Journal of Aerospace Engineering

This paper focuses on the guidance of an unpowered reusable launch vehicle (RLV) with aerosurface failure in the terminal area energy management (TAEM) phase. The aerosurface failure will limit the bank capability, and has a great influence on the range and turning radius of RLV. To this end, a new TAEM guidance scheme with the ability of online profile reconstruction is proposed in this paper for the bank-constrained RLV. The 3-dimensional (3D) profile is reconstructed online by directly adjusting the parameters of the dynamic pressure profile and the two-external-tangent-circle-based ground track profile. As the coupling between vertical and lateral motion is considered in the trajectory propagation, the reconstruction accuracy is guaranteed. Then, a closed-loop TAEM guidance law is proposed to track the reconstructed 3D profile. The effectiveness and robustness of the guidance scheme are verified by numerical simulations with a variety of initial states and model deviations.

Controllable lunar landers with magnetorheological fluid (MRF) damper have become a hot topic of research. However, limited research studies have been performed on the damping force analysis of MRF under high-velocity impacts. In this paper, the MRF hydrodynamics of new landing gear is analyzed under both steady and transient states by both theoretical analysis and simulations. To investigate the landing gear, its coupled Eulerian-Lagrangian (CEL) simulation model was constructed and analyzed in Abaqus. The study compares the simulated damping forces with those of theories. Under low uniform velocities, the simulated damping forces are in good agreement with those of the theories. Under high-velocity impacts, the simulated damping forces are more complex. To get lighter landing gear with better landing performance, an optimized lander was designed using the response surface methodology (RSM). In the optimized model, the mass of the optimized primary strut was reduced by 16.07% with a reduction in the fluctuations of the damping forces. It will be easier to control the landing under smoother damping forces, which is necessary for a successful landing.

With a view to designing tests in the arc wind tunnel small planetary entry simulator (SPES) at the Department of Industrial Engineering of the University of Naples “Federico II” on specimens of ultra-high-temperature ceramic (UHTC) materials, computer simulations have been carried out in order to get information about the test conditions, i.e., electrical power supplied to the torch, the nozzle area ratio (exit area/throat area), and the specimen geometry, to avoid expensive and time-consuming experimental characterization. Computations have been carried out both by a computation fluid-dynamics (CFD) and a direct simulation Monte Carlo (DSMC) code. The computations provided important quantitative information about flow field for velocity, temperature, gas composition, etc., and about heat flux and pressure on the specimen. The present computations allowed the authors to define the capabilities of SPES to perform tests on UHTC specimens, identifying a range of potential applications. Computed values of heat flux have been also compared with preliminary measurements performed by means of a copper slug calorimeter. Because of the evident effect of surface catalytic level on the experimental measurements, an experimental/computational procedure has been used to estimate the recombination efficiencies of oxygen and nitrogen on the calorimeter surface. The definition of this procedure is aimed at a future evaluation of surface catalyticity of UHTC specimens. At the conditions tested in the present paper, the procedure indicates that oxygen catalytic effect is higher than that of nitrogen, which is in agreement with what is reported in the literature.

This study investigates the effects of inhomogeneous wind fields on the aerostatic stability of a long-span cable-stayed bridge, which straddles a typical mountain-gorge terrain. Inhomogeneous wind fields, with featured wind speeds and wind attack angles, along the bridge’s main beam were firstly analyzed by using the computational fluid dynamics (CFD) approach. Then, a nonlinear methodology was implemented by adopting the ANSYS parametric design language (APDL) technology to analyze the aerostatic stability of long-span bridge under inhomogeneous wind speeds and inhomogeneous wind attack angles. The effects of inhomogeneous wind attack angles, inhomogeneous wind speeds, and both inhomogeneous wind speeds and inhomogeneous wind attack angles on the bridge’s aerostatic stability were comprehensively investigated. The aerostatic deformation of the bridge’s main beam and the variation of the cable’s axial force were also analyzed. The results show that the critical wind speed of the aerostatic instability under inhomogeneous wind attack angles is much smaller than that under homogeneous ones, and the performance of the aerostatic stability under inhomogeneous wind attack angles mainly depends on the peak wind attack angle rather than the average value of those inhomogeneous wind attack angles along the main beam. The wind-load effects acting on the main beam under inhomogeneous wind speeds are larger than those under homogeneous ones, and the critical wind speed of the aerostatic instability under inhomogeneous wind speeds is mainly determined by both the average and peak wind speeds along the main beam. The shapes of vertical displacements and torsion angles along the main beam are mainly dominated by the wind attack angles. However, the lateral displacements along the main beam are relatively independent, where the shapes are generally symmetrical to the midspan line and the values are mainly dominated by the oncoming wind speeds.

