The seven Endeavour astronauts suited up and boarded their spaceship at Kennedy Space Center's launch pad 39B today for a successful practice countdown that culminated with a simulated engine shutdown as clocks reached zero.

At launch pad 39B, the astronauts pause for a photo during Terminal Countdown Demonstration Test activities. From left are STS-108 commander Dom Gorie, pilot Mark Kelly, mission specialists Dan Tani and Linda Godwin, and Expedition Four's flight engineer Dan Bursch, commander Yuri Onufrienko and flight engineer Carl Walz. Photo: NASA

The drill is a routine event for all shuttle crews prior to launch. The astronauts flew from their Johnson Space Center training base in Houston to Florida's spaceport on Tuesday.

Besides the mock countdown, the crew has received briefings on how to use the emergency escape baskets at the pad, which would whisk the astronauts off the tower and down to a fortified bunker if a catastrophic problem arose on launch day. They also test-drove the armored tank to be used to evacuate the pad area.

No crew has ever had to use the baskets or tank for real, but each practice just in case.

Launch of Endeavour on its trek to the international space station remains slated for 7:44 p.m. EST on November 29.

The shuttle will ferry the Expedition Four crew to the orbiting outpost to begin a five-month stay and return the Expedition Three astronauts back to Earth after spending four months on Alpha.

The Expedition Four crew is commanded by Russian cosmonaut Yuri Onufrienko with American flight engineers Carl Walz and Dan Bursch. The three men will replace the Expedition Three crew of commander Frank Culbertson, pilot Vladimir Dezhurov and flight engineer Mikhail Tyurin.

Endeavour's crew is led by commander Dom Gorie, with pilot Mark Kelly and mission specialists Linda Godwin and Dan Tani.

This 107th shuttle mission will be the first since the September 11 terrorist attacks on America, promoting NASA and the Air Force to beef up security measures to protect Endeavour and crew.

"I'm not able to talk about any specifics, but we are very, very pleased with everything that's been done for security here," commander Gorie told reporters during a news conference Thursday. "We're extremely happy with all the hard work that's gone into making this site -- and the launch and landing of Endeavour -- a safe one."

The shuttle is carrying 6,000 Americans flags that will be given to the families of victims from the September 11 attacks after the flight.

In addition, flags recovered from the World Trade Center and Pentagon and one from Pennsylvania will be flown in space, along with the badges of 23 New York City police officers and 343 patches for the firefighters killed at the World Trade Center.

"I think anything that we can take that might commemorate the memory of those people who lost their lives is significant. And I can't think of another place where we could send items of significant emotional value were it means more to people," Gorie said.

"I think it will be a significant sign to them that their loved ones were placed in a very, very significant -- and maybe the highest pinnacle -- of our thoughts and prayers and wishes. I think it would have to be a very powerful message to them and to the country of how significant an event we think that was on September 11."

Besides exchanging the space station's resident crew, Endeavour will deliver to Alpha a couple tons of supplies and equipment using the Italian-made Raffaello cargo module. Mission specialists Godwin and Tani will also take a four-hour spacewalk to install thermal blankets on the drive assembly for one of the station's solar wings and perform other "get-ahead" tasks in preparation for new construction work next spring.

Endeavour's mission is due to last 11 days with landing back at Kennedy Space Center on December 10 at 3:05 p.m. EST.