1.
NASA
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President Dwight D. Eisenhower established NASA in 1958 with a distinctly civilian orientation encouraging peaceful applications in space science. The National Aeronautics and Space Act was passed on July 29,1958, disestablishing NASAs predecessor, the new agency became operational on October 1,1958. Since that time, most US space exploration efforts have led by NASA, including the Apollo Moon landing missions, the Skylab space station. Currently, NASA is supporting the International Space Station and is overseeing the development of the Orion Multi-Purpose Crew Vehicle, the agency is also responsible for the Launch Services Program which provides oversight of launch operations and countdown management for unmanned NASA launches. NASA shares data with various national and international such as from the Greenhouse Gases Observing Satellite. Since 2011, NASA has been criticized for low cost efficiency, from 1946, the National Advisory Committee for Aeronautics had been experimenting with rocket planes such as the supersonic Bell X-1. In the early 1950s, there was challenge to launch a satellite for the International Geophysical Year. An effort for this was the American Project Vanguard, after the Soviet launch of the worlds first artificial satellite on October 4,1957, the attention of the United States turned toward its own fledgling space efforts. This led to an agreement that a new federal agency based on NACA was needed to conduct all non-military activity in space. The Advanced Research Projects Agency was created in February 1958 to develop technology for military application. On July 29,1958, Eisenhower signed the National Aeronautics and Space Act, a NASA seal was approved by President Eisenhower in 1959. Elements of the Army Ballistic Missile Agency and the United States Naval Research Laboratory were incorporated into NASA, earlier research efforts within the US Air Force and many of ARPAs early space programs were also transferred to NASA. In December 1958, NASA gained control of the Jet Propulsion Laboratory, NASA has conducted many manned and unmanned spaceflight programs throughout its history. Some missions include both manned and unmanned aspects, such as the Galileo probe, which was deployed by astronauts in Earth orbit before being sent unmanned to Jupiter, the experimental rocket-powered aircraft programs started by NACA were extended by NASA as support for manned spaceflight. This was followed by a space capsule program, and in turn by a two-man capsule program. This goal was met in 1969 by the Apollo program, however, reduction of the perceived threat and changing political priorities almost immediately caused the termination of most of these plans. NASA turned its attention to an Apollo-derived temporary space laboratory, to date, NASA has launched a total of 166 manned space missions on rockets, and thirteen X-15 rocket flights above the USAF definition of spaceflight altitude,260,000 feet. The X-15 was an NACA experimental rocket-powered hypersonic research aircraft, developed in conjunction with the US Air Force, the design featured a slender fuselage with fairings along the side containing fuel and early computerized control systems
2.
Orbital Sciences Corporation
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It was headquartered in Dulles, Virginia and publicly traded on the New York Stock Exchange with the ticker symbol OA. Orbital also provided satellite subsystems and space-related technical services to government agencies and laboratories, on April 29,2014, Orbital Sciences announced that it would merge with Alliant Techsystems to create a new company called Orbital ATK, Inc. The merger was completed on February 9,2015 and Orbital Sciences ceased to exist as an independent entity, Orbital was founded and incorporated in 1982 by three friends who had met earlier while at Harvard Business School—David W. Thompson, Bruce Ferguson and Scott Webster. In 1985, Orbital procured its first contract for providing up to four Transfer Orbital Stage vehicles to NASA, in 1987, the seeds for the ORBCOMM constellation were planted when Orbital began investigating a system using Low Earth orbit satellites to collect data from remote locations. In 1988, Orbital acquired Space Data Corporation in Arizona- one of the leading suppliers of suborbital rockets- thereby broadening its rocket business. This was followed by the opening of a new facility in Chandler, in 1990, the company successfully carried out eight space missions, highlighted by the initial launch of the Pegasus rocket, the worlds first privately developed space launch vehicle. Shortly following the successful Pegasus launch, Orbital conducted an IPO in 1990, in 1993, Orbital established its current headquarters in Dulles, Virginia followed by the acquisition of Fairchild Space and Defense Corporation in 1994. In the same year, Orbital successfully conducted