NASA is pressing ahead with last-minute repairs to the Discovery space shuttle in order to hit the planned November 1 launch date.
Engineers have discovered a small leak in a propellant line for Discovery's orbital maneuvering system engines.
The leak was found at a flange located at the interface where two propellant lines meet in the shuttle's aft compartment. The line carries a propellant called monomethyl hydrazine, one of two chemicals used to ignite the 6,000-pound thrust engines.
These are used for major course corrections while Discovery is in orbit, as well as to move the shuttle out of orbit to start the descent to Earth.
Engineers and technicians working on Discovery at Launch Pad 39A at NASA's Kennedy Space Center in Florida will try the simplest solution first: tightening the six bolts around the flange.
If the leak still persists, the propellants already inside the tanks will be pumped out and technicians will replace both the primary and secondary seals.
It's a more complicated job than it might at first appear, as the monomethyl hydrazine is highly toxic, and elaborate safety precautions will have to be taken. It's made harder by the fact that the shuttle is already in the vertical position.
NASA reckons there's enough time to replace the two seals and test the system without delaying Discovery's launch. If not, the flight will probably be delayed by at least a month because of clashes with other launches and spacewalks.
It's to be Discovery's last scheduled flight before the shuttle fleet is retired next year.
Sister ship Endeavour is due to make a last flight early next year, and a final mission for later next year has been passed by Congress and president Obama, and is awaiting final approval.