.jpg) | |
| 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) |
| Pressurisedvolume |
|
| References:[1][2][3][4][5][6] | |
| Configuration | |
 On-orbit configuration of theZvezda service module | |
Zvezda, also known as theZvezda Service Module, is a module of theInternational Space Station (ISS). It was the third module launched to the station, and provided all of the station'slife support systems, some of which are supplemented in theUS Orbital Segment (USOS), as well as living quarters for two crew members. It is the structural and functional center of theRussian Orbital Segment (ROS), which is theRussian part of the ISS. Crew assemble here to deal with emergencies on the station.[7][8][9]
The module was manufactured in theUSSR byEnergia, with major sub-contracting work by GKNPTs Khrunichev.[10]Zvezda was launched on aProton launch vehicle on 12 July 2000, and docked with theZarya module on 26 July 2000 at 01:45UTC. It is a descendant of theSalyut programme's.
The hull ofZvezda, known as "DOS-8", was initially built in the mid-1980s as a structural spare of theMir core module (DOS-7) and later reconfigured as the core module of theMir-2 station. Its design is a continuation of the civilianSalyut programme's DOS (Durable Orbital Station) lineage.
DOS-7 and DOS-8 were developed after the Soviet government approved the plan to create a next-generation space station with multiple docking ports in 1976. Following the tradition in the Salyut programme, two identical modules were build to ensure a spare in case the primary article was lost during launch or due to a failure in orbit. After the design documentation was completed in 1982, manufacturing began on the twin modules at KB Salyut's Khrunichev factory.
The DOS-8 pressure vessel was completed in February 1985 after which work slowed significantly until the launch of DOS-7 as the Mir core module in February 1986. Major internal equipment was installed by October 1986.
Following the successful launch of DOS-7, DOS-8 became the core element of a proposed successor to Mir, internally known as GK-180, which utilised 100-tonne modules launched on the Energia and a large truss structure. The design was announced to the media as Mir-2 in January 1988 and officially approved in December 1989, though by 1991 significant delays and funding cuts caused the project to be abandoned.
After considering the option to replace the Mir core module in orbit with the DOS-8 article and deliver new add-on modules aboard Buran, by 1992 the choice fell on launching DOS-8 as the core of a new, streamlined Mir-2 station. The new configuration featured a truss braced against the core module's working compartment and a number of small expansion modules. Photovoltaic panels and solar concentrators would be attached to the truss, together with radiators, orientation thrusters, gyrodines and science experiments.
In 1993, the Mir-2 complex was redesigned once more, with the truss structure transitioning from a Sofora-like design assembled by the cosmonauts in orbit to one using preintegrated truss segments, and two Universal Docking Modules added to the station. Soon after, the Mir-2 station was merged with Space Station Freedom to form the International Space Station, on which DOS-8 serves as the Service Module.[11]
Zvezda consists of three pressurised compartments and one unpressurised compartment. From forward to aft, the pressurised compartments are: a spherical transfer compartment, a long cylindrical main working compartment, and a short cylindrical transfer tunnel. The unpressurised assembly compartment wraps around the exterior of the transfer tunnel.[10][12]Zvezda weighs about 19,050 kg (42,000 lb)[13] and has a length of 13.1 m (43 ft). The solar panels extend 29.7 m (97 ft).
The transfer compartment (Russian:Переходный Отсек, ПхО,romanized: Perekhodniy Otsek, PKhO) has three docking ports, along with an internal hatch that can seal it off from the rest of the module, allowing it to serve as an airlock. WhenZvezda was launched, its forward port docked to the aft port of theZarya module already in orbit. The nadir (Earth-facing) port was initially intended to be used by theUniversal Docking Module, it would instead be used by thePirs module from 2001 to 2021 and theNauka module since 2021. The zenith (space-facing) port was initially intended to be used by theScience Power Platform, it would instead be used by thePoisk module since 2009. The transfer compartment's airlock functionality was only used once duringExpedition 2, whenYury Usachov andJames Voss put a docking cone on the nadir port to prepare for the arrival of thePirs module.
