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Encyclopedia > Interplanetary travel

By definition, interplanetary travel is travel between bodies in a given star system; especially the solar system. Statue dedicated to the traveller. ... Major features of the Solar System (not to scale; from left to right): Pluto, Neptune, Uranus, Saturn, Jupiter, the asteroid belt, the Sun, Mercury, Venus, Earth and its Moon, and Mars. ...

Contents

Reasons for interplanetary travel

The costs and risks of interplanetary travel receive a lot of publicity - spectacular and sometimes tragic examples include: the Challenger and Columbia space shuttle disasters (though these were in fact planned as Earth-orbit missions); and malfunctions or complete failures of unmanned probes such as Mars 96, Deep Space 2 and Beagle 2 (the article List of planetary probes gives a fairly full list). Space Shuttle Challenger (NASA Orbiter Vehicle Designation: OV-099) was NASAs second Space Shuttle orbiter to be put into service. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... The Deep Space 2 mission, which launched in January 1999 as part of NASAs New Millennium Program, consisted of two highly advanced miniature probes to Mars. ... Beagle 2 as it would have looked on Mars Beagle 2 was an unsuccessful British landing spacecraft that formed part of the European Space Agencys 2003 Mars Express mission. ... It has been suggested that Timeline of Solar System exploration be merged into this article or section. ...


Many astronomers, geologists and biologists believe that exploration of the solar system provides knowledge that could not be gained by observations from Earth's surface or from orbit round Earth. But they disagree about whether manned missions make a useful scientific contribution - some think robotic probes are cheaper and safer, while others argue that either astronauts advised by Earth-based scientists, or spacefaring scientists advised by Earth-based astronauts, can respond more flexibly and intelligently to new or unexpected features of the region they are exploring. [1]


Those who pay for such missions (currently mainly taxpayers) are more likely to be interested in benefits for themselves or for the human race as a whole. So far the only benefits of this type have been "spin-off" technologies which were developed for space missions and then were found to be at least as useful in other activities (NASA publicizes spin-offs from its activities).


Other practical motivations for interplanetary travel are more speculative, because our current technologies are not yet advanced enough to support test projects. But science fiction writers have a fairly good track record in predicting future technologies - for example geosynchronous communications satellites (Arthur C. Clarke) and many aspects of computer technology (Mack Reynolds). 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. ... It has been suggested that this article or section be merged with geostationary orbit. ... Sir Arthur Charles Clarke, CBE (born 16 December 1917) is a British science-fiction author and inventor, most famous for his novel 2001: A Space Odyssey, and for collaborating with director Stanley Kubrick on the film of the same name. ... Reynolds Mission to Horatius (1968), the first original novel based on the television show Star Trek Mack Reynolds (Dallas McCord Reynolds) (November 11, 1917 - January 30, 1983) was an American science fiction writer. ...


Many science fiction stories (notably Ben Bova's Grand Tour stories) feature detailed descriptions of how people could extract minerals from asteroids and energy from sources including orbital solar panels (unhampered by clouds) and the very strong magnetic field of Jupiter. Some point out that such techniques may be the only way to provide rising standards of living without being stopped by pollution or by depletion of Earth's resources (for example peak oil). Benjamin William Bova (born November 8, 1932) is an American science fiction author and editor. ... The Grand Tour is a series of novels written by science fiction author Ben Bova. ... 253 Mathilde, a C-type asteroid. ... A laundromat in California with flat-plate solar water heating collectors on its roof. ... Magnetic field lines shown by iron filings In physics, a magnetic field is a solenoidal vector field in the space surrounding moving electric charges and magnetic dipoles, such as those in electric currents and magnets. ... Adjectives: Jovian Atmosphere Surface pressure: 20–200 kPa[4] (cloud layer) Composition: ~86% Molecular hydrogen ~13% Helium 0. ... hi In the context of models of the depletion of resources, notably Hubbert peak theory, peak oil is the date when the peak of the worlds petroleum (crude oil) production rate is reached. ...


Finally, colonizing other parts of the solar system would prevent the whole human species from being exterminated by an asteroid impact like the one which may have exterminated the dinosaurs. Although various Spaceguard projects monitor the solar system for objects that might come dangerously close to Earth, current asteroid deflection strategies are crude and untested. To make the task more difficult, carbonaceous chondrites are rather sooty and therefore very hard to detect. Although carbonaceous chondrites are thought to be rare, some are very large and the suspected "dinosaur-killer" appears to have been a carbonaceous chondrite. Near-Earth asteroids (NEAs) are asteroids whose orbits are close to Earths orbit. ... Badlands near Drumheller, Alberta where erosion has exposed the KT boundary. ... The term Spaceguard loosely refers to a number of efforts to discover and study near-Earth objects (NEO). ... Artists impression of a major impact event. ... Some carbonaceous chondrites. ...


