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BackgroundWith the development of human aerospace industry, it is necessary to develop propulsion systems suitable for different space mission scenarios. MegnetoPlasmaDynamic thruster (MPDT), which is similar to the principle of magnetic confinement fusion, is a typical representative of electromagnetic thruster, which stands out among many electric thrusters because of its superior performance in thrust power ratio and specific impulse. Anode power deposition is the result of the interaction between plasma and wall during MPDT operation. It is one of the main mechanisms of power loss of this type of thruster, accounting for 40%~90% of the total power, which seriously reduces the efficiency of thruster.PurposeThis study aims to solve the problem of low efficiency of thruster by investigating the influence of anode radius on the efficiency of thruster from the perspective of anode power deposition.MethodsFirst of all, based on MagnetoHydroDynamic (MHD) equations, numerical models for radial discharge parameters and physical model for anode power deposition were established. Then, the influences of anode radius on discharge parameters, anode power deposition and anode power deposition fraction were studied on the basis of these models by numerical calculation method. Finally, a water-cooled structure anode was designed, and the effectiveness of its heat dissipation structure was verified by thermal simulation.ResultsThe results show that with the increase of anode radius, the electron density and ion velocity are increased, the anode power deposition fraction is decreased whilst the anode power deposition is increased. The thruster efficiency is improved by increasing the anode radius. The thermal simulation results show that when the input power deposition of the water-cooled structure anode is about 3 kW, the corresponding temperature difference of the anode cooling water is 5 K.ConclusionsThis study verifies the reliability of the physical model of anode power deposition, indicating that increasing the anode radius is an effective means to improve the efficiency of the thruster.

BackgroundElectric propulsion systems, compared to traditional chemical propulsion, offer longer operational lifespans and lower fuel consumption in space missions, garnering significant attention in recent years. However, for high-power Hall effect electric thrusters developed based on controlled fusion concepts, measuring thrust proves challenging due to the high-temperature environments required for ionizing propellants in electric thruster, resulting in the generation of hot plasma plumes during operation. As a result, traditional thrust measurement methods are unable to accurately measure the thrust.PurposeThis study aims to accurately measure thrust during ground testing of electric thrusters for precise control of the spacecraft's attitude and orbit maintenance.MethodsFirstly, a thrust measurement platform based on flexible beam structure was designed and implemented with capability of measuring the thrust generated by electric thrusters in high-temperature. Simultaneously, a calibration system was built to verify the stability and repeatability of the thrust measurement results. Then, simulation analysis was conducted on the structural mechanics and thermal coupling field of the thrust measurement system under different operating conditions. Finally, the variable specific impulse magnetoplasma rocket (VASIMR) was taken for experimental thrust measurement of its electric propulsion system.ResultsThe experimental results of VASIMR indicate the thrust is 266.5 mN measured in real time at the central magnetic field intensity of 0.2 T with a mass flow rate of 20 mg∙s-1.ConclusionsThe thrust measurement platform based on the bending beam structure can meet the measurement requirements of VASIMR, providing valuable references for subsequent experiments.

This study focuses on the synthesis of Fe@Cu-Ni materials by direct reduction for Rhodamine B (Rh B) degradation. Fe@Cu-Ni pairs of the catalytic materials were characterized by SEM, XRD, and XPS. The degradation mechanism of the Fe@Cu-Ni catalyst and the degradation pathway of Rh B were analyzed. The dendritic structure of Fe@Cu-Ni provides divergent paths for electron transport and enrichment, which is conducive to charge transfer. Cu2O on the end of electron transfer channel and Cu with Ni doping played an important role for H2O2 generation through oxygen reduction reaction (ORR). The ·OH, which was produced from the catalyzation by in situ H2O2, was a key radicals for Rh B degradation. The intermediate products of Rh B degradation were identified by LC-MS/MS and the degradation intermediates revealed that the degradation function for Rh B mainly resulted from the synergistic action of ·H and ·OH. The degradation efficiency of Rh B can reach 98.7% at pH=2, Fe@Cu-Ni catalyst dosage of 0.5 g/L, and Rh B concentration of 20 mg/L. The study highlights the potential of Fe@Cu-Ni composites to eliminate dye residues. [ABSTRACT FROM AUTHOR]

Acoustic hyperbolic metamaterials are artificial materials with hyperbolic dispersion characteristics and strong anisotropy. Their negative refractive properties are the theoretical basis for studying the implementation of high-resolution focused superlenses. In response to the problem that the recognition of far-field noise sources is limited by the resolution of 0. 5 times wavelength acoustic Rayleigh diffraction recognition, combined with the excellent control effect of acoustic metamaterials on sound waves, a hyperbolic metamaterial that can achieve sub wavelength super-resolution imaging is introduced, and its negative refractive characteristics are used to design an acoustic hyperbolic structure for working at a frequency of 2 271. 5 Hz. The dispersion and negative refraction characteristics of the hyperbolic structure of this configuration were analyzed, and the results show that, the group velocity direction of sound waves propagating in this hyperbolic metamaterial is perpendicular to the wave vector and follows the normal direction of the dispersion curve. The research in this paper provides some design references for realizing arbitrary regulation of sound wave and elastic wave, as well as focusing, locating, identifying and amplifying noise sources. [ABSTRACT FROM AUTHOR]