Hard start

A hard start is a rocketry term referring to an overpressure condition during start of a rocket engine at ignition. In the worst cases, this takes the form of an unconfined explosion, resulting in damage, or destruction of the engine. A hard start is a rocketry term referring to an overpressure condition during start of a rocket engine at ignition. In the worst cases, this takes the form of an unconfined explosion, resulting in damage, or destruction of the engine. Rocket fuels, hypergolic or otherwise, must be introduced into the combustion chamber at the correct rate in order to have a controlled rate of production of hot gas. A 'hard start' indicates that the quantity of combustible propellant that entered the combustion chamber prior to ignition was too large. The result is an excessive spike of pressure, possibly leading to structural failure or even an explosion (sometimes humorously referred to as 'Spontaneous Self Disassembly').