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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.
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 are sometimes referred to as Hall thrusters or Hall-current thrusters. Hall-effect thrusters use a magnetic field to limit the electrons' axial motion and then use them to ionize propellant, efficiently accelerate the ions to produce thrust, and neutralize the ions in the plume. The Hall-effect thruster is classed as a moderate specific impulse space propulsion technology and has benefited from considerable theoretical and experimental research since the 1960s.
An ion thruster, ion drive, or ion engine is a form of electric propulsion used for spacecraft propulsion. It creates thrust by accelerating ions using electricity.
A magnetoplasmadynamic (MPD) thruster (MPDT) is a form of electrically powered spacecraft propulsion which uses the Lorentz force to generate thrust. It is sometimes referred to as Lorentz Force Accelerator (LFA) or MPD arcjet.
A pulsed plasma thruster (PPT), also known as a plasma jet engine, is a form of electric spacecraft propulsion. 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 starting in 1964. PPTs are generally flown on spacecraft with a surplus of electricity from abundantly available solar energy.
A propellant is a mass that is expelled or expanded in such a way as to create a thrust or another motive force in accordance with Newton's third law of motion, and "propel" a vehicle, projectile, or fluid payload. In vehicles, the engine that expels the propellant is called a reaction engine. Although technically a propellant is the reaction mass used to create thrust, the term "propellant" is often used to describe a substance which contains both the reaction mass and the fuel that holds the energy used to accelerate the reaction mass. For example, the term "propellant" is often used in chemical rocket design to describe a combined fuel/propellant, although the propellants should not be confused with the fuel that is used by an engine to produce the energy that expels the propellant. Even though the byproducts of substances used as fuel are also often used as a reaction mass to create the thrust, such as with a chemical rocket engine, propellant and fuel are two distinct concepts.
A spark gap consists of an arrangement of two conducting electrodes separated by a gap usually filled with a gas such as air, designed to allow an electric spark to pass between the conductors. When the potential difference between the conductors exceeds the breakdown voltage of the gas within the gap, a spark forms, ionizing the gas and drastically reducing its electrical resistance. An electric current then flows until the path of ionized gas is broken or the current reduces below a minimum value called the "holding current". This usually happens when the voltage drops, but in some cases occurs when the heated gas rises, stretching out and then breaking the filament of ionized gas. Usually, the action of ionizing the gas is violent and disruptive, often leading to sound, light, and heat.
Laser propulsion is a form of beam-powered propulsion where the energy source is a remote 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 glow discharge is a plasma formed by the passage of electric current through a gas. It is often created by applying a voltage between two electrodes in a glass tube containing a low-pressure gas. When the voltage exceeds a value called the striking voltage, the gas ionization becomes self-sustaining, and the tube glows with a colored light. The color depends on the gas used.
A vacuum arc can arise when the surfaces of metal electrodes in contact with a good vacuum begin to emit electrons either through heating or in an electric field that is sufficient to cause field electron emission. Once initiated, a vacuum arc can persist, since the freed particles gain kinetic energy from the electric field, heating the metal surfaces through high-speed particle collisions. This process can create an incandescent cathode spot, which frees more particles, thereby sustaining the arc. At sufficiently high currents an incandescent anode spot may also be formed.
The gridded ion thruster is a common design for ion thrusters, a highly efficient low-thrust spacecraft propulsion method running on electrical power by using high-voltage grid electrodes to accelerate ions with electrostatic forces.
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. Underwater jet propulsion is also used by several marine animals, including cephalopods and salps, with the flying squid even displaying the only known instance of jet-powered aerial flight in the animal kingdom.
The Large Plasma Device is an experimental physics device located at UCLA. It is designed as a general purpose laboratory for experimental plasma physics research. The device began operation in 1991 and was upgraded in 2001 to its current version. The modern LAPD is operated as the primary device for a national collaborative research facility, the Basic Plasma Science Facility, which is supported by the US Department of Energy, Fusion Energy Sciences and the National Science Foundation. Half of the operation time of the device is available to scientists at other institutions and facilities who can compete for time through a yearly solicitation.
A plasma propulsion engine is a type of electric propulsion that generates thrust from a quasi-neutral plasma. This is in contrast with ion thruster engines, which generate thrust through extracting an ion current from the plasma source, which is then accelerated to high velocities using grids/anodes. These exist in many forms. However, in the scientific literature, the term "plasma thruster" sometimes encompasses thrusters usually designated as "ion engines".
Spacecraft electric propulsion is a type of spacecraft propulsion technique that uses electrostatic or electromagnetic fields to accelerate mass to high speed and thus generate thrust to modify the velocity of a spacecraft in orbit. The propulsion system is controlled by power electronics.
High-power impulse magnetron sputtering is a method for physical vapor deposition of thin films which is based on magnetron sputter deposition. HIPIMS utilises extremely high power densities of the order of kW⋅cm−2 in short pulses (impulses) of tens of microseconds at low duty cycle of < 10%. Distinguishing features of HIPIMS are a high degree of ionisation of the sputtered metal and a high rate of molecular gas dissociation which result in high density of deposited films. The ionization and dissociation degree increase according to the peak cathode power. The limit is determined by the transition of the discharge from glow to arc phase. The peak power and the duty cycle are selected so as to maintain an average cathode power similar to conventional sputtering (1–10 W⋅cm−2).
The pseudospark switch a gas-filled tube capable of high speed switching. Pseudospark switches are functionally similar to triggered spark gaps.
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.
Atmosphere-breathing electric propulsion, or air-breathing electric propulsion, shortly ABEP, is a propulsion technology for spacecraft, which could allow thrust generation in low orbits without the need of on-board propellant, by using residual gases in the atmosphere as propellant. Atmosphere-breathing electric propulsion could make a new class of long-lived, low-orbiting missions feasible.
Microwave electrothermal thruster, also known as MET, is a propulsion device that converts microwave energy into thermal energy. These thrusters are predominantly used in spacecraft propulsion, more specifically to adjust the spacecraft’s position and orbit. A MET sustains and ignites a plasma in a propellant gas. This creates a heated propellant gas which in turn changes into thrust due to the expansion of the gas going through the nozzle. A MET’s heating feature is like one of an arc-jet ; however, due to the free-floating plasma, there are no problems with the erosion of metal electrodes, and therefore the MET is more efficient.
References
- ↑ Lunn, Jonathan (17 November 2016). "Vacuum Arc Thruster and Method of Operating the Same". WIPO IP Portal. Retrieved 20 October 2020.
