The rocket equation is a mathematical statement about the cost of carrying your own means of escape.

The rocket equation, usually called the Tsiolkovsky rocket equation, describes how much change in velocity a rocket can achieve by expelling propellant. Written as Δv = v_e ln(m₀/m_f), it links velocity change to exhaust velocity and the ratio between initial and final mass. Its logarithm carries a harsh lesson: gaining more speed demands rapidly increasing amounts of propellant. That relationship shapes nearly every serious rocket design, from small orbital launchers to interplanetary spacecraft. It also explains why multistage rockets are so useful. It is used primarily in spacecraft design, launch vehicle engineering, and orbital mission planning.