NASA Tackles Late Fuel Tank for Shuttle Flight

A five-day delay in the arrival of a newly designed external tank is not expected to delay Discovery's May 25 launch.

However, the loss of time virtually eliminates days off for technicians, Discovery flow director Stephanie Stilson said.

External Tank 128, scheduled to arrive from the New Orleans factory on Thursday, was delayed by bad weather and is now scheduled to arrive Tuesday.

The tank has titanium brackets on the liquid oxygen feed line, soldered ECO-sensor connectors, a redesigned ice-frost ramp and minor changes to the metal structure.

Discovery is scheduled to be attached to the tank and a pair of solid rocket boosters on April 27 and then to roll out to the launch pad on May 5. That schedule leaves enough time to load the 37-foot Kibo science laboratory and perform last-minute checks on the spaceship and related systems.

"We feel confident," Stilson said.

To make room for Kibo in the payload bay, Discovery must fly without the 540-pound orbital sensing boom used to photograph the thermal tile to check for damage.

Endeavour, however, borrowed Discovery's boom for its current mission and will leave it at the International Space Station. After arriving at the space station, Discovery will pick up the boom and use it for inspections of the thermal tiles.

NASA's three shuttles share two inspection booms, and Discovery is rigged so the boom it picks up in space will work properly, Stilson said.

Discovery also has been equipped with new radiator hoses to prevent kinks that worried managers during Atlantis' last mission.

"We did a few cycles of the payload door," said Stilson. "It worked exactly how we hoped it would."

Also, Discovery's UHF radio is working fine. NASA managers considered borrowing Discovery's radio when Endeavour's radio would not function on its high-power mode. However, they decided that the radio's two low-power modes would suffice.

"We don't ever like to pull anything out of the ship," Stilson said. "If they had needed it, by all means, we would have taken it out of Discovery."

Tuesday's arrival of the updated external tank marks the incorporation of all the changes recommended since the Return to Flight in 2005.

The tank, which is 153.8 feet long and 27.6 feet in diameter, carries nearly 5,000 pounds of foam, which keeps ice from building up on the outside.

The tank modifications include less foam on the titanium brackets that hold the liquid oxygen feed line and modifications to foam on other parts of the tank. A piece of foam broke loose and smashed a hole in Columbia's wing during launch on the 2003 mission that ended in disaster.

Changes to the tank will not slow processing toward launch, Stilson said.

"I'm getting a very clean tank when it gets here," she said.

NASA is broadcasting Endeavour's STS-123 mission live on NASA TV. Click here for SPACE.com's shuttle mission coverage and NASA TV feed.

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