Propellant molar ratio is defined as the moles of propellant divided by the total moles of fuel, oxidizer and propellant. Propellant molar ratio will increases as the molecular weight of the propellant increases and as the oxidizer propellant mix decreases.

In high performance rockets, the propellant molar ratio is zero. Given the combustion efficiency, fuel molar, mixture, mixture oxidizer mix, oxidizer molecular, oxidizer propellant mix and propellant molecular the propellant molar 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
oxidizer mix = oxidizer propellant mix / oxidizer molecular
propellant mix = ( 1.0 - oxidizer propellant mix ) / propellant molecular
total mix = oxidizer mix + propellant mix
oxidizer mix /= total mix

propellant molar ratio = propellant mix * mixture oxidizer mix
 
 

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

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