The agency is concerned that ice from a line could damage heat-shielding panels.
CAPE CANAVERAL, Fla. -- NASA made official Friday the expected delay of the space shuttle's return to flight, moving Discovery's launch from May until at least mid-July to deal with concerns about dangerous ice debris during liftoff.
NASA administrator Michael Griffin attributed the postponement to an ongoing analysis of the risk posed by ice breaking off the shuttle's external fuel tank, as well as several nagging technical issues that have cropped up in recent weeks.
"We are not going to rush to flight," Griffin said. "We want it to be right, so we're doing what we need to do to ensure that."
The main concern is a liquid oxygen propellant line that runs along the side of the tank. The line has joints, inside of which ice can form. One joint at the top of the line is a threat because ice shaken loose during launch can fall from there and strike heat-shielding panels on the orbiter's wings.
Shuttle Columbia broke apart in 2003 while re-entering Earth's atmosphere after a chunk of foam insulation fell from the tank and hit the leading edge of the orbiter's left wing during launch.
"We've come to the conclusion that we really need to do something about this ice," said Wayne Hale, NASA's deputy director of the shuttle program. "It is going to take us just a few more weeks to deal with that problem."
Two other spots on the tank, next to brackets that hold down the oxygen line and a pressurization line, also are being assessed. Engineers plan to eliminate the problem with the joint by adding a heater to prevent ice from forming. However, NASA must do some final testing on the heater before it is installed.