Plasma propulsion engine

An early plasma propulsion engine from the Lewis Research Center in Cleveland, Ohio in 1961
A plasma thruster during test firing
Artist rendition of VASIMR plasma engine

A plasma propulsion engine is a type of electric propulsion that generates thrust from a quasi-neutral plasma. This is in contrast to ion thruster engines, which generate thrust through extracting an ion current from plasma source, which is then accelerated to high velocities using grids/anodes. These exist in many forms (see electric propulsion). Plasma thrusters do not typically use high voltage grids or anodes/ cathodes to accelerate the charged particles in the plasma, but rather uses currents and potentials which are generated internally in the plasma to accelerate the plasma ions. While this results in a lower exhaust velocities by virtue of the lack of high accelerating voltages, this type of thruster has a number of interesting advantages. The lack of high voltage grids of anodes removes a possible limiting element as a result of grid ion erosion. The plasma exhaust is 'quasi-neutral', which means that ion and electrons exist in equal number, which allows simply ion-electron recombination in the exhaust to neutralise the exhaust plume, removing the need for an electron gun (hollow cathode). This type of thruster often generates the source plasma using radio frequency or microwave energy, using an external antenna. This fact, combined with the absence of hollow cathodes (which are very sensitive to all but the few noble gases) allows the intriguing possibility of being able to use this type of thruster on a huge range of propellants, from argon, to carbon dioxide, air mixtures to astronaut urine.[1]

Plasma engines are better suited for long-distance interplanetary space travel missions.[2]

In recent years, many agencies have developed several forms of plasma-fueled engines, including the European Space Agency, Iranian Space Agency and Australian National University, which have co-developed a more advanced type described as a double layer thruster.[3][4] However, this form of plasma engine is only one of many types.

Advantages

Plasma engines have a much higher specific impulse (I) value than most other types of rocket technology. The VASIMR engine is capable of reaching an impulse value of over 12000, while hall thrusters can reach about 2000. This is much higher than the chemical bipropellant fuel that is sometimes used that can reach a specific impulse of 450.[5] With high impulse, these rockets are capable of reaching relatively high speeds. Ex-astronaut Franklin Chang-Diaz claims his VASIMR engine could send a payload to Mars in as little as 39 days while reaching a max velocity of 34 miles per second.[6] The trend is the same for other plasma rockets.

Certain plasma thrusters, such as the mini-helicon, are hailed for their simple design and ease of use. With cheap fuel (a large number of gases or combinations of gases can be used as fuel), and relatively simple theory of performance, plasma rockets can be used more than once, and be easily built. Plasma rockets also do not have to spend all of their fuel all at once unlike traditional chemical rockets. This allows plasma rockets to change speed in flight, and even change direction midflight as well.[7]

Drawbacks

For some plasma thruster technologies, such as Berkant Goksel's tiny plasma thruster, one of the largest problems is generating enough electricity to turn gases into plasma.[8] This same problem plagues Diaz's VASIMR thruster. Diaz's device would need so much electricity, that any vehicle that uses a VASIMR engine would also need several nuclear reactors in order to generate enough power. Not only would the reactors add mass to the payload, this has caused concern by some who fear the possible fallout caused by an explosion of the reactor.[9] Because of this possibility, NASA has previously stopped research in nuclear reactors that could be sent up into space.

Another common issue plasma rockets have run into is the possibility of the rocket breaking itself. Over time, the plasma these rockets produce will damage the walls of the device ultimately causing it to break. This means that on a mission to Mars, it is possible that the rocket will destroy itself.[10]

Lastly, due to their low thrust, plasma engines are not suitable for sending large payloads into space. On average, these rockets provide about 2 pounds of thrust maximum.[5] This is a problem since in order to be financially efficient, heavy payloads need to be sent up every time a mission is scheduled. While plasma engines could take over once in space, chemical rockets would be needed to launch the vehicle.

Plasma engines in use

While most plasma engines are still confined to the laboratory, some have seen active flight time and use on missions. As of 2011, NASA, partnered with aerospace company Busek, launched the first hall thruster into space aboard the Tacsat-2 satellite. The thruster was the satellite's main propulsion system. Since then, the company has launched another hall effect thruster in 2011.[11] As time progresses, more plasma thrusters are likely to see flight time on objects that have left Earth's surface.

Engine types
Helicon double layer thrusters

Helicon thrusters use low-frequency electromagnetic waves (Helicon waves) that exist inside plasma when exposed to a magnetic field. An R-F antennae that wraps around a chamber of gas is used to create the waves and excite the gas. Once the energy provided by the antennae couples with the gas a plasma is created. Once the plasma is formed, the plasma is accelerated out of the engine using a magnetic field of ideal topology. Mini-helicon thrusters, invented by Oleg Batishcev, are small simple thrusters ideal for small maneuvers in space. These thrusters are capable of running off of many different fuels making these simple rockets ideal for long term missions. Its simple design also makes it versatile in that it can be made out of simple materials such as a glass soda bottle. [12]

Magnetoplasmadynamic thrusters

Magnetoplasmadynamic thrusters (MPD) use the Lorentz force (a force resulting from the interaction between a magnetic field and an electric current) to generate thrust—the electric charge flowing through the plasma in the presence of a magnetic field causing the plasma to accelerate due to the generated magnetic force. The Lorentz force is also crucial to the operation of most pulsed plasma thruster

Pulsed inductive thrusters

Pulsed inductive thrusters (PIT) also use the Lorentz force to generate thrust, but unlike the magnetoplasmadynamic thruster, they do not use any electrode, preventing their erosion. Ionization and electric currents in the plasma are induced by a rapidly varying magnetic field.

Electrodeless plasma thrusters

Electrodeless plasma thrusters use the ponderomotive force which acts on any plasma or charged particle when under the influence of a strong electromagnetic energy density gradient to accelerate both electrons and ions of the plasma in the same direction, thereby able to operate without neutralizer.

SPT
Hall effect thrusters

Hall effect thrusters (also called stationary plasma thrusters SPT) combine a strong localized static magnetic field perpendicular to the electric field created between an upstream anode and a downstream cathode called neutralizer, to create a "virtual cathode" (area of high electron density) at the exit of the device. This virtual cathode then attracts the ions formed inside the thruster closer to the anode. Finally the accelerated ion beam is neutralized by some of the electrons emitted by the neutralizer. Serial production of Hall effect thruster started in Soviet Union in the 1970s. One of the early variants, SPT-100 is now produced under license by European Snecma Moteurs under the name PPS-1350. Similarly BPT-4000 and PPS-5000 are closely related to SPT-140. SPT-290 has a thrust of 1.5N, 5-30 kW power and specific impulse 30 km/s, efficiency 65% and weight 23 kg.

