Artificial gravity is a simulation of gravity in outer space or free-fall. Artificial gravity is desirable for long-term space travel for ease of mobility and to avoid the adverse health effects of weightlessness. Gravity redirects here. ... Layers of Atmosphere - not to scale (NOAA)[1] Outer space, sometimes simply called space, refers to the relatively empty regions of the universe outside the atmospheres of celestial bodies. ... Free Fall opens with one of the most stunning first paragraphs I have ever, or am ever likely to, read. ... Astronauts on the International Space Station display an example of weightlessness. ...

Methods

Artificial gravity could be created in several ways:

Rotation

Artist's conception of the interior of a Stanford torus with a diameter of 1.8 kilometers (1.1 miles) and revolves at 1 rpm to produce 1g

A rotating spacecraft will produce the feeling of gravity on its inside hull. The rotation drives any object inside the spacecraft toward the hull thereby giving the appearance of a gravitational pull directed outward. Often referred to as a centrifugal force, the "pull" is actually a manifestation of the objects inside the spacecraft attempting to travel in a straight line due to inertia. The spacecraft's hull provides the centripetal force required for the objects to travel in a circle (if they continued in a straight line they would leave the spacecraft's confines). Thus, the gravity felt by the objects is simply the reaction force of the object on the hull reacting to the centripetal force of the hull on the object, in accordance with Newton's Third Law. Image File history File links Download high-resolution version (1600x1190, 641 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Space colonization Space habitat Stanford torus Artificial gravity User:N35w101 Portal:Space Portal:Space/Selected/Article The High... Image File history File links Download high-resolution version (1600x1190, 641 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Space colonization Space habitat Stanford torus Artificial gravity User:N35w101 Portal:Space Portal:Space/Selected/Article The High... Exterior view of a Stanford torus. ... Centrifugal force (from Latin centrum centre and fugere to flee) is a term which may refer to two different forces which are related to rotation. ... The centripetal force is the external force required to make a body follow a circular path at constant speed. ... Newtons First and Second laws, in Latin, from the original 1687 edition of the Principia Mathematica. ...

In order for an object inside the rotating spacecraft to feel the pull of artificial gravity, the object must be in motion relative to the center of rotation of the spacecraft. In the absence of air friction, an object that is not moving would remain in place (even when not at the center of motion) and would not "fall" toward the hull. This illustrates the fact that artificial gravity is a result of the object's circular motion and its reaction against the similarly moving spacecraft hull; artificial gravity is not an attraction between the object and the hull.

Artificial gravity by rotation has the following side effects:

• The Coriolis effect produced by rotation could cause dizziness, nausea and disorientation. Experiments have shown that slower rates of rotation reduce the Coriolis forces and its effects. It is generally believed that at 2 rpm or less no adverse effects from the Coriolis forces will occur, at higher rates some people can become accustomed to it and some do not, but at rates above 7rpm few if any can become accustomed. It is not yet known if very long exposures to high levels of Coriolis forces can increase the likelihood of becoming accustomed. The nausea-inducing effects of Coriolis forces can also be mitigated by restraining movement of the head. Head restraints are perhaps practical for exercising in artificial gravity (an artificial gravity gym), but not for much else.
• Gravity gradients: Artificial gravity levels vary proportionately with the distance from the center of rotation. With a small radius of rotation the amount of gravity felt at one's head would be significantly different from the amount felt at one's feet. This could make movement and changing body position awkward. Again, slower rotations or larger rotational radii should not lead to such a problem.
• Angular movement: As noted high angular velocities produce high levels of Coriolis forces, angular momentum would require a propulsion system of some kind to spin up (or spin down). Also if parts of the spaceship are intentionally not spinning, friction and similar torques will cause the rates of spin to converge (as well as causing the otherwise-stationary parts to spin), requiring motors and power to be used to compensate for the losses due to friction. Angular inertia can also complicate spacecraft propulsion and attitude control.

