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. There are many different methods. Each method has drawbacks and advantages, and spacecraft propulsion is an active area of research. However, most spacecraft today are propelled by exhausting a gas from the back/rear of the vehicle at very high speed through a supersonic de Laval nozzle. This sort of engine is called a rocket engine. Image:NASA-SSME-test-firing. ... Image:NASA-SSME-test-firing. ... The John C. Stennis Space Center (or SSC), located in Hancock County, Mississippi at the Mississippi/Louisiana border, is NASAs largest rocket engine test facility. ... Hancock County is a county located in the state of Mississippi. ... The Space Shuttle Discovery as seen from the International Space Station. ... For other uses, see Satellite (disambiguation). ... Figure 1: A de Laval nozzle, showing approximate flow velocity increasing from green to red in the direction of flow The main type of rocket engine nozzles used in modern rocket engines is the de Laval nozzle which is used to expand and accelerate the combustion gases, from burning propellants... For other uses, see Engine (disambiguation). ... 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. ...

All current spacecraft use chemical rockets (bipropellant or solid-fuel) for launch, though some (such as the Pegasus rocket and SpaceShipOne) have used air-breathing engines on their first stage. Most satellites have simple reliable chemical rockets (often monopropellant rockets) or resistojet rockets to keep their station, although some use momentum wheels for attitude control. Newer geo-orbiting spacecraft are starting to use electric propulsion for north-south stationkeeping. Interplanetary vehicles mostly use chemical rockets as well, although a few have experimentally used ion thrusters (a form of electric propulsion) with some success. 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. ... The Space Shuttle is initially launched with the help of solid-fuel boosters A Solid rocket or a solid fuel rocket is a rocket with a motor that uses solid propellants (fuel/oxidizer). ... Pegasus rocket on the ground Pegasus rocket attached to bottom of carrier aircraft The Pegasus rocket is a winged space booster developed by Orbital Sciences Corporation (Orbital). ... SpaceShipOne is small, having a three-person cabin and short but wide wings. ... The second stage of a Minuteman III rocket A multistage (or multi-stage) rocket is, like any rocket, propelled by the recoil pressure of the burning gases it emits as it burns fuel. ... A monopropellant rocket (or monoprop rocket) is a rocket that uses a single chemical as its power source and propellant. ... A resistojet is a way of propulsion that provides thrust by heating a (typically non-reactive) fluid. ... Gyroscope of the International Space Station A momentum wheel or reaction wheel is a type of flywheel used primarily by spacecraft to change their angular momentum without using fuel for rockets or other reaction devices. ... // In the context of spacecraft, attitude control is control of the angular position and rotation of the spacecraft, either relative to the object that it is orbiting, or relative to the celestial sphere. ... This article or section does not cite its references or sources. ... An ion engine test This article focuses on electrostatic ion thrusters - for a more general description, refer to electric propulsion. ...

The necessity for propulsion system

Artificial satellites must be launched into orbit, and once there they must be placed in their nominal orbit. Once in the desired orbit, they often need some form of attitude control so that they are correctly pointed with respect to the Earth, the Sun, and possibly some astronomical object of interest.^[1] They are also subject to drag from the thin atmosphere, so that to stay in orbit for a long period of time some form of propulsion is occasionally necessary to make small corrections (orbital stationkeeping).^[2] Many satellites need to be moved from one orbit to another from time to time, and this also requires propulsion.^[3] When a satellite has exhausted its ability to adjust its orbit, its useful life is over. Rockets (including missiles) can be launched from the following: for a launch into an orbital spaceflight and beyond: a launch pad, including a floating platform (see San Marco platform, Sea Launch) for the launch into a suborbital flight also: a missile silo a mobile launcher vehicle a submarine air launch... Two bodies with a slight difference in mass orbiting around a common barycenter. ... // In the context of spacecraft, attitude control is control of the angular position and rotation of the spacecraft, either relative to the object that it is orbiting, or relative to the celestial sphere. ... This article is about Earth as a planet. ... Sol redirects here. ... For other uses, see Astronomy (disambiguation). ... Atmospheric drag is a form of drag, which is the force that opposes an object moving through a liquid or gas. ... “Air” redirects here. ... In astrodynamics orbital stationkeeping is a term used to describe a particular set of orbital maneuvers used to keep a spacecraft in assigned orbit, either low earth orbit (LEO), or geostationary orbit (GEO). ...

Spacecraft designed to travel further also need propulsion methods. They need to be launched out of the Earth's atmosphere just as satellites do. Once there, they need to leave orbit and move around.

For interplanetary travel, a spacecraft must use its engines to leave Earth orbit. Once it has done so, it must somehow make its way to its destination. Current interplanetary spacecraft do this with a series of short-term trajectory adjustments.^[4] In between these adjustments, the spacecraft simply falls freely along its orbit. The simplest fuel-efficient means to move from one circular orbit to another is with a Hohmann transfer orbit: the spacecraft begins in a roughly circular orbit around the Sun. A short period of thrust in the direction of motion accelerates or decelerates the spacecraft into an elliptical orbit around the Sun which is tangential to its previous orbit and also to the orbit of its destination. The spacecraft falls freely along this elliptical orbit until it reaches its destination, where another short period of thrust accelerates or decelerates it to match the orbit of its destination.^[5] Special methods such as aerobraking are sometimes used for this final orbital adjustment.^[6] By definition, interplanetary travel is travel between bodies in a given star system; especially the solar system. ... Freefall or free fall in the strict sense is the condition of acceleration which is due only to gravity. ... 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. ... Thrust is a reaction force described quantitatively by Newtons Second and Third Laws. ... 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. ...

Artist's conception of a solar sail

Some spacecraft propulsion methods such as solar sails provide very low but inexhaustible thrust;^[7] an interplanetary vehicle using one of these methods would follow a rather different trajectory, either constantly thrusting against its direction of motion in order to decrease its distance from the Sun or constantly thrusting along its direction of motion to increase its distance from the Sun. NASA artists conception of a solar sail, from [1]. File links The following pages link to this file: Spacecraft propulsion Solar sail User:Patrick/w Categories: NASA images ... NASA artists conception of a solar sail, from [1]. File links The following pages link to this file: Spacecraft propulsion Solar sail User:Patrick/w Categories: NASA images ... 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. ...

