Specific impulse maximum

It is rather interesting that the maximum specific impulse of a rocket propellant system occurs when (T2iMW2)1/2 is maximized, even though the rocket combustion process is not one of detonation [17],... 

Effect of hydrocarbon enthalpy of formation and hydrogen to carbon ratio on performance with liquid oxygen as rocket propellants (sea level specific impulse, Pc = 1000 psia, equilibrium expansion, mixture ratio of maximum specific impulse). 

Those entrusted with the development of propellant systems frequently have attempted to gain insight from new analyses, only to find the fundamental conceptual results of the analyses obscured in non-understandable detail. Correspondingly, many books which have appeared report and analyze the performance of chemical propellants (9 through 13). Yet rarely is an attempt made to explain why the performance results of the analyses are oriented as they are. This monograph is an attempt to state clearly the important concepts of propellant evaluation and to answer the important question of why Why is one propellant better than another, why does the point of maximum specific impulse shift towards stoichiometric mixture ratio as the chamber pressure is increased, why doesn t one obtain equilibrium chamber product concentrations with certain monopropellants, etc ... 

In the previous chapters, it was observed that in a real sense the highest specific impulse was obtained for those propellants which gave the highest heat release per unit mass rate of consumption of propellants. In a more ideal sense, maximum specific impulse is obtained when Tc/fH is maximized. For conditions of correct expansion specific impulse increases with increasing chamber pressure for two reasons first, the pressure ratio across the nozzle increases (ambient kept constant) and second according to LeChatelier s principle there is less dissociation at... 

Fig. V.A. 1 Hydrogen/oxygen combustion products characteristics and propellant performance. The maximum specific impulse lies at a mixture ratio between the mixture ratios of minimum molecular weight and maximum combustion temperature. Pc = 1000 psia, optimum equilibrium expansion to one atmosphere ambient pressure...

If the criterion of propellant density is added to that of performance yet another optimum mixture will result. The importance of density depends upon the propulsion system and mission to be performed and is not reducible to a unique, well-defined performance parameter or figure of merit. It suffices to comment that the optimum mixture ratio will be influenced by the desirability of a high propellant bulk density. Since oxidizers are generally more dense than fuels, with notable exceptions, the optimum mixture ratio which includes the effect of propellant density is generally to the oxidizer side of the optimum mixture ratio based on maximum specific impulse alone. The effect of consideration of propellant density, then, in general, results in a shift toward the stoichiometric mixture ratio. 

Carbon Ratio on Performance with Liquid Oxygen as Rocket Propellants (Sea Level Specific Impulse, Pc = 1000 psia, Equilibrium Expansion, Mixture Ratio of Maximum Specific Impulse.)... 

V.A. 2.. .. themixture ratio of maximum specific impulse shifts toward the stoichiometric mixture ratio with increasing chamber pressure. 

Figure 127 gives theoretical specific impulse for ammonium perchlorate-Al-polybudiene propellants. The maximum specific impulse was calculated as liigh as /j = 266s [ 11J. 

Figure 14.2 Variation of maximum specific impulse a function of effective equivalence ratio 1 — nonuniform filling/equilibrium 2 — nonuniform fiU-ing/kinetics 3 — uniform filling/kinetics and 4 — uniform filling/equilibrium.

CHAMBER PRESSURE, 300 PSIA MAXIMUM SPECIFIC IMPULSE... 

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