PERFORMANCE OF EXPLOSIVES AND PROPELLANTS 1 Steady-State Detonations

The assumption of stable, one-dimensional detonations is not valid when one considers small-scale details, as Chapter 1 shows. However, although steady-state theory is invalid on a microscale, it does provide an excellent first approximation and a very useful aid in detonation performance calculations. Assumptions of chemical equilibrium in the steady-state model are incorrect. One of the interesting problems in modeling the equation of state of detonation products is finding reasonable changes in the detonation product composition which will reproduce the experimentally observed explosive and propellant performance. 

The Becker-Kistiakowsky-Wilson (BKW) equation of state is based upon a repulsive potential applied to the virial equation of state. The BKW equation of state has the form 

Two parameter sets are used, the RDX parameter set for most explosives, and the TNT parameter set for explosives with large amounts of solid carbon in the detonation products. 

The BKW code is described in detail in Appendix E and the personal computer executable code is included on the CD-ROM along with the USERBKW code, which assists in assembling the required input files for BKW. If the explosive or propellant elemental composition, density and heat of formation are known, the BKW code can be used to compute the C-J equilibrium detonation product composition, the C-J pressure, detonation velocity, temperature, the single shock Hugoniot and the isentrope. The HOM equation of state constants are generated for use in hydrodynamic codes. 

The Becker-Kistiakowsky-Wilson (BKW) equation of state described in Appendix E is the most used and best calibrated of those used to calculate detonation properties assuming steady-state and chemical equilibrium. Comparison of the calculated and experimental detonation properties permits evaluation of the errors to be expected from steady-state modeling of detonation products. Table 2.1 lists the calculated and experimental C-J properties of various explosives and mixtures. The calculated detonation product compositions of some of the explosives are given in Table 2.2. 

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