Small Thrust Research Articles

Electric Motor Chain Modeling Using Artificial Neural Networks and Semi-Empirical Methods

The methodology presented in this paper is dedicated to a user who wants to design a power chain of an electric unmanned aerial vehicle. The power chain includes a brushless direct current (BLDC) motor, a propeller, and a battery. Three models are presented to predict the thrust, electrical consumption, mechanical torque, and rotational speed provided by each component of an electrical power chain. Only public data were used to design these models. The research was developed in order to be used by all people who want to buy electrical power chain components and therefore to model their properties. Neural networks set with MATLAB parameters were used to design BLDC motor output (rotational speed and mechanical torque) models. Empirical methods such as blade element theory (BET) and disk area were used to model propeller thrust. A battery discharge model was designed based on public datasheets. Very good prediction results were obtained for the rotational speed (0.20% of error) and torque (0.45% of error). Small thrust modeling errors of 1.06% were found with the BET method. Models presented in this research could be designed using a wide type of data, such as public data (provided on manufacturer websites) or real test bench measurements.

Particle-in-Cell simulation of radio-frequency ion thruster RIT-1.0

Ion propulsion systems with a small thrust can be used in space missions for highly accurate controllability while possessing low power and propellant consumption. At the University of Giessen, radio-frequency ion thrusters are miniaturized with thrusts in the order of micro-Newtons (μ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mu$$\\end{document}N-RIT). As the size of the thruster becomes smaller the plasma properties can not be measured inside a closed plasma chamber. The simulations are needed to investigate plasma properties like temperature, density profile which would aid further opimization. In this work, we discuss kinetic simulations of plasma inside the RIT-1.0 thruster using in-house developed PlasmaPIC code that incorporates Monte-Carlo collisions (MCC) and Direct Simulation Monte Carlo (DSMC) for neutral gas distribution. We briefly present the features of PlasmaPIC and simulation of stable plasma generation. We also show the influence of neutral gas and extraction properties for the RIT-1.0 thruster under consideration.

Design and simulation of an automatic tank pressurization system for ground test of small thrust LREs

Design and simulation of an automatic tank pressurization system for ground test of small thrust LREs

Autonomous nanorobots with powerful thrust under dry solid-contact conditions by photothermal shock

Nanorobotic motion on solid substrates is greatly hindered by strong nanofriction, and powerful nanomotors‒the core components for nanorobotic motion‒are still lacking. Optical actuation addresses power and motion control issues simultaneously, while conventional technologies with small thrust usually apply to fluid environments. Here, we demonstrate micronewton-thrust nanomotors that enable the autonomous nanorobots working like conventional robots with precise motion control on dry surfaces by a photothermal-shock technique. We build a pulsed laser-based actuation and trapping platform, termed photothermal-shock tweezers, for general motion control of metallic nanomaterials and assembled nanorobots with nanoscale precision. The thrust-to-weight ratios up to 107 enable nanomotors output forces to interact with external micro/nano-objects. Leveraging machine vision and deep learning technologies, we assemble the nanomotors into autonomous nanorobots with complex structures, and demonstrate multi-degree-of-freedom motion and sophisticated functions. Our photothermal shock-actuation concept fundamentally addresses the nanotribology challenges and expands the nanorobotic horizon from fluids to dry solid surfaces.

A novel Penta-jet VTOL aerial robot: Modeling, control, and simulation verification

This paper presents a novel unmanned aerial vehicle known as the “Penta-jet”, which uses mini turbojet engines as its power source. The Penta-jet offers superior power compared to small rotorcraft and demonstrates enhanced maneuverability during takeoff and landing in comparison to fixed-wing aircraft. The Penta-jet uses four small thrust turbojet engines to supply steering power and a large thrust turbojet engine to provide the main thrust. To analyze the motion characteristics of the Penta-jet, a mathematical model is proposed, focusing on the dynamic analysis of the aircraft’s power system and rotation vector system. To achieve fixed-point reach and trajectory-tracking tasks, a back-stepping control technology with integral terms is designed for the attitude subsystem (inner loop) and position subsystem (outer loop). Simulation results demonstrate the proposed control method has a shorter adjustment time and smaller overshoot compared with the traditional control method, especially in tracking spiral trajectories.

