Variable Specific Impulse

Variable Specific Impulse (VSI) is a rocket engine feature that allows adjusting how efficiently it uses its fuel during a mission. Specific impulse measures how well a rocket engine produces thrust relative to its fuel consumption—higher values mean more efficient fuel use. With VSI, the engine can change its performance level to suit different phases of flight; for example, using more fuel-efficient settings for cruising and more powerful settings for acceleration. This adaptability enhances mission flexibility and efficiency, enabling rockets to optimize fuel use and improve overall performance across various stages of space travel.