CAPE CANAVERAL - Kennedy
Space Center technicians will take on a lengthy and unusual job today, one aimed
at getting inside a shuttle external tank to swap out suspect fuel sensors.
"It's not a trivial
process," said John Chapman, manager of NASA's external tank project at
Marshall Space Flight Center in Alabama.
"There are certain
risks involved," NASA shuttle program manager Wayne Hale added. "You
could damage the tank."
Delivered to KSC earlier
this month, the 154-foot-tall (47-meter) tank is hanging vertically inside the 52-story
Vehicle Assembly Building.
A
March 14 decision to replace
four fuel-depletion sensors in the bottom of the tank prompted NASA to
delay the planned launch of its second
post-Columbia shuttle mission from May to July.
The sensors serve the same
purpose as automobile fuel gauges and also provide a backup means of making
sure the shuttle's three liquid-fueled main engines shut down properly in
flight. A malfunction could prompt a premature shutdown, which could lead to a
risky and unprecedented emergency-landing attempt.
A failure also could allow
the engines to run dry, causing powerful turbopumps to seize up, break apart
and possibly prompt a catastrophe.
Technicians have built
scaffolding that will provide a work platform beneath the dome-shaped bottom of
the tank. A makeshift clean room also was put in place to make certain no dirt
or other contaminants get inside the tank.
The replacement work will
begin today as technicians start to remove foam insulation from a 3-foot-wide
(about one-meter) manhole cover bolted on the bottom of the tank. Later this
week, the cover will be taken off and a technician will climb inside.
The four sensors are on a
bracket attached to an internal shock mount that crisscrosses the bottom of the
tank. The technician will remove the bracket, replace it and then exit the
tank.
After the manhole cover is
bolted back in place, the tank will be hoisted out of the checkout cell and
onto a horizontal transporter in the center aisle of the assembly building.
The move will enable
technicians to reapply foam insulation on the bottom of the tank, a lengthy
process that involves spraying several layers of liquid foam and allowing each
to harden.
All in all, the sensor swap
is expected to take about 22 days.
"It takes time,"
Chapman said. "But it's a straight-forward process."
The change-out work will be
followed by the mating of the tank to a pair of 149-foot (45-meter) tall solid rocket
boosters that already are stacked on a mobile launcher platform in the assembly
building. The orbiter Discovery will be connected to the tank late next month.
NASA hopes to launch the
shuttle about July 1.
Published under license from FLORIDA TODAY. Copyright © 2006 FLORIDA TODAY. No
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