Post Thu Jul 21, 2011 9:11 am

ESA's members reafirm their interest for ISS

The ESA Council which took place on 16th and 17th March at Paris reunited representatives of all the member countries of the ESA. The conclusion taken by the Council concerning the ISS was that the station must operate until at least the end of year 2020. Besides the political decision, there was an agreement for an intermediary budget of 550 million euros which should cover the European costs in the ISS project until 2012, when it will take place the next ESA Council of the competent ministries. This way, the ESA will be capable of paying its duties (contribution of almost 8% from the station’s costs) and make sure that the European industry continues its spatial projects.

On short terms, considering the last evolutions from the USA, (the space shuttle retirement) the ESA’s capacity of maintaining the ISS will be questionable. The three ATV flights which were contracted at this moment are insufficient for maintenance until 2020 and possibly they will have to be supplemented. Also, because of their mission goal change, (they will have to transport back to Earth the results of experiments and even the astronauts) it’s expected that the ATV will suffer major design changes. We will see how these problems will be solved – it is certain that, anticipating the course of the events, ESA also allocated 220 million euros in the sector of European launchers until 2012, funds out of which the biggest part will be used for the Ariane 5 rocket.

A short summary of the ISS realized by

The International Space Station or ISS was officially started on 20th November 1998 when Zarya, the first ISS module, was installed. The mission was projected to operate until 2016 and it was recently discussed the utility of keeping it on long terms and the economical and technical implications of an extension (especially considering the decreasing of the international space agencies’ budgets). Given the project’s scale and the effort which was made for building it, but also its significance for the large public, a political decision of disassembly is not expected soon.


The first module – Zarya – was launched using a Proton-K rocket. At this moment, the ISS is visited by:
-the American Space Shuttle
-the Soyuz capsule
-the Progress capsule

-the ATV (the European Space Agency)
-the HTV (the Japan Aerospace Exploration Agency)

The orbit

The International Space Station’s orbit is maintained at an altitude between 278 and 460 km above the Earth, with a nominal altitude of 350 km and realizing 15.7 orbits in a day, with an orbital speed of almost 7.7 km/s. Still, there are some limitations, such as the Soyuz docking missions, when a maximal altitude of 425 km is required. The ISS orbit slope is 51.6 degrees in relation to the Equator.
Station operations

The station’s thermal control system main purpose is to maintain the temperature balance in the station. Without it, the temperature inside can vary from 120° Celsius, on the side exposed to the Sun, to -157° Celsius on the side in the shades. The system uses 2 types of concepts: active and passive control. The passive control uses successive isolative layers to reflect the exterior radiation of the Sun, and to prevent the thermal leaks in the colder space; moreover the thermal bridges that may appear between the layers are broken by using special materials, such as Mylar and Kevlar.
The active control ( consisting of three functions : heat collect, transport and dissipation) is organized like this:
- the inner active thermal control system (IATCS)
- the external active thermal control system (EATCS)
- the photovoltaic thermal control system (PVTCS)
- the external active thermal control system in the initial phase of the mission (EEATCS)

ISS also uses solar panels in order to produce the electric energy which is needed onboard. These panels are mobile, which means that they have a mechanism that allows them to rotate after the Sun, being able to align the photovoltaic cells towards the Sunbeams, in order to gather the maximum power. This type of mechanism allows the generation of up to 84kW. Moreover during the eclipses, the panels can be re-orientated to reduce the drag – this aspect is important if we consider the large surface of these panels and thereby a large atmospheric drag.

In addition, batteries using the nickel-hydrogen technology are used to deposit the required energy for eclipses, granting full functionality for around 35 minutes. Because of their constant degradation and the strict requirement for their performance maintenance, these batteries are periodical replaced.

The voltage on the station varies between 28V DC and 180V DC. The obtained power is stabilized and distributed on 160V DC, and converted after in 124V DC (this high voltage results in a minimum weight of the power lines).

The station is equipped with a 3-axially stabilized positioning control system. Currently, the orientation is maintained using a system of gyroscopes for the moment control, but when they become saturated, a system of engines intervene automatically.
Also, when a visiting space shuttle is docked, its engines can be used to correct the orbit or the position of the station. It must be mentioned that such orbit corrections must be performed periodically, considering the aerodynamic resistance of the atmosphere and the due to this the fact that ISS is lowering the altitude at a rate of approximately 2.5 km/month.

