The incidence angle of the pulsed laser has a significant influence on the performance of laser propulsion. To further reveal the impulse coupling mechanism when the pulsed laser is obliquely incident irradiated, a plume observation system with high spatial and temporal resolution and a plasma plume emission spectrometry system were designed and built. In this paper, time-resolved images and the plasma emission spectrum were investigated for pulsed laser irradiation of aluminum targets at 0°, 15°, 30°, 45°, 60°, and 75° in a vacuum environment. The results of the study show that the plasma plume is always ejected along with the normal phase of the target surface. Additionally, the electron number density, the plume radiation intensity, and the plasma temperature weaken as the angle of incidence increases. Besides, a high-precision three-dimensional spectral collection platform was built to finely study the two-dimensional spatial distribution of the plasma parameters in the flow field. The results show that the electron number density decreases rapidly with increasing distance from the target surface. In conclusion, the foundation is established for the analysis of the impulse coupling mechanism of pulsed laser oblique incidence.
The laser electromagnetic hybrid propulsion is a propulsion method that generates thrust through the synergistic action of laser ablation propulsion and electromagnetic propulsion. Laser ablation propulsion and electromagnetic propulsion complement each other to produce better thrust performance. In this paper, the emission spectra of pulsed electromagnetic propulsion (PEP) and laser assisted pulsed electromagnetic propulsion (LAPEP) are studied, and the composition, temperature and density of plasma plume are calculated. The evolution of plasma plumes of laser electromagnetic combined propulsion (LEHP) in the initial stage of formation and in the discharge chamber are studied by using a high speed camera. The results show that charged particles in PEP and LAPEP plumes are mainly C+, F+, C++ and F, among which C+ has the highest luminescence intensity of plasma. Calculated with the C+ spectral line intensity of plasma and the multi-spectral method, the electron temperature of PEP and LAPEP is about 12300K, and the electron density is about 1.2×1026m-3, which the electron temperature and density of LAPEP are slightly higher than those of PEP. In addition, the plasma evolution law and the discharge characteristics of LEHP are different from that of PEP. The plasma evolution process of PEP is continuous and regular, and the evolution process of LEHP is irregular.
The laser ablation micro thruster uses the target vapor or plasma jet generated by the laser ablation working fluid to obtain the reaction impulse and thrust. The working mode of the laser micro thruster is divided into two types, reflection type and transmission type. In this paper, the influence of plasma treatment on the bonding force between ablation layer and transparent layer is studied in transmission mode, and the influence of different kinds of substrate materials on the mechanical properties of laser ablation is studied. The results show that the surface activity of the PET transparent substrate is greatly improved by the formation of N-C=O or C=O active groups after plasma treatment, and the interlayer bonding force of the target band is increased by about 50%. Thus the peeling of the ablation layer and the transparent layer around the ablation pit after laser ablation target zone is eliminated. The light transmittance of PET substrate material is better than that of PI substrate material. In the case of the same thickness of ablation layer, the single pulse impulse and specific impulse of PET substrate target band are better than that of PI substrate material target band. The punching is better than the PI base material target tape. The optimization of target parameters provides guidance for further application of laser propulsion.
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