Ballistic Research Laboratory Research Articles

СИЛА ТА МОМЕНТ СИЛИ МАГНУСА. ЇХ ВПЛИВ НА ДАЛЬНІСТЬ СТРІЛЬБИ 155-ММ СНАРЯДІВ

An important component of the main vector of aerodynamic forces and moments of the projectile is the force and moment from the Magnus force, which significantly affect the dynamics of the projectile flight. At the same time, the influence of the Magnus force and moment on the flight of projectiles has been studied relatively little, in addition, the leading scientists of Ballistic Research Laboratories (USA) published quantitative indicators achieved during its calculations, which do not fully meet the requirements for the accuracy of their determination. It is shown that the Magnus force and moment depend on the density of the air, the angular velocity of rotation and the velocity of the projectile, the lateral surface and diameter of the projectile, as well as the angle of its nutation. To evaluate the influence of the Magnus force and moment (their aerodynamic coefficients) on the range of the projectile, a difference method is used, which consists in solving the system of differential equations of spatial motion of a projectile so that changing the value of the aerodynamic coefficient results in a change in the value of the flight range. Numerical modeling of the dependence of the flight range of the 155-mm PF Assegai M2000 projectile and the 155-mm PF ERFB/BB projectile on the change in the magnitude of aerodynamic force and Magnus moment coefficients by 1 % was carried out. It is shown that the aerodynamic force coefficient of Magnus creates the largest errors in the range at the minimum charge, the deviation reaches – 0,005 %, the smallest at the maximum charge – 0,003 %. The largest error in the flight range of the projectile from the aerodynamic coefficient of the Magnus moment is observed at the minimum charge, the deviation reaches 0,6 % D; the effect on other charges leads to much smaller deviations, which are 1-3 orders of magnitude smaller compared to the minimum charge. The obtained results provide an opportunity to assess the required accuracy of determining the aerodynamic coefficients of the Magnus force and the moment of the Magnus force under different conditions of firing by artillery systems.

Numerical and Experimental Comparative Analysis of Ballistic Performance of Packages Made of Biaxial and Triaxial Kevlar 29 Fabrics

Abstract The objective of this study is a comparative analysis of the ballistic effectiveness of packages made of biaxial and triaxial Kevlar 29 fabrics under the hitting of Parabellum 9×19 bullet. We conduct both numerical simulations using the LS-Dyna program and experimental research in a ballistic research laboratory. Based on the comparative analysis of the results from the numerical and experimental research, demonstrated differences exist in the ballistic effectiveness between the packages made of biaxial fabrics and the packages consisting of triaxial fabrics. For this purpose, the residual velocity of the bullet is analyzed in detail in terms of the maximum deformation cone, the shape of the deformation cone, and the distribution of stress for the textile ballistic packages. It is established that the packages made of triaxial fabric show a considerably smaller deformation cone compared with the packages made of biaxial fabric, a more favorable shape of the deformation cone from the perspective of ballistic trauma and distribution of stress similar to materials with isotropic properties. Poorer properties are recorded for these packages in the case of the minimum number of layers necessary for stopping the bullet, which arises from the open-work structure of the fabric.

