The Discovery launch had to be postponed until Sunday, after a gaseous hydrogen vent line began leaking on Wednesday, during countdown. According to shuttle launch director Mike Leinbach, NASA workers will take a closer look at the vent line on Thursday afternoon.

Following initial assessments, the repair should take no longer than three days, making room for a possible launch attempt as soon as Sunday, but we will know more as soon as the inspection to the vent line takes place.

According to Leinbach, the leak developed on the piping that runs from the fixed service structure to a valve at the intertank section of the shuttle’s external tank. The shuttle was never in danger, he added, but the leak allowed for too much gaseous hydrogen to escape.

NASA has already been confronted with several delays of the Discovery mission, after last November one of the valves in shuttle Endeavour was found to have suffered damage after the  mission was over. All three valves that channel gaseous hydrogen from the engines to the external fuel tank have been removed, inspected and reinstalled back.

The Discovery flight’s mission is to provide the necessary support for the station’s crew of six, as well as deliver the needed arrays that will provide electricity for the scientific experiments to be carried on the station.

The STS-119 mission will include seven astronauts: pilot Tony Antonelli, Mission Specialists Joseph Acaba, John Phillips, Steve Swanson, Richard Arnold, Japan Aerospace Exploration Agency astronaut Koichi Wakata, and Commander Lee Archambault, in charge of the crew.