Studies suggest that hybrid-electric aircraft have the potential to generate fewer emissions and be inherently quieter when compared to conventional aircraft. By operating combustion engines together with an electric propulsion system, synergistic benefits can be obtained. However, the performance of hybrid-electric aircraft is still constrained by a battery’s energy density and discharge rate. In this paper, the influence of battery performance on the gross mass for a four-seat general aviation aircraft with a hybrid-electric propulsion system is analyzed. For this design study, a high-level approach is chosen, using an innovative initial sizing methodology to determine the minimum required aircraft mass for a specific set of requirements and constraints. Only the peak-load shaving operational strategy is analyzed. Both parallel- and serial-hybrid propulsion configurations are considered for two different missions. The specific energy of the battery pack is varied from 200 to $\mathrm{1,000}\mathrm{W}·\mathrm{h}/\mathrm{kg}$, while the discharge time, and thus the normalized discharge rating (C-rating), is varied between 30 min (2C discharge rate) and 2 min (30C discharge rate). With the peak-load shaving operating strategy, it is desirable for hybrid-electric aircraft to use a light, low capacity battery system to boost performance. For this case, the battery’s specific power rating proved to be of much higher importance than for full electric designs, which have high capacity batteries. Discharge ratings of 20C allow a significant take-off mass reduction aircraft. The design point moves to higher wing loadings and higher levels of hybridization if batteries with advanced technology are used.

This work evaluated the effect of the unique microstructures and defects on the dynamic mechanical behavior of laser metal–deposited (LMD) GH4169. The compression and shear properties were tested at strain rates ranging from 0.001 to $\sim \mathrm{30,000}/\mathrm{s}$. The difference in dynamic properties between the LMD and forged GH4169 was estimated by a comparative study of their dynamic compressive response at different temperatures. The initial microstructures and fractured characteristics were observed using a scanning electron microscope. The results showed that both the compressive and shear strength exhibit significant strain-rate sensitivity. The microstructural anisotropy leads to different compressive strengths depending on loading direction. However, the anisotropy of shear properties is not obvious, resulting from the narrow deformation area of shear specimen. Owing to the coarse columnar grains in the LMD GH4169 sample, the compressive strength of the LMD sample was lower than that of the forged sample. The crack and fractography morphology showed that Laves phases and defects in the LMD samples could be sensitive points for deformation and fracture under dynamic loading.

The wing leading edge is susceptible to birdstrike, so various antibirdstrike schemes are proposed to ensure that the wing leading edge satisfies the requirements of airworthiness regulations. This paper proposes a novel antibirdstrike design, referred to as localized strengthened variable-thickness skin (LSVTS). An experimentally validated numerical model is used to prove the effectiveness of the novel design against birdstrike. The proposed scheme is compared with three other antibirdstrike schemes. The simulation results indicate that the new scheme can protect the wing skin from bird penetration and minimize the weight increase. Meanwhile, the compression residual strength of LSVTS increases by 20.9%–82.03% compared with those of the other three schemes. The novel antibirdstrike design is also suitable for most aircraft wings.

A nonlinear generalized minimum variance (NGMV) optimal controller is presented in this paper, which achieves tracking control of an Osprey fixed-wing aircraft with parameter uncertainties and unmodeled nonlinear disturbances. The optimal strategy involves minimizing a signal that includes the sum of the weighted tracking error and the weighted control effort. The input subsystem utilized in the dynamic model is very general and nonlinear. The reference model is represented as a linear subsystem, and the states are estimated using a modified linear Kalman filter. A benefit of the proposed NGMV optimal controller is that it is designed to be easily implementable and computationally minimal, requiring no online optimization. Finally, simulations of tracking control for an Osprey fixed-wing aircraft are provided and the performance of the proposed NGMV control law is compared with a proportional–integral–derivative (PID) controller.

An electrostatic precipitator that is suitable for use in the Martian atmosphere has been investigated to remove dust from carbon dioxide gas. It is expected to be used as an in situ resource in the production of oxygen on Mars. This technology has several advantages, including a low drop in pressure, simple configuration, low power consumption, long life, and no required consumables. A prototype with a wire-to-parallel-plate electrode was constructed to investigate the fundamental characteristics of the system in a past study. A preliminary experiment revealed that the performance at low pressure (700 Pa), which simulates the Martian environment, was different from that at atmospheric pressure (101 kPa). The cleaning efficiency was a maximum of 75% at 700 Pa, while it was nearly 100% at 101 kPa. A modified precipitator consisting of multiwire and parallel-plate electrodes was constructed in this study to improve the system performance. The cleaning efficiency improved to approximately 95% after adopting a two-wire configuration with a low applied voltage and no corona discharge in low-pressure (700 Pa) carbon dioxide gas. Dust collected on the surfaces of the wire electrodes, unlike the case when the pressure was 101 kPa (1 atm). It was demonstrated that the deposited dust could be removed by applying mechanical vibration to the wires for a short period, which facilitates long-time operation.

