Cloud halts shuttle return.

Byline: From RYAN PARRY, in Florida

ASTRONAUTS on space shuttle Discovery were told to sit tight yesterday as bad weather forced Nasa to delay their landing.

The craft is expected to attempt another landing early today at Kennedy Space Center in Cape Canaveral, Florida, after re-orbiting the Earth.

The crew were ready to land when low cloud forced Nasa to postpone for 90 minutes. At the second attempt cloud still covered the landing strip, forcing a rethink.

Mission Control told Discovery commander Eileen Collins: "We've been working this pretty hard as I'm sure you can imagine from our silence down here. We just can't get comfortable with the stability of the situation for this particular opportunity, so we are going to officially wave you off for 24 hours."

The shuttle, which launched on July 26, will again have two chances to land. Nasa is also considering Edwards Air Force Base in California and White Sands Missile Range in New Mexico as potential sites.

Nasa Administrator Michael Griffin said: "There's no agony. We're going to land one way or another, one place or another, and all we're talking about is where." Officials will want to stick to Kennedy to avoid the logistical nightmare of returning the shuttle to Florida, where they have the equipment to examine the data collected in space.

Discovery's return would have concluded the first shuttle flight since Columbia disintegrated on re-entry into the atmosphere in January 2003 when all seven crew died.

Before its approach, the shuttle flies upside down in orbit to stop it from overheatingIt turns tail first and the engines are fired to slow it before it re-enters the atmosphereIt is then flipped the right way up and enters the atmosphere at a 40-degree angleThe angle keeps thermal tiles facing the worst heat, which can reach 1,650C (3,000F)As speed drops, the shuttle uses wing flaps and rudder for control, banking to slow furtherThe shuttle falls fast from almost 220 miles up at a steep angle before finally stopping