Launch Tube Research Articles

Dimensional chains for ensuring that the assembled axisymmetric housing is inserted into the guide hole

Dimension chains were calculated using the example of a jet engine housing entering the launch tube. It was found that the method used does not take into account the actual values of losses and requires signifi cant reliability in the radical runout of the collected rocket engine case. A method for controlling radial runout in prisms is also considered.

Flow interactions on supersonic projectiles in transitional ballistic regimes

A projectile moving in the transitional/intermediate ballistic regime encounters many complex flow phenomena as the flow field contains two blast waves and several flow interfaces. The aerodynamic characteristics of the projectile are highly influenced by the interaction of the projectile with the surrounding flow field. The present study aims to experimentally visualize the flow structures associated with a moving projectile in the immediate vicinity of the launch tube (transitional/intermediate ballistic regime). In this work, the main focus is to investigate three significant phenomena which normally occur in the transitional ballistic regime and have significant effects on the aerodynamic characteristics of the projectile. These are the moving projectile-standing shock interaction termed as unsteady shock diffraction, shock generation due to the transition in the relative projectile Mach number and the moving projectile-moving shock interaction known as the projectile overtaking phenomenon. Experiments are carried out with projectiles of various configurations for various projectile Mach numbers. The flow field is visualized using time-resolved schlieren and shadowgraph flow visualization techniques. The experiments could capture several interesting features of projectile-flow interactions such as the unsteady shock diffraction, shock generation and overtaking phenomenon in various flow regimes through visualization and quantification of the images using image processing techniques.

Exhausted jet caused the deformation of front metal seal covers in a multiple launch rocket system

During the launch tests of a Multiple Launch Rocket System (MLRS), the front metal seal covers on unlaunched tubes had plastic deformation and felled to the ground. More seriously, the rocket exhausted jet directly caused damage to some of the unlaunched rockets projectiles. As the rocket exhausted jet impinged on the cover, high temperature and high pressure jet caused plastic deformation of the covers. So the temperature and pressure of exhausted jet acting on the surface of the cover were measured. Then pressure data were used to estimate the strain of front cover on adjacent launch tube caused only by pressure. And temperature data were used for thermal stress analysis of the cover. Furthermore, the triaxial strain curves of the cover were obtained during a flight test in which a 252-mm diameter rocket projectile was launched from the MLRS. The results demonstrated that plastic deformation of the covers is mainly due to the thermal deformation caused by the high temperature, which provided guidance for optimal design of front seal covers. No plastic deformation was found in the modified covers during subsequent launch tests of the MLRS.

Design and Control of an Underwater Launch System

The ability to launch, or otherwise deploy, a cylindrical body such as an unmanned vehicle, from an outer tube in an underwater environment continues to be of interest to the marine community. Applications of such technologies include the use of small unmanned underwater vehicles (UUV’s) deployed from deep ocean craft to support oil exploration efforts or inspection of damaged infrastructure. Historically, these payloads are deployed from their containment tube through the use of a water slug generated from a pump which pushes the vehicle into the open ocean environment.The objectives of this project are to identify and demonstrate a method to launch a cylindrical body from the launch tube utilizing an electromagnetic scheme. It was found that the solenoid coil launching mechanism was the most effective for an underwater launcher. A design was created, modeled in simulations, and finally built and tested to prove its validity. It was found that the solenoid coil launcher could effectively expel a payload with ample exit velocity, low noise, and could be reloaded several times within a minute.

Intermittent Gliding Flight Control Design and Verification of a Morphing Unmanned Aerial Vehicle

The intermittent gliding flight method takes advantage of the updraft is adopted to increase the flight endurance time of a type of multifunctional morphing unmanned aerial vehicle (UAV). This type of UAV is able to be folded before launch, launch from a cylindrical launch tube, and adjust the wing span and sweep angle during flight. It has the advantages of convenient storage and transportation and can use the energy of the updraft. In order to effectively utilize the updraft, the mathematical model of updraft is established, and an updraft judging method is proposed. In order to complete the intermittent gliding flight, the flight progress is divided into two stages and a segmentation control law is proposed. During the intermittent gliding stage switching, the wing sweep angle and wing span length are varied to accommodate requirements of different stages. H ∞ robust control design method for gain scheduling based on linear parameter varying model is used to ensure the stability of the morphing UAV during the wings change. The mathematical simulation verifies the effectiveness of the morphing control algorithm. After that, a semi-physical simulation verification involving a mathematical UAV model with a physical wing changing mechanism, a physical embedded flight control module, the real flight attitude, and the virtual route are implemented. It has been verified that the morphing UAV can remain stable throughout the entire cycle of the intermittent gliding. Moreover, the intermittent gliding flight with updraft can reduce the fuel consumption of the morphing UAV and increase its flight endurance time.

