International Space Station

Zvezda (, also known as the Zvezda Service Module, is a component of the International Space Station (ISS). It was the third module launched to the station, and provides some of the station's life support systems, as well as living quarters for two crew members. It is the structural and functional center of the Russian portion of the station - the Russian Orbital Segment.

The module was manufactured by S.P. Korolev Rocket and Space Corporation Energia and is currently the only fully Russian-built and funded module besides Pirs. (Zarya was built by Russia, but was funded and is owned by the United States). Zvezda was launched on a Proton rocket on July 12, 2000 and docked with the Zarya module on July 26. The rocket used for the launch was one of the first to carry advertising; it was emblazoned with the logo of the fast food chain Pizza Hut, for which the company paid US$1 million.[citation needed]

The basic structural frame of Zvezda, known as "DOS-8", was initially built in the mid-1980s to be the core of the Mir-2 space station. This means that Zvezda is similar in layout to the core module (DOS-7) of the Mir space station. It was in fact labeled as "Mir-2" for quite some time in the factory. Its design lineage thus extends back to the original Salyut stations. The space frame was completed in February 1985 and major internal equipment was installed by October 1986.

Zvezda consists of a cylindrical "Work Compartment" where the crews work and live, a cylindrical "Transfer Chamber" which has one docking port, an unpressurized "Assembly Compartment" surrounding the Transfer Chamber, and a spherical "Transfer Compartment" with three docking ports. The component weights 18,051 kg (42,000 lb) and had a length of 13.1 meters (43 feet). The solar panels extend 29.7 meters (97.5 feet).

The "Transfer Compartment" attaches to the Zarya module, and has docking ports intended for the Science Power Platform and the Universal Docking Module. Currently the lower port contains the Russian Docking Compartment and the other is empty. It could be used as an airlock; however, if the hatch failed, it would be impossible to travel to the rest of the station, so this capability has never been used. Once the Multipurpose Laboratory Module comes, before the launch, two crewmembers of Expedition 18 will remove the Docking Compartment, relocate it on the zenith port of Zvezda, and install and activate the Multipurpose Laboratory and the European Robotic Arm.

The "Assembly Compartment" holds external equipment such as thrusters, antennas, and propellant tanks.

The "Transfer Chamber" is equipped with automatic docking equipment and is used to service Soyuz and Progress spacecraft.

Zvezda contains sleeping quarters for two cosmonauts, a NASA-provided treadmill and a bicycle for exercise, toilet and other hygiene facilities and a galley with a refrigerator and freezer. It contains the primary Russian computers for guidance and navigation. It has a total of 14 windows -- three 9-inch diameter windows in the forward Transfer Compartment, a 16-inch window in the Working Compartment, one in each crew compartment, and several more. It also contains the Elektron system that electrolyzes condensed humidity and waste water to provide hydrogen and oxygen. The hydrogen is expelled into space and the oxygen is used for breathing air. The condensed water and the waste water can be used for drinking in an emergency, but ordinarily fresh water from Earth is used. There are 16 small thrusters and two large thrusters for propulsion, and eight batteries for storing power.

The Elektron system has required significant maintenance work, having failed several times and requiring the crew to use Solid Fuel Oxygen Generator canisters (commonly called "Oxygen Candles", which were the cause of a fire on Mir) when it has been broken for extended amounts of time. It also contains the Vozdukh, a system which removes carbon dioxide from the air based on the use of regenerable adsorbers of carbon dioxide gas. Zvezda has been criticized for being excessively noisy and the crew has been observed wearing earplugs inside it.

On July 26, 2000, Zvezda became the third component of the ISS when it docked at the aft port of Zarya. (Zarya had already been attached to the U.S. Unity module.) Later in July, the computers aboard Zarya handed over ISS commanding functions to computers on Zvezda.

On September 11, 2000, two members of the STS-106 Space Shuttle crew completed final connections between Zvezda and Zarya: during a 6 hour, 14 minute extravehicular activity (EVA), astronaut Ed Lu and cosmonaut Yuri Malenchenko connected nine cables between Zvezda and Zarya, including four power cables, four video and data cables and a fiber-optic telemetry cable. The next day, STS-106 crew members floated into Zvezda for the first time, at 12:20 a.m. CDT on September 12, 2000.

Zvezda provided early living quarters, a life support system, a communication system (Zvezda introduced a 10Mbit/s Ethernet network to the ISS), electrical power distribution, a data processing system, a flight control system, and a propulsion system. These quarters and systems have since been supplemented by additional ISS components.

The two main engines on Zvezda can be used to raise the station's altitude. This was done on 25 April 2007. This was the first time the engines had been fired since Zvezda arrived in 2000.

Due to Russian financial problems, Zvezda was launched with no backup and no insurance. Due to this risk, NASA had constructed an Interim Control Module in case it was delayed significantly or destroyed on launch.