Calculations

or Where: g = Decimal fraction of Earth gravity R = Radius from center of rotation in meters π = 3.14159 rpm = revolutions per minute In the inertial frame of reference (upper part of the picture), the black object moves in a straight line. ... // Pre-syncope is a sensation of feeling faint. ... For other uses, see Nausea (disambiguation). ... For other uses, see Revolutions per minute (disambiguation). ... Modern indoor gymnasium with pull-down basketball hoops. ... This gyroscope remains upright while spinning due to its angular momentum. ... For other uses, see Friction (disambiguation). ... Torque applied via an adjustable end wrench Relationship between force, torque, and momentum vectors in a rotating system In physics, torque (or often called a moment) can informally be thought of as rotational force or angular force which causes a change in rotational motion. ... Moment of inertia quantifies the resistance of a physical object to angular acceleration. ... When a circles diameter is 1, its circumference is Ï€. Pi or Ï€ is the ratio of a circles circumference to its diameter in Euclidean geometry, approximately 3. ...

The engineering challenges of creating a rotating spacecraft are comparatively modest to any other proposed approach. Theoretical spacecraft designs using artificial gravity have a great number of variants with intrinsic problems and advantages. To reduce Coriolis forces to livable levels a rate of spin of 2 rpm or less would be needed. To produce 1g the radius of rotation would have to be 224 m (735 ft) or greater, which would make for a very large spaceship. To reduce mass, the support along the diameter could consist of nothing but a cable connecting two sections of a spaceship, possibly a habitat module and a counterweight consisting of every other part of the spacecraft. Eugene F. Lally of the Jet Propulsion Laboratory proposed this concept in the early 1960's in a paper titled, "To Spin or Not to Spin". It is not yet known if exposure to high gravity for short periods of time is as beneficial to health as continuous exposure to normal gravity. It is also not known how effective low levels of gravity would be to countering the health effects of weightlessness. Artificial gravity at 0.1g would require a radius of only 22 m (74 ft). Likewise at a radius of 10 m about 10 rpm would be required to produce earth gravity (at the hips; gravity would be 11% higher at the feet), or 14 rpm to produce 2g. If brief exposure to high gravity can negate the health effects of weightlessness then a small centrifuge could be used as an exercise area. The term g force or gee force refers to the symbol g, the force of acceleration due to gravity at the earths surface. ... This article is about the unit of length. ... A foot (plural: feet or foot;[1] symbol or abbreviation: ft or, sometimes, ′ – a prime) is a unit of length, in a number of different systems, including English units, Imperial units, and United States customary units. ...

The Gemini 11 mission attempted to produce artificial gravity by rotating the capsule around the Agena Target Vehicle which it was attached to by a 36 meter tether. The resultant force was too small to be felt by either astronaut, but objects were observed moving towards the 'floor' of the capsule. Gemini 11 (officially Gemini XI) was a 1966 manned spaceflight in NASAs Gemini program. ... An Atlas launch vehicle launches GATV-5006 into orbit for the Gemini 11 mission. ...

The Mars Gravity Biosatellite will study the effect of artificial gravity on mammals. An artificial gravity field of 0.38g (Mars gravity) will be produced by rotation (34 rpm, radius of ca. 30 cm). Fifteen mice will orbit Earth for five weeks and land alive. The Mars Gravity Biosatellite project is a joint venture of MIT and the Georgia Institute of Technology to develop a free-flying spacecraft for un-crewed research flights. ... Adjectives: Martian Atmosphere Surface pressure: 0. ...

Acceleration

The spacecraft could, in theory, continuously accelerate in a straight line, forcing objects inside the spacecraft in the opposite direction of the direction of acceleration. Most rockets already accelerate at a rate to produce several times earth's gravity, but can only maintain these for several minutes because of a limited supply of fuel. Theoretically a propulsion system with a very high specific impulse and high thrust-to-weight ratio could accelerate, producing useful levels of artificial gravity for long periods of time. In addition, constant acceleration would provide relatively short flight times around the solar system. A spaceship accelerating (then decelerating) at 1g would reach Mars in 2-5 days, depending on the relative distance. In a number of science fiction plots, acceleration is used to produce artificial gravity for interstellar spacecraft, propelled by as yet theoretical or hypothetical means. Specific impulse (usually abbreviated Isp) is a way to describe the efficiency of rocket and jet engines. ... Thrust-to-weight ratio (where weight means weight at the Earths surface) is a dimensionless parameter characteristic of rocket and jet engines, and of vehicles propelled by such engines (typically space launch vehicles and jet aircraft). ... Adjectives: Martian Atmosphere Surface pressure: 0. ... Science fiction is a form of speculative fiction principally dealing with the impact of imagined science and technology, or both, upon society and persons as individuals. ... The interstellar medium (or ISM) is a term used in astronomy to describe the rarefied gas and dust that exists between the stars (or their immediate circumstellar environment) within a galaxy. ... In mathematics, theory is used informally to refer to a body of knowledge about mathematics. ... A hypothesis (= assumption in ancient Greek) is a proposed explanation for a phenomenon. ...