Some scientists, including members of the Space Studies Institute, argue that the vast majority of mankind eventually will live in space and will benefit from doing this.[2] Cover of procedings for 7th Space Manufacturing conference. ...


Current achievements in interplanetary travel

NASA's Apollo program landed twelve people on the Moon and returned them to Earth: Apollo 11-17, except 13, i.e. six missions, each with three astronauts of which two landed on the Moon. Robotic space probes have been sent to fly past all of the planets of the Solar system. The most distant probe spacecraft Pioneer 10, Pioneer 11, Voyager 1 and Voyager 2 are on course to leave the Solar system. For other uses, see Apollo (disambiguation). ... Apparent magnitude: up to -12. ... This article is about Earth as a planet. ... Technicians work on the Ulysses space probe. ... Major features of the Solar System (not to scale; from left to right): Pluto, Neptune, Uranus, Saturn, Jupiter, the asteroid belt, the Sun, Mercury, Venus, Earth and its Moon, and Mars. ... Pioneer 10 was the first spacecraft to travel through the asteroid belt, and was the first spacecraft to make direct observations of Jupiter. ... Position of Pioneer 10 and 11 Pioneer 11 was the second mission to investigate Jupiter and the outer solar system and the first to explore the planet Saturn and its main rings. ... Trajectory of Voyager 1 using Celestia The Voyager 1 spacecraft is a 733-kilogram robotic space probe of the outer solar system and beyond, launched September 5, 1977, and is currently operational. ... Trajectory Voyager 2 is an unmanned interplanetary spacecraft, launched on August 20, 1977. ...


Robot landers such as Viking, Pathfinder and Mars Exploration Rovers have already landed on the surface of Mars and several Venera and Vega spacecraft have landed on the surface of Venus. The NEAR Shoemaker orbiter successfully landed on the asteroid 433 Eros, even though it was not designed with this maneuver in mind. The Huygens probe successfully landed to Saturn's moon Titan. Viking mission profile. ... The Mars Pathfinder was launched on December 4, 1996 by NASA aboard a Delta II just a month after the Mars Global Surveyor was launched. ... Artists Concept of Rover on Mars (credit: Maas Digital LLC) NASAs Mars Exploration Rover (MER) Mission is an ongoing robotic Mars exploration mission, commenced in 2003, that sent two rovers — Spirit and Opportunity — to explore the Martian surface and geology. ... Mars is the fourth planet from the Sun in the solar system, named after the Roman god of war (the counterpart of the Greek Ares), on account of its blood red color as viewed in the night sky. ... Venera 7 lander Color image taken from the surface of Venus by the Soviet Venera 13 lander The Venera (Russian: Венера; formerly, sometimes referred to as Venusik in the West) series of probes was developed by the USSR to gather data from Venus. ... The Vega mission was a Venus mission which also took advantage of the appearance of Comet Halley in 1986. ... (*min temperature refers to cloud tops only) Atmospheric characteristics Atmospheric pressure 9. ... Artists conception of the NEAR Shoemaker spacecraft Near Earth Asteroid Eros as seen from the NEAR spacecraft. ... The asteroid 433 Eros (eer-os) was named after the Greek god of love Eros. ... The Huygens probe, supplied by the European Space Agency (ESA) and named after the Dutch 17th century astronomer Christiaan Huygens, is an atmospheric entry probe carried to Saturns moon Titan as part of the Cassini-Huygens mission. ... Titan may mean: // Titan (mythology), a class of deities who preceded the Olympians in Greek mythology Helios, Greek sun-deity sometimes referred to as Titan Titan (moon), largest moon of the planet Saturn Titan (rocket family), a family of U.S. expendable rockets Titan (computer), prototype Atlas 2 computer developed...


Economical travel techniques

Interplanetary travel has to solve two problems, other than escaping from the planet of origin:

  • The planet from which the spaceship starts is moving round the sun at a different speed than the planet to which the spaceship is traveling, because the two planets are at different distances from the sun. So as it approaches its destination, the spaceship must decrease its speed if the destination is closer to the sun, or increase its speed if the destination is further away (assuming a Hohmann transfer orbit).
  • If the destination is further away, the spaceship must lift itself "up" against the force of the sun's gravity. Otherwise, it must lift itself "down" against the force of inertia of the Earth.

Doing this by brute force - accelerating in the shortest route to the destination and then, if it is further from the sun, decelerating to match the planet's speed - would require an extremely large amount of fuel. And the fuel required for deceleration and velocity-matching has to be launched along with the payload, and therefore even more fuel is needed in the acceleration phase.