the launch of the Taurus rocket. In the early 2000s, Orbital continued expanding its missile defense systems business with a $900 million award to develop, build, test and support interceptor booster vehicles. In 2006 Orbital conducted its 500th mission since the founding with a diverse portfolio of products that included satellites, launch vehicles. Orbital is currently on-track to deliver on this contract with its Cygnus spacecraft and Antares rocket following the success of Cygnus Orb-D1, the new company will be called Orbital ATK, Inc. and will serve U. S. Orbital was a provider of small- to medium-class satellites, since the companys founding in 1982, Orbital has delivered 150 spacecraft to commercial, military and civil customers worldwide. To date, these spacecraft have amassed well over 1000 years of on-orbit operations, the Communications & Imaging Satellites developed by Orbital are smaller and more affordable. Earth imagery and high resolution digital imaging satellites such as the OrbView series are developed and manufactured by Orbital. In the last 10 years, Orbital has built more scientific, Orbitals space launch vehicles are considered the industry standard for boosting small payloads to orbit. The Minotaur ground-launched rockets combine Pegasus upper stages with either government-supplied or commercially available first-stage rocket motors to boost larger payloads to orbit, Minotaur IV combines decommissioned Peacekeeper rocket motors with proven Orbital avionics and fairings to provide increased lifting capacity for government-sponsored payloads. With the development of the Antares space launch vehicle, Orbital is extending its capabilities to provide launch services for U. S. government. The inaugural launch of Antares occurred on April 21,2013 from Wallops Flight Facility at Wallops Island, Orbital is also a major provider of suborbital target and interceptor launch vehicles for the U. S. missile defense systems
3.
Pegasus (rocket)
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The Pegasus is an air-launched rocket developed by Orbital ATK, formerly Orbital Sciences Corporation. Capable of carrying payloads of up to 443 kilograms into low Earth orbit, Pegasus first flew in 1990. The vehicle consists of three solid propellant stages and an optional monopropellant fourth stage, Pegasus is released from its carrier aircraft at approximately 40,000 ft, and its first stage has wings and a tail to provide lift and attitude control while in the atmosphere. The Pegasuss three Orion solid motors were developed by Hercules Aerospace specifically for the Pegasus launcher, additionally, wing and tail assemblies and a payload fairing were developed. Most of the Pegasus was designed by a led by Dr. Antonio Elias. The wing was designed by Burt Rutan, mass,18,500 kg,23,130 kg Length,16.9 m,17.6 m Diameter,1.27 m Wing span,6. Soon after development began, several government and military orders were placed, the first successful Pegasus launch occurred on April 5,1990 with NASA test pilot and former astronaut Gordon Fullerton in command of the carrier aircraft. Initially, a NASA-owned B-52 Stratofortress NB-008 served as the carrier aircraft, by 1994, Orbital had transitioned to their Stargazer L-1011, a converted airliner which was formerly owned by Air Canada. Initially, the Pegasus program had a failure rate, about 40% until 1997. It lost six different cargoes, starting with 7 microsatellites on its second attempt, included was at least partial failure of three out of four Space Test Experiment Platform efforts in the 1990s, on three separate launches. The Pegasus XL, introduced in 1994 has lengthened stages to increase payload performance, in the Pegasus XL, the first and second stages are lengthened into the Orion 50SXL and Orion 50XL, respectively. Higher stages are unchanged, flight operations are similar, the wing is strengthened slightly to handle the higher weight. The standard Pegasus has been discontinued, the Pegasus XL is still being produced, Pegasus has flown 42 missions in both configurations as of June 28,2013. Of these,37 were considered successful launches, dual payloads can be launched, with a canister that encloses the lower spacecraft and mounts the upper spacecraft. The upper spacecraft deploys, the canister opens, then the lower spacecraft separates from the third-stage adapter, since the fairing is unchanged for cost and aerodynamic reasons, each of the two payloads must be relatively compact. For their work in developing the rocket, the Pegasus team led by Dr. Antonio Elias was awarded the 1991 National Medal of Technology by U. S. President George H. W. Bush. The initial launch price offered was US$6 million, without options or a HAPS maneuvering stage, with the enlargement to Pegasus XL and the associated improvements to the vehicle, baseline prices increased. In addition, customers usually purchase additional services, such as testing, design and analysis
4.
