1.   But the date has been postponed twice because of delays by Khrunichev in building the critical third station element known as the service module.

2.   Early life support will be provided by the Russian service module, which is scheduled to be launched as the third station element.

3.   Engineers say it is by far the most complex and technically challenging of the U.S.-made station elements.

4.   The aluminum habitation module is now in Huntsville, Ala., where it and the other key U.S. station elements were built by Boeing.

5.   The node will be the connecting passageway to other station elements.

6.   The shuttle will fire its thrusters to force the two station elements together and they automatically will be secured by latches.