Shuttle Endeavour's heat shield appears to be fine
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: July 17, 2009
While the analysis is not yet complete, a quick look at photographs shot during the shuttle Endeavour's dramatic pitch-around maneuver during final approach to the space station today show the orbiter's heat shield appears to be in good condition with no obvious signs of damage beyond two areas of coating loss spotted during launch Wednesday.
"The video from the docking and the RPM maneuver was stunning as always," said John Shannon, the shuttle program manager at the Johnson Space Center in Houston. "All of the photographs that the ISS crew took of the underside of Endeavour are in the process of being downlinked, I think we have all them on the ground, they're being reviewed.
"It's kind of funny, the only damage we see to the tiles on the vehicle is what we saw during the ascent from the LO2 feedline camera," he said. "The underside looked completely clean except for the three little spots we had from that first foam loss and that little line of, it looks like, tile top coat that was abraded off by the second foam (impact). So we didn't see anything down by the ET doors, or on the elevons or really anywhere else.
"The team is actively looking at those photographs of that chine area (where the known damage is located)," Shannon said. "It did not look (to be) of very big concern at all."
While Shannon was briefing reporters, the Endeavour astronauts were gearing up for a rocket firing to boost the shuttle-space station complex about a mile to avoid a piece of space debris that might otherwise have passed too close for comfort.
"We definitely will need to do a reboost," Janice Voss radioed from Houston. "We are expecting about two-and-a-half feet per second posigrade (rocket firing) and about 15 minutes reboost duration."
Lead Flight Director Paul Dye said he did not know how large the debris might be or what spacecraft might have been the source. Its catalog number is 84180.
Engineers will continue the heat shield photo analysis overnight and make a recommendation Saturday as to whether an additional, "focused" inspection might be needed later to collect additional data.
In another bit of good news for commander Mark Polansky and his shuttle crewmates, Shannon said engineers had completed an assessment of Endeavour's reinforced carbon carbon nose cap and wing leading edge panels, which experience the most extreme re-entry heating, and had not found any areas of concern.
"There were no issues at all with any of the wing leading edge panels or the nose cap," he said.
Endeavour's two solid-fuel boosters are being towed back to Cape Canaveral for disassembly and inspection. Shannon said cameras in each booster will be removed Saturday evening and engineers hope to begin reviewing the footage Sunday.
The booster cameras are expected to shed light on the unusual loss of foam insulation from the central "intertank" area of Endeavour's external tank, which suffered multiple losses during Endeavour's climb to space. While most of the intertank foam came off after the shuttle was out of the dense lower atmosphere, where it poses the greatest impact threat to the shuttle's heat shield, engineers want to understand what caused the unusual shedding.
The foam that caused the presumably minor damage in the two areas seen during launch Wednesday came off the tank right beside the 17-inch-wide liquid oxygen feed line that emerges from the side of the intertank. While that foam released earlier than the bulk of the intertank debris, Shannon said the same mechanism may be responsible.
Shannon said two teams are looking into the matter, one focused on what happened to Endeavour's tank and the other looking into what might be needed to ensure the next tank in the launch sequence is safe to fly.
External tank No. 132 is scheduled for use by the shuttle Discovery in late August and engineers are planning "pull" tests to measure how tightly bonded its intertank foam is to the underlying metal. Shannon said depending on what the tests show, the tank could be launched as is, repaired or taken off line and replaced by a follow-on tank.
Because the intertank foam separated relatively late in the ascent, it does not appear to represent the sort of impact threat that might suggest sweeping changes. But Shannon said it's too soon to say what impact, if any, the work might have on Discovery's launch campaign.
"We're still putting the plan together to go and do the plug pulls to ensure we have the proper adhesion," he said. "This is not dissimilar from previous work we've done when we've seen foam losses on other tanks. Right now, my expectation is this will not affect a late August launch of STS-128."
But NASA has delayed Discovery's move to the Vehicle Assembly Building for attachment to ET-132 and a set of boosters from Monday to next Friday to allow more time for testing. NASA's internal launch target remains Aug. 18, but that date already was in conflict with a Delta rocket launch and regardless of the upcoming testing, Discovery's flight likely will slip a few days.