Scaling Laws for the Peak Overpressure of a Cannon Blast

For large cannons, blast overpressure can have a detrimental effect on the crew in the near field (i.e., within a distance of 50 tube diameters or calibers from the muzzle center) as well as on the support personnel and equipment in the far field (i.e., at a distance greater than 50 calibers). Therefore, an efficient method to determine the peak overpressure due to a cannon blast is highly desired. In this study, we investigate scaling laws for the peak overpressure, due to the primary blast of a large cannon, with the aim that they can be applied as an efficient method to evaluate the peak overpressure in the far field. We explore two types of scaling laws; each type is based on a power-law model involving a prefactor and an exponent as model parameters. The two types of the power-law models differ in the way they incorporate the polar angle dependence. The first type was proposed by Fansler and Schmidt (1983, “The Prediction of Gun Muzzle Blast Properties Utilizing Scaling,” U.S. Army Ballistic Research Laboratory, Aberdeen Proving Ground, MD, Report No. ARBRL-TR-02504). They developed a muzzle-center based scaling law (MCSL) in which the polar angle dependence was incorporated through a reference length scale to define a nondimensional or scaled radial distance from the muzzle center and the model parameters were independent of the polar angle. They calibrated the parameters by employing least-squares fit to a wide range of experimental data. In this study, we recalibrated or updated the parameters for the current cannon by using the numerical simulation data for the cannon blast in the near field. Additionally, we developed a second type of scaling law in which the radial distance is defined from the blast center (in contrast to the muzzle center) and scaled using the inner tube diameter. In this model, the angular dependence is incorporated directly into the model parameters. For this model too, we calibrated the parameters by using the numerical simulation data. We observe that both the modified version of the muzzle-center based scaling law as well as the blast-center based scaling law (BCSL) show a significantly closer fit to the numerical and experimental data and achieve a similar level of accuracy. This indicates that the current form or structure of the two types of power-law based scaling models is able to fit well with the near-field data; however, the current methodology requires a calibration process for a given cannon of interest. In the future, with far field data, we plan to evaluate predictions in the far field.

Regulatory testing for safety: The mathematics of broad-based results

Testing of the safety of manufactured products is typically conducted under a specified set of conditions. For example, when projecting an instrumented headform at the front of a car to assess the pedestrian safety of that model of car, the speed of the headform is specified. But surely, if they were asked, the public and policymakers would say that the result at one speed is a rather artificial measure, and they instead wish to know the average level of safety across real-world impact scenarios. One possible solution is to directly test across the range of conditions and combinations of conditions. However, manufacturers typically want to economise by conducting fewer tests. This article considers how to determine a product's saftey for a range of conditions, while also being economical with the testing. What is proposed has three steps. The first is to generalise the quantity observed in test conditions to what would be observed under different conditions. This is likely to involve a theory and a formula. For example, in a headform impact test the quantity observed might be HIC (the Head Injury Criterion), the condition that varies might be impact speed, and a formula might be available for the dependence of HIC on speed. The second is to convert the test quantity to something that is meaningfully averaged. This might be the dollar cost associated with a particular level of HIC, or perhaps the probability of death. The third is to obtain the average, by integration over the condition that varies from crash to crash (such as impact speed). In principle, this procedure is quite general and applicable to many other forms of testing. Good information is required for the three steps, but this is inherent in aiming for a broad-based result, rather than due to the method. References P. H. Deitz. A V/L taxonomy for analyzing ballistic live-fire events. Proceedings of the 15th International Symposium on Military Operational Research , 1998. http://ismor.cds.cranfield.ac.uk/15th-symposium-1998 R. G. Herbert and D. C. McWhannell. Shape and frequency composition of pulses from an impact pair. J. Eng. Ind. 99:513–518, 1977. doi:10.1115/1.3439270 K. H. Hunt and F. R. E. Crossley. Coefficient of restitution interpreted as damping in vibroimpact. J. Appl. Mech. 42:440–445, 1975. doi:10.1115/1.3423596 T. P. Hutchinson. Dependence of the Head Injury Criterion and maximum acceleration on headform mass and initial velocity in tests simulating pedestrian impacts with vehicles. J. Biomech. Eng. 135:114508, 2013. doi:10.1115/1.4025331 T. P. Hutchinson. Experimental injury: Inference from proxy observations in a test to the real-world average. J. Battlefield Tech. 18(1):1–6, 2015. http://search.informit.com.au/documentSummary;dn=958266262006914;res=IELENG T. P. Hutchinson, R. W. G. Anderson and D. J. Searson. Pedestrian headform testing: Inferring performance at impact speeds and for headform masses not tested, and estimating average performance in a range of real-world conditions. Traffic Inj. Prev. 13:402–411, 2012. doi:10.1080/15389588.2012.660252 T. P. Hutchinson, D. J. Searson, R. W. G. Anderson, J. K. Dutschke, G. Ponte and A. L. van den Berg. Protection of the unhelmeted head against blunt impact: The pedestrian and the car bonnet. Proceedings of the Australasian Road Safety Research, Policing and Education Conference , 2011. http://acrs.org.au/files/arsrpe/Protection%20of%20the%20unhelmeted%20head%20against%20blunt%20impact.pdf W. Kokinakis and J. Sperrazza. Criteria for incapacitating soldiers with fragments and flechettes. Technical Report 1269, Ballistic Research Laboratories, Aberdeen Proving Ground, MD, 1965. http://www.dtic.mil/dtic/tr/fulltext/u2/359774.pdf R. VanAmburg. An approach to analyze personnel injury of reflective spall from small-arms protective body armor. Technical Report ARL-TR-5595, U.S. Army Research Laboratory, Aberdeen Proving Ground, MD, 2011. http://www.dtic.mil/dtic/tr/fulltext/u2/a550618.pdf R. B. Webby, P. T. Adamson, J. Boland, P. G. Howlett, A. V. Metcalfe and J. Piantadosi. The Mekong–-applications of value at risk (VaR) and conditional value at risk (CVaR) simulation to the benefits, costs and consequences of water resources development in a large river basin. Ecological Modelling , 201:89–96, 2007. doi:10.1016/j.ecolmodel.2006.07.033

