Debra Rahn
Headquarters, Washington, DC                      March 28, 1997
(Phone:  202/358-1778)

June Malone
Marshall Space Flight Center, Huntsville, AL
(Phone:  205/544-0034)


RELEASE: 97-58

SHUTTLE'S NEW LIGHTER, STRONGER EXTERNAL
TANK COMPLETES MAJOR PRESSURE TESTS

    The first new, super lightweight, external fuel tank for the
Space Shuttle is set for final assembly after successfully
completing proof pressure tests that verify its design.  The
achievement is a significant step toward the first launch of the
International Space Station.  The new external tank is the same
size as the one currently used on the Space Shuttle -- but about
7,500 pounds lighter.

    "Each pound we remove from the external tank is a pound that
can be added to the payload," said Parker Counts, manager of the
External Tank Project at the Marshall Space Flight Center,
Huntsville, AL.  "The lighter tank is essential for launching the
Space Station because the Station components will be assembled in
a more demanding orbit than previously planned."

    The 154-foot-long external tank, higher than a 15-story
building and as wide as a silo with a diameter of about 27 feet,
is the largest single component of the Space Shuttle.  The
external tank holds the liquid hydrogen and liquid oxygen
propellants in two separate tanks for the Shuttle's three main
engines.

    The two major changes to the external tank involve materials
and design.  Both the liquid hydrogen and the liquid oxygen tank
are constructed of aluminum lithium -- a lighter, stronger
material than the metal alloy used for the Space Shuttle's current
external tank.  The tank's structural design also has been
improved.  The walls of the redesigned hydrogen tank are
manufactured in an orthogonal waffle-like pattern, providing more
strength and stability than the previous design.

    "The new external tank has passed one of the most innovative
structural verification test programs ever designed, culminating
with these proof tests," Counts said.

    The proof test for the liquid oxygen tank was a hydrostatic,
or water pressure test.  The tank was placed vertically on the
test stand at NASA's Michoud Assembly Facility in New Orleans, LA,
and filled with water, which has similar density to liquid oxygen.
The tests simulated conditions encountered during flights and
validated the design changes.

    The liquid hydrogen tank was pressurized with gaseous nitrogen
and subjected to conditions simulating the thrust of the orbiter's
main engines and solid rocket boosters.  Tests checked the new
design by exposing the tank to harsher conditions than it will
encounter in flight.

    After the tests, comprehensive X-ray and dye penetrant
inspections will be performed to further verify the tank's flight
worthiness.

    The proof tests completed March 25 were the final in a series
of rigorous certification and structural verification tests.

    "Our team of dedicated employees -- both at Marshall and
Lockheed Martin Corporation -- completed the ambitious task of
designing and building the improved external tank and verifying
its design," said Counts.

    "All of this was achieved successfully on a tight schedule of
about three-and-a-half years.  They pushed the state of the art of
test technology, looking beyond current program requirements and
squeezing all the information possible out of each test to
understand the capability of the new tank," he added.

    After thermal protection foam is sprayed on its exterior, the
first super lightweight tank will be shipped by barge from
Louisiana to the Kennedy Space Center, FL, for its launch with the
first elements of the International Space Station.  The changes to
the external tank will not affect the assembly process when the
orbiter is mated to its tank and solid rocket boosters.

    The Shuttle's current external tank and the new super
lightweight tank are manufactured by Lockheed Martin.

                              - end -