ShuttlePower
External
Tank
The external tank (ET) contains
the propellant for the main engines. The ET also serves as the
structural backbone of the Shuttle vehicle. The ET is actually
two tanks in one; the liquid hydrogen (LH2) and the liquid oxygen
(LO2) tanks, joined by an intertank.
Diagram shows major components that make up the external tank.
The design includes
precision plumbing and sensors that
measure propellant levels in each tank.
ETs are manufactured by Lockheed Martin
at the Michoud Assembly Facility near New Orleans, Louisiana. The Michoud
facility is one of the world's largest factories, covering 43 acres
under one roof. Here, technicians take specially machined aluminum
panels and curve them to form the large "barrel" sections
of the tanks. Marshall and Lockheed are implementing a revolutionary
new welding technique - friction stir welding - which greatly enhances
the strength and quality of the ET's welded joints.
Workers in the foreground give an idea of the size of
a finished external tank as it is
towed to a barge
for transport from
Michoud to KSC. The ribbed section
in the middle is the intertank,
which joins the hydrogen and oxygen tanks.
Finished ETs are loaded on a barge and shipped across the Gulf of Mexico
and around Florida to Kennedy Space Center. They are then transferred
to the vehicle assembly building for integration with the rest of the
shuttle
vehicle.
The orbiter connects to the ET at three points, two at the bottom, and
one at the top. During launch, the orbiter pushes the tank upward by
the same joints. Fuel and oxidizer flow to the engines through two 17-inch
wide fuel feed lines.
Although the aluminum skin of the ET is less than 0.5 inch thick, it
holds more than 1.5 million pounds of propellant and withstands thrust
loads of 6.6 million pounds. If an aluminum soft drink can were expanded
to the size of an ET, it would be only slightly thicker than the tank's
skin.
Inside the Vehicle Assembly Building (VAB) at KSC, cranes
are used to
position
the huge external tank for mating to the orbiter.
Shortly after main engine cutoff, the ET is jettisoned
as the orbiter continues
into orbit.
The ET falls and breaks up over
a remote stretch
of the Indian Ocean.
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