NASA's Atlantis shuttle blasted off on Monday with a haul of spare parts for the International Space Station and some microscopic worms that could explain muscle loss in space.

The shuttle and its six astronauts left Florida's Kennedy Space Centre without a hitch for an 11-day voyage to deliver assorted gyroscopes, ammonia tanks and other equipment to the ISS.

"A perfect launch, right on time," said a spokesperson for the US space agency as the crew reached orbit ? hurtling at a speed of more than 15 000 miles per hour.

With only five launches left before the 2010 retirement of the shuttle fleet, NASA officials said the parts were essential for extending the life of the space station, where the crew is due to dock on Wednesday.

"This flight is all about spares, basically; we're getting them up there while we still can," said mission director Brian Smith, "you'll see this theme in some of the flights that are going to come after ours as well."

This fifth and final shuttle mission for 2009 is scheduled to include three space walks to store hardware on the exterior of the space station and bring US astronaut Nicole Stott, who has been on the ISS since August, back to earth.

Worms in space

But the crew will also get to conduct some science, with the help of some ground-breaking worms.

Thousands of the microscopic creatures have been sent from Britain's University of Nottingham to study the effect of zero gravity on the human body's muscle development and physiology.

The worms will be stashed inside the Japanese Kibo laboratory on the ISS where they will be tested with several potential treatments for muscle loss.

Researcher Nathaniel Szewczyk said he hopes the worms, which suffer similar weight loss as humans, will pave the way for treatments to be safely tested on astronauts.