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The ISS: its parts and modules
The ISS is a space complex based in a modular design, which means it was built in different sections called modules. This design makes possible the addition of new modules at any moment, multiplying the possibilities and the station's infrastructure. In this section, we will try and explain the modules and ISS's parts in an easy and short way to you.
Generally speaking, we can distinguish two types of zones:
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Pressurised zones: There is oxygen on them and there is no need of wearing an spacesuit. They all make a total of 900 liveable cubic metres. In them, most experiments and scientific activities take place.
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Not pressurised zones: They are exposed to the vacuum of space and it is necessary to wear a spacesuit equipped with different systems and tools that provide a vital support. Here, there is among others the solar panels, the integrated truss structure (ITS, you will see it later),...
The ISSin 2018 from a Soyuz Spacecraft // Source: Instagram @iss
Credits: NASA/Roscosmos
Pressurised zones
Like it was said before, in these zones there is oxygen and a spacesuit isn’t needed. Temperature is regulated, letting the crew being in short clothes if they want to, as we can see in some pictures. Pressurized zones consist of many modules:
Zarya Module
Zarya its the first ISS module. It gave the ISS electric energy as well as propulsion and guiadance. Nowadays, it's inside and outside are used as a storage module. It has two solar panels, as well as 6 batteries, 16 fuel tanks and engines that have been used to modify the ISS' orbit.
Picture: STS-88
Unity Module
Unity Module or Node 1 is the first module built in the United States. It is the bond between the north American and the Russian section. It has 6 docking ports, allowing it to dock and berth with other modules. It is also the first one out of the three nodes that are going to be part of the station once it is finished.
Picture: STS-88
Zvezda Module
The Zvezda Module it’s the third module to be launched, and contains all the ISS vital support systems. Two crew members can live on it. It’s the center of the Russian section and it’s where the crew gathers to find a solution in case of an emergency. After being docked to Zayra, the ISS already had three modules: Unity, Zarya and Zvezda:
Picture: STS-106
Destiny Module
The Destiny Module or US laboratory it is the place where science investigation from the United States is done on the ISS. It’s berthed to the Unity module and since then it is the first NASA permanent investigation laboratory in orbit. Here materials, biotechnology, engineering, medicine and physics are studied under microgravity conditions. It has a freezer at -80°C which allows storaging sustances and reactives to the station, and moving them out or inside the station maintaining their temperatures. In Destiny, the AgCam is installed too (Agricultural Cam), which takes photos of vegetative zones for its later investigation of possible aplicattions that could improve agriculture.
Picture: STS-98
Quest Airlock
The Quest Joint Airlock it is the module that allows doing EVAs (Extravehicular Activities), which means it allows the crew to go out from the presurized environment to do repairs, add new parts or investigate in the space vacuum. It’s designed in the way that both EMU (Extravehicular Mobility Unit, the US spacesuit), and Orlan Russian spacesuits can be used on it. Before this module was docked, the Russian EVAs had to be done from the Zvezda Module, and the US ones, from a docked Shuttle.
Picture: STS-127
Pirs and Poisk Modules
They are two Russian airlocks which have two identical hatches. Pirs was used to storage, inspect and refurbish Russian Orlan suits and it had one entrance so the crew that used American suits, which were a little bigger, could go inside the ISS by an alternative entrance or if Quest was not available for any reason. Each one of the modules has a docking port for Soyuz and Progress spacecraft. Poisk is almost identical to Pirs.
Picture: STS-110
Picture: STS-129
Harmony Module
Harmony or Node 2 it is an important node in the ISS because it connects the laboratory modules of the US, Europe and Japan. It gives them electricity and internet connection. Up to 4 crew members can live in it.
Picture: STS-134
Tranquility Module
Tranquility or Node 3 has environmental control and vital support systems, an space toilet, specific training equipment and a dome which allows the crew to view and observe the Earth trough a 360º degree window view.
Picture: Soyuz TMA-20
Colombus Module
Columbus is the European laboratory, which represents the biggest contribution by ESA (European Space Agency) to the ISS. It has with many useful systems like one that allows the crew to exercise and a solar observatory.
Picture: STS-127
Kibo Module
Kibo is the experimental Japanese Module. It’s the biggest module of ISS and it’s berthed to Harmony. It was launched in three different STS missions. It has a presurized zone and a not pressurized one to make experiments exposed to the space vacuum.
