Zvezda (ISS module)
Russian International Space Station module From Wikipedia, the free encyclopedia
Russian International Space Station module From Wikipedia, the free encyclopedia
Zvezda (‹See Tfd›Russian: Звезда, lit. 'star'), also known as the Zvezda Service Module, is a module of the International Space Station (ISS). It was the third module launched to the station, and provided all of the station's life support systems, some of which are supplemented in the US Orbital Segment (USOS), as well as living quarters for two crew members. It is the structural and functional center of the Russian Orbital Segment (ROS), which is the Russian part of the ISS. Crew assemble here to deal with emergencies on the station.[7][8][9]
Module statistics | |
---|---|
COSPAR ID | 2000-037A |
Part of | International Space Station |
Launch date | 12 July 2000, 04:56 UTC |
Launch vehicle | Proton-K |
Docked | 26 July 2000, 01:45 UTC (Zarya aft) |
Mass | 20,320 kg (44,800 lb) |
Length | 13.1 m (43 ft) |
Width | 29.7 m (97 ft) |
Diameter | 4.35 m (14.3 ft) |
Pressurised volume |
|
References: [1][2][3][4][5][6] | |
Configuration | |
On-orbit configuration of the Zvezda service module |
The module was manufactured in the USSR by Energia, with major sub-contracting work by GKNPTs Khrunichev.[10] Zvezda was launched on a Proton launch vehicle on 12 July 2000, and docked with the Zarya module on 26 July 2000 at 01:45 UTC. It is a descendant of the Salyut programme's DOS spacecraft, leading to the alternate name, DOS-8.
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.
The Mir-2 space station was redesigned after the failure of the Polyus orbital weapons platform core module to reach orbit. Zvezda is around 1⁄4 the size of Polyus, and has no armaments.
Zvezda consists of the cylindrical "Work Compartment" where the crews work and live (and which makes up the bulk of the module's volume), the small spherical "Transfer Compartment" located at the front (with three docking ports), and at the aft end the cylindrical "Transfer Chamber" (with one docking port) which is surrounded by the unpressurized "Assembly Compartment" – this gives Zvezda four docking ports in total.[10] The component weighs about 18,051 kg (39,796 lb) and has a length of 13.1 m (43 ft). The solar panels extend 29.7 m (97 ft).
The "Transfer Compartment" attaches to the Zarya module, and has docking ports intended for the Science Power Platform (SPP) and the Universal Docking Module (UDM). As in the early days of Mir, the transfer compartment provides a suitable EVA airlock where spacewalkers in Orlan space suits removed a hatch after closing a few that connected the compartment to the rest of the station. It was used only during Expedition 2, where Yury Usachov and James Voss put a docking cone on the nadir port. The lower port connects to Pirs and the top port connects to Poisk. Eventually, the plan for Pirs was for it to be deorbited on 23 July 2021 and replaced by Nauka (Multipurpose Laboratory Module) docking on 29 July 2021.
The "Assembly Compartment" holds external equipment such as thrusters, thermometers, antennas, and propellant tanks. The large movable "Lira satellite communications antenna" is located on the Zvezda service module near the aft or rear of the International Space Station on this Assembly Compartment.[12] The "Transfer Chamber" is equipped with automatic docking equipment and is used to service Soyuz and Progress spacecraft.
Zvezda can support up to six crew [10] including separate sleeping quarters for two cosmonauts at a time.[10] It also has a NASA-provided Treadmill with Vibration Isolation System, a kitchen equipped with a refrigerator/freezer and a table, a bicycle for exercise, a toilet and other hygiene facilities. The crew's wastewater and condensation water pulled out of the cabin air is recycled. Zvezda has been criticised for being excessively noisy and the crew has been observed wearing earplugs inside it.
Zvezda has 14 windows.[10] There are two 22.5 cm (8.9 in) diameter windows, one in each of the two crew sleep compartments (windows No. 1 and 2), six 22.5 cm (8.9 in) diameter windows (No. 3, 4, 5, 6, 7 and 8) on the forward Transfer Compartment earth-facing floor, a 40 cm (16 in) diameter window in the main Working Compartment (No. 9), and one 7.5 cm (3.0 in) diameter window in the aft transfer compartment (No. 10). There are a further three 22.5 cm (8.9 in) diameter windows in the forward end of the forward transfer compartment (No. 12, 13 and 14), for observing approaching craft. Window No. 11 is unaccounted for in all available sources.