Onboard are used horizon sensors which allow the use of the Earth’s infrared emission and the upper part of the atmosphere or the alignment of the inertial system, the solar sensors which determine the position of the Sun using the sensor’s inner coordinates (they will be further converted into the stations own coordinates), stellar cameras which are used to determine the inertial position of the station through the identification of the stars in the field of view of the instrument, magnetometers which are used to measure the magnetic field of the Earth and finally Glonass/GPS receivers.
The software of the positioning system has a couple of operating modes to maximize the power and minimize the negative thermal effects:
- x-axis maintained parallel with the orbital speed vector
- or x-axis parallel with the vector of the angular momentum H
- or y-axis maintained parallel with the orbital speed vector

The Space station has a special system, “Environment Control and Life Maintenance System”, which controls the fundamental factors affecting life aboard (hence, oxygen and other gases’ concentrations, atmospheric pressure necessary for breathing, water, fire prevention system etc. ). This system is composed of five main components:

• Atmospheric control and maintenance: supplies the ISS with oxygen and nitrogen (gases which are used in experiments and for other purposes) and maintains the atmospheric pressure
Also maintains the gas concentrations at sea level concentrations (21% oxygen, 78% nitrogen). The Russian segment of the ISS was responsible for these functions in the first phases of station construction. Oxygen will be provided by an Elektron electrolysis system which separates water molecules in oxygen and hydrogen. The USA will provide additional oxygen, nitrogen and pressure maintenance systems through rechargeable tanks, available at the end of the first assembly stage, using pipes from the American segment.
• Atmospheric refreshment system: eliminates carbon dioxide and other contaminating particles and monitors oxygen and nitrogen levels. Special absorbing materials are used for collecting carbon dioxide which is then eliminated into space.
• Temperature and humidity control: recycles air, absorbs moisture and maintains a constant temperature aboard. The central part in this subsystem is taken by a common recirculation room in which air is drawn through special filters, cooling it and reducing its humidity, sending it back into the station. The water obtained is sent to the water management and recovery subsystem.
• Water management and recovery subsystem: recovers and recycles water from showers, toilets, condensation, fuel cells etc. A water processing system purifies residual water transforming it into drinkable water. Water quality is continuously checked by a quality control and maintenance process.
• Fire detection and extinction system: consists of smoke detectors, alarms and automated shutting systems, portable fire extinguishers, oxygen containers and gas masks. In each pressurized compartment there are two fire extinguishers besides the equipment ventilation system (which ensures proper ventilation for electronic components).
• The telecommunications system must ensure bidirectional audio and video links, both between crew members and between the crew and scientists located on Earth, all of these in the Ku, S and UHF frequency channels. It also allows the crew to send commands directly to the ISS operators, to direct them towards a space shuttle or the other way around besides providing the command center and the instrument operation center with data obtained from systems, experiments and on-board tools.

Mass : 455.000 kg (in the final stage, after complete construction)
Dimensions : 58.5 x 30.5 m (solar panels completely deployed cover 108.5 x 72.8 m)
Costs : 100 billion euros – for the whole 30 year period, considering designing, mounting and exploitation costs for at least 10 years (costs which will be divided between participating countries)

-Destiny Laboratory Module
-Columbus Module
-Kibo Japanese Experimental Module
-Express Logistics Carrier
-Multipurpose Laboratory Module

Control Centers:
-NASA Lyndon B. Johnson Space Center, Houston, USA
-Kenedy Space Centre, USA
-RKA mission control center, Korolyov Russia
-Mobile Servicing System Control and Training, Saint-Hubert, Quebec, Canada
-Columbus Control Centre, Oberpfaffenhofen, Germany
-ATV Control Centre, Toulouse, France
-HTV Control Centre, Tsukuba, Japan

Scientific Aims

One of the main aims of the ISS is to provide a suitable environment for carrying out specific experiments that require one or more non-reproducible conditions on Earth. The main research directions are:

• Biology (including biomedical research and biotechnology)

• Physics (including fluid physics, materials' science and quantum physics)

ISS experiments are studying the outer space environment and how a long term exposure to space vacuum and particles would affect the materials. This research will provide to the future designers of space structures and to the researchers in general, new knowledge about the nature of space and thus will enhance the quality of future platforms designed.
Some experiments will study the basic forces of nature (included in the general chapter of fundamental physics), thus making use of weightlessness in order to analyze small forces that are difficult to analyze in the presence of terrestrial gravity, which would explain the evolution of the Universe. Certain investigations using laser in order to cool atoms to temperatures near 0 Kelvin will help us understand Earth's gravity itself.

• Astronomy (including cosmology)

• Meteorology

There will be included large-scale observations about the Earth, long-term changes in climate, studies on the forests, oceans and mountains, the impact of meteorites, hurricanes and typhoons and volcanic effects. Also, the effects of air pollution and smoke from the big cities will be studied. The forest destruction and water pollution are best visible from space and high-resolution images will be captured, which would be impossible to obtain from Earth.

• Long-term effects of microgravity on humans

These experiments will provide useful information for future space travel. Analysis of the effects of gravity can lead to a better understanding of the human body and of the interaction with the environment on Earth. Some researchers believe that even the ISS itself can be used for transport between Earth and Mars.

• Encouraging the commercial applications development in space

• Setting new milestones in the history of space by a record number of trips in space and developing new generations of spatial robots.


ISS is the largest and most complex scientific project in human history, playing a major role in establishing a strong cooperation within the international scientific community. Another side benefit derived from this collaboration was the division of the enormous cost of this project among various participating states, otherwise being difficult to be assumed by a single country.