In recent years, substantial improvements in the performance of solid propellant guns have resulted from the development of higher energy propellants, higher loading density propellant charge configurations, and propellant geometries and concepts that have provided the progressively increasing gas generation rates required to efficiently use available increases in total energy. Unfortunately, these same features also typically lead to increases in ammunition vulnerability to enemy threats. Coupled with the current interest in much lighter fighting vehicles, the need for ammunition with reduced rather than increased sensitivity is obvious. This report describes the development of a new approach in the U.S. Army to address propellant energy/ performance and sensitivity/vulnerability as a single set of critical design requirements, to be addressed concurrently from the very beginning of the new energetic material research and development cycle. Some elements of this work were presented in abbreviated form at the 19th International Symposium on Ballistics in Interlaken, Switzerland in May 2001 [1]. iii ACKNOWLEDGMENTS The development and execution of a major new thrust such as the Insensitive High Energy Munitions (IHEM) Program involve the contributions of many people at the U.S. Army Research Laboratory (ARL). Acknowledgment is made to Drs. Arpad Juhasz, Thomas Minor, and William Oberle for contributions through the years to high progressivity/high density and in electro-thermal-chemical gun propulsion concepts. The work of Mr. Jerry Watson provided the background for shaped charge jet vulnerability response plot in Figure 11. Dr. Rob Lieb performs mechanical property measurements and interprets their significance. He also performs the microscopic examination of the non-ignited shear-punch samples. Many people are instrumental in conducting the small-scale vulnerability experiments at ARL. Dr. Reed Skaggs is in charge of our battlefield information coordination efforts, Mr. Al Bines and Mr. Bill Sunderland conduct the electric flyer experiments, and Dr. Larry Vande Kieft and Mr. Oliver Blake run the hot fragment conductive ignition and shear-punch experiment. We thank Dr.

The findings in this report are not to be construed as an official Department of the Army position, unless so designated by other authorized documents.

Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. REPORT DATE (DD-MM-YYYY)November 2005 ARL-TR-3671 SPONSOR/MONITOR'S ACRONYM(S) 9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) SPONSOR/MONITOR'S REPORT NUMBER(S) DISTRIBUTION/AVAILABILITY STATEMENTApproved for public release; distribution is unlimited SUPPLEMENTARY NOTES ABSTRACTWhile the use of guns and gun-like devices extends back in history for more than a millennium, the past century has been marked by significant advances in the technology of guns, the projectiles they launch, and the propulsion systems employed to launch these projectiles to ever-increasing velocities. This report chronicles a sampling of theoretical and experimental advances in the science of gun propulsion and its application to a wide range of practical gun propulsion concepts. BackgroundIn preparing for this report, the author had the privilege of reviewing hundreds of publications from numerous countries on both the seminal accomplishments and the technical details of theoretical and experimental efforts critical to the evolution of gun propulsion technology. The current work by no means attempts to catalog all of these efforts, but rather is intended to provide a sampling of interesting and important scientific accomplishments and practical developments leading to identifiable advances in gun propulsion. As this report was written primarily for oral presentation, the narrative performs the function of providing brief technical description and historical perspective associated with a clearly limited but hopefully interesting selection of topics pertinent to progress in the field of gun propulsion. (Much of this material was presented at the 20th International Symposium on Ballistics [1].) The reader is directed to the references for a more complete accounting of any of the reported accomplishments. Interior Ballistics -The Underpinning Science of Gun PropulsionThe interior ballistics of guns is the science of converting some form of stored energy (classically, chemical energy of a solid propellant released upon burning) into significant kinetic energy of a launch package in a very short timeframe and employing a launch system t...

Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. REPORT DATE (DD-MM-YYYY)November 2005 ARL-TR-3673 SPONSOR/MONITOR'S ACRONYM(S) 9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) SPONSOR/MONITOR'S REPORT NUMBER(S) DISTRIBUTION/AVAILABILITY STATEMENTApproved for public release; distribution is unlimited. SUPPLEMENTARY NOTES ABSTRACTOne of the many challenges facing weapon developers is the requirement for a highly lethal, lightweight, and compact largecaliber gun system. A promising concept recently investigated by the U.S. Army is that of a swing-chamber gun, necessitating the use of telescoped ammunition. Such ammunition not only reduces the volume available for the propellant charge, but also places severe geometric constraints on both the distribution of the propellant and the location and functionality of the ignition system. Results of an earlier study highlighted the fact that lumped-parameter interior ballistic codes cannot capture the influence of these configurational complexities on the processes of flamespreading and the ensuing formation of pressure waves. Application of a one-dimensional, two-phase flow code to this problem revealed the likelihood of such waves and raised concern over possible damage to the projectile. Subsequent use of a state-of-the-art, multidimensional interior ballistic code provided quantitative predictions of the flow in the annular region between the sidewall of the telescoped projectile and the cartridge case, detailed the formation of pressure waves, and furthered concern about transient projectile loads. The present report extends this effort, providing results applicable both to comparison with companion gun simulator experiments and appropriate for coupling to projectile/gun structural dynamics codes. iii

Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. REPORT DATE (DD-MM-YYYY) May 2006 REPORT TYPE ARL-TR-3796 SPONSOR/MONITOR'S ACRONYM(S) 9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) SPONSOR/MONITOR'S REPORT NUMBER(S) DISTRIBUTION/AVAILABILITY STATEMENTApproved for public release; distribution is unlimited. SUPPLEMENTARY NOTES ABSTRACTGun and ammunition designers typically employ various models initially to evaluate preliminary design concepts and ultimately to make specific decisions regarding the design and optimization of both individual components and all-up weapon systems. A wide range of computerized models exists today to address virtually every aspect of this process; in particular, the propelling charge designer has available several levels of interior ballistic models. These range from rather simple lumped-parameter models, providing basic performance data such as muzzle velocity and peak pressure and which run quickly on personal computers, to very complex multidimensional, multiphase flow models capable of describing the details of flamespreading, grain motion, and the formation of pressure waves, but employ specialized and occasionally unavailable input for propellant, charge, and gun parameters and require many hours on a workstation or supercomputer to complete the simulation. This report addresses the increasing level of physics and thus range of applicability to problems of increasing sophistication associated with three of today's most popular interior ballistic models: the lumped-parameter IBHVG2 code, the one-dimensional, two-phase flow XKTC code, and the state-of-the-art multidimensional, multiphase flow NGEN3 code. Recommendations are made with respect to the appropriate use of each of these highly useful tools, as well as the transferability of input data and comparability of results so obtained.