Generalized analytical body force model for actuator disc computations of wind turbines

Abstract. A new generalized analytical model for representing body forces in numerical actuator disc models of wind turbines is proposed and compared to results from a blade element momentum (BEM) model. The model is an extension of a previously developed load model, which was based on the rotor disc being subject to a constant circulation, modified for tip and root effects, corresponding to an optimum design case. By adding a parabolic circulation distribution, corresponding to a solid-body approach of the flow in the near wake, it is possible to take into account losses associated with off-design cases, corresponding to pitch regulation at high wind speeds. The advantage of the model is that it does not depend on any detailed knowledge concerning the actual wind turbine being analysed but only requires information about the thrust coefficient and tip-speed ratio. The model is validated for different wind turbines operating under a wide range of operating conditions. The comparisons show generally an excellent agreement with the BEM model even at very small thrust coefficients and tip-speed ratios.

Numerical study on the dynamic process of ramjet/scramjet mode transition in the integrated full flow path for RBCC engine

As the inflow velocity increases, rocket-based combined cycle(RBCC) engine typically require a ramjet/scramjet mode transition within the flight range Ma∞ = 5.5 to 6.0. However, during the mode transition process, the reduction of the fuel mass flow rate usually causes the combustion intensity in the engine to drop sharply in a very short time, which will further lead to severe thrust fluctuations. So some technical methods need to be applied in this process to realize smooth mode transition. In this paper, different throttling strategies (kerosene mass flow rate dominant and rocket mass flow rate dominant) were designed and employed to study the dynamic mode transition process in the integrated RBCC engine flow path through three-dimensional numerical simulation for flight Ma∞ = 5.5 and Ma∞ = 6.0, respectively. The results show that when RBCC engine operates under the condition of large mass flow rate of fuel, the wall flow separation zone caused by oblique shock wave and combustion cannot be effectively improved by the bleed block and the inlet is still in the limit working state. Under flight Ma∞ = 5.5 condition, with the reduction of fuel equivalence ratio, RBCC engine successfully transited from ramjet mode to scramjet mode, and the flow separation zone near the bleed block disappeared. At this time, the high temperature gas of the rocket has no obvious effect on the thrust gain of the engine. By adjusting fuel mass flow rate in a small range and rocket mass flow rate in a large range, stable mode transition can be achieved, with relatively small time consumption and minimum thrust fluctuation during mode transition. With the increase of flight altitude, under flight Ma∞ = 6.0, the incoming flow speed increases, but the air capture ability of the inlet decreases, which is not conducive to the mixing of fuel and air combustion. When Ma∞ = 5.5, the mode transition by reducing the fuel equivalence ratio will cause the RBCC engine to produce huge thrust fluctuations, and the range of the high-pressure zone in the combustor will be greatly reduced. In order to ensure the stable operation of the RBCC engine, the rocket needs to operate at a larger mass flow rate.

A three-dimensional numerical study on the effect of geometric asymmetry on arcjet thruster performance

In an arcjet thruster, the cathode and constrictor degrade with time, and the electrical arc discharge may become unsymmetrical. In this work, a three-dimensional numerical model of a hydrogen plasma arcjet is developed and validated to study the effect of unsymmetrical electric arc discharge on thruster performance. The unsymmetrical arc discharge is realized by introducing a radial shift of the cathode so that the cathode tip offset is 80 μm (25% of the constrictor radius). Simulations are conducted for both axially centered cathode (coaxial) and off-centered cathode (non-coaxial) configurations with identical propellant flow rates and input current. Simulations show asymmetrical arc discharge in the non-coaxial cathode configuration, resulting in azimuthally asymmetric Joule heating, species concentrations, and velocity field. This asymmetry continues as the plasma expands in the divergent section of the nozzle. Temperature, species concentrations, and axial velocity exhibit asymmetric radial distribution at the nozzle exit. The computed Joule heating was found to reduce with cathode shift, and consequently, the thrust and specific impulse of the thruster was decreased by about 6.6%. In the case of the non-coaxial cathode, geometric asymmetry also induces a small side thrust.