Spacecraft for interstellar travel also need propulsion methods. No such spacecraft has yet been built, but many designs have been discussed. Since interstellar distances are very great, a tremendous velocity is needed to get a spacecraft to its destination in a reasonable amount of time. Acquiring such a velocity on launch and getting rid of it on arrival will be a formidable challenge for spacecraft designers.^[8] Artists depiction of a hypothetical Wormhole Induction Propelled Spacecraft, based loosely on the 1994 warp drive paper of Miguel Alcubierre. ...

Effectiveness of propulsion systems

When in space, the purpose of a propulsion system is to change the velocity, or v, of a spacecraft. Since this is more difficult for more massive spacecraft, designers generally discuss momentum, mv. The amount of change in momentum is called impulse.^[9] So the goal of a propulsion method in space is to create an impulse. This article is about momentum in physics. ... In classical mechanics, the impulse of a constant force is the product of the force and the time during which it acts. ...

When launching a spacecraft from the Earth, a propulsion method must overcome a higher gravitational pull to provide a net positive acceleration.^[10] In orbit, the spacecraft tangential velocity provides a centrifugal acceleration that counteracts the acceleration due to gravity at a given path (which is actually the orbit path) so that any additional impulse, even very tiny, will result in a change in the orbit path. In astrodynamics, gravity drag is inefficiency encountered by a spacecraft thrusting while moving against a gravitational field. ...

The rate of change of velocity is called acceleration, and the rate of change of momentum is called force. To reach a given velocity, one can apply a small acceleration over a long period of time, or one can apply a large acceleration over a short time. Similarly, one can achieve a given impulse with a large force over a short time or a small force over a long time. This means that for maneuvering in space, a propulsion method that produces tiny accelerations but runs for a long time can produce the same impulse as a propulsion method that produces large accelerations for a short time. When launching from a planet, tiny accelerations cannot overcome the planet's gravitational pull and so cannot be used. Acceleration is the time rate of change of velocity and/or direction, and at any point on a velocity-time graph, it is given by the slope of the tangent to the curve at that point. ... its made by jaypeeng magandang google wikepedia For other uses, see Force (disambiguation). ...

The Earth's surface is situated fairly deep in a gravity well and it takes a velocity of 11.2 kilometers/second (escape velocity) or more to escape from it. As human beings evolved in a gravitational field of 1g (9.8 m/s²), an ideal propulsion system would be one that provides a continuous acceleration of 1g (though human bodies can tolerate much larger accelerations over short periods). The occupants of a rocket or spaceship having such a propulsion system would be free from all the ill effects of free fall, such as nausea, muscular weakness, reduced sense of taste, or leaching of calcium from their bones. A gravity well is the scientific/science fictional term for the distortion in space-time caused by a massive body such as a planet. ... Space Shuttle Atlantis launches on mission STS-71. ... For other uses, see Free-fall (disambiguation). ...

The law of conservation of momentum means that in order for a propulsion method to change the momentum of a space craft it must change the momentum of something else as well. A few designs take advantage of things like magnetic fields or light pressure in order to change the spacecraft's momentum, but in free space the rocket must bring along some mass to accelerate away in order to push itself forward. Such mass is called reaction mass. In physics, a conservation law states that a particular measurable property of an isolated physical system does not change as the system evolves. ...

In order for a rocket to work, it needs two things: reaction mass and energy. The impulse provided by launching a particle of reaction mass having mass m at velocity v is mv. But this particle has kinetic energy mv²/2, which must come from somewhere. In a conventional solid, liquid, or hybrid rocket, the fuel is burned, providing the energy, and the reaction products are allowed to flow out the back, providing the reaction mass. In an ion thruster, electricity is used to accelerate ions out the back. Here some other source must provide the electrical energy (perhaps a solar panel or a nuclear reactor), while the ions provide the reaction mass.^[10] The Space Shuttle is initially launched with the help of solid-fuel boosters A Solid rocket or a solid fuel rocket is a rocket with a motor that uses solid propellants (fuel/oxidizer). ... A liquid rocket engine has fuel and oxidizer in liquid form, as opposed to a solid rocket or hybrid rocket or gaseous propellant. ... A hybrid rocket propulsion system comprises propellants of two different states of matter, the most common configuration being a rocket engine composed of a solid propellant lining a combustion chamber into which a liquid or gaseous propellant is injected so as to undergo a strong exothermic reaction to produce hot... An ion engine test This article focuses on electrostatic ion thrusters - for a more general description, refer to electric propulsion. ... A photovoltaic module is composed of individual PV cells. ... Core of a small nuclear reactor used for research. ...

When discussing the efficiency of a propulsion system, designers often focus on effectively using the reaction mass. Reaction mass must be carried along with the rocket and is irretrievably consumed when used. One way of measuring the amount of impulse that can be obtained from a fixed amount of reaction mass is the specific impulse, the impulse per unit weight-on-Earth (typically designated by I_sp). The unit for this value is seconds. Since the weight on Earth of the reaction mass is often unimportant when discussing vehicles in space, specific impulse can also be discussed in terms of impulse per unit mass. This alternate form of specific impulse uses the same units as velocity (e.g. m/s), and in fact it is equal to the effective exhaust velocity of the engine (typically designated v_e). Confusingly, both values are sometimes called specific impulse. The two values differ by a factor of g, the acceleration due to gravity on the Earth's surface (I_spg = v_e). Specific impulse (usually abbreviated Isp) is a way to describe the efficiency of rocket and jet engines. ... g (also gee, g-force or g-load) is a non-SI unit of acceleration defined as exactly 9. ...

A rocket with a high exhaust velocity can achieve the same impulse with less reaction mass. However, the energy required for that impulse is proportional to the square of the exhaust velocity, so that more mass-efficient engines require much more energy, and are typically less energy efficient. This is a problem if the engine is to provide a large amount of thrust. To generate a large amount of impulse per second, it must use a large amount of energy per second. So highly (mass) efficient engines require enormous amounts of energy per second to produce high thrusts. As a result, most high-efficiency engine designs also provide very low thrust.

Delta-v and propellant use

Rocket mass ratios versus final velocity, as calculated from the rocket equation.

