High-speed Aircraft Research Articles

Design and Verification of Short-Distance Landing Control System for a One-Third-Scale Unmanned Supersonic Experimental Airplane

The Aerospace Plane Research Center at the Muroran Institute of Technology is currently conducting research to develop enabling technologies for high-speed aircraft traveling at high altitudes and constructing experimental, small-scale, unmanned supersonic aircraft called Oowashi as a testbed for flight. To confirm the control performance of the aircraft, an experiment using a one-third-scale model of the Oowashi aircraft has been planned. The flight of high-speed aircraft always presents the problem of having to land on an ordinary runway regardless of the aircraft’s high speed at the beginning of the landing process. This paper therefore proposes a new landing control design method that can shorten the landing distance for a high-speed aircraft without increasing the rate of descent. The design method utilizes the newly clarified relationship between an angle of attack and the time constant of flare control system, which is effective to raise glideslope angle during landing. The validity of the method is confirmed by computer simulation assuming the model aircraft equivalent to a one-third-scale model of the Oowashi aircraft.

Analysis of Influence of Stratospheric Airship’s Key Parameter Perturbation on Motion Mode

The stratospheric airship is taken as the research object, and the motion mode analysis of the stratospheric airship is carried out. The influence of key parameters such as the center of mass, the center of buoyance, and the aerodynamic stability moment on the motion mode of stratospheric airship are analyzed and summarized in detail. According to the simulation and analysis results, unlike high-speed and high-dynamic aircrafts such as airplanes, the motion modes of the stratospheric airship are hardly affected by the perturbation of aerodynamic stability moment; the perturbations of the vertical center of mass and the vertical center of buoyancy have a great influence on the pitch pendulum motion modes, and their parameter perturbations affect the frequency of the pitch pendulum motion and also the stability of the pitch pendulum motion; the axial mass center location perturbation not only changes the damping of pitch pendulum motion but also affects the frequency of the yaw motion attitude motion mode to a certain extent.

Thermal Insulation Performance of Monolithic Silica Aerogel with Gas Permeation Effect at Pressure Gradients and Large Temperature Differences

ABSTRACT Silica aerogel is an excellent thermal insulator for high-speed aircraft, but there is little research on it in a high-temperature and complex-pressure environment. This research aims to evaluate the thermal insulation performance of silica aerogel monoliths with different porosities under large temperature differences and pressure gradients. We established an experimental system to measure and analyze the hot surface temperature response by fixing the heat flux and the cold surface temperature at transient pressure conditions. An unsteady-state heat transfer model considering gas flow is developed. The effective thermal conductivity of silica aerogels with 79.55 ~ 90.91% porosity is measured at different temperature differences between cold and hot surfaces (127 ~ 512 K), near-vacuum (<10 Pa), and transient pressure conditions. The results demonstrated that silica aerogel with 90.91% porosity showed the best thermal insulation performance when the temperature differences were over 500 K, while the aerogel with 79.55% porosity became the best when the temperature differences were less than 500 K. In addition, both the temperature and pressure difference affect the thermal insulation performance: the energy transport caused by gas flow affects the dynamic temperature response when gas permeability is of the order of 10−15 m2; the thermal insulation performance is improved by increasing gas permeability and pressure difference when gas flow and heat transfer directions are opposite.

Path-Following Control for Thrust-Vectored Hypersonic Aircraft

Thrust vector control (TVC) might be used to control aircraft at large altitudes and in post-stall conditions when aerodynamic control surfaces are ineffective. This study demonstrated that the implementation of the TVC on high-speed aircraft is a reasonable solution and might be an alternative when compared to the complicated reaction control system or large aerodynamic control surfaces. The numerical flight dynamics model of the X-15 experimental aircraft was developed and implemented in MATLAB/Simulink and then used to investigate the proposed solution. The obtained results indicate that the aircraft, equipped with full 3D thrust vectoring and two independent horizontal stabilizers to control the roll angle, was able to achieve flight along the path that was defined by a set of waypoints. This paper also highlights the potential benefits and challenges of using TVC as a control method for aircraft. The results of this study contribute to the growing body of research on aircraft control and simulation. Future work can explore the use of TVC for other aircraft with unique configurations and low maneuverability features.