Explorers program
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The Explorers program is a United States space exploration program that provides flight opportunities for physics, geophysics, heliophysics, and astrophysics investigations from space. Over 90 space missions have launched since 1958, and it is still active. Starting with Explorer 6, it has operated by NASA, with regular collaboration with a variety of other institutions. The Explorers program was the United Statess first successful attempt to launch an artificial satellite. It began as a U. S. Army proposal to place a satellite into orbit during the International Geophysical Year, however. The Explorers program was reestablished to catch up with the Soviet Union after that nations launch of Sputnik 1 on October 4,1957. Explorer 1 was launched on January 31,1958, besides being the first U. S. satellite, it is known for discovering the Van Allen radiation belt. Over the years, NASA has launched a series of Explorers spacecraft carrying a variety of scientific investigations. These missions have also investigated air density, radio astronomy, geodesy, various space telescopes have made a variety of discoveries, including the first known Earth Trojan asteroid. The Explorers Program Office at Goddard Space Flight Center in Greenbelt, Maryland, Explorers categories have included MIDEX, SMEX, UNEX, and others. A subprogram called Missions of Opportunity has funded instruments on non-NASA missions, launchers used for these missions include Jupiter C, Juno II, various Thor rockets such as the Thor-Able, Scout, various Delta and Delta II rockets of the Delta rocket family, and Pegasus. The Medium-Class Explorer program is an effort within NASA to fund space exploration missions that cost no more than US$180 million, list of MIDEX missions The Small Explorer program is an effort within NASA to fund space exploration missions that cost no more than US$120 million. The first set of three SMEX missions were launched between 1992 and 1998, the second set of two missions were launched in 1998 and 1999. These missions were managed by the Small Explorer Project Office at NASAs Goddard Space Flight Center, list of SMEX missions Investigations characterized by definition, development, mission operations, and data analysis costs not to exceed $15. 0M total cost to NASA. UNEX missions will be launched by a variety of low cost methods, list of UNEX missions The Missions of Opportunity program provides funding for science instruments or hardware components of onboard non-NASA space missions. MO missions have a total NASA cost of under $55 million, list of MO missions Explorers name numbers can be found in the NSSDC master catalog, typically assigned to each spacecraft in a mission. These numbers were not officially assigned until after 1975, many missions are proposed, but not selected. For example, in 2011, the Explorers program received 22 full missions solicitations,20 Missions of Opportunity, Missions of Opportunity are small collaborative missions with spacecraft not operated by NASA, such as an additional instrument
5.
Aeronomy of Ice in the Mesosphere
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The Aeronomy of Ice in the Mesosphere is a satellite to conduct a 26-month study of noctilucent clouds. It is the ninetieth Explorer program mission and is part of the NASA-funded Small Explorer program, on April 25,2007 AIM was boosted into a 600 km high polar orbit by a Pegasus-XL rocket, which was air-launched from the Lockheed L-1011 Stargazer aircraft operated by Orbital Sciences. The AIM satellite is a 200 kg,1.4 m by 1, the AIM mission will help determine what factors — temperature, water vapor, and dust particles — lead to the formation of these clouds. The clouds seem to be a recent phenomenon, they were first seen in 1885. The clouds always occur during the season near the poles. Scientists have found that the start of the Southern season can vary up to a month however, AIM home SOFIE Instrument and science description, view or download data AIM Mission Profile by NASAs Solar System Exploration
6.
