Ballistic Model Research Articles

3D pressure-corrected ballistic extrapolation of solar wind speed in the inner heliosphere

Solar wind parameters at different locations in the inner heliosphere can be estimated using various solar wind extrapolation methods. The simple ballistic method extrapolates solar wind parameters from the point of measurement to a chosen heliospheric position by assuming that major solar wind structures are persistent and arrive relatively unaltered to the target position. The method considers the rotation period of the Sun while assuming a constant solar wind speed during radial propagation. We improve the simple ballistic model by considering the interaction between the slow and the fast solar wind with a pressure correction during the propagation. Instead of extrapolating from the position of a single spacecraft, we apply this pressure-corrected ballistic method to 2D speed maps of the solar source surface available from solar coronal models to determine the solar wind speed in the inner heliosphere in 3D, between latitudes of ±50°. We also take into account the effects of the solar differential rotation in our model. Our method is simple and fast, and it can be applied to different source surface datasets. The results of our model are validated with in situ data from the ACE spacecraft. We find that the pressure-corrected ballistic method can give accurate predictions of the solar wind in 3D.

Aircraft turbine fan casing and ballistic fan blade impact: Geometry and material

If the failed fan blade (FB) is not contained in the fan casing (FC) at the time of failure, a catastrophic disaster could follow from the failure of the aircraft's engine turbine. Unfavorable problems including the aircraft malfunctioning, a potential engine shutdown, and even a crash could occur if the detached FB enters the FC. This study employed the Finite Elements Method (FEM) to examine the effects of utilizing Polyether Ether Ketone (PEEK) as an alternative FB material on the FC in order to address this issue. In order to investigate the effects of PEEK and aluminum ballistic FB penetration on FC with thicknesses of 5, 4, 3, and 2 mm at 255 m/s, a FEM ballistic model was developed using the ABAQUS/Explicit modeling system. It was found that during working conditions, none of these FBs could pierce the FC, regardless of thickness. PEEK might be a better alternative, though, as the FC was more obviously deformed by the metal FB. The decision was made to conduct additional analytical validation of the developed FE models. The moment of inertia methodology, a novel approach, was employed. There was a strong correlation between the results of the FE models and the analytical answers. Therefore, it may be said that PEEK is a better material than aluminum for making blade casings.

Effect of modified method based on recoil motion on interior ballistic performance of ultralight high-low pressure artillery

Light gun is of unique application prospect for its low body mass and projectile initial velocity. In order to solve the problem of calculation error caused by the large free recoil velocity of light artillery in traditional interior ballistic model, a more suitable internal ballistic model for ultralight artillery was proposed through the design and test of a light gun, the accuracy of the algorithm was verified. The model described the effect of the recoil motion of the gun on chamber pressure and projectile acceleration travel, which made the calculation result more accurate when the gun mass was lighter. Compared with the experimental data, the errors of the calculation results using the improved algorithm were 2.90 % and 0.33 % respectively, while that using the traditional algorithm were 20.38 % and 10.02 % respectively. At the same time, the extended calculation was carried out to analyze the impact of the buffer device on the interior ballistic performance. The result showed that the lighter the gun, the greater the improvement brought by the buffer device under the same mass and recoil resistance. When the mass of the projectile and the gun was both 3 kg, the resistance of 70 kN could increase the velocity of projectile by 16.2 %. Furthermore, the internal ballistic elements of the traditional algorithm and the improved algorithm were calculated respectively under the same working conditions. It was found that when the mass of the gun is 8.567 times the mass of the bullet, the error of the two algorithms was less than 1 %, and the error increased gradually with the mass ratio of gun and projectile decreasing.

