Posted: Tue, Apr 18, 2006, 8:02 AM ET (1202 GMT)
One of the three spacewalks previously planned for the STS-121 shuttle mission this year has been canceled because of scheduling constraints, NASA officials said Monday. The EVA was planned to test heat shield repair techniques that would be used if shuttle tiles or panels were damaged during launch. However, because of an overloaded schedule for the mission, in part because of additional shuttle inspections added to the original mission timeline, led shuttle managers to drop the EVA from the schedule to give the crew some additional time off in orbit. NASA could add the EVA back to the schedule if enough consumables, particularly hydrogen and oxygen used for the shuttle's fuel cells, remain to extend the mission's duration by a day. The shuttle Discovery is scheduled to fly the STS-121 mission in July.

Related Links:

•  CBS News/Spaceflight Now article
•  SPACE.com article