Dave-Platt%LADC@CISL-SERVICE-MULTICS.ARPA (Dave Platt) (03/07/86)
According to an article in the LA Times this morning, the presidential commission on the Challenger disaster reconvened yesterday to look over a large mass of data gathered during the last few weeks. The commission is focusing its attention on the possible causes for the apparent rupture in the SRB seals. Theories include: 1) The low temperatures compromised the ability of the O-rings to seal the inter-segment gap properly during the first second of SRB firing. This is the theory backed by the pre-launch warnings of several Morton Thiokol engineers. NASA experts have challenged this theory, suggesting other possible causes for the seal rupture. 2) An article in Aviation Week & Space Technology this week reports that the commission has heard evidence that ice might have formed in the failed joint before liftoff. Photographs of the launch reportedly show a white puff of steam at the suspect joint, .2 seconds after ignition and prior to a plume of black smoke from the joint. AW&ST said it is theorized that the steam was evaporating ice that had gathered in the lower section of the joint, which is U-shaped and theoretically could hold a small amount of water. In the 37 days that it sat on the pad, Challenger was exposed to at least six inches of rain, and sub-freezing temperatures for several hours on the eve of launching. NASA officials testified that three years ago, a trace of rain water was discovered to have collected in a solid rocket joint. NASA then began applying grease to the joints in an attempt to prevent water from entering. 3) The commission is also looking into the possibility that the O-rings in the suspect joint might have had an undetected defect, or that the assembly of the rocket was not properly conducted. There have been reports that the assembly of the section of rocked believed to have failed took several hours longer than usual, and these reports have raised questions about assembly procedures. Previous witnesses have told the commission that sections of reusable rockets don't always fit well when the rockets are reassembled. Most of the rocket segments used on teh Challenger mission had been flown in different combinations at least twice before.