In the case of line defect, if the closed path can be continuously deformed into one point, the defect is not stable, and otherwise, it is stable.
12.
A fuel line defect during the launch has been traced to a faulty sensor . . . and NASA engineers are investigating a malfunctioning power unit-called an APU . NASA officials say this may shorten the mission to pick up Shannon Lucid from the Mir space station.