Wide-field Infrared Survey Explorer
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Wide-field Infrared Survey Explorer is a NASA infrared-wavelength astronomical space telescope launched in December 2009, and placed in hibernation in February 2011 when its transmitter turned off. WISE discovered thousands of planets and numerous star clusters. Its observations also supported the discovery of the first Y Dwarf, WISE performed an all-sky astronomical survey with images in 3.4,4.6,12 and 22 μm wavelength range bands, over ten months using a 40 cm diameter infrared telescope in Earth orbit. After its hydrogen coolant depleted, a mission extension called NEOWISE was conducted to search for near-Earth objects such as comets. The All-Sky data including processed images, source catalogs and raw data, was released to the public on March 14,2012, in August 2013, NASA announced it would reactivate the WISE telescope for a new three-year mission to search for asteroids that could collide with Earth. Science operations and data processing for WISE and NEOWISE take place at the Infrared Processing, the mission was planned to create infrared images of 99 percent of the sky, with at least eight images made of each position on the sky in order to increase accuracy. The spacecraft was placed in a 525 km, circular, polar, Sun-synchronous orbit for its mission, during which it has taken 1.5 million images. Each image covers a 47-arcminute field of view, which means a 6-arcsecond resolution, each area of the sky was scanned at least 10 times at the equator, the poles were scanned at theoretically every revolution due to the overlapping of the images. The produced image library contains data on the local Solar System, the Milky Way, among the objects WISE studied are asteroids, cool, dim stars such as brown dwarfs, and the most luminous infrared galaxies. Stellar nurseries, which are covered by interstellar dust, are detectable in infrared, Infrared measurements from the WISE astronomical survey have been particularly effective at unveiling previously undiscovered star clusters. Examples of such embedded star clusters are Camargo 18, Camargo 440, Majaess 101, in addition, galaxies of the young Universe and interacting galaxies, where star formation is intensive, are bright in infrared. On this wavelength the interstellar gas clouds are also detectable, as well as proto-planetary discs, WISE satellite was expected to find at least 1,000 of those proto-planetary discs. WISE was not able to detect Kuiper belt objects, because their temperatures are too low and it was able to detect any objects warmer than 70–100 K. A Neptune-sized object would be out to 700 AU, a Jupiter-mass object out to 1 light year. A larger object of 2–3 Jupiter masses would be visible at a distance of up to 7–10 light years and that translates to about 1000 new main-belt asteroids per day, and 1–3 NEOs per day. The peak of magnitude distribution for NEOs will be about 21–22 V, WISE would detect each typical Solar System object 10–12 times over about 36 hours in intervals of 3 hours. Construction of the WISE telescope was divided between Ball Aerospace & Technologies, SSG Precision Optronics, Inc, DRS and Rockwell, Lockheed Martin, and Space Dynamics Laboratory. The program was managed through the Jet Propulsion Laboratory, the WISE instrument was built by the Space Dynamics Laboratory in Logan, Utah
7.
Solar System
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The Solar System is the gravitationally bound system comprising the Sun and the objects that orbit it, either directly or indirectly. Of those objects that orbit the Sun directly, the largest eight are the planets, with the remainder being significantly smaller objects, such as dwarf planets, of the objects that orbit the Sun indirectly, the moons, two are larger than the smallest planet, Mercury. The Solar System formed 4.6 billion years ago from the collapse of a giant interstellar molecular cloud. The vast majority of the mass is in the Sun. The four smaller inner planets, Mercury, Venus, Earth and Mars, are terrestrial planets, being composed of rock. The four outer planets are giant planets, being more massive than the terrestrials. All planets have almost circular orbits that lie within a flat disc called the ecliptic. The Solar System also contains smaller objects, the asteroid belt, which lies between the orbits of Mars and Jupiter, mostly contains objects composed, like the terrestrial planets, of rock and metal. Beyond Neptunes orbit lie the Kuiper belt and scattered disc, which are populations of trans-Neptunian objects composed mostly of ices, within these populations are several dozen to possibly tens of thousands of objects large enough that they have been rounded by their own gravity. Such objects are categorized as dwarf planets, identified dwarf planets include the asteroid Ceres and the trans-Neptunian objects Pluto and Eris. In addition to two regions, various other small-body populations, including comets, centaurs and interplanetary dust clouds. Six of the planets, at least four of the dwarf planets, each of the outer planets is encircled by planetary rings of dust and other small objects. The solar wind, a stream of charged particles flowing outwards from the Sun, the heliopause is the point at which pressure from the solar wind is equal to the opposing pressure of the interstellar medium, it extends out to the edge of the scattered disc. The Oort cloud, which is thought to be the source for long-period comets, the Solar System is located in the Orion Arm,26,000 light-years from the center of the Milky Way. For most of history, humanity did not recognize or understand the concept of the Solar System, the invention of the telescope led to the discovery of further planets and moons. The principal component of the Solar System is the Sun, a G2 main-sequence star that contains 99. 86% of the known mass. The Suns four largest orbiting bodies, the giant planets, account for 99% of the mass, with Jupiter. The remaining objects of the Solar System together comprise less than 0. 002% of the Solar Systems total mass, most large objects in orbit around the Sun lie near the plane of Earths orbit, known as the ecliptic
8.
