Spinning Projectile Research Articles

In-Flight Self-Alignment Method Aided by Geomagnetism for Moving Basement of Guided Munitions

Due to power-after-launch mode of guided munitions of high rolling speed, initial attitude of munitions cannot be determined accurately, and this makes it difficult for navigation and control system to work effectively and validly. An in-flight self-alignment method aided by geomagnetism that includes a fast in-flight coarse alignment method and an in-flight alignment model based on Kalman theory is proposed in this paper. Firstly a fast in-flight coarse alignment method is developed by using gyros, magnetic sensors, and trajectory angles. Then, an in-flight alignment model is derived by investigation of the measurement errors and attitude errors, which regards attitude errors as state variables and geomagnetic components in navigation frame as observed variables. Finally, fight data of a spinning projectile is used to verify the performance of the in-flight self-alignment method. The satisfying results show that (1) the precision of coarse alignment can attain below 5°; (2) the attitude errors by in-flight alignment model converge to 24′ at early of the latter half of the flight; (3) the in-flight alignment model based on Kalman theory has better adaptability, and show satisfying performance.

Correcting Algorithms of the Spinning Projectile Attitude Based on the Background Magnetic Field Compensation

At present, traditional navigation method could not provide long-time stability attitude information for the high spinning projectile because of drift errors of micro-inertial sensors. Meanwhile, the projectile attitude measuring method with respect to the earth's magnetic field is still auxiliary. The principle of characteristic ratio algorithm and compensation model of the background magnetic field for the spinning projectile are been introduced. To realize the high accuracy attitude measuring of the projectile, a new correcting method is proposed. The detail correcting steps are derived with the linear interpolation theory and iterative algorithm. On this basis, numerical simulation is conducted combining with projectile's flight rules. The results show that the corrected attitude angles errors are within, and attitude update rate increased obviously. The calculating results could better describe the whole real roll motion. The proposed correcting method is significantly effective.

On the Stability of a Spinning Projectile

Stability problem both for small and large yawing of a spinning projectile has been discussed. In the latter case criterion for stability of steady conically yawing motion has been obtained. Particularly it has been proved that with a tilting moment coefficient of the type micro(delta)-betaohm/sup2/4[1-4qs(1-cosdelta)] the motion of a shell in steady state is stable like an equivalent top only when q>=0.

Analysis of Theory and Model of Background Magnetic Field of High-Spinning Projectile

At present, methods of the navigation and the attitude measurements of projectile utilizing the magnetic fields are facing the interference from the BMF (background magnetic field). The principle and mathematical model of the BMF for the spinning projectile are been researched to realize the high accuracy measurement of the geomagnetic field on projectile. The composition and jamming mechanism of the projectile's BMF are derived with the Faraday electromagnetic induction theory. High precision compensation model of the geomagnetic measurement is established by synthesizing the magnetic sensor error model. Based on the idea of the error transfer, the attitude measuring errors caused by the BMF are analyzed and the error calculation formulas are given. On this basis, numerical simulation is conducted combining with projectile's flight rules. The results show that the influence of attitude angle measuring precisions caused by the background interference magnetic field are much bigger than the errors caused by the sensor noise and the established compensation model has obvious effect. Besides, the effective BMF compensation of geomagnetic measurements on the projectile must be conducted if the attitude angle measurement error is in requirements within ±1 °.

Actuator characterization of a man-portable precision maneuver concept

The US Army Research Laboratory is conducting research to explore technologies that may be suitable for maneuvering man-portable munitions. Current research is focused on the use of rotary actuators with spin-stabilized munitions. A rotary actuator holds the potential of providing a low-power solution for guidance of a spinning projectile. This is in contrast to a linear (reciprocating) actuator which would need to constantly change direction, resulting in large accelerations which in turn would require large forces, thereby driving up the actuator power. A rotational actuator would be operating at a fairly constant rotation rate once it is up to speed, resulting in much lower power requirements. Actuator experiments conducted over a variety of conditions validate the dynamic models of the actuator and supply the data necessary for model parameter estimation. Actuator performance metrics of spin rate response, friction, and power requirements were derived from the data. This study indicates that this class of maneuver concepts can be driven with these actuators. These results enable actuator design and multi-disciplinary simulation of refined maneuver concepts for a specific application.

