Methods of Propulsion

Marine Propulsion

• Marine propulsion refers to the means of moving a vessel through a body of water. Methods of marine propulsion include the use of paddles and sails for smaller boats. On larger boats and most modern ships the propulsion system consists of an engine or motor that runs a propeller to move the ship through the water. Some speed boats and faster ships also make use of impellers (small propellers without blades) to propel boats or ships at high speeds. Such engine systems may run off steam, gas, diesel or nuclear power.

Aircraft Propulsion

• Aircraft propulsion is focused on moving aircraft through the air. To accomplish this propulsion system must both overcome drag for acceleration and balance the drag at cruising altitude. This means some aircraft will need excess thrust, such as fighter jets,, while others will need a propulsion system efficient at overcoming drag at cruising altitude such as airliners. Most aircraft will used an engine system to drive propellers to create propulsion, while some high speed jets will make use of afterburners to create excess thrust to overcome drag at high speeds.

Spacecraft Propulsion

• Spacecraft propulsion is mainly concerned with sending spacecraft and satellites into space. Spacecraft have a diverse range of propulsion methods, with many areas of active research. The main method of propulsion, however, is the use of chemical rockets and reaction engines. Using Newton's third law of motion, a reaction engine will expel reaction mass to produce propulsion that drives the spacecraft. A rocket engine on the other hand will use internal combustion heat to produce a reaction mass of hot gas that is pushed through a nozzle to produce propulsion. Such engines include chemical powered, solar powered, electrical and nuclear powered.

Ground Propulsion

• Ground propulsion refers specifically to moving a vehicle forward on the ground. The most obvious propulsion method on the ground in pure muscle such as the leg muscles when riding a bicycle. Another example includes horses drawing carriages or oxen pulling a blade to plow a field. There are still some communities around the world who rely on muscle power for propulsion. However, more modern societies moved to steam engines and from there, today rely on internal combustion engines and electric motors to generate propulsion for ground vehicles.