HOUSTON - One of several small pieces of foam that popped free from Discovery's external tank during launch may have struck the orbiter, but likely caused no significant damage, shuttle managers said Thursday.
"We think that little piece of foam at that altitude did not cause damage of concern," said Wayne Hale, NASA's deputy shuttle program manager, during a press briefing here at Johnson Space Center (JSC), adding that he fully expects the orbiter will be free of any debris concerns as data is processed. "I expect that on Flight Day 6, we're going to get the go ahead to fly as is."
Earlier today, NASA officials said they were confident that Discovery's heat shield is intact and the orbiter fit for an Earth return, but are awaiting additional analysis.
After two days of image analysis, analysts have tracked several small pieces of foam insulation as they popped free from the tank very near the origin of a larger, 0.9-pound chunk that missed Discovery as it fell, shuttle officials said.
They originated from an ice frost ramp, very close to another ramp that shed the larger foam chunk, and separated from the tank about 20 seconds after the bigger piece, Hale said. There is no definitive evidence - based on surveys conducted Wednesday with a sensor-laden orbital boom and sensors inside the wing - that the foam debris made contact with Discovery's right wing leading edge as it fell away, he added.
But even if the small foam piece did strike the orbiter, it would have hit with only 1/10th the energy needed to cause damage, according to debris transport analysis, Hale said.
Nevertheless, shuttle officials would like to know why the additional foam pieces fell away at all and will study the incident. NASA plans to address the current foam loss issue before launching another shuttle into space.
Discovery's STS-114 spaceflight is NASA's first shuttle flight since the 2003 Columbia disaster.
Hale said that Discovery's mission management team (MMT), which he chairs, will now hand off the external tank work to others and shift their focus onto verifying the shuttle's thermal protection system comprised of heat-resistant tiles and reinforced carbon carbon panels (RCC) along its wings and nose cap.
Earlier today, the STS-114 crew and space station astronauts worked together to photograph Discovery's belly, obtaining high-resolution images of the orbiter's belly-mounted tiles to be reviewed by specialists on Earth. The image survey came a day after Discovery's astronaut crew deployed the shuttle's 50-foot (15-meter) orbital boom sensor system (OBSS) to scrutinize the orbiter's wing leading edges for any hint of damage.
"We are very satisfied with the results we are getting," Hale said of the shuttle's tile-lined belly.
The measures are designed to search for damage like that which crippled the Columbia orbiter in 2003. The orbiter broke apart during reentry on Feb. 1, 2003, after suffering wing damage from external tank foam at launch.
Steve Poulos, NASA's orbiter projects office manager, said Discovery is a "very clean orbiter" that sustained about 80 percent fewer impacts than past shuttle flights.
The OBSS detected very slight scuffs to some of Discovery's RCC panels - one such incident leaving a mark smaller than the dot atop the letter 'i' - but additional passes are needed to catch every view flight controllers want, Poulos added.
In the history of the space shuttle program, most orbiter averaged about 150 nicks, dings or other damage to its heat-resistant tiles per flight, Hale said, adding that some of that damage admittedly occurred during descent as the landing gear deployed. Of that average 150 incidents, about 31 are typically larger than an inch in size, he added.
Shuttle tile specialists have picked out about 26 specific points where Discovery's belly tiles appear to have been dinged during flight. All but one of those - an apparently chipped tile noticed during video captured during launch - are smaller than 1/2 inch in size, and they are all expected to be cleared of concern by July 31, the sixth day of Discovery's STS-114 mission, NASA officials said.
Some of those tile dings may be chosen for follow-up looks with the OBSS on Friday, though tile specialists were still discussing that issue late Thursday, NASA officials said.
Meanwhile, Hale said he has sent e-mails to Discovery's crew expressing his concern for the foam shedding seen on launch day.
"I told them, frankly, that I was mortified of the external tank's foam loss, and that we're going to fix it before we fly again," Hale said.
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