The Shuttle Discovery remains on schedule for launching in the window opening July 1. Concern about the foam-shedding issue on the external tank (ET) has not abated, however. As ET chief John Chapman at Marshall Space Flight Center puts it, "Foam will come off. There is no way around that. It's the very nature of the material and the way that we use it and the way we apply it." The question is whether the shedding has been reduced to the point that the risk to the vehicle is acceptable. What constitutes an acceptable risk, of course, remains an area of subjective judgment.
There is no way flying such a complex vehicle will ever be "safe" in the sense of "no risk." As Shuttle program manager Wayne Hale said, "If you're not scared when we fly the shuttle, you're not understanding what's going on." He does say, "In terms of the foam, we are so much smarter this year than we were last year."
The most extensive array of cameras and sensors ever used to monitor a space launch will try to make everyone smarter.
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COMMENT: For all the technology and engineering brainpower being thrown at this problem, it bothers me that NASA is essentially flying four versions of the tank on succeeding flights: the "old" ET carried on the fatal Columbia flight (STS-107), the modified one used on last year's "return to flight" Discovery mission that resulted in more (although not deadly) foam events (STS-114), the one being used on this flight (STS-121), and the one slated for the shuttle Atlantis on the next flight (STS-116), which will have further modifications already decided on. It's not clear to this non-engineer that the accumulation of data from flying four designs isn't so complex it could actually conceal a problem rather than spotlighting it.
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