NASA has delayed the launch of the space shuttle Discovery for a fourth time amidst concerns about valves.

The space shuttle Discovery lands, ending Mission STS-124 to the International Space Station, at the Kennedy Space Center in Cape Canaveral, Florida June 14, 2008.(Xinhua/Reuters File Photo)

Managers want to make sure if that happens again, the shuttle and its seven-man crew would be safe.

Discovery’s latest mission to the International Space Station originally had been scheduled for Feb. 12. During a review of Discovery’s readiness for flight, NASA managers decided Feb. 3 to plan a launch no earlier than Feb. 19.

However, on Feb. 7, NASA announced that the launch would be no earlier than Feb. 22, citing concerns over a valve that keeps fuel flowing in Discovery’s main engines. NASA announced last Friday that Discovery’s liftoff was targeted for no earlier than Feb. 27.

Discovery’s 14-day mission will deliver the International Space Station’s fourth and final set of solar arrays, completing the orbiting laboratory’s truss, or backbone.

The shuttle also will carry a replace distillation assembly for the station’s new water recycling system.

VietNamNet/Xinhuanet