VOA常速英语:Shuttle Endeavour to Deliver Space Station Module

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The space shuttle Endeavour is set for launch early Wednesday, after technicians resolved a hydrogen leak that delayed the first attempt. The new schedule has pushed back the launch of a separate mission to the moon.

The seven-member crew of Endeavour is set to deliver the final piece of a Japanese science laboratory and other supplies to the International Space Station. The first launch attempt was postponed after technicians discovered a hydrogen leak while the ship was on the launch pad.

The new schedule calls for Endeavour to lift off before dawn on Wednesday, the same day that NASA had hoped to launch a separate mission to survey the moon. Officials now say the lunar mission will launch as early as Thursday from the Kennedy Space Center in Florida.

Shuttle test director Stephen Payne said the lunar mission team agreed to allow Endeavour to take the launch pad, or range, on Wednesday.

"We will have one opportunity on the 17th [of June], and then stand down and allow them [the lunar mission] to play through. The [shuttle] vehicle will be ready for multiple attempts; our only constraint is [launch] range," said Payne.

Payne said that if this attempt fails, the Endeavour team will have to wait until mid-July to try again.

He said technicians are confident that they have fixed the hydrogen leak, which was found while NASA crews were filling the shuttle's external fuel tank. The same problem delayed the launch of Discovery in March.

Payne said technicians found that seals on the hydrogen vent lines were out of alignment and they installed new ones to fix the leaks.

"What's causing that misalignment is what we really have to go after. Because if we can keep the alignment straight then the seals work fine. It's between the mating and de-mating that we get the misalignment problem," he said.

The Endeavour mission includes plans for five space walks to install the Japanese science module and perform other tasks at the space station. Astronaut Tim Kopra will travel to the station to replace Koichi Wakata, who will return to Earth aboard the shuttle.