VASIMR
VASIMR

VASIMR, short for Variable Specific Impulse Magnetoplasma Rocket, uses radio waves to ionize a propellant into a plasma. Then, a magnetic field accelerates the plasma from the rocket engine, generating thrust. The VASIMR is being developed by Ad Astra Rocket Company, headquartered in Houston, TX. A Nova Scotia, Canada-based company Nautel, is producing the 200 kW RF generators required to ionize the propellant. Some component tests and "Plasma Shoot" experiments are performed in a Liberia, Costa Rica laboratory. This project is led by former NASA astronaut Dr. Franklin Chang-Díaz (CRC-USA).

The Costa Rican Aerospace Alliance has announced development of an exterior support for the VASIMR to be fitted outside the International Space Station. This phase of the plan to test the VASIMR in space is expected to be conducted in 2016. A projected 200 megawatt VASIMR engine could reduce the time to travel from Earth to Jupiter or Saturn from six years to fourteen months, and from Earth to Mars from 6 months to 39 days.[13]

See also

Magnetic sail

References
  1. "Australian National University develops helicon plasma thruster". Dvice. January 2010. Retrieved 8 June 2012.
  2. "N.S. company helps build plasma rocket". cbcnews. January 2010. Retrieved 24 July 2012.
  3. "Plasma engine passes initial test". BBC News. 14 December 2005.
  4. "Plasma jet engines that could take you from the ground to space". New Scientist. Retrieved 2017-07-29.
  5. "Space Travel Aided by Plasma Thrusters: Past, Present and Future | DSIAC". www.dsiac.org. Retrieved 2017-07-29.
  6. "Antimatter to ion drives: NASA's plans for deep space propulsion". Cosmos Magazine. Retrieved 2017-07-29.
  7. "Rocket Aims For Cheaper Nudges In Space; Plasma Thruster Is Small, Runs On Inexpensive Gases". ScienceDaily. Retrieved 2017-07-29.
  8. "Plasma jet engines that could take you from the ground to space". New Scientist. Retrieved 2017-07-29.
  9. "The 123,000 MPH Plasma Engine That Could Finally Take Astronauts To Mars". Popular Science. Retrieved 2017-07-29.
  10. "Traveling to Mars with immortal plasma rockets". Retrieved 2017-07-29.
  11. "TacSat-2". www.busek.com. Retrieved 2017-07-29.
  12. "Rocket Aims For Cheaper Nudges In Space; Plasma Thruster Is Small, Runs On Inexpensive Gases". ScienceDaily. Retrieved 2017-07-29.
  13. "TacSat-2". www.busek.com. Retrieved 2017-07-29.
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Plasma propulsion engine

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Plasma propulsion engine

An early plasma propulsion engine from the Lewis Research Center in Cleveland, Ohio in 1961 A plasma thruster during test firing Artist rendition of VASIMR plasma engine A plasma propulsion engine is a type of electric propulsion that generates thrust from a quasi-neutral plasma. This is in contrast to ion thruster engines, which generate thrust through extracting an ion current from plasma source, which is then accelerated to high velocities using grids/anodes. These exist in many forms (see electric propulsion). Plasma thrusters do not typically use high voltage grids or anodes/ cathodes to accelerate the charged particles in the plasma, but rather uses currents and potentials which are generated internally in the plasma to accelerate the plasma ions. While this results in a lower exhaust velocities by virtue of the lack of high accelerating voltages, this type of thruster has a number of interesting advantages. The lack of high voltage grids of anodes removes a possible limiting element as a result ...more...

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Ion thruster

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Ion thruster

NASA's 2.3 kW NSTAR ion thruster for the Deep Space 1 spacecraft during a hot fire test at the Jet Propulsion Laboratory An ion thruster or ion drive is a form of electric propulsion used for spacecraft propulsion. It creates thrust by accelerating positive ions with electricity. The term refers strictly to gridded electrostatic ion thrusters, and is often incorrectly loosely applied to all electric propulsion systems including electromagnetic plasma thrusters. An ion thruster ionizes a neutral gas by extracting some electrons out of atoms, creating a cloud of positive ions. These thrusters rely mainly on electrostatics as ions are accelerated by the Coulomb force along an electric field. Temporarily stored electrons are finally reinjected by a neutralizer in the cloud of ions after it has passed through the electrostatic grid, so the gas becomes neutral again and can freely disperse in space without any further electrical interaction with the thruster. Electromagnetic thrusters on the contrary use the Lore ...more...

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Jet propulsion

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Jet propulsion

Jet propulsion is the propulsion of an object in one direction, produced by ejecting a jet of fluid in the opposite direction. By Newton's third law, the moving body is propelled in the opposite direction to the jet. Reaction engines operating on the principle of jet propulsion include the jet engine used for aircraft propulsion, the pump-jet used for marine propulsion, and the rocket engine and plasma thruster used for spacecraft propulsion. Biological systems include the propulsion mechanisms of certain marine animals such as cephalopods, sea hares, arthropods, and fish. Physics Jet propulsion is produced by some reaction engines or animals when thrust is generated by a fast moving jet of fluid in accordance with Newton's laws of motion. It is most effective when the Reynolds number is high—that is, the object being propelled is relatively large and passing through a low-viscosity medium.[1] In biology, the most efficient jets are pulsed, rather than continuous,[2] at least when the Reynolds number is gr ...more...

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Electrically powered spacecraft propulsion

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Electrically powered spacecraft propulsion

6 kW Hall thruster in operation at the NASA Jet Propulsion Laboratory An electrically-powered spacecraft propulsion system uses electrical energy to change the velocity of a spacecraft. Most of these kinds of spacecraft propulsion systems work by electrically expelling propellant (reaction mass) at high speed, but electrodynamic tethers work by interacting with a planet's magnetic field.[1] Electric thrusters typically use much less propellant than chemical rockets because they have a higher exhaust speed (operate at a higher specific impulse) than chemical rockets.[2] Due to limited electric power the thrust is much weaker compared to chemical rockets, but electric propulsion can provide a small thrust for a long time.[3] Electric propulsion can achieve high speeds over long periods and thus can work better than chemical rockets for some deep space missions.[2] Electric propulsion is now a mature and widely used technology on spacecraft. Russian satellites have used electric propulsion for decades[4] and ...more...

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Nuclear pulse propulsion

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Nuclear pulse propulsion

An artist's conception of the Project Orion "basic" spacecraft, powered by nuclear pulse propulsion. Nuclear pulse propulsion or external pulsed plasma propulsion, is a hypothetical method of spacecraft propulsion that uses nuclear explosions for thrust.[1] It was first developed as Project Orion by DARPA, after a suggestion by Stanislaw Ulam in 1947.[2] Newer designs using inertial confinement fusion have been the baseline for most post-Orion designs, including Project Daedalus and Project Longshot. Project Orion A nuclear pulse propulsion unit. The explosive charge ablatively vaporizes the propellant, propelling it away from the charge, and simultaneously creating a plasma out of the propellant. The propellant then goes on to impact the pusher plate at the bottom of the Orion spacecraft, imparting a pulse of 'pushing' energy. Project Orion was the first serious attempt to design a nuclear pulse rocket. The design effort was carried out at General Atomics in the late 1950s and early 1960s. The idea of ...more...