Electronic Shooting Simulator Family "STrIzh": Implementation Levels and Free Software Structure

Development of rifle electronic simulators (i.e. for hand weapons and not using ammunition) is an important task, since the production of any type of small arms according to regulatory documents also requires the production of a simulator to instill aiming and firing skills. A family of electronic shooting simulators "STrIzh" of four levels of implementation: initial, basic, professional and special is described. Structural diagrams of different configurations are given, functional purpose and capabilities of each level of simulators are shown. The initial level allows independent assemble the simulator from publicly available elements (laptop, webcam, weapon layouts, IR LEDs), which can contribute to widespread use both in schools and at home, but is low in accuracy and manufacturabili (requires daily calibration). The basic level also allows independent assemble the simulator, and less publicly available elements (laptop, projector, mockup weapons, laser emitters, FHD camera), which allows to be used both in schools and in DOSAAF structures, and has acceptable accuracy and manufacturability (a weekly calibration is enough, but assembling a mock-up weapon with laser emitters requires adjustments). It is recommended to limit the special level to virtual reality simulators, including a helmet with a smartphone and a mockup of a weapon with its smartphone which also contributes to its public availability and widespread use. The simulator software algorithm should fully support all implementation levels with different configurations and include a multimedia shooting training system. Mathematical models of external ballistics of thrown equipment for Kalashnikov assault rifle, Makarov pistol, hand-held anti-tank grenade launcher 7 products are described in detail, taking into account changes in atmospheric factors (temperature, air pressure, wind force) and dispersion of various types of ammunition. The above review of rifle simulators and their experience revealed the main trends of improvement – use of virtual reality and training not only direct shooting skills, but also training in the eligibility of the use of weapons, safe handling of them and even tactical interaction in the group.

Group-Fusion One-Dimensional Convolutional Neural Network for Ballistic Target High-Resolution Range Profile Recognition with Layer-Wise Auxiliary Classifiers

Ballistic missile defense systems require accurate target recognition technology. Effective feature extraction is crucial for this purpose. The deep convolutional neural network (CNN) has proven to be an effective method for recognizing high-resolution range profiles (HRRPs) of ballistic targets. It excels in perceiving local features and extracting robust features. However, the standard CNN's fully connected manner results in high computational complexity, which is unsuitable for deployment in real-time missile defense systems with stringent performance requirements. To address the issue of computational complexity in HRRP recognition based on the standard one-dimensional CNN (1DCNN), we propose a lightweight network called group-fusion 1DCNN with layer-wise auxiliary classifiers (GFAC-1DCNN). GFAC-1DCNN employs group convolution (G-Conv) instead of standard convolution to effectively reduce model complexity. Simply using G-Conv, however, may decrease model recognition accuracy due to the lack of information flow between feature maps generated by each G-Conv. To overcome this limitation, we introduce a linear fusion layer to combine the output features of G-Convs, thereby improving recognition accuracy. Additionally, besides the main classifier at the deepest layer, we construct layer-wise auxiliary classifiers for different hierarchical features. The results from all classifiers are then fused for comprehensive target recognition. Extensive experiments demonstrate that GFAC-1DCNN with such simple and effective techniques achieves higher overall testing accuracy than state-of-the-art ballistic target HRRP recognition models, while significantly reducing model complexity. It also exhibits a higher recall rate for warhead recognition compared to other methods. Based on these compelling results, we believe this work is valuable in reducing workload and enhancing missile interception rates in missile defense systems.

Simulating droplet distribution characteristics for sprinkler irrigation with a modified ballistic model

