Magnetic nozzles are convergent-divergent applied magnetic fields which are commonly used in electric propulsion, manufacturing, and material processing industries. This paper studies the previously overlooked physics...
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Magnetic nozzles are convergent-divergent applied magnetic fields which are commonly used in electric propulsion, manufacturing, and material processing industries. This paper studies the previously overlooked physics in confining the thermalized ions injected from a near-uniform inlet in the magnetic nozzle. Through fully kinetic planar-3V particle-in-cell (PIC) modeling and simulation, an electric potential barrier is found on the periphery of the nozzle throat, which serves to confine the thermalized ions by the electric force. With the initial thermal energy as driving force and insufficient magnetic confinement, the ions overshoot the most divergent magnetic line, which results in the accumulation of positive space charges around the throat. The accumulated charges would create an ion-confining potential barrier with limited extent. Apart from the finite-electron Larmor radius (FELR) effect, two more factors are put forward to account for the limited extent of the potential barrier: the depletion of ion thermal energy and the short-circuiting effect. The influences of inlet temperature ratio of ions to electrons and magnetic inductive strength B0 are quantitively investigated using the PIC code. The results indicate that the potential barrier serves as a medium to transfer the gas dynamic thrust to the magnetic nozzle while providing constrain to the ions, like the solid wall in a de Laval nozzle. In high-B0 regime, the finite-ion Larmor radius (FILR) effect becomes dominant rather than the FELR effect in the plasma confinement of magnetic nozzles.
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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ISBN:
(数字)9781538679692
ISBN:
(纸本)9781538679708
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 modular design in order to compare three different magnetic field configurations: A) nominal, B) orthogonal magnetic field and C) high magnetic field. In Hall Thrusters the magnetic field is used to confine the electrons and create highly ionized plasma. Configuration A and configuration B were chosen to compare two different topographies of the magnetic field with two different magnetic field gradients and to study their influence in the plasma discharge and thruster performance. Both configurations where derived assuming Bohm diffusion as the dominant process in the plasma discharge. If instead of Bohm diffusion it is considered electron-wall collisions as main mechanism in the electron transport then a higher magnetic field is required and in consequence configuration C was designed. These three configurations are intended to provide a better understanding of the influence of the magnetic field in the thruster discharge.
In this paper, the formation problem of unknown multi-quadrotor systems with underactuation and nonlinearities is addressed. A formation controller including a position controller and an attitude controller is designe...
In this paper, the formation problem of unknown multi-quadrotor systems with underactuation and nonlinearities is addressed. A formation controller including a position controller and an attitude controller is designed. The designed formation controller is based on hierarchical scheme and reinforcement learning method is used to learn the control weights of the formation controller. A simulation of formation of multiple quadrotor systems shows the effectiveness of the proposed controller.
In this paper, a reinforcement learning based control law is proposed to solve the attitude synchronization problem of the leader-following multi-quadrotor systems. The overall system is composed of a team of quadroto...
In this paper, a reinforcement learning based control law is proposed to solve the attitude synchronization problem of the leader-following multi-quadrotor systems. The overall system is composed of a team of quadrotors, modeled with highly nonlinear and coupled dynamics. An optimal control solution is obtained by solving an augmented HamiltonJacobi-Bellman equation. A reinforcement learning approach is used to learn the optimal control law. simulation results are provided to verify the effectiveness of the proposed controller.
This work presents the difficulties associated with the miniaturization of Hall Thruster engines and how state of the art materials and new manufacture techniques can potentially solve these problems. Hall Thrusters a...
This work presents the difficulties associated with the miniaturization of Hall Thruster engines and how state of the art materials and new manufacture techniques can potentially solve these problems. Hall Thrusters are electric propulsion systems that require specific magnetic field topography and uniform propellant distribution for optimal operation which is difficult to achieve with typical materials and by conventional manufacturing methods in miniaturized engines. To keep the optimal magnetic field distribution at small thruster sizes, it is shown that new alloys of SmCo permanent magnets can generate the desired magnetic field distribution and that their high-temperature resistance properties assure its operation temperature will be under the maximum operational temperature. In addition, whereas for the small dimensions required for the anode traditional manufacture methods only allow for simple designs, it is explained how the implementation of 3D-printing techniques can improve the uniformity in the azimuthal distribution of the propellant by allowing complex geometries in the design of the anode that are unattainable with traditional manufacturing.
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