The change in speed (delta-v) required to match velocity with another planet is surprisingly large.[3] For example Venus orbits about 5.2km/second faster than Earth and Mars orbits about 5.7km/second slower. To put these figures in perspective, Earth's escape velocity is about 11.2km/second (it varies slightly depending on the launch direction). So matching a space shuttle's velocity with that of Venus or Mars would require a significant percentage of the energy which is used to launch a shuttle from Earth's surface. General In general physics delta-v is simply the change in velocity. ... Adjectives: Venusian or (rarely) Cytherean Atmosphere Surface pressure: 9. ... This article is about Earth as a planet. ... Adjectives: Martian Atmosphere Surface pressure: 0. ... Space Shuttle Atlantis launches on mission STS-71. ... NASAs Space Shuttle, officially called Space Transportation System (STS), is the United States governments current manned launch vehicle. ...


Hohmann transfers

Hohmann Transfer Orbit: a spaceship leaves from point 2 in Earth's orbit and arrives at point 3 in Mars'

For many years economical interplanetary travel meant using the Hohmann transfer orbit. Hohmann demonstrated that the lowest energy route between any two orbits is an elliptical "orbit" which forms a tangent to the starting and destination orbits. Once the spacecraft arrives, a second application of thrust will re-circularize the orbit at the new location. In the case of planetary transfers this means adjusting the spacecraft, originally in an orbit almost identical to Earth's, such that the apogee is on the far side of the Sun near the orbit of the other planet. A spacecraft traveling from Earth to Mars via this method will arrive near Mars orbit in approximately 18 months, but because the orbital velocity is greater when closer to the center of mass (i.e. the Sun) and slower when farther from the center, the spacecraft will be traveling quite slowly and a small application of thrust is all that is needed. If the manoeuver is timed properly, Mars will be "arriving" under the spacecraft when this happens. Hohmann transfer orbit File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... In astronautics and aerospace engineering, the Hohmann transfer orbit is an orbital maneuver that, under standard assumption, moves a spacecraft from one circular orbit to another using two engine impulses. ... For other uses, see Ellipse (disambiguation). ... In mathematics, the word tangent has two distinct but etymologically-related meanings: one in geometry and one in trigonometry. ... This article is about several astronomical terms (apogee & perigee, aphelion & perihelion, generic equivalents based on apsis, and related but rarer terms. ...


The Hohmann transfer applies to any two orbits, not just those with planets involved. For instance it is the most common way to transfer satellites into geostationary orbit, after first being "parked" in low earth orbit. However the Hohmann transfer takes an amount of time similar to ½ of the orbital period of the outer orbit, so in the case of the outer planets this is many years – too long to wait. It is also based on the assumption that the points at both ends are massless, as in the case when transferring between two orbits around Earth for instance. With a planet at the destination end of the transfer, calculations become considerably more difficult. Geostationary orbit A geostationary orbit (GEO) is a geosynchronous orbit directly above the Earths equator (0° latitude), with orbital eccentricity of zero. ... A low Earth orbit (LEO) is an orbit in which objects such as satellites are below intermediate circular orbit (ICO) and far below geostationary orbit, but typically around 350 - 1400 km above the Earths surface. ...


Gravitational slingshot

Over-simplified example of gravitational slingshot: the spacecraft's velocity changes by up to twice the planet's velocity

The gravitational slingshot technique uses the gravity of planets and moons to change the speed and direction of a spacecraft without using fuel. In typical example, a spacecraft is sent to a distant planet on a path that is much faster than what the Hohmann transfer would call for. This would typically mean that it would arrive at the planet's orbit and continue past it. However if there is a planet between the departure point and the target, it can be used to bend the path toward the target, and in many cases the overall travel time is greatly reduced. A prime example of this are the two craft of the Voyager program, which used slingshot effects to change trajectories several times in the outer solar system. It is difficult to use this method for journeys in the inner part of the solar system, although it is possible to use other nearby planets such as Venus or even the Moon as slingshots in journeys to the outer planets. Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... In orbital mechanics and aerospace engineering, a gravitational slingshot or gravity assist is the use of the gravity of a planet or other celestial body to alter the path and speed of a spacecraft. ... Gravity is a force of attraction that acts between bodies that have mass. ... Voyager Project redirects here. ... (*min temperature refers to cloud tops only) Atmospheric characteristics Atmospheric pressure 9. ... Apparent magnitude: up to -12. ...


