US space agency Nasa is confident that the space shuttle Discovery will make a safe return to Earth despite a possible problem which occurred on take-off.
Some scientists believe a piece of foam from a fuel tank may have hit a wing of Discovery after breaking away when the vehicle took off on Tuesday.
But Nasa officials are split on whether or not the foam actually made contact.
Discovery - which is visiting the International Space Station - is expected to return on 7 August.
SHUTTLE RETURN TO FLIGHT
Mission known as STS-114
Discovery's 31st flight
17th orbiter flight to ISS
Location: Kennedy Space Center, Launch Pad 39B
Discovery crew: Collins, Kelly, Noguchi, Robinson, Thomas, Lawrence and Camarda
In 2003, the space shuttle Columbia broke up as it re-entered the Earth's atmosphere. It later turned out that it had been damaged by a piece of foam.
Nasa has stopped all shuttle fights until the problem can be sorted out.
"We are trying to get it down to a level that cannot damage the orbiter," said a Nasa spokesman.