NASA shuttle
managers decided Thursday not to test fuel the external tank that will feed the
Discovery orbiter during a planned
launch this July, space agency officials said.
Shuttle
managers have debated the fuel-loading test since
last month, when engineers opened
up the aft end of Discovery's Lockheed Martin-built external tank to replace
four engine
cut-off sensors inside its liquid hydrogen compartment.
Known as a
tanking test, the fuel-loading check operation involves pumping Discovery's 15-story
fuel tank with the 526,000 gallons (about two million liters) of super-chilled
liquid oxygen and liquid hydrogen into the orange vessel while it sits atop the
launch pad. The test would verify the performance of the new ECO sensors and allow
engineers a chance to see the changes made to ET-119's foam insulation covering
- the most noticeable of which is the removal
of a 38-foot (11-meter) ramp - under fully fueled conditions.
"There's a
cost to it in a lot of places and that's what they were looking at, the pros
and the cons," James Hartsfield, a NASA spokesperson with the agency's Johnson
Space Center in Houston, told SPACE.com, adding that the test could
reduce the contingency time at the pad for the planned space shot.
Discovery's
launch will mark NASA's second shuttle mission - STS-121 commanded by veteran astronaut
Steven
Lindsey - since the 2003
Columbia accident. The spaceflight is currently slated to launch on July 1,
but has a flight
window that stretches through July 19.
NASA
decided to swap
out Discovery's fuel tank ECO sensors with new ones in March after
identifying a wiring defect in similar units. The sensors are designed to shut
down a shuttle's three main engines before its fuel tank runs dry. They can be
checked during tanking tests or actual pre-launch fueling to verify that they
are working properly.
Last week,
shuttle managers also said that they would not
make additional changes to Discovery's external tank aside from the already
completed removal of a protuberance air-load (PAL) ramp that shielded a cable
tray and pressure lines.
During
Discovery's last launch - NASA's first
return to flight mission STS-114 - a one-pound (0.4-kilogram) piece of foam
popped
free from the ramp during the orbiter's ascent. While the foam debris did
not strike the orbiter, it was reminiscent the foam shedding problem that doomed
the Columbia orbiter and its seven-astronaut crew in 2003.
NASA's space
shuttle chief Wayne Hale said Friday that the PAL ramp removal marked "the
largest aerodynamic change" to the shuttle launch system since its first flight
25 years ago.
At NASA's
Kennedy Space Center (KSC) spaceport in Florida, preparations are underway to
move Discovery from its hangar-like Orbiter Processing Facility to the 52-story
Vehicle Assembly Building, where the shuttle's external tank has already
been mated to the two solid rocket boosters that will launch the spacecraft
into orbit, on May 12.
The
complete launch stack is also on track to roll out to the launch pad on May 19,
KSC spokesperson George Diller said.
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