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Pulsed plasma thruster

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Pulsed plasma thruster

A pulsed plasma thruster (PPT), also known as a plasma jet engine, is a form of electric spacecraft propulsion.[1] PPTs are generally considered the simplest form of electric spacecraft propulsion and were the first form of electric propulsion to be flown in space, having flown on two Soviet probes (Zond 2 and Zond 3) starting in 1964.[2] PPTs are generally flown on spacecraft with a surplus of electricity from abundantly available solar energy. Operation Schematic layout of a Pulsed Plasma Thruster Most PPTs use a solid material (normally PTFE, more commonly known as Teflon) for propellant, although very few use liquid or gaseous propellants. The first stage in PPT operation involves an arc of electricity passing through the fuel, causing ablation and sublimation of the fuel. The heat generated by this arc causes the resultant gas to turn into plasma, thereby creating a charged gas cloud. Due to the force of the ablation, the plasma is propelled at low speed between two charged plates (an anode and c ...more...

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Magnetohydrodynamic drive

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Magnetohydrodynamic drive

Yamato 1 on display in Kobe, Japan. The first working full-scale MHD ship. A magnetohydrodynamic drive or MHD accelerator is a method for propelling vehicles using only electric and magnetic fields with no moving parts, accelerating an electrically conductive propellant (liquid or gas) with magnetohydrodynamics. The fluid is directed to the rear and as a reaction, the vehicle accelerates forward.[1][2][3] First studies in the field of marine propulsion date back to the early 1960s.[4][5][6][7][8][9][10][11][12][13] Few large-scale working prototypes have been built, as marine MHD propulsion remains impractical due to its low efficiency, limited by the low electrical conductivity of seawater. Increasing current density is limited by Joule heating and water electrolysis in the vicinity of electrodes, and increasing the magnetic field strength is limited by the cost, size and weight (as well as technological limitations) of electromagnets and the power available to feed them.[14][15] Stronger technical limit ...more...

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Variable Specific Impulse Magnetoplasma Rocket

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Variable Specific Impulse Magnetoplasma Rocket

Artist's impression of multi-megawatt VASIMR spacecraft The Variable Specific Impulse Magnetoplasma Rocket (VASIMR) is an electromagnetic thruster under development for possible use in spacecraft propulsion. It uses radio waves to ionize and heat a propellant. Then a magnetic field accelerates the resulting plasma to generate thrust (plasma propulsion engine). It is one of several types of spacecraft electric propulsion systems. The VASIMR method for heating plasma was originally developed from nuclear fusion research. It is intended to bridge the gap between high-thrust, low-specific impulse and low-thrust, high-specific impulse systems, and is capable of functioning in either mode. Former NASA astronaut Franklin Chang Díaz created the VASIMR concept and has been developing it since 1977.[1] VASIMRs units for development and test are assembled by Ad Astra Rocket Company in Costa Rica.[2] Design and operation VASIMR schematic VASIMR, sometimes referred to as the Electro-thermal Plasma Thruster or Ele ...more...

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Plasma railgun

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Plasma railgun

A plasma railgun is a linear accelerator which, like a projectile railgun, uses two long parallel electrodes to accelerate a "sliding short" armature. However, in a plasma railgun, the armature and ejected projectile consists of plasma, or hot, ionized, gas-like particles, instead of a solid slug of material. Scientific plasma railguns are typically operated in vacuum and not at air pressure. They are of value because they produce muzzle velocities of up to several hundreds of kilometers per second. Because of this, these devices have applications in magnetic confinement fusion (MCF), magneto-inertial fusion (MIF), High Energy Density Physics research (HEDP), laboratory astrophysics, and as a plasma propulsion engine for spacecraft. Theory Plasma railguns appear in two principle topologies, linear and coaxial. Linear railguns consist of two flat plate electrodes separated by insulating spacers and accelerate sheet armatures. Coaxial railguns accelerate toroidal plasma armatures using a hollow outer conducto ...more...

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Fusion rocket

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Fusion rocket

A fusion rocket is a theoretical design for a rocket driven by fusion propulsion which could provide efficient and long-term acceleration in space without the need to carry a large fuel supply. The design relies on the development of fusion power technology beyond current capabilities, and the construction of rockets much larger and more complex than any current spacecraft. A smaller and lighter fusion reactor might be possible in the future when more sophisticated methods have been devised to control magnetic confinement and prevent plasma instabilities. Inertial fusion could provide a lighter and more compact alternative, as might a fusion engine[1] based on an FRC. For space flight, the main advantage of fusion would be the very high specific impulse, and the main disadvantage the (likely) large mass of the reactor. However, a fusion rocket may produce less radiation than a fission rocket, reducing the mass needed for shielding. The surest way of building a fusion rocket with current technology is to use ...more...

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Spacecraft propulsion

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Spacecraft propulsion

A remote camera captures a close-up view of a Space Shuttle Main Engine during a test firing at the John C. Stennis Space Center in Hancock County, Mississippi. Spacecraft propulsion is any method used to accelerate 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 forcing 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. 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 thrusters (often monopropellant rockets) or resistojet rockets for orbital station-keeping and some use momentum wheels for attitude control. Soviet bloc satellites have used electric propulsi ...more...

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Electrodeless plasma thruster

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Electrodeless plasma thruster

The electrodeless plasma thruster is a spacecraft propulsion engine commercialized under the acronym "E-IMPAcT" for "Electrodeless-Ionization Magnetized Ponderomotive Acceleration Thruster" . It was created by Mr. Gregory Emsellem based on technology developed by French Atomic Energy Commission scientist Dr Richard Geller and Dr. Terenzio Consoli, for high speed plasma beam production. The electrodeless plasma thruster is currently being developed and adapted to various spacecraft propulsion needs by The Elwing Company. Operating principle Propellant is injected at the upstream side of the thruster body. In cases where the propellant used is not gaseous (e.g., alkali metals) at the local temperature, the propellant must be vaporized.[1] Gaseous propellant is ionized by one of the following methods: bombarding the propellant with electrons emitted by a hot cathode or by an electron gun. a steady state electrical discharge between two electrodes. applying an alternating electric field either via a cap ...more...