Outer space
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Outer space or just space, is the void that exists between celestial bodies, including Earth. The baseline temperature, as set by the radiation from the Big Bang, is 2.7 kelvins. In most galaxies, observations provide evidence that 90% of the mass is in a form, called dark matter. Data indicates that the majority of the mass-energy in the universe is a poorly understood vacuum energy of space which astronomers label dark energy. Intergalactic space takes up most of the volume of the Universe, there is no firm boundary where outer space starts. However the Kármán line, at an altitude of 100 km above sea level, is used as the start of outer space in space treaties. The framework for international law was established by the Outer Space Treaty. This treaty precludes any claims of sovereignty and permits all states to freely explore outer space. Despite the drafting of UN resolutions for the uses of outer space. Humans began the exploration of space during the 20th century with the advent of high-altitude balloon flights. Earth orbit was first achieved by Yuri Gagarin of the Soviet Union in 1961, due to the high cost of getting into space, manned spaceflight has been limited to low Earth orbit and the Moon. Outer space represents an environment for human exploration because of the dual hazards of vacuum. Microgravity also has an effect on human physiology that causes both muscle atrophy and bone loss. In addition to health and environmental issues, the economic cost of putting objects, including humans. In 350 BCE, Greek philosopher Aristotle suggested that nature abhors a vacuum and this concept built upon a 5th-century BCE ontological argument by the Greek philosopher Parmenides, who denied the possible existence of a void in space. Based on this idea that a vacuum could not exist, in the West it was held for many centuries that space could not be empty. As late as the 17th century, the French philosopher René Descartes argued that the entirety of space must be filled, in ancient China, there were various schools of thought concerning the nature of the heavens, some of which bear a resemblance to the modern understanding. In the 2nd century, astronomer Zhang Heng became convinced that space must be infinite, extending well beyond the mechanism that supported the Sun, the surviving books of the Hsüan Yeh school said that the heavens were boundless, empty and void of substance
9.
Moon
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The Moon is an astronomical body that orbits planet Earth, being Earths only permanent natural satellite. It is the fifth-largest natural satellite in the Solar System, following Jupiters satellite Io, the Moon is second-densest satellite among those whose densities are known. The average distance of the Moon from the Earth is 384,400 km, the Moon is thought to have formed about 4.51 billion years ago, not long after Earth. It is the second-brightest regularly visible celestial object in Earths sky, after the Sun and its surface is actually dark, although compared to the night sky it appears very bright, with a reflectance just slightly higher than that of worn asphalt. Its prominence in the sky and its cycle of phases have made the Moon an important cultural influence since ancient times on language, calendars, art. The Moons gravitational influence produces the ocean tides, body tides, and this matching of apparent visual size will not continue in the far future. The Moons linear distance from Earth is currently increasing at a rate of 3.82 ±0.07 centimetres per year, since the Apollo 17 mission in 1972, the Moon has been visited only by uncrewed spacecraft. The usual English proper name for Earths natural satellite is the Moon, the noun moon is derived from moone, which developed from mone, which is derived from Old English mōna, which ultimately stems from Proto-Germanic *mǣnōn, like all Germanic language cognates. Occasionally, the name Luna is used, in literature, especially science fiction, Luna is used to distinguish it from other moons, while in poetry, the name has been used to denote personification of our moon. The principal modern English adjective pertaining to the Moon is lunar, a less common adjective is selenic, derived from the Ancient Greek Selene, from which is derived the prefix seleno-. Both the Greek Selene and the Roman goddess Diana were alternatively called Cynthia, the names Luna, Cynthia, and Selene are reflected in terminology for lunar orbits in words such as apolune, pericynthion, and selenocentric. The name Diana is connected to dies meaning day, several mechanisms have been proposed for the Moons formation 4.51 billion years ago, and some 60 million years after the origin of the Solar System. These hypotheses also cannot account for the angular momentum of the Earth–Moon system. This hypothesis, although not perfect, perhaps best explains the evidence, eighteen months prior to an October 1984 conference on lunar origins, Bill Hartmann, Roger Phillips, and Jeff Taylor challenged fellow lunar scientists, You have eighteen months. Go back to your Apollo data, go back to computer, do whatever you have to. Dont come to our conference unless you have something to say about the Moons birth, at the 1984 conference at Kona, Hawaii, the giant impact hypothesis emerged as the most popular. Afterward there were only two groups, the giant impact camp and the agnostics. Giant impacts are thought to have been common in the early Solar System, computer simulations of a giant impact have produced results that are consistent with the mass of the lunar core and the present angular momentum of the Earth–Moon system
10.
