External Tank Fact Sheet

The External Tank, also known as ET:

  • Functioned as the “gas tank” for the Orbiter; it contained the propellants used by the Space Shuttle Main Engines
  • Three main components of the External Tank:
    • oxygen tank, located in the forward position,
    • hydrogen tank located in an aft-position, and
    • a collar-like intertank, which connected the two propellant tanks, housed instrumentation and processing equipment and provided the attachment structure for the forward end of the solid rocket boosters
  • the hydrogen tank was 2.5 times larger than the oxygen tank but weighed only one-fifth as much when filled to capacity
  • the difference in weight is that liquid oxygen is 16 times heavier than liquid hydrogen
  • Functioned as the “backbone” of the Shuttle during the launch, providing structural support for attachment with the solid rocket boosters and orbiter
  • At liftoff, the External Tank absorbed the total (7.4 million pounds) thrust loads of the three main engines and the two solid rocket motors
  • Most of the ET’s skin was covered with a thermal protection system that is a 2.5 centimeter (1-inch) thick coating of spray-on polyisocyanurate foam. The thermal protection systems acts to maintain the propellants at an acceptable temperature, to protect the skin surface from aerodynamic heat, and to minimize ice formation
  • ET was the only component of the Space Shuttle that was not reused. Approximately 8.5 minutes into the flight, with its propellant used, the tank was jettisoned
  • When the Solid Rocket Boosters separated at an altitude of approximately 45 kilometers (28 miles), the orbiter, with the main engines still burning, carried the External Tank piggyback to near orbital velocity, approximately 113 kilometers (70 miles) above the Earth
  • The empty tank separated and fell in a preplanned trajectory with the majority of it disintegrating in the atmosphere and the rest falling into the ocean
  • External Tank Stats:

            Weight:                        Empty: 65,000 pounds

                                                Propellant: 1,629,577 pounds

                                                Total: 1,694,577 pounds

            Propellant Weight:            Liquid oxygen: 1,391,936

                                                      Liquid hydrogen: 237,641 pounds

                                                      Total: 1,629,577pounds

            Propellant Volume:            Liquid oxygen tank: 143,351 gallons

                                                      Liquid hydrogen tank: 385,265 gallons

                                                      Total: 528,616 gallons