The ballistic model, with its high computational efficiency and small test workload, is an effective method to simulate the distribution of spray droplets. It can be employed to solve the problems of oversimplifying the droplet crushing process and motion shape and ignoring the droplet energy characteristics in the equivalent droplet indicator in the existing model assumptions. Based on the law of the motion of sprinkler irrigation water flow, the model assumption of continuous motion and segmental fragmentation of the jet is proposed in the current study. Ellipsoidal droplet shape parameters were introduced to construct the equations of the motion of sprinkler irrigation water flow in the jet and droplet stages, respectively. The critical conditions for large droplet separation and correction drag coefficient for small droplets are defined and solved, and the calculation formulas based on the energy-weighted equivalent droplet indicators were derived. The accuracy of the model was verified using 50PYC, ZY-2, and HY50 nozzles, and the modified model was compared with Fukui’s and Li’s models. The effects of working pressure, nozzle diameter, nozzle elevation angle, and installation height on the droplet landing distance, velocity, and angle at the end of the spray range were investigated. The results showed that: (1) The mean absolute error (MAE) and root-mean-square error (RMSE) of droplet landing distance, velocity, and angle under different working conditions simulated by the modified model were smaller than those obtained using Fukui’s and Li’s models, showing better simulation accuracy. Considering the simulated values of droplet landing distance, velocity, and angle of the 50 PYC nozzle (nozzle diameter of 22 mm and working pressure of 0.35 MPa) as an example, the accuracy of the modified model was improved by 72.86 % and 53.45 % (landing distance), 35.86 % and 70.57 % (landing velocity), 42.10 % and 67.66 % (landing angle) compared with the Fukui’s and the Li’s models, respectively. (2) Fukui’s and Li’s models demonstrate higher accuracy in simulating the droplet landing distance of the ZY-2 nozzle with a smaller nozzle diameter (7 mm) than in simulating the HY50 and 50PYC nozzles; (3) The changes in nozzle operating pressure, nozzle diameter, and nozzle elevation angle exert the greatest effect on the droplet landing distance, landing velocity, and landing angle, respectively. This study provides a novel idea for using the ballistic model to simulate the spray droplet distribution.

Geometrical exponents of contour loops on ballistic deposition model with power-law distributed noise

In this paper, we study geometrical properties of contour loops to characterize the morphology of the porous ballistic deposition model with power-law distributed noise. In this model, rod-like particles with variable lengths instead of homogeneous particles are deposited, the length of each rod, l, is determined by a power-law distribution, P(l)∼l−(μ+1), and μ indicates the power-law strength exponent. The accumulation of rods with different lengths leads to a porous structure. The porous structure is converted into contour loops by using the Hoshen–Kopelman algorithm and the complexity and fractal features of the loops are investigated. On the other hand, the distributions of loops indicating the porosity distribution of the growth rough surfaces are investigated. The fractal dimension of the contour set, d, the fractal dimension of each loop, Df, cumulative distributions exponent of areas, ξ, and the perimeter distribution exponent, τ, are calculated for the investigated porous structures. Our results show that enhancement of μ exponent and appearance of the Gaussian ballistic deposition model leads to reduction of structure porosity and enhancement of contour loops area and perimeter. The fractal dimension of the contour set, and the fractal dimension of each loop increases by enhancement of μ exponent. Distributions of loops and geometrical exponents of contour loops in different μ exponent are determined. The results indicate that the hyperscaling relation and Zipf’s law hold for μ≥μc=3 which power-law distributed noise approaches to Gaussian one.

Physical vapor deposition simulator by graphical processor unit ray casting

This paper presents fast, accurate software for modeling physical vapor deposition systems over irregular surfaces. The model is implemented using graphics processing unit (GPU) ray casting. Applied models are viewed as a cross section of the area of interest. Given evaporation rate, time, and angular profiles in a vacuum system, an iterative time-step approach for calculating deposition profiles is calculated in the GPU architecture following a ballistic modeling approach. Thin-film technologies for the electronics industry will require evaporations on complex surfaces. Depending on the nature of the surface, a uniform thin film across the topology is wanted for various device parameters. The ray casting method is tested against various profiles. The code is freely distributed on GitHub (see https://github.com/adam-r-thomas/PVDS).

Physical modeling of ribosomes along messenger RNA: Estimating kinetic parameters from ribosome profiling experiments using a ballistic model.

Gene expression is the synthesis of proteins from the information encoded on DNA. One of the two main steps of gene expression is the translation of messenger RNA (mRNA) into polypeptide sequences of amino acids. Here, by taking into account mRNA degradation, we model the motion of ribosomes along mRNA with a ballistic model where particles advance along a filament without excluded volume interactions. Unidirectional models of transport have previously been used to fit the average density of ribosomes obtained by the experimental ribo-sequencing (Ribo-seq) technique in order to obtain the kinetic rates. The degradation rate is not, however, accounted for and experimental data from different experiments are needed to have enough parameters for the fit. Here, we propose an entirely novel experimental setup and theoretical framework consisting in splitting the mRNAs into categories depending on the number of ribosomes from one to four. We solve analytically the ballistic model for a fixed number of ribosomes per mRNA, study the different regimes of degradation, and propose a criterion for the quality of the inverse fit. The proposed method provides a high sensitivity to the mRNA degradation rate. The additional equations coming from using the monosome (single ribosome) and polysome (arbitrary number) ribo-seq profiles enable us to determine all the kinetic rates in terms of the experimentally accessible mRNA degradation rate.