Fuzzy orbits

Computers did not exist when Hohmann transfer orbits were first proposed (1925) and were slow, expensive and unreliable when gravitational slingshots were developed (1959). Recent advances in computing have made it possible to exploit many more features of the gravity fields of astronomical bodies and thus calculate even lower-cost trajectories.[4][5] Paths have been calculated which link the Lagrange points of the various planets into the so-called Interplanetary Transport Network. Such "fuzzy orbits" use significantly less energy than Hohmann transfers but are often much slower. They may not offer much advantage for manned missions or for research missions, but may be useful for high-volume transport of low-value commodities if the human species develops a space-based economy. In astronautics and aerospace engineering, the Hohmann transfer orbit is an orbital maneuver that, under standard assumption, moves a spacecraft from one circular orbit to another using two engine impulses. ... Year 1925 (MCMXXV) was a common year starting on Thursday (link will display the full calendar) of the Gregorian calendar. ... In orbital mechanics and aerospace engineering, a gravitational slingshot or gravity assist is the use of the gravity of a planet or other celestial body to alter the path and speed of a spacecraft. ... Year 1959 (MCMLIX) was a common year starting on Thursday (link will display full calendar) of the Gregorian calendar. ... RAM (Random Access Memory) Look up computing in Wiktionary, the free dictionary. ... In celestial mechanics, the Lagrangian points, (also Lagrange point, L-point, or libration point) are the five stationary solutions of the circular restricted three-body problem. ... Artists concept of the Interplanetary Transport Network. ... A commodity is something for which there is demand, but which is supplied without qualitative differentiation across a given market. ...


Aerobraking

Apollo Command Module flying at a high angle of attack to aerobrake by skimmimg the atmosphere, (artistic rendition)

Aerobraking uses the atmosphere of the target planet to slow down. It was first used on the Apollo program where the returning spacecraft did not enter Earth orbit but instead used a series of passes through Earth's atmosphere to reduce its speed until it was safe to land. Aerobraking does not require a thick atmosphere - for example most Mars landers use the technique, and Mars' atmosphere is only about 1% as thick as Earth's. Image File history File links Apollo_cm. ... Image File history File links Apollo_cm. ... In this diagram, the black arrow represents the direction of the wind. ... An artists conception of a spacecraft aerobraking Aerobraking is a technique used by spacecraft in which it uses drag within a planetary atmosphere to reduce its velocity relative to the planet. ... Atmosphere is the general name for a layer of gases that may surround a material body of sufficient mass. ... For other uses, see Apollo (disambiguation). ... Adjectives: Martian Atmosphere Surface pressure: 0. ...


Aerobraking converts the spacecraft's kinetic energy into heat, so it requires a heatshield to prevent the craft from burning up. As a result, aerobraking is only helpful in cases where the fuel needed to transport the heatshield to the planet is less than the fuel that would be required to brake an unshielded craft by firing its engines. The kinetic energy of an object is the extra energy which it possesses due to its motion. ... Atmospheric reentry is the process by which vehicles that are outside the atmosphere of a planet can enter that atmosphere and reach the planetary surface intact. ...


Improved travel technologies

Several technologies have been proposed which both save fuel and provide significantly faster travel than Hohmann transfers. Most are still just theoretical, but the Deep Space One mission was a very successful test of an ion drive. These improved technologies focus on on one or more of: Conceptual drawing The spacecraft Deep Space 1 was launched October 24, 1998 on top of a Delta rocket. ... An ion engine test An ion thruster is a type of spacecraft propulsion that uses beams of ions for propulsion. ...

  • Space propulsion systems with much better fuel economy. Such systems would make it possible to travel much faster while keeping the fuel cost within acceptable limits.
  • Using solar energy and In-Situ Resource Utilization to avoid or minimize the fuel-expensive task of shipping components and fuel up from the Earth's surface, against the Earth's gravity (see "Using non-terrestrial resources", below).

Besides making travel faster, such improvements would allow greater design "safety margins" by reducing the imperative to make spacecraft lighter. 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 used to change the velocity of spacecraft and artificial satellites, or in short, to provide delta-v. ... In astronautics, In-Situ Resource Utilization (ISRU) is the way to describe the use the resources of the planetary body which is explored (Moon, Mars,...) to provide propellant, energy or consumables to the science payload or to the crew which has been deployed there. ...


Electric propulsion

Electric propulsion systems use an external source such as a nuclear reactor or solar cells to generate electricity, which is then used to accelerate a chemically inert propellant to speeds far higher than achieved in a chemical rocket. Such drives produce feeble thrust, and are therefore unsuitable for quick maneuvers or for launching from the surface of a planet. But they are so economical in their use of reaction mass that they can keep firing continuously for days or weeks, while chemical rockets use up reaction mass so quickly that they can only fire for seconds or minutes. Even a trip to the Moon is long enough for an electric propulsion system to outrun a chemical rocket - the Apollo missions took 3 days in each direction. This article or section does not cite its references or sources. ... Core of a small nuclear reactor used for research. ... A solar cell, made from a monocrystalline silicon wafer A solar cell or photovoltaic cell is a device that converts light energy into electrical energy. ... Lightning strikes during a night-time thunderstorm. ... Working mass is a mass against which a system operates in order to produce acceleration. ... For other uses, see Apollo (disambiguation). ...