In practice, this idea is far beyond the current state of the art.

Mass

Another way artificial gravity may be achieved is by installing an ultra-high density core into a spacecraft so that it would generate its own gravitational field and pull everything inside towards it. Technically this is not artificial gravity—it is gravity. An extremely large amount of mass would be needed to produce even a tiny amount of noticeable gravity. A large asteroid could exert several thousandths of a G and by attaching a propulsion system of some kind would qualify as a space ship, though gravity at such a low level might not have any practical value. In addition, the mass would obviously need to move with the spacecraft; if the spacecraft is to be accelerated significantly, this would greatly increase fuel consumption. It is generally acknowledged that this method of producing gravity is unlikely to be of any benefit or utility to manned spaceflight inside the solar system.

Tidal forces

In a planetary orbit a small artificial gravity can be obtained from the tidal force; by two spacecraft above each other (or one spacecraft and another mass), connected by a tether. See also tidal stabilization. Comet Shoemaker-Levy 9 after breaking up under the influence of Jupiters tidal forces. ... Artists conception of satellite with a tether Tether propulsion uses long, strong strings (known as Tethers) to change the orbits of spacecraft. ...

Magnetism

A similar effect to gravity has been created through diamagnetism. It requires magnets with extremely powerful magnetic fields. At present such devices have been made that were able to levitate at most a small frog, and thus producing a 1 g field to cancel the Earth's; yet it required a magnet and system that weighs thousands of kilograms and is kept superconductive with expensive cryonics and required 6 MW of power^[1]. Levitating pyrolytic carbon Diamagnetism is a form of magnetism that is only exhibited by a substance in the presence of an externally applied magnetic field. ... “Kg” redirects here. ... Superconductivity is a phenomenon occurring in certain materials at low temperatures, characterised by the complete absence of electrical resistance and the damping of the interior magnetic field (the Meissner effect. ... Not to be confused with cryogenics. ...

Such extremely strong magnetic fields are far above the permitted levels^[specify], and safety for use with humans is at best unclear. In addition, it would involve avoiding any non-diamagnetic materials near the strong magnetic field required for diamagnetism to be evident. Some other disadvantages of using magnetism on a spaceship are found here: http://www.madsci.org/posts/archives/2005-04/1112370655.Ph.r.html

However, facilities using diamagnetism may prove excellent laboratories for simulating low gravity conditions here on Earth. Note that the frog was levitated against Earth's gravity, simulating a condition similar to microgravity. Lower forces may also be generated to simulate a condition similar to Lunar or Martian gravity with small model organisms. Astronauts on the International Space Station display an example of weightlessness Weightlessness is the experience (by people and objects) during freefall, of having no weight. ... A model organism is one that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the model organism will provide insight into the workings of other organisms. ...

Gravity generator/gravitomagnetism

In science fiction, artificial gravity (or cancellation of gravity) is sometimes present in spacecraft that are neither rotating nor accelerating. At present there is no confirmed technique that can produce gravity other than sheer mass. There have been many claims over the years of such a device. Eugene Podkletnov, a Russian engineer, has claimed since the early 1990s to have made such a device consisting of a spinning superconductor producing a powerful Gravitomagnetic field, but there has been no verification or even negative results from third parties. In 2006 a research group funded by ESA claimed to have created a similar device that demonstrated positive results for the production of gravitomagnetism, although it produced only 100 millionths of a g.[1] Science fiction is a form of speculative fiction principally dealing with the impact of imagined science and technology, or both, upon society and persons as individuals. ... This article does not cite any references or sources. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... g (also gee, g-force or g-load) is a non-SI unit of acceleration defined as exactly 9. ...

Fiction

Rotational gravity

In the movie 2001: A Space Odyssey a rotating centrifuge in the Discovery spacecraft provides artificial gravity. The people would be walking inside the circle; their feet toward the exterior and their head toward the center, the floor and ceiling would curve upwards. A rotating circular set was used in at least one instance to make this effect, with the actors always at the bottom, as they walked the set would be turned to keep the actors at the bottom and prevent them from falling over as they walked up the curved floor. The movie also features a rotating space station.

