The space shuttle programme’s final flight tank—designated External Tank-138—has completed a critical production milestone at the NASA Michoud Assembly Facility.
Lockheed Martin builds the External Tanks in New Orleans where its engineers and technicians mechanically spliced ET-138’s liquid oxygen (LO2)/intertank to the liquid hydrogen (LH2) tank, thus producing “a whole tank” for the first time in the production process.
The work is performed in Cell A in the 20-story-tall Vertical Assembly Building, and is the only time during production that the tank stands upright. Workers also completed foam “closeouts” on the LH2 to intertank flange.
An External Tank is actually three components in one. The 16.6m-tall bullet-shaped LO2 tank sits at the top. The 7m-long intertank separates the LO2 tank and the LH2 tank and does not hold fuel. Unpressurised, the intertank serves as the forward attachment point for the Solid Rocket Boosters. The bottom vessel is the 29.5m-tall LH2 tank. The LO2 tank and intertank are already spliced together when they enter Cell A.
Lockheed Martin employees loaded the tanks into the cell and completed the splicing and laydown of the tank in a record 40 days. The prior eight tanks averaged 60 days in Cell A.
ET-138 now proceeds to the Final Assembly area for more processing and is scheduled for completion June 29. When ET-138 is delivered to NASA, it will be 15 stories tall (47m), nearly 8.5m in diameter, and weigh 26.3 tonnes empty. When filled with 2,021,000 litres of propellant on the launch pad, the tank will weigh nearly 771 tonnes.
ET-138 is scheduled to launch with Space Shuttle Discovery (STS-133) on September 16—the final shuttle launch of the 29-year programme. ET-138 will help propel Discovery to orbit and then separate from the shuttle 8.5 minutes post-launch after Main Engine Cut-off or MECO.
ET-138 will be the 134th flight tank that Lockheed Martin has constructed for the shuttle programme.
Adapted from information issued by Lockheed Martin.