Houston, we have another problem on 'Discovery'

Astronauts on the Discovery space shuttle have spent seven hours meticulously examining and repairing the surface of their craft in the hope of avoiding disaster on re-entry.

As well as filling cracks in the shuttle's heat-resistant tiles, they and their controllers at Nasa headquarters in Houston found another potential problem: a couple of short strips of filler material dangling between the thermal tiles that might pose a risk in the intense heat Discovery will experience as it comes back into the Earth's atmosphere.

Nasa officials have not decided what to do about the strips, neither longer than an inch. The astronauts might be asked to cut them, pull them out or try to shove them back in on their next spacewalk on Wednesday.

It is not unusual for shuttle flights to return to Earth with drooping pieces like this, Nasa said.