SP-425 The Martian Landscape

 

Manufacturing Problems

 

[17] From the very first day of camera construction it seemed that nothing was built without some defect. All parts had to be fashioned from a limited list of approved materials that would withstand the deep space and martian environments, and, in addition, would not outgas volatile organic materials that might lead to a false positive result from the biology instruments.

Batches of specially constructed electronic parts arrived from a supplier, and a check revealed that only four or five out of a hundred parts met the rigorous Viking requirements. Another batch arrived with similar results. Special supervisors from Martin Marietta and ITEK flew out to California to monitor each step in the construction of the parts. The yield increased, but rejected parts still outnumbered those that passed all qualification tests.

The elevation assembly that controlled the movement of the mirror proved an unexpected source of difficulty. The shaft was encased in ball bearings lubricated with a solid compound. After repeated mirror movements the lubricant built up at certain positions, disturbing smooth rotation of the shaft. A waiver from a general Viking rule was obtained. Because the elevation assembly was hermetically sealed, isolated from the rest of the spacecraft, a wet lubricant could be used in place of the troublesome solid lubricant.

The motor that drove the mirror was touted to be the ultimate in dependability. After long term operation, its innards were examined. The commutator brushes had essentially disappeared, ground down to nubbins. A frantic search for new brush materials was initiated. Finally a likely candidate an exotic mixture of high silver content carbon and molybdenum disulfide was discovered. A long term test showed negligible wear. Joe Fiorilla, the ITEK chief engineer, was not satisfied. Continue the testing. Can we stop now? Longer. So the motor ran on and on, far beyond the qualification requirements, a penance for all its former sins.

The most potentially devastating problem involved the tiny photosensor array (PSA). This was the single most critical component of the camera, the retina of our eye on Mars. ITEK had subcontracted the work to a company with special experience in this area of microelectronics. But as month followed month, there was nothing but bad news. Each time the sensor package was built up, parts would fail. Technicians, working under unusual tension, created inadvertent damage with a single false movement. Each miscue meant weeks of delays. To the scientists it began to appear as if the designers had overstepped the bounds of realistic possibility. In an ironic reversal of roles-it is usually the scientist who demands better instrumental capability and the engineer who adopts a conservative position-we urged the project engineers to incorporate a simpler photosensor array using only half the diodes. Fortunately our suggestion was shelved. The struggle went on, but time was running out.

At a tense meeting attended by all the chief managers of the Viking Project, an extraordinary decision was made. The contract with the ITEK supplier would be terminated, and all partly fabricated components would be sent directly to the Martin Marietta facility in Denver. There a special laboratory would be equipped to accomplish the work that had so far defied completion. Bizarre, inverted contractual relationships were forged to fit the special circumstances. NASA Langley built parts for the PSA and supplied them to Martin Marietta. That company built the PSA and furnished the units to ITEK. ITEK incorporated the PSAs into cameras and delivered them to Martin Marietta under the Viking contract let by NASA Langley.

It was a hazardous gamble. Important weeks were lost while the new Martin Marietta facility was prepared. Institutional rivalries were ignored-anyone who could help was called in. Bill Patterson, our team engineer with special background in this area of microelectronics, traveled from Brown University to Denver for a few days of consultation. Those days stretched into weeks; six months later he returned to Brown. Amazingly, by the time Bill was back at Brown, the photosensor arrays had been built. And they worked. A few months previously we would have settled for an array with one or two diodes inoperative. The components delivered to ITEK by the Martin Marietta task force were completely functional. Several units were shuttled back and forth between Denver and Boston for repair, but, at the time of final camera assembly, every diode in every assembly was ready to carry out its assigned task.

Early on, Viking managers at Langley devised a humbling technique for charting the progress of the program. The most grievous problems were assigned to the "Top Ten." At regular weekly reviews, the engineer with relevant responsibility was required to brief Jim Martin, Project Manager, on what progress had been made. More often than not, progress was backward.

Barely a year after the start of camera construction Glenn Taylor called me with the expected news-we had made the Top Ten. We tried to look on the bright side at least we wouldn't be laboring in darkness anymore. In fact, our early arrival on the Top Ten (something of a misnomer since the specially designated problems sometimes numbered up to fifteen) proved beneficial. We received helpful attention from a group of consulting engineers appropriately called the Tiger Team-before they were exhausted by the endless succession of problems that came later.

[18] The burden of manufacturing problems was especially heavy for the several Martin Marietta engineers who were permanently in residence at ITEK, coordinating contractual and technical affairs between the two companies. On the one hand, they were the daily recipients of strident phone messages from their home institution, asking them what the hell was going on, why nothing was being delivered on time and within cost. On the other hand, the ITEK personnel were less than delighted with the intrusions of outside observers-they recognized their problems clearly enough, without having others remind them of their deficiencies.

Vince Corbett was in charge of the Martin Marietta resident group at ITEK. One Friday afternoon, as I sat in his office listening to tales of misfortune, I urged him to take a day off. Why not drive down to Providencc the ITEK facilities were in nearby Boston-and spend the day sailing on Narragansett Bay? Vince accepted. He, his teenage son, and I spent a relaxing afternoon on our daysailer. It was one of those lovely crisp Indian summer days. Returning to the mooring, I made a poor approach. As the buoy drifted by to one side, Vince's son dove into the cold water to retrieve it. Somehow it seemed an appropriate end to our day of recreation-our mere association with Viking guaranteed that we would be dogged by misfortune.

One of the more vexing problems proved to have an unexpectedly simple solution. When the camera was operated in a special chamber cooled to the low temperatures prevailing on the surface of Mars the azimuthal drive jammed. When the temperature was raised the problem disappeared. Exotic electronic malfunctions were hypothesized, but common sense observations indicated the real problem. There was very little clearance between the upper camera housing and the fixed post against which the recessed window was stowed when the camera was not in use. As the temperature was lowered the post flexed and pressed against the upper housing. The clearance between post and housing was adjusted slightly and the problem never recurred.

Gradually, imperceptibly, the situation improved. The final fabrication of the cameras was accomplished virtually without incident. There were even a few moments of humor. A technician, carefully applying solder to an electrical junction, looked up to see a group of 18 visiting engineers and administrators standing around his workbench. The technician, unimpressed, remarked to the ITEK guide that it reminded him of the typical Viking philosophy-one person does the work and 18 others kibitz.


Ten engineers and technicians proudly surround their completed camera.

Figure 12. Members of the ITEK team dramatizing (some persons might say overdramatizing) an important event-delivery of the first camera to Martin Marietta. The upper and lower camera housings are distinguishable. The fixed post, attached to the top of the lower housing, is situated to the right of the recessed camera window.


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