Supersonic Projectile Research Articles

Prediction of sound around shooting ranges

The assessment of sound around shooting ranges can be challenging. On one hand, methods to predict the sound levels around shooting ranges are described in the standard ISO 17201 "Acoustics - Noise from shooting ranges". It consists of measurement and calculation methods to determine the source strength from muzzle blasts or explosives and supersonic projectiles, as well as a method for the sound propagation. The methods to calculate the muzzle and projectile sound are being updated this year. On the other hand, challenges remain to measure the source strength from weapons with a large caliber and the sound emitted from shooting facilities with a complex geometry. These issues and its approach are illustrated. Also, a noise management method is described, as a pilot study, that allows for a flexible use of different weapons for a given period of time, typically a year.

Multi-fidelity multidisciplinary meta-model based optimization of a slender body with fins

Multidisciplinary design optimization (MDO) involving aero-elastic simulations still proves challenging for computational cost. This paper proposes a competitive cost-effective multi-fidelity MDO strategy based on two ideas. Firstly, a new multi-fidelity fluid-structure interaction model (MF-FSI) is proposed, allowing a considerable saving of the FSI simulation cost. Secondly, the optimization cost is further reduced using a meta-model approximation of the MF-FSI computations during optimization. Therefore, the MF-FSI model is validated on an experimental case of supersonic projectile fins. Then, it is combined with a meta-model-based optimization strategy (MBO) to improve the fins design. The constrained multi-objective problem aiming to maximize the lift-to-drag ratio and minimize the fin mass is solved using both high-fidelity (HFMDO) and multi-fidelity (MFMDO). The results showed that the proposed MFMDO strategy could produce the same optimal solutions as the HFMDO one with a 52% lower cost.

Формування вихідних даних для вирішення задач маршового розрахунку надзвукового обтікання ракет різного компонування

This paper gives a general overview of components and layouts used in supersonic rockets of different purposes. The rocket layout is specified as a structure and a set of components (a wing, a rudder, a stabilizer, a destabilizer, and a superstructure) arranged along the rocket structure. The goal of this work is to develop a unified approach to specifying the shape parameters of rocket layouts regardless of the rocket type. For complex-shape rocket layouts, the paper proposes an approach in which the shapes of the rocket structure and the additional components installed thereon are specified independently. The additional components of the rocket layout are bound to the rocket structure using operation parameters. The use of the operation parameters binds each additional component of the rocket layout to the rocket structure, thus offering a unified method for specifying the geometrical parameters of variously shaped rocket layouts. This approach is developed towards more complex shapes of rocket layout elements arbitrarily placed on rocket structures. The outside shape of each rocket component is specified in a Cartesian system of coordinates rigidly bound thereto. A unified approach to specifying the outside shape of various rocket components is presented. According to the general scheme of specifying the geometrical parameters of rocket layout components, they are specified by three methods: analytically, by plan shape, and by plan shape with board and end chord profiles. To describe the outside shape of a component, the specification method and the number and the values of its key parameters are specified. To specify rocket layout input data, one has to fix the number of additional components to be installed on the rocket structure. For each layout component, the parameters that define its shape, location on the rocket structure, and deflection angle are specified. To each layout component there corresponds an input data set of its own. The set consists of parameters that define the shape of the component and parameters of its operation as a part of the layout. A standard input data file for specifying rocket layout shapes is configured.

Selected Papers from 4th National Aerospace Propulsion Conference NAPC 2022

The National Aerospace Propulsion Conference (NAPC) is a national conference dedicated to aerospace propulsion technologies. Two erstwhile popular conference series, the National Propulsion Conference (NPC) and the National Conference on Air-Breathing Engines (NCABE) were merged to result in NAPC. This biennial conference is intended to bring together the entire propulsion community spanning the industry, academia and the research labs nationwide. The aerospace propulsion-centred conference is considered an ideal opportunity to showcase one’s research activities with peers and foster future collaborations through networking. The 4th edition of the conference, NAPC-2022, comprised a keynote lecture, several topical invited lectures and presentations of contributed papers in parallel sessions. This special issue contains eight manuscripts selected based on peer-reviews of selected papers presented during the conference. The manuscripts broadly cover several aspects pertaining to aerospace propulsion that includes airbreathing engine components such as intakes, compressors, combustors and nozzles. From the rocket propulsion (non-airbreathing), there are papers that investigate the rocket motor grain port alignment and another paper on the heat transfer characteristics of a supersonic rocket nozzle.