NASA's Deep Space One was a very successful test of a prototype ion drive, which fired for a total of 678 days and enabled the probe to run down Comet Borrelly, a feat which would have been impossible for a chemical rocket. A more ambitious, nuclear-powered version was intended for an unmanned Jupiter mission, the Jupiter Icy Moons Orbiter, originally planned for launch sometime in the next decade. Due to a shift in priorities at NASA that favored manned space missions, the project lost funding in 2005, effectively canceling the JIMO mission. The spacecraft Deep Space 1 was launched October 24, 1998 on top of a Delta II rocket. ... An ion engine test An ion thruster is a type of spacecraft propulsion that uses beams of ions for propulsion. ... Artistss Conception of Jupiter Icy Moons Orbiter The Jupiter Icy Moons Orbiter (JIMO) was a proposed spacecraft designed to explore the icy moons of Jupiter. ...


Solar Sails

Solar sails rely on the fact that light reflected from a surface exerts pressure on the surface. The radiation pressure is small and decreases by the square of the distance from the sun, but unlike rockets, solar sails require no fuel. Although the thrust is small, it continues as long as the sun shines and the sail is deployed.[6] Solar sails (also called light sails, especially when they use light sources other than the Sun) are a proposed form of spacecraft propulsion. ... Radiation pressure is the pressure exerted upon any surface exposed to electromagnetic radiation. ...


The original concept relied only on radiation from the sun - for example in Arthur C. Clarke's 1965 story "Sunjammer". More recent light sail designs propose to boost the thrust by aiming ground-based lasers or masers at the sail. Ground-based lasers or masers can also help a light-sail spacecraft to decelerate: the sail splits into an outer and inner section, the outer section is pushed forward and its shape is changed mechanically to focus reflected radiation on the inner portion, and the radiation focused on the inner section acts as a brake. Sir Arthur Charles Clarke, CBE (born 16 December 1917) is a British science-fiction author and inventor, most famous for his novel 2001: A Space Odyssey, and for collaborating with director Stanley Kubrick on the film of the same name. ... Sunjammer is a science fiction short story by Arthur C. Clarke. ... Experiment with a laser (US Military) In physics, a laser is a device that emits light through a specific mechanism for which the term laser is an acronym: Light Amplification by Stimulated Emission of Radiation. ... A hydrogen radio frequency discharge, the first element inside a hydrogen maser (see description below) A maser is a device that produces coherent electromagnetic waves through amplification due to stimulated emission. ... Experiment with a laser (US Military) In physics, a laser is a device that emits light through a specific mechanism for which the term laser is an acronym: Light Amplification by Stimulated Emission of Radiation. ... A hydrogen radio frequency discharge, the first element inside a hydrogen maser (see description below) A maser is a device that produces coherent electromagnetic waves through amplification due to stimulated emission. ...


Although most articles about light sails focus on interstellar travel, there have been several proposals for their use within the solar system. Artists Impression of the compression of a viewers perspective in front of a ship during interstellar travel Interstellar space travel is unmanned or manned travel between stars, though the term usually denotes the latter. ...


No spacecraft powered only or mainly by light sails have been built. But ordinary spacecraft and satellites sometimes use solar collectors, temperature-control panels and sun shades as light sails, to make minor corrections to their attitude and orbit without using fuel. A few have even had small purpose-built solar sails for this use (for example Eurostar E3000 geostationary communications satellites built by EADS Astrium). A geostationary orbit (abbreviated GEO) is a circular orbit in the Earths equatorial plane, any point on which revolves about the Earth in the same direction and with the same period as the Earths rotation. ... EADS Astrium, one of the three business units of EADS Space, this company being a subsidiary of EADS, is an European space manufacturer involved in the manufacture of spacecraft used for science, Earth observation and telecommunication, as well as the equipment and subsystems used therein and related ground systems. ...


Nuclear thermal and solar thermal rockets

Sketch of nuclear thermal rocket
Sketch of nuclear thermal rocket

In a nuclear thermal rocket or solar thermal rocket a working fluid, usually hydrogen, is heated in a high temperature, and then expands through a rocket nozzle to create thrust. The energy replaces the chemical energy of the reactive chemicals in a traditional rocket engine. Due to the low molecular mass and hence high thermal velocity of hydrogen these engines are at least twice as fuel efficient as chemical engines, even after including the weight of the reactor.[citation needed] Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... In a nuclear thermal rocket a working fluid, usually hydrogen, is heated in a high temperature nuclear reactor, and then expands through a rocket nozzle to create thrust. ... Solar thermal propulsion is a form of spacecraft propulsion that makes use of solar power to directly heat reaction mass, and therefore does not require an electrical generator as most other forms of solar-powered propulsion do. ... General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... Rocket Nozzle A nozzle is a mechanical device designed to control the characteristics of a fluid flow as it exits from an enclosed chamber into some medium. ... Thrust is a reaction force described quantitatively by Newtons Second and Third Laws. ... A cold (un-ignited) rocket engine test at NASA A rocket engine is a reaction engine that can be used for spacecraft propulsion as well as terrestrial uses, such as missiles. ...


