Repairs to shuttle Discovery's right-side Orbital Maneuvering System helium system will delay the start of the STS-133 countdown to Sunday, with liftoff retargeted for 3:52 p.m. EDT Wednesday, NASA Test Director Jeff Spaulding said Saturday.
NASA initially expected repairs would delay launch one day, but the work turned out to be more complicated than anticipated. The leak was found late Thursday night as the OMS tanks were being pressurized for a launch attempt on Monday.
To access the couplings which needed to be replaced, technicians had to reconfigure valves, which entailed a door removal and some additional leak checks, Spaulding said.
"Thus far, we've vented down the tanks -- the intermediate and the final venting -- removed the doors, removed and replaced the air-and ground-half couplings and done some initial leak checks and some moisture checks and those came back good," he said.
Discovery's 39th and final flight is an 11-day mission, with one extension day possible, to deliver a logistics module, spare parts and supplies to the International Space Station. The crew plans to conduct two spacewalks for station maintenance and repairs.
Meteorologists forecast a 30 percent chance of a delay on Wednesday due to the possibility of rain and clouds.
"Overall, it isn't going to be a washout," said Kathy Winters, with the 45th Space Wing's Weather Squadron.
The launch window extends until Nov. 7, then closes until Dec. 1 due to sun-angle heating issues and then due to other activities at the station.
The STS-133 crew arrived at the Kennedy Space Center on Thursday.