Picture: STS-134
Cupola Module
Cupola is the observatory which has the greatest number of windows on the ISS, 7, to be exact. On it, observations of Earth are made. Docked spacecraft are also observed from here. Its center window, which is a circle, has an 80 cm diameter.
Picture: Cupola from inside // NASA
Picture: Astronaut Nicholas Patrick outside the Cupola // STS-130
Rassvet Module
It is a Russian module mostly used as storage and docking port to Russian spacecraft.
Picture: STS-132
Leonardo Module
Leonardo is a multipurpose module used to storage spares, trash and supplies, which were everywhere on the station before this module was docked permanently. Before it was docked, it was used to transport cargo from and to the station, as it was put into the Shuttle’s payload bay. When the Shuttle arrived to the station, Leonardo was docked so the crew could take its content to the station. Once it was empty, trash and cargo which was wanted to return safely to Earth was taken into Leonardo, and then it was undocked and put into the Shuttle’s payload bay again.
Picture: Leonardo docked to the ISS
Picture: Leonardo in Discovery's payload bay
Bigelow Expandable Activity Module
This one is the most recent ones to be installed. It is a module which it is capable of getting expanded after being docked. It was docked in 2016 and in 2018 its mission time got extended.
Not pressurised zones
Not presurized zones, like we said at the beginning of this page, are those zones exposed to the space vacuum where there is no oxygen, which makes necessary to wear a spacesuit which provides you, among other things, with oxygen, communication and refrigeration systems. Here, the solar panels are located as well as many battery storage systems and more. Now we will show you some of the most relevant parts of the non-pressurized areas.
Integrated Truss Structure
It is the transversal structure of the ISS, which we can see in the following picture:
Picture: STS-120
On it, the most important instrument are the photovoltaic solar panels, which transform solar energy to electricity. We can also apreciate the white radiators, which function is based in eliminate the leftover heat of the ISS. Now we will explain how it works shortly so it is easier for you to understand:
Solar panels
In the integrated truss structure, the ISS has 4 groups of photovoltaic solar panels and each one has two pairs of panels. Two can be found at the left and another two can be found at the right. They transform the solar energy in electricity, providing the ISS with the electricity it needs. Each solar panel is 34 metres long and 11 metres wide. These panels are automatically orientated towards the Sun. Together, they generate from 84 to 120KW (84000 to 12000W), enough to give electricity to at least 40 homes. To make an idea of the generated electricity by this panels, a computer and a monitor can consume 270W, and a small refrigerator, 725W. The 60 % of the energy generated goes to the station’s batteries (made from Ni-Cd, Nickel-Cadmiun and Li-ion, Litium-ion), to provide the station with electricity when the solar panels don’t receive sunlight. The electricity is produced in DC, which is regulated at a voltage 160V in the primary circuit and at 124.5V in the secondary circuit. In the following image, we can clearly see the solar panels:
The ISS in 2018 from a Soyuz Spacecraft // Source: Instagram @iss Credits: NASA/Roscosmos
Radiators
The ISS has many radiators built by using aluminium panels (you can see them white at the picture). It's mainly fuction is to disipate the leftover heat from the ISS. As the ISS is in space and does not have an atmosphere protecting it, the ISS area receiving sunlight would be at 121ºC and the one not receiving sunlight would be at -157°C if the ISS didn’t have with a sophisticated thermal control system where the radiators are of great importance. This thermal control system is formed by two closed circuits:
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The first circuit: Trough the radiators runs ammonium, which has a really low solidification temperature (approximately -77ºC at 1 atm), what means that if it were water it would freeze inmediately. All the radiators make a closed circuit.
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Water is running on the second circuit, which consists of cooling plates and heat exchangers that take the overheat inside the station.
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Both of them are connected thanks to a heat exchanger that transfers the heat from water to the ammonium.
Canadarm2 robotic arm
Canadarm2 is a robotic arm that is part of the Mobile Servicing System. It is of great importance in tasks such as assembly or maintenance of the station. It can move equipment and supplies, as well as assisting in extravehicular activities, and check instruments, as well as other cargo. It is hooked to a base that allows it to move on rails that run through the ITS.
Picture: Astronaut Stephen Kern Robinson being moved with Canadarm2 // STS-114
Here ends out short summary of the ISS modules and most relevant parts. We hope you could have understood this space complex parts and its different functions. Remember that you can learn a lot more browsing through our web!
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