NASA is marking a major step in assembling the Space Shuttle for its
Return to Flight mission. Monday, workers successfully “mated,” or
attached, the redesigned External Tank and twin Solid Rocket Boosters
(SRBs). The fuel tank and booster rockets will help launch Space
Shuttle Discovery on its mission to the International Space Station,
currently targeted for May 15-June 3.

The Space Shuttle’s External Tank was lifted by a giant crane and
joined to the already assembled, or “stacked,” boosters in the
52-story Vehicle Assembly Building (VAB) at NASA’s Kennedy Space
Center, Fla. Mating the tank with the boosters is another major step
in readying the Space Shuttle system for flight.

Following integration and final checkout of the External Tank with the
SRBs, orbiter Discovery will join its propulsion components in the
VAB. Discovery will roll over from its hangar, the Orbiter Processing
Facility, later this month to mark the completion of Return to Flight
processing. The orbiter then will be attached to the stack in the

The External Tank will fly with several modifications, including two
new forward bipod heaters at the forward attach fittings that connect
the tank to the orbiter. NASA and Lockheed Martin Space Systems Co.
spent nearly two years modifying the tank to make it safer.

During ET-SRB mating, the left and right boosters are bolted to the
tank at both the forward, or top, and the aft, or tail, ends. At the
forward end, a vertical bolt mechanism attaches each booster to the
tank. On launch day, approximately two minutes after liftoff, the
SRBs will separate from the ET when pyrotechnic devices fire to break
the 25-inch, 62-pound steel bolts. One half of the bolt is caught in
canister-like “bolt catchers” located on the tank; the other half
remains with the boosters.

Discovery will also be the first flight with a modified bolt catcher,
which was upgraded from a two-piece welded design to a one-piece,
machine-made design. By eliminating the weld, the modified bolt
catcher is structurally stronger than the original design.

Prior to orbiter Discovery joining the stack, final closeouts on the
External Tank will include attaching the new bolt catcher and
electrical cable connections, as well as installing an aerodynamic
fairing and the bi-pod struts, which are the attach points for the
nose of the orbiter to the tank.

The External Tank is the largest element of the Space Shuttle system,
which also includes the orbiter, main engines and SRBs. It measures
27.6 feet wide and 154 feet tall. Despite the tank’s size, the
aluminum skin covering it is only an eighth of an inch thick in most
areas. Yet it still withstands more than 6.5 million pounds of thrust
during liftoff and ascent. The tank is the only Shuttle component
that cannot be reused.

Photos of the External Tank mating operations can be found at the
following URL. Additional photos will be added to the page as they
are available.

Video b-roll will air on NASA TV beginning at 3 p.m. today on NASA
Television. NASA TV is available on the Web and via satellite in the
continental U.S. on AMC-6, Transponder 9C, C-Band, at 72 degrees west
longitude. The frequency is 3880.0 MHz. Polarization is vertical, and
audio is monaural at 6.80 MHz. In Alaska and Hawaii, NASA TV is
available on AMC-7, Transponder 18C, C-Band, at 137 degrees west
longitude. The frequency is 4060.0 MHz. Polarization is vertical, and
audio is monaural at 6.80 MHz. For NASA TV information and schedules
on the Internet, visit:

For the latest information on NASA’s Return to Flight efforts, visit: