NationMaster - Encyclopedia: Interstellar travel

Interstellar space travel is unmanned or manned travel between stars. The concept of interstellar travel in starships is a staple in science fiction. Interstellar travel is tremendously more difficult than interplanetary travel. Intergalactic travel, the travel between different galaxies, is even more difficult. NASA conceptual art by Les Bossinas for the Breakthrough Propulsion Physics project - File links The following pages link to this file: Spacecraft propulsion User:Patrick/w Categories: NASA images ... NASA conceptual art by Les Bossinas for the Breakthrough Propulsion Physics project - File links The following pages link to this file: Spacecraft propulsion User:Patrick/w Categories: NASA images ... This article is about the Alcubierre metric. ... Miguel Alcubierre (Born 1964) is a Mexican theoretical physicist. ... This article does not cite any references or sources. ... This article is about the astronomical object. ... One of the fictional ships called the Starship Enterprise from Star Trek, one of the most famous fictional starships. ... 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. ... By definition, interplanetary travel is travel between bodies in a given star system; especially the solar system. ... Intergalactic travel is travel between galaxies, and is considered much more technologically demanding than even interstellar travel. ...

Many scientific papers have been published about related concepts. Given sufficient travel time and engineering work, both unmanned and generational interstellar travel seem possible, though representing a very considerable technological and economic challenge unlikely to be met for some time, particularly for crewed probes. NASA has been engaging in research into these topics for several years, and has accumulated a number of theoretical approaches. For other uses, see NASA (disambiguation). ...

The difficulties of interstellar travel

The main difficulty of interstellar travel is the vast distances that have to be covered and therefore the time it takes with most realistic propulsion methods - from decades to millennia. Hence an interstellar ship would be much more severely exposed to the hazards found in interplanetary travel, including hard vacuum, radiation, weightlessness, and micrometeoroids. The long travel times make it difficult to design manned missions, and make economic justification of any interstellar mission nearly impossible, since benefits that do not become available for decades or longer have a present value close to zero. For other senses of this word, see decade (disambiguation). ... These pages contain the trends of millennia and centuries. ... By definition, interplanetary travel is travel between bodies in a given star system; especially the solar system. ... Look up Vacuum in Wiktionary, the free dictionary. ... Radiation hazard symbol. ... Zero gravity redirects here. ... A Micrometeoroid (also micrometeorite, micrometeor) is a tiny meteoroid; a small particle of rock from space, usually weighing less than a gram, that poses a threat to space exploration. ... The present value of a single or multiple future payments (known as cash flows) is the nominal amounts of money to change hands at some future date, discounted to account for the time value of money, and other factors such as investment risk. ...

It has been argued that an interstellar mission which cannot be completed within 50 years should not be started at all. Instead, the money should be invested in designing a better propulsion system. This is because a slow spacecraft would probably be passed by another mission sent later with more advanced propulsion.^[1]

Intergalactic travel involves distances about a million-fold greater than interstellar distances, making it radically more difficult than even interstellar travel. Intergalactic travel is travel between galaxies, and is considered much more technologically demanding than even interstellar travel. ...

Interstellar distances

Astronomical distances are sometimes measured in the length of time it would take a beam of light to travel between two points (see lightyear). Light in a vacuum travels 299,792,458 meters per second or 186,282.37 miles per second. For other uses, see Light (disambiguation). ... Light year, a measure of distant Lightyear (band), a ska-punk band from the UK Buzz Lightyear, a character in the animated film Toy Story. ...

The distance from Earth to the Moon is 1.3 light-seconds. With current spacecraft propulsion technologies, a trip to the moon will typically take about three days. The distance from Earth to other planets in the solar system ranges from three light-minutes to about four light-hours. Depending on the planet and its alignment to Earth, for a typical unmanned spacecraft these trips will take from a few months to a little over a decade. This article is about Earth as a planet. ... A light second is a unit of length. ...