Experimental and Computing Methods to Determine the External Surface Temperature of the Small Arms Weapon Systems Barrel

The need to determine the small arms weapon system barrel temperature under a variety of conditions makes modelling and simulation a good alternative to the expensive real tests. Therefore, in a unique way, this paper includes three alternatives to assess the external surface temperature in order to better understand the balance between the chosen calculation method accuracy and the computed time. For numerical simulations, the initial conditions were established based on STANREC 4367 thermodynamic interior ballistic model. The heat transfer was solved for One-Dimensional and Two-Dimensional model using the finite difference discretisation method, with code written in Matlab. The Three-Dimensional model was resolved by finite element analysis method in Ansys. The simulations results are validated by means of the results obtained in case of two real firing scenarios. During the field testing, a new detection method based on shockwaves microphones was used in order to exactly establish the moment of each shoot and to precisely observe the temperature evolution on barrel surface.

On the relative importance of shocks and self-gravity in modifying tidal disruption event debris streams

ABSTRACT In a tidal disruption event (TDE), a star is destroyed by the gravitational field of a supermassive black hole (SMBH) to produce a stream of debris, some of which accretes onto the SMBH and creates a luminous flare. The distribution of mass along the stream has a direct impact on the accretion rate, and thus modelling the time-dependent evolution of this distribution provides insight into the relevant physical processes that drive the observable properties of TDEs. Analytic models that only account for the ballistic evolution of the debris do not capture salient and time-dependent features of the mass distribution, suggesting that fluid dynamical effects significantly modify the debris dynamics. Previous investigations have claimed that shocks are primarily responsible for these modifications, but here we show – with high-resolution hydrodynamical simulations – that self-gravity is the dominant physical mechanism responsible for the anomalous (i.e. not predicted by ballistic models) debris stream features and its time dependence. These high-resolution simulations also show that there is a specific length-scale on which self-gravity modifies the debris mass distribution, and as such there is enhanced power in specific Fourier modes. Our results have implications for the stability of the debris stream under the influence of self-gravity, particularly at late times and the corresponding observational signatures of TDEs.

Scaling limit of the heavy tailed ballistic deposition model with p-sticking

Scaling limit of the heavy tailed ballistic deposition model with p-sticking

Uncertain optimization for initial disturbance of projectile for moving tank based on stochastic programming and deep learning surrogate model

To enhance the hitting accuracy of tank with moving firing, an uncertain optimization method based on stochastic programming is adopted to reduce the initial disturbance of projectile. Firstly, the firing dynamics model of moving tank is modeled to simulate the initial disturbance of projectile. Secondly, the controllable interior ballistic parameters such as projectile structure parameters and propellant parameters are treated as random design variables. The surrogate model for the firing dynamics model of moving tank is constructed by using the neural network based on deep learning. The uncertain optimization problem is transformed into a deterministic optimization problem by stochastic programming method. Then multi-objective genetic algorithm is adopted to settle optimization model, and reasonable design interval of random design variables is obtained. Finally, a six-degree-of-freedom rigid external ballistics model is used to establish a hitting accuracy evaluation model of moving tank based on interval uncertainty analysis. Through this model, the effectiveness of the optimization method is demonstrated.

An internal ballistic model of electromagnetic railgun based on PFN coupled with multi-physical field and experimental validation

To accelerate the practicality of electromagnetic railguns, it is necessary to use a combination of three-dimensional numerical simulation and experiments to study the mechanism of bore damage. In this paper, a three-dimensional numerical model of the augmented railgun with four parallel unconventional rails is introduced to simulate the internal ballistic process and realize the multi-physics field coupling calculation of the rail gun, and a test experiment of a medium-caliber electromagnetic launcher powered by pulse formation network (PFN) is carried out. Various test methods such as spectrometer, fiber grating and high-speed camera are used to test several parameters such as muzzle initial velocity, transient magnetic field strength and stress-strain of rail. Combining the simulation results and experimental data, the damage condition of the contact surface is analyzed.

