The Joint Airlock Module under final testing at NASA's Marshall Space Flight Center. Photo: NASA

The Joint Airlock Module -- the gateway from which crew members aboard the International Space Station (ISS) will enter and exit the 470-ton orbiting research facility -- arrived at the Kennedy Space Center yesterday.

The airlock was transported from NASA's Marshall Space Flight Center in Huntsville, Ala., today arriving at KSC's Shuttle Landing Facility aboard NASA's Super Guppy aircraft at 1:40 p.m. The airlock was then transported to the Operations and Checkout Building in the KSC industrial area where it will undergo vacuum chamber testing beginning next week. It will then be moved to the Space Station Processing Facility (SSPF) for further prelaunch preparation and checkout.

The massive, spindle-shaped airlock is 20 feet long, has a diameter of 13 feet at its widest point, and weighs six and a half tons. It was manufactured at NASA's Marshall Space Flight Center by the Huntsville division of The Boeing Company.

The airlock includes two compartments: the crew lock, to be used by astronauts as they enter and exit the Space Station; and the equipment lock, where astronauts will change into and out of their spacesuits and stow all necessary gear.

The airlock is a critical element of the ISS because of design differences between American and Russian spacesuits. Currently, American suits will not fit through Russian-designed airlocks. The Joint Airlock Module is specially designed to accommodate both suits, providing a chamber where astronauts from every nation can suit up for spacewalks to conduct maintenance and construction work or to do science experiments outside the Station.

An illustration of the airlock after its installation and the configuration of the space station next May. Photo: NASA

The Space Shuttle Atlantis will carry the airlock to orbit on mission STS-104, the tenth International Space Station flight, currently targeted for liftoff in May 2001. The Shuttle crew will secure the airlock to the right side of "Unity," the American-built connecting node that currently comprises one-third of the current Space Station, along with the Russian modules "Zarya" and "Zvezda."

The International Space Station is a cooperative endeavor by the United States and 15 other nations -- the largest multinational space construction effort in history. Orbital assembly of the Station is expected to be complete in 2006.