Lockheed Martin has successfully spliced together the final flight tank for space shuttle mission STS 133.

External tank 138 (ET-138) is a 154ft three-stage tank, weighing 58,500lb empty.

The components include a liquid oxygen (LO2) tank on top, a liquid hydrogen (LH2) tank at the bottom and an intertank in between.

ET-138 will undergo further processing at the final assembly area, and will be complete by June 2010.

The tank on the Discovery space shuttle will carry 534,000gal of propellant and weigh 1.7 million pounds.

Discovery is expected to lift off on its final space shuttle mission on 16 September 2010.