Showing papers on "Projectile published in 1991"

Operational characteristics of the thermally choked ram accelerator

Abstract: Operational characteristics of the thermally choked ram accelerator, a ramjet-in-tube device for accelerating projectiles to ultrahigh velocities, are investigated theoretically and experimentally. The projectile resembles the centerbody of a conventional ramjet and travels through a stationary tube filled with premixed gaseous fuel and oxidizer at high pressure. The combustion process travels with the projectile, its thermal choking producing a pressure field which results in thrust on the projectile. The results of experiments with 45-75 gm projectiles in a 12.2 m long, 38 mm bore accelerator, using methane-based propellant mixtures, are presented in the velocity range of 1150-2350 m/s. Acceleration of projectiles with staged propellants and transitions between different mixtures are investigated and the velocity limits in several propellant mixtures are explored. Agreement between theory and experiment is found to be very good.

Shooting simulating process and training device

Abstract: A user friendly shooting simulating process and training system are provided to more accurately and reliably detect the impact time and location in which a projectile shot from a shotgun, rifle, pistol or other weapon, hits a moving target. Desirably, the shooting simulating process and training system can also readily display the amount by which the projectile misses the target. The target impact time is based upon the speed and directions of the target and weapon, as well as the internal and external delay time of the projectile. In the preferred form, the training system includes a microprocessor and special projectile sensing equipment, and the targets and projectiles are simulated and viewed on display screens.

Experimental investigation of ram accelerator propulsion modes

Abstract: Experimental investigations on the propulsive modes of the ram accelerator are reviewed in this paper. The ram accelerator is a ramjet-in-tube projectile accelerator whose principle of operation is similar to that of a supersonic air-breathing ramjet. The projectile resembles the centerbody of a ramjet and travels through a stationary tube filled with a premixed gaseous fuel and oxidizer mixture. The combustion process travels with the projectile, generating a pressure distribution which produces forward thrust on the projectile. Several modes of ram accelerator operation are possible which are distinguished by their operating velocity range and the manner in which the combustion process is initiated and stabilized. Propulsive cycles utilizing subsonic, thermally choked combustion theoretically allow projectiles to be accelerated to the Chapman-Jouguet(C-J) detonation speed of a gaseous propellant mixture. In the superdetonative velocity range, the projectile is accelerated while always traveling faster than the C-J speed, and in the transdetonative regime (85–115 % of C-J speed) the projectile makes a smooth transition from a subdetonative to a superdetonative propulsive mode. This paper examines operation in these three regimes of flow using methane and ethylene based propellant mixtures in a 16 m long, 38 mm bore ram accelerator using 45–90 g projectiles at velocities up to 2500 m/s.

Analysis of induction-type coilgun performance based on cylindrical current sheet model

Abstract: A method which is based on a cylindrical current sheet model for the analysis and design of induction-type coilguns is presented. The work starts with a derivation of closed-form formulae which relate the dimensions of the gun to the performance expressed in terms of propulsive and local maximum forces on the projectile, power factor and efficiency of the system, thermal stress of the projectile armature, distributions of the flux density around the launcher, and the system parameters in a multisection coilgun. A numerical example is given. >

Fragmentation of gold projectiles: From evaporation to total disassembly

Abstract: We have studied the fragmentation of Au projectiles interacting with targets of C, Al and Cu at an incident energy ofE/A=600 MeV. The employed inverse kinematics allowed a nearly complete detection of projectile fragments with chargeZ≧2. The recorded fragmentation events were sorted according to three observables, the multiplicityMlp of light charged particles, the largest atomic numberZmax within an event, and a new observable,Zbound, representing the sum of the atomic numbersZ of all fragments withZ≧2. Using these observables, the impact parameter dependence of the fragmentation process was investigated. For all three targets, a maximum mean multiplicity of 3 to 4 intermediate mass fragments (IMFs) is observed. The corresponding impact parameters range from central collisions for theC target to increasingly peripheral collisions for the heavier targets. It is found that the correlation between the IMF multiplicity andZbound, extending from evaporation type processes (largeZbound) to the total disassembly of the projectile (smallZbound), is independent of the target nucleus. This universal behaviour may suggest an — at least partial — equilibration of the projectile fragment prior to its decay.