The US Atomic Energy Commission and NASA tested a few designs from 1959 to 1968 . The NASA designs were conceived as replacements for the upper stages of the Saturn 5 launch vehicle, but the tests revealed reliability problems, mainly caused by the vibration and heating involved in running the engines at such high thrust levels. Political and environmental considerations make it unlikely such an engine will be used in the foreseeable future, since nuclear thermal rockets would be most useful at or near the Earth's surface and the consequences of a malfunction could be horrific. Almost a year after World War II ended, Congress established the United States Atomic Energy Commission to foster and control the peace time development of atomic science and technology. ... The National Aeronautics and Space Administration (NASA) is an agency of the United States federal government, responsible for the nations public space program. ... This article is about the rocket. ...


Cyclers

It is possible to put stations or spacecraft on orbits that cycle between different planets, for example a Mars cycler would synchronously cycle between Mars and Earth, with very little propellant usage to maintain the trajectory. Cyclers are conceptually a good idea, because massive radiation shields, life support and other equipment only need to be put onto the cycler trajectory once. A cycler could combine several roles: habitat (for example it could spin to produce an "artificial gravity" effect); mothership (providing life support for the crews of smaller spacecraft which hitch a ride on it).[7] Cyclers' main limitation would be that they would be slow, because they would rely on gravitational techniques such as Hohmann transfer orbits and gravitational slingshots. Wikipedia does not yet have an article with this exact name. ... In astronautics and aerospace engineering, the Hohmann transfer orbit is an orbital maneuver that, under standard assumption, moves a spacecraft from one circular orbit to another using two engine impulses. ... In orbital mechanics and aerospace engineering, a gravitational slingshot or gravity assist is the use of the gravity of a planet or other celestial body to alter the path and speed of a spacecraft. ...


Space elevator

A space elevator is a structure designed to transport material from a planet's surface into orbit.[8] The fundamental idea is that, once the expensive job of building the elevator is complete, an indefinite number of loads can be transported into orbit at minimal cost. Even the simplest designs avoid the vicious circle of rocket launches from the surface, the difficulty that: the fuel needed to travel the last 10% of the distance to orbit must be lifted all the way from the surface; that requires extra fuel; most of the extra fuel must be lifted most of the way before it is burned; that requires more extra fuel; and so on. More sophisticated space elevator designs reduce the energy cost per trip by using counterweights, and the most ambitious schemes aim to balance loads going up and down and thus make the energy cost close to zero. Space elevators have also sometimes been referred to as "beanstalks", "space bridges", "space lifts", "space ladders" or "orbital towers". A space elevator would consist of a cable anchored to the Earths surface, reaching into space. ... Vicious Circle is an album released in 1995 by L.A. Guns. ... This article or section does not cite its references or sources. ... A space elevator would consist of a cable attached to the surface and reaching outwards into space. ...


A terrestrial space elevator is beyond our current technology, although a lunar space elevator could theoretically be built using existing materials.


Using non-terrestrial resources

Current space vehicles attempt to launch with all their fuel (propellants and energy supplies) on-board that they will need for their entire journey, and current space structures are lifted from the Earth's surface. Non-terrestrial sources of energy and materials are mostly a lot further away, but most would not require lifting out of a strong gravity field and therefore should be much cheaper to use in space in the long term. In astronautics, In-Situ Resource Utilization (ISRU) is the way to describe the use the resources of the planetary body which is explored (Moon, Mars,...) to provide propellant, energy or consumables to the science payload or to the crew which has been deployed there. ...


The most important non-terrestrial resource is energy, because it can be used to transform non-terrestrial materials into useful forms (some of which may also produce energy). At least two fundamental non-terrestrial energy sources have been proposed: solar-powered energy generation (unhampered by clouds), either directly by solar cells or indirectly by focusing solar radiation on boilers which produce steam to drive generators; and electrodynamic tethers which generate electricity from the powerful magnetic fields of some planets (Jupiter has a very powerful magnetic field). A solar cell, made from a monocrystalline silicon wafer A solar cell or photovoltaic cell is a device that converts light energy into electrical energy. ... Electrodynamic tethers are long conducting wires (such as the one deployed from the tether satellite) which can operate on the well known electromagnetic priciples as a generator (via converting its velocity to electric energy) or engine (ultilizing electric energy for velocity). ... Adjectives: Jovian Atmosphere Surface pressure: 20–200 kPa[4] (cloud layer) Composition: ~86% Molecular hydrogen ~13% Helium 0. ...


Water ice would be very useful if it can be found on the moons of Jupiter or Saturn (except that we might not want to mine Europa for ice so long as there is a possibility of finding life there): Adjectives: Jovian Atmosphere Surface pressure: 20–200 kPa[4] (cloud layer) Composition: ~86% Molecular hydrogen ~13% Helium 0. ... Adjectives: Saturnian Atmosphere Surface pressure: 140 kPa Composition: >93% hydrogen >5% helium 0. ... Europa is the name of : Europe, the continent, in most European languages (most Germanic languages, Latin and some Romance languages, and some Slavic Languages) Europa (mythology), a beautiful Phoenician princess in Greek mythology Europa (moon), the smallest of the Galilean moons of planet Jupiter Europa, a small island in the...