Timing and Origin of Compressional Tectonism in Mare Tranquillitatis

AbstractThe lithosphere of the Moon has been deformed by tectonic processes for at least 4 billion years, resulting in a variety of tectonic surface features. Extensional large lunar graben formed during an early phase of net thermal expansion before 3.6 Ga. With the emplacement of mare basalts at ∼3.9–4.0 Ga, faulting and folding of the mare basalts initiated, and wrinkle ridges formed. Lunar wrinkle ridges exclusively occur within the lunar Maria and are thought to be the result of superisostatic loading by dense mare basalts. Since 3.6 Ga, the Moon is in a thermal state of net contraction, which led to the global formation of small lobate thrust faults called lobate scarps. Hence, lunar tectonism recorded changes in the global and regional stress fields and is therefore an important archive for the thermal evolution of the Moon. Here, we mapped tectonic features in the non‐mascon basin Mare Tranquillitatis and classified these features according to their respective erosional states. This classification aims to provide new insights into the timing of lunar tectonism and the associated stress fields. We found a wide time range of tectonic activity, ranging from ancient to recent (3.8 Ga to <50 Ma). Early wrinkle ridge formation seems to be closely related to subsidence and flexure. For the recent and ongoing growth of wrinkle ridges and lobate scarps, global contraction with a combination of recession stresses and diurnal tidal stresses, as well as with a combination of South Pole‐Aitken ejecta loading and true polar wander are likely.

Numerical study of a trapezoidal bypass dual throat nozzle

Bypass Dual Throat Nozzle (BDTN) is a novel type of fluidic thrust vectoring nozzle. To improve the infrared stealth performance of BDTN, a nozzle based on BDTN is proposed and numerically simulated. Each cross-section along the x-axis of the novel nozzle becomes a trapezoid, which is named “BDTN-TRA.” The main numerical simulation results show that BDTN-TRA can produce a thrust vectoring angle when the upper or lower bypass valve is open. The angle difference between the two conditions mentioned above is usually approximately 1°–2°. Even if the two bypasses are closed, BDTN-TRA can produce a small thrust vectoring angle at around 3°–5°. When the sidewall angle increases from 60° to 90°, the thrust coefficient and thrust vectoring angle under each work condition usually decrease. A larger aspect ratio indicates better performance. As the aspect ratio increases over 7.2, the performance of BDTN-TRA is quite close to that of BDTN with rectangular cross-sections at the same aspect ratio. These features will benefit the control and trimming for future aircraft design, especially for the flying wing layout aircraft. Last but not least, BDTN-TRA has a more extraordinary mixing performance compared with BDTN. The distributions of static temperature and axial velocity along the x-axis of BDTN-TRA with sidewall angle of 60° decrease faster than those of BDTN. When the total temperature of the inlet equals 1600 K, the static temperature difference between BDTN-TRA with sidewall angles of 60° and 90° is over 360 K at twice the length of the nozzle downstream of the nozzle exit, which is the reflection for excellent infrared stealth for the fighter.

