CAPE CANAVERAL, Fla. -- Liberty Star, one of NASA's solid rocket booster retrieval ships, tows the right spent booster from space shuttle Discovery's final launch, to Port Canaveral in Florida.The shuttle's two solid rocket booster casings and associated flight hardware are recovered in the Atlantic Ocean after every launch by Freedom Star and Liberty Star. The boosters impact the Atlantic about seven minutes after liftoff and the retrieval ships are stationed about 10 miles from the impact area at the time of splashdown. After the spent segments are processed, they will be transported to Utah, where they will be refurbished and stored, if needed.