Unsteady Vibration Aerodynamic Modeling and Evaluation of Dynamic Derivatives Using Computational Fluid Dynamics

Unsteady aerodynamic system modeling is widely used to solve the dynamic stability problems encountering aircraft design. In this paper, single degree-of-freedom (SDF) vibration model and forced simple harmonic motion (SHM) model for dynamic derivative prediction are developed on the basis of modified Etkin model. In the light of the characteristics of SDF time domain solution, the free vibration identification methods for dynamic stability parameters are extended and applied to the time domain numerical simulation of blunted cone calibration model examples. The dynamic stability parameters by numerical identification are no more than 0.15% deviated from those by experimental simulation, confirming the correctness of SDF vibration model. The acceleration derivatives, rotary derivatives, and combination derivatives of Army-Navy Spinner Rocket are numerically identified by using unsteady N-S equation and solving different SHV patterns. Comparison with the experimental result of Army Ballistic Research Laboratories confirmed the correctness of the SHV model and dynamic derivative identification. The calculation result of forced SHM is better than that by the slender body theory of engineering approximation. SDF vibration model and SHM model for dynamic stability parameters provide a solution to the dynamic stability problem encountering aircraft design.

English

The rail track rocket sled (RTRS) national test facility at Terminal Ballistics Research Laboratory (TBRL) has been established to provide simulated flight environment for carrying out aero dynamic studies, terminal studies and kinematic studies of variety of test articles. The sled velocity is a critical parameter in evaluation trials. This velocity is also used to ensure that the maximum speed and allowable g loading does not exceed the value which the test article will experience under free flight in air1. Overseas, the facilities have been set up to attain velocities ranging from sub-sonic to hypersonic2. The rocket sled at TBRL can be presently accelerated to travel along the rail track at velocities up to 500 m/s and capability is being built to increase velocity beyond 500 m/s. Signals acquired from existing magneto-inductive arrangement have been analysed in the present work. The experiments indicate that with increase in velocity the rate of change of flux increases, the amplitude of induced emf also increases but terminal voltage decreases and shape of the acquired pulse gets distorted. The parameters of magneto-inductive pick up have been modified in such a way that there is improvement in amplitude and shape of the received pulse with increase in velocity. The improved signals have been analysed and simulation results validated with feasible experiments. This paper also discusses issues, challenges and proposes recommendations in improving the sensor for measurement of velocity beyond Mach 1.5. It has been found that it is prudent to reduce the inductance by reducing the number of turns and changing the core from soft iron core to air core which will improve the response of inductive pick up coil at high velocity. Defence Science Journal, 2014, 64(2), pp. 143-151. DOI: http://dx.doi.org/10.14429/dsj.64.5034

Energy Absorption and Dynamic Deformation of Backing Material for Ballistic Evaluation of Body Armour

