Specific impulse is a useful value for compare engines, similar to miles per gallon as well as liters per 100 kilometers is used for cars. A propulsion process and system having a higher specific behavioral instinct is more propellant-efficient. As move the unit of a few moments can seem perplexing to laypeople, it is fairly simple to know as “hover-time”: how long a rocket can certainly “hover” before running from fuel, given the weight of this propellant/fuel.