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Laser propulsion

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Laser propulsion

Laser propulsion is a form of beam-powered propulsion where the energy source is a remote (usually ground-based) laser system and separate from the reaction mass. This form of propulsion differs from a conventional chemical rocket where both energy and reaction mass come from the solid or liquid propellants carried on board the vehicle. A laser launch Heat Exchanger Thruster system History The basic concepts underlying a photon-propelled "sail" propulsion system were developed by Eugene Sanger and the Hungarian physicist György Marx. Propulsion concepts using laser-energized rockets were developed by Arthur Kantrowitz and Wolfgang Moekel in the 1970s.[1] An exposition of Kantrowitz's laser propulsion ideas was published in 1988.[2] Laser propulsion systems may transfer momentum to a spacecraft in two different ways. The first way uses photon radiation pressure to drive momentum transfer and is the principle behind solar sails and laser sails. The second method uses the laser to help expel mass from the ...more...

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Plasma (physics)

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Plasma (physics)

Plasma (from Ancient Greek πλάσμα​, meaning 'moldable substance'[1]) is one of the four fundamental states of matter, and was first described by chemist Irving Langmuir[2] in the 1920s.[3] Unlike the other three states, solid, liquid, and gas, plasma does not exist freely on the Earth's surface under normal conditions. Plasma can be artificially generated by heating or subjecting a neutral gas to a strong electromagnetic field to the point an ionised gaseous substance becomes increasingly electrically conductive, and long-range electromagnetic fields dominate the behaviour of the matter.[4] Plasma and ionised gases have properties and display behaviours unlike those of the other states, and the transition between them is mostly a matter of nomenclature[2] and subject to interpretation.[5] Based on the surrounding environmental temperature and density, partially ionised or fully ionised forms of plasma may be produced. Neon signs and lightning are examples of partially ionised plasma,[6] while the interior of ...more...

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Pulsed inductive thruster

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Pulsed inductive thruster

Cross-section diagram of a Pulsed Inductive Thruster. [1] The gas is puffed inward through a central nozzle, towards the flat electromagnetic coil where it is ionized. [2] The plasma (pink) is then accelerated to the rear by the Lorentz force. Pulsed inductive thrusters (or PITs) are a form of ion thruster, used in spacecraft propulsion. It is a plasma propulsion engine using perpendicular electric and magnetic fields to accelerate a propellant with no electrode. Operation A nozzle releases a puff of gas which spreads across a flat spiraling induction coil of wire about 1 meter across. A bank of capacitors releases a pulse of high voltage electric current of tens of kilovolts lasting 10 microseconds into the coil, generating a radial magnetic field. This induces a circular electrical field in the gas, ionizing it and causing charged particles (free electrons and ions) to revolve in the opposite direction as the original pulse of current. Because the motion of this induced current flow is perpendicular to ...more...

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Beam-powered propulsion

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Beam-powered propulsion

Beam-powered propulsion, also known as directed energy propulsion, is a class of aircraft or spacecraft propulsion that uses energy beamed to the spacecraft from a remote power plant to provide energy. The beam is typically either a microwave or a laser beam and it is either pulsed or continuous. A continuous beam lends itself to thermal rockets, photonic thrusters and light sails, whereas a pulsed beam lends itself to ablative thrusters and pulse detonation engines.[1] The rule of thumb that is usually quoted is that it takes a megawatt of power beamed to a vehicle per kg of payload while it is being accelerated to permit it to reach low earth orbit.[2] Other than launching to orbit, applications for moving around the world quickly have also been proposed. Background Rockets are momentum machines; they use mass ejected from the rocket to provide momentum to the rocket. Momentum is the product of mass and velocity, so rockets generally attempt to put as much velocity into their working mass as possible, t ...more...

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Hall-effect thruster

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Hall-effect thruster

2 kW Hall thruster in operation as part of the Hall Thruster Experiment at the Princeton Plasma Physics Laboratory In spacecraft propulsion, a Hall-effect thruster (HET) is a type of ion thruster in which the propellant is accelerated by an electric field. Hall-effect thrusters trap electrons in a magnetic field and then use the electrons to ionize propellant, efficiently accelerate the ions to produce thrust, and neutralize the ions in the plume. Hall-effect thrusters (based on the discovery by Edwin Hall) are sometimes referred to as Hall thrusters or Hall-current thrusters. Hall thrusters are often regarded as a moderate specific impulse (1,600 s) space propulsion technology. The Hall-effect thruster has benefited from considerable theoretical and experimental research since the 1960s.[1] 6-kW Hall thruster in operation at the NASA Jet Propulsion Laboratory. Hall thrusters operate on a variety of propellants, the most common being xenon. Other propellants of interest include krypton, argon, bismuth, ...more...

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Nuclear propulsion

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Nuclear propulsion

Nuclear propulsion includes a wide variety of propulsion methods that fulfill the promise of the Atomic Age by using some form of nuclear reaction as their primary power source. The idea of using nuclear material for propulsion dates back to the beginning of the 20th century. In 1903 it was hypothesised that radioactive material, radium, might be a suitable fuel for engines to propel cars, boats, and planes.[1] H. G. Wells picked up this idea in his 1914 fiction work The World Set Free.[2] Pressurised water reactors are the most common reactors used in ships and submarines. The pictorial diagram shows the operating principles. Primary coolant is in orange and the secondary coolant (steam and later feedwater) is in blue. Surface ships, submarines, and torpedoes Nuclear-powered vessels are mainly military submarines, and aircraft carriers. Russia is the only country that currently has nuclear-powered civilian surface ships, most are icebreakers but one is a container ship. They use nuclear reactors as thei ...more...

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Interstellar travel

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Interstellar travel

A Bussard ramjet, one of many possible methods that could serve as propulsion of a starship. Interstellar travel is the term used for hypothetical crewed or uncrewed travel between stars or planetary systems. Interstellar travel will be much more difficult than interplanetary spaceflight; the distances between the planets in the Solar System are less than 30 astronomical units (AU)—whereas the distances between stars are typically hundreds of thousands of AU, and usually expressed in light-years. Because of the vastness of those distances, interstellar travel would require a high percentage of the speed of light; huge travel time, lasting from decades to millennia or longer; or a combination of both. The speeds required for interstellar travel in a human lifetime far exceed what current methods of spacecraft propulsion can provide. Even with a hypothetically perfectly efficient propulsion system, the kinetic energy corresponding to those speeds is enormous by today's standards of energy production. Moreover ...more...

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Artificial intelligence

Artificial intelligence (AI), sometimes called machine intelligence, is intelligence demonstrated by machines, in contrast to the natural intelligence displayed by humans and other animals. In computer science AI research is defined as the study of "intelligent agents": any device that perceives its environment and takes actions that maximize its chance of successfully achieving its goals.[1] Colloquially, the term "artificial intelligence" is applied when a machine mimics "cognitive" functions that humans associate with other human minds, such as "learning" and "problem solving".[2] The scope of AI is disputed: as machines become increasingly capable, tasks considered as requiring "intelligence" are often removed from the definition, a phenomenon known as the AI effect, leading to the quip, "AI is whatever hasn't been done yet."[3] For instance, optical character recognition is frequently excluded from "artificial intelligence", having become a routine technology.[4] Capabilities generally classified as AI ...more...

