Search Results (427)

This study presents a simulation-based damage modeling and fatigue risk assessment of a reusable ceramic matrix composite thruster designed for short-duration, green bipropellant propulsion systems. The thruster is constructed from a fiber-reinforced ultra-high temperature ceramic matrix composite composed of zirconium diboride, silicon carbide, and carbon fibers. Time-resolved thermal and structural simulations are conducted on a validated thruster geometry to characterize the severity of early-stage thermal shock, stress buildup, and potential degradation pathways. Unlike traditional fatigue studies that rely on empirical fatigue constants or Paris-law-based crack-growth models, this work introduces a simulation-derived stress-margin envelope methodology that incorporates ±20% variability in temperature-dependent material strength, offering a physically grounded yet conservative risk estimate. From this, a normalized risk index is derived to evaluate the likelihood of damage initiation in critical regions over the 0–10 s firing window. The results indicate that the convergent throat region experiences a peak thermal gradient rate of approximately 380 K/s, with the normalized thermal shock index exceeding 43. Stress margins in this region collapse by 2.3 s, while margin loss in the flange curvature appears near 8 s. These findings are mapped into green, yellow, and red risk bands to classify operational safety zones. All the results assume no active cooling, representing conservative operating limits. If regenerative or ablative cooling is implemented, these margins would improve significantly. The framework established here enables a transparent, reproducible methodology for evaluating lifetime safety in ceramic propulsion nozzles and serves as a foundational tool for fatigue-resilient component design in green space engines. Full article

Reliable prediction of tunnel thruster performance under reverse, or off-design, reverse operating direction (ROD) conditions, is crucial for modern vessels that require bidirectional thrust from a single unit—such as yachts and offshore support vessels. Despite the increasing demand for such a capability, there remains limited understanding of the unsteady hydrodynamic behavior and performance implications of ROD operation. This study addresses this gap through a scale-resolving computational fluid dynamics (CFD) investigation of a full-scale, fixed-pitch propeller with a diameter of 0.62, installed in a tunnel geometry representative of yacht-class side thrusters. Using advanced turbulence modeling, we compare the thruster’s performance under both the normal operating direction (NOD) and ROD. The results reveal notable differences: in ROD, the upstream separation zone was more compact and elongated, average thrust increases by approximately 3–4%, and torque and pressure fluctuations rise by 15–30%. These findings demonstrate that a single tunnel thruster can meet bidirectional manoeuvring requirements. However, the significantly elevated unsteady loads during ROD operation offer a plausible explanation for the increased noise and vibration frequently observed in practice. Full article

To meet the rapid maneuverability and lightweight demands of micro-nano satellites, a space micro solid thruster using 3D-printed short glass fiber reinforced polyamide 6 (PA6GF) composites was developed. Thruster shells with wall thicknesses of 4, 3, and 2.5 mm were designed, and ground ignition tests were conducted to monitor chamber pressure and shell temperature. Compared with conventional metallic thrusters, PA6GF composites have exhibited excellent thermal insulation and sufficient mechanical strength. Under 8 MPa and 2773 K ignition conditions, the shell thickness was reduced to 2.5 mm and could withstand pressures up to 10.37 MPa. These results indicate that PA6GF composites are well-suited for space micro solid thrusters with inner diameters of 15–70 mm, offering new possibilities for lightweight space propulsion system design. Full article

As an innovative underwater propulsion technology, the rim-driven thruster (RDT) has garnered increasing attention due to its advantages over conventional diesel or gas turbine propulsion systems, including reduced noise, higher efficiency, and a compact structure. However, traditional hull–engine–propeller matching theories are not directly applicable to RDTs because of their unique shaftless and ducted characteristics. Based on conventional hull–engine–propeller matching theory and propeller design methodology, this study proposes a novel hull–engine–propeller matching approach tailored specifically to RDTs. The method enables rapid matching by using open-water characteristics for hull–engine–propeller matching. In the absence of open-water test data for shaftless propellers, key parameters derived from ducted propeller tests are used for matching based on open-water characteristics to design the shaftless propeller. The propeller is then optimized through computational fluid dynamics (CFD) simulations to achieve the required thrust performance, effectively enabling an equivalent replacement. The proposed method provides a practical framework for selecting and designing RDTs, improves overall propulsion efficiency, and offers specific guidelines for determining optimal motor design parameters. Full article

