Pilot: "the engine is still damaged, and we can't stop the gas tank leak completely."

Check toilets for silent leaks by putting a few drops of food coloring in the tank; if the color shows up in the bowl indicating a leak, fixing it may be as simple as replacing the toilet's flapper.

Discovery was hours from launching on it final voyage to the ISS on November 5 when technicians found a hydrogen leak and later a series of long cracks on the shuttle's external fuel tank.