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Pulse detonation engine

A pulse detonation engine (PDE) is a type of propulsion system that uses detonation waves to combust the fuel and oxidizer mixture.[1][2] The engine is pulsed because the mixture must be renewed in the combustion chamber between each detonation wave and the next. Theoretically, a PDE can operate from subsonic up to a hypersonic flight speed of roughly Mach 5. An ideal PDE design can have a thermodynamic efficiency higher than other designs like turbojets and turbofans because a detonation wave rapidly compresses the mixture and adds heat at constant volume. Consequently, moving parts like compressor spools are not necessarily required in the engine, which could significantly reduce overall weight and cost. PDEs have been considered for propulsion since 1940.[3] Key issues for further development include fast and efficient mixing of the fuel and oxidizer, the prevention of autoignition, and integration with an inlet and nozzle. To date, no practical PDE has been put into production, but several testbed engine ...more...

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Reaction engine

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Reaction engine

A reaction engine is an engine or motor that produces thrust by expelling reaction mass, in accordance with Newton's third law of motion. This law of motion is most commonly paraphrased as: "For every action force there is an equal, but opposite, reaction force." Examples include jet engines, rocket engines, and more uncommon variations such as Hall effect thrusters, ion drives, mass drivers, and nuclear pulse propulsion. Energy use Propulsive efficiency For all reaction engines that carry on-board propellant (such as rocket engines and electric propulsion drives) some energy must go into accelerating the reaction mass. Every engine wastes some energy, but even assuming 100% efficiency, the engine needs energy amounting to 1 2 M V e 2 {\displaystyle {\begin{matrix}{\frac {1}{2}}\end{matrix}}MV_{e}^{2}} (where M is the mass of propellent expended and V e {\displaystyle V_{e}} is the exhaust velocity), which is simply the energy to accelerate the exhaust. Due to energy ...more...

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Concentrated solar power

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Concentrated solar power

2014 December - Crescent Dunes completed site. The three towers of the Ivanpah Solar Power Facility. Part of the 354 MW SEGS solar complex in northern San Bernardino County, California. Bird's eye view of Khi Solar One, South Africa Concentrated solar power (also called concentrating solar power, concentrated solar thermal, and CSP) systems generate solar power by using mirrors or lenses to concentrate a large area of sunlight, or solar thermal energy, onto a small area. Electricity is generated when the concentrated light is converted to heat, which drives a heat engine (usually a steam turbine) connected to an electrical power generator[1][2][3] or powers a thermochemical reaction (experimental as of 2013).[4][5][6] CSP had a world's total installed capacity of 4,815 MW in 2016, up from 354 MW in 2005. As of 2017, Spain accounted for almost half of the world's capacity, at 2,300 MW, making this country the world leader in CSP. United States follows with 1,740 MW. Interest is also notable in Nort ...more...

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In-space propulsion technologies

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In-space propulsion technologies

Saturn V rocket, used for the American manned lunar landing missions Proposed in-space propulsion technologies describe the propulsion technologies that could meet future space science and exploration needs. These propulsion technologies are intended to provide effective exploration of our Solar System and will permit mission designers to plan missions to "fly anytime, anywhere, and complete a host of science objectives at the destinations" and with greater reliability and safety. With a wide range of possible missions and candidate propulsion technologies, the question of which technologies are "best" for future missions is a difficult one. A portfolio of propulsion technologies should be developed to provide optimum solutions for a diverse set of missions and destinations.[1][2][3] In-space propulsion begins where the upper stage of the launch vehicle leaves off; performing the functions of primary propulsion, reaction control, station keeping, precision pointing, and orbital maneuvering. The main engines ...more...

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Teleportation

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Teleportation

Teleportation is the theoretical transfer of matter or energy from one point to another without traversing the physical space between them. It is a common subject in science fiction literature, film, video games, and television. In some situations teleporting is time travelling across space. Since 1993, energy and particle teleportation has become a hot topic in quantum mechanics. Etymology The use of the term teleport to describe the hypothetical movement of material objects between one place and another without physically traversing the distance between them has been documented as early as 1878.[1][2] American writer Charles Fort is credited with having coined the word teleportation in 1931[3][4] to describe the strange disappearances and appearances of anomalies, which he suggested may be connected. As in the earlier usage, he joined the Greek prefix tele- (meaning "distant") to the root of the Latin verb portare (meaning "to carry").[5] Fort's first formal use of the word occurred in the second chapte ...more...

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Scramjet

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Scramjet

A scramjet ("supersonic combustion ramjet") is a variant of a ramjet airbreathing jet engine in which combustion takes place in supersonic airflow. As in ramjets, a scramjet relies on high vehicle speed to compress the incoming air forcefully before combustion (hence ramjet), but whereas a ramjet decelerates the air to subsonic velocities before combustion, the airflow in a scramjet is supersonic throughout the entire engine. That allows the scramjet to operate efficiently at extremely high speeds. History Before 2000 During World War II, a tremendous amount of time and effort were put into researching high-speed jet- and rocket-powered aircraft, predominantly by the Germans. After the war, the US and UK took in several German scientists and acquired various military technologies through Operation Paperclip, including technology surrounding jet engines. The Bell X-1 attained supersonic flight in 1947 and, by the early 1960s, rapid progress towards faster aircraft suggested that operational aircraft would be ...more...

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Gridded ion thruster

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Gridded ion thruster

The gridded ion thruster is a common design for ion thrusters, a highly efficient low-thrust spacecraft propulsion running on electrical power. These designs use high-voltage grid electrodes to accelerate ions with electrostatic forces. History The ion engine was first demonstrated by German-born NASA scientist Ernst Stuhlinger,[1] and developed in practical form by Harold R. Kaufman at NASA Lewis (now Glenn) Research Center from 1957 to the early 1960s. The use of ion propulsion systems were first demonstrated in space by the NASA Lewis "Space Electric Rocket Test" (SERT) I and II.[2] These thrusters used mercury as the reaction mass. The first was SERT-1, launched July 20, 1964, which successfully proved that the technology operated as predicted in space. The second test, SERT-II, launched on February 3, 1970,[3][4] verified the operation of two mercury ion engines for thousands of running hours.[5] Despite the demonstration in the 1960s and 70s, though, they were rarely used before the late 1990s. NASA ...more...

