Discovery makes return trip to assembly building

Leaving the launch pad and rolling back to the Vehicle Assembly Building overnight, the space shuttle Discovery will spend the holidays having the external tank digitally X-rayed as engineers look to prove the hypothesis that its structural cracks resulted from pent up stresses accumulated during construction and were unleashed during the strains of cryogenic fueling. The crack problem dates back to Discovery's initial launch attempt Nov. 5 when a chunk of outer insulating foam on the external tank broke during fueling. The subsequent investigation revealed that two underlying U-shaped support beams in the tank's ribbed midsection had cracked, displacing the covering foam. More

(Source: Space Flight Now - Dec 23)