The feasibility of integrating the wave propagation (WP) method with the electromechanical impedance (EMI) method in damage diagnosis of joints in precast concrete segments under shear load was experimentally studied. The variation of voltage signals, relative voltage attenuation coefficient (RVAC), resistance curves, and RMS deviation (RMSD) index was discussed to investigate the time and location of fracture occurrence. The male–female single-key joint specimens were match cast and connected with epoxy resin adhesive. Voltage signals and resistance of piezoelectric lead zirconate titanate (PZT) transducers were measured at the healthy state and every load interval. The RVAC and RMSD value were presented as quantitative assessments of the damage. The results indicated that as the load increased, the peak value of the voltage signals and resistance curves decreased. The downward shift of the voltage wave and the relative change of the RVAC proved that shear damage occurred at the upper and middle parts of the epoxied single-key joint. Furthermore, the variation of the resistance curves and the RMSD value determined the location and quantitatively assessed the extent of the damage. Data analyzed from the test demonstrated the effectiveness of integrating the WP method with the EMI method in damage detection of single-key joints.

Biaxial buckling of the laminated composite rhombic (skew) plate with mass variations in the form of openings and adding extra mass at the center of the plate was studied using improved shear deformation theory (ISDT). The ISDT mathematical model incorporates third-degree variation of the thickness coordinate in the displacement formulation. In the presented theory, the use of shear correction factor was eliminated and a second-order variation of transverse shear strains through the plate thickness was implied. A computer-based algorithm based on the $C_0$ finite-element formulation of the mathematical model was developed to analyze the buckling behavior of a laminated composite skew plate with openings and extra mass imposed at the center of the plate. Due to a lack of results in the literature based on the ISDT of the considered problem of biaxial buckling of laminated composite skew plates with openings cutout and extra mass imposed at the center of plate, the present results were validated with the suitable results available for laminated composite plates without openings/extra mass imposed at the center of plate with zero skew angle. The new results were obtained by varying the geometry, boundary conditions, ply orientations, and skew angles.

In situ resource utilization on the Moon increases mission capability in lunar exploration and colonization. Lunar regolith is the most promising substance that can be used as a building material; its chemical composition includes metals, oxygen, helium-3, and water. Because the transportation of regolith is an essential and intricate part of its utilization, the author investigates a vibration transport system that uses a piezoelectric actuator combined with a displacement-amplifying mechanism. Although the load capacity of the piezoelectric actuator is substantially high, its movable displacement is low. Therefore, the displacement of the piezoelectric actuator was amplified approximately five times in the direction normal to the extending direction of the piezoelectric actuator to generate a high magnitude of vibration. A vibrational acceleration of approximately 7 g of the conveyor was achieved by optimizing the structure of the displacement-amplifying mechanism. The system has no frictional parts and does not require complicated controls or a significant amount of power; thus, it is compatible with space applications. We demonstrated both a flat and an inclined transport path through a small conveyor tube with a 26-mm inner diameter and 300-mm length. The results indicated a mass flow rate of approximately $7\mathit{g}/\mathrm{s}$ of the lunar regolith simulant at a reasonable speed ($150\mathrm{mm}/\mathrm{s}$) through the tube on the horizontal conveyance and a maximum conveyance tilt angle of 24° in Earth conditions. In addition to the regolith transport, large particles in the regolith were observed to be susceptible to a downward fall in the tube, given the Brazil nut effect, and this feature was proposed to be used as a beneficiation system.

A numerical investigation was conducted on a passive jet flow control method for alleviating unsteady wake oscillation behind a circular cylinder. The study focused on the effects of two crucial parameters—the number of jet holes in a pipe and the radial thickness of a pipe—on the aerodynamic forces acting on a circular cylinder and alternating vortex shedding in the wake. Pressure coefficient distributions, aerodynamic coefficients, vorticity distributions, probability density functions of wake velocities, and production of turbulent kinetic energy were analyzed in detail. Both the fluctuating lift force and the mean drag force acting on the model decreased with an increase in the jet momentum coefficient. The optimal parameters were a 13-hole pipe and a 5% ratio of pipe radial thickness to the cylinder diameter. Under the optimal parameters, fluctuating lift was reduced by 99.57% with a mean drag reduction of 32.41% compared with a bare cylinder. The fluctuating wake of the circular cylinder was almost eliminated. The alternating vortex shedding was converted into two parallel shear layers, and the asymmetric vortex shedding mode was shifted into a symmetric wake mode. The probability density function of the fluctuating transverse velocity in the wake shrank without wide tails, because the production of turbulent kinetic energy in the wake was reduced by over one order of magnitude, which is the intrinsic nature of this passive method to effectively suppress the aerodynamic forces on a circular cylinder and wake oscillation.