Thrusters

Thrusters are propulsion devices that generate thrust by expelling reaction mass, enabling a vehicle to accelerate without external forces. They are used in spaceflight for orbit raising, station keeping, attitude control, deorbiting, and interplanetary propulsion, and in underwater or surface platforms for maneuvering.

Chemical thrusters burn propellants to produce high thrust over short durations. They include solid-fuel motors and liquid bipropellant or monopropellant systems. Their exhaust velocity is moderate, yielding lower specific impulse than electric propulsion but providing strong thrust for liftoff or rapid maneuvers.

Electric propulsion thrusters use electrical energy to accelerate propellant to high velocity, resulting in high specific impulse but relatively low thrust. Common types include ion thrusters (gridded electrostatic accelerators) and Hall-effect thrusters (electromagnetic acceleration). Electrothermal thrusters, such as arcjets, heat propellant to high temperature to increase exhaust velocity. Magnetic or pulsed-plasma variants also exist. Propellants are often inert noble gases or other suitable liquids or solids.

Other categories include cold gas thrusters, which eject stored gas at low thrust for fine attitude control, and pulsed plasma thrusters that generate a short, energetic plasma pulse. Thrust is described by magnitude and direction; thrust vector control is achieved by gimbaling nozzles or using multiple thrusters.

Performance depends on thrust, specific impulse, and power availability. High-thrust chemical systems are favored for launch and rapid maneuvers, while electric propulsion emphasizes efficiency for in-space propulsion. Limitations include power supply requirements for electric thrusters and toxic or handling concerns for some chemical propellants.