DEVELOPMENT OF ANTIHAIL ROCKET WITH REACTION LIFTOFF

Hail-suppression activities are undertaken in many countries to prevent the devastating effects of hailstorms. Among various hail-suppression techniques there is overseeding, where the hail formation process is influenced by seeding the clouds with artificial nuclei. An injection of artificial nuclei into supercooled parts of the clouds can be performed by small low-altitude rockets which carry a pyrotechnic substance impregnated with meteorological reagent. The reagent produces nuclei during burning of pyrotechnic substance and injects these nuclei directly into the cloud region where the hail develops and thus prevents hail formation. This paper reports on the development of a new generation of antihail rockets, where a rocket (which consists of a motor and a container with a pyrotechnic substance) is launched from its transport tube, i.e., the transport tube represents the launcher at the same time. In addition to motor thrust, the rocket escapes the launch tube at the expense of exhaust gases produced by the motor (hot-launch system). As the rocket launch velocity increases in this way, its operation range is extended and the surface wind sensitivity of the rocket trajectory is reduced. Thereby the total mass of the propellant and the diameter of the rocket are reduced, for the same maximum altitude and mass of the reagent, as compared to the rockets propelled during launching by thrust force only. This also ensures better performance, easy handling, and reliability of use.

An Electromagnetic Rail Launcher by Quadrupole Magnetic Field for Heavy Intelligent Projectiles

This paper presents a new rail launcher based on a rupole magnetic field. This novel propulsion concept is adopted for launching heavy intelligent projectile. The interaction between the magnetic field and the armature current results in the generation of a large thrust. The thrust acts on the armature where the intelligent projectile is loaded without magnetic shielding, and pushes it forward. The configuration of the rails is given in this paper. Numerical analysis and the finite-element model are adopted to validate the properties of the magnetic field in the launch tube. The current and magnetic field distribution in the armature are simulated in ANSYS Maxwell 3-D and based on which the armature’s structure is designed. The thrusts as function of the rail distance and current are presented. The results show that the proposed rail launcher can project sensitive devices because of its magnetic field features and it can provide abundant thrust for heavy projectile, as well as good stability in launch process.

Velocity Control of Diaphragmless Vertical Gas Gun for Low Pressure Ranges

In the field of impact engineering, high-speed impact phenomena are simulated using a projectile accelerator. At the Impact Engineering Laboratory in Ritsumeikan University, a single-stage gas gun was designed to investigate the high-speed penetration phenomena of impacts in sand, which is known to show fluid-like behavior. The gas gun consists of a 2 m launch tube that can achieve projectile muzzle velocities of up to around 500 m/s. The theoretical muzzle velocity of the projectile can be calculated by considering the speed of sound and the specific heat ratio of propellant gases. A performance evaluation for high-pressure ranges of 1 MPa and higher in a high-pressure vessel has been conducted. When fitting parameters are introduced to the theoretical formula, good agreement is obtained with the experimental results. In this study, experiments for low pressure ranges were conducted to predict the projectile velocity and to investigate the minimum velocity limit of the projectile. By introducing fitting parameters to the theoretical formula, the projectile velocity could be predicted accurately for pressure ranges less than 1 MPa. Furthermore, the minimum velocity limit of this equipment was found to be around 30 m/s.

Non-Contact DC Electromagnetic Propulsion by Multipole Transversal Field: Numerical and Experimental Validation

This paper describes the numerical and experimental validation of a novel non-contact dc electromagnetic propulsion concept. In the proposed approach, a propulsion coil carrying a dc current is surrounded by a dc transversal multipole field created inside of a launch tube. The interaction between the transversal dc magnetic field and a dc propulsion coil results in the generation of axial (thrust) force with no need of sliding contacts. This paper describes a numerical assessment of the field-current-force interactions based on both analytical calculations and finite elements, and the corresponding validation experiments. The experiments demonstrate the generation of contactless axial (thrust) force in a dc launch coil using a dc transversal multipole field, and provide a benchmark for the model-based prediction of the field-current-force interactions. Partial magnetic shielding of the propulsion coil is used to selectively attenuate the magnetic field experienced by the thrust coil in a way that a net thrust force is achieved. Experimental measurements confirmed that it is indeed possible to generate contact-free thrust force on a dc propulsion coil using a dc multipole magnetic field, and the measured values of thrust force are in good agreement with the corresponding predictions.

A Desktop Tensile Kolsky Bar for the Dynamic Testing of Metallic Foils

A miniature tension Kolsky (split-Hopkinson) bar has been developed to facilitate measurement of the uniaxial stress–strain constitutive response of metallic foils at strain rates on the order of 104 s−1. The system utilizes a cylindrical launch tube with an internal striker to generate the loading pulse. This launch tube set-up allows for the use of traditional disk shaped pulse shapers which may be required to ensure that the specimen in deformed under force equilibrium and at a nearly constant strain rate. Unlike most traditional Kolsky bar systems, incident and transmitted bars with rectangular cross-section are used to facilitate specimen and strain gage mounting. The rectangular bar cross-section also provides a reduced cross sectional bar area when compared to an equivalent diameter circular section which increases the system sensitivity. The system was used to perform dynamic tests on 99.9 % magnesium specimens, illustrating the ability to measure the high-rate response of ductile metals under equilibrium and constant strain rate conditions.