This study presents a comprehensive finite element investigation into the design optimization of an ultra-high temperature ceramic matrix composite thruster for green bipropellant systems. Focusing on ZrB₂–SiC–Cfiber composites, it explores their thermal and mechanical response under realistic transient combustion conditions. Two geometries, a simplified and a complex full-featured model, were evaluated to assess the impact of geometric fidelity on stress prediction. The complex thruster model (CTM) offered improved resolution of temperature gradients and stress concentrations, especially near flange and convergent regions, and was adopted for optimization. A parametric study with nine wall thickness profiles identified a 2 mm tapered configuration in both convergent and divergent sections that minimized mass while maintaining structural integrity. This optimized profile reduced peak thermal stress and overall mass without compromising safety margins. Transient thermal and strain analyses showed that thermal stress dominates initially (≤3 s), while thermal strain becomes critical later due to stiffness degradation. Damage risk was evaluated using temperature-dependent stress margins at four critical locations. Time-dependent failure maps revealed throat degradation for short burns and flange cracking for longer durations. All analyses were conducted under hot-fire conditions without cooling. The validated methodology supports durable, lightweight nozzle designs for future green propulsion missions. Full article

A collaborative inter-laboratory study was conducted to characterise the performance of the novel 250 W External Discharge Plasma Thruster (XPT) with a channel-less Hall effect-type thruster designed to address lifetime limitations and lower-power efficiency challenges in conventional Hall effect thrusters. This study aimed to validate performance measurements across different facilities and thrust stands, investigating potential facility effects on thrust characterisation. Performance testing was conducted both at the University of Surrey using a torsional thrust balance and at the University of Southampton with a double inverted pendulum thrust stand, providing independent verification of the thrust and efficiency metrics. The comparison highlighted the importance of cross-facility testing with differing background pressures, calibration methods, and thrust balance types. These differences provide valuable insights, ensuring more robust and reliable low-power thruster characterisation. The XPT thruster demonstrated consistent performance across both the University of Surrey and University of Southampton facilities, with thrust levels ranging from 1.60 mN to 11.8 mN, specific impulses from 327 s to 1067 s, and anode efficiencies up to 11%. Higher anode voltages and mass fluxes at Southampton enabled extended operational envelopes, revealing performance plateaus at elevated powers, particularly for flow rates above 8 sccm. Cross-facility testing highlighted facility-dependent influences, with Southampton achieving a higher thrust and specific impulse at lower flow rates (5–6 sccm) due to increased anode currents, while discrepancies between test sites of up to 25% were observed at higher flow rates (8–10 sccm) and powers above 200 W. Characterisation identified an optimal operating range at 200 W of anode power with a mass flux below 8 sccm. This work underscores the importance of inter-laboratory validation in electric propulsion testing and provides insights into the best practices for assessing next-generation Hall effect-type thrusters. Full article

Micronewton thrusters have a wide range of applications in the aerospace field, and the accuracy of micronewton thrust measurement is directly affected by environmental vibration. The cantilever beam is the core part of the microthrust measurement system, and its stability directly affects the accuracy of thrust calibration. Aiming at the problems of the cantilever beam oscillating during the change in thrust and being susceptible to the impulse vibration of the ground, the interference suppression scheme of the microthrust measurement system based on the fuzzy PID of particle swarm optimization is investigated. And an interference suppression algorithm of the microthrust system based on the adaptive Kalman displacement expectancy estimation algorithm and the fuzzy PID of particle swarm optimization is designed. An adaptive Kalman displacement expectation estimation algorithm and a particle swarm optimization fuzzy PID microthrust system interference suppression algorithm are designed. The results show that the proposed algorithm can effectively track the thrust signal and suppress the influence of external vibration interference for the mN-level thrust change, control the overshooting amount within 10%, shorten the stabilization time to within 0.2 s, reduce the impulse oscillation to 22% of the original, reduce the steady-state error, and have a strong suppression effect on the oscillation phenomenon of the system, with better control accuracy and stability, and provide a good condition for the thrust calibration. Full article