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Thruster

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Thruster

Look up thruster or thrusters in Wiktionary, the free dictionary. Thruster may refer to: Propulsion devices A thruster is a propulsive device used by spacecraft and watercraft for station keeping, attitude control, in the reaction control system, or long-duration, low-thrust acceleration. Reaction engine Spacecraft thrusters Rear thrusters of the Space Shuttle Atlantis Rocket engine, using exothermic chemical reactions of the propellant(s) Electrohydrodynamic thruster, using ionized air (only for use in an atmosphere) Electrostatic ion thruster, using high-voltage electrodes Ion thruster, using beams of ions accelerated electrically Hall-effect thruster, a type of ion thruster Pulsed inductive thruster, a pulsed form of ion thruster Magnetoplasmadynamic thruster, electric propulsion using the Lorentz force Electrodeless plasma thruster, electric propulsion using ponderomotive force Pulsed plasma thruster, using current arced across a solid propellant RF resonant cavity thru ...more...

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Project Orion (nuclear propulsion)

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Project Orion (nuclear propulsion)

An artist's conception of the NASA reference design for the Project Orion spacecraft powered by nuclear propulsion. Project Orion was a study of a spacecraft intended to be directly propelled by a series of explosions of atomic bombs behind the craft (nuclear pulse propulsion). Early versions of this vehicle were proposed to take off from the ground with significant associated nuclear fallout; later versions were presented for use only in space. Six tests were launched. The idea of rocket propulsion by combustion of explosive substance was first proposed by Russian explosives expert Nikolai Kibalchich in 1881, and in 1891 similar ideas were developed independently by German engineer Hermann Ganswindt. General proposals of nuclear propulsion were first made by Stanislaw Ulam in 1946, and preliminary calculations were made by F. Reines and Ulam in a Los Alamos memorandum dated 1947.[1] The actual project, initiated in 1958, was led by Ted Taylor at General Atomics and physicist Freeman Dyson, who at Taylor's ...more...

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Sonic weapon

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Sonic weapon

A Long-Range Acoustic Device (LRAD) in use on the USS Blue Ridge Sonic and ultrasonic weapons (USW) are weapons of various types that use sound to injure, incapacitate, or kill an opponent. Some sonic weapons are currently in limited use or in research and development by military and police forces. Some of these weapons have been described as sonic bullets, sonic grenades, sonic mines, or sonic cannons. Some make a focused beam of sound or ultrasound; some make an area field of sound. Use and deployment An NYPD officer stands ready with the LRAD 500X at an Occupy Wall Street protest on November 17, 2011 near the city hall Extremely high-power sound waves can disrupt or destroy the eardrums of a target and cause severe pain or disorientation. This is usually sufficient to incapacitate a person. Less powerful sound waves can cause humans to experience nausea or discomfort. The use of these frequencies to incapacitate persons has occurred both in anti-citizen special operation and crowd control settin ...more...

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Plasma window

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Plasma window

The plasma window (not to be confused with a plasma shield[1]) is a technology that fills a volume of space with plasma confined by a magnetic field. With current technology, this volume is quite small and the plasma is generated as a flat plane inside a cylindrical space. Plasma is any gas that has had its atoms or molecules ionized and is a separate phase of matter. This is most commonly achieved by heating the gas to extremely high temperatures, although other methods also exist. Plasma becomes increasingly viscous at higher temperatures, to the point where other matter has trouble passing through. A plasma window's viscosity allows it to separate gas at standard atmospheric pressure from a total vacuum, and can reportedly withstand a pressure difference of up to nine atmospheres.[2] At the same time, the plasma window will allow radiation such as lasers and electron beams to pass. This property is the key to the plasma window's usefulness — the technology of the plasma window permits for radiation that ...more...

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Reactionless drive

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Reactionless drive

A reactionless drive is a device producing motion without the exhaust of a propellant. A propellantless drive is not necessarily reactionless when it constitutes an open system interacting with external fields; but a reactionless drive is a particular case of a propellantless drive as it is a closed system presumably in contradiction with the law of conservation of momentum and often considered similar to a perpetual motion machine.[1] The name comes from Newton's third law, which is usually expressed as, "for every action, there is an equal and opposite reaction." A large number of infeasible devices, such as the Dean drive, are a staple of science fiction particularly for space propulsion. Closed systems Through the years there have been numerous claims for functional reactionless drive designs using ordinary mechanics (i.e. devices not said to be based on quantum mechanics, relativity or atomic forces or effects). Two of these represent their general classes: The "Dean drive" is perhaps the best known ex ...more...

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Head transplant

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Head transplant

A head transplant is an experimental surgical operation involving the grafting of one organism's head onto the body of another; in many experiments the recipient's head was not removed but in others it has been. Experimentation in animals began in the early 1900s. As of 2018, no durable success had been achieved.[1][2] Medical challenges There are three main technical challenges. As with any organ transplant, managing the immune response to avoid transplant rejection is necessary. Also, the brain is highly dependent on continuous flow of blood to provide oxygen and nutrients and remove waste products, with damage setting in quickly at normal temperatures when blood flow is cut off. Finally, managing the nervous systems in both the body and the head is essential, in several ways. The autonomic nervous system controls essential functions like breathing and the heart beating and is governed largely by the brain stem; if the recipient body's head is removed this can no longer function. Additionally each nerve c ...more...

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Force field (fiction)

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Force field (fiction)

In speculative fiction, a force field, sometimes known as an energy shield, force shield, defence shield or deflector shield, is a barrier made of energy, plasma, or particles. It protects a person, area, or object from attacks or intrusions. This fictional technology is created as a field of energy without mass that acts as a wall, so that objects affected by the particular force relating to the field are unable to pass through the field and reach the other side. This concept has become a staple of many science-fiction works, so much that authors frequently do not even bother to explain or justify them to their readers treating them almost as established fact and attributing whatever capabilities the plot requires. There is ongoing scientific research into real force fields, primarily to protect against radiation. History The concept of a force field goes back at least as far as the 1920s, in the works of E.E. 'Doc' Smith and others; in William Hope Hodgson's The Night Land (1912) the Last Redoubt, the re ...more...

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Helicon double-layer thruster

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Helicon double-layer thruster

The helicon double-layer thruster is a prototype spacecraft propulsion engine. It was created by Australian scientist Dr Christine Charles, based on a technology invented by Professor Rod Boswell, both of the Australian National University. The design has been verified by the ESA, which is participating in its development. Theory of operation A helicon double-layer thruster (HDLT) is a type of plasma thruster, which ejects high velocity ionized gas to provide thrust to a spacecraft. In this thruster design, gas is injected into a tubular chamber (the source tube) with one open end. Radio frequency AC power (at 13.56 MHz in the prototype design) is coupled into a specially shaped antenna wrapped around the chamber. The electromagnetic wave emitted by the antenna causes the gas to break down and form a plasma. The antenna then excites a helicon wave in the plasma, which further heats the plasma. The device has a roughly constant magnetic field in the source tube (supplied by solenoids in the prototype), but ...more...

