Baosheng Du

Carbon nanotube paper (CNTP) is a promising material for pulsed laser propulsion, yet the relationship between species-resolved plasma dynamics and momentum generation remains poorly understood. Here, time-resolved imaging was employed to investigate C ₂ and CN plasmas generated from four CNTP composites under nanosecond laser ablation. Plasma front evolution, expansion velocity, emission intensity, and temperature were analyzed. C ₂ dominates the early-stage expansion, and its initial expansion velocity ( v ₀ ) strongly correlates with the impulse coupling coefficient ( C _m ), identifying early-stage C ₂ dynamics as an important kinetic indicator of momentum transfer. Highly graphitized single-walled CNTP generates stronger C ₂ emission but lower plume velocity, whereas multi-walled CNTP composites exhibited faster expansion and higher C _m . These findings establish a direct link between CNTP composite and plasma momentum evolution, providing guidance for the design of high-performance laser propulsion materials.

Laser propulsion is a new conceptual technology that drives spacecraft and possesses advantages such as high specific impulse, large payload ratio, and low launch cost. It has potential applications in diverse areas, such as space debris mitigation and removal, microsatellite attitude control, and orbital maneuvering. Liquid pulse laser propulsion has notable advantages among the various laser propulsion systems. We review the concept and the theory of liquid laser propulsion. Then, we categorize the current state of research based on three types of propellants—non-energetic liquids, energetic liquids, and liquid metals—and provide an analysis of the propulsion characteristics arising from the laser ablation of liquids such as water, glycidyl azide polymer (GAP), hydroxylammonium nitrate (HAN), and ammonium dinitramide (ADN). We also discuss future research directions and challenges of pulsed liquid laser propulsion. Although experiments have yielded encouraging outcomes due to the distinctive properties of liquid propellants, continued investigation is essential to ensure that this technology performs reliably in actual aerospace applications. Consistent results under both spatial and ground conditions remain a key research content for fully realizing its potential.

The study of thruster plume flow fields can yield a series of thruster performance parameters such as thrust effect, spacecraft plume contamination, etc., which is of great significance for thruster development. The paper presents a physical simulation model of a laser thruster under a vacuum back-pressure environment. Through the finite difference method and the Direct Simulation Monte Carlo (DSMC) calculation method, based on the actual laser ablation thruster structure and working mode, the changes in the flow-field distribution in the laser thruster plume under different vacuum back-pressure conditions are obtained. The influence of different vacuum back-pressure conditions on the plume density, pressure, temperature, and velocity field of the thruster was verified through physical experiments, and the evolution of the plume flow field during the laser ablation of a polyamide glycidyl ether (GAP) solid target material was analyzed in detail. The simulation results are in good agreement with the test results, and the deviation between the simulated data and the test data from 0 to 3000 ns is less than 10.4%. This study presents a foundation for a prediction model of laser ablation thrusters under vacuum environments and provides an important reference for ground tests and in-orbit applications of satellite laser propulsion systems.

This study systematically investigates the dynamic evolution of chemical regimes in pulsed coaxial dielectric barrier discharge (DBD) plasma under atmospheric pressure using mass spectrometry. An innovative real-time mass spectrometric monitoring methodology was established, enabling the dynamic tracking of the formation and consumption processes of key reactive species such as ozone (O₃) and nitrogen oxides (NO_x). Energy density was the critical parameter governing the evolution of gaseous chemical components, with a quantitative elucidation of the regulatory mechanisms of air flow rate and control voltage on plasma chemical regime transition kinetics. Experimental results revealed significant parametric correlations: Under a constant control voltage of 140 V, increasing the gas flow rate from 0.5 to 5.5 L/min prolonged the transition duration from O₃-NO_x coexistence regime to a NO_x-dominant regime from 408 s to 1210 s. Conversely, at a fixed flow rate of 3.5 L/min, elevating the control voltage from 120 V to 140 V accelerated this transition, reducing the required time from 2367 s to 718 s. Parametric sensitivity analysis demonstrated that control voltage exerts approximately 3.3 times greater influence on transition kinetics than flow rate variation. Through comprehensive analysis of the formation and consumption mechanisms of N, O, O₃, and NO_x species, we established a complete plasma chemical reaction network. This scheme provides fundamental insights into reaction pathways while offering practical optimization strategies for DBD systems. For aerospace applications, this work holds particular significance by demonstrating that the identified control parameters can be directly applied to plasma-assisted treatment of propellant wastewater at launch sites, where the efficient removal of nitrogen-containing pollutants is crucial. These findings advance both the fundamental understanding of atmospheric-pressure plasma chemistry and the engineering applications of plasma-based environmental remediation technologies in aerospace operations.