The nearest known star to the Sun is Proxima Centauri, which is 4.23 light-years away. The fastest outward-bound spacecraft yet sent, Voyager 1, has covered 1/600th of a light-year in 30 years and is currently moving at 1/18000 the speed of light. At this rate, a journey to Proxima Centauri would take 72,000 years. Of course, this mission was not specifically intended to travel fast to the stars, and current technology could do much better. The travel time could be reduced to a few millennia using lightsails, or to a century or less using nuclear pulse propulsion (Orion). Sol redirects here. ... Proxima Centauri (Latin proximus, -a, -um: meaning next to or nearest to)[4] is a red dwarf star that is likely a part of the Alpha Centauri star system and is the nearest star to the Sun at a distance of 4. ... For the album by The Verve, see Voyager 1 (album). ... An artists conception of the Orion basic spacecraft, powered by nuclear pulse propulsion. ...

No current technology can propel a craft fast enough to reach other stars in under 50 years' time. Current theories of physics indicate that it is impossible to travel faster than light, and suggest that if it were possible, it might also be possible to build a time machine using similar methods. Faster than the speed of light redirects here. ... Time travel is a concept that has long fascinated humanity—whether it is Merlin experiencing time backwards, or religious traditions like Mohammeds trip to Jerusalem and ascent to heaven, returning before a glass knocked over had spilt its contents. ...

However, special relativity offers the possibility of shortening the apparent travel time: if a starship with sufficiently advanced engines could reach velocities approaching the speed of light, relativistic time dilation would make the voyage seem much shorter for the traveller. However, it would still take many years of elapsed time as viewed by the people remaining on Earth, and upon returning to Earth, the travellers would find that far more time had elapsed on Earth than had for them. (This effect is referred to as the twin paradox.) For a generally accessible and less technical introduction to the topic, see Introduction to special relativity. ... Time dilation is the phenomenon whereby an observer finds that anothers clock which is physically identical to their own is ticking at a slower rate as measured by their own clock. ... In physics, the twin paradox refers to a thought experiment in Special Relativity, in which a person who makes a journey into space in a high-speed rocket will return home to find they have aged less than an identical twin who stayed on Earth. ...

General relativity offers the theoretical possibility that faster than light travel may be possible without violating fundamental laws of physics, for example, via wormholes, although it is still debated whether this is possible in the real world. Proposed mechanisms for faster than light travel within the theory of General Relativity require the existence of exotic matter. For a generally accessible and less technical introduction to the topic, see Introduction to general relativity. ... A wormhole, also known as an Einstein-Rosen bridge, is a hypothetical topological feature of spacetime that is essentially a shortcut from one point in the universe to another point in the universe, allowing travel between them that is faster than it would take light to make the journey through... Faster than the speed of light redirects here. ... Exotic matter is a hypothetical concept of particle physics. ...

Manned missions

The mass of any craft capable of carrying humans would inevitably be several orders of magnitude greater than that necessary for an unmanned interstellar probe. For instance, the first space probe, Luna 1, had a payload of 361 kg; while the first spacecraft to carry a living passenger (Laika the dog), Sputnik 2, had a payload over 20 times that at 7,314 kg. This in fact severely underestimates the difference in the case of interstellar missions, given the vastly greater travel times involved and the resulting necessity of a closed-cycle life support system. This article or section does not cite its references or sources. ... Luna 1 is the first spacecraft to reach the vicinity of the Moon and the first of the Luna programme of Soviet automatic interplanetary stations successfully launched in the direction of the Moon. ... For other uses, see Laika (disambiguation). ... Sputnik 2 (Russian: , Satellite 2) was the second spacecraft launched into Earth orbit, on November 3, 1957, and the first to carry a living animal - a dog named Laika. ... Controlled (or Closed) Ecological Life Support Systems or (acronym CELSS) are a type of scientific endeavor to create a self-supporting life support system for space stations and colonies typically through controlled ecological environments, such as the BioHome, BIOS-3, Biosphere 2 and Mars Base Zero. ... In human spaceflight, the life support system is a group of devices that allow a human being to survive in outer space. ...

Proposed methods of interstellar travel

If a spaceship could average 10 percent of light speed, this would be enough to reach Proxima Centauri in forty years. Several propulsion systems are able to achieve this, but none of them are reasonably cheap. Proxima Centauri (Latin proximus, -a, -um: meaning next to or nearest to)[4] is a red dwarf star that is likely a part of the Alpha Centauri star system and is the nearest star to the Sun at a distance of 4. ...