Manufacturing and damping properties of microflake–nanoflake reinforced carbon fiber epoxy resin matrix composites

Due to the high strength, high modulus, lightweight and other characteristics, carbon fiber reinforced polymer (CFRP) is widely used in aerospace, high-speed aircraft, and other fields. In this article, a high-damping CFRP reinforced by flake polyurethane fillers is prepared with good mechanical properties, and the effects of flake polyurethane fillers on the mechanical and damping properties of CFRP are studied. The results show that the mechanical and damping properties of CFRP could be significantly improved by the appropriate content of the flake polyurethane fillers. In addition, the optimal content of the flake polyurethane fillers is 3 wt.%, and the flexural strength, interlaminar shear strength, and damping properties of CFRP are increased by 6.19%, 12.07%, and 9.48%, respectively.

Reducing the Mutual Coupling of Cylindrical Circular Microstrip Antennas (CCMAs) Array Using EBG Structure

A theoretical study to design a conformal microstrip antennas was introduced in this work. Conformal microstrip antennas define antennas which can be conformed to a certain shape or to any curved surface. It is used in high-speed trains, aircraft, defense and navigation systems, landing gear and various communications systems, as well as in body wearable. Conformal antennas have some advantages such as a wider-angle coverage compared to flat antennas and low radar cross-sectional (RCS) and they are suitable for using in Radome. The main disadvantage of these antennas is the narrow bandwidth. The FDTD method is extremely useful in simulating complicated structures because it allows for direct integration of Maxwell's equations depending on time. The 1x2 cylindrical circular microstrip antennas array is designed and simulated vertically via Finite Difference Time Domain (FDTD) method where can directive antenna be achieved through antennas array design. Mutual coupling between the antennas in the array and the different separation between them were studied. The circular patch is excited by a probe feed method for several reasons including providing less spurious radiation from the probe current, in addition to the simplicity in theoretical engineering installation and practical manufacturing. It is well known that the values of the coupling are decreased as the distance separation increased. Cylindrical circular microstrip antenna with resonant frequency operating is 3.5GHz for mode, several parameters like return loss, band width, and input impedance are calculated. Also, for isolated coupling, mutual coupling coefficients, directivity gain, for different separations between the centers of the two adjacent circular patches in terms the wave length operating are calculated. Moreover, the electromagnetic band gap EBG structure is used for reducing the mutual coupling created by the surface waves in order to enhance the antenna's performance in an array has become smaller than before. The proposed EBG is a three triangular-shape equal sides metallic structure, utilizing the inter-element spacing in an array. The less value of for the spacing between the two centers of patches is . BW percentage increased to 34.3% and the directivity is enhanced also. Additionally, simulations were done using MATLAB 2017b.

Estimation of the influence of grid resolution on the results of numerical simulation the flow around a high-speed aircraft

The most important step in the correct solution of discrete analogs of the equations of gas dynamics for the high-speed flow of a compressible chemically active gas using grid methods is to ensure sufficient grid resolution of regions with high gradients of gas-dynamic parameters, that is, the region of the departed curvilinear shock wave compressed and boundary layer. In this work, the grid independence of the main flow parameters on the dimensionality of the computational grid was checked on the problem of flowing a sphere by a high-speed flow of a gas mixture. The dependences of gas-dynamic flow parameters on the grid resolution along the normal to the sphere surface are revealed. The conclusions about the sufficiency of the grid resolution for a particular problem have been made.