Measurement of post-collision interaction effects for p on Ne collisions

Abstract: The authors have studied the post-collision interaction distortion of the Ne K-L2.32(1D2) Auger electron line excited by proton bombardment in the energy range 0.7-2.0 MeV. A systematic study of both the bombarding energy and the observation angle dependence has been performed for the first time. They have found the effect to be most pronounced at 0' observation angle and at the bombarding energy where the projectile and the outgoing Auger electron have about the same velocity. The results are in a reasonable agreement with theories which assume PCI between the Auger electron and the outgoing projectile.

The A1200 projectile fragment separator

Abstract: A beam analysis device, the A1200, has been constructed at the National Superconducting Cyclotron Laboratory (NSCL) for routine cyclotron beam analysis. This device can also be used to separate radioactive beams produced by projectile fragmentation. Since the A1200 begins the K1200 cyclotron beam lines, radioactive ions can be delivered to any experimental device. The details of the mechanical and optical designs are presented. In addition some of the planned experiments with the separated radioactive beams are discussed.

Muzzle brake and flash hider

Abstract: An improved muzzle brake having a generally upward opening void from which escaping gases create a downwardly directed reaction force and a sloping face on which the propelling gases collide and expand and deflect to either side and upward of the muzzle brake to defeat the natural tendency of the muzzle of a weapon to climb and drift. Below the generally upward opening void, within the floor of the bore of the muzzle is a venturi trough in which a lowered pressure region of propelling gases is created by the high speed passage of the propelling gases down to the bore of the muzzle brake. This lowered pressure region within the venturi trough is still in excess of the environmental pressure exterior of the muzzle brake so that gases within the venturi trough escape through channels directed downwardly and to the left and right of the projectile path. Gas escaping through these downward, left and right deflected channels is adjustable in flow so that any tendency of the weapon to drift left or right or to move downwardly may be compensated for. The muzzle brake has a structural shape which accommodates it to be fitted within a government issued flash hider. Once so housed within the flash hider, further modification is made to introduce retrojet gas escape channels through the walls of the flash hider into the bore through which the projectile and its propelling gases pass. Propelling gases escaping through these rearwardly directed retrojet channels offset the recoil of the weapon. By arraying these retrojet channels, a balanced set of reaction forces is derived which tends to offset transverse movement of the muzzle of the weapon.

The relationship between mechanisms of wounding and principles of treatment of missile wounds

Abstract: Determinants of the wounding effects of a metallic projectile include the velocity, mass, shape, and stability of the missile, and whether it tumbles, deforms, or fragments within the body. The velocity, mass, shape, and stability influence its capability to penetrate through the skin, and the other factors influence the depth and volume of the wound. The energy lost into the tissues (kinetic energy deposition) is a greater determinant of potential wound volume than is the striking velocity, even though, because K.E. = 1/2 MV2, the potential striking K.E. is more strongly influenced by velocity than mass. The actual size and shape of the wound is influenced by tumbling, deformation, and fragmentation of the projectile and by the characteristics of the tissues and organs contacted. The pulsating temporary cavitation resulting from the passage of a high-velocity projectile produces blunt trauma that extends beyond the tissue actually contacted by the missile. The pulsation of the temporary cavitation with resulting strong negative pressure components permits contamination of the entire wound track of a perforating wound, with entrance of external contaminants from both the exit and the entrance sites. The extent and type of treatment required is determined more by the tissues and organs injured than by the characteristics of the wounding agent. Although extremity wounds from high-velocity projectiles may heal uneventfully, surgical exploration is indicated whenever there is a possibility of subfascial penetration, and obviously devascularized tissue should be excised. In circumstances in which contaminated devascularized tissue cannot be excised promptly or adequately, prophylactic topical antibacterial therapy (such as mafenide aqueous spray, which can penetrate through devascularized tissue) may prevent otherwise lethal infection.

Settable electronic fuzing system for cannon ammunition

Abstract: In an ammunition fuzing system, a fuze setter is inductively coupled with an electronic fuze incorporated in the projectile of an ammunition round being fed to a rapid-fire cannon to transmit power supply charging energy and fuze-setting data thereto. A detonation counter is incremented at a high counting rate to accumulate a projectile flight time count indicative of the fuze-setting data. A conformation signal is transmitted to the fuze setter for determination that the flight time count acceptably corresponds to the setting data. Upon projectile launch, the detonation counter is decremented at a low counting rate and functions the projectile warhead when decremented to zero.