Nuclear pulse propulsion

Since the 1960s it has been technically possible to build spaceships with nuclear pulse propulsion engines, i.e. ships driven by a series of nuclear explosions. This propulsion system contains the prospect of very high specific impulse (space travel's equivalent of fuel economy) and high speed, and therefore of reaching the nearest star in decades rather than centuries; construction and operational costs per unit of Payload (air and space craft) were expected to be similar to those of ships using chemical rockets.^[2] An artists conception of the Orion basic spacecraft, powered by nuclear pulse propulsion. ... Specific impulse (usually abbreviated Isp) is a way to describe the efficiency of rocket and jet engines. ... In military aircraft or space exploration, the payload is the carrying capacity of an aircraft or space ship, including as cargo, munitions, scientific instruments or experiments, or external fuel, although internal fuel is usually not included. ...

Proposed interstellar spacecraft using nuclear pulse propulsion include Project Orion and Project Longshot. Using miniature nuclear bombs as fuel, Orion would be able to reach a velocity of 3% of the speed of light. It is one of very few known interstellar spacecraft proposals that could be constructed entirely with today's technology. Project Orion may mean: Project Orion is the name of one of several projects to build a laser broom for the International Space Station. ... Project Longshot is a design for an interstellar spaceship, an unmanned probe intended to fly to Alpha Centauri powered by nuclear pulse propulsion. ...

Fusion rockets

Fusion rocket starships, using foreseeable fusion reactors, should be able to reach speeds of approximately 10 percent of that of light. These would "burn" deuterium. One proposal using a fusion rocket is Project Daedalus. This article does not cite any references or sources. ... An artists conception of the British Interplanetary Society design for Project Daedalus Project Daedalus was a study conducted between 1973 and 1978 by the British Interplanetary Society to design a plausible interstellar unmanned spacecraft. ...

The problem with all traditional rocket propulsion methods is that the spacecraft would need to carry its fuel with it, thus making it quite heavy. The following three methods attempt to solve this problem.

Interstellar Ramjets

In 1960 Robert W. Bussard proposed the Bussard ramjet, a fusion rocket in which a huge scoop would collect the diffuse hydrogen in interstellar space, "burn" it on the fly using a proton-proton fusion reaction, and expel it out of the back. Though later calculations with more accurate estimates suggest that the thrust generated would be less than the drag caused by any conceivable scoop design, the idea is attractive because, as the fuel would be collected en route, the craft could theoretically accelerate to near the speed of light. Artists conception of a Bussard ramjet. ... The proton-proton chain reaction is one of two fusion reactions by which stars convert hydrogen to helium, the other being the CNO cycle. ...

Antimatter rockets

An Antimatter rocket would have a far higher energy density and specific impulse than any other proposed class of rocket. If energy resources and efficient production methods are found to make antimatter in the quantities required, theoretically it would be possible to reach speeds near that of light, where time dilation would shorten perceived trip times for the travelers considerably. This article does not cite any references or sources. ... For other senses of this term, see antimatter (disambiguation). ... Time dilation is the phenomenon whereby an observer finds that anothers clock which is physically identical to their own is ticking at a slower rate as measured by their own clock. ...

Beamed Propulsion

A light sail or magnetic sail powered by a massive laser or particle accelerator in the home star system could potentially reach even greater speeds, because it would not need reaction mass and therefore would not need to accelerate that as well as the payload. In theory a lightsail driven by a laser or other beam from Earth can be used to decelerate a spacecraft approaching a distant star or planet, by detaching part of the sail and using it to focus the beam on the forward-facing surface of the rest of the sail.^[3] A magnetic sail could also decelerate to its destination without fuel, by interacting with the plasma found in the solar wind of the destination star and the interstellar medium. A artists depiction of a Cosmos 1 type spaceship in orbit Solar sails (also called light sails or photon sails, especially when they use light sources other than the Sun) are a proposed form of spacecraft propulsion using large membrane mirrors. ... A magnetic sail or magsail is a proposed method of spacecraft propulsion. ... For other uses, see Laser (disambiguation). ... Working mass is a mass against which a system operates in order to produce acceleration. ... In military aircraft or space exploration, the payload is the carrying capacity of an aircraft or space ship, including as cargo, munitions, scientific instruments or experiments, or external fuel, although internal fuel is usually not included. ...