The fuel produced through water electrolysis is non-toxic and clean, and the water propulsion system offers low cost and easy integration with other systems. This study investigates the pulse operating characteristics of a water electrolytic chemical propulsion engine using microwave ignition technology. A high-speed camera captured flame images, while a spectrometer and pressure sensor were used for data quantification. Three peak gas pressure points were selected for data analysis. The experimental results revealed that the flame color changes at different combustion stages, starting white and turning blue at the flame tip during stable combustion. Combustion pressure fluctuated between −0.53 kPa and 765 kPa, with an average of ≈32 kPa, showing a rapid pressure rise followed by smooth decay. At all three operating points, the thrust was small (0.38 N, 0.37 N, and 0.35 N), but after the third operating point, thrust increased significantly to 2.25 N, an enhancement of 508.1%. Spectral data indicated that the combustion products included H, O, and N atoms. This study is the first to investigate the pulsed conditions of a direct microwave ignition system and provide insights into its operating characteristics. The system will be optimized in the future. Full article

Vacuum arc thrusters (VATs) have recently gained significant interest as a micro-propulsion system due to their scalability, low cost, storability, and small form factor. While VATs offer an attractive propulsion solution for CubeSats, conventional propellant feed systems used in VATs require intricate mechanical moving parts, increasing overall system complexity and mission risk. A promising alternative is the use of VAT arrays, where multiple thin-layer VATs are arranged in a regularly spaced grid, thus enhancing reliability, increasing total impulse without a mechanical propellant feed system, and enabling integrated attitude control via off-axis thruster placement. However, VAT arrays require a larger power processing unit (PPU) and additional control system, posing challenges within CubeSat volume constraints. To address this, this study proposes a novel PPU design that enables the simultaneous operation of multiple VATs while minimising system mass and volume. Experimental results demonstrate the successful operation of VAT pairs using the proposed PPU concept, validating its feasibility as an efficient propulsion solution for CubeSats. Full article

This research paper provides a conceptualization of a new type of plasma thruster based on screw-pinch physics and on the magnetic mirror concept. The article proposes a method to size a screw-pinch with a non-uniform axial magnetic field as a plasma thruster and to estimate its propulsive performance. The results obtained show that the plasma thruster is suitable for space missions inside the Earth’s sphere of influence and for space transportation of small satellites. Full article

In this study, an unsteady vortex element method is applied to the analysis of a horizontal wing in order to investigate its propulsive performance when operating as a biomimetic thruster. The foil undergoes a combined heaving and pitching motion at the same frequency, in a uniform inflow condition, due to its advance at a constant speed. The numerical results are presented and compared to experimental measurements for the propulsion thrust coefficient and the efficiency of the system over a range of motion parameters. The results indicate the significance of 3D effects and show that the present technique can serve for the design of this kind of propulsive system with optimized performance. In the next stage, the wing is examined in a horizontal T-foil arrangement at the bow of a ship as an efficient propulsion system, and its performance in irregular head waves, characterized by a frequency spectrum, is also studied using experiments in a towing tank. In the test cases, a 30% damping of the ship responses in waves is observed with a simultaneous decrease in the total resistance by 5%. The numerical results are compared with data obtained from tank experiments, revealing good agreement, demonstrating the applicability of the present method to the preliminary design of this system for the augmentation of ship propulsion in waves. Full article

