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. An ion thruster creates a cloud of positive ions from a neutral gas by ionizing it to extract some electrons from its atoms. The ions are then accelerated using electricity to create thrust. Ion thrusters are categorized as either electrostatic or electromagnetic.
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 Pulsed Plasma Rocket (PPR), or as a plasma jet engine (PJE), 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 pulsed inductive thruster (PIT) is 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.
The Variable Specific Impulse Magnetoplasma Rocket (VASIMR) is an electrothermal thruster under development for possible use in spacecraft propulsion. It uses radio waves to ionize and heat an inert propellant, forming a plasma, then a magnetic field to confine and accelerate the expanding plasma, generating thrust. It is a plasma propulsion engine, one of several types of spacecraft electric propulsion systems.
Specific impulse is a measure of how efficiently a reaction mass engine, such as a rocket using propellant or a jet engine using fuel, generates thrust. In general, this is a ratio of the impulse, i.e. change in momentum, per mass of propellant. This is equivalent to "thrust per massflow". The resulting unit is equivalent to velocity, although it doesn't represent any physical velocity ; it is more properly thought of in terms of momentum per mass, since this represents a physical momentum and physical mass.
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 with magnetohydrodynamics. The fluid is directed to the rear and as a reaction, the vehicle accelerates forward.
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.
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.
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.
The helicon double-layer thruster is a prototype electric spacecraft propulsion. It was created by Australian scientist Christine Charles, based on a technology invented by Professor Rod Boswell, both of the Australian National University.
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 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.
Spacecraft electric propulsion is a type of spacecraft propulsion technique that uses electrostatic or electromagnetic fields to accelerate mass to high speed and thus generating thrust to modify the velocity of a spacecraft in orbit. The propulsion system is controlled by power electronics.
A cold gas thruster is a type of rocket engine which uses the expansion of a pressurized gas to generate thrust. As opposed to traditional rocket engines, a cold gas thruster does not house any combustion and therefore has lower thrust and efficiency compared to conventional monopropellant and bipropellant rocket engines. Cold gas thrusters have been referred to as the "simplest manifestation of a rocket engine" because their design consists only of a fuel tank, a regulating valve, a propelling nozzle, and the little required plumbing. They are the cheapest, simplest, and most reliable propulsion systems available for orbital maintenance, maneuvering and attitude control.
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.
A magnetic nozzle is a convergent-divergent magnetic field that guides, expands and accelerates a plasma jet into vacuum for the purpose of space propulsion. The magnetic field in a magnetic nozzle plays a similar role to the convergent-divergent solid walls in a de Laval nozzle, wherein a hot neutral gas is expanded first subsonically and then supersonically to increase thrust. Like a de Laval nozzle, a magnetic nozzle converts the internal energy of the plasma into directed kinetic energy, but the operation is based on the interaction of the applied magnetic field with the electric charges in the plasma, rather than on pressure forces acting on solid walls. The main advantage of a magnetic nozzle over a solid one is that it can operate contactlessly, i.e. avoiding the material contact with the hot plasma, which would lead to system inefficiencies and reduced lifetime of the nozzle. Additional advantages include the capability of modifying the strength and geometry of the applied magnetic field in-flight, allowing the nozzle to adapt to different propulsive requirements and space missions. Magnetic nozzles are the fundamental acceleration stage of several next-generation plasma thrusters currently under development, such as the helicon plasma thruster, the electron-cyclotron resonance plasma thruster, the VASIMR, and the applied-field magnetoplasmadynamic thruster. Magnetic nozzles also find another field of application in advanced plasma manufacturing processes, and their physics are related to those of several magnetic confinement plasma fusion devices.
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 is fixed to the rocket and supplies the principal amount of thrust.
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.
