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Thrusters (spacecraft)
A thruster is a spacecraft propulsion device used for orbital station-keeping, attitude control, or long-duration, low-thrust acceleration, often as part of a reaction control system. A vernier thruster or gimbaled engine are particular cases used on launch vehicles where a secondary rocket engine 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. Some devices that are used or proposed for 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 forc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spacecraft Propulsion
Spacecraft propulsion is any method used to accelerate spacecraft and artificial satellites. In-space propulsion exclusively deals with propulsion systems used in the vacuum of space and should not be confused with space launch or atmospheric entry. Several methods of pragmatic spacecraft propulsion have been developed, each having its own drawbacks and advantages. Most satellites have simple reliable chemical thrusters (often monopropellant rockets) or resistojet rockets for orbital station-keeping, while a few use Reaction wheel, momentum wheels for attitude control. Russian and antecedent Soviet bloc satellites have used Spacecraft electric propulsion, electric propulsion for decades, and newer Western geo-orbiting spacecraft are starting to use them for north–south station-keeping and orbit raising. Interplanetary vehicles mostly use chemical rockets as well, although a few have used electric propulsion such as ion thrusters and Hall-effect thrusters. Various technologies ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetoplasmadynamic Thruster
A magnetoplasmadynamic (MPD) thruster (MPDT) is a form of electrically powered spacecraft propulsion which uses the Lorentz force (the force on a charged particle by an electromagnetic field) to generate thrust. It is sometimes referred to as a Lorentz Force Accelerator (LFA) or (mostly in Japan) MPD arcjet. Generally, a gaseous material is ionized and fed into an acceleration chamber, where the magnetic and electric fields are created using a power source. The particles are then propelled by the Lorentz force resulting from the interaction between the current flowing through the plasma and the magnetic field (which is either externally applied or induced by the current) out through the exhaust chamber. Unlike chemical propulsion, there is no combustion of fuel. As with other electric propulsion variations, both specific impulse and thrust increase with power input, while thrust per watt drops. There are two main types of MPD thrusters, applied-field and self-field. Applied-field t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Collins English Dictionary
The ''Collins English Dictionary'' is a printed and online dictionary of English. It is published by HarperCollins in Glasgow. It was first published in 1979. Corpus The dictionary uses language research based on the Collins Corpus, which is continually updated and has over 20 billion words. Editions * The current edition is the 14th; it was published on 31 August 2023, with more than 732,000 words, meanings, and phrases (not 730,000 headwords) and 9,500 place names and 7,300 biographies. A newer edition of the 14th edition was published 7 May 2024. * The previous edition was the 13th edition, which was published in November 2018. * A special "30th Anniversary" 10th edition was published in 2010. * Earlier editions were published once every 3 or 4 years. History The 1979 edition of the dictionary, with Patrick Hanks as editor and Laurence Urdang as editorial director, was the first British English dictionary to be typeset from the output from a computer database in a specif ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transfer Orbit
Orbits Astrodynamics In orbital mechanics, a transfer orbit is an intermediate elliptical orbit that is used to move a spacecraft in an orbital maneuver from one circular, or largely circular, orbit to another. There are several types of transfer orbits, which vary in their energy efficiency and speed of transfer. These include: * Hohmann transfer orbit, an elliptical orbit used to transfer a spacecraft between two circular orbits of different altitudes in the same plane * Bi-elliptic transfer, a slower method of transfer, but one that may be more efficient than a Hohmann transfer orbit * Geostationary transfer orbit or geosynchronous transfer orbit is usually also a Hohmann transfer orbit * ''Lunar transfer orbit'' is an orbit that touches Low Earth orbit and a lunar orbit In astronomy and spaceflight, a lunar orbit (also known as a selenocentric orbit) is an orbit by an object around Earth's Moon. In general these orbits are not circular. When farthest from the Moon (at ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orbit Insertion
In spaceflight an orbit insertion is an orbital maneuver which adjusts a spacecraft’s trajectory, allowing entry into an orbit around a planet, moon, or other celestial body, becoming an artificial satellite. An orbiter is a spacecraft designed for orbital insertion. An orbit insertion maneuver involves either deceleration from a speed in excess of the respective body's escape velocity, or acceleration to it from a lower speed. When the result is a transfer orbit, e.g. a ''descent orbit insertion,'' the maneuver is an orbit injection. Orbit types Orbits are periodic or quasi-periodic trajectories, usually around a central celestial body like the Earth or the Sun. They may also be trajectories around Lagrange point locations in a multi-body system like the Earth–Moon system. (For example, NASA used a halo orbit for the CAPSTONE mission.) Low orbits Low orbits are trajectories deep within the 'gravitational well' of a central body. Examples include low Earth orbit and lo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solid-fuel Rocket