The measurement of back face signature (BFS) or behind armour blunt trauma (BABT) is a critical aspect of ballistic evaluation of body armour. BFS is the impact experienced by the armour wearing body, when subjected to a non-penetrating projectile. Mineral or polymeric clay is used to measure the BFS. In addition to stopping the projectile, the body armour can be used only when the BFS also falls within permissible limits. The extent of the BFS depends upon the behavior of the backing material in different loading conditions and prior history. This paper explains some of the studies carried out on the backing material used for ballistic evaluation in Terminal Ballistics Research Laboratory, Chandigarh. It has been observed that the backing material is highly non-linear viscoelastic in nature. The depth of deformation is also linearly proportional to the impact energy and temperature. The effect of time on the depth of deformation is gradual and does not influence the BFS values during a standard ballistic evaluation comprising of 6-8 shots. Defence Science Journal, 2013, 63(5), pp.462 -466 , DOI:http://dx.doi.org/10.14429/dsj.63.3821

American Studies after the Internet

American Studies after the Internet Lauren Frederica Klein (bio) The Computer Boys Take Over: Computers, Programmers, and the Politics of Expertise. By Nathan Ensmenger. MIT Series in the History of Computing. Cambridge, Mass.: MIT Press, 2010. 336 pages. $30.00 (cloth). Programmed Visions: Software and Memory. By Wendy Hui Kyong Chun. MIT Series in Software Studies. Cambridge, Mass.: MIT Press, 2011. 256 pages. $32.00 (cloth). Race after the Internet. Edited by Lisa Nakamura and Peter A. Chow-White. New York: Routledge Press, 2011. 352 pages. $150.00 (cloth). $39.95 (paper). Debates in the Digital Humanities. Edited by Matthew K. Gold. Minneapolis: University of Minnesota Press, 2012. 504 pages. $105.00 (cloth). $34.95 (paper). June 1945: The height of the war in the Pacific, Allied forces in Germany had only just assumed control of the recently defeated nation, and in the United States, citizens continued to mourn the loss of Franklin Delano Roosevelt, their wartime commander in chief. In the midst of this global tumult, six women were summoned to the U.S. Army’s Ballistics Research Laboratory in Aberdeen, Maryland, where they were assigned to the top-secret “Project X.” As the women would soon discover, Project X was the code name for the Electronic Numerical Integrator and Computer (ENIAC) project, an enterprise that would culminate in the world’s first electronic, digital, and programmable computer. Upon its completion, in 1946, the ENIAC machine was immediately deployed to calculate the firing tables required for the precision targeting of the Army’s long-range ballistic weapons. However, the “ENIAC girls,” as the women who operated the machine were known, would be acknowledged for their pioneering role in the history of computing—for they were the world’s first computer programmers—only fifty years after the fact.1 [End Page 861] The surprise of this story is not only how strongly it resonates with many of the issues engaged by American studies today—such as the gendering and valuation of labor (or lack thereof) and the rise of the U.S. military-industrial complex—but also that it has only recently begun to be mined for its significance as the starting point of today’s digital culture. It suggests, moreover, how the fields of American studies and the digital humanities, so often viewed as disciplinarily, methodologically, and ontologically distinct, are in fact deeply intertwined. For decades, the creation of digital tools and the application of digital methods was the purview of “humanities computing,” a close-knit field of dedicated practitioners. Renamed the digital humanities in the early 2000s, the field has since been extended to encompass what Kathleen Fitzpatrick describes in her contribution to Debates in the Digital Humanities as the array of “changes that digital technologies are producing across the many fields of humanistic inquiry” (12).2 But if the digital humanities is to become an umbrella term for a generalized epistemology of the digital, it is of the utmost importance that we understand the origins and implications of the digital itself. The origins of the digital humanities are most often traced to 1949, when an Italian Jesuit priest, Father Roberto Busa, approached IBM with an idea of employing a computer to compile an index verborum of the complete works of Thomas Aquinas—nearly eleven million words of medieval Latin.3 This story, replete with anecdotes about punch-cards trucked through narrow, sixteenth-century streets, establishes intellectual ambition, technological resourcefulness, and a not insignificant amount of whimsy as the foundational values in the field. The story of the “ENIAC girls” reveals a more complex prehistory, however—one that, as Nathan Ensmenger’s Computer Boys Take Over and Wendy Hui Kyong Chun’s Programmed Visions each demonstrate, is shot through with contradiction. Indeed, the history of the digital humanities, in both its original and its expanded meanings, is also, necessarily, a history of gender, labor, empire, and—as I discuss below—race. And the ideological and conceptual systems that underpin each of these terms are, in ways that have not yet been sufficiently acknowledged, informed by our ideas about and experience with the digital.4 When Tara McPherson, at the 2011 American Studies Association annual meeting, posed the question...

