Oxidizer heat of formation is the amount of energy per kilomole of substance required to form the molecule in the state it is in while in the oxidizer tank from elemental molecules at standard conditions. A positive number means energy is required to form the molecule and it will release energy when going to the standard state of its elemental components. A negative number means energy is released when forming the molecule and it will absorb energy when going to the standard state of its elemental components. Generally the higher the number, the more reactive or volatile the substance will be. When a substance is heated, its heat of formation rises.

Liquid oxygen is the most commonly used oxidizer in large liquid fueled rockets. Ozone is explosive, as of 2001 it has only been used in laboratory rocket engines. With extreme cleanliness, a mix of a third ozone and two thirds oxygen could be used safely. Monoatomic oxygen is barely stable in the solid form at twenty degrees Kelvin, as of 2001 it hasn't even been used in laboratory rocket engines. The oxidizer heat of formation is used to calculate the mix heat, which is in turn used to calculate the reactant enthalpy.

mix heat = oxidizer mix * oxidizer heat of formation + propellant mix * propellant heat of formation

reactant enthalpy = fuel molar ratio * fuel heat of formation + mixture oxidizer mix * mix heat
 
 

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