Fast Then Slow: Choice Revisions Drive a Decline in the Attraction Effect

We explore the nature and robustness of the attraction effect. The attraction effect can be seen as a persistent bias or as the result of heuristics that may not persist upon reflection. We provide robust experimental evidence that the attraction effect first rises and then falls over time when participants are incentivized to make a quick choice they can later revise. Participants in two experiments under continuous time pressure make choices among options with the aim to maximize an objective, measurable value. We find that participants disproportionately favor the asymmetrically dominant option in the first seconds and then revise their choices until the effect disappears or is significantly reduced. The effect survives only in the special and often studied case of indifference among options. We develop a tractable extension to the multiattribute linear ballistic accumulator model to allow for choice revisions. That model explains how choice revisions reduce context effects. We estimate its parameters at the individual level and document differences between fast and slow participants that also play a role in explaining the rise-and-fall pattern in the attraction effect. We extend the analysis to similarity and compromise effects. We find a very small similarity effect, which does not exhibit any dynamics, and a significant reverse compromise effect displaying a rise-and-fall pattern. Our findings, although limited to objective-value tasks, are consistent with context effects being short-term heuristics that can be superseded by more reflective cognitive strategies when decision makers have time and incentive to do so. This paper was accepted by Manel Baucells, behavioral economics and decision analysis. Funding: This work was supported by the Institut National de la Recherche Agronomique [Grant SAE2 Jeune Chercheur 2017]. Supplemental Material: The data files and online appendix are available at https://doi.org/10.1287/mnsc.2023.4874 .

A Bright First Day for Tidal Disruption Events

Stream–stream collision may be an important prepeak energy dissipation mechanism in tidal disruption events (TDEs). We perform local three-dimensional radiation hydrodynamic simulations in a wedge geometry including the gravity to study stream self-crossing with an emphasis on resolving the collision and following the subsequent outflow. We find that the collision can contribute to prepeak optical emissions by converting ≳5% of the stream kinetic energy to radiation, yielding prompt emission of ∼1042−44 erg s−1. The radiative efficiency is sensitive to stream mass fallback rates and strongly depends on the downstream gas optical depth. Even for a sub-Eddington (10%) mass fallback rate, the strong radiation pressure produced in the collision can form a local super-Eddington region near the collision site, where a fast, aspherical outflow is launched. A higher mass fallback rate usually leads to more optically thick outflow and lower net radiative efficiency. For , the estimated photosphere size of the outflow can expand by 1–2 orders of magnitude, reaching ∼1014 cm. The average gas temperature at this photospheric surface is a few × 104 K, roughly consistent with inferred prepeak photosphere properties for some optical TDEs. We find that the dynamics is sensitive to the collision angle and radius, but the radiative efficiency or outflow properties show more complex dependency than is often assumed in ballistic models.

Muzzle flow field characteristics of underwater sealed launch system under different projectile shapes

The underwater sealed launch is one of effective launch technologies for enhancing the velocity of underwater vehicle and also for achieving better interior ballistic performance. However, the underwater muzzle flow field based on this sealed technology is a major consideration as it decides initial kinetic stability and subsequent shooting accuracy. Hence, this study establishes a comprehensive model involving in a modified sealed interior ballistic model, muzzle multiphase turbulent flow model and supercavitation model due to high-velocity moving vehicle, and mainly investigates the effect of the vehicle shapes on the underwater sealed muzzle field. An experiment for the muzzle field of underwater sealed launch is also carried out using a 12.7 mm-caliber launch device and water tank. Comparisons on flow patterns of muzzle field and expansion displacements of Taylor cavity on computational results are done with experimental studies, and a reasonable match has been obtained in these comparisons. The results show that the gas sealed in the launch barrel firstly injects into the water forming an initial Taylor cavity once the sealed device is broken. Then, the propellant combustion-gas just with high pressure and high temperature injects into the water with the moving vehicle. Consequently, a complicated interaction effect between these two types of gases and high-density water takes place, generating complicated shock wave phenomena in the muzzle field. Different vehicle shapes can affect the formation of the shock waves and expansion characteristics of Taylor cavity in the water. Eventually, the diameter of the Mach disk is always the largest for the cylindrical underwater vehicle and the axial pressure fluctuation for the vehicle with a cavitator are most significant with a lowest temperature field due to strong gas-liquid interaction.