This study proposes a novel calibration method for polyvinylidene fluoride (PVDF) piezoelectric sensors based on electromagnetic force. The standard force source is obtained by calibrating the original force source of the inductor coil through an electronic balance. Transient force loading waveforms and peak values of PVDF piezoelectric sensors were obtained to analyze the mechanical effects of laser ablation on Al/Ti alloys. Transient force sensing using PVDF piezoelectric sensors exhibits a wide linear detection range (0.01–5.8 V) and high response values in response to changes in electrical signals. When irradiating Al/Ti alloy targets with different laser energies and spot sizes, the electrical signal intensity of PVDF piezoelectric sensors varies greatly, and the corresponding transient force peak value test results range from 0.01 to 8.5 N. This excellent transient mechanical sensing performance can be attributed to the high laser power density, efficient laser energy utilization, and the physical properties of the target material. COMSOL Multiphysics simulation results confirmed that the temperature and ablation center position of the surface of the target material undergo significant changes after being irradiated with different laser energies and spots. The simulation results are consistent with the experimental results. This research indicates that transient force measurements based on PVDF piezoelectric sensors have broad prospects in high-performance optical laser propulsion applications.

Propellants play a crucial role in the propulsion systems of aerospace vehicles, and their combustion characteristics are susceptible to external environmental conditions. This study systematically investigated the impact of various initial conditions on the combustion process of ADN-based propellant, including combustion products, equilibrium pressure, adiabatic temperature, and ignition delay time. The results indicate that the primary combustion products of ADN-based propellant include N₂O, N₂, CO₂, OH, and others. ADN-based propellant exhibits a distinct two-stage combustion process under low pressure and temperature conditions (P₀ = 2 atm, T₀ = 586 K). Conversely, under high pressure and temperature conditions (P₀ = 10 atm, T₀ = 2930 K), the two stages of combustion occur almost simultaneously, making them difficult to distinguish. Furthermore, as the initial temperature increases, the ignition delay time decreases significantly, and the combustion rate accelerates. When the initial temperature rises from 400 K to 2800 K at a pressure of P₀ =10 atm, the ignition delay time decreases from 3.5 ms to 0.6 μs. Interestingly, changes in initial pressure have a relatively minor impact on the ignition delay time compared to changes in temperature. Therefore, temperature has a more crucial influence on the combustion characteristics of ADN-based propellant than pressure. This study holds promise for providing new combustion optimization strategies for the aerospace industry and promoting the development of aircraft designs towards higher performance and sustainability.

The vigorous development of micro–nano satellites urgently requires satellite-borne propulsion systems as support. Pulsed laser ablation micro-propulsion can meet these high demands. Ammonium dinitramide (ADN), as a green monopropellant, can serve as the working substance for laser ablation. This work investigated the micro-propulsion performance of liquid propellants composed of ADN and water with different ADN mass fractions, aiming to clarify the enhancement effect of chemical energy. Through the single-pulse impulse measurement, the results show that the 70 wt.% ADN had a maximum specific impulse of 167.55 s, a 19% increase compared to H₂O. The established semi-empirical model of the micro-propulsion performance fits well with the experimental data and can effectively explain the variations in the patterns of the propulsion’s parameters. The chemical energy’s actual rate of contribution to the increase in the kinetic energy was positively correlated with the ADN’s mass fraction and negatively correlated with the laser energy, with an actual contribution rate of 36% for 70 wt.% ADN at a laser energy of 60 mJ. Furthermore, based on the relationship between the ablation efficiency, chemical-specific energy, and laser specific energy, it was found that the ablation efficiency can be improved by increasing the chemical specific energy and reducing the laser specific energy while ensuring the breakdown. This work provides a scientific approach to quantitatively analyze the enhancement in the propulsion’s performance by chemical energy in laser micro-ablation, which is expected to be extended to other energetic liquid propellants.

