Nasa engineers are urgently trying to discover whether the space shuttle Endeavour was damaged when nine chunks of foam insulation broke off the fuel tank during lift off on Wednesday night.
Last night members of Endeavour's crew, including the schoolteacher-turned-astronaut Barbara Morgan, conducted a minute inspection of the shuttle's most vulnerable areas in search of possible damage.
Foam damage has been a concern for Nasa since a chunk pierced the space shuttle Columbia's left wing during take off in January 2003, leading to its destruction on re-entry into the earth's atmosphere, killing all on board.
In America's latest space mission nine pieces of foam insulation broke off Endeavour's fuel tank during lift off, and three pieces appeared to strike the shuttle, said John Shannon, chairman of the mission management team. None is believed to have been big enough to cause critical damage, he said.
Within hours, the shuttle commander Scott Kelly is due to guide Endeavour slowly toward the international space station. Then Endeavour will make a giant backflip so that crew members aboard the space station can zoom in for pictures of its belly and send them to Houston for analysis.
The first foam fragment came off at 24 seconds after lift off and appeared to hit the tip of the body flap. The second, and most troubling, detached itself 58 seconds after lift off, with a resulting spray or discoloration on the right wing. The third came almost three minutes after lift off, too late to cause any damage to the right wing.
"Whether it caused damage or not, we will find out in great detail" during Friday's rendezvous, Mr Shannon said last night.
"The report initially was that you got a spray of debris from this area and, of course, that brings up images of Columbia and the spray you saw there, and I would tell you this was not even remotely of the same magnitude."
The Endeavour mission has attracted extra attention because of the presence on board of Ms Morgan, 55, a former elementary schoolteacher from Idaho, who was Christa McAuliffe's backup for the inaugural teacher-in-space flight aboard the ill-fated Challenger mission in 1986.
McAuliffe never made it to space. She was killed along with her six crewmates when the shuttle exploded just over a minute after lift off.
Ms Morgan and the rest of the crew spent most of yesterday using Endeavour's robot arm and an extension boom to search the shuttle's wings and nose cap for damage. Working from the cockpit, they slowly swept the laser- and camera-tipped boom while engineers on the ground looked for cracks or holes.
The meticulous survey has been standard procedure ever since the Columbia disaster. The 50 ft boom, attached to the shuttle's 50 ft robot arm, was created expressly for the job.
"Hey, it's great being up here," Ms Morgan said last night, in her first televised update from space. "We've been working really hard, but it's a really good, fun kind of work."
After Mr Kelly completes Endeavour's backflip, the shuttle will come alongside and connect with the space station, while both vessels travel at 17,500 miles (28,000 km) per hour.
Endeavour's crew will then unload its major cargo - a two ton truss that will become part of the space station's backbone.
Nasa hopes to keep Endeavour in orbit for a full two weeks. The shuttle is equipped with a new system for drawing power from the space station. If it works, mission managers plan to extend the flight from 11 days to 14 days.
Ms Morgan was invited into the astronaut corps by Nasa in 1998. Now, finally in orbit, she plans to answer questions next week from schoolchildren and is flying 10 million basil seeds for eventual distribution to students and teachers.