Zvezda 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 (up to 5.13 kg per day is generated) 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. The Elektron system has required significant maintenance work, having failed several times and requiring the crew to use the Solid Fuel Oxygen Generator canisters (also 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 absorbers of carbon dioxide gas. Zvezda is also the home of the Lada Greenhouse, which is a test for growing plants in space.[13]
The Service Module has 16 small thrusters as well as two large 3,070-newton (690 lbf) S5.79 thrusters that are 2-axis mounted and can be gimballed 5°. The thrusters are pressure-fed from four tanks with a total capacity of 860 kg.[6] The oxidizer used for the propulsion system is dinitrogen tetroxide and the fuel is UDMH, the supply tanks being pressurised with nitrogen.[14] 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.[15]
The Zvezda module inherited a limitation from its predecessor Mir and Salyut stations rooted in a Soviet spacecraft design philosophy favoring the permanent installation of critical hardware. This approach, while providing more internal living space by concealing systems behind closed panels, contrasts with the US Orbital Segment's (USOS) strategy of using easily replaceable 41.3-inch-wide (105 cm) International Standard Payload Racks. USOS modules, connected via the Common Berthing Mechanism (CBM), have 51-inch-wide (130 cm) hatches that accommodate the movement of these racks between modules and spacecraft. Consequently, broken or unfixable hardware on Zvezda remains permanently in place. A notable example is the pre-installed Elektron oxygen-generating system, which required frequent repairs by cosmonauts due to the inability to replace it. Zvezda's 78.74-centimetre-wide (31.00 in) hatch and the lack of available replacement Elektron units hindered the replacement process. The discontinuation of Elektron production further exacerbated this issue. In October 2020, the Elektron system malfunctioned again, leading to its deactivation.[16][17][18][19][20]
The rocket used for launch to the ISS carried advertising; it was emblazoned with the logo of Pizza Hut restaurants,[21][22][23] for which they are reported to have paid more than US$1 million.[24] The money helped support Khrunichev State Research and Production Space Center and the Russian advertising agencies that orchestrated the event.[25]
Management and integration of the Service Module into the International Space Station began in 1991. Structural construction was performed by RKK Energia, then handed over to the Khrunichev Design Bureau for final outfitting. Joint reviews between the Russian Space Agency (Roscosmos) and the NASA ISS Program Office monitored construction, solved language and security concerns and ensured flight readiness and crew training. Several years of delay were encountered due to funding constraints between Roscosmos and RKK Energia requiring repeated delays in First Element Launch.
On 26 July 2000, Zvezda became the third component of the ISS when it docked at the aft port of Zarya. (The U.S. Unity module had already been attached to Zarya). Later in July, the computers aboard Zarya handed over ISS commanding functions to computers on Zvezda.[26]
On 11 September 2000, two members of the STS-106 Space Shuttle crew completed final connections between Zvezda and Zarya; during a 6-hour, 14 minute 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.[27] The next day, STS-106 crew members floated into Zvezda for the first time, at 05:20 UTC on 12 September 2000.[28]
Zvezda provided early living quarters, a life support system, a communication system (Zvezda introduced a 10 Mbit/s Ethernet network to the ISS [29]), electrical power distribution, a data processing system, a flight control system, and a propulsion system. These quarters and some, but not all, systems have since been supplemented by additional ISS components.
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 (ICM) in case it was delayed significantly or destroyed on launch.[citation needed]
Since September 2019, the Zvezda module has been experiencing a worsening air leak. The source appears to be microscopic structural cracks within the small tunnel connecting Zvezda to a docking port used by Progress cargo spacecraft. The leak rate has increased from initially less than 1 pound (0.45 kg) per day to 3.7 pounds (1.7 kg) per day as of April 2024. While both NASA and Roscosmos suspect internal or external welds, the root cause of the leaks remains unknown. The agencies have said that if the leaks reach an untenable level, they plan to close the hatch leading to the tunnel, however that would result in the loss of the docking port. Internally, NASA has classified the leaks as a high-risk threat to spaceflight activities, potentially leading to "catastrophic failure." However, Roscosmos has expressed confidence in their ability to monitor the leak and close the hatch before it becomes unmanageable.[30][31]
Aft port
Nadir
Zenith
Forward
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