Burning the entire usable propellant of a spacecraft through the engines in a straight line in free space would produce a net velocity change to the vehicle; this number is termed 'delta-v' (Δv). Image File history File links Size of this preview: 800 × 529 pixelsFull resolution (1014 × 670 pixel, file size: 27 KB, MIME type: image/png) I, the copyright holder of this work, hereby release it into the public domain. ... Image File history File links Size of this preview: 800 × 529 pixelsFull resolution (1014 × 670 pixel, file size: 27 KB, MIME type: image/png) I, the copyright holder of this work, hereby release it into the public domain. ... In aerospace engineering, mass ratio is a measure of the proportion of a rocket that is propellant. ... General In general physics delta-v is simply the change in velocity. ...

If the exhaust velocity is constant then the total Δv of a vehicle can be calculated using the rocket equation, where M is the mass of fuel (or rather the mass of propellant), P is the mass of the payload (including the rocket structure), and v_e is the velocity of the rocket exhaust. This is known as the Tsiolkovsky rocket equation: Tsiolkovskys rocket equation, named after Konstantin Tsiolkovsky who independently derived it, considers the principle of a rocket: a device that can apply an acceleration to itself (a thrust) by expelling part of its mass with high speed in the opposite direction, due to the conservation of momentum. ...

For historical reasons, as discussed above, v_e is sometimes written as

v_e = I_spg_o

where I_sp is the specific impulse of the rocket, measured in seconds, and g_o is the gravitational acceleration at sea level. Specific impulse (usually abbreviated Isp) is a way to describe the efficiency of rocket and jet engines. ... In physics, gravitational acceleration is the acceleration of an object caused by the force of gravity from another object. ...

For a high delta-v mission, the majority of the spacecraft's mass needs to be reaction mass. Since a rocket must carry all of its reaction mass, most of the initially-expended reaction mass goes towards accelerating reaction mass rather than payload. If the rocket has a payload of mass P, the spacecraft needs to change its velocity by Δv, and the rocket engine has exhaust velocity v_e, then the mass M of reaction mass which is needed can be calculated using the rocket equation and the formula for I_sp:

For Δv much smaller than v_e, this equation is roughly linear, and little reaction mass is needed. If Δv is comparable to v_e, then there needs to be about twice as much fuel as combined payload and structure (which includes engines, fuel tanks, and so on). Beyond this, the growth is exponential; speeds much higher than the exhaust velocity require very high ratios of fuel mass to payload and structural mass. For other uses, see Linear (disambiguation). ...

Energy use

Some energy must go into accelerating the reaction mass. Every engine will waste some energy, but even assuming 100% efficiency, the engine will need energy amounting to

Due to energy carried away in the exhaust the energy efficiency of a reaction engine varies with the speed of the exhaust relative to the speed of the vehicle

Comparing the rocket equation (which shows how much energy ends up in the final vehicle) and the above equation (which shows the total energy required) shows that even with 100% engine efficiency, certainly not all energy supplied ends up in the vehicle - some of it, indeed usually most of it, ends up as kinetic energy of the exhaust. Image File history File links PropulsiveEfficiency. ... Image File history File links PropulsiveEfficiency. ...

Interestingly, if the I_sp is fixed, for a mission delta-v, there is a particular I_sp that minimises the overall energy used by the rocket. This comes to an exhaust velocity of about ⅔ of the mission delta-v (see the energy computed from the rocket equation). Drives with a specific impulse that is both high and fixed such as Ion thrusters have exhaust velocities that can be enormously higher than this ideal, and thus end up powersource limited and give very low thrust. Where the vehicle performance is power limited, e.g. if solar power or nuclear power is used, then in the case of a large v_e the maximum acceleration is inversely proportional to it. Hence the time to reach a required delta-v is proportional to v_e. Thus the latter should not be too large. Tsiolkovskys rocket equation, named after Konstantin Tsiolkovsky who independently derived it, considers the principle of a rocket: a device that can apply an acceleration to itself (a thrust) by expelling part of its mass with high speed in the opposite direction, due to the conservation of momentum. ... Solar power describes a number of methods of harnessing energy from the light of the sun. ...

On the other hand if the exhaust velocity can be made to vary so that at each instant it is equal and opposite to the vehicle velocity then the absolute minimum energy usage is achieved. When this is achieved, the exhaust stops in space ^  and has no kinetic energy; and all the energy ends up in the vehicle (in principle such a drive would be 100% efficient, in practice there would be thermal losses from within the drive system and residual heat in the exhaust). However in most cases this uses an impractical quantity of propellant, but is a useful theoretical consideration.

Some drives (such as VASIMR or Electrodeless plasma thruster ) actually can significantly vary their exhaust velocity. This can help reduce propellant usage and improve acceleration at different stages of the flight. However the best energetic performance and acceleration is still obtained when the exhaust velocity is close to the vehicle speed. Proposed ion and plasma drives usually have exhaust velocities enormously higher than that ideal (in the case of VASIMR the lowest quoted speed is around 15000 m/s compared to a mission delta-v from high Earth orbit to Mars of about 4000m/s). VASIMR test bed The Variable specific impulse magnetoplasma rocket (VASIMR) is a hypothetical form of spacecraft propulsion that uses radio waves and magnetic fields to accelerate a propellant. ... The Electrodeless Plasma Thruster is a spacecraft propulsion engine. ... General In general physics delta-v is simply the change in velocity. ...

For a mission, for example, when launching from or landing on a planet, the effects of gravitational attraction and any atmospheric drag must be overcome by using fuel. It is typical to combine the effects of these and other effects into an effective mission delta-v. For example a launch mission to low Earth orbit requires about 9.3-10 km/s delta-v. These mission delta-vs are typically numerically integrated on a computer. General In general physics delta-v is simply the change in velocity. ...

Example

Suppose we want to send a 10,000 kg space probe to Mars. The required Δv from LEO is approximately 3000 m/s, using a Hohmann transfer orbit. (A manned probe would need to take a faster route and use more fuel). For the sake of argument, let us say that the following thrusters may be used: 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. ... 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. ...

Observe that the more fuel-efficient engines can use far less fuel; its mass is almost negligible (relative to the mass of the payload and the engine itself) for some of the engines. However, note also that these require a large total amount of energy. For earth launch engines require a thrust to weight ratio of much more than unity. To do this they would have to be supplied with Gigawatts of power — equivalent to a major metropolitan generating station. This would need to be carried on the vehicle, which is clearly impractical. Specific impulse (usually abbreviated Isp) is a way to describe the efficiency of rocket and jet engines. ... The Space Shuttle is initially launched with the help of solid-fuel boosters A Solid rocket or a solid fuel rocket is a rocket with a motor that uses solid propellants (fuel/oxidizer). ... 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. ... An ion engine test This article focuses on electrostatic ion thrusters - for a more general description, refer to electric propulsion. ... Electricity generation is the first process in the delivery of electricity to consumers. ...

