NASA starts repairs of space shuttle launch pad

BEIJING, June 30 (Xinhuanet) -- NASA has started
repairing a damaged Florida launch padin preparation for the October
launch of space shuttle Atlantis in a mission to repair the Hubble Space
Telescope.

The intense pressure from space shuttle Discovery's
May 31 launch tore bricks from the wall of Launch Pad 39A's flame trench and
sent some pieces flying at supersonic speeds, but NASA officials said that the
incident did not pose a threat to the space shuttle or its launch schedule.

"It's not a flight issue at all," said Rita
Willcoxon, space shuttle processing manager, during a Thursday teleconference
where she and other officials laid out the results of NASA's investigation and
repair plans.

NASA engineers found that time and environmental
effects had eroded the adhesive materials holding a layer of heat-resistant
bricks against the east wall of the flame trench. Vibrations during Discovery's
launch caused that layer to bend outwards slightly, and allowed a hot gas plume
to enter behind the bricks.

"Due to interlocking nature of the bricks, that led
to cascading failure," said Perry Becker, head of the Engineering Investigation
Team.

The thrust from Discovery's engines blasted 3,500
bricksfrom the wall and left them strewn across 1,500 feet (457 meters)
between the flame trench and the pad's perimeter fence. However, simulations run
by the engineers showed that none of the bricks flew up near the pad surface,
and therefore posed no possible risk to the space shuttle.

Erosion has similarly taken its toll on the intact
west wall of the flame trench. NASA crews plans to work with an outside
contractor to repair the damaged east wall, but will also replace a 25-foot high
by 80-foot wide section of the west wall's bricks using a spray-on, heat
resistant material.

NASA has two launch pads for Atlantis and the
remaining shuttle missions, but will need both ready for the Hubble repair
mission in case a second shuttle must fly on a rescue mission. That's because
Atlantis will have to fly to a higher orbit than normal to reach the Hubble
Space Telescope, and would not have fuel to reach the safe haven of the
International Space Station during an emergency.

(Agencies)