Identification method of temperature corrections to aircraft engine thrust in flight tests

The article is devoted to identifying the dependence of thrust on the outside air temperature for a turbojet engine as part of an aircraft. A methodic that allows to determine temperature corrections to the effective thrust of a turbojet engine at fixed operating modes during flight tests is presented. The application of the developed methodology in flight testing of a high-speed high-altitude aircraft is shown. A distinctive feature of the method is the calculation of the engine thrust increment through the excess thrust coefficient at zero lift in straight-line horizontal acceleration modes. Keywords aircraft, aircraft testing, turbojet engine, thrust identification, turbojet engine characteristics

Real-time identification of severe heat loads over external interface of lightweight thermal protection system

The lightweight thermal protection system (LTPS) is typically employed on the exterior surface of high-speed aircraft to prevent the penetration of high-temperature heat flux. The sequential function specification method (SFSM) is exploited in this study to solve the inverse issue in anticipation of the external-surface heating conditions of a lightweight thermal protection system by entering temperature data at a single measurement station. The results show that the inversion accuracy is significantly dependent on the temperature acquisition position as well as the forecast time step. Adding noise to the temperature data reveals that temperature noise aggravates the volatility of the inverse heat flux, necessitating an increase in the forecast time step to enhance the inverse accuracy. The experiment of a light thermal protection system demonstrates that the approach can efficiently and correctly recover the boundary heat flux by employing the inner wall temperature of the thermal protection structure.

Analysis of the influence of aerodynamic heating in ascent stage on infrared radiation characteristics of high-speed aircraft in midcourse

Analysis of the influence of aerodynamic heating in ascent stage on infrared radiation characteristics of high-speed aircraft in midcourse

БЛОК АНТЕННЫЙ С УЛУЧШЕННЫМИ ХАРАКТЕРИСТИКАМИ НА ОСНОВЕ АНТЕННЫ ПРОДОЛЬНОГО ИЗЛУЧЕНИЯ ЧЕРЕЗ ДИЭЛЕКТРИЧЕСКИЙ ОТКРЫТЫЙ ВОЛНОВОД

Results of work on upgrade of antenna assemblies of the equipment of setting of noises of the REB equipment of high-speed aircraft are presented in article. As a result of the carried-out upgrade the antenna assembly surpassing applied with the improved electroresponse and constructive characteristics, executed completely on domestic materials is developed.

Polycyclic aromatic hydrocarbons production from the supercritical pyrolysis of n-decane, ethylcyclohexane, and n-decane/ethylcyclohexane blends

To investigate the effects of fuel composition on the production and growth of polycyclic aromatic hydrocarbons (PAH) at conditions relevant to the pre-combustion environment of fuels in future high-speed aircraft, we have conducted supercritical pyrolysis experiments in an isothermal, silica-lined stainless-steel flow reactor at 568 °C, 94.6 atm, and 133 s, with the model fuels n-decane and ethylcyclohexane—as well as n-decane/ethylcyclohexane blends in which the fraction of fuel carbon coming from ethylcyclohexane is 0.25, 0.50, and 0.75. High-pressure liquid-chromatographic analyses of the reaction products have led to the isomer-specific identification and quantification of 169 three- to nine-ring PAH—159 of which have never before been reported as products of a cyclic-alkane fuel. Quantification of the aliphatic products by gas chromatographic techniques reveals that n-decane produces mostly 1-alkenes and n-alkanes, whose radicals generate more radicals; whereas ethylcyclohexane produces mostly C5-ring and C6-ring alkanes and alkenes, whose radicals show a propensity for ring dehydrogenation. These contrasts in the aliphatic-product distributions have major impacts on PAH growth, which, in this reaction environment, occurs chiefly through the reactions of resonance-stabilized arylmethyl radicals with the C2-C4 1-alkenes. For fuel compositions rich in n-decane, all the ingredients necessary for these PAH-growth reactions to thrive are in place: methyl-substituted PAH, as sources of arylmethyl radicals; a radical-rich environment that fosters H abstraction and arylmethyl-radical formation; and C2-C4 1-alkenes, as growth species. However, an increase in the level of ethylcyclohexane in the fuel brings about substantial reductions in the levels of H-abstracting radicals and C2-C4 1-alkenes as well as an increase in the supply of “donated” hydrogen for stabilizing radicals. These factors combine to bring about marked reductions in PAH growth at fuel compositions rich in ethylcyclohexane, resulting in much lower production of the high-ring-number PAH that are the precursors to solids in the supercritical fuel-pyrolysis environment.