Design and performance of a multi-stage cylindrical reconnection launcher

Abstract: A multistage launcher was designed and assembled by stacking six coil assemblies end-to-end in a support housing which also aligns the system. Each coil is powered by its own capacitor bank which is triggered when an optical sensor in each stage determines that the projectile is in the firing position. The induction launch technology is successfully demonstrated for multistage systems. A 5 kg projectile can be accelerated from 12 m/s to 335 m/s with an average of 200 kJ stored in each of six stages. Calculations of launcher performance with the digital simulation code, WARP-10, are in good agreement with experiments. >

Projectile having plural rotatable sections with aerodynamic air foil surfaces

Abstract: Aerodynamical air foil surface and subsurface expressions and/or impressions of varied geometrics, angles of attack, heights and depths, comprising part of a projectile surface itself to create McClain effect molecular friction/pressure/temperature reaction flight control surfaces which automatically achieve in all fluids and velocities of flight self-stabilizing spin and rotation, increased height of trajectory with corresponding enhancement of range and distance, kinetic energies, inducing smooth laminar boundary layer flows, substantially decreasing drag effects, synergistically combined to constitute a major technological improvement in performance of all projectiles. Projectile having plurality rotatable sections with aerodynamic air foil surfaces provides self-stabilized spin projectile with sections rotating in opposite directions.

Universal projectile ammunition

Abstract: Ammunition for a riot gun with a projectile of universal application. The projectile (5) has a fluted end (40), with an internal cavity (47), which permits varied sleeves (7) with a fluted throughbore (57) to be used with varied nose inserts to define the type of ammunition desired, for example, a non-shattering flat nose (9) shatterable ceramic cover (117), tear gas nose (200), or the like. The projectile, sleeve and nose are insertable into a shell casing (3) with a projectile propellant (77).

Single wall penetration equations

Abstract: Five single plate penetration equations are compared for accuracy and effectiveness. These five equations are two well-known equations (Fish-Summers and Schmidt-Holsapple), two equations developed by the Apollo project (Rockwell and Johnson Space Center (JSC), and one recently revised from JSC (Cour-Palais). They were derived from test results, with velocities ranging up to 8 km/s. Microsoft Excel software was used to construct a spreadsheet to calculate the diameters and masses of projectiles for various velocities, varying the material properties of both projectile and target for the five single plate penetration equations. The results were plotted on diameter versus velocity graphs for ballistic and spallation limits using Cricket Graph software, for velocities ranging from 2 to 15 km/s defined for the orbital debris. First, these equations were compared to each other, then each equation was compared with various aluminum projectile densities. Finally, these equations were compared with test results performed at JSC for the Marshall Space Flight Center. These equations predict a wide variety of projectile diameters at a given velocity. Thus, it is very difficult to choose the 'right' prediction equation. The thickness of a single plate could have a large variation by choosing a different penetration equation. Even though all five equations are empirically developed with various materials, especially for aluminum alloys, one cannot be confident in the shield design with the predictions obtained by the penetration equations without verifying by tests.

Two-centre effects in ejected-electron spectra from ionization of helium atoms in collisions with fast, fully stripped ions

Abstract: Ajoint experimental and theoretical study ofthe double-differential ~ro~~~eftions (DOCS) for ejection of electrons from helium by 1.00 and 1.84 MeVamu-' pi, Hez*, C6* and On+ is presented. Electron-emission angles from 20' to 160' are surveyed, and the electron energies range from 4 to 25OOeV. Single-differential and total cross sections, obtained hy integrating the DDCS over angle and electron energy, are also presented. Large departures from the q2 dependence (where q is the projectile charge) predicted by the first Born approximation are observed in the cross sections. The deviations, which are seen to increase with projectile charge. are discussed and compared with calculations, using the first Born approximation and a caotinuum-distorted-wave eik~nal-ioitial-itate model. It is concluded that the deviations are due to the simultaneous effect of the projectile and residual target fields, thus indicating that two-centre effects are important in the electron emission.

Quantum-mechanical impulse approximation for single ionization of hydrogenlike atoms by multicharged ions

Abstract: A quantum-mechanical approximation is developed for ionization of one-electron targets by charged-ion impact. The model is based on the nonrelativistic distorted-wave formalism valid for impact velocities larger than the electron orbital velocity in the initial state. The exact impulse wave function is used to describe the initial state, thus incorporating the projectile potential to all orders. The final state is represented by a product of continuum Coulomb wave functions around both centers, providing the correct asymptotic conditions and the projectile and target cusps. The theory is thought to be valid for large projectile charge, even larger than the ion velocity. The impulse approximation developed here is expensive in computing time, but it is probably one of the few models to deal with high projectile charges. Double-differential cross sections are computable in the forward and backward ejection angles. Comparisons with the experiments in different regions of interest are presented, including the binary sphere, capture to the continuum cusp, ridge electrons, and backward ejection angles. The theory proves to be quite successful, and it does not seem to deteriorate with increasing projectile charge.

