The amount of gas a rocket engine uses can vary significantly based on several factors, including the type of rocket, its size, and the mission requirements. For example, the Space Shuttle’s main engines used liquid hydrogen and liquid oxygen, consuming about 12 tons of propellant per second at full throttle during launch.
Generally, rocket engines are designed to maximize efficiency and thrust while minimizing the mass of the fuel needed. A small sounding rocket might use hundreds of kilograms of fuel, while larger launch vehicles can consume hundreds of thousands of kilograms in a single launch.
To give you a clearer picture, consider that rockets consume fuel in different stages of flight. During the initial phase of launch, a rocket might burn fuel at an unprecedented rate to overcome Earth’s gravity. Once they reach space, the consumption might taper off depending on the maneuvering required for the mission.
In summary, rocket engines can use varying amounts of gas based on their design and mission profile, with larger rockets consuming much more fuel compared to smaller ones.