A solid-propellant rocket or solid rocket is a rocket with a rocket engine that uses Rocket propellant#Solid chemical propellants, solid propellants (fuel/oxidizer). The earliest rockets were solid-fuel rockets powered by gunpowder. The inception of gunpowder rockets in warfare can be credited to the ancient Chinese, and in the 13th century, the Mongols played a pivotal role in facilitating their westward adoption. All rockets used some form of solid or powdered propellant until the 20th century, when liquid-propellant rockets offered more efficient and controllable alternatives. Because of their simplicity and reliability, solid rockets are still used today in military armaments worldwide, model rockets, solid rocket boosters and on larger applications. Since solid-fuel rockets can remain in storage for an extended period without much propellant degradation, and since they almost always launch reliably, they have been frequently used in military applications such as missiles. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Apogee Kick Motor
An apogee kick motor (AKM) is a rocket motor that is regularly employed on artificial satellites to provide the final impulse to change the trajectory from the transfer orbit into its final orbit (most commonly circular). For a satellite launched from the Earth, the rocket firing is done at the highest point of the transfer orbit, known as the apogee. An apogee kick motor is used, for example, for satellites launched into a geostationary orbit. As the vast majority of geostationary satellite launches are carried out from spaceports at a significant distance away from Earth's equator, the carrier rocket often only launches the satellite into an orbit with a non-zero inclination approximately equal to the latitude of the launch site. This orbit is commonly known as a "geostationary transfer orbit" or a "geosynchronous transfer orbit". The satellite must then provide thrust to bring forth the needed delta v to reach a geostationary orbit. This is typically done with a fixed onbo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geostationary Orbit
A geostationary orbit, also referred to as a geosynchronous equatorial orbit''Geostationary orbit'' and ''Geosynchronous (equatorial) orbit'' are used somewhat interchangeably in sources. (GEO), is a circular orbit, circular geosynchronous orbit in altitude above Earth's equator, in radius from Earth's center, and following the retrograde and prograde motion, direction of Earth's rotation. An object in such an orbit has an orbital period equal to Earth's rotational period, one sidereal time, sidereal day, and so to ground observers it appears motionless, in a fixed position in the sky. The concept of a geostationary orbit was popularised by the science fiction writer Arthur C. Clarke in the 1940s as a way to revolutionise telecommunications, and the first satellite to be placed in this kind of orbit was launched in 1963. Communications satellites are often placed in a geostationary orbit so that Earth-based satellite dish, satellite antennas do not have to rotate to track t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Liquid-propellant Rocket
A liquid-propellant rocket or liquid rocket uses a rocket engine burning liquid rocket propellant, liquid propellants. (Alternate approaches use gaseous or Solid-propellant rocket , solid propellants.) Liquids are desirable propellants because they have reasonably high density and their combustion products have high Specific impulse, specific impulse (''I''sp). This allows the volume of the propellant tanks to be relatively low. Types Liquid rockets can be monopropellant rockets using a single type of propellant, or bipropellant rockets using two types of propellant. Tripropellant rockets using three types of propellant are rare. Liquid oxidizer propellants are also used in hybrid rockets, with some of the advantages of a solid rocket. Bipropellant liquid rockets use a liquid fuel such as liquid hydrogen or RP-1, and a liquid oxidizer such as liquid oxygen. The engine may be a cryogenic rocket engine, where the fuel and oxidizer, such as hydrogen and oxygen, are gases which hav ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RF Resonant Cavity Thruster
The EmDrive is a controversial device first proposed in 2001, purported by its inventors to be a reactionless drive. While no mechanism for operation was proposed, this would violate the law of Momentum#Conservation, conservation of momentum and other laws of physics. The concept has at times been referred to as a resonant cavity thruster. The idea is generally considered by physicists to be pseudoscience. Neither person who claims to have invented it committed to details about it beyond showing prototypes they have built. While the lack of a published design or mechanism makes it hard to say whether a given object is an example of an EmDrive, over the years prototypes based on its public descriptions have been constructed and tested. In 2016, Harold G. White, Harold White's group at NASA observed a small apparent thrust from one such test, however subsequent studies suggested this was a measurement error caused by thermal gradients. In 2018 and 2021, Martin Tajmar's group a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
