INTERNATIONAL SPACE STATION - 3

INTERNATIONAL SPACE STATION-3

MICROGRAVITY:

At the station's orbital altitude, the gravity from the Earth is 88% of that at sea level. The state of weightlessness is caused by the constant free fall of the ISS. Due to the equivalence principle, free fall is indiscernible from a state of zero gravity, however the environment on the station is instead often described as microgravity, as it is imperfect due to four effects:
1. The drag resulting from the residual atmosphere.
2. Vibratory acceleration caused by mechanical systems and the crew on board the ISS.
3. Orbital corrections by the on-board gyroscopes (or thrusters).
4. The spatial separation from the real centre of mass of the ISS—any part of the ISS not at the exact centre of mass will tend to follow its own orbit.

However, as each point is physically part of the station, this is impossible, and so each component is subject to small accelerations from the forces which keep them attached to the station as it orbits.This is also called the tidal force.

LIFE SUPPORT:

The ISS Environmental Control and Life Support System (ECLSS) provides or controls elements such as atmospheric pressure, fire detection and suppression, oxygen levels, and water supply. The highest priority for the ECLSS is the ISS atmosphere, but the system also collects, processes, and stores waste and water produced and used by the crew. This process includes recycling fluid from the sink, shower, toilet, and condensation from the air. The Elektron system aboard Zvezda and a similar oxygen generation system in Destiny generate oxygen aboard the station.If required, the crew has a backup option in the form of bottled oxygen and Solid Fuel Oxygen Generation (SFOG) canisters. Carbon dioxide is removed from the air by the Vozdukh system in Zvezda. Other by-products of human metabolism, such as methane from the intestines and ammonia from sweat, are removed by activated charcoal filters.

The atmosphere on board the ISS is maintained to have a composition similar to that of the Earth's atmosphere. Normal air pressure on the ISS is 101.3 kPa (14.7 psi), the same as at sea level on Earth. Whilst this type of atmosphere offers various benefits for crew comfort, an Earthlike atmosphere is also much safer than the alternative, a pure oxygen atmosphere, due to the increased risk of fire, responsible for the deaths of the Apollo 1 crew.

SIGHTINGS:

Because of the size of the International Space Station (about that of an American football field) and the large reflective area offered by its solar panels, ground based observation of the station is possible with the naked eye if the observer is in the right location at the right time—in many cases, the station is one of the brightest naked-eye objects in the sky, although it is visible only for brief periods of time, ranging from two to five minutes.

In order to view the station, the following conditions need to be fulfilled, assuming the weather is clear: The station must be above the observer's horizon, and it must pass within about 2000 km of the observing site (the closer the better); it must be dark enough at the observer's location for stars to be visible; and the station must be in sunlight rather than in the Earth's shadow. It is common for the third condition to begin or end during what would otherwise be a good viewing opportunity. In the evening, this will cause the station to suddenly fade and disappear as it moves further from the dusk, going from west to east. In the reverse situation, it may suddenly appear in the sky as it approaches the dawn

POLITICS AND FINANCING:

As a multinational project, the legal and financial aspects of the ISS are complex. Issues of concern include the ownership of modules, station utilisation by participating nations, and responsibilities for station resupply. The main legal document establishing obligations and rights between the ISS partners is the Space Station Intergovernmental Agreement (IGA). This international treaty was signed on January 28, 1998 by the primary nations involved in the Space Station project: the United States, Russia, Japan, Canada and ten Member States of the European Space Agency (Belgium, Denmark, France, Germany, Italy, The Netherlands, Norway, Spain, Sweden, Switzerland). This set the stage for a second layer of agreements, called Memoranda of Understanding (MOU), between NASA and ESA, CSA, RKA and JAXA. These agreements are then further split, such as for the contractual obligations between nations, and trading of partners rights and obligations.Use of the Russian Orbital Segment is also negotiated at this level