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Hype cycle

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Hype cycle

Hype cycle The hype cycle is a branded graphical presentation developed and used by the American research, advisory and information technology firm Gartner, for representing the maturity, adoption and social application of specific technologies. The hype cycle provides a graphical and conceptual presentation of the maturity of emerging technologies through five phases. An example of a hype cycle is found in Amara's law[1] coined by Roy Amara,[2] which states that We tend to overestimate the effect of a technology in the short run and underestimate the effect in the long run.[3][4] Five phases General hype cycle for technology Each hype cycle drills down into the five key phases of a technology's life cycle. No. Phase Description 1 Technology Trigger A potential technology breakthrough kicks things off. Early proof-of-concept stories and media interest trigger significant publicity. Often no usable products exist and commercial viability is unproven. 2 Peak of Inflated Expectations Early pu ...more...

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Anti-gravity

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Anti-gravity

Anti-gravity (also known as non-gravitational field) is an idea of creating a place or object that is free from the force of gravity. It does not refer to the lack of weight under gravity experienced in free fall or orbit, or to balancing the force of gravity with some other force, such as electromagnetism or aerodynamic lift. Anti-gravity is a recurring concept in science fiction, particularly in the context of spacecraft propulsion. Examples are the gravity blocking substance "Cavorite" in H. G. Wells' The First Men in the Moon and the Spindizzy machines in James Blish's Cities in Flight. In Newton's law of universal gravitation, gravity was an external force transmitted by unknown means. In the 20th century, Newton's model was replaced by general relativity where gravity is not a force but the result of the geometry of spacetime. Under general relativity, anti-gravity is impossible except under contrived circumstances.[1][2][3] Quantum physicists have postulated the existence of gravitons, massless elemen ...more...

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Caseless ammunition

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Caseless ammunition

The 4.73 × 33 mm caseless ammunition used in the Heckler & Koch G11 rifle, shown disassembled. The components are, from left to right, the solid propellant, the primer, the bullet, and a plastic cap that serves to keep the bullet centered in the propellant block. Caseless ammunition is a type of small arms ammunition that eliminates the cartridge case that typically holds the primer, propellant, and projectile together as a unit. Caseless ammunition is an attempt to reduce the weight and cost of ammunition by dispensing with the case, which is typically precision made of brass or steel, as well as to simplify the operation of repeating firearms by eliminating the need to extract and eject the empty case after firing.[1] Its acceptance has been hampered by problems with production expenses, heat sensitivity, sealing, and fragility. Its use to date has been limited to prototypes and low-powered firearms. History An early predecessor to modern caseless ammunition, Walter Hunt's Rocket Ball cartridge, w ...more...

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Aerojet Rocketdyne

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Aerojet Rocketdyne

Aerojet Rocketdyne is an American rocket and missile propulsion manufacturer. Headquartered in Sacramento, California,[1] the company is owned by Aerojet Rocketdyne Holdings. Aerojet Rocketdyne was formed in 2013 when Aerojet (then owned by GenCorp) and Pratt & Whitney Rocketdyne were merged, following the latter's acquisition by GenCorp from Pratt & Whitney.[2][3] On April 27, 2015, the name of the holding company, GenCorp, was changed from GenCorp, Inc. to Aerojet Rocketdyne Holdings, Inc.[4] Products Space Shuttle Main Engines (RS-25s) Current engines RS-25 (LH2/LOX) – Reusable main engine for the retired Space Shuttle. Remaining shuttle engines are scheduled for use on Space Launch System first stage launches after which an expendable version, RS-25E will be developed for follow-on SLS launches. RL10 (LH2/LOX) – Developed by Pratt & Whitney and currently used on both the upper stage of the Delta IV as well as the Centaur upper stage for the Atlas V. Formerly used on the Centaur u ...more...

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Thrusters (spacecraft)

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Thrusters (spacecraft)

A thruster is a propulsive device used by spacecraft for station keeping, attitude control, in the reaction control system, or long-duration, low-thrust acceleration. A vernier engine or gimbal engine is a particular case used on launch vehicles where a secondary rocket or other high thrust device is used to control the attitude of the rocket while the primary thrust engine (generally also a rocket engine) is fixed to the rocket and supplies the principal amount of thrust.[1][2][3][4][5] Some devices that are use or proposed to use as thrusters are: Cold gas thruster Electrohydrodynamic thruster, using ionized air (only for use in an atmosphere) Electrodeless plasma thruster, electric propulsion using ponderomotive force Electrostatic ion thruster, using high-voltage electrodes Hall effect thruster, a type of ion thruster Ion thruster, using beams of ions accelerated electrically Magnetoplasmadynamic thruster, electric propulsion using the Lorentz force Pulsed inductive thruster, a pulsed for ...more...

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Genetically modified food

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Genetically modified food

Genetically modified foods or GM foods, also known as genetically engineered foods, bioengineered foods, genetically modified organisms, or GMOs, are foods produced from organisms that have had changes introduced into their DNA using the methods of genetic engineering. Genetic engineering techniques allow for the introduction of new traits as well as greater control over traits than previous methods such as selective breeding and mutation breeding.[1] Commercial sale of genetically modified foods began in 1994, when Calgene first marketed its unsuccessful Flavr Savr delayed-ripening tomato.[2][3] Most food modifications have primarily focused on cash crops in high demand by farmers such as soybean, corn, canola, and cotton. Genetically modified crops have been engineered for resistance to pathogens and herbicides and for better nutrient profiles. GM livestock have been developed, although as of November 2013 none were on the market.[4] There is a scientific consensus[5][6][7][8] that currently available foo ...more...

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Jet pack

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Jet pack

Rocketbelt pilot Dan Schlund at the 2005 Melbourne Show A jet pack, rocket belt or rocket pack is a device, usually worn on the back, which uses jets of gas (or in some cases liquid) to propel the wearer through the air. The concept has been present in science fiction for almost a century and became widespread in the 1960s. Real jet packs using a variety of mechanisms have been developed, though the challenges of Earth's atmosphere, Earth's gravity, low energy density of available fuels, and the human body not being naturally adapted to fly mean that their uses are much more limited than their fictional counterparts', being principally used for stunts. A practical use for the jet pack has been in extra-vehicular activities for astronauts. Overview In the most general terms, a jet pack is a wearable device which allows the user to fly by providing thrust. With the exception of use in a microgravity environment, this thrust must be upwards so as to overcome the force of gravity, and must be enough to overco ...more...

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Antimatter rocket

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Antimatter rocket

A proposed antimatter rocket An antimatter rocket is a proposed class of rockets that use antimatter as their power source. There are several designs that attempt to accomplish this goal. The advantage to this class of rocket is that a large fraction of the rest mass of a matter/antimatter mixture may be converted to energy, allowing antimatter rockets to have a far higher energy density and specific impulse than any other proposed class of rocket. Methods Antimatter rockets can be divided into three types of application: those that directly use the products of antimatter annihilation for propulsion, those that heat a working fluid or an intermediate material which is then used for propulsion, and those that heat a working fluid or an intermediate material to generate electricity for some form of electric spacecraft propulsion system. The propulsion concepts that employ these mechanisms generally fall into four categories: solid core, gaseous core, plasma core, and beamed core configurations. The alternati ...more...