Three different attitude measurements of spinning projectile based on magnetic sensors

Micro-inertial sensors currently could not provide long-time stability attitude information for the high spinning projectile because of drift errors. Meanwhile, the method of the navigation and attitude measurement with respect to the earth’s magnetic field is still auxiliary, and the attitude angle information cannot be got only by measuring the three-axis components of the geomagnetic field. In view of the flying characteristics of high spinning projectile, three different attitude measurements only using magnetic sensors are researched. Through comparative analyses, the calculating principle, system composition, applicable condition and error range of these methods are explained. Meanwhile, the semi-physical experiments are made to prove the effectiveness of the three attitude measurements. The experiment results indicate that only scalar arithmetic operations are required for these angular measurements and they have the day/night and all weather capability. The three different measurements have same angle error range within ±1° but different attitude updating rate.

Application of surface conformed linear mesh and data subdivision technique to a spinning projectile

In this paper, we report a spinning projectile application of a parallel CFD program featuring surface-conformed isotropic mesh subdivision. The subdivision technique generates finer computational mesh without user interaction using a 3-D hybrid unstructured coarse base. The main motivation behind the subdivision technique is to overcome the bottleneck in generating and processing of the computational meshes with billions of elements. First, we generate a coarse mesh using any unstructured mesh generator. Then, we subdivide the coarse mesh to the level of resolution needed for the simulations. Finally, we conform mesh nodes on solid surfaces to the original geometry since linear subdivision ignores surface curvatures. We use K-D tree search algorithm in the surface mapping. To deform interior mesh nodes due to the surface correction, we use the spring analogy method since deformations are very small. Surface correction is implemented in parallel using the Message Passing Interface. The new mesh obtained from the isotropic subdivision preserves mesh density distribution of the original coarse mesh. The mesh subdivision with surface correction is integral part of our Variable Intensity Computational Environment. A projectile test case with and without spinning at different angles of attack are used to demonstrate the applicability of this method. Flow solutions are obtained using our compressible Navier–Stokes flow solver, CaMEL Aero, with the Detached Eddy Simulation turbulence model. Flow solutions and mesh subdivisions are performed in our parallel cluster at the Jackson State University.

Longitudinal Aerodynamics of a Canard Guided Spin Stabilized Projectile

Navier–Stokes simulation is performed on a canard guided spinning projectile for different attack angles and circumferential position angles of canard over the Mach number range of 1.8–2.2. The computational Magnus moment coefficients of test case are validated with available experimental data of a Secant-Ogive-Cylinder-Boattail (SOCBT) configuration at Mach 3, demonstrating that the method can provide an accurate and viable approach for this problem. The aim of the present study is to provide a detailed understanding of the effects of canard with different circumferential position angles on longitudinal aerodynamic coefficients at three supersonic speeds and various angles of attack. And the results show that normal force coefficients and pitch moment coefficients vary periodically with the circumferential position angles of canard.

Lateral-Directional Aerodynamics of a Canard Guided Spin Stabilized Projectile at Supersonic Velocity

A computational study performed for a canard guided spin stabilized projectile using finite volume TVD schemes is described in this paper. Computational Fluid Dynamics (CFD) modeling and analysis of the spinning projectile with fixed canard are conducted to determine the lateral-directional aerodynamic coefficients at three supersonic speeds and various angles of attack. The analyses provide a detailed understanding of the effects of canard with different circumferential position on lateral-directional aerodynamic coefficients, and the results show that side force coefficient and yaw moment coefficient vary periodically with the circumferential position angles of canard.

