A small ruler shows the relative size of the LH2 recirculation line in Space Shuttle Discovery's engine compartment.

A small ruler shows the relative size of the bent LH2 recirculation line in Space Shuttle Discovery's engine compartment. Underneath the line is material draped to protect other components. The 12-inch-long dent was discovered during routine aft compartment inspections Tuesday, Dec. 7. The LH2 line recirculates hydrogen from the Shuttle main engines back to the external tank during prelaunch engine conditioning. The line is being replaced and managers expect the replacement work to take about 3 days, followed by system retests and final aft compartment close-outs. Preliminary assessments reflect a launch date of Space Shuttle Discovery on mission STS-103 no earlier than Dec. 16. STS-103 is the third servicing mission for the Hubble Space Telescope