Exploratory development of the reconnection launcher 1986-90

Abstract: The exploratory development phase for the reconnection launcher is summarized. This is an induction launcher which features a contactless, solid armature with either flat-plate or cylindrical geometry. The strategy for successful design is discussed, emphasizing the way the issues of ohmic heating and high-voltage requirements for high velocity were resolved. The indispensable role of a fast-running, mesh-matrix code is stressed. The three multistage launcher are described. One of these achieved a muzzle velocity of 1 km/s with a 150 gram flat-plate projectile. The other two have launched cylindrical projectiles at 335 m/s, one with relatively heavy projectiles of 5 kg, the other with relatively light ones of 10 g. The cylindrical projectile scan be spin-stabilized prior to launch for improved flight. The potential of this technology for earth-to-orbit launch of small artificial satellites is outlined. >

Deviations from Rutherford backscattering for Z = 1, 2 projectiles

Abstract: In a previous paper, an analytical expression for the center of mass kinetic energy, E nr , for departure from Rutherford backscattering was obtained and applied to both proton and 4 e projectiles. This paper further explores the consequences of deviations from Rutherford backscattering, specifically for the charged particle projectiles, Z = 1, 2. In the original model there was no dependence on the nature of the projectile. In this paper, it is shown through the use of both data and optical model calculations that there are two clearly discernable projectile effects, namely an increase in E nr as the projectile charge increases and a less prounounced increase in E nr for the heaviest of the isotopes in each of the two charge groups. It is then demonstrated how these two effects can be accounted for in terms of the mass and charge of the projectile, without changing either the model parameters or results of the previous paper.

Roll angle determination

Abstract: The invention relates to an arrangement for determining the roll angle of a rotating projectile, shell, missile or the like as it leaves the barrel or launch tube. The projectile comprises a magnetised part (2) with a known polarisation direction, and the barrel or launch tube is provided with two pairs of windings (9, 10) mounted at the very front of the muzzle bell of the barrel in such a way that a voltage is induced in the windings when the projectile passes the mouth, and an evaluation unit (17) is designed to calculate, with the aid of the voltage signals, the roll angle position of the projectile upon firing.

Projectile Penetration in Granular Soils

Abstract: Results from centrifuge and 1-g model tests of projectile penetration into granular soils are described. Solid spherical projectiles in four calibers were fired into uniform samples of dry sand at approximately 305 m/s. Comparison to full-scale test results verified the suitability of the centrifuge testing technique for this type of problem. Power relationships between projectile penetration depth and projectile mass-to-area ratio are developed. Statistical analyses show that these functions describe the combined 1-g and centrifuge test results with a high degree of accuracy. Test results are compared to predictions of penetration depth based on Young’s equation. Suggestions for improvements in Young’s equation are made, including elimination of an arbitrary mass-scaling factor, use of a soil description based on physical properties of the soil, and use of a soil-specific exponent with the projectile mass-to-area ratio.

Railgun performance with a two-stage light-gas gun injector

Abstract: Results obtained with the HELEOS (hypervelocity experimental launcher for equation of state) railgun, which uses a two-stage light-gas gun (2SLGG) as an injector, are presented. The high-velocity 2SLGG injector preaccelerates projectiles up to approximately 7 km/s. The high injection velocity reduces the exposure duration of the railgun barrel to the passing high temperature plasma armature, thereby reducing the ablation and subsequent armature growth. The 2SLGG also provides a column of cool, high-pressure hydrogen gas to insulate the rails behind the projectile, thereby eliminating restrike. A means to form an armature behind the injected projectile has been developed. In preliminary tests, the third-stage railgun has successfully increased the projectile velocity by 1.35 km/s. Extensive diagnostics have been used to determine the behavior of the armature and track the launcher's performance. Insome cases, velocity increases in the railgun section have been achieved, which are in close agreement with theoretical predictions, whereas in other experiments deviations from theoretical have been observed. The reasons for and implications of these results are addressed. Recent tests are reported. >

Gas powered weapon having shearable diaphragm member

Abstract: A weapon system which utilizes pressurized gas to propel a projectile from a barrel and which utilizes a shearable diaphragm member to permit the pressure of gas in the weapon to increase to a selected point before the gas propels the projectile from the barrel.

