bolts, and since the entire AE-35 was designed to be easy to replace, Poole estimated that there would be no problem. However, it was obvious that he would not be able to carry out this work if he remained in the space capsule.Not only was it dangerous to get too close to the delicate mesh antenna structure, but Betty's steering jet could easily bend the giant paper-thin radio reflector.He had to park the capsule twenty feet away, and he stepped out of the capsule himself in his spacesuit.It was much quicker to disassemble that part with his gloved hands than Betty's remote anyway.

He checked the various systems on the space suit, and when he was satisfied, he let the air out of the space capsule.As the air in Betty hissed and rushed into the vacuum, a layer of crystalline ice formed around him for a moment, and the stars in the sky seemed a little hazy for a short moment. Before he leaves the capsule, there is one more thing to do.He switched from manual control to remote control, handing Betty over to Hal to direct.This was a typical safety measure; although a strong, spring-loaded cord not much thicker than cotton thread kept him securely attached to Betty, the safest of safety lines had had accidents.If he needed the delivery vehicle and could call HAL right away, he would be a laughingstock himself.

The door of the cosmic pod popped open, and he floated slowly into the silent space, dragging the extended safety line behind him.Be calm - never act fast - stop and think - that's the rule of EVA.If everything is followed, there will never be any trouble. He grabbed one of Betty's outer armrests and removed the spare AE-35 part from her breast pocket.He didn't take the time to access any of the tools in the pod, since most of them weren't designed for human use.All the monkey wrenches and keys he might need are already attached to the belt of his spacesuit. With a slight push, he flung himself toward the gimbal roughly below.The big bowl lay between him and the sun like a huge dish.When he floated down along the two beams of Betty's searchlight, his figure formed strange shapes around him.But he was surprised to notice that on the huge radio reflecting mirror, there were dazzling bright spots of light.

He had been puzzled by the points of light for a few seconds as he moved silently, and then he understood what they were.During the voyage the reflector must have been pierced many times by tiny comets; what he saw was sunlight filtering through these holes.Because these small holes are too small, they do not substantially affect the performance of the entire system. Since he was moving very slowly, he had little forward momentum, so he stretched out his hand and grabbed the antenna bracket without bouncing back.He quickly hooked the safety line to the nearest hook; this would give him strength as he worked the tool.Then he paused, reported the situation to Bowman, and considered his next steps.

There was one small problem: he was standing—or rather floating—with his back to the light, and his own shadow made it difficult for him to see the AE-35 components.So he ordered Hal to flash the searchlight aside, and after a while of trial, he got uniform illumination from the reflection on the back of the antenna dish. He took a few seconds to examine the metal plate and its four wire-wrapped locking bolts.Then he said to himself: "Any repair without authorization will invalidate all the guarantees of the factory." He cut off the wire and began to loosen the bolt cap.The bolts were standard size, just the right size for the zero torque wrench he was carrying.When the bolt cap is rotated, the internal spring device of the wrench absorbs the reaction of the screw thread rotation, and the user does not need to twist in the opposite direction. The four bolt caps unscrewed effortlessly, and Poole stored them carefully in a handy pouch. (It is predicted that one day the earth will have a halo like Saturn, which will be completely composed of bolts, latches and even tools carelessly thrown away by space construction workers.) The metal cover is a bit difficult to take off, which made him worry for a while. It was cold-soldered; but after a few taps it came loose and he clamped it to the antenna bracket with a large alligator clamp. At this point, he could see the electronics of the AE-35 unit.It's a thin sheet, the size of a card, that fits into a slot just the right size.This part is held in place by two locking crosspieces, with a small handle, which makes it easy to remove. "Hal," Poole called over the radio, "I'm about to disassemble this part. Turn off all control power to the antenna system. " "Antenna control power cut off," Hal replied. "Start right away. I'll take this part out right now." The card-like sheet slid out of the groove without trouble; it didn't get stuck, and the dozen or so sliding points of contact didn't stick.In less than a minute, the spare part is installed. Poole, however, isn't about to take any chances.He gently pushed himself away from the antenna mount, just in case the big bowl lost control when plugged in.When he was safely out of range, he called to Hal, "New part works. Restore control power." "Power on." Hal replied.The antenna remained as motionless as a rock. "Make failure predictions." "The circuit is clear," Hal reported after only ten seconds, and in that split second he had performed as many tests as a team of inspectors could. "Well," said Poole with satisfaction, "close the lid now." Fifteen minutes later, on his way back to the space capsule warehouse by jet propulsion, he silently congratulated himself that he had completed a job that did not need to be reworked. On this point, however, he was woefully wrong.