Weather forces NASA to postpone shuttle launch

By Irene Klotz

CAPE CANAVERAL, Florida (Reuters) - Heavy clouds near the Kennedy Space Centre forced NASA to call off Sunday's launch of the space shuttle Endeavour on a mission to deliver a Japanese-built porch to the International Space Station.

The launch was rescheduled for 6:51 p.m. EDT (11:51 p.m. British time) on Monday.

It was the fourth delay of Endeavour's flight. Two launch attempts last month were scuttled by hydrogen fuel leaks and a third try on Saturday ended when NASA ordered checks of the shuttle's electrical systems following a spate of lightning strikes at the launch pad on Friday.

The clouds moved into the area less than an hour before Endeavour's scheduled 7:13 p.m. EDT (12:13 a.m. British time) launch, with the seven astronauts strapped into their seats and the ship loaded with 500,000 gallons (1.9 million litres) of fuel to blast it into orbit.

Endeavour's primary cargo is a porch for Japan's $2.4 billion (1.48 billion pound) Kibo laboratory complex on the space station. The platform can be used to expose experiments to the open environment of space.

A small robotic crane will be able to retrieve and service experiments on the platform without time-consuming and potentially dangerous spacewalks by station crewmembers.

NASA launched the first section of the elaborate three-part complex in March 2008 and the second section two month later.

The porch is scheduled to be installed during the first of five spacewalks planned during Endeavour's 12-day stay at the outpost, a $100 billion project of 16 nations.