Watching the CAIB at workThe press conference: foam, bolts, tiles, and a possessed PowerPoint presentationAfter a brief break at the end of the public hearing (scheduled to end at noon but not wrapping up until around 12:30) board members reconvened for a press conference to discuss the status of the investigation itself. Ironically, although this was perhaps the most interesting part of the day—and the most newsworthy too, given the attention the press conference proceedings received in the media compared to the public hearing—the event was closed to all but credentialed media. (However, a few who hung around for the half-hour between the end of the public hearing and the beginning of the press conference could stay; security was only checking the credentials of those arriving at the auditorium for the press conference.) After some introductory remarks by Gehman and a few words by Ride about how a CAIB subcommittee is looking into NASA’s decisionmaking processes, it was Osheroff’s turn to discuss efforts to understand how the external tank’s foam could come off. There was a problem, though: Osheroff’s PowerPoint presentation wouldn’t display properly, jerking around the screen in a series of distorted shapes. This St. Vitus’ Dance appeared to be caused by an allergic reaction by the projector to Osheroff’s PowerBook, and was not resolved until he nearly finished his presentation. (The solution was not publicized, although one rumor claimed his presentation was moved to a Windows computer; the danger, perhaps, of thinking a little too differently.) Some reports attempted to draw parallels between his presentation, where he described tests performed on foam in a kitchen sink using red Mont Blanc ink, among other items, with Richard Feynman’s famous demonstration during the Challenger hearings of the inflexibility of O-rings at cold temperatures. The comparison is tempting: Feynman, like Osheroff, was a Nobel laureate in physics with few ties to NASA and willing to take novel approaches to the investigation. The parallels, though, can’t easily be extended. Feynman’s test was performed live, in full view of the cameras, and the results got to the heart of the cause of the Challenger accident. Osheroff instead summarized recent work performed back at Stanford University on a relatively complex topic: whether “cryopumping”, the aerodynamic heating of liquid nitrogen trapped in the foam, would cause the foam to shed. Osheroff’s tests showed that cryopumping causes two-dimensional flat cracks in the foam perpendicular to the surface, insufficient to causing shedding by itself, contrary to earlier claims by NASA. Osheroff suggested, though, that cryopumping could work in conjunction with something else—not specified—to cause foam to shed during flight. Most of all, it’s difficult envisioning the iconoclastic Feynman ever bothering to use Microsoft PowerPoint, let along have the tolerance to deal with a faulty presentation!
After Logsdon discussed work the board is doing on management and budget issues (as well as gently chastising reporters for publicizing a draft outline of the CAIB’s final report the previous week), Barry talked about work the board has done to close out “fault trees” in an effort to rule out alternative causes for the accident. This was when Barry and the CAIB revealed the problem with the boltcatcher that was picked up by every media outlet. It was interesting to watch the media reaction to this announcement, as they scrambled to flesh out additional details as well as try to resolve some confusion over whether the bolt debris could be an alternative cause for the accident (it isn’t, as Barry and the board noted; among other things, an 18-kilogram bolt hitting the shuttle would cause a lot more damage, and would be more easily noticed, than a chunk of foam weighing under one kilogram.) Barry also discussed a problem during the launch of STS-112 mission last year, when one of two signals designed to trigger explosive bolts in hold-down posts for the SRBs failed to fire. That problem, though, got considerably less attention in the media, perhaps because that problem had previously been reported. After this press conference wrapped up, the board held a second press conference to discuss the recent foam impact tests on shuttle reinforced carbon-carbon (RCC) panels. (The CAIB referred to this event as a “Roundtable”, but it was functionally identical to a press conference.) Scott Hubbard showed images and high-speed video from the June 6 test where a piece of foam was fired at an actual shuttle RCC panel. The impact caused two cracks in the panel and one in an adjoining T-seal, as well as superficial damage to the upper carrier panel. Surprisingly, he noted, there was no damage to the surface of the RCC shell itself: the cracks were in the ribs and flanges of the panel, even though the impact exceeded the design strength of the panel.
Hubbard said that more foam impact tests were planned to better understand how the RCC panels could be damaged. Two tests are planned for this week using fiberglass panels, with a final test, using a different set of RCC panels, is planned for late June. There are no plans for additional foam impact tests, Hubbard said. Hubbard’s press conference wrapped up the day for the CAIB at about 3:30 pm, or six and a half hours after the public hearing started. Other than the boltcatcher problem (which is more a return-to-flight issue) there were no dramatic revelations nor any cutting insights into the Columbia accident and its underlying causes. Instead, one got to see members of the panel gradually assembling data and analyses that will eventually be incorporated into the report. Not the stuff of drama, to be certain, but the grunt work needed to understand the accident and make sure nothing like it happens again. Home |
|