Larry Niven's novel Ringworld featured a gigantic habitat encircling a star, which created artificial gravity through rotation. Niven also makes a reference to the Coriolis Effect, when the protagonists see what looks like a giant eye above the horizon. When they get closer, they realise that it is in fact a hurricane, but rotating about an axis parallel to the ground rather than perpendicular to it. Large hurricanes on Earth rotate the way they do due to the Coriolis Effect. A number of early Known Space and Man-Kzin Wars stories also make use of rotational gravity, prior to the adoption of "gravity polarizer" technology which generates artificial gravity fields. This article does not cite any references or sources. ... Ringworld is a Hugo and Nebula award-winning 1970 science fiction novel by Larry Niven, set in his Known Space universe. ... In the inertial frame of reference (upper part of the picture), the black object moves in a straight line. ... Known Space is the fictional setting of several science fiction novels and short stories written by author Larry Niven. ... The Kzin (plural Kzinti) are a fictional, very warlike and bloodthirsty race of felinoid aliens in Larry Nivens Known Space series. ...

In the Gundam universe, gigantic space habitats similar to O'Neill cylinders, called Colonies, are an important aspect to the plot. They spin to generate artificial gravity. This article is about the anime series. ... A pair of ONeill cylinders Interior of a Torus (doughnut-shaped) station A space habitat, also called space colony or orbital colony, is a space station intended as a permanent settlement rather than as a simple waystation or other specialized facility. ... A pair of ONeill cylinders The ONeill cylinder is a space habitat design proposed by physicist Gerard K. ONeill in his book, The High Frontier. ...

In the anime Cowboy Bebop, the Bebop possesses a ringed area that generates artificial gravity, and is often seen being used (with the rest of the ship not rotating). “Animé” redirects here. ... Original run April 3, 1998 – April 23, 1999 Episodes 26 Movie: Knockin on Heavens Door (天国の扉) Director Shinichiro Watanabe Writer Keiko Nobumoto Studio Sunrise BONES Bandai Visual[2] Released September 1, 2001 Runtime 115 min. ...

The book Rendezvous with Rama and the sequels featured an alien construct similar to an O'Neill habitat which was able to generate approximately 1g on the intentionally habitable ground section. The plot employed significant use of the difference in strength of artificial gravity as an object approaches the center of the rotating cylinder. Rendezvous with Rama is a novel by Arthur C. Clarke first published in 1972. ... A pair of ONeill cylinders The ONeill cylinder is a space habitat design proposed by Gerard K. ONeill in his book The High Frontier. ...

In the television series Babylon 5, the Earth Alliance made extensive use of rotational gravity in its space stations and some larger military vessels, as well as civilian cruise ships. It has been suggested that the cruise ships would alter their rate of spin gradually en route to match the destination, helping to acclimate the passengers to the new gravity they would find upon arrival. Babylon 5 is an epic American science fiction television series created, produced, and largely written by J. Michael Straczynski. ... The Earth Alliance is the name of at least two fictional governments or alliances in modern science-fiction. ... The International Space Station in 2007 A space station is an artificial structure designed for humans to live in outer space. ...

In the stories based on Sid Meier’s Alpha Centauri, the Unity provided artificial gravity by spinning, though the game made allusions to less conventional technologies developed later on. “SMAC” redirects here. ...

In John Varley’s Gaian Trilogy (Titan, Wizard, and Demon), the titular world Gaia, being a torus with a diameter of 1300 kilometers, spins at a rate of one revolution per sixty-one minutes, producing an apparent gravity of one-quarter gee. John Varley John Herbert Varley (born August 9, 1947 in Austin, Texas) is a Hugo Award, Nebula Award, Seiun Award and Prometheus Award Winning science fiction author. ... The Gaian Trilogy includes Titan_(John_Varley) Wizard Demon written by SF author John Varley in the late 70s / early 80s. ... In geometry, a torus (pl. ... A kilometer (Commonwealth spelling: kilometre), symbol: km is a unit of length in the metric system equal to 1,000 metres (from the Greek words χίλια (khilia) = thousand and μέτρο (metro) = count/measure). ...

