Shuttle set to return to flight after 2 1/2 years

By Deborah Zabarenko

CAPE CANAVERAL, Fla. (Reuters) – Shuttle Discovery was “go
for launch” on Wednesday in NASA’s first human space mission
since the fatal Columbia accident 2 1/2 years ago.

The U.S. space agency cleared the shuttle for fueling
before dawn, but a faulty heater delayed that process by more
than an hour. NASA officials said there was ample time to fill
the fuel tank and launch as scheduled at 3:51 p.m. (1951 GMT).

It was the second glitch in the final hours of the
countdown. On Tuesday, a temporary plastic window cover fell
from the roof of the cockpit and damaged two tiles near the
vehicle’s tail; these were replaced and NASA called it a minor
issue.

Weather was the main potential obstacle to an on-time
liftoff; an afternoon thunderstorm — common in Florida in July
– could force a delay. NASA forecasters predicted a 60 percent
chance of favorable weather, meaning no adverse conditions
within 20 nautical miles of the launch pad.

Discovery’s flight is meant to kick-start the stalled
construction of the International Space Station and to be the
first step on the road back to the moon and to Mars and beyond.

This flight begins the last chapter for the three-ship
shuttle fleet, which has been grounded since Columbia
disintegrated over Texas on Feb. 1, 2003, killing all seven
astronauts.

The shuttles are set to retire for good in 2010 after about
20 construction flights to the station. NASA’s new
administrator, Michael Griffin, said the shuttles will be
succeeded by a new generation of spacecraft and there is no
thought of extending the shuttle fleet’s service after that.

By 2010, Griffin said on Tuesday, the shuttles will have
been in use nearly three decades.

“That’s enough,” he said. “It’s time to take what we have
learned and move on.”

INHERENT RISKS

Even with all this experience, Griffin acknowledged that
the shuttles remain experimental test vehicles, and their
flights carry inherent risks.

Problems with the shuttle’s 2.5 million parts are not ruled
out on this mission and $1 billion and countless hours of
manpower spent to avoid a repeat of the Columbia disaster do
not eliminate the dangers of a shuttle mission.

Columbia tore apart on its re-entry into the atmosphere
because falling foam from the external fuel tank had knocked a
hole in its wing during liftoff 16 days before. When the
shuttle returned to the Earth’s atmosphere, superheated gases
ate into the breach.

NASA’s efforts since have been directed at minimizing the
possibility of falling debris and one of Discovery’s main tasks
will be to see whether those efforts have paid off, and to try
out experimental repair techniques if they have not.

The conditions Discovery and her crew, commanded by veteran
astronaut Eileen Collins, will face are daunting. Its two solid
rocket boosters will pour out 6.5 million pounds (3 million kg)
of thrust and enough energy to light 87,000 homes for a day.

Discovery’s other mission is to deliver needed supplies to
the International Space Station, a 16-nation project.

Construction of the station has been on hold since the
three remaining space shuttles were grounded after the Columbia
accident, and it has been run by a two-man skeleton crew.

The station will serve as a safe haven for shuttle
astronauts if Discovery is damaged and has enough oxygen, water
and supplies to accommodate the seven-person crew for about
eight weeks. It will provide the same function to the next
scheduled shuttle mission in September.

After that, Griffin said, shuttle missions will be on their
own because NASA will not be able to reserve a second shuttle
to act as a rescue craft and still keep to the station’s
construction schedule.

Under a new vision for space exploration announced in 2004
by President Bush, the shuttle’s return to flight and the
completion of the space station are essential steps toward the
shuttle fleet’s retirement.