Instead, a much smaller, less powerful generator may be included which will take much longer to generate the total energy needed. This lower power is only sufficient to accelerate a tiny amount of fuel per second, but over long periods the velocity will be finally achieved. For example. it took the Smart 1 more than a year to reach the Moon, while with a chemical rocket it takes a few days. Because the ion drive needs much less fuel, the total launched mass is usually lower, which typically results in a lower overall cost. SMART-1 was a Swedish-designed European Space Agency satellite that orbited around the Moon. ...

Mission planning frequently involves adjusting and choosing the propulsion system according to the mission delta-v needs, so as to minimise the total cost of the project, including trading off greater or lesser use of fuel and launch costs of the complete vehicle.

Propulsion methods

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Propulsion methods can be classified based on their means of accelerating the reaction mass. There are also some special methods for launches, planetary arrivals, and landings. Image File history File links Broom_icon. ... Prose is writing distinguished from poetry by its greater variety of rhythm and its closer resemblance to the patterns of everyday speech. ...

Rocket engines

Main article: Rocket engine

SpaceX's Kestrel engine is tested

Most rocket engines are internal combustion heat engines (although non combusting forms exist). Rocket engines generally produce a high temperature reaction mass, as a hot gas. This is achieved by combusting a solid, liquid or gaseous fuel with an oxidiser within a combustion chamber. The extremely hot gas is then allowed to escape through a high-expansion ratio nozzle. This bell-shaped nozzle is what gives a rocket engine its characteristic shape. The effect of the nozzle is to dramatically accelerate the mass, converting most of the thermal energy into kinetic energy. Exhaust speeds as high as 10 times the speed of sound at sea level are common. 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. ... Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... The internal combustion engine is an engine in which the combustion of fuel and an oxidizer (typically air) occurs in a confined space called a combustion chamber. ... A heat engine performs the conversion of heat energy to work by exploiting the temperature gradient between a hot source and a cold sink. Heat is transferred to the sink from the source, and in this process some of the heat is converted into work. ... Diagram of a de Laval nozzle, showing approximate flow velocity increasing from green to red A de Laval nozzle (or convergent-divergent nozzle, CD nozzle or con-di nozzle) is a tube that is pinched in the middle, making an hourglass-shape. ...

Rockets emitting plasma can potentially carry out reactions inside a magnetic bottle and release the plasma via a magnetic nozzle, so that no solid matter need come in contact with the plasma. Of course, the machinery to do this is complex, but research into nuclear fusion has developed methods, some of which have been used in speculative propulsion systems. A magnetic mirror is a magnetic field configuration where the field strength changes when moving along a field line. ... This page is a candidate for speedy deletion. ... The deuterium-tritium (D-T) fusion reaction is considered the most promising for producing fusion power. ...

See rocket engine for a listing of various kinds of rocket engines using different heating methods, including chemical, electrical, solar, and nuclear. 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. ...

Electromagnetic acceleration of reaction mass

This test engine accelerates ions using electrostatic forces

Rather than relying on high temperature and fluid dynamics to accelerate the reaction mass to high speeds, there are a variety of methods that use electrostatic or electromagnetic forces to accelerate the reaction mass directly. Usually the reaction mass is a stream of ions. Such an engine very typically uses electric power, first to ionise atoms, and then uses a voltage gradient to accelerate the ions to high exhaust velocities. Ion engine in operation (from Great Images in NASA) File links The following pages link to this file: Spacecraft propulsion Ion thruster User:Patrick/w Categories: NASA images ... Ion engine in operation (from Great Images in NASA) File links The following pages link to this file: Spacecraft propulsion Ion thruster User:Patrick/w Categories: NASA images ... Fluid dynamics is the sub-discipline of fluid mechanics dealing with fluids (liquids and gases) in motion. ... Electromagnetism is the physics of the electromagnetic field: a field which exerts a force on particles that possess the property of electric charge, and is in turn affected by the presence and motion of those particles. ... This article is about the electrically charged particle. ...

For these drives, at the highest exhaust speeds energetic efficiency and thrust are all inversely proportional to exhaust velocity. Their very high exhaust velocity means they require huge amounts of energy and thus with practical power sources provide low thrust, but use hardly any fuel.

For some missions, particularly reasonably close to the Sun, solar energy may be sufficient, and has very often been used, but for others further out or at higher power, nuclear energy is necessary; engines drawing their power from a nuclear source are called nuclear electric rockets. Solar power describes a number of methods of harnessing energy from the light of the sun. ... In a nuclear electric rocket, nuclear thermal energy is changed into electrical energy that is used to power one of the electrical propulsion technologies. ...

With any current source of electrical power, chemical, nuclear or solar, the maximum amount of power that can be generated limits the amount of thrust that can be produced to a small value. Power generation adds significant mass to the spacecraft, and ultimately the weight of the power source limits the performance of the vehicle.

Current nuclear power generators are approximately half the weight of solar panels per watt of energy supplied, at terrestrial distances from the Sun. Chemical power generators are not used due to the far lower total available energy. Beamed power to the spacecraft shows some potential. However, the dissipation of waste heat from any power plant may make any propulsion system requiring a separate power source infeasible for interstellar travel.

Some electromagnetic methods:

• Ion thrusters (accelerate ions first and later neutralize the ion beam with an electron stream emitted from a cathode called a neutralizer)
  • Electrostatic ion thruster
  • Field Emission Electric Propulsion
  • Hall effect thruster
  • Colloid thruster
• Plasma thrusters (where both ions and electrons are accelerated simultaneously, no neutralizer is required)
  • Magnetoplasmadynamic thruster
  • Helicon Double Layer Thruster
  • Electrodeless plasma thruster
  • Pulsed inductive thruster
  • Variable specific impulse magnetoplasma rocket (VASIMR)
• Mass drivers (for propulsion)