The working compartment (Russian:Рабочий Отсек, РО,romanized: Rabochii Otsek, RO) is where the crews work and live and makes up the bulk of the module's volume. It comprises two cylinders joined together by a conical adapter. The forward, small-diameter instrument compartment (Russian:Приборой Отсек, ПО,romanized: Priboroi Otsek, PO) contains the station command post (central computer) and related equipment, The aft large-diameter habitable compartment (Russian:Жилой Отсек, ЖО,romanized: Zhloi Otsek, ZhO) contains two sleeping quarters, aNASA-providedTreadmill with Vibration Isolation Stabilization, a kitchen equipped with a refrigerator/freezer and a table, a bicycle for exercise, a toilet and other hygiene facilities, this section also contained theElektron system that electrolyzes condensed humidity and waste water to provide up to 5.13 kilograms (11.3 lb) per day ofoxygen for breathing, while hydrogen is expelled into space. The system also creates condensedwater that could be used for drinking in an emergency, but ordinarily fresh water from Earth was used.
Zvezda has 13 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. Designers did not include installation of Window No. 11.
Zvezda is also the home of the Lada Greenhouse, which is a test for growing plants in space.[15]
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.[16] The "Transfer Chamber" is equipped with automatic docking equipment and is used to serviceSoyuz andProgress spacecraft.
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 isdinitrogen tetroxide and the fuel isUDMH, the supply tanks being pressurised with nitrogen.[17] The two main engines onZvezda 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 sinceZvezda arrived in 2000.[18]
Elektron proved to be rather noisy for the crew and significant maintenance work, having failed several times and requiring the crew to use theSolid Fuel Oxygen Generator canisters (also called "oxygen candles", which were the cause of a fire onMir) when it has been broken for extended amounts of time. It also contains the Vozdukh, a system which removescarbon dioxide from the air based on the use of regenerable absorbers of carbon dioxide gas.
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 theCommon 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-installedElektron 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.[19][20][21][22][23]
The rocket used for launch to the ISS carriedadvertising; it was emblazoned with thelogo ofPizza Hut restaurants,[24][25][26] for which they are reported to have paid more than US$1 million.[27] The money helped supportKhrunichev State Research and Production Space Center and the Russian advertising agencies that orchestrated the event.[28]
Management and integration of the Service Module into the International Space Station began in 1991. Structural construction was performed byRKK Energia, then handed over to the Khrunichev Design Bureau for final outfitting. Joint reviews between theRussian 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 ofZarya. (The U.S.Unity module had already been attached toZarya). Later in July, the computers aboardZarya handed over ISS commanding functions to computers onZvezda.[29]
On 11 September 2000, two members of theSTS-106Space Shuttle crew completed final connections betweenZvezda andZarya; during a 6-hour, 14 minuteEVA, astronautEd Lu and cosmonautYuri Malenchenko connected nine cables betweenZvezda andZarya, including four power cables, four video and data cables and a fiber-optic telemetry cable.[30] The next day, STS-106 crew members floated intoZvezda for the first time, at 05:20 UTC on 12 September 2000.[31]
Zvezda provided early living quarters, a life support system, a communication system (Zvezda introduced a 10 Mbit/s Ethernet network to the ISS[32]), 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 anInterim Control Module (ICM) in case it was delayed significantly or destroyed on launch.[citation needed]
Since September 2019, theZvezda module has been experiencing a worsening air leak. The source appears to be microscopic structural cracks within the small transfer tunnel, known by the Russian acronym PrK, which connectsZvezda to the aft docking port typically used by Progress cargo spacecraft. Initially, the leak rate was minimal, less than 1 pound (0.45 kg) per day, but it has steadily increased, reaching 3.7 pounds (1.7 kg) per day as of April 2024. While both NASA and Roscosmos suspect issues with welds, the exact cause of the leak remains unknown. NASA has classified the leaks as a high-risk threat to spaceflight activities, potentially leading to "catastrophic failure." However, Roscosmos says that it does not believe a catastrophic disintegration of the PrK is realistic, and has expressed confidence in their ability to monitor and manage the leak.[33][34][35]
As of November 2024[update], to mitigate the leak and the risk of a catastrophic failure the normal operating procedure is to keep the hatch leading to the PrK from Zvezda closed except when a spacecraft is being actively accessed. When the hatch leading to the PrK is opened, a hatch leading to theUS Orbital Segment of the ISS is closed, which would contain a catastrophic failure and decompression to just theRussian Orbital Segment.[35]
Aft port
Nadir
Zenith
Forward
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