The US space agency Nasa is preparing to make a fifth attempt to launch the space shuttle Endeavour, which has been delayed by bad weather.

The seven-member crew boarded the spacecraft despite forecasts giving only a 40% chance of favourable weather conditions at Cape Canaveral, Florida.

Nasa said the launch was scheduled at 1851 local time (2251 GMT).

Earlier launches were called off because of lightning strikes around the launch pad and over hydrogen leaks.

Meteorologists are predicting further heavy showers and lighting near the launch site on Monday and over the next couple of days.

However, Nasa spokesman Allard Beutel said the agency was "going to give it a shot".

New experiments

The Endeavour crew is set to install an external platform on Japan’s space station lab, Kibo.

The orbiter 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 during the mission.

Their arrival will bring the total crew on the outpost to 13 – a record for the International Space Station (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, the 29th to the station, the 23rd for Endeavour and the third in 2009.

Seven further flights to the platform remain before the shuttles retire in 2010.</p

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