Propellant mass ratio is the mass of propellant divided by the total mass of fuel, oxidizer and propellant. The propellant mass is equal to one minus the oxidizer propellant mix times the total mass of the oxidizer and propellant.

Seventy percent hydrogen peroxide is thirty percent propellant by mass. The overall propellant mass ratio in that case would be a bit less than thirty percent because of the added mass of the fuel, with methane it works out to be twenty eight percent. In high performance rockets, the propellant mass ratio is zero. Given the combustion efficiency, fuel molecular, fuel molar, mixture, mixture oxidizer mix, oxidizer mix molecular and oxidizer propellant mix the propellant mass ratio can be calculated.

relative fuel = 1.0 - mixture
mixture oxidizer mix = 1.0 + mixture

unreacted fuel = 0.0
if ( relative fuel > mixture oxidizer mix ) {
    unreacted fuel = relative fuel - mixture oxidizer mix
}

If the combustion isn't ideal:

if ( combustion efficiency < 1.0 ) {

Then the quadratic equation is used to determine the part of each reactant that combines chemically:

    ratio = 9999999.9
    if ( relative fuel != 0.0 ) {
    ratio = mixture oxidizer mix / relative fuel
    }
    unreactability = 1.0 / ( 1.0 - combustion efficiency )
    a = 2 * unreactability * unreactability
    b = a * ( ratio - 1.0 )
    c = ratio + 1.0
    unreacted = 0.5 / a * ( sqrt( b * b + 4.0 * a * c ) - b )
    unreacted fuel = relative fuel * unreacted
}

relative fuel *= fuel molar
mixture oxidizer mix *= oxidizer mix molar
mixture molar = relative fuel + mixture oxidizer mix
mixture oxidizer mix /= mixture molar

fuel mass ratio = relative fuel * fuel molecular
oxidizer mix mass ratio = mixture oxidizer mix * oxidizer mix molecular
mixture mass = fuel mass ratio + oxidizer mix mass ratio
oxidizer mix mass ratio /= mixture mass

propellant mass ratio = ( 1.0 - oxidizer propellant mix ) * oxidizer mix mass ratio
 
 

This is used in tripropellant rocket, pumped rocket and rocket cost.
 
 

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