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List of spacecraft with electric propulsion

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List of spacecraft with electric propulsion

In chronological order, spacecrafts are listed equipped with electric space propulsion. This includes both cruise engines and/or thrusters for attitude and orbit control. It is not specified whether the given engine is the sole means of propulsion or whether other types of engine are also used on a spacecraft. The list does not claim to be comprehensive. Chronological overview Spacecraft with electric propulsion Spacecraft name Launch date End of life Thruster type No. Model Propellant Spacecraft customer Thruster prime Comment Program 661A Flight A 18 Dec 1962 18 Dec 1962 Ion engine 1 Cesium USAF EOS (Electro-Optical Systems, Inc.) Suborbital, no operation of on-board ion engine Kosmos 21 11 Nov 1963 11 Nov 1963 Pulsed plasma thruster PTFE Kurchatov Institute/OKB-1 Launch failure SERT 1 20 Jul 1964 20 Jul 1964 Ion engine 1 1 Mercury Cesium NASA NASA Hughes Space Electric Rocket Test, suborbital (31 min), the first demonstration of an ion engine in space - only the mercur ...more...

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Arcology

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Arcology

Concept design for the NOAH (New Orleans Arcology Habitat) proposal, designed by E. Kevin Schopfer.[1] Arcology, a portmanteau of "architecture" and "ecology",[2] is a field of creating architectural design principles for very densely populated, ecologically low-impact human habitats. The term was coined by architect Paolo Soleri, who posited that a completed arcology would provide space for a variety of residential, commercial, and agricultural facilities while minimizing individual human environmental impact. These structures have been largely hypothetical insofar as no arcology, even one envisioned by Soleri himself, has yet been built. The concept has been popularized by various science fiction writers. Authors such as Peter Hamilton in Neutronium Alchemist and Paolo Bacigalupi in The Water Knife explicitly used arcologies as part of their scenarios. They are often portrayed as self-contained or economically self-sufficient. Development An arcology is distinguished from a merely large building in t ...more...

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Fusion power

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Fusion power

The Sun, like other stars, is a natural fusion reactor, where stellar nucleosynthesis transforms lighter elements into heavier elements with the release of energy. Fusion power is a form of power generation in which energy is generated by using nuclear fusion reactions to produce heat for electricity generation. In a fusion process, two lighter atomic nuclei combine to form a heavier nucleus, and at the same time, they release energy. This is the same process that powers stars like our Sun. Devices designed to harness this energy are known as fusion reactors. Fusion processes require fuel and a highly confined environment with a high temperature and pressure, to create a plasma in which fusion can occur. In stars, the most common fuel is hydrogen, and gravity creates the high temperature and confinement needed for fusion. Fusion reactors generally use hydrogen isotopes such as deuterium and tritium, which react more easily, and create a confined plasma of millions of degrees using inertial methods (laser) o ...more...

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Nuclear thermal rocket

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Nuclear thermal rocket

Sketch of nuclear thermal rocket 1 December 1967: The first ground experimental nuclear rocket engine (XE) assembly is shown here in "cold flow" configuration, as it makes a late evening arrival at Engine Test Stand No. 1 at the Nuclear Rocket Development Station in Jackass Flats, Nevada. A nuclear thermal rocket is a proposed spacecraft propulsion technology. In a nuclear thermal rocket a working fluid, usually liquid hydrogen, is heated to a high temperature in a nuclear reactor, and then expands through a rocket nozzle to create thrust. In this kind of thermal rocket, the nuclear reactor's energy replaces the chemical energy of the propellant's reactive chemicals in a chemical rocket. The thermal heater / inert propellant paradigm as opposed to the reactive propellants of chemical rockets turns out to produce a superior effective exhaust velocity, and therefore a superior propulsive efficiency, with specific impulses on the order of twice that of chemical engines. The overall gross lift-off mass of ...more...

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Technological singularity

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Technological singularity

The technological singularity (also, simply, the singularity)[1] is the hypothesis that the invention of artificial superintelligence (ASI) will abruptly trigger runaway technological growth, resulting in unfathomable changes to human civilization.[2] According to this hypothesis, an upgradable intelligent agent (such as a computer running software-based artificial general intelligence) would enter a "runaway reaction" of self-improvement cycles, with each new and more intelligent generation appearing more and more rapidly, causing an intelligence explosion and resulting in a powerful superintelligence that would, qualitatively, far surpass all human intelligence. Stanislaw Ulam reports a discussion with John von Neumann "centered on the accelerating progress of technology and changes in the mode of human life, which gives the appearance of approaching some essential singularity in the history of the race beyond which human affairs, as we know them, could not continue".[3] Subsequent authors have echoed this ...more...

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Bioethics

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Bioethics

Bioethics is the study of the ethical issues emerging from advances in biology and medicine. It is also moral discernment as it relates to medical policy and practice. Bioethicists are concerned with the ethical questions that arise in the relationships among life sciences, biotechnology, medicine, politics, law, and philosophy. It includes the study of values ("the ethics of the ordinary") relating to primary care and other branches of medicine. Etymology The term Bioethics (Greek bios, life; ethos, behavior) was coined in 1926 by Fritz Jahr in an article about a "bioethical imperative" regarding the use of animals and plants in scientific research. [1] In 1970, the American biochemist Van Rensselaer Potter used the term to describe the relationship between the biosphere and a growing human population. Potter's work laid the foundation for global ethics, a discipline centered around the link between biology, ecology, medicine, and human values.[2][3] Purpose and scope The field of bioethics has addressed ...more...

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Hydrogen vehicle

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Hydrogen vehicle

The 2015 Toyota Mirai is one of the first hydrogen-fuel-cell vehicles to be sold commercially. The Mirai is based on the Toyota FCV concept car (shown).[1] A hydrogen vehicle is a vehicle that uses hydrogen as its onboard fuel for motive power. Hydrogen vehicles include hydrogen-fuelled space rockets, as well as automobiles and other transportation vehicles. The power plants of such vehicles convert the chemical energy of hydrogen to mechanical energy either by burning hydrogen in an internal combustion engine, or by reacting hydrogen with oxygen in a fuel cell to run electric motors. Widespread use of hydrogen for fuelling transportation is a key element of a proposed hydrogen economy.[2] As of 2016, there are 3 hydrogen cars publicly available in select markets: the Toyota Mirai, the Hyundai ix35 FCEV, and the Honda Clarity. Several other companies are working to develop hydrogen cars. As of 2014, 95% of hydrogen is made from natural gas. It can be produced using renewable sources, but that is an expensi ...more...

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H2

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