The shuttle Endeavour lifts off Wednesday from Kennedy Space Center in Florida. (John Raoux/Associated Press)The shuttle Endeavour lifted off Wednesday carrying seven astronauts, including Canadian Julie Payette, from the Kennedy Space Center in Florida en route to the International Space Station.

The shuttle launched at 6:03 p.m. ET despite earlier concerns that weather might again force NASA to postpone the mission.

A mounted camera on the shuttle Endeavour's detachable fuel tank shows the curvature of the Earth. (NASA TV)Watching from the ground at the space centre, fellow Canadian astronaut Chris Hadfield described the launch as "just perfect."

But video camera mounted on the shuttle's external fuel tank showed chunks of debris flying off the tank during the launch, hitting Endeavour's fragile heat shield.

"The bottom line is we saw some stuff," said Mike Moses, chairman of the mission management team. "Some of it doesn't concern us. Some of it you just can't really speculate on right now."

Engineers will need several days to evaluate launch imagery and perform other tests to ensure there are no problems, he added.

Poor weather conditions scuttled three earlier attempts to launch the shuttle on Saturday, Sunday and Monday. The discovery of potentially dangerous leaks of hydrogen gas thwarted back-to-back launch attempts last month.

Payette, who spoke to reporters by telephone shortly before she boarded the shuttle, said weather-related delays are the "nature of the game."

"We have to wait until [the International Space] Station goes overhead before we launch. That dictates at what time we go. Unfortunately, going in the middle of the afternoon in July in Florida is about as hard as it gets," she said.

2 Canadians in space

Canadian astronaut Julie Payette blows a kiss to the camera as she prepares to board the space shuttle Endeavour on Wednesday. (NASA TV)Endeavour's seven astronauts, including Payette, are scheduled to perform five spacewalks and complete the construction of the Japan Aerospace Exploration Agency's Kibo experiment module at the space station during their 16-day mission.

Payette, the flight engineer, will operate the shuttle's Canadarm 1, the space station's Canadarm 2 and a third mechanical arm that is to be installed on Kibo.

Payette is making her second foray into space; she was the first Canadian to visit the space station, in 1999.

All of the astronauts were ready to go and looking forward to carrying out the mission, she said.

"I can tell you there’s nothing routine about standing next to a spacecraft or [being] strapped in inside a spacecraft. This is an immense privilege, but it’s also quite awesome," she said.

The astronauts will catch up Friday with the space station, which was soaring more than 355 kilometres above the Pacific at launch time.

When they do, it will be the first time 13 people are together in space. Ten is the previous record.

The mission will also mark the first time two Canadians will be in space simultaneously. Robert Thirsk arrived at the space station in late May aboard a Russian space capsule for a six-month stay, the first time a Canadian has participated in a long-duration mission to space.

With files from The Associated Press