An ion engine test An ion thruster is a type of spacecraft propulsion that uses beams of ions for propulsion. ... The electrostatic ion thruster is a kind of design for ion thrusters (a kind of highly-efficient low-thrust spacecraft propulsion running on electrical power). ... Field Emission Electric Propulsion (FEEP) is an advanced electrostatic propulsion concept, a form of ion thruster, that uses liquid metal (usually either cesium or indium) as a propellant. ... 2 kW Laboratory Hall Thruster in operation at the Princeton Plasma Physics Laboratory A Hall effect thruster is a type of ion thruster in which the propellant is accelerated by an electric field in a plasma discharge with a radial magnetic field. ... 20 μN colloid thruster system[1] A colloid thruster is a type of ion thruster which uses electrostatic acceleration of charged liquid droplets for propulsion. ... An MPD thruster during test firing The Magnetoplasmadynamic (MPD) thruster (MPDT) is a form of electric propulsion (a subdivision of spacecraft propulsion) which uses the Lorentz force (a force resulting from the interaction between a magnetic field and an electric current) to generate thrust. ... The Helicon Double Layer Thruster is a prototype spacecraft propulsion engine. ... The Electrodeless Plasma Thruster is a spacecraft propulsion engine. ... Pulsed inductive thrusters or PITs as they are commonly abbreviated are a form of spacecraft propulsion that uses perpendicular electric and magnetic fields to accelerate a propellant. ... VASIMR test bed The Variable specific impulse magnetoplasma rocket (VASIMR) is a hypothetical form of spacecraft propulsion that uses radio waves and magnetic fields to accelerate a propellant. ... 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. ...

Systems without reaction mass carried within the spacecraft

NASA study of a solar sail. The sail would be half a kilometer wide.

The law of conservation of momentum states that any engine which uses no reaction mass cannot move the center of mass of a spaceship (changing orientation, on the other hand, is possible). But space is not empty, especially space inside the Solar System; there are gravitation fields, magnetic fields, solar wind and solar radiation. Various propulsion methods try to take advantage of these. However, since these phenomena are diffuse in nature, corresponding propulsion structures need to be proportionately large. From http://antwrp. ... From http://antwrp. ... In physics, a conservation law states that a particular measurable property of an isolated physical system does not change as the system evolves. ... This article is about momentum in physics. ... Magnetic field lines shown by iron filings In physics, the space surrounding moving electric charges, changing electric fields and magnetic dipoles contains a magnetic field. ... The plasma in the solar wind meeting the heliopause The solar wind is a stream of charged particles (i. ...

There are several different space drives that need little or no reaction mass to function. A tether propulsion system employs a long cable with a high tensile strength to change a spacecraft's orbit, such as by interaction with a planet's magnetic field or through momentum exchange with another object.^[11] Solar sails rely on radiation pressure from electromagnetic energy, but they require a large collection surface to function effectively. The magnetic sail deflects charged particles from the solar wind with a magnetic field, thereby imparting momentum to the spacecraft. A variant is the mini-magnetospheric plasma propulsion system, which uses a small cloud of plasma held in a magnetic field to deflect the Sun's charged particles. Artists conception of satellite with a tether Tether propulsion uses long, strong strings (known as tethers) to change the orbits of spacecraft. ... 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. ... Radiation pressure is the pressure exerted upon any surface exposed to electromagnetic radiation. ... A magnetic sail or magsail is a proposed method of spacecraft propulsion. ... The plasma in the solar wind meeting the heliopause The solar wind is a stream of charged particles (i. ... Mini-magnetospheric plasma propulsion (M2P2) is a form of spacecraft propulsion, a way to make a magnetic sail. ...

For changing the orientation of a satellite or other space vehicle, conservation of angular momentum does not pose a similar constraint. Thus many satellites use momentum wheels to control their orientations. These cannot be the only system for controlling satellite orientation, as the angular momentum built up due to torques from external forces such as solar, magnetic or tidal forces eventually needs to be "bled off" using a secondary system. In physics, angular momentum intuitively measures how much the linear momentum is directed around a certain point called the origin; the moment of momentum. ... Gyroscope of the International Space Station A momentum wheel or reaction wheel is a type of flywheel used primarily by spacecraft to change their angular momentum without using fuel for rockets or other reaction devices. ...

Gravitational slingshots can also be used to carry a probe onward to other destinations. 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. ...

Launch mechanisms

An artist's conception of an electromagnetic catapult on the Moon

High thrust is of vital importance for Earth launch, thrust has to be greater than weight (see also gravity drag). Many of the propulsion methods above give a thrust/weight ratio of much less than 1, and so cannot be used for launch. Download high resolution version (1023x675, 507 KB)Lunar base concept drawing from NASA File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Download high resolution version (1023x675, 507 KB)Lunar base concept drawing from NASA File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... In astrodynamics, gravity drag is inefficiency encountered by a spacecraft thrusting while moving against a gravitational field. ...

All current spacecraft use chemical rocket engines (bipropellant or solid-fuel) for launch. Other power sources such as nuclear have been proposed, and tested, but safety, environmental and political considerations have so far curtailed their use. 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. ... The Space Shuttle is initially launched with the help of solid-fuel boosters A Solid rocket or a solid fuel rocket is a rocket with a motor that uses solid propellants (fuel/oxidizer). ...

One advantage that spacecraft have in launch is the availability of infrastructure on the ground to assist them. Proposed ground-assisted launch mechanisms include:

• Space elevator
• Orbital airship
• Space fountain
• Hypersonic skyhook
• Electromagnetic catapult (railgun, coilgun)
• Space gun (Project HARP, ram accelerator)
• Laser propulsion (Lightcraft)

A space elevator would consist of a cable anchored to the Earths surface, reaching into space. ... The orbital airship, also called the space blimp, is a proposed space transportation system that carries payloads to and from low Earth orbit. ... The space fountain concept is a proposed form of space elevator that does not require the structure to be in geosynchronous orbit, and does not rely on tensile strength for support. ... Artists conception of satellite with a tether Tether propulsion uses long, strong strings (known as Tethers) to change the orbits of spacecraft. ... 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. ... A railgun is a form of gun that converts electrical energy (rather than the more conventional chemical energy from an explosive propellant) into projectile kinetic energy. ... A coilgun (not to be confused with a railgun) is a type of cannon which uses one or more electromagnetic coils to accelerate a magnetic projectile to high velocity. ... There are various methods of space launch, one of them is to shoot something out of a gigantic gun. ... Project HARP, short for High Altitude Research Project, was a joint project of The Pentagon and the Canadian Department of National Defence created with the goal of studying ballistics of re-entry vehicles at low cost; whereas most such projects used expensive (and failure-prone) rockets, HARP used a very... A ram accelerator is a gun that utilizes ramjet compression to accelerate a projectile to extremely high speeds. ... Laser propulsion is a form of Beam-powered propulsion where the energy source is a remote (usually ground-based) laser system. ... A lightcraft is a vehicle currently under development by NASA that uses an external source of laser or maser energy to provide power for producing thrust (beam-powered propulsion). ...

