Leo rotated the image so that each student could see it from every angle. “Now let’s magnify this part. You see the deep-V cross section from the high-energy-density beam, familiar from your basic welding courses, right? Note the small round porosities here…” the magnification jumped again. “Would you say this weld is defective or not?” He almost added, Raise your hand, before realizing what a particularly unintelligible directive that was here. Several of the red-clad students solved the dilemma for him by crossing their upper arms formally across their chests instead, looking properly hesitant. Leo nodded toward Tony.
“Those are gas bubbles, aren’t they sir? It must be defective.”
Leo smiled thanks for the desired straight line. “They are indeed gas porosities. Oddly enough, though, when we crunch the numbers through, they do not appear to be defects. Let us run the computer scan down this length, with an eye to the digital read-out. As you see,” the numbers flickered at a corner of the display as the cross-section moved dizzyingly, “at no point do more than two porosities appear in a cross-section, and at all points the voids occupy less than five percent of the section. Also, spherical cavities like these are the least damaging of all potential shapes of discontinuities, the least likely to propagate cracks in service. A non-critical defect is called a discontinuity.” Leo paused politely while two dozen heads bent in unison to highlight this pleasingly unambiguous fact on the autotranscription of their light boards, braced between lower hands for a portable recording surface. “When I add that this weld was in a fairly low-pressure liquid storage tank, and not, for example, in a thruster propulsion chamber with its massively greater stresses, the slipperiness of this definition becomes clearer. For in a thruster the particular degree of defect that shows up here would have been critical.”
“Now,” he switched the holovid display to one in red light. “This is a holovid of the same weld from data bits mapped by an ultrasonic pulse reflective scan. Looks quite different, doesn’t it? Can anyone identify this discontinuity?” He zoomed in on a bright area.
Several sets of arms crossed again. Leo nodded toward another student, a striking boy with aquiline nose, brilliant black eyes, wiry muscles, and dark mahogany skin contrasting elegantly with his red T-shirt and shorts. “Yes, Pramod?”
“It’s an unbonded lamination.”
“Right!” Leo tapped his holovid controls. “But check down this scan—where have all our little bubbles gone? Anybody think they magically closed between tests? Thank you,” he said to their knowing grins, “I’m glad you don’t think that. Now let’s put both maps together.” Red and blue melded to purple at overlapping points as the computer integrated the two displays.
“And now we see the little bugger,” said Leo, zooming in again. “These two porosities, plus this lamination, all in the same plane. You can see the fatal crack starting to propagate already, on this rotation—” The holovid turned, and Leo emphasized the crack with a bright pink light. “That, children, is a defect.”
They oohed in gratifying fascination. Leo grinned and plunged on. “Now, here’s the point. Both these test scans were valid pictures—as far as they went. But neither one was complete, neither alone sufficient. The maps were not the territories. You have to know that x-radiography is excellent for revealing voids and inclusions, but poor at finding cracks except at certain chance alignments, and ultrasound is optimum for just those laminar discontinuities x-rays are most likely to miss. Both maps, intelligently integrated, yielded a judgment.”
“Now,” Leo smiled a bit grimly, and replaced the gaudy image with another, monochrome green this time. “Look at this. What do you see?” He nodded at Tony again. “A laser weld, sir.”
“So it would appear. Your identification is quite understandable—and quite wrong. I want you all to memorize this piece of work. Look well. Because it may be the most evil object you ever encounter.”
They looked wildly impressed, but totally bewildered. He commanded their absolute silence and utmost attention.
“That,” he pointed for emphasis, his voice growing heavy with scorn, “is a falsified inspection record. Worse, it’s one of a series. A certain subcontractor of GalacTech supplying thruster propulsion chambers for Jump ships found its profit margin endangered by a high volume of its work being rejected—after it had been placed in the systems. So instead of tearing the work apart and doing it over right, they chose to lean on the quality control inspectors. We will never know for certain if the chief inspector refused a bribe or not, because he wasn’t around to tell us. He was found accidentally very dead due to an apparent power suit malfunction, attributed to his own errors made when attempting to don it while drunk. The autopsy found a high percentage of alcohol in his bloodstream. It was only much later that it was pointed out that the percentage was so high, he oughtn’t to have been able to walk, let alone suit up.
“The assistant inspector did accept the bribe. The welds passed the computer certification all right—because it was the same damn good weld, replicated over and over and inserted into the data bank in place of real inspections, which for the most part were never even made. Twenty propulsion chambers were put on-line. Twenty time-bombs.
“It wasn’t until the second one blew up eighteen months later that the whole story was finally uncovered. This isn’t hearsay; I was on the probable-cause investigating team. It was I who found it, by the oldest test in the world, eye-and-brain inspection. When I sat there in that station chair, running those hundreds of holovid records through one by one, and first recognized the piece when I saw it again—and again—and again—for the computer only recognized that the series was free of defects—and I realized what those bastards had done…” His hands were shaking, as they always did at this point of the lecture, as the old memories flickered back. Leo clenched them by his sides.
“The judgment of the map was falsified in these electronic dream images. But the universal laws of physics yielded a judgment of blood that was absolutely real. Eighty-six people died altogether. That,” Leo pointed again, “was not merely fraud, it was coldest, cruelest murder.”
He gathered his breath. “This is the most important thing I will ever say to you. The human mind is the ultimate testing device. You can take all the notes you want on the technical data, anything you forget you can look up again, but this must be engraved on your hearts in letters of fire.
“There is nothing, nothing, nothing more important to me in the men and women I train than their absolute personal integrity. Whether you function as welders or inspectors, the laws of physics are implacable lie-detectors. You may fool men. You will never fool the metal. That’s all.”
He let his breath out, and regained his good humor, looking around. The quaddie students were taking it with proper seriousness, good, no class cut-ups making sick jokes in the back row. In fact, they were looking rather shocked, staring at him with terrified awe.
“So,” he clapped his hands together and rubbed them cheerfully, to break the spell, “now let’s go over to the shop and take a beam welder apart, and see if we can find everything that can possibly go wrong with it…”
They filed out obediently ahead of him, chattering among themselves again. Yei was waiting by the door aperture as Leo followed his class. She gave him a brief smile.
“An impressive presentation, Mr. Graf. You become quite articulate when you talk about your work. Yesterday I thought you must be the strong silent type.”