Research on shipping energy-saving technology: Hydrofoil amphibious vehicle driven by waterjet propulsion

The shipping industry is one of the crucial sources of carbon emissions. With carrying capacity both on land and water, the hydrodynamic characteristics of amphibious vehicles are essential indicators of energy saving and emission reduction. The hydrodynamic characteristics of an amphibious vehicle driven by a single waterjet propulsion are investigated in this study, together with the impact of the NACA0012 hydrofoil mounted at the bow and stern. Based on the RANS and body force methods, the hydrodynamic calculation models of the bare hull and waterjet-driven hull are established. All CFD calculations are based on STAR-CCM+. Based on the towing experiment, an uncertainty analysis is conducted to confirm the precision and legitimacy of the numerical calculation approach. The thrust deduction characteristics of vehicle hulls with different hydrofoil models are analyzed respectively. Small or negative thrust deductions always occur at medium and high speeds. Combined with the analysis of vehicle attitude, flow field, and pressure distribution, the inherent thrust deduction characteristics of the amphibious vehicle and the influence of hydrofoils are studied. Then, the hydrodynamic characteristics of different configurations are compared. The lift characteristics of hydrofoils and their influence on the vehicle's attitude and resistance are studied. The change in the performance of the stern hydrofoil caused by the waterjet propulsion is analyzed. Results show that the hull with two hydrofoils has the best drag-reduction effect when Fr<1.43, and the highest drag-reduction rate is 25.7%.

고체/액체 혼합 입자 분사에 의한 항공기 노즐의 다상 유동에 관한 전산 해석

Infrared (IR) signals from the hot exhaust gases of aircraft engines have a significant impact on the survivability of aircraft. Several methods were developed to reduce IR signatures to avoid tracking by IR signatures generated in the exhaust, or decoy flares are used to deceive IR seekers. Research into injecting water particles to lower the exhaust gas temperature or injecting carbon particles to shield the plume has also been previously conducted. In this study, we propose a method for injecting solid/liquid mixed particles that lower the exhaust gas temperature and block IR signal propagation generated in the exhaust gas. The multiphase flow in aircraft nozzles by solid/liquid mixed particle injection was analyzed using the CFD code for the total flow rate of particles corresponding to 5%, 10%, and 20% of the exhaust gas flow rate. After analyzing the characteristics of the mixed particles interacting with the exhaust plume, the optimal flow rate of water and carbon particles with a small thrust penalty was obtained.

The time has come to stop using the audible pop caused by thrust manipulation as a criterion of success

High velocity, small amplitude thrust manipulation has been shown to beneficial and is indicated to reduce pain, improve joint mobility, and reduce disability. Thrust manipulation of the spine often results in a popping sensation. The exact mechanism responsible for the audible pop remains elusive. Current clinical guidelines indicate that clinicians should use research evidence to guide clinical decision making. The effects and/or benefit of the audible pop during spinal manipulation has been the subject(s) of several previous studies. Such studies evaluated and failed to demonstrate any direct effect of an audible pop’s presence on the subjective reported pain levels, improvement in joint mobility, a change in nervous system activity, and a change in patient perceived disability. Based on current evidence, it seems abundantly clear that the audible pop cannot be used as a criterion (by clinicians and researchers) to determine if the spinal thrust manipulation was successful. Despite the current evidence, the research community continues to ignore this and uses the audible pop as a standard for the success of a spinal thrust manipulation. Additionally, the thrust manipulation will be repeated a second time if no audible pop is obtained or switching to the opposite spinal segment and attempted twice to achieve the audible pop. This potentially results into multiple capsular stretch maneuvers and makes comparison post intervention unreliable. The audible pop is not correlated to therapeutical success; stop using it for that.

A New Strategy for Disc Cutter Wear Status Perception Using Vibration Detection and Machine Learning.