Beamed propulsion seems to be the best interstellar travel technique presently available, since it uses known physics and known technology that is being developed for other purposes.^[4] Beam-powered propulsion is a class of spacecraft propulsion mechanisms that use energy beamed to the spacecraft from a remote power plant. ...

Further speculative methods

Light speed travel

Interstellar travel via transmission

If physical entities could be transmitted as information and reconstructed at a destination, travel precisely at the speed of light would be possible. Note that, under General Relativity, information cannot travel faster than light. The speed increase when compared to near-light-speed travel would therefore be minimal for outside observers, but for the travelers the journey would become instantaneous. Teleport redirects here. ... For a generally accessible and less technical introduction to the topic, see Introduction to general relativity. ...

Encoding, sending and then reconstructing an atom by atom description of (say) a human body is a daunting prospect, but it may be sufficient to send software that in all practical purposes duplicates the neural function of a person. Presumably, the receiver/reconstructor for such transmissions would have to be sent to the destination by more conventional means. Tachyons could not be used for communication. Computer software (or simply software) refers to one or more computer programs and data held in the storage of a computer for some purpose. ... A tachyon (from the Greek (takhÃºs), meaning swift, fast) is any hypothetical particle that travels at superluminal velocity. ...

Faster than light travel

Scientists and authors have postulated a number of ways by which it might be possible to surpass the speed of light. Even the most serious-minded of these are speculative. Faster-than-light (also superluminal or FTL) communications and travel are staples of the science fiction genre. ...

Warped Spacetime

According to Einstein's equation of General Relativity, spacetime is curved: In physics, the Einstein field equation or Einstein equation is a differential equation in Einsteins theory of general relativity. ... For a generally accessible and less technical introduction to the topic, see Introduction to general relativity. ... For other uses of this term, see Spacetime (disambiguation). ...

General relativity may permit the travel of an object faster than light in curved spacetime.^[5] One could imagine exploiting the curvature to take a "shortcut" from one point to another. This is one form of the Warp Drive concept. For other uses, see Warp drive (disambiguation). ...

In physics, the Alcubierre drive is based on an argument that the curvature could take the form of a wave in which a spaceship might be carried in a "bubble". Space would be collapsing at one end of the bubble and expanding at the other end. The motion of the wave would carry a spaceship from one space point to another in less time than light would take through unwarped space. Nevertheless, the spaceship would not be moving faster than light within the bubble. This concept would require the spaceship to incorporate a region of exotic matter, or "negative mass". As a practical means of interstellar transportation, this idea has been criticized; see Alcubierre Drive. This article is about the Alcubierre metric. ... Exotic matter is a hypothetical concept of particle physics. ... This article is about the Alcubierre metric. ...

Wormholes

Wormholes are conjectural distortions in space-time that theorists postulate could connect two arbitrary points in the universe, across an Einstein-Rosen Bridge. It is not known whether or not wormholes are possible in practice. Although there are solutions to the Einstein equation of general relativity which allow for wormholes, all of the currently known solutions involve some assumption, for example the existence of negative mass, which may be unphysical.^[6] However, Cramer et al. argue that such wormholes might have been created in the early universe, stabilized by cosmic string.^[7] The general theory of wormholes is discussed by Visser in the book Lorentzian Wormholes^[8] A wormhole, also known as an Einstein-Rosen bridge, is a hypothetical topological feature of spacetime that is essentially a shortcut from one point in the universe to another point in the universe, allowing travel between them that is faster than it would take light to make the journey through... 2D analogy to a wormhole. ... Exotic matter is a hypothetical concept of particle physics. ... A cosmic string is a hypothetical 1-dimensional topological defect in the fabric of spacetime. ...

Methods for slow manned missions

Slow interstellar travel designs such as Project Longshot generally use near-future spacecraft propulsion technologies. As a result, voyages are extremely long, starting from about one hundred years and reaching to thousands of years. Crewed voyages might be one-way trips to set up colonies. The duration of such a journey would present a huge obstacle in itself. The following are the major proposed solutions to that obstacle: Project Longshot is a design for an interstellar spaceship, an unmanned probe intended to fly to Alpha Centauri powered by nuclear pulse propulsion. ... A remote camera captures a close-up view of a Space Shuttle Main Engine during a test firing at the John C. Stennis Space Center in Hancock County, Mississippi Spacecraft propulsion is any method used to change the velocity of spacecraft and artificial satellites. ... This article is about a type of political territory. ...