Laser interferometer measurement and reconstruction of supersonic projectile acoustic pressure fields

Sensing acoustic fields with a laser interferometer offers several advantages over conventional techniques: the probe beam does not disturb the medium in which it operates, the interferometer optics can be placed far from the source, and interferometry typically has a wider bandwidth than microphones. These advantages are particularly useful in situations where precise measurements of high-amplitude shock-generating sources are required. In this work we use a laser interferometer to study the generation and propagation of shock wave signatures of ballistic projectiles. A laboratory experiment was conducted to collect interferometer data from a variety of supersonic projectiles over a range of standoff distances. Simultaneously-captured microphone data is compared to the interferometer measurements, and techniques for inversion and reconstruction of the sound pressure field are discussed.

A photographic analysis of Mach wave radiation from a rocket plume

At 7:30 AM on October 6, 2020 Space-X launched a Falcon-9 rocket from pad 39A at Kennedy Space Center. Photographer Trevor Mahlmann had positioned his camera in the location where the rocket would pass in front of the rising sun and took a series of images of that encounter. These images are visually stunning, but they are also scientifically useful. The high-intensity sound and shock waves originating in the plume are imaged by passing in front of the sun, particularly near the edge of the sun. This can be considered a background-oriented schlieren system. The sound from a supersonic rocket plume is thought to be due to Mach wave radiation, but the details are not yet well understood. We are analyzing these images to determine the position and radiation characteristics of the sound source in the plume. The results of this analysis will be presented.

Model calculations and measurements of shooting sound in practical situations

Shooting sound in practical situations with propagation distances up to 300 m is investigated by means of model calculations and measurements. The results illustrate uncertainties in the model calculations for practical situations. The measurements were performed with various small-caliber weapons. Microphones were placed at positions screened by a noise barrier, and also at unscreened positions. The measured signals contain muzzle sound and bullet sound. The model calculations for muzzle sound and bullet sound take into account emission spectra and various propagation attenuation terms, including ground attenuation and barrier attenuation. The bullet sound model is based on a nonlinear theory of N waves generated by supersonic projectiles. For the unscreened situation, model and measurement results show that the sound levels are considerably reduced by ground attenuation. Ground-level variations and ground roughness in the measurement area play an important role. At a 300 m distance, the A-weighted bullet sound level is higher than the A-weighted muzzle sound level, which underlines the importance of bullet sound. For the screened situation, model and measurement results are used to analyze diffraction of bullet sound by the horizontal and vertical edges of the barrier. The diffraction is explained by considering Fresnel zones on the bullet trajectory.

Primena tehnika vizuelizacije strujanja za određivanje sile otpora projektila

The paper provides an overview of flow visualization methods. From the many ways of classifying flow visualization methods, the chosen method of classification is in accordance with the experimental procedure. Flow visualization methods that involve the addition of foreign material are the simplest, from the point of view of the required material and the experimental setup, in which one tracer and an adequate light source are most often applied, except for layers sensitive to pressure and shear stress. Their application is wide and most methods from this category can be modified very easily depending on the case. Visualization methods that involve addition of energy to the fluid flow use strong sources of electromagnetic radiation, most often lasers, to excite the molecules in the fluid stream, producing an adequate quantum-mechanical effect that enables visualization. Optical methods of flow visualization are based on changes in the refractive index of light caused by the presence of a fluid in motion in the test section, in addition, the principle of superposition of light waves is used in interferometry methods. Optical methods are mainly used in areas of supersonic flow and shock wave studies, but they are also present in exhaust gas propagation studies. As computational fluid dynamics is a separate subject, the physical laws on which CFD is based on are presented, as well as an example of flow visualization, which is an integral part of most calculations performed using this method. In addition to the classification and description of flow visualization methods, the paper provides an explanation of a approximate calculation procedure based on the use of one of the optical methods, Schlieren photography, in order to calculate the resistance force during supersonic projectile flow, as well as a comparison of results based on empirical data.