The paper presents a simulation physical model of laser thruster under vacuum back pressure environment. Through the finite difference method and the Direct Simulation Monte Carlo (DSMC) calculation method, based on the actual laser thruster structure and working mode, the changes of the flow field distribution in the laser thruster plume under different vacuum back pressure conditions are obtained. The influence of different vacuum back pressure conditions on the plume density field and velocity field of the thruster was verified through physical experiments, and the evolution process of the plume flow field during laser ablation of polyamide glycidyl ether (GAP) solid target material was analyzed in detail. The simulation results are in good agreement with the test results, and the deviation between the simulated data and the test data from 0 to 3000ns is less than 10.4%. It presents a foundation for the prediction model of laser thruster under vacuum environment, and provides an important reference for ground test and in-orbit application of satellite laser propulsion system.

The present study explores the influence of diverse nozzle geometries on the combustion characteristics of ADN-based energetic propellants. The pressure contour maps reveal a rapid initial increase in the average pressure of ADN-based propellants across the three different nozzles. Subsequently, the pressure tapers off gradually as time elapses. Notably, during the crucial initial period of 0–5 μs, the straight nozzle exhibited the most significant pressure surge at 30.2%, substantially outperforming the divergent (6.67%) and combined nozzles (15.5%). The combustion product variation curves indicate that the contents of reactants ADN and CH₃OH underwent a steep decline, whereas the product N₂O displayed a biphasic behavior, initially rising and subsequently declining. In contrast, the CO₂ concentration remained on a steady ascent throughout the entire combustion process, which concluded within 10 μs. Our findings suggest that the straight nozzle facilitated the more expeditious generation of high-temperature and high-pressure combustion gases for ADN-based propellants, expediting reaction kinetics and enhancing combustion efficiency. This is attributed to the reduced intermittent interactions between the nozzle wall and shock waves, which are encountered in the divergent and combined nozzles. In conclusion, the superior combustion characteristics of ADN-based propellants in the straight nozzle, compared to the divergent and combined nozzles, underscore its potential in informing the design of advanced propulsion systems and guiding the development of innovative energetic propellants.

The precise determination of moment of inertia (MOI) holds paramount importance in investigating the rotational dynamics of an object. Based on the torsion pendulum system, a novel high-precision measurement method for MOI is developed by using the constant force in this paper. Firstly, the extreme response characteristics of a torsional pendulum measurement system under a constant force are discussed in detail in this paper, and the relationships between the system damping ratio, natural frequency, MOI and the extremal characteristic points of the system response are determined through the linear regression analysis. By applying the superposition principle, the MOI for the object being measured can be computed. As the performance of the constant force source is the key to ensure the measurement accuracy, this paper develops an electromagnetic force source, which consists of a coil and a permanent magnet, and the electromagnetic force variation law with the relative position of the coil and permanent magnet is investigated by utilizing a high-precision electronic balance, and then the optimal relative position is determined to reduce the impact of the relative position on the electromagnetic force. Furthermore, the high-precision electromagnetic force driving equation at the optimal position is acquired by utilizing the least square method. Finally, this paper develops a novel torsional measurement device for the MOI and successfully achieves high-precise measurement of the MOI for the target object using the proposed measurement method. The measurement experiment for MOI of a target object indicates that the corresponding measurement relative error is 0.297%, thereby confirming the effectiveness and high precision of the proposed measurement approach.