Airbreathing engines for launch

Main article: Jet engine

Studies generally show that conventional air-breathing engines, such as ramjets or turbojets are basically too heavy (have too low a thrust/weight ratio) to give any significant performance improvement when installed on a launch vehicle itself. However, launch vehicles can be air launched from separate lift vehicles (e.g. B-29, Pegasus Rocket and White Knight) which do use such propulsion systems. A Pratt and Whitney turbofan engine for the F-15 Eagle is tested at Robins Air Force Base, Georgia, USA. The tunnel behind the engine muffles noise and allows exhaust to escape. ... For the fictional method of interstellar travel, see Bussard ramjet. ... A Pratt and Whitney turbofan engine for the F-15 Eagle is tested at Robins Air Force Base, Georgia, USA. The tunnel behind the engine muffles noise and allows exhaust to escape. ... A Boeing X-43 being air launched from under the wing of a B-52 Stratofortress. ... The Boeing B-29 Superfortress was a four-engine heavy bomber propeller aircraft flown by the United States Army Air Forces in World War II and other military organizations afterwards. ... Pegasus rocket on the ground Pegasus rocket attached to bottom of carrier aircraft The Pegasus rocket is a winged space booster developed by Orbital Sciences Corporation (Orbital). ... SpaceShipOne and White Knight during a captive carry test flight The Scaled Composites Model 318 White Knight is a jet-powered carrier aircraft used to launch the SpaceShipOne experimental spacecraft. ...

On the other hand, very lightweight or very high speed engines have been proposed that take advantage of the air during ascent:

• SABRE - a lightweight hydrogen fuelled turbojet with precooler^[12]
• ATREX - a lightweight hydrogen fuelled turbojet with precooler^[13]
• Liquid air cycle engine - a hydrogen fuelled jet engine that liquifies the air before burning it in a rocket engine
• Scramjet - jet engines that use supersonic combustion

Normal rocket launch vehicles fly almost vertically before rolling over at an altitude of some tens of kilometers before burning sideways for orbit; this initial vertical climb wastes propellant but is optimal as it greatly reduces airdrag. Airbreathing engines burn propellant much more efficiently and this would permit a far flatter launch trajectory, the vehicles would typically fly approximately tangentially to the earth surface until leaving the atmosphere then perform a rocket burn to bridge the final delta-v to orbital velocity. French naval officers sabre of the 19th Century From left to right: two bayonets, a short curved infantry or artillery briquet, a straight infantry officers sabre, and a carbine. ... The ATREX engine developed in Japan is an experimental precooled jet engine that works as a turbojet at low speeds and a ramjet up to mach 6. ... A liquid air cycle engine (LACE) is a spacecraft propulsion engine that attempts to gain efficiency by gathering part of its oxidizer from the atmosphere. ... X-43A with scramjet attached to the underside at Mach 7 A scramjet (supersonic combustion ramjet) is a variation of a ramjet with the key difference being that the flow in the combustor is supersonic. ... General In general physics delta-v is simply the change in velocity. ...

Planetary arrival and landing

A test version of the MARS Pathfinder airbag system

When a vehicle is to enter orbit around its destination planet, or when it is to land, it must adjust its velocity. This can be done using all the methods listed above (provided they can generate a high enough thrust), but there are a few methods that can take advantage of planetary atmospheres and/or surfaces. A test of the Mars Pathfinder airbag system; from NASA http://grin. ... A test of the Mars Pathfinder airbag system; from NASA http://grin. ...

• Aerobraking allows a spacecraft to reduce the high point of an elliptical orbit by repeated brushes with the atmosphere at the low point of the orbit. This can save a considerable amount of fuel since it takes much less delta-V to enter an elliptical orbit compared to a low circular orbit. Since the braking is done over the course of many orbits, heating is comparatively minor, and a heat shield is not required. This has been done on several Mars missions such as Mars Global Surveyor, Mars Odyssey and Mars Reconnaissance Orbiter, and at least one Venus mission, Magellan.
• Aerocapture is a much more aggressive manoeuver, converting an incoming hyperbolic orbit to an elliptical orbit in one pass. This requires a heat shield and much trickier navigation, since it must be completed in one pass through the atmosphere, and unlike aerobraking no preview of the atmosphere is possible. If the intent is to remain in orbit, then at least one more propulsive maneuver is required after aerocapture—otherwise the low point of the resulting orbit will remain in the atmosphere, resulting in eventual re-entry. Aerocapture has not yet been tried on a planetary mission, but the re-entry skip by Zond 6 and Zond 7 upon lunar return were aerocapture maneuvers, since they turned a hyperbolic orbit into an elliptical orbit. On these missions, since there was no attempt to raise the perigee after the aerocapture, the resulting orbit still intersected the atmosphere, and re-entry occurred at the next perigee.
• Parachutes can land a probe on a planet with an atmosphere, usually after the atmosphere has scrubbed off most of the velocity, using a heat shield.
• Airbags can soften the final landing.
• Lithobraking, or stopping by simply smashing into the target, is usually done by accident. However, it may be done deliberately with the probe expected to survive (see, for example, Deep Space 2). Very sturdy probes and low approach velocities are required.