Generation ships

A generation ship is a type of interstellar ark in which the travellers live normally (not in suspended animation) and the crew who arrive at the destination are descendants of those who started the journey. A generation ship is a hypothetical starship that travels across great distances between stars at a speed much slower than that of light (see interstellar travel). ... To meet Wikipedias quality standards, this article or section may require cleanup. ... This article is about suspended animation in a medical context. ...

Generation ships are not currently feasible, both because of the enormous scale of such a ship and because such a sealed, self-sustaining habitat would be difficult to construct. Artificial closed ecosystems, including Biosphere 2, have been built in an attempt to work out the engineering difficulties in such a system, with mixed results. A coral reef near the Hawaiian islands is an example of a complex marine ecosystem. ... Biosphere 2 Biosphere 2 is a 3. ...

Generation ships would also have to solve major biological and social problems.^[9] Estimates of the minimum viable population vary - 180 is about the lowest, but such a small population would be vulnerable to genetic drift, which might reduce the gene pool below a safe level. A generation ship in fiction typically takes thousands of years to reach its destination, i.e. longer than most human civilizations have lasted. Hence there is a risk that the culture which arrives at the destination may be incapable of doing what is needed - in the worst case it may have fallen into barbarism. Also they may forget that they are on a generation ship. Stephen Baxter's story "Mayflower II" (in the collection Resplendent) explores both of these risks as does Robert A. Heinlein's two-part 1941 novel Orphans of the Sky. To meet Wikipedias quality standards, this article or section may require cleanup. ... In population genetics, genetic drift is the statistical effect that results from the influence that chance has on the success of alleles (variants of a gene). ... The gene pool of a species or a population is the complete set of unique alleles that would be found by inspecting the genetic material of every living member of that species or population. ... Barbarism may refer to: Barbarism (derived from barbarian), the condition to which a society or civilization may be reduced after a societal collapse, relative to an earlier period of cultural or technological advancement; the term may also be used pejoratively to describe another society or civilization which is deemed inferior... Stephen Baxter (born in Liverpool, 13 November 1957) is a British hard science fiction author. ... Resplendent will be released on 21 September 2006 in the UK (time unknown for the US). ... Robert Anson Heinlein (July 7, 1907 â€“ May 8, 1988) was one of the most popular, influential, and controversial authors of hard science fiction. ... 1964 hardback edition Orphans of the Sky is a 1951 science fiction novella by Robert A. Heinlein, consisting of two parts: Universe and Common Sense. ...

Suspended animation

Scientists and writers have postulated various techniques for suspended animation. These include human hibernation and cryonic preservation. While neither is currently practical, they offer the possibility of sleeper ships in which the passengers lie inert for the long years of the voyage. However, even assuming all relevant space-faring and suspended animation technologies could be developed, an automated means of guiding the ship to its destination with little or no human influence would be required. This article is about suspended animation in a medical context. ... This article refers to the process of hibernation in biology. ... Not to be confused with cryogenics. ... A sleeper ship is a hypothetical type of manned spaceship in which most or all of the crew spends the journey in some form of hibernation or suspended animation. ...

Extended human lifespan

A variant on this possibility is based on the development of substantial human life extension, such as the "Engineered Negligible Senescence" strategy of Dr. Aubrey de Grey. If a ship crew had lifespans of some thousands of years, they could traverse interstellar distances without the need to replace the crew in generations. The psychological effects of such an extended period of travel would potentially still pose a problem. Engineered negligible senescence refers to an engineered prevention or reversal of cellular aging (referred to as senescence in biology). ... Aubrey David Nicholas Jasper de Grey, Ph. ...

