The space shuttle Endeavour's astronauts inspected their ship for damage Thursday as NASA struggled to understand why a normally benign section of the fuel tank lost so much foam during liftoff.
The slow, tedious work unfolded as the shuttle rocketed toward the international space station for a Friday linkup. It was the first full day in orbit for the seven astronauts, who are delivering a veranda for Japan's enormous lab. It also happened to be the 40th anniversary of the launch of the first manned moon landing.
Shuttle program manager John Shannon said the thin layer of foam insulation on the central area of the tank peeled away in approximately 6-inch (15-centimeter) strips as Endeavour blasted toward orbit Wednesday. The green primer on the metal skin of the tank was exposed in places.
Fortunately, he said, the shedding from this area — the so-called intertank connecting the hydrogen and oxygen reservoirs — occurred well past the critical two-minute mark in the flight and posed no danger to Endeavour.
"We have a bit of a mystery," Shannon said. "We're not worried about this flight, but we need to understand what was going on for the next flight."
Some foam also broke off an adjoining area less than two minutes after liftoff and hit the underside of Endeavour, where the right wing joins the fuselage. That left a series of dings in the thermal tiles. Shannon said the damage looks to be less extensive than what occurred in practically the same place on the last flight. In all likelihood, it's merely coating loss and considered minor.
In all, more than a dozen pieces of foam came off the fuel tank during liftoff, at least two of which struck Endeavour.
"It was dramatic footage looking at it," Shannon told reporters.
Inspections on Thursday and Friday
Throughout Thursday afternoon, Endeavour's seven-member crew used a 100-foot (30-meter) laser-tipped boom to inspect their ship's heat shield, standard procedure ever since shuttle flights resumed after the Columbia accident. Columbia was destroyed during re-entry in 2003 because of a hole in its wing, left there by flyaway foam at liftoff.
But the boom could not reach everywhere, and NASA was going to rely on a complete photo survey of the shuttle, right before Friday's docking, to fill in the coverage gaps. The space station residents will use zoom lenses to photograph every angle of the shuttle as it performs a somersault for the cameras.
Any additional damage should show up in those photos. It will take several days, however, to sift through the data.
Endeavour will remain docked at the space station for nearly two weeks. During that time, the astronauts will install the third and final piece of the Japanese space station lab, a porch for outdoor experiments. Five spacewalks are planned.
Engineers, meanwhile, will conduct extensive testing of the fuel tank that will be used on the next shuttle flight in August. The investigation may involve X-raying the fuel tank and determining whether there are serious issues with cracks and fissures in the foam.
Shannon said it's too soon to know whether the glue beneath the intertank foam or some other material or process caused the problem. He would not speculate on whether the next mission might be delayed because of the extra checks or the effect if a bonding problem is found. The shuttle Discovery's mission to the space station is currently targeted for liftoff no earlier than Aug. 18.
NASA officials told NBC News that they did not think the foam problem would force a suspension of shuttle flights. "We will make sure that future external tanks are safe, but we are not grounding future flights," said one official, speaking on condition of anonymity.
This report includes information from NBC News.