気体デトネーション駆動型ガス銃を用いた飛行体加速実験

The gaseous detonation driven gas gun was developed for accelerating the projectile to a supersonic speed. The gas gun was simply consisted of two straight stainless-steel tubes. The one was the detonation tube and the other was the launch tube. The detonation tube was 50 mm inside diameter with 2180 or 4280 mm long, and the launch tube was 5 mm inside diameter with 1040 mm long. Chapman-Jouguet detonation wave was initiated in the detonation tube, and the projectile was accelerated in the launch tube via combustion products behind the detonation wave. The spherical projectile of 4.76 mm diameter was made of high-density polyethylene with 52 mg mass. The driver mixture was stoichiometric hydrogen-oxygen premixed gas with initial pressure ranging from 120 to 450 kPa. The gas gun was successfully operated, and the maximum projectile velocity of 1400 m/s was obtained for the conditions that the detonation tube was 4280 mm long and the initial pressure of the driver gas was 450 kPa. The results of the longer detonation tube demonstrated that the projectile velocity was 1.15 - 1.25 times higher than the case of shorter detonation tube. This velocity change of the projectile could be explained by the pressure increase at the inlet of the launch tube by using longer detonation tube. The reason of the pressure increase has a possibility that the length of Taylor wave behind the detonation wave becomes longer for the case of longer detonation tube.

EMI's TwinGun Concept for a New Light-gas Gun Type Hypervelocity Accelerator

A new two-stage light-gas gun type accelerator was developed at Fraunhofer EMI. The accelerator features two parallel pump tubes that are attached to a single powder chamber. Loading conditions are adjusted to achieve a small delay between the arrival of the two pistons at their respective accelerated reservoir. A merging section combines both gas channels and guides the two pressure pulses generated to a single launch tube breech. The two pressure pulses merge to a single, but elongated pressure pulse that acts on the projectile. Carefully adjusting the loading conditions shall in the future increase the performance compared to standard light-gas gun accelerators. Initial experimental results of the calibre 4 mm prototype show feasibility of the concept.

Numerical Simulation of the Added Mass and Drag of a Uniform and Accelerated Motion Projectile

The added mass, drag and drag coefficient of a uniform and accelerated motion projectile in viscous incompressible fluid were calculated by numerical simulation and dynamic mesh method. The effect of velocity and acceleration on the added mass, drag and drag coefficient of the projectile in a launch tube was investigated. The results show that the variation rules of added mass, drag and drag coefficient are basically the same when the projectile moves at different speeds. The added mass, drag and drag coefficient become smaller and drag becomes bigger with the increase of speed. The variation rules of the added mass, drag and drag coefficient are the same as uniform motion when the projectile moves at different accelerations. The added mass and drag coefficient become smaller and drag becomes bigger with the increase of acceleration. These reveal that the motion region, velocity and acceleration have some effect on the added mass, drag and drag coefficient.

Non-invasive timing of gas gun projectiles with light detection and ranging

We have developed a Light Detection and Ranging (LIDAR) diagnostic to track the position of a projectile inside of a gas gun launch tube in real-time. This capability permits the generation of precisely timed trigger pulses useful for triggering high-latency diagnostics such as a flash lamp-pumped laser. An initial feasibility test was performed using a 72 mm bore diameter single-stage gas gun routinely used for dynamic research at Los Alamos. A 655 nm pulsed diode laser operating at a pulse repetition rate of 100 kHz was used to interrogate the position of the moving projectile in real-time. The position of the projectile in the gun barrel was tracked over a distance of ~ 3 meters prior to impact. The position record showed that the projectile moved at a velocity of 489 m/s prior to impacting the target. This velocity was in good agreement with independent measurements of the projectile velocity by photon Doppler velocimetry and timing of the passage of the projectile through optical marker beams positioned at the muzzle of the gun. The time-to-amplitude conversion electronics used enable the LIDAR data to be processed in real-time to generate trigger pulses at preset separations between the projectile and target.

Application of the Projection Pursuit Regression in Forecasting the Pressure of the Torpedo Launch Tube

Through the relation among the pressure of the torpedo launch tube, cylinder volume, cylinder pressure and emission valve size, we adopt the projection pursuit regression method and establish the model to predict the pressure of the torpedo launch tube. Through the comparison of experiment data and model prediction, fitting accuracy of this relation model is higher than that of the partial least-squares regression method and linear regression model and the projection pursuit regression is an efficient method which can research the initial ballistic trajectory of ship launched torpedoes.