Energetic neutral atom
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This constitutes the far-flung edge of the solar system. The solar wind consists of ripped-apart atoms flying out of the Sun and this is mostly hydrogen, that is, bare electrons and protons, with a little bit of other kinds of nuclei, mostly helium. The space between systems is similar, but they come from other stars in our galaxy. These charged particles can be redirected by magnetic fields, for instance, but, every so often, a few of them steal electrons from neutral atoms they run into. At that point, they become neutral, although theyre still moving very fast and these are called Energetic Neutral Atoms. ENA images are constructed from the detection of these energetic neutral atoms, Earths magnetosphere preserves Earths atmosphere and protects us from cell-damaging radiation. This region of space weather is the site of geomagnetic storms that disrupt communications systems, a deeper understanding of this region is vitally important. The heliosphere protects the entire Solar System from the majority of cosmic rays but is so remote that only an imaging technique such as ENA imaging will reveal its properties. The heliospheres structure is due to the interaction between the solar wind and cold gas from the local interstellar medium. The creation of ENAs by space plasmas was predicted but their discovery was both deliberate and serendipitous, while some early efforts were made at detection, their signatures also explained inconsistent findings by ion detectors in regions of expected low ion populations. Ion detectors were co-opted for further ENA detection experiments in other low-ion regions, however, the development of dedicated ENA detectors entailed overcoming significant obstacles in both skepticism and technology. Although ENAs were observed in space from the 1960s through 1980s, today, dedicated ENA instruments have provided detailed magnetospheric images from Venus, Mars, Jupiter, and Saturn. Cassinis ENA images of Saturn revealed a unique magnetosphere with complex interactions that have yet to be fully explained, the first ever images of the heliospheric boundary, published in October 2009, were made by the ENA instruments aboard the IBEX and Cassini spacecraft. These images are very exciting because they challenge existing theories about the region, the most abundant ion in space plasmas is the hydrogen ion—a bare proton with no excitable electrons to emit visible photons. The occasional visibility of other ions is not sufficient for imaging purposes. ENAs are created in charge-exchange collisions between hot solar plasma ions and a neutral background gas. These charge-exchange processes occur with frequency in planetary magnetospheres and at the edge of the heliosphere. In a charge-exchange collision between a high energy plasma ion and a neutral atom, the ion steals electrons from the neutral atom, producing a cold ion
11.