  • The low gravity of these moons would make them a cheaper source of water for space stations and planetary bases than lifting it up from Earth's surface.
  • Non-terrestrial power supplies could be used to electrolyse water ice into into oxygen and hydrogen for use in bipropellant rocket engines.
  • Solar thermal rockets could use it as reaction mass. Hydrogen has also been proposed for use in these engines and would provide much greater specific impulse (thrust per kilogram of reaction mass), but it has been claimed that water will beat hydrogen in cost/performance terms despite its much lower specific impulse by orders of magnitude.[9][10].

Oxygen is a common constituent of the moons crust, and is probably abundant in most other bodies in the solar system. Non-terrestrial oxygen would be about as valuable as water ice, for example: This article is about the chemical process. ... F-1 rocket engine (The kind used by the Saturn V.) A bipropellant rocket engine is a rocket engine that uses two fluid propellants stored in separate tanks that are injected into, and undergo a strong exothermic reaction, in a rockets combustion chamber. ... Solar thermal propulsion is a form of spacecraft propulsion that makes use of solar power to directly heat reaction mass, and therefore does not require an electrical generator as most other forms of solar-powered propulsion do. ... Working mass is a mass against which a system operates in order to produce acceleration. ... Specific impulse (usually abbreviated Isp) is a way to describe the efficiency of rocket and jet engines. ... Apparent magnitude: up to -12. ...

  • In the life support systems of space ships, space stations and planetary bases.
  • In rocket engines. Even if the other propellant has to be lifted from Earth, using non-terrestrial oxygen could reduce propellant launch costs by up to 2/3 for hydrocarbon fuel, or 85% for hydrogen. The savings are so high because oxygen accounts for the majority of the mass in most rocket propellant combinations.

Scientists expect to find a vast range of organic compounds in some of the planets, moons and comets of the outer solar system, and the range of possible uses is even wider. For example methane can be used be used as a fuel (burned with non-terrestrial oxygen), or as a feedstock for petrochemical processes such as making plastics. And ammonia could be a valuable feedstock for producing fertilizers to be used in the vegetable gardens of orbital and planetary bases, reducing the need to lift food to them from Earth. In human spaceflight, the life support system is a group of devices that allow a human being to survive in outer space. ... Rocket propellants undergo exothermic chemical reactions which produce hot gas which is used by a rocket for propulsive purposes. ... Benzene is the simplest of the arenes, a family of organic compounds An organic compound is any member of a large class of chemical compounds whose molecules contain carbon and hydrogen; therefore, carbides, carbonates, carbon oxides and elementary carbon are not organic (see below for more on the definition controversy... The outer solar system (as opposed to the outer planets) is that part of the Solar System which begins at roughly the orbit of Neptune and terminates at maximum orbit distance, approximately one Light Year from the sun in terms of orbital measurements. ... Methane is a chemical compound with the molecular formula CH4. ... A feedstock is a petrochemical used as a raw material to be fed into a machine or processing plant. ... Petrochemicals are chemical products made from raw materials of petroleum (hydrocarbon) origin. ... This article or section does not cite any references or sources. ... Ammonia is a compound with the formula NH3. ... Spreading manure, an organic fertilizer Fertilizers (also spelled fertilisers) are compounds given to plants to promote growth; they are usually applied either via the soil, for uptake by plant roots, or by foliar feeding, for uptake through leaves. ...


Even unprocessed rock may be useful as rocket propellant if mass drivers are employed. A mass driver for lunar launch (artists conception) A mass driver or electromagnetic catapult is a method of spacecraft propulsion that would use a linear motor to accelerate payloads up to high speeds. ...


Exotic propulsion

See the spacecraft propulsion article for a discussion of a number of other technologies that could, in the medium to longer term, be the basis of interplanetary missions. Unlike the situation with interstellar travel, the barriers to fast interplanetary travel involve engineering and economics rather than any basic physics. New physics for space propulsion will need to be invented and old physics concepts of the forties will need to be put on the shelf. 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 Propulsion means to add speed or acceleration to an object, by an engine or other similar device. ... Artists Impression of the compression of a viewers perspective in front of a ship during interstellar travel Interstellar space travel is unmanned or manned travel between stars, though the term usually denotes the latter. ...


Difficulties of manned interplanetary travel

Life support

Life support systems must be capable of supporting human life for weeks, months or even years. A breathable atmosphere of at least 0.35 bar (5psi) must be maintained, with adequate amounts of oxygen, nitrogen, and controlled levels of carbon dioxide, trace gases and water vapour.