The use of continuous-thrust propulsion systems allows spacecraft to cover complex space trajectories and to complete missions that would be difficult using chemical thrusters. Among the continuous-thrust propulsion systems proposed in recent decades, solar electric thrusters occupy an important position thanks to the maturity reached by this technology. Technological advances in the miniaturization of spacecraft components allow an electric thruster to be installed even in a small and standardized vehicle such as a CubeSat. In this context, the BIT-3 RF ion thruster is an interesting option that has been recently employed in some space missions for the study of the lunar surface. In the recent literature, the performance of a CubeSat equipped with a propulsion system based on the BIT-3 has been studied considering a simplified model in which the thrust magnitude has a fixed value or varies continuously within a prescribed range. However, the operating levels of a BIT-3 are finite in number. This paper studies the transfer performance of a BIT-3-propelled CubeSat considering the actual operating levels that can be provided by such a thruster. The work analyzes the optimal transfer towards asteroid 2000 SG344 when the electric power is obtained through solar arrays. Full article

Electric ducted fans are gaining prominence in aviation due to their compact size, low noise, and zero emissions compared to conventional gas turbines. This study presents an experimental test system for a 390 mm electric Ducted Propulsion Fan developed by the Aerospace Propulsion Systems group at Hanoi University of Science and Technology. The carbon fiber composite thruster, driven by a centrally located BLDC motor, was mounted on a test stand equipped with force and rotational speed (rpm) sensors. Power was supplied through two battery configurations, eight-pack and nine-pack, with voltage and current monitored and controlled via an ESC module. Experiments conducted from 2000 to 7000 rpm explored the relationship between electrical inputs and aero-propulsive outputs. The results revealed that input power, current, and sound pressure level (SPL) amplified meaningfully with rpm, while the voltage slightly declined. The maximum rpm reached 6500 rpm for the eight-pack and 7000 rpm for the nine-pack configurations. When greater than 6000 rpm, the SPL reaches close to 120 dB. The eight-pack configuration provided higher thrust per volt, whereas the nine-pack offered better thrust per ampere and improved starting power. Although dimensionless indices, including power coefficient (CP), thrust coefficient (CT), and figure of merit (FM), reduced with rpm, the FM remained between 0.7 and 0.75 at medium speeds, demonstrating effective energy conversion. Full article

As the demand for underwater robots in complex environments continues to grow, research on their agile motion capabilities becomes increasingly crucial. This paper focuses on the design and agile motion control of autonomous underwater vehicles (AUVs) operating in subsea environments, addressing key issues such as structural design, system modeling, and control algorithm development. An optimization model for the arrangement of propellers is formulated and solved using a Sequential Quadratic Programming (SQP) algorithm. Computational Fluid Dynamics (CFD) software is employed for hydrodynamic analysis and shape optimization. A novel adaptive event-triggered nonlinear model predictive control (AET-NMPC) algorithm is proposed and compared with traditional Cascaded Proportional–Integral–Derivative (PID) control and event-triggered cascaded PID control algorithms. Simulation and experimental results demonstrate that the AET-NMPC algorithm significantly enhances the response capability and control accuracy of underwater robots in complex tasks, with the trajectory tracking error being reduced to 4.89%. This study provides valuable insights into the design and control strategies for AUVs, paving the way for more sophisticated underwater operations in challenging environments. Full article

This paper presents a fault-tolerant thruster configuration scheme and a thrust control allocation strategy for an underwater vehicle. First, to accommodate the vehicle’s flexible spatial motion capabilities and address potential thruster failures, an 8-thruster vector arrangement is designed, and the impact of thruster failures on vehicle maneuverability is analyzed. Based on this configuration, a mathematical model of the vector propulsion system is then developed, establishing the relationship between the thrust generated by the individual thrusters and the virtual control forces applied to the vehicle’s 6 degrees of freedom (DOF). Subsequently, a thrust allocation strategy based on quadratic programming (QP) is proposed to optimize thrust allocation, enhancing energy efficiency while satisfying thrust saturation constraints. Finally, simulation results demonstrate that the proposed thruster configuration exhibits strong fault-tolerance. Moreover, compared to the least squares (LS) method based on the pseudo-inverse of the configuration matrix, the QP-based thrust allocation strategy achieves significantly better energy-saving performance. Full article