NASA will not attempt to fly space shuttle Discovery this year as it investigates what caused cracking in the ship's fuel tank during a launch try in November, officials said on Friday.
The next opportunity to fly Discovery on one of the shuttles' final cargo runs to the International Space Station likely will be in February, said NASA space flight chief Bill Gerstenmaier.
Until then, engineers plan tests to see if they can replicate the cracking that appeared following Discovery's Nov. 5 launch attempt.
"We've hit a point where there is no obvious answer to what occurred," shuttle program manager John Shannon told reporters.
With data analysis running dry, NASA will press ahead with two tests, one with tank components at the manufacturing site in New Orleans, and the other with shuttle Discovery at the launch pad at Kennedy Space Center in Florida.
"I have strong confidence this is a solvable problem," Shannon said.
NASA had planned to fly Discovery in November to deliver a storage room, spare parts and a prototype humanoid robot to the station and then launch Endeavour in February with the $2 billion Alpha Magnetic Spectrometer particle detector.
It also hoped to win congressional funding for a bonus mission, aboard Atlantis, over the summer.
That flight is needed to stash a year's worth of food, water and other supplies aboard the station, a $100 billion project of 16 nations that has been under construction since 1998.
The shuttles, which can carry about 50,000 pounds of cargo at a time, are being retired due to high operating costs. NASA plans to develop vehicles that can travel farther away from Earth than the station, which orbits about 220 miles (355 kilometres) above the planet.
NASA does not yet know how delaying shuttle Discovery's mission to next year will impact its request for the additional flight. The agency, like the rest of the U.S. government, is operating under temporary budgets pending congressional approval of a spending plan for the fiscal year that began Oct. 1.