Numerička analiza udarnog voza u konusnim mlaznicama sa ravnim grlom

The overexpanded flow regime in supersonic rocket engine nozzles presents different shock wave structures due to the geometrical configurations of the internal walls. In the present investigation, the study of the shock train phenomenon is addressed for a group of convergentdivergent conical nozzles with straight-cut throats for the overexpanded flow condition for NPR=12. The viscous and compressible flow field under stationary conditions is simulated with the RANS model in the ANSYSFluent R16.2 code, which applies the finite volume method (FVM) to discretize the computational domain. The Spalart-Allmaras turbulence model is used, and Sutherland's law is used for the viscosity as a function of temperature. The results show that, in the straight-cut throat section, as its length increases, the flow accelerates and decelerates with the presence of oblique shocks, which forms a definite shock train structure, where the flow velocity fluctuations are within the estimated Mach number range of 0.6 to 1.8. Increasing the throat length significantly affects the flow development at the nozzle outlet, which decreases the thrust force.

Computational Studies of the Aerophysical Characteristics on the Head Part of the Supersonic Body of Rotation During Flight Along Trajectories

The use of modern computer systems for calculating the aerophysical characteristics of supersonic bodies of revolution together with the calculation of the flight trajectory under conditions of continuously changing Mach and Reynolds numbers of the oncoming flow, the presence of transient regimes and non-isothermality in near-wall flows is often not possible due to the complexity of the organisation of the computational process. By using a number of integral methods for calculating inviscid flows and viscous compressible near-wall flows, taking into account the non isothermality and intermittency of the boundary layer, a method has been developed for calculating the friction and heating of supersonic bodies of revolution on the flight trajectory. On the basis of well-known flight experiments, the correlation dependences of the Reynolds numbers of the beginning of the transition on sharp cones were obtained and the method of corrections for spherical blunting of the head part was implemented. By calculating the intermittency function, the changeability of flow regimes in the boundary layer is established for a number of trajectories of the supersonic uncontrolled rocket projectile. Calculated dependences for aerodynamic friction, heat fluxes and projectile wall temperature on the flight time are obtained. The concept of combined calculation of aerophysical characteristics on the flight trajectory using numerical and integral methods is proposed.

A numerical study of flow over supersonic projectile under heavy rain

This paper presents a computational fluid dynamics study of morphology and structure dynamics of the flow over a supersonic secant-ogive cylinder boat tail projectile under heavy rain. The discrete phase model is employed to approximate the process of droplet–particle collision with the projectile wall and the formation of a liquid film. The simulation results indicate that at certain angles of attack, rain impact decreases lift coefficient of projectile by as much as 14.9%, as the wall pressure distribution is distinctly reformed. Moreover, the rain condition induces the formation of a liquid film on the front end of the projectile, as the angle of attack increases, the stability of this liquid film gradually improves, while its thickness and coverage rise to the peak values and then decrease. On the projectile’s trailing half, however, the liquid film developed a watery pattern. The collision of liquid droplets causes momentum loss to the projectile, while an unstable liquid film tends to exacerbate aerodynamic performance loss, a stable liquid film would mitigate the performance loss.

Optimizing Supersonic Rocket Efficiency: a Numerical Analysis of Aerodynamic Characteristics and Angle of Canard Deflection

Optimizing Supersonic Rocket Efficiency: a Numerical Analysis of Aerodynamic Characteristics and Angle of Canard Deflection

A self-adaptive local diversity-preserving NSGA-II for the multidisciplinary design optimization of a miniaturized supersonic rocket

The miniaturized supersonic rocket or missile is an innovative concept most notably characterized by its small caliber, short length, and high flight speed. Tightly coupled design parameters and constrained objectives bring high complexity to launch safety assessments. The commonly used heuristic algorithm NSGA-II cannot address this complexity with its original density estimation strategy. In this paper, a multidisciplinary design optimization (MDO) based on a multidisciplinary feasible (MDF) architecture is established and simplified according to specific design requirements. The design system includes one coupled numerical model, two drivers, and six disciplines. As an optimizer for an MDO problem, multi-objective evolutionary algorithms (MOEAs) with heuristic features are very conducive to exploring the performance of complex rocket systems. The coupling relationship between the design variables of a small dual-chamber rocket is complex, and its optimal design is challenging to obtain empirically by traditional methods. Optimizing its propulsion performance and launch safety is imperative. For engineering designs, the convergence process of algorithms is often passive with a high degree of randomness, and the diversity of the final results is difficult to guarantee. This paper improves the Pareto front's diversity in designing a miniaturized supersonic rocket by using a self-adaptive local diversity-preserving NSGA-II (SLDNSGA-II) in an MDO framework with an active control strategy.

