Third module to be launched, the Service module (Zvezda) will enable the station to be permanently habitated by 3 people, it is the primary Russian contribution. It will just like Zarya (FGB), be launched by a Russian Proton rocket from the Baikonur Cosmodrome, in Kazahkstan. During launch most of it's systems will be in standby mode, but once in orbit preprogrammed commands will be activated and systems will go online, the solar arrays and communications antenna will be deployed. Ground controllers will then use Zarya to do the rendezvous with the Service module. In the picture you first see the Service module, then Zarya and Unity with it's two mating adapters. The Service module will be guided by remote control to dock with the already orbiting station in July 2000. The module is very similar to the Core module of the Mir space station with only some modifications and changes. The module provides living quarters in the early phase, life support system, electrical power distribution, data processing system, flight control system, and propulsion system. The module's aft docking port will serve as the primary docking port for Progress-type cargo resupply vehicles. The Service module will also provide a communications system that enables remote command capabilities from ground flight controllers. So when this module is up and running the first crew can board the station. Many of it's systems will be replaced by later U.S. modules, such as living quarters and life support, but it will always serve as the structural and functional center of the Russian part of the station.

Just as the Mir core module, the Service module has three pressurized compartments, a spherical transfer chamber at the forward end, known as the node on Mir, a long cylindrical work compartment and a small cylindrical transfer chamber at the aft end. A unpressurized compartment is also located around the aft transfer chamber and houses fuel tanks, antennas and thrusters. The Service module will have four docking ports, two less than the Mir station. One in the aft with a probe and cone docking mechanism will be used to allow automated dockings from Progress and Soyuz spacecraft. And three hybrid docking mechanisms in the forward spherical transfer chamber (small Node). One point upwards, one downwards and one forwards. The one forwards will be docked to the FGB, later in the assembly the one facing upwards will be connected to a Russian Science Platform and the one facing downwards will be connected to a Russian Universial Docking Module.

Living accommodations on the module include personal sleeping areas, toilet and hygiene facilities, freezer/refrigerator and a table for securing meals so they don't float away. The module has fourteen windows, 3 which are 22,8 centimeter in diameter are placed in the forward transfer node to allow viewing of dockings maneuvers. One 40,6 centimeter wide window in the working compartement, and small individual windows in each crew compartment, additional windows are placed in position for earth and module observation. The Service module also has U.S. exercise equipment to keep the crew in good physical condition. This includes a NASA-provided treadmill and a bicycle. The crew's wastewater and condensated water will be used for oxygen-generation in the module but will not be reused as drinking water. Spacewalks done with the Russian Orlan-M spacesuit can be done from the forward transfer node until the airlock module is launched later in the assembly. The spacewalks is possible by sealing of all the modules, depressurizing the node and then exit one of the free docking ports. This used to be done on Mir before the Kvant-2 module was connected to the station in 1989. The latest spacewalk executed like this was an internal one, to repair the power supply in the damaged Spektr module. The module had been punctured in a Progress collision in summer 1997.

Module information:

Related Info:
NASA | JSC | Shuttle | Shuttle-Mir | Mir

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