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NASA probing space shuttle fuel leak

Posted on: Friday, 14 July 2006, 20:50 CDT

By Irene Klotz

HOUSTON (Reuters) - Astronauts aboard shuttle Discovery prepared to leave the International Space Station on Friday while ground control teams revamped landing plans to handle a small leak in one of the ship's power generators.

Managers believe the leak is inconsequential but because there is not enough proof, they are proceeding cautiously.

"It's a coin flip," said deputy space shuttle program manager John Shannon.

The shuttle has three power units needed to move the body flaps, speed brakes and other critical landing gear. It can safely land with just one, though two or more make for greater control, Shannon said.

One unit has a tiny leak, about six drops per hour, and NASA plans to test on Sunday whether the unit is safe for landing. If the leak worsens, Shannon wants the crew to dump the unit's hazardous hydrazine fuel -- even though engineers suspect a system using nonhazardous liquid nitrogen is the one leaking -- and land using just two power units.

"We don't have enough information to say whether the leak is hydrazine or nitrogen," Shannon said. "If it got bigger, it would be an issue. You just don't want hydrazine in the aft (engine compartment). You don't want it anywhere."

A space shuttle in 1983 returned with a fire in its engine compartment when a spray of hydrazine hit one of it's power units, which can reach temperatures of 500 degrees Fahrenheit.

Shannon said the key difference between landing with two power units instead of three is that the shuttle's landing gear would be released by firing explosive bolts rather than with hydraulic power. That should not affect the touchdown, he said.

NASA may also decide to divert the shuttle from its primary landing site in Florida to a backup runway at Edwards Air Force Base in California, where the weather is more stable and the landing strip more accommodating.

The shuttle is scheduled to end its 13-day flight on Monday morning.

Under any scenario, Shannon said there is little risk to the shuttle and its returning six astronauts. Germany's Thomas Reiter, who was launched aboard Discovery on July 4, will stay aboard the space station until late December.

The shuttle crew spent their last day linked up with the space station conducting a time-consuming scan of their ship's heat shield. They were looking for possible damage from micrometeoroids hitting the ship once it reached orbit.

The scan is part of NASA's effort to assess the shuttle's condition before it attempts the dangerous dive back through Earth's atmosphere for landing.

Earlier inspections found no damage from debris at launch.

The shuttle is scheduled to leave the space station on Saturday and scans for tiny meteoroid dents will continue after it undocks. If any damage is found, Discovery could return to the outpost to seek shelter or make repairs.

The shuttle Columbia broke apart in 2003 when superheated gases blasted into a hole in its wing as it re-entered the atmosphere. The hole was caused when debris fell off the fuel tank during launch and hit the wing. The fuel tank was redesigned but failed its first test-flight last year.

Discovery's July 4 launch proved the latest modifications to the tank were successful. The crew also repaired the space station's equipment transporter, which is needed for upcoming missions to resume construction of the $100 billion station.

Space station assembly was halted after the Columbia accident but is scheduled to resume with the shuttle mission scheduled for next month.

Source: REUTERS

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