In
aerospace engineering,
mass ratio is a measure of the efficiency of a
rocket. It describes how much more massive the vehicle is with
propellant than without; that is, the ratio of the rocket's
wet mass (vehicle plus contents plus propellant) to its
dry mass (vehicle plus contents). A more
efficient rocket design requires less propellant to achieve a given goal, and would therefore have a lower mass ratio; however, for any given efficiency a higher mass ratio typically permits the vehicle to achieve higher
delta-v.