Segmented projectile with de-spun joint

Abstract: A projectile which would ordinarily be a spinning artillery shell is segmented so that the forward segment can be deflected relative to the rear segment for aerodynamic directional corrections in flight. Fins provide the projectile spin and a motor in the rear segment rotates an angle drive means with a velocity equal and opposite to the rotation of the rear segment, so that the angle drive means can establish an angle which has a fixed orientation on an earth coordinate reference frame despite the spinning of one or both portions of the projectile. Ground or sea-based radio and radar communications or an on-board roll reference system continuously communicates with the projectile, informing it of its own rotation rate and providing command signals for the nose deflection needed to establish the proper real-time trajectory correction. The weight, weight distribution, and configuration of the aerodynamic surfaces of each of the segments are coordinated such that the net lift vector substantially aligns with the center of mass to minimize in-flight torque forces at the joint.

Projectile with interiorly weighted flow passage insert

Abstract: A football-like projectile having a central longitudinal bore includes a weighted insert in the bore to concentrate the weight of the projectile interiorly of the ball about the longitudinal axis. The insert is provided with a longitudinal flow passage to permit air flow hrough the insert and the bore when the ball is in flight.

Projectile having a matrix of cavities on its surface

Abstract: An improved aerodynamic surface for the exterior of vehicles moving through a gas and vehicles employing such improved surfaces. The objectives of employing such improved surfaces are reduced air resistance and increased lift. The improved surface comprises a series of dimples or depressions formed into the portions of the surface of the vehicle. The improved surface is most beneficially located either at a leading edge, where the vehicle first cleaves the pool of air through which it is traveling, or on vehicle surfaces which tend to move the air pool to accommodate the presence of the vehicle itself or on vehicle surfaces to which the designer wishes to provide a lift function. Wings, ailerons and rudder surfaces are examples of surfaces to which a lift function is most applicable. The vehicle may be of the nature of an automobile, an airplane, a rocket or missile or a projectile fired from a gun. The invention is also applicable to the internal surface of pipes for conveying fluid.

Experimental results from CEM-UT's single shot 9 MJ railgun

Abstract: A 10-m-long, 90-mm bore railgun has been designed and fabricated. During the test program, a number of solid armatures and projectile packages have been tested in a 50-m-deep vertical test range. The experiments are powered by six homopolar generator (HPG) charged inductive stores, sequentially staged to provide the desired acceleration profile. Prior to testing, computer simulations are run to determine the preferred current profile and predict system performance. During projectile flight, high-speed films, X-rays, muzzle volts, and velocity/acceleration profiles are recorded along with power supply operating parameters. Postshot diagnostics include bore wear analysis and armature and target recovery. Comparisons of predicted and recorded shot performance are also made. On selected tests, an energy balance is performed to determine efficiencies of the various components. A summary of all 90-mm gun shots is presented along the critical data collected from selected tests. >

Magnetohydrodynamic wave drag

Abstract: A calculation is made of the energy loss by emission of shear‐Alfven and slow magnetoacoustic waves by a perfectly conducting solid spherical projectile moving with uniform velocity through an ideal magnetoplasma.

RAILGUN PERFORMANCE WITH A TWO-STAGE LIGHT-GAS GUN INJECTOR*+ R. S. Hawke and A. R. Susoeff, Lawrence Livermore National Laboratory, Livermore, CA

Abstract: This paper summarizes the results obtained with the HELEOS railgun which uses a two-stage light-gas gun (2SLGG) as an injector [ 11. The high velocity 2SLGG injector pre-accelerates projectiles up to -7 km/s. The high injection velocity reduces the exposure duration of the railgun barrel to the passing high temperature plasma armature, thereby reducing the ablation and subsequent armature growth. The 2SLGG also provides a column of cool, high pressure hydrogen gas to insulate the rails behind the projectile, thereby eliminating restrike. A means to form an armature behind the injected projectile has been developed. In preliminary tests, the third stage railgun has successfully increased the projectile velocity by 1.35 km/s. Extensive diagnostics have been used to determine the behavior of the armature and rrack the launcher’s performance. In some cases, velocity increases in the railgun section have been achieved, which are in close agreement with theoretical predictions, whereas in other experiments deviations from theoretical have been observed. The reasons for and implications of these results are addressed. Recent tests are reported.