The space shuttle Endeavour has launched into the skies above the Kennedy Space Center, rocketing Canadian astronaut Julie Payette towards the International Space Station.

Endeavour blasted off from the Florida launch pad Wednesday at 6:03 p.m. ET, and it will take about two days to reach its destination.

NASA had previously scrubbed the launch five times, most recently because of lightning storms in the area. The record for most delays in a shuttle launch is seven.

But NASA managers were quick to strike a cautious tone as launch video showed eight or nine pieces of foam insulation came off the external fuel tank during liftoff.

The shuttle was hit two or three times about two minutes into the flight, Bill Gerstenmaier, NASA's space operations chief, said.

Mission Control told astronauts of the damage, and said it looked to be less extensive than damage during the last liftoff.

Viewing launch video for debris strikes has been standard prodcure since the Columbia disaster.

Zoom-in photos will be taken when the shuttle docks at the space station Friday.

"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. But we have the tools in front of us and the processes in front of us to go clear this vehicle for entry" later this month.

Astronaut Mark Polansky was cautiously optimistic before Wednesday's launch, writing on his twitter feed at Astro_127: "Hope next tweet is from orbit. We'll see."

Canadian astronaut Chris Hadfield watched the shuttle take off in Florida and told CTV News Channel it was a "visceral" experience.

Endeavour's launch marks a historic moment for Canada: With astronaut Robert Thirsk currently aboard the space station, it's the first time two Canadians have been in space at the same time.

Thirsk arrived at the space station last month for a record-breaking six-month stay.

Canadian Space Agency President Steve MacLean says the Canadian rendezvous aboard the space station is a "big deal."

"It is an amazing feeling to have a place to go and to meet someone from your own country -- that's got to top it by an order of magnitude," MacLean said.

This is Payette's second time in space. She was a crew member aboard Discovery in 1999.

"There's nothing routine about standing next to the spacecraft or being strapped in; it's an immense privilege and it's quite awesome," Payette said in a cellphone call shortly before lift-off.

"It's an absolutely magnificent vehicle; it's incredible."

Payette and Polansky are among seven crew members travelling aboard Endeavour. The crew also includes the 500th person to ever fly in space -- mission specialist Chris Cassidy. He gets the honour because of where he's seated in the shuttle.

If Endeavour had not launched Wednesday, it would have been delayed until at least July 27t=, to accommodate for a Russian supply mission to the orbiting station.

The launch was scrubbed twice in June because of hydrogen gas leaks, and three times this month because of thunder storms in the area.

Space educator Randy Attwood says NASA was concerned about two things: lightning and maintaining a dry landing strip.

After the Apollo 12 rocket was hit by lightning twice during its launch through a relatively benign rainstorm, NASA realized that the rocket plume itself can generate its own electricity.

"They have a strict rule now that they can't have any kind of lightning within 30 kilometres of the launch pad," Attwood explained.

The other concern was the landing strip. If, for some reason, the shuttle had to turn around and land within 25 minutes of launch -- which has never happened before -- it can't fly through rainstorms, Attwood said.

"That would just shear off its protective tiles, which make the aeronautical shape of the shuttle. So while flying through a rainstorm in a regular airplane is no problem, for the shuttle it would be a disaster,' he said.