Development of a Linear Implosion-driven Hypervelocity Launcher

A traditional difficulty with high-explosive hypervelocity launching techniques is that extreme loading generally causes hydrodynamic deformation of the projectile either incidentally or by design. The launcher presented in this study uses explosives to operate the pump tube of a two-stage light gas gun via continuous linear implosion. In this configuration, the projectile is cushioned from direct action of the explosives by a light driver gas. The launch cycle is therefore comparable to a conventional two-stage light gas gun but with the shock driven by the rapid linear implosion of the pump tube compressing the gas to a much higher enthalpy. A laboratory scale version of the implosion driven launcher has recently demonstrated the ability to launch a 0.7g projectile to 7.9km/s. This design has successfully been scaled up to launch a 15g projectile to 7.6km/s, a result comparable to large two-stage light gas guns. This study presents the experimental and computational work performed in the ongoing development of this device. The extreme launch conditions lead to a number of unique design considerations, including dynamic confinment of the driver and launcher reservoir, mitigation of the loss of driver gas, and in-bore projectile stability and survivability. These issues are addressed experimentally through a number of focused launcher trials, as well as through the development of a quasi-one-dimensional Lagrangian hydrocode. The development of advanced implementations that involve continuing explosives onto the reservoir and launch tube in order to maintain a high driving pressure are also considered. These “second stage” techniques offer the potential for achieving projectile velocities in excess of 10km/s.

G191016 一段式ガス銃の回転発射機構の検討及び基礎実験([G191]宇宙工学部門,一般セッション)

The high-speed collision experiment is conducted,by the issue of space debris collision.However,the experiment in consideration of the influence of the rotation projectile is not carried out very much.The purpose of this study is to develop the single-stage gas gun which can fire a rotation projectile at low velocity.Improve a launching device and measure a turn and the velocity of the projectile with a high-speed video camera.The number of revolutions of the motor which turned a projectile used 14000rpm.The experimental conditions were being press gas,the length of the launch tube and pressure of vacuum chamber,raised the pressure of the pressure vessel,and it was found to be effective for projectilerotary maintenance to make an acceleration pipe a vacuum.The maximum number of turns of a projectile comprising this rotary launching device is 10000rpm.

Numerical simulation of flow fields induced by a supersonic projectile moving in tubes

Numerical study of the shocked flows generated by a supersonic projectile released from a launch tube into a big chamber has been performed in this paper. Based on fixed Cartesian grids, the two-dimensional axisymmetric Euler equations are solved by the fifth-order WENO scheme implemented with moving boundary conditions. Both the level set technique and ghost fluid method are used for capturing the moving interface of the projectile implicitly. The numerical results show that complex shock phenomena exist in the transient shock flow, resulting from shock-wave reflection, shock-wave focusing, shock-wave/projectile interaction and shock-wave/contact surface interactions. The relationships between the acceleration of the projectile and the transient shock flow are also discussed in detail.

발사체 충격 방식을 사용한 초음속 액체 제트의 과도 분무 형상에 관한 연구

The effects of projectile impact system on the transient spray characteristic which is supersonic liquid tip velocity were studied by experimentally. Supersonic liquid jets were generated by impact of a high speed projectile driven by a Two-stage light gas gun. A high speed camera and schlieren optical system were used to capture the spray structures of the supersonic liquid jets. In a case of nozzle assembly Type-A, expansion gases accelerate a projectile which has a mass of 6 grams from 250 m/s at the exit of the launch tube. Accelerated projectile collides with the liquid storage part, then supersonic liquid jets are injected with instantaneous spray tip velocity from 617.78 m/s to 982.54 m/s with various nozzle L/d. However, In a case of nozzle assembly Type-B which has a heavier projectile (60 grams) and lower impact velocity (182 m/s), an impact pressure was decreased. Thus the liquid jet injected at 210 m/s of the maximum velocity did not penetrate a shock wave and fast break-up was occurred. Pulsed injection of liquid column generated second shock wave and multiple shock wave.

Research on the base cavity of a sub-launched projectile

The finite volume method based on a multiphase model is adopted to solve the Reynolds-Averaged Navier-Stokes (RANS) equations, which takes into account the effects of fluid compressibility, viscosity, gravity, medium mixture and energy transfer of water and combustion gas. The program Fluent User Define Function (UDF) module combined with the dynamic mesh method is employed to simulate the coupling flow field of combustion gas, water field and trajectory of projectile. The results show that the volume of gas cavity at the bottom of projectile and tail pressure will fluctuate after bottom of the projectile leaving the launch tube. The cause of the fluctuation is analyzed and its effects on the trajectory of projectile are presented. The numerical and experimental results agree well with each other.