Frozen embryos

A robotic space mission carrying some number of frozen early stage human embryos is another theoretical possibility. This method of space colonization requires, among other things, the development of a method to replicate conditions in a uterus, the prior detection of a habitable terrestrial planet, and advances in the field of fully autonomous mobile robots. (See embryo space colonization.) In practical usage, a robot is a mechanical device which performs automated tasks, either according to direct human supervision, a pre-defined program or, a set of general guidelines, using artificial intelligence techniques. ... Categories: Biology stubs | Developmental biology ... Artists conception of a space habitat called the Stanford torus, by Don Davis Space colonization (also called space settlement, space humanization, space habitation, etc. ... This article is about female reproductive anatomy. ... The inner planets, Mercury, Venus, Earth, and Mars, their sizes to scale. ... The Shadow robot hand system holding a lightbulb. ... Embryo space colonization is an interstellar space colonization proposal that involves sending a robotic mission to a terrestrial planet (having a biosphere) that transports frozen early-stage embryos. ...

NASA research

The NASA Breakthrough Propulsion Physics Project identified two breakthroughs which are needed for interstellar travel to be possible ^[10]: For other uses, see NASA (disambiguation). ...

In other words, any engine short of the best conceivable engine won't work, and that engine cannot be powered by currently known energy sources. Analogies for 'breakthroughs' in technology are steam engines supplanting sailing ships, and jet aircraft replacing propeller aircraft.

Geoffery A. Landis, of NASA's Glenn Research Center, says that a laser-powered interstellar sail ship could possibly be launched within 50 years, utilizing new methods of space travel. "I think that ultimately we're going to do it, it's just a question of when and who," Landis said in an interview. Rockets are too slow to send humans on interstellar missions. Instead, he envisions interstellar craft with gigantic sails, propelled by laser light to about one tenth the speed of light. It would take such a ship about 43 years to reach Alpha Centauri, if it passed through the system. Slowing down to stop at Alpha Centauri could increase the trip to 100 years.^[9]

References

^ Yoji Kondo: Interstellar Travel and Multi-generation Spaceships, p. 31
^ General Dynamics Corp. (Jan 1964). Nuclear Pulse Vehicle Study Condensed Summary Report (General Dynamics Corp.). U.S. Department of Commerce National Technical Information Service.
^ Forward, R.L. (1984). "Roundtrip Interstellar Travel Using Laser-Pushed Lightsails". J Spacecraft 21 (2): 187-195.
^ Bob Forward: Ad Astra, in Journal of the British Interplanetary Society (Vol. 49, pp. 23-32, 1996)
^ Remote Sensing Tutorial Page A-10
^ (http://www.nasa.gov/centers/glenn/research/warp/ideachev.html#worm)
^ John G. Cramer, Robert L. Forward, Michael S. Morris, Matt Visser, Gregory Benford, and Geoffrey A. Landis, "Natural Wormholes as Gravitational Lenses," Phys. Rev. D51 (1995) 3117-3120
^ M. Visser (1995) Lorentzian Wormholes: from Einstein to Hawking, AIP Press, Woodbury NY, ISBN 1-56396-394-9
^ ^a ^b [1] Malik, Tariq, "Sex and Society Aboard the First Starships." Science Tuesday, Space.com March 19, 2002.
^ Warp Drive, When? Breakthrough Technologies

General Dynamics Corporation (NYSE: GD) is a defense conglomerate formed by mergers and divestitures, and as of 2006 it is the sixth largest defense contractor in the world[2]. The company has changed markedly in the post-Cold War era of defense consolidation. ...

Contents

The difficulties of interstellar travel

Interstellar distances

Manned missions

Proposed methods of interstellar travel

Nuclear pulse propulsion

Fusion rockets

Interstellar Ramjets

Antimatter rockets

Beamed Propulsion

Further speculative methods

Light speed travel

Interstellar travel via transmission

Faster than light travel

Warped Spacetime

Wormholes

Methods for slow manned missions

Generation ships

Suspended animation

Extended human lifespan

Frozen embryos

NASA research

References

See also

External links

Contents

The difficulties of interstellar travel var ACE_AR = {Site: '756743', Size: '300250'};

Interstellar distances

Manned missions

Proposed methods of interstellar travel

Nuclear pulse propulsion

Fusion rockets

Interstellar Ramjets

Antimatter rockets

Beamed Propulsion

Further speculative methods

Light speed travel

Interstellar travel via transmission

Faster than light travel

Warped Spacetime

Wormholes

Methods for slow manned missions

Generation ships

Suspended animation

Extended human lifespan

Frozen embryos

NASA research

References

See also

External links

The difficulties of interstellar travel