Launch Safety Research Articles

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.

Numerical Method of Propulsion Concept: Partially Cut Multiaperture Stick Propellant

The partially cut Multiaperture stick propellant is a new concept charging structure. In this paper, in order to accurately obtain the change and development process of the two-phase flow field in different stages of the whole interior ballistic process in this propulsion concept system, a coupled calculation model of computational interior ballistic is established, which converts the Euler-Lagrange method to the Euler-Euler method. Firstly, at the initial stage of ignition, the Euler-Lagrange method is used to describe the flow field. During this period, the gas phase is based on Euler coordinates, while the solid phase is based on Lagrangian coordinates. After the projectile starts, the partially cut Multiaperture stick propellant is fractured into granular propellant. The flow field is converted to describe by the Euler-Euler method by using the initial mapping method. Finally, by comparing the calculated results with the experimental results, the maximum pressure error is only 0.54%, which verifies the accuracy and effectiveness of the coupling calculation method. It effectively captures the distribution of the physical parameters in the combustion chamber, providing a new research method for the computational interior ballistic of the propulsion concept. Based on this method, the pressure distribution in the propulsion concept system is obtained, and no obvious shock waves and expansion waves are seen, indicating that the charge scheme of partially cut Multiaperture stick propellant can improve launch safety.

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>

Retracted: Study on Optimization of Interior Ballistic Performance of Cased Telescoped Ammunition Based on Improved Firefly Algorithm

AbstractConsidering that the evolution operators of common optimization algorithms such as genetic algorithm has a poor convergence speed and solution accuracy in the interior ballistic performance optimization of artillery, an improved firefly algorithm is selected for the interior ballistic performance optimization of cased telescoped ammunition (CTA). It is applied to the interior ballistic mathematical model of CTA to carry out single‐objective optimization and multi‐objective optimization respectively. The results show that in the single‐objective optimization, the muzzle velocity obtained by using the improved firefly algorithm is larger than other commonly used optimization algorithms. Under the constraints of maximum chamber pressure and relative burnout point, the muzzle velocity can be increased by about 30 m/s. In the multi‐objective optimization, three sub‐objectives of muzzle velocity, ballistic efficiency and muzzle pressure are considered respectively, and the multi‐objective firefly algorithm is applied to comprehensively optimize the interior ballistic performance of CTA. Then, the results are compared with the commonly used multi‐objective optimization algorithms, such as non‐dominated sorting genetic algorithm version II (NSGA‐II) and non‐dominated sorting genetic algorithm version III (NSGA‐III), the solution results are a series of Pareto optimal solutions. The obtained optimization results improved the interior ballistic performance and launch safety, providing reference for the reasonable matching of charge structure parameters and the selection of optimization algorithm upon the interior ballistic performance optimization of CTA to some extent.

AN OVERVIEW OF METHODS AND TECHNICAL MEANS OF SPACE DEBRIS REMOVAL FROM LOW EARTH ORBITS

Debris in Earth's orbit poses a significant threat to existing spacecraft and hinders the safe launch of new spacecraft. This paper discusses various methods of space debris removal from orbit. In particular, active, passive, and combined methods are considered. The possibility of using suborbital rockets to launch the removal system into orbit is also considered. The purpose of this paper is to review existing methods and technical means of space debris de-orbiting and analyze and identify promising areas for the development of such systems. A patent analysis was conducted for the period from 2002 to 2022. Modern scientific works on various methods of space debris removal were also analyzed. The papers on the combined method of space debris removal were analyzed separately. Non-standard approaches to space debris removal are considered. In particular, the possibility of using suborbital launch vehicles to launch removal systems into orbit is considered. As a result of the work, the current state of development of methods and technical means for space debris removal was determined. It has been found that the most commonly patented and studied in scientific papers are technical means based on the passive removal method. At the same time, the active method receives less attention in scientific papers. Because of this, it has been established that the study of passive and combined methods and the development of technical means based on these methods are promising areas. It was found that the combined method is promising, but little was studied, and the basic requirements for systems using suborbital launch vehicles were also identified. This work allowed us to summarize the current state of the problem of space debris management and identify the most promising areas for the development of space debris removal systems.

Thermo-mechanical coupling simulation of PBX explosive charge in launch environment

The distribution of internal stress and temperature of explosive charge in launch environment is significant to determine the launch safety of explosive charge. PBX is composed of energetic particles, binder and metal powder, hence it can perform the viscoelastic mechanical properties under the external force loading condition. The generalized Maxwell constitutive equation is embedded into LS-DYNA program by secondary development technology, and verified rational after the simulation of launch safety experiment of explosive charge. Utilizing the constitutive equation and considering the influence of viscoelastic work and chemical reaction heat, the distribution of internal stress and temperature of explosive charge in launch environment is acquired. The results indicate that the viscoelastic work and chemical reaction heat produce a 4K highest temperature rise of explosive charge, the explosive charge without defects cannot ignite in the launch process. The results provide a certain guiding significance for the launch safety evaluation of explosive charge.

