The coupling region of a Hall thruster with a hollow cathode is the region between the cathode and the thruster *** characteristics of plasma in that region are complicated and strongly associated with the thruster wo...
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The coupling region of a Hall thruster with a hollow cathode is the region between the cathode and the thruster *** characteristics of plasma in that region are complicated and strongly associated with the thruster working conditions and the cathode *** this paper,a laboratory 100 W class magnetically shielded Hall thruster was coupled with a hollow *** imaging and electrostatic probe were employed to monitor and scan the plasma *** characteristics in the coupling region in non-self-sustained mode and self-sustained mode were *** of the coupling plume with the cathode position was *** show that,when turning the thruster into self-sustained mode or moving the cathode further away axially,the discharge current can be reduced by 6.4–10.6%restraining the electron current and improving *** particular,when the cathode is moved further,the electron conduction near the channel walls is *** electron current is reduced by 27.4%and the ion beam current is increased by 7%.Overall,this work shows that the working mode of the thruster and the position of the cathode greatly affect the coupling plasma *** play an important role in improving the utilizations of propellant and current.
The Vlasov-Poisson equation is one of the most fundamental models in plasma physics. It has been widely used in areas such as confined plasmas in thermonuclear research and space plasmas in planetary magnetospheres. I...
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To minimize the mass and increase the bearing failure load of composite double-lap bolted joints,a three-step optimization strategy including feasible region reduction,optimization model decoupling and optimization wa...
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To minimize the mass and increase the bearing failure load of composite double-lap bolted joints,a three-step optimization strategy including feasible region reduction,optimization model decoupling and optimization was *** feasible region reduction,the dimensions of the feasible design region were reduced by selecting dominant design variables from numerous multilevel parameters by sensitivity analyses,and the feasible regions of variables were reduced by influence mechanism *** model decoupling,the optimization model with a large number of variables was divided into various sub-models with fewer variables by variance *** the third step,the optimization sub-models were solved one by one using a genetic algorithm,and the modified characteristic curve method was adopted as the failure prediction *** on the proposed optimization method,optimization of a double-lap single-bolt joint was performed using the ANSYS®*** results show that the bearing failure load increased by 13.5%and that the mass decreased by 8.7%compared with those of the initial design of the joint,which validated the effectiveness of the three-step optimization strategy.
Fixed threshold models have been widely used in active fire detection products. However, its accuracy is limited due to the complexity of setting up thresholds. Artificial neural network (ANN) is capable of learning f...
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With the rapid development of remote sensing technology, it is possible to obtain continuous video data from outer space successfully. It is of great significance in military and civilian fields to detect moving objec...
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In this work,a force measurement system is proposed to measure the thrust of plasma microthruster with thrust magnitude ranging from sub-micro-Newtons to hundreds *** thrust measurement system uses an elastic torsiona...
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In this work,a force measurement system is proposed to measure the thrust of plasma microthruster with thrust magnitude ranging from sub-micro-Newtons to hundreds *** thrust measurement system uses an elastic torsional pendulum structure with a capacitance sensor to measure the displacement,which can reflect the position change caused by the applied force perpendicular to the pendulum *** the open-loop mode,the steady-state thrust or the impulse of the plasma micro-thruster can be obtained from the swing of the pendulum,and in the closed-loop mode the steady-state thrust can be obtained from the feedback force that keeps the pendulum at a specific *** thrust respond of the system was calibrated using an electrostatic weak force generation *** results show that the system can measure a thrust range from 0 to 200μN in both open-loop mode and closed-loop mode with a thrust resolution of 0.1μN,and the system can response to a pulse bit at the magnitude of 0.1 m N s generated by a micro cathode arc *** background noise of the closed-loop mode is lower than that of the open-loop mode,both less than 0.1 m N/Hz in the range of 10 mHz to 5 Hz.
Asteroid flybys near Earth pose significant risks of potential impacts on Earth while simultaneously offering valuable opportunities for exploration missions. This study investigates the dynamics of a satellite transf...