회전발사체 롤댐핑 특성에 관한 고속 유동장 실험연구

본 연구의 목적은 풍동실험을 통해 회전발사체에서 발생하는 동적 롤댐핑 특성을 실험적으로 측정하는데 있었으며, 이를 위해 약 12,000 rpm으로 회전하는 회전발사체 실험모형에 작용하는 롤댐핑 특성의 측정을 위한 고속풍동실험을 국방과학연구소 삼중음속풍동에서 수행하였다. 실험시의 마하수는 0.7~1.05까지의 천음속 영역이었으며 이때의 받음각 구간은 -4~+10 deg이었다. 풍동실험 측정기법의 유효성 평가를 위해 동일형상 모형에 대해 기 수행하였던 롤댐핑 측정결과와의 비교검토를 수행하였다. The purpose of this research is to determine the dynamic roll-damping data of a spinning projectile in wind-tunnel testing. In the present work, the high-speed wind-tunnel tests for the roll-damping measurements were conducted on a spin-stabilized projectile model in the Agency for Defense Development's Tri-Sonic Wind Tunnel at spin rates about 12,000 rpm. The test Mach numbers ranged from 0.7 to 1.05, and the angles of attack ranged from -4 to +10 deg. The validity of the wind-tunnel measurement techniques was evaluated by comparing them with the previous test results on the same configuration.

Effective Use of Magnetometer Feedback for Smart Projectile Applications

: The use of magnetometers for orientation estimation on rapidly-spinning flight bodies is analyzed. Specifically, the effect of spin-induced magnetic field distortion is discussed, with particular attention to its implications for magnetometer-based orientation estimation. First, the nature of spin-induced field distortion is described and it is shown that, if not properly accounted for, distortion can lead to significant estimation errors in artillery projectiles. Then, an orientation estimator is constructed driven by magnetometer, gyroscope, and GPS feedback. A novel feature of this algorithm is its compensation for spin-induced distortion of the Earth's field. The algorithm also incorporates in-flight magnetometer calibration performed simultaneously with projectile orientation estimation. The comprehensive algorithm is built as a coupled set of Extended Kalman filters. Observability of the estimation problem is discussed and unobservable modes are identified. Finally, example results and Monte Carlo simulations compare estimation performance to algorithms which neglect spin-induced distortion effects or do not perform in-flight calibration. These results demonstrate that magnetometer-based systems on-board spinning projectiles should incorporate corrections for field distortion, and that overall accuracy is greatly enhanced by performing in-flight calibration.

Systems of aiming guided spinning projectile

In the article suggestions are resulted in relation to the improvement of the system of aiming spinning projectile. Possibility of application of immobile radio engineering co-ordinator of purpose is considered with the special signals. It is also suggested to use an aiming head with the complexing of infra-red and radio engineerings signals.

회전발사체 마그너스 특성에 관한 고속 유동장 실험연구

The purpose of this research is to determine the dynamic Magnus effect data of a spinning projectile in wind-tunnel testing. In the present work, the high-speed wind-tunnel tests for the Magnus effect measurements were conducted on a 155-mm spin-stabilized projectile model in the Agency for Defense Development`s Tri-Sonic Wind Tunnel at spin rates about 12,000 rpm. The test Mach numbers ranged from 0.7 to 2.0, and the angles of attack ranged from -4 to +10 deg. The validity of the wind-tunnel measurement techniques was evaluated by comparing them with the previous test results on the same configuration. The experimental results show that fair to good agreement is obtained with resonable accuracy.

Magnus and Spin-Damping Measurements of a Spinning Projectile Using Design of Experiments

Covers advancements in spacecraft and tactical and strategic missile systems, including subsystem design and application, mission design and analysis, materials and structures, developments in space sciences, space processing and manufacturing, space operations, and applications of space technologies to other fields.