Metallurgical Studies on Explosive Welded Aluminium Alloy-Stainless Steel Bimetallic Plates

Aluminium alloys and austenitic stainless steels are often used for construction of cryogenic pressure vessels owing to their attractive properties at cryogenic temperatures. Indian space programme requires AA2219/ICSS1218-SS321 bimetallic components which are machined from explosive welded plates. Pure aluminium sheet is used as an interlayer between aluminium alloy and steel to achieve a satisfactory bond. Internal soundness of the joint is evaluated through ultrasonic testing (UT). The present paper discusses bonding trials carried out by varying the explosive parameters using facilities and expertise of Terminal Ballistic Research Laboratory (TBRL), Chandigarh and M/s Giridhari Explosives Private Limited (GEPL), Hyderabad. The welded joint is extensively characterised with respect to Lap Shear and Ultimate Tensile Strength at ambient temperature and for metallographic analysis.

When Women Were Computers: LeAnn Erickson, Top Secret Rosies

The documentary film Top Secret Rosies, directed by LeAnn Erickson, provides a long overdue and fascinating look into the experiences of the young American women who worked as human “computers” during World War II. The hour-long film makes the case that the top-secret activities of the women of the Philadelphia Computing Section of the U.S. Army's Ballistic Research Laboratory (housed in the University of Pennsylvania’s Moore School of Engineering) were crucial not only to the war effort but also the development of ENIAC, arguably the first electronic digital computer. The film mixes archival footage with recent interviews of the “Rosies” and professional historians. This film will be of interest to historians of technology, computing, and gender, as well as U.S. and military historians.

The International Symposium on Ballistics

The International Symposium on Ballistics

Dynamic response of two strain-hardened aluminum alloys

Despite their common usage in armor applications such as lightweight armored vehicles, the dynamic material response of 5083-H131 and 5083-H32 strain-hardened aluminum alloys has not been previously reported in the open literature. Measurement of the dynamic material properties, including the shock Hugoniot equation of state (EOS), provides hydrocode modelers with critical information required for accurate modeling of material response to intense loading. In the work reported here we investigate the Hugoniot EOS and Hugoniot elastic limit over the stress range of 1.5–8.0GPa. All experiments were performed on the Army Research Laboratory 102mm bore single-stage light gas gun. Impact conditions were uniaxial and planar to within 1mrad of tilt. Both direct-impact- and shock-transmission-type experiments were performed using velocity interferometry diagnostics to record particle velocity histories with 0.5ns temporal resolution. The shock Hugoniot for 5083-H131 is extrapolated to 50GPa and compared to the previous high pressure results of Hauver and Melani (1973) [Ballistic Research Laboratory December Technical Report No. BRL 2345, 1973] and to prior shock studies of 5083-O aluminum alloy.

