Re: Ib Physics Past Papers November 1998
Jhuls Morgan
The International Space Station (ISS) is a large space station assembled and maintained in low Earth orbit by a collaboration of five space agencies and their contractors: NASA (United States), Roscosmos (Russia), JAXA (Japan), ESA (Europe), and CSA (Canada). The ISS is the largest space station ever built. Its primary purpose is to perform microgravity and space environment experiments.[12]
Operationally, the station is divided into two sections: the Russian Orbital Segment (ROS) assembled by Roscosmos, and the US Orbital Segment, assembled by NASA, JAXA, ESA and CSA. A striking feature of the ISS is the Integrated Truss Structure, which connects the large solar panels and radiators to the pressurized modules. The pressurized modules are specialized for research, habitation, storage, spacecraft control, and airlock functions. Visiting spacecraft dock at the station via its eight docking and berthing ports. The ISS maintains an orbit with an average altitude of 400 kilometres (250 mi)[13] and circles the Earth in roughly 93 minutes, completing 15.5 orbits per day.[14]
The ISS programme combines two prior plans to construct crewed Earth-orbiting stations: Space Station Freedom planned by the United States, and the Mir-2 station, planned by the Soviet Union. The first ISS module was launched in 1998. Major modules have been launched by Proton and Soyuz rockets and by the Space Shuttle launch system. The first long-term residents, Expedition 1, arrived on November 2, 2000. Since then, the station has been continuously occupied for 23 years and 211 days, the longest continuous human presence in space. As of March 2024[update], 279 individuals from 22 countries have visited the space station.[15] The ISS is expected to have additional modules (the Axiom Orbital Segment, for example) before being de-orbited by a dedicated NASA spacecraft in January 2031.
As the space race drew to a close in the early 1970s, the US and USSR began to contemplate a variety of potential collaborations in outer space. This culminated in the 1975 Apollo-Soyuz Test Project, the first docking of spacecraft from two different spacefaring nations. The ASTP was considered a success, and further joint missions were also contemplated.
One such concept was International Skylab, which proposed launching the backup Skylab B space station for a mission that would see multiple visits by both Apollo and Soyuz crew vehicles.[16] More ambitious was the Skylab-Salyut Space Laboratory, which proposed docking the Skylab B to a Soviet Salyut space station. Falling budgets and rising cold war tensions in the late 1970s saw these concepts fall by the wayside, along with another plan to have the Space Shuttle dock with a Salyut space station.[17]
In early 1985, science ministers from the European Space Agency (ESA) countries approved the Columbus programme, the most ambitious effort in space undertaken by that organization at the time. The plan spearheaded by Germany and Italy included a module which would be attached to Freedom, and with the capability to evolve into a full-fledged European orbital outpost before the end of the century.[19]
Increasing costs threw these plans into doubt in the early 1990s. Congress was unwilling to provide enough money to build and operate Freedom, and demanded NASA increase international participation to defray the rising costs or they would cancel the entire project outright.[20]
Simultaneously, the USSR was conducting planning for the Mir-2 space station, and had begun constructing modules for the new station by the mid 1980s. However the collapse of the Soviet Union required these plans to be greatly downscaled, and soon Mir-2 was in danger of never being launched at all.[21] With both space station projects in jeopardy, American and Russian officials met and proposed they be combined. [22]
The ISS was originally intended to be a laboratory, observatory, and factory while providing transportation, maintenance, and a low Earth orbit staging base for possible future missions to the Moon, Mars, and asteroids. However, not all of the uses envisioned in the initial memorandum of understanding between NASA and Roscosmos have been realised.[30] In the 2010 United States National Space Policy, the ISS was given additional roles of serving commercial, diplomatic,[31] and educational purposes.[32]
The ISS provides a platform to conduct scientific research, with power, data, cooling, and crew available to support experiments. Small uncrewed spacecraft can also provide platforms for experiments, especially those involving zero gravity and exposure to space, but space stations offer a long-term environment where studies can be performed potentially for decades, combined with ready access by human researchers.[33][34]
The ISS simplifies individual experiments by allowing groups of experiments to share the same launches and crew time. Research is conducted in a wide variety of fields, including astrobiology, astronomy, physical sciences, materials science, space weather, meteorology, and human research including space medicine and the life sciences.[35][36][37][38] Scientists on Earth have timely access to the data and can suggest experimental modifications to the crew. If follow-on experiments are necessary, the routinely scheduled launches of resupply craft allows new hardware to be launched with relative ease.[34] Crews fly expeditions of several months' duration, providing approximately 160 person-hours per week of labour with a crew of six. However, a considerable amount of crew time is taken up by station maintenance.[39]
Perhaps the most notable ISS experiment is the Alpha Magnetic Spectrometer (AMS), which is intended to detect dark matter and answer other fundamental questions about our universe. According to NASA, the AMS is as important as the Hubble Space Telescope. Currently docked on station, it could not have been easily accommodated on a free flying satellite platform because of its power and bandwidth needs.[40][41] On 3 April 2013, scientists reported that hints of dark matter may have been detected by the AMS.[42][43][44][45][46][47] According to the scientists, "The first results from the space-borne Alpha Magnetic Spectrometer confirm an unexplained excess of high-energy positrons in Earth-bound cosmic rays".