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. ... The Mars Global Surveyor (MGS) was a US spacecraft developed by NASA and the Jet Propulsion Laboratory and launched November 1996. ... Artists concept of the 2001 Mars Odyssey Spacecraft 2001 Mars Odyssey is an unmanned spacecraft orbiting the planet Mars. ... NASAs Mars Reconnaissance Orbiter (MRO) is a multipurpose spacecraft designed to conduct reconnaissance and exploration of Mars from orbit. ... Magellan spacecraft at Kennedy Space Center The Magellan spacecraft carried out a mission from 1989-1994, orbiting Venus from 1990-1994. ... Aerocapture is a technique used to reduce velocity of a spacecraft, arriving at a celestial body with an hyperbolic trajectory, in order to bring it in an orbit with an eccentricity less or equal to 1. ... Skip reentry is a reentry technique involving successive skips off the atmosphere to slow the spacecraft to a reasonable speed before entering, which greatly decreases the huge amount of heat that is usually generated on faster descents. ... Zond 6 (Soyuz 7K-L1) Zond 6, a member of the Soviet Unions Zond program, was launched on a lunar flyby mission from a parent satellite (68-101B) in Earth parking orbit. ... Zond 7 (Soyuz 7K-L1) Zond 7, a member of the Soviet Unions Zond program and the only truly successful test of the Soyuz 7K-L1, was launched towards the Moon from a mother spacecraft (69-067B) on a mission of further studies of the Moon and circumlunar space... This article is about the device. ... “Reentry” redirects here. ... For the Mozilla crash reporting software previously called Airbag, see Breakpad. ... Lithobraking is the a technique of descent by an unmanned space vehicle to the surface of a terrestrial body by which the vehicle is slowed by the use of friction with the bodys surface. ... 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. ...

Proposed methods that may violate the laws of physics

Artist's conception of a warp drive design

In addition, a variety of hypothetical propulsion techniques have been considered that would require entirely new principles of physics to realize and that may not actually be possible. To date, such methods are highly speculative and include: 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 ...

• Diametric drive
• Pitch drive
• Bias drive
• Disjunction drive
• Alcubierre drive (a form of Warp drive)
• Differential sail
• Wormholes - theoretically possible, but impossible in practice with current technology
• Antigravity - requires the concept of antigravity; theoretically impossible
• Reactionless drives - breaks the law of conservation of momentum; theoretically impossible
• EmDrive - again, breaks the law of conservation of momentum; theoretically impossible
• A "hyperspace" drive based upon Heim theory

The Breakthrough Propulsion Physics Program (BPP) is a research program which was funded from 1996 through 2002 by NASA, in the hope of studying various proposals for revolutionary methods of spacecraft propulsion which would require breakthroughs in physics before they could be realized, hence the name. ... The Breakthrough Propulsion Physics Program (BPP) is a research program which was funded from 1996 through 2002 by NASA, in the hope of studying various proposals for revolutionary methods of spacecraft propulsion which would require breakthroughs in physics before they could be realized, hence the name. ... The Breakthrough Propulsion Physics Program (BPP) is a research program which was funded from 1996 through 2002 by NASA, in the hope of studying various proposals for revolutionary methods of spacecraft propulsion which would require breakthroughs in physics before they could be realized, hence the name. ... The Breakthrough Propulsion Physics Program (BPP) is a research program which was funded from 1996 through 2002 by NASA, in the hope of studying various proposals for revolutionary methods of spacecraft propulsion which would require breakthroughs in physics before they could be realized, hence the name. ... This article is about the Alcubierre metric. ... For other uses, see Warp drive (disambiguation). ... The Breakthrough Propulsion Physics Program (BPP) is a research program which was funded from 1996 through 2002 by NASA, in the hope of studying various proposals for revolutionary methods of spacecraft propulsion which would require breakthroughs in physics before they could be realized, hence the name. ... For other uses, see Wormhole (disambiguation). ... AntiGravity is a group of New York gymnasts/performance artists. ... A reactionless drive or reactionless thruster (sometimes even reactionless engine) is a hypothetical form of thrust that does not require any outside force to move. ... In physics, a conservation law states that a particular measurable property of an isolated physical system does not change as the system evolves. ... New Scientist. ... This article may be too technical for most readers to understand. ...

Table of methods and their specific impulse

Below is a summary of some of the more popular, proven technologies, followed by increasingly speculative methods.

Four numbers are shown. The first is the effective exhaust velocity: the equivalent speed that the propellant leaves the vehicle. This is not necessarily the most important characteristic of the propulsion method, thrust and power consumption and other factors can be, however: Specific impulse (usually abbreviated Isp) is a way to describe the efficiency of rocket and jet engines. ...

• if the delta-v is much more than the exhaust velocity, then exorbitant amounts of fuel are necessary (see the section on calculations, above)
• if it is much more than the delta-v, then, proportionally more energy is needed; if the power is limited, as with solar energy, this means that the journey takes a proportionally longer time

The second and third are the typical amounts of thrust and the typical burn times of the method. Outside a gravitational potential small amounts of thrust applied over a long period will give the same effect as large amounts of thrust over a short period. (This result does not apply when the object is significantly influenced by gravity.)

The fourth is the maximum delta-v this technique can give (without staging). For rocket-like propulsion systems this is a function of mass fraction and exhaust velocity. Mass fraction for rocket-like systems is usually limited by propulsion system weight and tankage weight. For a system to achieve this limit, typically the payload may need to be a negligible percentage of the vehicle, and so the practical limit on some systems can be much lower.