In the game Halo: Combat Evolved (by Bungie), the main location of the story is an artificial ringworld that creates artificial gravity by computer-controlled rotational spin. "Halo" (or "Installation 04") is approximately 10,000 km in diameter and is eventually destroyed by the same forces keeping it in operation. A nuclear explosion weakens part of the ringworld, and centrifugal forces tear the ring apart. Halo: Combat Evolved, or simply Halo, is a video game in the first-person shooter (FPS) genre, created by the Microsoft-owned Bungie Studios. ...

Field generators

In many science fiction stories, there are artificial gravity generators that create a gravitational field based on a mass that does not exist. It helps the story by creating a more Earth-like spaceship, and in the case of a movie or television program, it helps the production because it is a lot cheaper than the special effects needed to simulate weightlessness. Science-fiction critic Justin B. Rye has proposed the term 'gravity carpet' to describe this technology, but the term has not come into widespread use. Science fiction is a form of speculative fiction principally dealing with the impact of imagined science and technology, or both, upon society and persons as individuals. ... The Space Shuttle Discovery as seen from the International Space Station. ... Astronauts on the International Space Station display an example of weightlessness. ...

In the Star Trek universe, artificial gravity is achieved by the use of "gravity plating" embedded in a starship's deck. This article is about the entire Star Trek franchise. ...

• In the Star Trek: Enterprise episode "In a Mirror, Darkly", the gravity plating of the USS Defiant is used to fend off a Gorn attack, by greatly increasing the ship's gravity in one section. The Gorn attacker was forced down to the floor and immobilized, where Jonathan Archer easily killed him.
• Benjamin Sisko once built a replica of an ancient Bajoran solar-sailer spacecraft. As these craft were not normally equipped with artificial gravity, Sisko added grav plating to make it easier for him and Jake to pilot the vessel. (DS9 episode "Explorers")

In Gene Roddenberry's Andromeda, set thousands of years in the future, gravity field generators not only provide gravity for the people inside the ship, but also reduce inertial mass of ships such as the Andromeda Ascendant to just under a kilogram. This greatly increases the efficiency of their Magneto-Plasma Dynamic Drive, allowing them to go from a stop to percentages of light speed very quickly. The starship Enterprise (NX-01) Star Trek: Enterprise is a science fiction television series set in the Star Trek universe. ... In a Mirror, Darkly is a two-part episode of Star Trek: Enterprise. ... In the Star Trek universe, the USS Defiant (NCC-1764) is one of the original twelve Federation Constitution-class starships. ... The Gorn which Captain Kirk fought in Arena A Gorn from the Enterprise episode In a Mirror, Darkly Part II In the fictional Star Trek universe, the Gorn are intelligent reptilian humanoids from the Gorn Hegemony. ... Jonathan Archer is a fictional character and the main character of the television series Star Trek: Enterprise. ... Benjamin Lafayette Sisko, played by Avery Brooks, is the main character of the television series Star Trek: Deep Space Nine. ... Bajorans, a race of humanoids in the fictional Star Trek universe, were introduced in the Next Generation series and played an integral part in the Deep Space Nine series. ... Jake Sisko is a character in the fictional Star Trek universe, played by Cirroc Lofton. ... Space station Star Trek: Deep Space Nine (ST:DS9 or STDS9 or DS9 for short) is a science fiction television series produced by Paramount and set in the Star Trek universe. ... Explorers is the 22nd episode in the third season of Star Trek: Deep Space Nine. ... Eugene Wesley Roddenberry (August 19, 1921 – October 24, 1991) was an American scriptwriter and producer. ... Gene Roddenberrys Andromeda is an American science fiction television series, based on unused material by Gene Roddenberry developed by Robert Hewitt Wolfe, and produced posthumously by his widow, Majel Roddenberry. ... Inertial mass is a measure of the resistance of an entity to a change in its velocity relative to an inertial frame. ... The Andromeda Ascendant is a fictional starship in the television series Gene Roddenberrys Andromeda. ...

In the cartoon Dragonball Z the characters train in numerous extra-gravity environments. For example, Goku trains in a gravity chamber on his 6-day trip to Namek. He trains from 20-100X Earth's gravity. Vegeta later trains at 300X and 450X Earth's gravity.

References

1. ^ 20 tesla Bitter solenoid

External links

• List of peer review papers on artificial gravity
• Mars gravity experiment homepage
• Revolving artificial gravity calculator
• Overview of artificial gravity in Sci-Fi and Space Science
• Description of artificial gravity
• NASA's Java simulation of artificial gravity