Hydrogen
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Hydrogen is a chemical element with chemical symbol H and atomic number 1. With a standard weight of circa 1.008, hydrogen is the lightest element on the periodic table. Its monatomic form is the most abundant chemical substance in the Universe, non-remnant stars are mainly composed of hydrogen in the plasma state. The most common isotope of hydrogen, termed protium, has one proton, the universal emergence of atomic hydrogen first occurred during the recombination epoch. At standard temperature and pressure, hydrogen is a colorless, odorless, tasteless, non-toxic, nonmetallic, since hydrogen readily forms covalent compounds with most nonmetallic elements, most of the hydrogen on Earth exists in molecular forms such as water or organic compounds. Hydrogen plays an important role in acid–base reactions because most acid-base reactions involve the exchange of protons between soluble molecules. In ionic compounds, hydrogen can take the form of a charge when it is known as a hydride. The hydrogen cation is written as though composed of a bare proton, Hydrogen gas was first artificially produced in the early 16th century by the reaction of acids on metals. Industrial production is mainly from steam reforming natural gas, and less often from more energy-intensive methods such as the electrolysis of water. Most hydrogen is used near the site of its production, the two largest uses being fossil fuel processing and ammonia production, mostly for the fertilizer market, Hydrogen is a concern in metallurgy as it can embrittle many metals, complicating the design of pipelines and storage tanks. Hydrogen gas is flammable and will burn in air at a very wide range of concentrations between 4% and 75% by volume. The enthalpy of combustion is −286 kJ/mol,2 H2 + O2 →2 H2O +572 kJ Hydrogen gas forms explosive mixtures with air in concentrations from 4–74%, the explosive reactions may be triggered by spark, heat, or sunlight. The hydrogen autoignition temperature, the temperature of spontaneous ignition in air, is 500 °C, the detection of a burning hydrogen leak may require a flame detector, such leaks can be very dangerous. Hydrogen flames in other conditions are blue, resembling blue natural gas flames, the destruction of the Hindenburg airship was a notorious example of hydrogen combustion and the cause is still debated. The visible orange flames in that incident were the result of a mixture of hydrogen to oxygen combined with carbon compounds from the airship skin. H2 reacts with every oxidizing element, the ground state energy level of the electron in a hydrogen atom is −13.6 eV, which is equivalent to an ultraviolet photon of roughly 91 nm wavelength. The energy levels of hydrogen can be calculated fairly accurately using the Bohr model of the atom, however, the atomic electron and proton are held together by electromagnetic force, while planets and celestial objects are held by gravity. The most complicated treatments allow for the effects of special relativity
12.
Oxygen
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Oxygen is a chemical element with symbol O and atomic number 8. It is a member of the group on the periodic table and is a highly reactive nonmetal. By mass, oxygen is the third-most abundant element in the universe, after hydrogen, at standard temperature and pressure, two atoms of the element bind to form dioxygen, a colorless and odorless diatomic gas with the formula O2. This is an important part of the atmosphere and diatomic oxygen gas constitutes 20. 8% of the Earths atmosphere, additionally, as oxides the element makes up almost half of the Earths crust. Most of the mass of living organisms is oxygen as a component of water, conversely, oxygen is continuously replenished by photosynthesis, which uses the energy of sunlight to produce oxygen from water and carbon dioxide. Oxygen is too reactive to remain a free element in air without being continuously replenished by the photosynthetic action of living organisms. Another form of oxygen, ozone, strongly absorbs ultraviolet UVB radiation, but ozone is a pollutant near the surface where it is a by-product of smog. At low earth orbit altitudes, sufficient atomic oxygen is present to cause corrosion of spacecraft, the name oxygen was coined in 1777 by Antoine Lavoisier, whose experiments with oxygen helped to discredit the then-popular phlogiston theory of combustion and corrosion. One of the first known experiments on the relationship between combustion and air was conducted by the 2nd century BCE Greek writer on mechanics, Philo of Byzantium. In his work Pneumatica, Philo observed that inverting a vessel over a burning candle, Philo incorrectly surmised that parts of the air in the vessel were converted into the classical element fire and thus were able to escape through pores in the glass. Many centuries later Leonardo da Vinci built on Philos work by observing that a portion of air is consumed during combustion and respiration, Oxygen was discovered by the Polish alchemist Sendivogius, who considered it the philosophers stone. In the late 17th century, Robert Boyle proved that air is necessary for combustion, English chemist John Mayow refined this work by showing that fire requires only a part of air that he called spiritus nitroaereus. From this he surmised that nitroaereus is consumed in both respiration and combustion, Mayow observed that antimony increased in weight when heated, and inferred that the nitroaereus must have combined with it. Accounts of these and other experiments and ideas were published in 1668 in his work Tractatus duo in the tract De respiratione. Robert Hooke, Ole Borch, Mikhail Lomonosov, and Pierre Bayen all produced oxygen in experiments in the 17th and the 18th century but none of them recognized it as a chemical element. This may have been in part due to the prevalence of the philosophy of combustion and corrosion called the phlogiston theory, which was then the favored explanation of those processes. Established in 1667 by the German alchemist J. J. Becher, one part, called phlogiston, was given off when the substance containing it was burned, while the dephlogisticated part was thought to be its true form, or calx. The fact that a substance like wood gains overall weight in burning was hidden by the buoyancy of the combustion products
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