Trajectory Optimization for High-Speed and Long-Range Interceptor Based on Improved Adaptive hp Pseudospectral Method

The trajectory optimization design of interceptor is very important in the defense combat against a class of high-speed and strong-maneuvering aircraft. At present, an important idea is to use hp pseudospectral method to offline optimizes the trajectory of interceptor, but the solving efficiency of this method needs to be further improved. Aiming at this issue, an improved adaptive hp pseudospectral method is proposed in this paper. In order to shorten the solving time of the algorithm, the proposed method has two main improvements on the basis of the traditional hp pseudospectral method: on one hand, by judging the positions of the control sudden change points, prerefine the mesh around them according to certain rules. On the other hand, the curvature of the system state curve is used as the criterion to segment the original mesh nonuniformly so that more mesh points can be allocated where the curvature is large. These two points together ensure that the collocation point resources can be used more efficiently in the mesh refinement process. The simulation results show that the proposed method can solve the optimized trajectory of interceptor effectively, and it also proves that this method has higher solving efficiency than the traditional adaptive hp method.

Photochemical Method for Laser Absorption.

During the laser application process, laser energy is usually converted into heat energy, causing high temperature, which affects the (high-speed) aircraft in routine flight. A completely novel photochemical method was investigated to potentially minimize the energy effect of the laser beam. Ag nanoparticles/C3N4 were synthesized by an ultra-low temperature reduced deposit method with Ag mean diameters of 5-25 nm for photofixation of N2. The absorption performance of laser can be improved by using appropriate charge density and small size Ag metal particles. The energy absorption rate was 7.1% over Ag/C3N4 (-40) at 5 mJ/cm2 of laser energy.

Active Disturbance Rejection Control of DC-Bus Voltages Within a High-Speed Aircraft Electric Starter/Generator System

Wide-speed range operation capabilities in both motoring and generation modes are essential for an aircraft electrical starter/generator (ESG) drive system for more-electric aircraft applications. When running as a generator, the ESG is supplying power to the main HVdc bus within the onboard electrical system. A fast and robust dc bus voltage would be beneficial to electrical loads connected to it. In this article, an active disturbance rejection control (ADRC) is proposed to realize a fast and robust regulation of onboard dc bus voltages. The ADRC is achieved with a second-order extended state observer (ESO) to generate torque reference for the ESG. All the key characteristics, such as the stability of ESO, dc voltage tracking performance, and disturbance rejection capability of the ADRC for aircraft ESG applications, are thoroughly analyzed. To enhance system stabilities, an innovative and simple design method for the ADRC and ESO gains is introduced based on the gain-margin and phase-margin criteria. Experimental results have shown that, compared with the conventional PI-based dc voltage control, the proposed method can realize a faster and more robust dc voltage control.

Towards a formalized model-based process for the design of high-speed aircraft and related subsystems

Increasing complexity associated to advanced aircraft concepts for high-speed flight is pushing the limit of engineering practices concerning design phases of products lifecycle. Specific methodologies aimed at managing requirements over the entire vehicle architecture definition shall then be properly formalized and supported by means of standardized processes and languages in order to be effective. The approaches suggested by the Systems Engineering practices, especially when considering the model-based environments as main tools for systems design, can be exploited to face these challenges, if properly tailored to suit the specific engineering field considered. This paper aims at proposing a model-based process for the design of high-speed aircraft exploiting a formalized methodology and the typical tools of Systems Engineering. A conceptual design exercise, based on the STRATOFLY MR3 hypersonic cruiser case study, is performed from high-level stakeholder objectives to vehicle performance estimations, passing through functional and interface analyses. Additionally, some insights concerning on-board subsystems sizing activities are provided in terms of integration within the high-level design process. The whole work highlights the capability of performing a seamless requirements management and development within the design procedure, particularly focussing on the relationships among the different stages of the workflow.