Ugo Fano

With the passing of Ugo Fano on 13 February 2001, the Radiation Research Society lost an influential founding member. A broader community dearly misses a great theoretical physicist. Ugo Fano was born a son of Rosa Cassin and Gino Fano (1871-1952), professor of mathematics at Turin, Italy, specializing in differential geometry. Having studied mathematics first at the University of Turin, the younger Fano turned to physics under the influence of his cousin, Giulio Racah (1909-1965), a physicist known for the powerful theory of angular momentum. Then Fano was fortunate to receive postdoctoral training from two giants in modern physics: Enrico Fermi at Rome in 1934-1936 and Werner Heisenberg at Leipzig in 1936-1937. Fano's American career began with pioneering work in 1940-1944 in what was later to be called radiation biology with M. Demerec and others at the Department of Genetics of the Carnegie Institution at Cold Spring Harbor. It is noteworthy that, after a seminar in Rome by P. Jordan on the effects of X rays on genetic material, Fermi had suggested to Fano that the biological action of radiation would be an important and suitable topic for study. Fano's papers in this period concerned chromosomal rearrangements, mutations, lethal effects,more » and genetic effects of X rays and neutrons on Drosophila melanogaster, as well as theoretical analysis of genetic data. His work also included the discovery of bacteriophage-resistant mutants in Escherichia coli, following up earlier studies by Salvador E. Luria. After a wartime effort at the U.S. Army Ballistic Research Laboratory in 1944-1945, Fano joined the staff of the National Bureau of Standards in 1946. Fano's two decades at NBS saw prolific and outstanding contributions to two major areas of research: radiation physics and the basic physics of atoms, molecules and condensed matter. Many of Fano's contributions to radiation physics are seminal to later developments. In 1946, he put forth the first general theory of the yield of ionization in a gas. In 1947, he pointed out the statistical fluctuations of ionization and characterized them by what is now known as the Fano factor. In 1951-1959, he led L. V. Spencer, M. J. Berger and others in developing methods for treating the transport of photons and charged particles in matter. The invention in 1953-1954 of the degradation spectrum for characterizing electrons and other charged particles in matter was especially influential. In 1954, Fano also demonstrated the cavity principle of radiation equilibrium under general conditions. In later years at Chicago, he maintained a keen interest in radiation physics and studied topics such as the behavior of slow electrons in condensed matter, which are produced abundantly by any ionizing radiation. Fano's work after the mid-1950s focused increasingly on basic and microscopic aspects of radiation interactions with matter, including condensed-phase effects on radiation absorption (studied in 1956-1960) and stopping powers of materials (comprehensively reviewed in 1963). He continued for many years to campaign for the use of synchrotron radiation, for which numerous facilities have now been developed worldwide. The numerous, wide-ranging influences of Fano in basic physics and chemistry grew mostly from his years since 1966 at the University of Chicago. Not only did he train approximately 30 Ph.D. students and many postdoctoral fellows, but he communicated regularly with scientists around the world in meetings or by telephone calls, letters and electronic mail, liberally sharing his ideas and incisive insights into scientific matters. This style of 'doing physics' (in Fano's frequently used words) stems from Fermi, who strove to see the essence of knowledge in experimental facts and to tell it to others in simple and unpretentious words. We shall continue to learn much from his five monographs and over 250 papers.« less

Before the ENIAC [weapons firing table calculations

During World War II, the Ballistic Research Laboratory of the US Army was charged with the responsibility of preparing firing tables for the various new weapons under development. The computations required for the preparation of these firing tables were so time-consuming that they overwhelmed the facilities available at the laboratory. In spite of the extensive arrangements the laboratory made with the University of Pennsylvania for assistance, the backlog continued to grow. At one point, more than 100 female students were engaged to carry out firing table calculations. It was to relieve this bottleneck that John W. Mauchly and J. Presper Eckert, two members of the faculty of the Moore School of Engineering, the University of Pennsylvania, proposed the construction of the ENIAC (Electronic Numerical Integrator And Computer), which was funded by the US Army. In this article, I describe the nature of the computations required in the preparation of firing tables and explain the reasons why these calculations were so burdensome.

The early years of aerodynamics ranges, light-gas guns, and high-velocity impact

The age of supersonic flight began at the end of the 19th century when the inventions of smokeless powder and high strength steel enabled an increase in gun velocities to supersonic speeds. However, neither theory nor experiment were available at this time for the science of supersonic flight. The approach being taken then was to record the flight of the body and to compute the forces from its motions, but, unfortunately, unsolved problems in instrumentation stood in the way. The author was assigned the task of solving these problems at the Army's Ballistic Research Laboratories in 1940. His success in this endeavor led to the development of an apparatus, called an “Aerodynamic Range”, for recording the projectile's flight and, hence, determining the aerodynamic forces. World War II had started by this time, and the Aerodynamics Range was put to work immediately measuring the aerodynamic characteristics of gun-fired projectiles, bombs, rockets and some guided missiles. The “cold” war started right after the “hot” war and with it came a new challenge in the form of the InterContinental Ballistic Missile armed with an atomic explosive warhead. Aerodynamic Ranges, which had been built in various laboratories by this time, were put to work on impact tests to determine the lethality of kinetic energy weapons in countering the ICBM threat. In addition, the moon landing program had been started and tests were needed to evaluate the effects of meteorite impact on the lunar surface. Implementing these new programs required a gun capable of launching projectiles at the re-entry and meteoroid velocities of 8 to 10 km/s. The development of a new design of a two-stage high-velocity gun had been started at the Colorado School of Mines, a gun called a “light gas gun” because it used hydrogen as the propellant of its second stage. The author and others continued with its development until a design had been evolved capable of firing projectiles at the required velocities. The gun was then put to work in Aerodynamic Ranges on the assigned tasks of kinetic energy weapon lethality and meteoroid impact.The Early Years paper is an account of the trials and errors in the initial developments of Aerodynamic Ranges and High-Velocity Light Guns and the beginnings of research in high-velocity impact. It is not a formal research paper. Rather, it is an anecdotal account of the events taking place at the starts of these new programs to give the reader a feeling for the ambiance of the times with just enough technology thrown in for credibility. In a sense, telling about the successes and failures of The Early Years belongs with Kipling's verse: “To meet with Triurnph and Disaster and treat these two Impostors just alike”.