In practice on the International Space Station the Elektron oxygen generator unit has been temperamental. International Space Station insignia ISS Statistics Crew: 3 As of June 20, 2007 Perigee: 319. ... Elektron is a Russian oxygen generator used on board the International Space Station (ISS). ...


Radiation

Once a vehicle leaves low earth orbit and the protection of Earth's magnetosphere, it enters the Van Allen radiation belt, a region of high radiation. Once through there the radiation drops to lower levels, with a constant background of high energy cosmic rays. These are dangerous over periods of years to decades. A low Earth orbit (LEO) is an orbit in which objects such as satellites are below intermediate circular orbit (ICO) and far below geostationary orbit, but typically around 350 - 1400 km above the Earths surface. ... Van Allen radiation belts The Van Allen Radiation Belt is a torus of energetic charged particles (plasma) around Earth, held in place by Earths magnetic field. ... Cosmic rays can loosely be defined as energetic particles originating outside of the Earth. ...


In addition, Coronal mass ejections from the Sun are highly dangerous, and are fatal within a very short timescale to humans unless they are protected by massive shielding ( [1] [2] [3] [4] [5] [6] [7] [8] ). A solar coronal mass ejection blasts plasma throughout the Solar System. ... The Sun (Latin: Sol) is the star at the center of the Solar System. ...


Reliability

Any major failure to a spacecraft en route is likely to be fatal, and even a minor one could have dangerous results if not repaired quickly, something difficult to accomplish in open space.


Launch windows

For astrodynamics reasons, travel to other planets is only practical within certain time windows. Outside these windows the planets are essentially inaccessible from Earth with current technology. This constrains flights and prevents rescue in an emergency. Astrodynamics is the study of the motion of rockets, missiles, and space vehicles, as determined from Sir Isaac Newtons laws of motion and his law of universal gravitation. ...


Feasibility of manned interplanetary travel

While manned interplanetary travel (with the arguable exception of the Apollo program) has not yet been achieved, a trip to Mars is probably feasible, even with chemical rocket propulsion, and could probably be achieved within a decade (at most two) if the funds were made available. NASA's "Design Reference Mission" proposes a Mars exploration program costing $50 billion, but others have made detailed proposals with projected costs much less (see Mars Direct). Mars is the fourth planet from the Sun in the solar system, named after the Roman god of war (the counterpart of the Greek Ares), on account of its blood red color as viewed in the night sky. ... The National Aeronautics and Space Administration (NASA) is an agency of the United States federal government, responsible for the nations public space program. ... Mars Direct is a proposal for a relatively low-cost manned mission to Mars with current rocket technology. ...


See also

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 Propulsion means to add speed or acceleration to an object, by an engine or other similar device. ... General In general physics delta-v is simply the change in velocity. ... The Wait Calculation was introduced by Andrew Kennedy in his paper, Interstellar Travel: The Wait Calculation and the Incentive Trap of Progress, JBIS V 59 no 7 July 2006. ...

References

  1. ^ Crawford, I.A. (1998). The Scientific Case for Human Spaceflight 14-17.
  2. ^ Valentine, L (2002). A Space Roadmap: Mine the Sky, Defend the Earth, Settle the Universe. Space Studies Institute, Princeton.
  3. ^ Error on call to Template:cite web: Parameters url and title must be specified.
  4. ^ Gravity's Rim. discovermagazine.com.
  5. ^ Belbruno, E. 2004. Capture Dynamics and Chaotic Motions in Celestial Mechanics: With the Construction of Low Energy Transfers, Princeton University Press
  6. ^ Abstracts of NASA articles on solar sails.
  7. ^ Aldrin, B (2005). Buzz Aldrin's Roadmap To Mars. Popular Mechanics.
  8. ^ David, D (2002). The Space Elevator Comes Closer to Reality. space.com.
  9. ^ Origin of How Steam Rockets can Reduce Space Transport Cost by Orders of Magnitude
  10. ^ "Neofuel" -interplanetary travel using off-earth resources

  Results from FactBites:
 
Interplanetary travel - Wikipedia, the free encyclopedia (1272 words)
By definition, interplanetary travel is travel between bodies in a given star system.
In the case of planetary transfers this means adjusting the spacecraft, originally in an orbit almost identical to Earth's, such that the apogee is on the far side of the Sun near the orbit of the other planet.
While manned interplanetary travel (with the arguable exception of the Apollo program) has not yet been achieved, a trip to Mars is probably feasible, even with chemical rocket propulsion, and could probably be achieved within a decade (at most two) if the funds were made available.
Interstellar travel - Wikipedia, the free encyclopedia (1848 words)
Interstellar space travel is unmanned or manned travel between stars, though the term usually denotes the latter.
The concept of interstellar travel in starships is a staple in science fiction.
There is a tremendous difference between interstellar travel and interplanetary travel, mainly due to the much larger distances involved.
  More results at FactBites »

 
 

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