Space habitat. A type of space station, intended as a permanent settlement Interior view of an O'Neill cylinder, showing alternating land and window stripes A space habitat (also called a space colony, space settlement, orbital habitat, orbital settlement or orbital colony) is a type of space station, intended as a permanent settlement rather than as a simple way-station or other specialized facility. No space habitat has been constructed yet, but many design concepts, with varying degrees of realism, have come both from engineers and from science-fiction authors.
The term space habitat sometimes includes more broadly colonies built on or in a body other than Earth—such as the Moon, Mars or an asteroid. This article concentrates on self-contained structures envisaged for micro-g environments. Motivation[edit] Several motivations for building space colonies have been proposed: (See: Reasons for space colonization or Space and survival.)
Advantages[edit] Access to solar energy[edit] Outside gravity well[edit] Asteroid mining. Artist's concept of asteroid mining Asteroid mining is the exploitation of raw materials from asteroids and other minor planets, including near-Earth objects.[1] Minerals and volatiles could be mined from an asteroid or spent comet then used in space for in-situ utilization (e.g. construction materials and rocket propellant) or taken back to Earth. These include gold, iridium, silver, osmium, palladium, platinum, rhenium, rhodium, ruthenium and tungsten for transport back to Earth; iron, cobalt, manganese, molybdenum, nickel, aluminium, and titanium for construction; water and oxygen to sustain astronauts; as well as hydrogen, ammonia, and oxygen for use as rocket propellant. Due to the high costs of current space transportation, extraction techniques still being developed and lingering uncertainties about target selection, terrestrial mining is currently the only means of raw mineral acquisition today.
Purpose[edit] Asteroid selection[edit] Asteroid cataloging[edit] Surface mining[edit] Comet. Natural object in space that releases gas Comets usually have highly eccentric elliptical orbits, and they have a wide range of orbital periods, ranging from several years to potentially several millions of years. Short-period comets originate in the Kuiper belt or its associated scattered disc, which lie beyond the orbit of Neptune.
Long-period comets are thought to originate in the Oort cloud, a spherical cloud of icy bodies extending from outside the Kuiper belt to halfway to the nearest star.[2] Long-period comets are set in motion towards the Sun by gravitational perturbations from passing stars and the galactic tide. Hyperbolic comets may pass once through the inner Solar System before being flung to interstellar space. Etymology The word comet derives from the Old English cometa from the Latin comēta or comētēs. The astronomical symbol for comets (represented in Unicode) is U+2604 ☄ COMET, consisting of a small disc with three hairlike extensions.[15] Physical characteristics Coma. Galactic tide.
A galactic tide is tidal force experienced by objects subject to the gravitational field of a galaxy such as the Milky Way. Particular areas of interest concerning galactic tides include galactic collisions, the disruption of dwarf or satellite galaxies, and the Milky Way's tidal effect on the Oort cloud of the Solar System. Effects on external galaxies[edit] Galaxy collisions[edit] Tidal forces are dependent on the gradient of a gravitational field, rather than its strength, and so tidal effects are usually limited to the immediate surroundings of a galaxy. Two large galaxies undergoing collisions or passing nearby each other will be subjected to very large tidal forces, often producing the most visually striking demonstrations of galactic tides in action.
Two interacting galaxies will not always collide head-on (if at all), and the tidal forces will distort each galaxy along an axis pointing roughly towards and away from its perturber. Satellite interactions[edit] The Andromeda Galaxy. Solar System. The Sun and objects orbiting it The Solar System was formed 4.6 billion years ago from the gravitational collapse of a giant interstellar molecular cloud. Over time, the cloud formed the Sun and a protoplanetary disk that gradually coalesced to form planets and other objects.
That is the reason why all eight planets have an orbit that lies near the same plane. In the present day, 99.86% of the Solar System's mass is in the Sun and most of the remaining mass is contained in the planet Jupiter. Six planets and many other bodies have natural satellites or moons orbiting around them. All of the giant planets and a few smaller bodies are encircled by planetary rings, composed of ice, dust and sometimes moonlets. Formation and evolution Due to their higher boiling points, only metals and silicates could exist in solid form in the warm inner Solar System close to the Sun, and these would eventually form the rocky planets of Mercury, Venus, Earth, and Mars. Structure and composition Orbits Sun Venus.
Earth. Third planet from the Sun Earth is the third planet from the Sun and the only astronomical object known to harbor life. This is enabled by Earth being a water world, the only one in the Solar System sustaining liquid surface water. Almost all of Earth's water is contained in its global ocean, covering 70.8% of Earth's crust.
The remaining 29.2% of Earth's crust is land, most of which is located in the form of continental landmasses within one hemisphere, Earth's land hemisphere. Earth has a dynamic atmosphere, which sustains Earth's surface conditions and protects it from most meteoroids and UV-light at entry. Earth is rounded into an ellipsoid with a circumference of about 40,000 km. Earth, like most other bodies in the Solar System, formed 4.5 billion years ago from gas in the early Solar System. Etymology Historically, "earth" has been written in lowercase. There are a number of adjectives for the planet Earth. Natural history Formation After formation Origin of life and evolution Future. Terminator (solar) Video of the Earth from the ISS as it approaches the terminator. Supersonic aircraft like jet fighters or Concorde and Tupolev Tu-144 supersonic transports are the only aircraft able to overtake the maximum speed of the terminator.
However, slower vehicles can overtake the terminator at higher latitudes, and it is possible to walk faster than the terminator at the poles, near to the equinoxes. The visual effect is that of seeing the Sun rise in the west, or set in the east. Examination of a terminator can yield information about the surface of a planetary body; for example, the presence of an atmosphere can create a fuzzier terminator. Low Earth orbit satellites take advantage of the fact that certain polar orbits set near the terminator do not suffer from eclipse, therefore their solar cells are continuously lit by sunlight. Ground track. Moon. Natural satellite orbiting the Earth Both the Moon's prominence in Earth's sky and its regular cycle of phases have provided cultural references and influences for human societies throughout history.
Such influences can be found in language, calendar systems, art, and mythology. The first artificial object to reach the Moon was the Soviet Union's uncrewed Luna 2 spacecraft in 1959; this was followed by the first successful soft landing by Luna 9 in 1966. The only human lunar missions to date have been those of the United States' Apollo program, which landed twelve men on the surface between 1969 and 1972. These and later uncrewed missions returned lunar rocks that have been used to develop a detailed geological understanding of the Moon's origins, internal structure, and subsequent history. Names and etymology The usual English adjective pertaining to the Moon is "lunar", derived from the Latin word for the Moon, lūna. The astronomical symbol for the Moon is a crescent, Natural history.