Predicted flight performance of base-bleed projectiles

Current Army programs are applying a base-bleed concept to achieve increased range for projectiles. Base bleed is a technique in which low-speed mass is injected into the base region to reduce base drag and extend range. The U.S. Army Ballistic Research Laboratory is developing an engineering computational model capable of predicting the flight performance. The model analyzes three problem elements: a solid propellant gas generator, the effect of injection on the aerodynamic drag, and trajectory computations. Because each element is time dependent, all three must be solved simultaneously. The analysis is based on experimental and numerical data generated for the M864 base-bleed projectile. Navier-Stokes computations for the near wake region have been performed on the Army's Cray X-MP/48 supercomputer. The results were used to correlate base pressure change with injection rate, gas temperature, and Mach number. These results provide critical data for the analysis. The mass generation analysis is combined with the effect of mass injection on base pressure to obtain the projectile base drag at each step of a two-dimensional, point-mass trajectory computation. Computed results are in reasonable agreement with the flight data. Ranges are predicted within 4.2%.

ARMOR ACCEPTANCE PROCEDURE

The Probability and Statistics Branch of the U.S. Army Ballistic Research Laboratory was asked to develop a procedure of acceptance testing for armor packages. Because the available sample sizes were extremely small, standard acceptance plans were inapp..

High velocity penetration of steel targets

Researchers at the U.S. Army Ballistic Research Laboratory (BRL) have conducted a combined experimental and numerical research program in high-velocity penetration aimed at increasing the understanding of penetration mechanics over the striking velocity range between 1.5 and 4 km/s. A judicious combination of ballistic tests and large-scale simulations have been used to evaluate the performance of a family of both monolithic and segmented penetrators against semi-infinite rolled homogeneous armor (RHA). The results of the experimental and numerical programs are discussed.

Aerodynamic characteristics of a family of cone-cylinder-flare projectiles

A systematic study of a number of flare-stabilized projectile geometries has been undertaken at the U.S. Army Ballistic Research Laboratory (BRL). Ten projectile configurations having identical forebodies and a variety of flares were tested in the BRL Aerodynamics Ballistic Range, and the results were compared to numerical computations based on two design codes and a parabolized Navier-Stokes (PNS) code. The design codes, in general, gave good results. The PNS code complimented these results by providing more details on the development of the aerodynamic forces. The results show the drag and stability tradeoffs involved for the different configurations. This information can be used to tailor the flare geometry to meet future mission requirements.

Investigation of Liquid Gun Propellants: Electrical ignition of LGP 1846

AbstractProgress achieved in the study of the electrical ignition of the hydroxylammonium nitrate(HAN)‐based liquid gun propellant LGP 1846 is described. The goal of the work is to develop an igniter system suitable for regenerative liquid propellant guns. Several igniter configurations of the one‐ as well as the two‐stage types designed by the Ballistic Research Laboratory and the Fraunhofer‐Institut EMI‐AFB, have been tested. Voltage and current as well as the pressure histories were recorded. Calculations of electrostatic field distributions discussed here were obtained by a finite element code implemented at Dynamit Nobel. The theoretical analysis yielded alternative electrode designs for future testing. In addition, a specially designed igniter chamber equipped with sapphire windows was used at EMJ‐AFB to study the fundamentals of the electrical discharge by means of high‐speed photography.