NASA to retest shuttle's fuel tank

[Guest Glenn]

Reuters

 

May 11, 2005

 

KENNEDY Space Center workers will conduct a second test of shuttle Discovery's fuel tank to determine why sensors critical for flight failed an earlier one, a NASA spokesman said on Monday.

 

The work was ordered after puzzling failures of two sensors that detect when the tank is filled with liquid hydrogen.

 

The problem is unrelated to another tank issue that had prompted managers to delay Discovery's launch from May to July and NASA is holding firm to its plans for a July launch.

 

The orbiter itself has been cleared as the cause of the hydrogen sensor problem, said Kennedy Space Center spokesman Bruce Buckingham.

 

"We're going to go back and redo the test since we have more time," Buckingham said.

 

The retest should narrow down the problem to either the sensors or faulty wiring, he said.

 

Discovery will not fly with its current fuel tank, no matter what the test results show.

 

NASA last week decided to install an additional heater on the tank to reduce concerns about ice building up on its outside, breaking off during launch and possibly striking the shuttle. The extra work forced NASA to delay Discovery's launch until July 13 at the earliest.

 

Managers later determined it would be faster to swap Discovery's tank and twin boosters -- which fly as a set -- for equipment being prepared for the next flight. Work to install the heater on that tank is under way, Buckingham said.

 

Although ice and foam from the tank have showered space shuttles since they began flying in 1981, the issue took on heightened importance after the loss of Columbia and its seven-member crew on February 1, 2003.

 

Accident investigators determined Columbia was destroyed because of a breach in its left wing -- damage caused by a piece of foam insulation that fell off the shuttle's fuel tank during liftoff. The damage left the shuttle vulnerable and it broke apart when it re-entered the atmosphere before landing.

 

NASA now plans to return Discovery to its assembly building before the end of May, then swap its tank and boosters with gear that had been earmarked for shuttle Atlantis. Atlantis, which needs to be nearly ready to fly at the time Discovery launches, will in turn get Discovery's tank, which will be outfitted with a new heater, and boosters.

 

NASA wants to have both shuttles available in case Atlantis has to be dispatched on a rescue mission, a scenario that would not have been possible for Columbia's crew, who were on a free-flying research mission out of reach of the space station.

 

After the Columbia accident, NASA decided to fly shuttles only to the space station, where the crew can seek shelter in case a ship was too damaged to fly home.

 

During the tank test, the shuttle is filled with 1.9 million litres of liquid oxygen and liquid hydrogen, just as it will be on launch day.

 

In order to make its next available launch period to the International Space Station, which opens July 13 and closes July 31, NASA has ordered around-the-clock work shifts, including weekends and holidays, Buckingham said.

 

"It's going to be tight, but it's doable," he said.