Carrying out status monitoring and fault-diagnosis research on cutter-wear status is of great significance for real-time understanding of the health status of Tunnel Boring Machine (TBM) equipment and reducing downtime losses. In this work, we proposed a new method to diagnose the abnormal wear state of the disc cutter by using brain-like artificial intelligence to process and analyze the vibration signal in the dynamic contact between the disc cutter and the rock. This method is mainly aimed at realizing the diagnosis and identification of the abnormal wear state of the cutter, and is not aimed at the accurate measurement of the wear amount. The author believes that when the TBM is operating at full power, the cutting forces are very high and the rock is successively broken, resulting in a complex circumstance, which is inconvenient to vibration signal acquisition and transmission. If only a small thrust is applied, to make the cutters just contact with the rock (less penetration), then the cutters will run more smoothly and suffer less environmental interference, which would be beneficial to apply the method proposed in this paper to detect the state of the cutters. A specific example was to use the frequency-domain characteristics of the periodic vibration waveform during the contact between the cutter and the granite to identify the wear status (including normal wear state, wear failure state, angled wear failure state) of the disc cutter through the artificial neural network, and the diagnosis accuracy rate is 90%.

Optimum design of nuclear electric propulsion spacecraft for deep space exploration

Future space exploration is now focused on new field-deep space planets. Deep space exploration and the development and utilization of resources are inestimable strategic significance for the country to seize the initiative and command heights of deep space exploration. Nuclear electric propulsion (NEP) systems convert heat from the fission reactor to electrical power and then use the electrical power to produce thrust. Compared with traditional propulsion technology, the NEP system with variable Isp can be used for several applications. The NEP spacecraft is more suitable for deep space exploration missions due to the advantages of high specific impulse, high power, and long life. This paper analyzes the relationship between the transfer travel time, specific mass, power, and payload ratio of the NEP spacecraft through simple performance models. Use the mass optimization and specific mass optimization models based on the NEP system composition and small thrust orbit theory to maximize the payload ratio for a given transfer time and technological characteristics. Finally, applied this NEP model to discuss the feasibility of Mars, Jupiter, and Saturn transfer missions and compared it with the Tianwen-1, Juno, and Cassini–Huygens spacecraft, respectively. Results show that when the NEP spacecraft specific mass reaches 4.77 kg/kW, the Earth–Mars transfer time can be changed to 331.31 days, the payload increases to 1650 kg, the transfer time for Jupiter and Saturn mission would be shorted to 661.31 days and 1131.31 days, the corresponding payload significantly increases which achieved to 1270 kg and 2981 kg. The nuclear electric propulsion spacecraft dramatically improves the detection capability of the spacecraft and provides a reference for the feasibility demonstration and subsequent design of the deep space and the extrasolar planet exploration.

Analogue sandbox modeling of orogenic wedge front faulting: Roles of inherited fault zones and topographic loading

Earthquakes reported in the frontal belts of active orogenic wedges such as the 2013 Mw6.6 Lushan and 1999 Mw7.6 Chi-Chi earthquakes, highlight the importance of loading exerted by mountainous topography and inherited fault zones. However, their effects on formation and activation of these wedge front fault systems remain poorly understood. This study presents three sets of sandbox experiments in which topographic loading and geometry of inherited faults were first separately investigated, then explored jointly. Experiments show that smaller topographic loading favors gentle-dipping wedge front thrusts, while larger topographic loading promotes the development of steep wedge front faults. Introduced as zones of frictional weakness, all inherited faults promote deformation localization, though the steep ones are characterized by buttressing nearby rather than direct slip on themselves. When the two factors were tested integrally, four major deformation modes arose, including (1) direct reactivation; (2) fault truncation in the initial stage of compression; (3) stacking of small thrusts against the inherited fault and possible truncation in a later evolutionary stage; (4) behavior as a fossil structure. These modes show differences not only in first-order deformation styles, but also in the distribution of secondary structures, defining a basic framework and providing new guides for the interpretation of complex wedge front fault systems and their activities, in areas such as the Longmen Shan (eastern Tibet), the Tian Shan and the western margin of the Taiwan orogen.

