Specific Impulse Values

Elemental fluorine has been studied as a rocket propellant as it has an exceptionally high specific impulse value. 

Table VI. Maximum Theoretical Specific Impulse Values of Heterogeneous Fuels with Nitrogen Tetroxide...

Theoretical performance calculations were first made on propellant compositions containing the acetylenic polyurethane binder and ammonium perchlorate as the oxidant. These calculations assumed a shifting equilibrium in the rocket exhaust. The calculations demonstrated two of the principal advantages of the acetylenic binders—namely the increased performance provided by the energetic triple bond and the fact that optimum performance is achieved at relatively low levels of oxidizer. Specific impulse values of 251—253 lbf.-sec./lbm. were calculated at 1000 p.s.i.a. chamber pressure for optimum oxidizer loadings. Furthermore, peak performance was achieved at 83% oxidizer, and even at an 80% loading a theoretical I8P of 250 seconds was obtained. 

Rocket power plants use the heat liberated by the reaction of chemical propellants, liquid or solid, as the source of energy. Specific impulse is more in liq propint applications it is difficult to accurately measure the propellant flow rate of solid-propellant-rocket thrust producing units. The average specific impulse is occasionally calculated for solid-propellant units on the basis of thrust, duration, and proplnt wt, hut there are other parameters that are more convenient. Modem rocket power plants are capable of obtaining specific impulse values between 240-250 lb/(lb/sec) 1... 

Molecules 2 and 4 have high specific impulse values, calculated to be 25 and 20% better than HMX, respectively. Both of these compounds have relatively high heats of formation and produce fairly large amounts of... 

Specific impulse value may be approximately calculated if the pressure-time dependence is known, assuming that there is no lateral scattering of detonation products. Assuming that the expansion isentrope equation for the detonation products has the form (Eq. (4.50))... 

Solid propellants usually consist of ammonium nitrate (NH4NO3), ammonium perchlorate (NH4CIO4), and aluminum powder bound in a resin of polystyrene, polyurethane, or polybutadiene. Specific impulse values of 250-300 s are achieved depending on the choice of fuel and oxidizer. 

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