The seven-member crew of the space shuttle Endeavour practised an emergency escape from the launch pad on Wednesday as part of a dress rehearsal in preparation for next month's shuttle launch to the International Space Station.

The procedure is one of several safety measures the crew has practised since arriving at Kennedy Space Center in Cape Canaveral, Fla., on Monday. The dress rehearsals will culminate Thursday with a simulated countdown launch for the crew and launch team.

Canadian astronaut Dave Williams, a 53-year-old Saskatoon-born mission specialist, said the preparation is key to managing risks with space missions.

"One of the things that's important to point out is — we don't take chances, we manage risks," said Williams, one of the seven astronauts who will board Endeavour for the space shuttle's Aug. 7 launch.

"And every time we fly in space we evaluate the risks and what has happened, and we try to make the next flight safer."

Williams has been in space once before, spending 16 days on the shuttle Columbia in 1998.

He's expected to break a Canadian record by spending 19 hours floating outside the space station as he does assembly and repair work. The work will be spread out over three separate spacewalks.

During the 14-day assembly mission, the astronauts are to deliver and install an extension for the central struts that support the station's solar power arrays.

On one spacewalk, the astronauts will replace a failed gyroscope, one of four electrically powered turbines that steer and steady the station.

The crew also includes educator-turned-astronaut Barbara Morgan, an Idaho teacher who was chosen as a backup candidate for the 1985 NASA teacher-in-space program.

The woman chosen, New Hampshire teacher Christa McAuliffe, died with six others when the space shuttle Challenger exploded shortly after takeoff in 1986.

Next month's mission will be the first flight in almost five years for Endeavour, which underwent extensive refurbishment.