Specific impulse (usually abbreviated Isp) is a way to describe the efficiency of rocket and jet engines. ... Thrust is a reaction force described quantitatively by Newtons Second and Third Laws. ... The Space Shuttle is initially launched with the help of solid-fuel boosters A Solid rocket or a solid fuel rocket is a rocket with a motor that uses solid propellants (fuel/oxidizer). ... A hybrid rocket propulsion system comprises propellants of two different states of matter, the most common configuration being a rocket engine composed of a solid propellant lining a combustion chamber into which a liquid or gaseous propellant is injected so as to undergo a strong exothermic reaction to produce hot... A monopropellant rocket (or monoprop rocket) is a rocket that uses a single chemical as its power source and propellant. ... 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. ... A Tripropellant rocket is a form of spacecraft propulsion that uses two fuels and one oxidizer. ... A resistojet is a way of propulsion that provides thrust by heating a (typically non-reactive) fluid. ... Arcjets are a form of electric propulsion for spacecraft, whereby an electrical discharge (arc) is created in a flow of propellant (typically hydrazine or ammonia). ... 2 kW Laboratory Hall Thruster in operation at the Princeton Plasma Physics Laboratory A Hall effect thruster is a type of ion thruster in which the propellant is accelerated by an electric field in a plasma discharge with a radial magnetic field. ... The electrostatic ion thruster is a kind of design for ion thrusters (a kind of highly-efficient low-thrust spacecraft propulsion running on electrical power). ... Field Emission Electric Propulsion (FEEP) is an advanced electrostatic propulsion concept, a form of ion thruster, that uses liquid metal (usually either cesium or indium) as a propellant. ... An MPD thruster during test firing The Magnetoplasmadynamic (MPD) thruster (MPDT) is a form of electric propulsion (a subdivision of spacecraft propulsion) which uses the Lorentz force (a force resulting from the interaction between a magnetic field and an electric current) to generate thrust. ... Pulsed plasma thrusters use an arc of electric current adjacent to a solid propellant (almost always teflon), to produce a quick and repeatable burst of impulse. ... Pulsed inductive thrusters or PITs as they are commonly abbreviated are a form of spacecraft propulsion that uses perpendicular electric and magnetic fields to accelerate a propellant. ... In a nuclear electric rocket, nuclear thermal energy is changed into electrical energy that is used to power one of the electrical propulsion technologies. ... 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. ... The astronomical unit (AU or au or a. ... Artists conception of satellite with a tether Tether propulsion uses long, strong strings (known as tethers) to change the orbits of spacecraft. ... 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. ... An artists conception of the NASA reference design for the Project Orion spacecraft powered by nuclear propulsion. ... VASIMR test bed The Variable specific impulse magnetoplasma rocket (VASIMR) is a hypothetical form of spacecraft propulsion that uses radio waves and magnetic fields to accelerate a propellant. ... Sketch of nuclear thermal rocket 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. ... The radioisotope rocket is a type of rocket engine that uses the heat generated by the decay of radioactive elements to heat a working fluid, which is then exhausted through a rocket nozzle to produce thrust. ... Air-augmented rockets (also known as rocket-ejector, ramrocket, ducted rocket, integral rocket/ramjets, or ejector ramjets) use the supersonic exhaust of some kind of rocket engine to further compress air collected by ram effect during flight to use as additional working mass, leading to greater effective thrust for any... A liquid air cycle engine (LACE) is a spacecraft propulsion engine that attempts to gain efficiency by gathering part of its oxidizer from the atmosphere. ... French naval officers sabre of the 19th Century From left to right: two bayonets, a short curved infantry or artillery briquet, a straight infantry officers sabre, and a carbine. ... Dual mode propulsion systems combine the high efficiency of bipropellant rockets with the reliability and simplicity of monopropellant rockets. ... A magnetic sail or magsail is a proposed method of spacecraft propulsion. ... Mini-magnetospheric plasma propulsion (M2P2) is a form of spacecraft propulsion, a way to make a magnetic sail. ... An artists conception of the Orion basic spacecraft, powered by nuclear pulse propulsion. ... 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. ... Gas core reactor rockets are a conceptual type of rocket that is propelled by the exhausted coolant of a gaseous fission reactor. ... A nuclear salt-water rocket is a type of nuclear thermal rocket designed by Robert Zubrin that would be fueled by water bearing dissolved salts of plutonium or U235. ... Beam-powered propulsion is a class of spacecraft propulsion mechanisms that use energy beamed to the spacecraft from a remote power plant. ... The fission sail is a type of spacecraft propulsion proposed by Robert Forward that uses fission fragments to propel a large solar sail-like craft. ... The fission-fragment rocket is a rocket engine design that directly harnesses hot nuclear fission products for thrust, as opposed to using a separate fluid as working mass. ... In a nuclear photonic rocket, a nuclear reactor would generate such high temperatures that the blackbody light from the reactor would provide thrust. ... This article does not cite any references or sources. ... A space elevator would consist of a cable anchored to the Earths surface, reaching into space. ... Antimatter catalysed nuclear pulse propulsion is a variation of nuclear pulse propulsion based upon the injection of antimatter into a mass of nuclear fuel which normally would not be useful in propulsion. ... This article does not cite any references or sources. ... Artists conception of a Bussard ramjet. ... This article is in need of attention from an expert on the subject. ...

See also

• interplanetary travel
• interstellar travel
• List of aerospace engineering topics
• specific impulse
• rocket
• rocket engine nozzles
• Tsiolkovsky rocket equation
• satellite
• Solar sail
• Magnetic sail
• Orbital mechanics

Image File history File links No higher resolution available. ... By definition, interplanetary travel is travel between bodies in a given star system; especially the solar system. ... Artists depiction of a hypothetical Wormhole Induction Propelled Spacecraft, based loosely on the 1994 warp drive paper of Miguel Alcubierre. ... This page aims to list all articles related to the specific discipline of aerospace engineering. ... Specific impulse (usually abbreviated Isp) is a way to describe the efficiency of rocket and jet engines. ... This article is about vehicles powered by rocket engines. ... Figure 1: A de Laval nozzle, showing approximate flow velocity increasing from green to red in the direction of flow The main type of rocket engine nozzles used in modern rocket engines is the de Laval nozzle which is used to expand and accelerate the combustion gases, from burning propellants... Tsiolkovskys rocket equation, named after Konstantin Tsiolkovsky who independently derived it, considers the principle of a rocket: a device that can apply an acceleration to itself (a thrust) by expelling part of its mass with high speed in the opposite direction, due to the conservation of momentum. ... For other uses, see Satellite (disambiguation). ... 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. ... This article or section should be merged with Celestial Mechanics Astrodynamics is the study and creation of orbits, especially those of artificial satellites. ...

Notes

1. ^  With things moving around in orbits and nothing staying still, the question may be quite reasonably asked, stationary relative to what? The answer is for the energy to be zero (and in the absence of gravity which complicates the issue somewhat), the exhaust must stop relative to the initial motion of the rocket before the engines were switched on. It is possible to do calculations from other reference frames, but consideration for the kinetic energy of the exhaust and propellant needs to be given. In Newtonian mechanics the initial position of the rocket is the centre of mass frame for the rocket/propellant/exhaust, and has the minimum energy of any frame.

References

Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 211th day of the year (212th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 211th day of the year (212th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 211th day of the year (212th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 211th day of the year (212th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 211th day of the year (212th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 212th day of the year (213th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 207th day of the year (208th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 212th day of the year (213th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 214th day of the year (215th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 214th day of the year (215th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 207th day of the year (208th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 207th day of the year (208th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 207th day of the year (208th in leap years) in the Gregorian calendar. ...

External links

• NASA Beginner's Guide to Propulsion
• NASA Breakthrough Propulsion Physics project
• Rocket Propulsion
• Journal of Advanced Theoretical Propulsion
• Different Rockets
• Earth-to-Orbit Transportation Bibliography
• Spaceflight Propulsion - a detailed survey by Greg Goebel, in the public domain
• Rocket motors on howstuffworks.com