Asteroid flybys near Earth pose significant risks of potential impacts on Earth while simultaneously offering valuable opportunities for exploration missions. This study investigates the dynamics of a satellite transferring from Earth to an asteroid during a flyby, modeled by the Hyperbolic Restricted Three-Body Problem (HR3BP). Previous research has mainly focused on the dynamical behaviors of boundary manifolds in the HR3BP. However, boundary manifolds only exist in theoretical and radical situations and cannot be applied to the satellite trajectory design. To address this limitation, this work proposes a novel approach for satellite transfer trajectories to an asteroid by developing the applications of Finite-Time Lyapunov Exponent (FTLE) fields. By applying the method of FTLE fields, one of the libration points, the L 1 point, is proven to hold the property of an energy-efficient transfer window in the HR3BP. Then, transfer trajectories to an asteroid are generated and patched with multiple trajectories to achieve lower energy cost transfer from Earth to the asteroid than before. Numerical simulations indicate that the proposed approach reduces the energy cost of transfer trajectories by 23 % compared to the conventional Hohmann transfer approach. Additionally, to expedite the generation of FTLE fields, this study integrates the differential algebra (DA) method to reduce the generation time for FTLE fields to approximately 11 % of the time required without the DA.
Erosion can influence cathode life,and is thus considered to be one of the main factors limiting the application of applied-field magnetoplasmadynamic *** this paper,erosion sites on graphite cathodes are studied so a...
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Erosion can influence cathode life,and is thus considered to be one of the main factors limiting the application of applied-field magnetoplasmadynamic *** this paper,erosion sites on graphite cathodes are studied so as to identify the influence of applied magnetic field and the ratio of propellant mass flow rate supplied from cathode and *** experiment results show that the application of applied magnetic field can significantly reduce the erosion rate of the cathode compared to that without magnetic *** erosion sites on the cathode vary with the relative position of the convergent-divergent magnetic field,and are mainly distributed in the divergent part of the *** erosion sites on the cathodes are found to be related to the propellant *** decreasing anode mass flow rate enlarges the range of *** results are much helpful for the analysis of cathode erosion site location since they provide evidences of erosion mechanisms and point out the directions for further research.
A 100 W radial scaled Hall Thruster has been designed and manufactured using as reference design the D-55 thruster with anode layer (TAL). The magnetic field required is provided by permanent magnets following a modul...
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In this paper, a novel synthetical multi-attribute evaluation (MAE) approach for small launch vehicles (SLVs) is proposed. In addition to traditional technical performances, other attributes, including cost, operabili...
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In this paper, a novel synthetical multi-attribute evaluation (MAE) approach for small launch vehicles (SLVs) is proposed. In addition to traditional technical performances, other attributes, including cost, operability, manufacturability, flexibility and safety/environmental-friendly characteristics, are considered for comparison. Three chemical propulsion systems, which are solid rocket motor (SRM), liquid rocket engine (LRE), and hybrid rocket motor (HRM), are adopted for the designoptimization of a SLV and comparison of the multi-attribute evaluations. Three disciplines are considered to establish the system design model of the SLV, including propulsion, structure and overall design. The Ziolkovsky formula is used to estimate the total velocity increment needed for the orbit injection. Cost models for different propulsion are established respectively. And two performance parameters, the taking-off mass and total cost of the launch vehicle, are selected as the design targets of the multi-objective optimization, which aims at the same design reference mission, 100kg payload with injection at 300km circle low earth orbit. Moreover, fuzzy decision method is adopted to quantitatively characterize expert evaluation in MAE. In order to synthetically evaluate the suitability of each propulsion system, TOPSIS multi-standard decision scheme is implemented based on entropy weight method. The results show that all MDO models acquire a series of solutions with two objectives (takeoff mass and total cost) for SLV. Aiming at the same index, SLV powered by SRM has the smallest takeoff mass, while SLV powered by HRM emerges the lowest cost. Total mass emerges significant positive correlation with total cost, while Pareto front indicates that negative correlation exists between total cost and takeoff mass at the range of whole design space. The proposed synthetical MAE approach is proved to be flexible for SLV design, and can be extended to other attributes. Otherwise the HRM is
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