Research on the launch safety test of explosive charge under simulated launch environment

Aiming at the launch safety problems of breech blow caused by the current harsh artillery launch environment, the mechanism of breech blow caused by explosive charges and the current research status of explosive charge launch safety tests are summarized. In order to consider the influence of friction on the ignition of the explosive due to the relative movement between the explosive and the shell caused by the high-speed rotation of the projectile during the launch process, the simulation of the explosive charge launch environment was carried out based on the projectile launch dynamics equations and the internal ballistic equations, and then a new device for the launch safety test of explosive charges is established to comprehensively simulate the longitudinal overload and high-speed rotation launch environment of explosive charges in the bore. The test results show that the test device can simulate the maximum rotating speed of the projectile in the bore and the stress process at the bottom of the explosive charge during the launch process, which truly reproduces the launch environment of explosive charge. The research in this paper provides a new means for the launch safety test and evaluation of explosive charges.

Influence of propellant charge structure parameters on the intergranular compression stress at projectile bottom

The chamber explosion caused by propellant charge is essentially the large-scale fragmentation of the propellant charge at the projectile bottom, and the inter-granular compression stress is crucial to the fragmentation. In order to figure out the influence of propellant charge structures on the inter-granular compression stress between propellant particles, an interior ballistic twophase flow model and simulation system is established with a large caliber howitzer as the research object. Then the effects of ignition hole diameter, hole breaking pressure, arc thickness and charge amount on the inter-granular compression stress between propellant particles are studied respectively. The results show the significant effects of arc thickness and charge amount on the inter-granular compression stress between propellant particles, but the little effect of ignition hole diameter and hole breaking pressure. By improving the aforementioned propellant charge structure, the inter-granular compression stress can be effectively reduced by more than 5%while the original ballistic performance is guaranteed. The method presented in this paper provides a certain theoretical basis for improving the launch safety of the propellant charge.

Analysis on affecting factors of the fragmentation degree of propellant charge

It has been demonstrated in theory and experiments that the breech blow caused by the propellant charge is almost due to the propellant charge fracture. This paper discusses and analyses the effects of temperatures (-40°C, 15°C, 50°C) and packing patterns (random, horizontals and verticals) on fragmentation degree of propellant charge under the given impacting load condition, through utilizing the dynamic compression and fracture test of propellant charge as well as initial dynamic vivacity of propellant charge. The test results reveals that the propellant charge at -40°C has a largest fragmentation degree than other temperatures. Moreover, the fragmentation degree of the propellant charge packed vertically is also larger than horizontal and random packing patterns. The fragmentation degrees of various random packing have no significant differences. This test of launch safety of propellant charge can be repeated easily, which is verified scientific.

Optimization for dynamic compression and fracture test of propellant charge

The excessive fracture of propellant charge is the key to reveal the breech blow caused by propellant charge. The dynamic compression and fracture test of propellant charge is the only existing simulation approach to reproduce the propellant charge fracture process under launch environment. However, the simulation of the compression stress of propellant charge is essentially a process with trial and error, meantime, the dispersion of the compression stress obtained under the constant experiment condition is a stumbling block in launch safety research. To solve them, this paper attempts to establish a regression model of compression stress of propellant charge through several machine learning methods, and then the optimal model with high generalization ability is demonstrated by experiment. On account of the distribution test of model error, this method can predict the compression stress test results as well as the corresponding range with high confidence. Overall, this method makes it feasible to provide an effective reference for test conditions to acquire the target compression stress of propellant charge, which can significantly optimize the dynamic compression and fracture test of propellant charge and shorten the research cycle.

Active Learning Strategy for Surrogate-Based Quantile Estimation of Field Function

Uncertainty quantification is widely used in engineering domains to provide confidence measures on complex systems. It often requires to accurately estimate extreme statistics on computationally intensive black-box models. In case of spatially or temporally distributed model outputs, one valuable metric results in the estimation of extreme quantile of the output stochastic field. In this paper, a novel active learning surrogate-based method is proposed to determine the quantile of an unidimensional output stochastic process with a confidence measure. This allows to control the error on the estimation of a extreme quantile measure of a stochastic process. The proposed approach combines dimension reduction techniques, Gaussian process and an adaptive refinement strategy to enrich the surrogate model and control the accuracy of the quantile estimation. The proposed methodology is applied on an analytical test case and a realistic aerospace problem for which the estimation of a flight envelop is of prime importance for launch safety reasons in the space industry.