The space environment is hostile to life. Unprotected presence in space is characterised by an intense radiation field (consisting primarily of protons and other subatomic charged particles from the solar wind, in addition to cosmic rays), high vacuum, extreme temperatures, and microgravity.[48] Some simple forms of life called extremophiles,[49] as well as small invertebrates called tardigrades[50] can survive in this environment in an extremely dry state through desiccation.
Medical research improves knowledge about the effects of long-term space exposure on the human body, including muscle atrophy, bone loss, and fluid shift. These data will be used to determine whether high duration human spaceflight and space colonisation are feasible. In 2006, data on bone loss and muscular atrophy suggested that there would be a significant risk of fractures and movement problems if astronauts landed on a planet after a lengthy interplanetary cruise, such as the six-month interval required to travel to Mars.[51][52]
Medical studies are conducted aboard the ISS on behalf of the National Space Biomedical Research Institute (NSBRI). Prominent among these is the Advanced Diagnostic Ultrasound in Microgravity study in which astronauts perform ultrasound scans under the guidance of remote experts. The study considers the diagnosis and treatment of medical conditions in space. Usually, there is no physician on board the ISS and diagnosis of medical conditions is a challenge. It is anticipated that remotely guided ultrasound scans will have application on Earth in emergency and rural care situations where access to a trained physician is difficult.[53][54][55]
In August 2020, scientists reported that bacteria from Earth, particularly Deinococcus radiodurans bacteria, which is highly resistant to environmental hazards, were found to survive for three years in outer space, based on studies conducted on the International Space Station. These findings supported the notion of panspermia, the hypothesis that life exists throughout the Universe, distributed in various ways, including space dust, meteoroids, asteroids, comets, planetoids or contaminated spacecraft.[56][57]
Remote sensing of the Earth, astronomy, and deep space research on the ISS have significantly increased during the 2010s after the completion of the US Orbital Segment in 2011. Throughout the more than 20 years of the ISS program, researchers aboard the ISS and on the ground have examined aerosols, ozone, lightning, and oxides in Earth's atmosphere, as well as the Sun, cosmic rays, cosmic dust, antimatter, and dark matter in the universe. Examples of Earth-viewing remote sensing experiments that have flown on the ISS are the Orbiting Carbon Observatory 3, ISS-RapidScat, ECOSTRESS, the Global Ecosystem Dynamics Investigation, and the Cloud Aerosol Transport System. ISS-based astronomy telescopes and experiments include SOLAR, the Neutron Star Interior Composition Explorer, the Calorimetric Electron Telescope, the Monitor of All-sky X-ray Image (MAXI), and the Alpha Magnetic Spectrometer.[35][58]
Gravity at the altitude of the ISS is approximately 90% as strong as at Earth's surface, but objects in orbit are in a continuous state of freefall, resulting in an apparent state of weightlessness.[59] This perceived weightlessness is disturbed by five effects:[60]
Researchers are investigating the effect of the station's near-weightless environment on the evolution, development, growth and internal processes of plants and animals. In response to some of the data, NASA wants to investigate microgravity's effects on the growth of three-dimensional, human-like tissues and the unusual protein crystals that can be formed in space.[35]
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