<p>Liquid rocket main engine valve (MEV) serves the purpose of isolating the propellants in tankages from engine and allows propellant to the engine during engine operations. Along with the isolation of propellant from engine cavities, the opening and closing characteristics of MEV play a vital role in the start and shutdown transient of a liquid rocket engine. To have a smooth start of a liquid rocket engine, usually a lead of one propellant over another is required and MEVs play an important role to ensure the same. In this paper, dynamic modelling of a normally closed-type spring-loaded pneumatically operated MEVs of an earth-storable propellant liquid rocket engine is carried out and various variables which affect the opening and closing characteristic of a main engine valve are also studied. Results obtained from the mathematical model are compared with experimental data as well as data obtained from flights/ground tests.</p>