A test method for launch safety of explosive charge accurately simulating launch overload

ABSTRACT In this paper, the generalized Maxwell constitutive equation is embedded into LS-DYNA program by secondary development technology, the projectile launching process is numerically calculated, and the stress distribution of explosive charge in the launching process is described. According to the calculation results, the explosive charge launch safety simulator for the research of explosive charge launch safety is designed and developed. Then the experiment is carried out, and the dynamic behavior and ignition process of explosive charge were obtained. Finally, a quantitative evaluation method for the launch safety of explosive charge is established, and the launch safety of the PBX is evaluated.

Safe launch of a robotically assisted mitral valve repair program in a single center: experience of initial 20 cases under the Center for Minimally Invasive Surgery.

Robotically assisted mitral valve repair was approved by the Japanese government in April 2018. However, understanding robotic surgery involves steep learning curves of surgeons and dedicated cardiac teams. The Center for Minimally Invasive Surgery (CMIS) of Tottori University Hospital is a multidisciplinary organization established in 2011 with seven surgical departments. In this study, we report strategies for improving the safety of robotic surgery in the CMIS and early results of robotic mitral valve repair at our hospital. We reviewed the first 20 patients who underwent robotic primary mitral valve repair, including concomitant procedures, from October 2019 to September 2021 under the supervision of the CMIS. Before starting the program, the CMIS requires setting console time limit to 180min and implementing risk management strategies through simulation training for various mechanical failures. Mitral valve repair was completed in all patients. There was no in-hospital or 30-day mortality. No conversion to median sternotomy was necessary. The analysis of mitral pathology revealed 1 case of functional mitral regurgitation, 12 cases of posterior lesions, 3 cases of anterior lesions, 3 cases of bileaflet lesions, and 1 case of commissural lesion. The average cross-clamp time was 133 ± 27min. Sixteen cases had trace mitral regurgitation postoperatively, and 4 cases had mild mitral regurgitation. The median (interquartile range) postoperative hospital stay was 10 (8.5-12.5) days. Robotically assisted mitral valve repair was performed safely with assistance from the multidisciplinary CMIS, and the early results were satisfactory without compromising clinical outcomes.

Design and Performance of Armature Surface Coating for Electromagnetic Launcher

Armature is the key component of electromagnetic launcher (EML), but in the process of launching, its working environment is bad and the surface is seriously worn. Excessive wear will seriously weaken the mechanical properties of armature and affect the launching safety. Therefore, it is necessary to deal with the surface state of armature to reduce wear and improve the performance of armature. First, the properties of the candidate materials are analyzed. According to the principle of maximum current carrying capacity per unit mass, aluminum is the most suitable material for armature manufacturing. At the same time, the defects of material selection in single material system are pointed out. Second, based on the above problems, the surface coating design scheme is proposed. From the point of view of material melting point and hardness, it is proposed that tungsten can be used as the coating material for armature surface. According to the wear amount of armature tail under launch condition, the coating shape and thickness are designed. The best coating forming process is determined by calculating the shear force between coating and substrate; finally, the effect of the coating on the electric contact performance, system efficiency, and projectile gouging threshold velocity is analyzed. The results show that the maximum shear force between the coating and the substrate is above 171 MPa under the launching condition, and the laser cladding technology can meet the process requirements. After coating treatment, the contact resistance between the armature and rail (AR) increases by 6%, which has little effect on the system efficiency. Although it will affect the projectile gouging threshold velocity, it can be improved by modifying the tungsten coating or rail surface treatment. The analysis results are of great significance to reduce the armature wear, improve the contact performance between the AR, and improve the launch safety.

Numerical study on jet noise suppression with water injection during one-nozzle launch vehicle lift-off

The launch vehicle will experience extreme acoustic environment at lift-off, which will cause the invalidation and destruction of the aerospace equipment, and reducing noise is of great significance for improving launch safety. In this paper, the numerical simulation of gas–liquid two-phase flow and its acoustic field is carried out, and the flow field is simulated by the discrete phase model (DPM), second-order Roe format, Scale-Adaptive Simulation (SAS) and three-dimensional Navier–Stokes. Based on the analysis of the flow field, the acoustic analogy integration method (FW-H) is used to predict the jet noise at the observation position. The influence of the water different injection angles and mass flow rate ratios are studied, and the results show that water injection not only reduces the temperature, velocity and vorticity at the gas–liquid interface, and the temperature at the bottom of the jet deflector, it also significantly reduces the jet noise. The total sound pressure level can be reduced to 6.92 dB by appropriate selection of the water injection angles and water injection mass flow rates. The numerical method established in this paper provides a useful tool for the design and analysis of water injection noise reduction for high-thrust multi-nozzle launch vehicle.

