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A cold gas thruster (or a cold gas propulsion system) is a type of rocket engine which uses the expansion of a (typically inert) 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.
Direct comparison of physical properties, performance, cost, storability, toxicity, storage requirements and accidental release measures for hydrogen peroxide, hydroxylammonium nitrate (HAN), hydrazine and various cold gas monopropellants shows that hydrazine is the highest performing in terms of specific impulse. However, hydrazine is also the ...
The power for the thruster comes from the high pressure gas created during the decomposition reaction that allows a rocket nozzle to speed up the gas to create thrust. The most commonly used monopropellant is hydrazine (N 2 H 4, or H 2 N−NH 2), a compound unstable in the presence of a catalyst and which is also a strong reducing agent.
Rocket propellant may be expelled through an expansion nozzle as a cold gas, that is, without energetic mixing and combustion, to provide small changes in velocity to spacecraft by the use of cold gas thrusters, usually as maneuvering thrusters. To attain a useful density for storage, most propellants are stored as either a solid or a liquid.
A common fuel in small maneuvering thrusters is hydrazine. It is liquid at room temperature and, having a positive enthalpy of formation, can be used as a monopropellant to greatly simplify system design. But it is also extremely toxic and has a relatively high freezing point of +1C.
The simplest case of a thermal rocket is the case in which a compressed gas is held in a tank, and is released through a nozzle. This is known as a cold gas thruster.The thermal source, in this case, is simply the energy contained in the heat capacity of the gas.
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
A rocket engine is a reaction engine, producing thrust in accordance with Newton's third law by ejecting reaction mass rearward, usually a high-speed jet of high-temperature gas produced by the combustion of rocket propellants stored inside the rocket. However, non-combusting forms such as cold gas thrusters and nuclear thermal rockets also exist