R. Meyer J. Köhler A. Homburg Explosives

321 Thermodynamic Calculation of Decomposition Reactions
The composition of the reaction products (mol %):
28.63% H2O
28.39% CO
21.07% CO2
4.13% H2
14.63% N2
0.21% O2
0.48% NO
0.37% KOH
1.50% OH
}
0.42% H
dissociated atoms and radicals
0.09% O
0.02% K
2. Rocket Propellants
Raketentreibstoffe; propellants de roquette
The calculation of the performance data of rocket propellants is carried
out in the same manner as shown above for gunpowders, but the
burning process in the rocket chamber proceeds at constant pressure
instead of constant volume. For the evaluation of the heat of reaction,
the difference of the enthalpies of formation instead of the energies
must now be used; for the internal heat capacities, the corresponding
enthalpy values are listed in Table 38 below (instead of the energy
values in Table 31); they are based on the average specific heats cp at
constant pressure instead of the cv values. The first step is to calculate
the reaction temperature Tc and the composition of the reaction gases
(mole numbers n1, etc.). The second step is to evaluate the same for
the gas state at the nozzle exit (transition from the chamber pressure
pc to the nozzle exit pressure pe e.g., the atmospheric pressure). The
basic assumption is, that this transition is “isentropic”, i.e., that the
entropy values of the state under chamber pressure and at the exit are
the same. This means that the thermodynamic transition gives the
maximum possible output of kinetic energy (acceleration of the rocket
mass).
The calculation method begins with the assumption of the temperature
of the exit gases, e.g., Te = 500 K. The transition from the thermodynamical
state in the chamber into the state at the nozzle exit is
assumed to be instantaneous, i.e. the composition of the gases remains
unchanged (“frozen” equilibria). The entropy of the exit gases at
the assumed temperature Te is assumed to be the same as the
entropy of the gases in the chamber (known by calculation); the
assumed value Ta is raised until both entropy values are equal. Since
both states are known, the corresponding enthalpy values can be
calculated. Their difference is the source of the kinetic energy of the