A novel launch dynamics measurement system for multiple launch rocket system and comparative analysis with numerical simulations

In this paper,a novel launch dynamics measurement system based on the photoelectric sensor pair is built.The actual muzzle time(i.e.a time duration that originates from the initial movement to the rocket's departure from the muzzle)and the muzzle velocity are measured.Compared with the classical methods,the actual muzzle time is obtained by eliminating the ignition delay.The comparative analysis method is proposed with numerical simulations established by the transfer matrix method for multibody systems.The experiment results indicate that the proposed measurement system can effectively measure the actual muzzle time and reduce the error of classical methods,which match well with the simulation results showing the launch dynamics model is reliable and helpful for further analysis and design of the MLRS.     

多属性决策中方案属性权重计算的相对熵模型

构建了多属性决策中方案属性权重计算的相对熵模型,给出了求解方法和步骤,并对模型的可行性和有效性进行了验证。研究表明,该模型能够解决专家群体对方案属性重要性意见不一致的问题,从而可以求得最能够让每一个专家都满意的方案属性权重,即最合理权重。     

Controllable combustion behaviors of the laser-controlled solid propellant

Microsatellites have been widely applied in the fields of communication,remote sensing,navigation and science exploration due to its characteristics of low cost,flexible launch mode and short development period.However,conventional solid-propellant have difficulties in starting and interrupting combustion because combustion is autonomously sustained after ignition.Herein,we proposed a new type of solid-propellant named laser-controlled solid propellant,which is sensitive to laser irradiation and can be started or interrupted by switching on/off the continuous wave laser.To demonstrate the feasibility and investigate the controllable combustion behaviors under different laser on/off conditions,the combus-tion parameters including burning rate,ignition delay time and platform pressure were tested using pressure sensor,high-speed camera and thermographic camera.The results showed that the increase of laser-on or laser-off duration both will lead to the decrease of propellant combustion performance during re-ignition and re-combustion process.This is mainly attributed to the laser attenuation caused by the accumulation of combustion residue and the change of chamber ambient temperature.Simultaneously,the multiple ignition tests revealed that the increased chamber ambient temperature after combustion can make up for the energy loss of laser attenuation and expansion of chamber cavity.However,the laser-controlled combustion performance of solid propellant displayed a decrease trend with the addi-tion of ignition times.Nevertheless,the results still exhibited good laser-controlled agility of laser-controlled solid propellant and manifested its inspiring potential in many aspects of space missions.     

International Security,Multiple Public Good Provisions,and The Exploitation Hypothesis

Since the 1960s Olson-Zeckhauser’s (1966) analysis, its ‘exploitation of the great by the small’ has provided economists’ core model of alliance’s provision of security/defense. But with the end of the Cold War, countries’ allocative behavior has diverged markedly from OZ’s predictions for defense as a homogeneous pure public good voluntarily provided. This paper suggests a replacement for OZ, with the essential difference that ‘defense’ rather than being aggregated into their single public good is disaggregated into more realistic categories of self-insurance and self-protection. Because allocative behavior in public good groups is essentially driven by income effects, we concentrate on these, which become complex and conflicted, giving much greater scope for goods-inferiority. The analysis is followed by numerical simulations, which conform to actual experienced allocations in NATO much better than the conventional ‘exploitation’ model.     

Influence of multiple structural parameters on interior ballistics based on orthogonal test methods

Influence of multiple structural parameters on the performance of a gun launch system driven by high-pressure reactive gases is important for structural design and performance adjustment. A coupled lumped parameter model was utilized to predict the propellant combustion, and a dynamic finite element method was applied to approximate the mechanical interactions between the projectile and the barrel. The combustion and the mechanical interactions were coupled through a user subroutine interface in ABAQUS. The correctness and the capability of the finite element approximations in capturing small structural changes were validated by comparing predicted resistance with experiments. Based on the coupled model, the influence of structural parameters of a medium-caliber gun on the system performance was investigated. In order to reduce the research costs, orthogonal tests were designed to investigate the comprehensive effects of the parameters. According to statistical analysis, the important order of the structural parameters on the launching process was obtained. The results indicate that the influence of the width of the rotating band stands out among the studied parameters in the gun. The work provides a method to investigate the influence of multiple parameters on system performance and gives guidance for controlling the system performance.