The launch of the US space shuttle Endeavour has been postponed¹ for a fourth time, because of thunder storms in the area.

美国航天飞机奋力号因为该地区的雷电暴风天气第四次被推迟发射。

This was Nasa\'s fourth attempt to launch Endeavour

The decision was made only minutes before the shuttle was due to take off from Cape² Canaveral in Florida.

An earlier launch was called off after Nasa investigated lightning strikes around the launch pad while two were scrapped³（废弃） in June over hydrogen（氢） leaks.

The launch has been rescheduled for 1851 local time (2251 GMT) on Monday.

"Looks like the team is ready but the weather is not. At this time we are no-go," said Nasa's launch director, Pete Nickolenko.

The lift-off had been scheduled for 1913 local time (2313 GMT) from the Kennedy Space Center in Florida, some 24 hours later than planned.

Forecasters had said there was only a 30% chance of a weather-related delay.

It came after engineers spent Saturday checking over the shuttle's critical systems to ensure that there was no damage.

Experts said they found no damage to the shuttle or electrical systems after lightning struck 11 times near the launch pad at Cape Canaveral on Friday.

Two previous launch attempts in June were scrapped because of a potentially hazardous⁴（危险的） leak in a hydrogen vent⁵ line（通风管道）.

The crew is set to install an external platform on Japan's space station lab.

Nasa technicians have filled the ship with 500,000 gallons (1.9 million litres) of liquid oxygen and liquid hydrogen for the eight-and-a-half-minute ride into orbit.

New experiments

Endeavour is taking a seven-strong crew into space, made up of six Americans and one Canadian - Julie Payette - who will operate the shuttle's robotic arm（机械手） during the mission.

Their arrival will bring the total crew on the outpost to 13 - a record for the ISS.
 
During five spacewalks, a platform will be added to the Japanese lab complex, which can be used for experiments that require materials to be exposed to the harsh environment of space.

In addition, Endeavour will deliver a new long-stay US crew member, Tim Kopra, to the ISS and bring back Japan's Koichi Wakata, who has lived aboard the platform for more than three months.

The space station, now about the size of a four-bedroom house, has been under construction for more than a decade.

When it launches, Endeavour will make the 127th space shuttle flight, and the 29th to the station.

Seven further flights to the station remain before the shuttles retire in 2010.