Dispersion Analysis for Spinning Artillery Projectile

This paper investigates the dispersion for unguided spinning projectile in order to explain the importance of the projectile production accuracy and the benefit of using guided projectiles. The total dispersion results mainly from the production inaccuracy of: (1) gun tube which can be shown in projectile's launching problems (muzzle angle, and muzzle pitching and yawing rates), (2) propellant which can be shown in projectile's muzzle velocity and muzzle spinning rate and projectile which is the projectile total mass, axial and lateral moments of inertia, and resultant center of gravity. The other causes are occurred due to free flight portion of projectile’s trajectory which may be divided to: launching problems (vibration of launch tube), wind velocity and direction (wind profile). In this study, a trajectory calculation using a 6-DOF model was developed and applied for 155 mm M107 projectiles at different projectile and flight properties.

Detached Eddy Simulations and Reynolds-Averaged Navier- Stokes Calculations of a Spinning Projectile

Covers advancements in spacecraft and tactical and strategic missile systems, including subsystem design and application, mission design and analysis, materials and structures, developments in space sciences, space processing and manufacturing, space operations, and applications of space technologies to other fields.

회전 발사체용 마그너스 효과 특정기법의 개발

The Magnus effect measurement apparatus was designed and built for spinning wind tunnel model which would simulate the rotation of projectiles. Prior to the high speed test, the ground functional test and the low speed test were carried out in the Agency for Defense Development`s Low Speed Wind Tunnel(ADD-LSWT) at spin rates from about 6,000 to 10,000 rpm. Magnus force and moment were measured on the spinning projectile model at velocity of 100 m/s. It was shown that the Magnus force and moment were linear function of spin parameter. The test results were compared with Magnus test run on the same configuration in the Arnold Engineering Development Center`s Propulsion Tunnel 4T(AEDC-4T).

Perturbation of Initial Stability of an FSAPDS Projectile

For a spinning projectile, the initial stability condition is 2 = 1+ (4 K3 / K22) > 0. In the presentstudy, this condition has been modified for the malalignments arising due to pressure gradientand damping moment for an FSAPDS projectile. The equations of motion are established for thefirst phase of motion. A mathematical model for the first phase of motion has been developed.The effect of perturbation on the trajectory and stability of motion are discussed. It is provedthat if 3 K(a parameter appearing due to perturbation)(-K22 2 /4 ), the initial stability ofmotion will breakdown.

Navier-Stokes Computations for a Spinning Projectile from Subsonic to Supersonic Speeds

A computational study has been undertaken to predict the static-aerodynamic, Magnus-moment, and roll-damping coefficients of a standard spinning projectile using a single, modern, unstructured Navier-Stokes flow solver. Numerical results without engraving and semi-empirical results have been obtained for a wide range of Mach numbers to include subsonic, transonic, and supersonic flight regimes. Effects of 0-, 2-, and 5-deg angles of attack have been investigated. Flowfield characteristics of each flight regime are briefly explored. A comparison of coefficients calculated from the computational fluid dynamics results are made to both experimental range data as well as semi-empirical aeroprediction code results with some success. Good predictive capabilities are found for the static aerodynamic coefficients throughout all of the flight regimes. Discrepancies arise between the computational results and the experimental results for the Magnus moment and roll-damping coefficients due in part to the lack of engraving on the computational model.

Prediction of swerving motion of a dual-spin projectile with lateral pulse jets in atmospheric flight

Using the linear theory for a dual-spin projectile in atmospheric flight, closed form expressions are obtained for swerving motion under the action of lateral pulse jets. Trajectory results generated by the linear theory equations and a fully nonlinear seven degree-of-freedom dual spin projectile model agree favorably. The analytic solution provides a relatively straightforward and computationally efficient means of trajectory estimation which is useful within smart weapon flight control systems. In order to accurately predict the impact point using the analytic solution, the dual-spin projectile linear model must be updated periodically. Terminal impact point prediction degrades rapidly as the linear model update interval is increased beyond a critical value. Control authority, as defined by the change in impact location due to a pulse jet firing, steadily decreases as a function of projectile down range position.