Equivalent Area Targets for Inverse Design Optimization with Changing Low-Boom Cruise Conditions

This paper provides theoretical and numerical justifications for inverse design optimization of reversed equivalent area of low-boom supersonic aircraft when the cruise condition changes during optimization iterations. A modified linear theory for steady flow around a supersonic projectile is used to establish the accuracy of body-of-revolution approximation of a low-boom supersonic aircraft for undertrack sonic-boom analysis using computational fluid dynamics off-body pressure. As a result, designing a low-boom shape of the off-body pressure at three body lengths below the aircraft is equivalent to designing a low-boom shape. A Bezier curve with eight control points is used to define an target for inverse design optimization of of a supersonic aircraft. To make an target matchable by a low-boom supersonic aircraft, the target must have the minimal perceived level of decibels (PLdB) for sonic boom and satisfy two constraints defined by the cruise condition, effective length, and two nondimensional parameters. Numerical results are used to verify that, for different cruise conditions, all optimized targets with PLdB below 70 can be approximately generated by scaling one of them if the targets have the same nondimensional parameters and approximately the same effective length.

Numerical Simulation of Surface Pressure of a Wedge at Supersonic Mach Numbers and Application of Design of Experiments

This paper aims to numerically simulate the flow field for wedge, cone, and ogives. Usually, wedge shapes are used as a stabilizing surface for supersonic projectiles like rockets, missiles, and planes in defense applications. Wedge-shaped or delta wings are often the principal wing used for the stability of supersonic aircraft/missiles. The main goal of the current study is to estimate the pressure at the wedge-shaped plane's/missiles nose at different Mach numbers and incidence angles. Analytical pressure distribution is determined using the strip and piston theory. Later the outcomes from the numerical simulations are compared with the results obtained analytically. The analytical and CFD findings matching is very good. The findings demonstrate that the Mach number and wedge angle are the variables that influence the deviation of static pressure. The static pressure on the surface of the wedge grows with the rise in the semi-vertex angle of the wedge angle and the Mach number. This increase in the surface pressure ratio is linear for the increase in Mach number as well as the semi-vertex angle of the wedge. However, the magnitude of increase with the Mach numbers is not the same as what it was for low Mach numbers. The enhancement in the pressure decreases with the Mach numbers.

Design and optimization of a novel supersonic rocket with small caliber

<p style='text-indent:20px;'>It's difficult to meet the design requirements of a rocket with sensitive parameters using the traditional methods. This paper develops a design and optimization concept for a lightweight solid-propellant rocket with a small caliber and a high Mach number. The structural design and numerical modeling depend on the interior ballistic methodology. The model is validated by comparing pressure-time data from simulation and experiment. A modified evolutionary algorithm with constraints is applied because of the interactive design parameters and conflicting objects. The launch performance is improved by single- and multi-objective optimization. Under unchanged interior ballistic performance conditions, the peak pressure is reduced by 46.4%, and the erosive peak ratio is reduced by 46.4%. Despite the constraints, the Mach number is improved by 4.9%, the total impulse is improved by 6.3%, the peak pressure is reduced by 92.5%, and the erosive effects are reduced by 38.1% using different optimal solutions. A Pareto front is obtained by a constrained NSGA-Ⅱ, which reveals non-linear and non-uniform relations among design objects. A tidying method is proposed for a clear Pareto front. It indicates that, despite the sensitive parameters, launch safety and higher velocity are possible. The results help designers choose the best design schemes.</p>

Numerical Analysis of Cavity-Based Control of Base Pressure Variations at Supersonic Mach Numbers

In the present study, the base pressure variations induced by the presence of a cavity, known to have a strong influence of the behaviour of supersonic projectiles, are investigated through numerical solution of the balance equations for mass, momentum, and energy. An area ratio of four is considered and numerical simulations are carried out at Mach M = 1.2, 1.4, 1.6, and 1.8 assuming no cavity or cavity locations 0.5D, 1D, 1.5D, and 2D. The inlet pressure of the nozzle is considered as a flow variable. The Taguchi method is also used, and the considered cases are then analyzed using a full factorial experimental design. The results show that the cavity is effective in increasing the base pressure for the conditions examined. For other nozzle pressure ratios, cavities do not lead to passive control due the change in the reattachment length. The distribution of wall pressure reveals that, in general, a cavity used to implement passive control of the base pressure does not adversely influence the flow pattern in the domain.

