This story was updated at 9:03 p.m. EDT.
HOUSTON -- NASA officials have grounded the agency's remaining space shuttles after the Discovery orbiter's external tank shed chunks of foam, including one piece more than 2 feet long.
The problem is similar to what occurred in the disastrous Columbia flight in 2003 and was thought to have been fixed.
Space shuttle officials said that while there is currently no indication the foam contacted the Discovery orbiter, the incident should not have happened in the first place and is reason enough to put a hold on future flights.
Images taken of the external tank in orbit identified the foam separation, and also detailed additional areas where the material pulled loose from its tank, they said.
"Until we've fixed this, we're not ready to fly," said Bill Parsons, NASA's space shuttle program manager, during a press briefing here at Johnson Space Center. "You could say that we're grounded."
The Discovery orbiter and its STS-114 crew launched into space Tuesday morning and are approaching the International Space Station (ISS), where they will dock early Monday.
It is NASA's first shuttle to fly since the loss of the space shuttle Columbia in 2003, which was fatally struck by falling foam debris during launch. The briefcase-sized foam chunk hit Columbia's left wing back then, gouging a hole in its heat shield that led to the orbiter's destruction -- and the deaths of all seven astronauts aboard -- during reentry on Feb. 1, 2003.
The foam shed during Discovery's Tuesday launch originated on a protuberance air load (PAL) ramp that juts out from the orange external tank and protects vital cables, wiring and pressure lines running along its length. Current estimates place it between 24 and 33 inches long at its longest point and up to 8 inches wide.
'We need to do better'
NASA has spent two-and-a-half years redesigning portions of the shuttle's external tank to prevent exactly such foam loss, and early discussions on the need to address the PAL ramp -- which is swathed in thick foam layers -- ended with engineers believing no changes were needed. External tank project manager Sandy Coleman said the modifications had resulted in "the safest, most reliable tank we have ever built" for the shuttle program when the first of three new units were delivered to NASA's Kennedy Space Center in January 2005.
The tank used by Discovery in Tuesday's launch was the second of those tanks delivered.
"We need to do better than this," said Wayne Hale, deputy shuttle program manager, during the briefing, adding that it was fortunate the incident occurred when it did. "If this had happened earlier, it would have been bad."
Because of Discovery's high altitude at the time of the PAL foam loss, there was not enough air to sweep it back fast enough to impact the orbiter, Hale added.
The space shuttle Atlantis, being prepared to launch in September, will not fly before shuttle engineers fully understand and address the PAL ramp foam loss, shuttle officials said, adding that they did not know if any fix could be implemented in the next month, three months or by the end of the year. Discovery was slated to fly after Atlantis.
NASA's third, and last, remaining shuttle -- Endeavour -- is currently in its major modification period.
Today's announcement came at the end of a day in which Discovery's astronaut crew spent hours conducting a methodical inspection of their spacecraft's nose cap and wing leading edges using a new orbital boom sensor system (OBSS). Capped with a video camera laser sensors, the boom is designed to inspect the shuttle's vital reinforced carbon carbon panels and heat-resistant tiles that safeguard the orbiter and its crew from the extreme heat of reentry.
"We feel very confident of Discovery's thermal protection system, but we are looking into this," Parsons said.
Additional foam loss, known tile damage
Handheld images taken by the STS-114 crew of the external tank also revealed other incidents of unexpected foam loss.
In addition to the PAL ramp incident, a chunk of foam separated near the tank's bipod structure, where its connected to the forward section of Discovery. Shuttle officials made modifications to the foam application in that region, and were surprised to see foam loss there, Parsons said.
"We need to take another look at that," he added.
A short distance beneath the bipod, in a region known as acreage foam, another small divot appeared. Acreage foam is applied to the external tank by machine, a process NASA engineers made no changes two in the last two years.
"Personally, I'm disappointed," Parsons said of the foam loss, but added that it was advantageous that it occurred without harming Discovery. "We learned something. What if this hadn't happened and we flew five, six or seven [missions] down the line?"
NASA already knew they had a chipped tile near Discovery's nose landing gear doors.
Hale said that images taken by an external tank-mounted video camera caught the small chip flying off Discovery during the launch. Also in the image was a small white area on the shuttle's belly that will be an "area of interest" when the orbiter exposes its underside to the space station astronauts for photographs.
"Are we concerned? We're treating it very seriously," Hale said of the apparent tile damage. "Are we losing sleep at night? Not yet."
The STS-114 crew will likely train the cameras aboard the orbital boom sensor system on the chipped tile region during a three-hour block of time on July 29 already set aside for follow up inspections to Discovery's thermal protection system, Hale added.
The crews of both Discovery and the International Space Station -- where two astronauts plan to take extremely high resolution images of the shuttle's tile-covered belly early Thursday - have been notified, and data packages uplinked to their vehicles for analysis, Parsons said.
"They were very glad to get [the data] and there will be more discussions about it tomorrow," Parsons said.
While no new space shuttles will fly for the time being, NASA will not stop preparations for the follow-up to Discovery's mission, the STS-121 spaceflight aboard the Atlantis orbiter. Atlantis is already mated to its own external tank-solid rocket booster launch stack, and was slated for a Sept. 9 liftoff before today's foam find. NASA also tapped Atlantis to serve as a rescue ship for the STS-114 crew in the remote chance Discovery were too damage to return home and its astronauts forced to take shelter aboard the space station. That contingency rescue mission is known as STS-300.
"We think the need for an STS-300 is remote at this time," said Wayne Hale, deputy shuttle program manager, during the briefing.
But Parsons said that should it be needed, the decision would be "very difficult."
Meanwhile, Discovery's crew was sleeping Wednesday evening and is expected to awaken at 11:39 EDT (0339 GMT) and prepare to dock at the ISS. That docking is slated for 7:18 a.m. EDT (1118 GMT) on July 28.
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