2001_ A Space Odyssey - Arthur C. Clarke [50]
But Poole was taking no 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 Hal: “The new unit should be operational. Restore control power.”
“Power on,” answered Hal. The antenna remained rock steady.
“Carry out fault prediction tests.”
Now microscopic pulses would be bouncing through the complex circuitry of the unit, 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 half a billion miles away. It was often impossible to see how solid-state electronic components could fail; yet they did.
“Circuit fully operational,” reported Hal after only ten seconds. In that time, he carried out as many tests as a small army of human inspectors.
“Fine,” said Poole with satisfaction. “Now replacing the cover.”
This was often the most dangerous part of an extravehicular operation: when a job was finished and it was merely a matter of tidying up and getting back inside the ship — that was when the mistakes were made. But Frank Poole 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 almost got away from him, he caught it before it had traveled more than a few feet.
Fifteen minutes later he was jetting back into the space-pod garage, quietly confident that here was one job that need not be done again.
In this, however, he was sadly mistaken.
Chapter 23
Diagnosis
“Do you mean to say,” exclaimed Frank Poole, more surprised than annoyed, “that I did all that work for nothing?”
“Seems like it,” answered Bowman. “The unit checks out perfectly. Even under two hundred percent overload, there’s no fault prediction indicated.”
The two men were standing in the tiny workshop-cum-lab in the carrousel, which was more convenient than the space-pod garage for minor repairs and examinations. There was no danger, here, of meeting blobs of hot solder drifting down the breeze, or of completely losing small items of equipment that had decided to go into orbit. Such things could — and did — happen in the zero-gee environment of the pod bay.
The thin, card-sized plate of the AE-35 unit lay on the bench under a powerful magnifying lens. It was plugged into a standard connection frame, from which a neat bundle of multicolored wire led to an automatic test set, no bigger than an ordinary desk computer. To check any unit it was only necessary to connect it up, slip in the appropriate card from the “trouble-shooting” library, and press a button. Usually the exact location of the fault would be indicated on a small display screen, with recommendations for action.
“Try it yourself,” said Bowman, in a somewhat frustrated voice.
Poole turned the OVERLOAD SELECT switch to X-2 and jabbed the TEST button. At once, the screen flashed the notice: UNIT OK.
“I suppose we could go on turning up the juice until we burned the thing out,” he said, “but that would prove nothing. What do you make of it?”
“Hal’s internal fault predictor could have made a mistake.”
“It’s more likely that our test rig has slipped up. Anyway, better safe than sorry. It’s just as well that we replaced the unit, if there’s the slightest doubt.”
Bowman unclipped the wafer of circuitry, and held it up to the light. The partly translucent material was veined with an intricate network of wiring and spotted with dimly visible micro components, so that it looked like some piece of abstract art.
“We can’t take any chances — after all, this is our link with Earth. I’ll file it as N/G and drop it in the junk store. Someone else can worry about it, when we get home.”
But the worrying was to start long before that, with the next transmission from Earth.
“X-ray-Delta-One, this is Mission Control, reference our two-one-five-five. We appear to have a slight problem.
“Your report