Zvezda (ISS)

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Zvezda service module with a Progress docked on the right and the Zarya FGB on the left. (NASA)

Zvezda Service Module under construction

Zvezda (Russian: Звезда, meaning "star"), also known as the Service Module is the third module launched to the International Space Station and provides the main life support systems and living quarters for the crew. 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 funded and owned by the United States). It was launched on a Proton rocket on July 12, 2000 and docked with the Zarya module on July 26.

Zvezda is similar in layout to the core module of the Mir space station. The basic structural frame was initially built in the mid-1980s and designed to be the core of the Mir-2 space station, which the ISS replaced, and, in fact, was labeled as "Mir-2" for quite some time in the factory. The design lineage of Zvezda extends back to the original Salyut stations.

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. However, without the Service Module, it would be several more flights before the ISS would be able to support a permanent crew.

Zvezda provided early living quarters, a life support system, a communication system, electrical power distribution, a data processing system, a flight control system, and a propulsion system. These quarters and systems are to be supplemented or replaced by future ISS components.

Zvezda consists of a cylindrical "Work Compartment" where the crews work and live, a cylindrical "Transfer Chamber" which has one docking port, an unpressurised "Assembly Compartment" surrounding the Transfer Chamber, and a spherical "Transfer Compartment" with three docking ports.

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.

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 system to remove carbon dioxide from the air. Zvezda has been criticized for being excessively noisy and the crew have been observed wearing earplugs inside of it.

[edit] Trivia

The Proton rocket used to launch Zvezda was one of the first space rockets to carry advertising; it was emblazoned with the logo of the fast food chain Pizza Hut, for which the company paid US$1 million.