Evaluation of the Mechanical Failure Criterion to Consider the Triple Base Propellant Safety Life: Application of Sustainable Renewables for Environmental Hazards

Implementation of clean energy and renewables is essential for the consideration of environmental impact because it can be implemented in supply chain networks and sustainable management procedures for safety. In order to study the safety life failure criterion of a triple base propellant under the failure mode of mechanical properties, an accelerated aging test, an evaluation method for the launch safety test of gun propellant charge, and a compressive strength test were used. The failure criterion of mechanical properties was obtained by researching the correlation between launch safety change and mechanical property change of samples. Berthelot’s equation was used to predict the safety life of the triple base propellant. The results show that the mechanical failure criterion is “27% reduction of maximum compressive strength.” The safety life at 25°C and 75% humidity is 13.77 years.

Finite Volume Method for the Launch Safety of Energetic Materials

It is important to examine the ignition of energetic materials for launch safety. Given that there is a paucity of experimental tests, numerical simulations are important for analysing energetic materials. A computer program based on the finite volume method and viscoelastic statistical crack mechanics model is developed to study the ignition of energetic materials. The trends of temperature and stress of energetic materials subjected to projectile base pressure are studied by numerical examples. The results are compared with those in an extant study, which verified the correctness of the proposed method. Additionally, the relationships between the temperature increase and nonimpact ignition of energetic materials were analysed. The results show that when the temperature at the bottom of the explosive rises to a certain value, it will cause the explosive to ignite. This research has significance to the study of the base gap of explosives, and it provides a reference for launch safety evaluation of energetic materials.

Influences of the Random Stacking and Charge's Diameter on Compression and Fracture Process of Propellant Charge

AbstractAfter decades of unremitting research on the launch safety of propellant charge at home and abroad, it is gradually recognized that the fractured propellant charge generated by the compression process of propellant particles is the leading cause of chamber explosion. The large numbers of particles in propellant charge inevitably bring out the complexity in describing the fracture process under impact load in description. The discrete element method is applied to study the influences of the random stacking configurations of propellant charge and the charge diameter on the compression and fracture process of propellant charge in this paper. The results show that the random stacking of propellant bed influences little on the fracture process under the same impact load. When the diameter of propellant charge is larger than a certain value, the charge's diameter has little influence on the fracture process.

Research on parameter matching characteristics of pneumatic launch systems based on co-simulation

AbstractPneumatic launch systems for Unmanned Aerial Vehicles (UAVs), including mechanical and pneumatic systems, are complex and non-linear. They are subjected to system parameters during launch, which leads to difficulty in engineering research analysis. For example, the mismatch between the UAV parameters and the parameter design indices of the launch system as well as the unclear design indices of the launching speed and overload of UAVs have a great impact on launch safety. Considering this situation, some studies are presented in this paper. Taking the pneumatic launch system as a research object, a pneumatic launcher dynamic simulation model is built based on co-simulation considering the coupling characteristics of the mechanical structure and transmission system. Its accuracy was verified by laboratory test results. Based on this model, the paper shows the effects of the key parameters, including the mass of the UAV, cylinder volume, pressure and moment of inertia of the pulley block, on the performance of the dynamic characteristics of the launch process. Then, a method for matching the parameter characteristics between the UAV and launch system based on batch simulation is proposed. The set of matching parameter values of the UAV and launch system that satisfy the launch take-off safety criteria are calculated. Finally, the influence of the system parameters of the launch process on the launch performance was analysed in detail, and the design optimised. Meaningful conclusions were obtained. The analysis method and its results can provide a reference for engineering and theoretical research and development of pneumatic launch systems.

Research progress on explosives for naval gun shell and its launching safety

<p indent="0mm">To investigate the launch safety problems in the application of powerful naval gun ammunition, this paper analyzes and studies the development of domestic and foreign explosives and weaponry for naval gun ammunition, the research equipment for explosive charge launching safety, impact mechanism of explosive charge launching safety, and the design of numerical simulation and equivalent test for explosive charge launching safety. Results show that although the explosive charge of naval gun ammunition varies among countries, the principle of the test device used to study the explosive charge launching safety is basically the same. To verify whether the explosive charge meets the launch safety requirements, the recoil force stress and its response to explosives in the launching process is simulated. Additionally, the relevant test and research results prove that the launching safety performance of explosive charge can be effectively enhanced by improving the charge quality and reducing the charge defects. By exploring the explosive formula design and charging technology, avoiding the hot spot of explosives in a complex stress launching environment, such as adiabatic compression and shear, is a crucial technical measure, as well as improving the launching safety of naval gun shell explosive charge.