Effects of the transversely nonuniform plasma density in a blowout regime of a plasma wakefield accelerator.

We present an analytical study on the effects of the transverse plasma gradient in the blowout regime of a plasma wakefield accelerator. The analysis departs from a simple ballistic model of plasma electrons and allows us to derive a complete analytic solution for the pseudopotential and, consequently, for the wakefield. We demonstrate that the transverse plasma gradient modifies the bubble shape and affects the wakefield; namely, the dipole plasma gradient results in a dipole component of the wakefield. Analysis suggests that, despite the asymmetry, the instability due to the fixed transverse plasma gradient is unlikely, as the total wakefield has a single stable point inside the bubble. The only effect that occurs is the shift of the electromagnetic center. We point out that random fluctuation of the transverse plasma gradient could become an issue.

Research on Vibration Control of Paired Inclined Nozzles Dynamic Coupled Tubes

The barrel vibrates violently, which will lead to a serious drop in shooting accuracy. To solve this issue, a barrel vibration control method of the paired oblique nozzle dynamic couple is proposed. A pair of inclined nozzle devices are designed on the barrel to fully use the gunpowder gas energy in the chamber during the shooting process. A dynamic couple is generated to balance the turning moment of the barrel weapon. Simultaneously, the recoil force is reduced by exporting the gunpowder gas in the chamber. Therefore, the vibration of the barrel is reduced. Firstly, the internal ballistic two-phase flow model including the gas transient flow model in the vibration control device is modelled based on the internal ballistic theory of two-phase flow. Secondly, the numerical simulation of the weapon launching process is carried out. Thirdly, the rigid-flexible coupling firing dynamics modelling and simulation research is conducted on a 30mm chain gun equipped with a paired oblique nozzle dynamic couple vibration control device. At last, the effects of the device on the continuous firing vibration control of barrel weapons are analyzed. The results show that the vibration reduction efficiency of the inclined nozzle is better than that of the vertical nozzle and the horizontal nozzle. When the angle of the inclined nozzle is 30°, the barrel shows the highest vibration reduction efficiency. The vibration reduction efficiency of each vibration characteristic is 39.2%, 17.1%, 44.8%, and 48.9%, respectively.

Research on Ballistic limit model for a typical 93W ball-Q235 steel plate projectile target system

A representative and most commonly used ballistic target system consisting of a 93W ball and Q235 steel plate is investigated for its ballistic limit fast calculation engineering model. The basic data on the material of the projectile target system was obtained through quasi-static compression tests on the mechanical properties of 93W ball and Q235 steel plate materials. Using a Φ12.7mm ballistic gun and the ten shot v50 ballistic limit method, tests were carried out with 93W balls positively penetrating Q235 steel target plates and v 50 was obtained for 3g of 93W balls penetrating 6mm and 8mm thick Q235 steel plates respectively. Based on the Autodyn platform, a numerical simulation model of a 93W ball intruding through a Q235 steel target plate was established and the accuracy of the simulation model was verified using test data. On this basis, the range was extended to obtain v 50 for a total of 34 working conditions with 93W ball masses between 1 and 6g and Q235 steel target plate thicknesses between 2 and 12mm, and the v 50 engineering calculation model for 93W ball intrusion into Q235 steel plate was obtained by multiple linear regression. Comparative analysis with other representative v 50 engineering models shows that the resulting v 50 calculation model has a greater range of applicable speeds, higher accuracy and greater practicality. The results of the research can provide basic methods and tools for the design of warhead power, target protection, and the assessment of the destructive effectiveness of weapons and ammunition.