What are the advantages of liquid fuel rocket engines?

Answer 1

There are two types of rockets -- those that use liquid fuel and those that use solid fuel.

Liquid fuel rockets have two main advantages. Liquid fuel rocket engines burning can be controlled. That is, they can be turned on and off, and their thrust (pushing force) can be controlled/varied. Second, they produce more thrust for the same amount (weight) of fuel -- called specific impulse.

Liquid fuel is also cheaper, but that's rarely a consideration as it is such a small part of the cost.

Answer 2

Liquid fueled rocket engines have the ability to stop the engine burn process after ignition, usually by cutting off the fuel flow to the engine. Typical liquid fuel engines are fueled by liquid oxygen, liquid hydrogen, or as in the case of the Shuttle's Main Engine and External Tank, a combination of those two.

Solid fuel (propellant) rocket engines, once ignited, cannot be shut down - the only way to stop them is to destroy them, but even that will not keep the solid fuel from ceasing to burn. Once solid rocket fuel is ignited, it will burn until it is completely expended.

The reason for this is that solid rocket fuel creates its own oxygen supply, by means of an ingredient called an oxydizer. For sustained combustion, any fire needs oxygen, heat and fuel, the removal of any one of those will halt the combustion process. In solid propellants, the oxydizer is mixed in solid form with the fuel itself (so that it can burn in space where oxygen exists only in molecular form). Once ignited, it supplies itself with what it needs to sustain itself, making it nearly impossible to stop once started.

Answer 3

Liquid fuel rocket engines provide higher specific impulse and greater efficiency compared to solid fuel rockets. They also offer the ability to throttle and shut down the engine, allowing for more precise control during flight. Additionally, liquid fuel engines can be re-ignited multiple times, enabling complex maneuvers and missions.