Towards three-dimensional characterization of hypervelocity impact events using ultrahigh-speed digital holography

This experimental study reports the development and use of high-speed and ultrahigh-speed digital holography (DH) systems to perform three-dimensional (3D) characterization of particle-fields created from the impact of a supersonic projectile with a target plate. Different target materials including clay and gypsum were tested producing a cloud of ejecta particles from the impact zone. While the megahertz-rate ultrahigh-speed DH instrument version was used for measurements in early (0-250 µs) time-scale processes, the 100 kilohertz-rate high-speed version was employed to interrogate extended (250 µs-1 s) durations following impact. By capturing holograms and performing wavefront reconstruction at different depths, holography allows scanning through the 3D space plane-by-plane at given moment in time, allowing the user to focus on different objects to determine their shape and precise 3D location. We automate this particle detection procedure in sequential holograms by using a minimum intensity focusing criterion and obtain their locations in three-dimensional space with respect to time. Further, we track particles over these durations to determine their trajectories along with instantaneous and mean velocities. Based on the optical configuration and field-of-view employed both instruments were able characterize the ejecta clouds for particle size distributions ranging 1 µm-1 mm. The results presented clearly demonstrate the applicability of digital holography for 3D characterization of ejecta and debris clouds arising from the impact of supersonic and hypersonic projectile with different material targets.

Kometa i rakieta: postęp technologiczny w intertekstualnych konstelacjach "Komety" Brunona Schulza i "Tęczy Grawitacji" Thomasa Pynchona

Twentieth-century literary representations of objects that fall from the sky include technological, man-made items as well as natural phenomena. Writers have contributed their specific readings to instances of this kind, and have grafted specific symbolic meanings on these phenomena. The falling object in question can be a supersonic rocket like the one that constitutes the thematic center of the American novelist Thomas Pynchon’s 1973 Gravity’s Rainbow. It may likewise be a celestial body, a larger and usually more destructive one than a mere meteor — a bolide, in other words, like the one Bruno Schulz describes in his 1938 story “Kometa”. What the rocket and the comet have in common is that Pynchon and Schulz ascribe a special significance to their respective flight curves and, more specifically, to the turning point of this parabola. Pynchon associates the issue of immobility at the rocket’s turning point with that of transformation; an instance mirrored in the text by Schulz, who moreover does so – again like Pynchon later – with reference to cyclists transmogrified into frozen firmament riders. The paper identifies a common intertextual reference point for this in the poetry of Rainer Maria Rilke. It demonstrates the impact as well as the similarities, but also interpretational differences of the Rilkean constellation of new stars named “Rider” in Schulz’s and Pynchon’s fiction.

Gas Flow and Ablation of 122 mm Supersonic Rocket Nozzle Investigated by Conjugate Heat Transfer Analysis

The propellant gas flow of a supersonic rocket in inappropriate operating conditions can cause excessive ablation inside a nozzle. In this research, conjugate heat transfer analysis (CHTA), consisting of computational fluid dynamics (CFD) and finite element analysis (FEA), was applied to investigate the gas flow and ablation of a 122 mm nozzle as a case study in the transient state, based on actual operating conditions. First, the nozzle was tested in a static experiment. Then, the experimental results were employed for CHTA settings and validation. Next, after completing the CFD calculation, the results revealed that the nozzle’s gas flow, temperature, pressure, Mach number, shock, etc. were consistent with theoretical results. Finally, using the CFD results as loads, the FEA results showed the equivalent von Mises stress (σv), which was consistent with the ablation results from the experiment, as expected. The more the σv, the greater the ablation. Both σv and ablation were high near the throat and decreased further away. In addition, increasing the insulators’ thickness reduced σv, leading to ablation reduction. The research findings contribute to an understanding of ablation and the methodology of employing CHTA to improve the design of 122 mm and other nozzles with reduced ablation for higher efficacy.