Conceptual design and its optimization of an air-cooled nuclear reactor for aircraft propulsion considering both thermal and neutronic performance

Air-cooled nuclear-powered engine is a good choice for low-attitude and high-speed aircraft soon. To achieve better propulsion performance, a conceptual design for air-cooled reactors with the aim of minimum size and high thrust-weight ratio is conducted in this work, where both thermal-hydraulics and neutronics targets are satisfied to make sure its safety under extreme operating conditions. The nuclear engine composed of the diffuser, the reactor, and the nozzle is modeled with simplification to mainly calculate heat transfer and pressure drop inside the flow channels of the reactor core. The relation of thrust and specific impulse is investigated to show the operation range of the engine. Geometrical dimensions of the air-cooled reactor core are minimized to offer the rated output thrust of 120 kN. For this optimal design, wall temperature of the reactor remains below the upper limit of 1644 K, and the core theoretically reaches criticality based on the critical buckling got from Monte-Carlo simulations of a fuel unit. Additionally, the neutronics analysis is then employed for the entire reactor. Attribute to Gd2O3 added in the fuel matrix, shutdown margin keeps below −1 $ under the submersion accident. This work finally proposes a design of the air-cooled reactor with a mass of 2.6 ton loaded by high-enriched uranium oxide, which could provide the high-speed cruise aircraft with the thrust of 120 kN at sea level for 15 days.

Thermoelectric detector application for measuring the ignition delay time in a shock heated combustible mixture

The problem of flight safety of high-speed aircrafts is primarily related to the reliability of engines, which, in turn, depends on the correct understanding of the processes of ignition and combustion of fuel in the combustion chambers of engines during their design. In this work, a new method for registration the ignition of shock heated gaseous fuels using a thermoelectric detector is proposed. The detector well measures the ignition delay time of fuels in the microsecond range, which is characteristic of detonation processes in the combustion chambers of promising aircraft engines operating on detonation combustion. The efficiency of the detector is demonstrated by the ignition of a propane-air mixture behind a reflected shock wave as an example. During the experiments, the thermoelectric detector showed such properties as the ability to register high heat flux values, low inertia, high signal-to-noise ratio, and high temporal resolution. The data obtained are compared with the measurement data of the ignition delay time by optical and piezoelectric methods obtained in this work, as well as in the studies of other authors.

Calculation of Heat Transfer and Drag Coefficients for Aircraft Geometric Models

A numerical model to calculate the heat transfer and resistance coefficients near the bodies of complex geometric shapes moving at high velocity is formulated. The processes of heat and mass transfer and flow around aircraft elements are considered. An algorithm for calculating heat fluxes and the heat transfer coefficient is proposed. The developed numerical technique can give an idea of the essential features of the flow, heat transfer at the end keels of the wings, and integral layouts of high-speed aircraft. An approximate mathematical model for calculating the heat transfer processes and resistance coefficients near the bodies of complex geometric shapes moving at high speed in the Earth’s atmosphere is formulated. The calculated results for convective heat transfer and friction coefficients for the X-33 and X-43 vehicles are obtained.

Genetic Diversity and Population Genetic Structure of Aedes albopictus in the Yangtze River Basin, China.

Aedes albopictus is an indigenous primary vector of dengue and Zika viruses in China. Understanding the population spatial genetic structure, migration, and gene flow of vector species is critical to effectively preventing and controlling vector-borne diseases. The genetic variation and population structure of Ae. albopictus populations collected from 22 cities along the Yangtze River Basin were investigated with nine microsatellite loci and the mitochondrial CoxI gene. The polymorphic information content (PIC) values ranged from 0.534 to 0.871. The observed number of alleles (Na) values ranged from 5.455 to 11.455, and the effective number of alleles (Ne) values ranged from 3.106 to 4.041. The Shannon Index (I) ranged from 1.209 to 1.639. The observed heterozygosity (Ho) values ranged from 0.487 to 0.545. The FIS value ranged from 0.047 to 0.212. All Ae. albopictus populations were adequately allocated to three clades with significant genetic differences. Haplotype 2 is the most primitive molecular type and forms 26 other haplotypes after one or more site mutations. The rapid expansion of high-speed rail, aircraft routes and highways along the Yangtze River Basin have accelerated the dispersal and communication of mosquitoes, which appears to have contributed to inhibited population differentiation and promoted genetic diversity among Ae. albopictus populations.