Development, Verification, and Analysis of a Small Satellite Thrust Determination Filter

A current challenge for the Advanced Propulsion Experiment (APEX) CubeSat, under development by Missouri University of Science and Technology, is the accurate determination of thrust for its experimental multimodal propulsion system main payload. A consider batch least-squares filter is proposed that processes downlinked dual-frequency GPS pseudorange data to estimate the average thrust magnitude of a maneuver in conjunction with the initial dynamic states, static coefficients of drag and solar radiation pressure, and GPS receiver clock biases from each measurement epoch. Two Monte Carlo analyses were performed to test the statistical consistency of the filter and the robustness under the influence of unmodeled dynamics. The filter was found to perform nominally with matching truth and filter dynamics models and acceptably when the truth model used to synthesize measurements was a higher fidelity than the filter model. Filter performance was assessed using flight data from NASA’s Gravity Recovery and Climate Experiment Follow-On mission. A trade study was conducted to identify acceptable orbital regimes for the APEX mission. Thrust estimates using this method were shown to meet APEX mission requirements for a range of acceptable orbits.

Laboratory Model Test of Fully Buried Portal Frame-Shaped Slope-Stabilizing Piles

Abstract Fully buried portal frame-shaped piles have been widely used to control and stabilize large-scale landslides or slopes. However, the working mechanism of portal frame piles, such as the soil–pile interaction and load transfer behavior, is still not fully understood, which has limited the development of effective pile designs and construction. In this study, a well-designed laboratory model test was conducted in a sandy soil slope with a man-made slip surface. Nine portal frame piles were installed, synthetically considering the pile spacing between the rear and front piles as well as the support condition of the pile ends. To make the test closer to reality, in addition to a small thrust due to the excavation of the slope, greater landslide thrusts were imposed on the rear side of the portal frame piles by gradually applying static loads on the top of the slope. It is found that in addition to a concentrated thrust transferred via the cap beam, a landslide thrust accounting for 30 to 60 % of the landslide thrust on the rear pile was transmitted to the front pile by the soil sandwiched between the rear and front piles, which should not be ignored in designs. Meanwhile, to evenly mobilize the bearing capacity of both the rear and front piles, the reasonable spacing between them should be 1.0 to 1.5 times the diameter of the pile. The study also shows that portal frame piles should be embedded in a stable soil layer rather than the bedrock if they can meet the requirements for bearing capacity.

Optimal Design of a Short Primary Double-Sided Linear Induction Motor for Urban Rail Transit

Linear induction motors (LIMs) have been widely used in rail transit. However, Due to the breaking of the primary core and the large air gap, the efficiency and power factor of LIMs are seriously damaged, causing a large amount of energy waste. To improve the efficiency and power factor of LIMs for urban rail transit, we present a new optimization method for the design of a short primary double-sided linear induction motor (SP-DLIM) with a rated speed of 45 km/h and small thrust. The method is based on a steady state equivalent circuit model and the differential evolutionary algorithm (DEA). Moreover, the design constraints and the objective functions are proposed for the optimization problem. Finally, the optimized SP-DLIM is simulated by 2D transient finite element method (FEM). The 2-D transient FEM results verify the accuracy of the optimization method proposed in this paper.

Variation of Osculating Orbit Elements Using Low-Thrust Photonic Laser Propulsion in the Two-Body Problem

This study investigated the variation of the osculating orbit elements of a spacecraft propelled by photonic laser propulsion (PLP) under the two-body problem assumption. The PLP thrusting system can produce continuous and constant thrust. This paper first reviewed its basics and then studied its influences on the variation of osculating orbit elements given a small PLP thrust. Gauss’s equations, perturbation theory, and normalization were introduced to investigate this problem. Our work approached the problem by studying the influences of small planar and out-of-plane PLP thrusts, respectively. Bounds on the variation of orbit elements were derived, and a sufficient condition that traps the mission spacecraft in the vicinity of the mother ship was also found. Numerical simulations are also presented to verify our results, including the bounds and the sufficient conditions. The results obtained in this paper are directly applicable to the usage of PLP thrust, a new type of thrusting system, in the future, and are potentially helpful to various space missions, especially interplanetary travel.