Shock initiation thresholds of bare and covered PBX-9404 and an HMX/TATB explosive called RX-26-AF were measured. The shocks were produced by the impact of flat-nosed and round-nosed steel projectiles in the velocity range of 0.5 to 2.2 km/s. Three types of coverings were used, 2 or 6 mm of tantalum, and a composite of aluminum and plastic. An Eulerian code containing material-strength and explosive-initiation models was used to evaluate our ability to calculate the shock initiation thresholds. These code calculations agreed well with the flat-nosed experimental data, but not so well with the round-nosed data.

Using the SIN and 2DE computer codes, we have conducted a numerical study of the shock initiation response of both bare and covered composition-B charges to projectile impact. In the bare charge case we observed two modes of shock initiation. Independence of the explosive response with respect to projectile aspect ratio was verified and critical conditions were determined as a function of projectile diameter with unit aspect ratio. The critical velocity was observed to have a linear dependence on the reciprocal of the square root of the diameter with values a little below experimental data. Additional linear relations to completely describe buildup to detonation were generated from the results. We found that development of detonation is similar in the case of covered charges. When the critical velocity was corrected for cover plate thickness, good agreement between the results for bare and covered charges was observed.

This work marks a stage in the evolution of a scientific and technical field which has been developed by the Commissariat a l'Energie Atomique (CEA) over several decades. Many members of the staff of the CEA have won re nown in this field, and their work has brought it to the high degree of excel lence for which it is internationally recognized today. These scientists had to consider every aspect of the field, as it concerned: modeling, which has recourse to fluid thermodynamics, molecular phys ics, and chemistry; numerical evaluation, which relies on mathematical analysis and data processing; and experiments in the firing area, which require specific stress generators and instrumentation. Whilst this book is a testament to the activity and success of staff of the CEA, it also reviews a number ofthe advances made in the discipline. How ever, it is not intended to be an exhaustive account of those advances; it is assumed that the reader can, if desired, consult the standard monographs, and more recent, more specialized works (notably W.C. Davis and W. Fickett, and C.L. Mader). The history of the discipline is interesting in itself, and also as an illustra tion of the causes which lead to progress in a coherent body of scientific work. I should like to make some comments on this progress, of which there is a fascinating summary in the introduction, and which will figure largely throughout the work.