Aerodynamic Acceleration Research Articles

Calculate the ignition height of the vertical landing phase online for the reusable rocket

For the vertical landing phase of the reusable rocket, in order to improve the landing accuracy with consideration of multiple uncertainties, a novel strategy to calculate the ignition height online is proposed based on polynomial guidance law (PGL), particle swarm optimization (PSO), and deep reinforcement learning (DRL). Firstly, a deep neural network (DNN) is designed to describe the relationship between the state of the reusable rocket and the ignition height. To accomplish the guidance task of the vertical landing phase, PGL is modified by introducing the estimated aerodynamic acceleration. Through simulation, the output range of the DNN is estimated by the modified PSO. Then, the reward function is shaped and the parameters of the DNN are trained on a training set of simulation scenarios by the DRL algorithm. Finally, to demonstrate the effectiveness of the proposed strategy, the trained DNN is used to calculate the ignition height of 1500 unlearned simulation scenarios online. The numerical simulation results show that the proposed strategy has higher landing accuracy and lower fuel consumption than the offline strategy of fixed ignition height based on the modified PSO.

GRACE-FO radiation pressure modelling for accurate density and crosswind retrieval

Uncertainties in radiation pressure modelling play a significant role in the thermospheric density and crosswind observations derived from the GRACE-FO accelerometer, especially during low solar activity. Under such conditions, the radiation pressure acceleration matches the magnitude of the aerodynamic acceleration along the track and exceeds it in the cross-track direction. The GRACE-FO mission has been operating for several years at such high altitudes during both low and rising solar activity, providing a perfect opportunity to study the effects of radiation pressure. This research uses ray tracing based on a high-fidelity satellite geometry model to calculate the radiation pressure acceleration. We numerically fine-tuned the coefficients describing the thermo-optical surface properties to obtain more accurate radiation pressure accelerations than those specified in the GRACE-FO mission manual. We also used in situ temperature measurements from thermistors on the solar arrays to model the satellite’s thermal emission. These temperature measurements allowed a realistic setup of the thermal model, extended by the parameter describing the efficiency of the solar cells, and reproduced the acceleration of the thermal emission with an accuracy of RMS 0.148 nms−2. The combination of the updated thermal model and the fine-tuning of the surface coefficients improved the accuracy of the crosswind acceleration to an RMS of 0.55 nms−2, compared to an RMS of 4.22 nms−2 when using panel models and instantaneous thermal radiation. We compared the observed crosswind with two models: HWM14 and TIE-GCM. While both models capture most of the salient features of the observed crosswind, HWM14 shows particularly good agreement at high latitudes. Compared to the previously employed radiation pressure model, the crosswind observations have been improved in low and mid-latitudes, especially during periods of higher solar activity. Since the effect of radiation pressure is most significant in the crosswind direction, the effect on density was small compared to previously published datasets.

Patterns of air mixture movement in the operating area for the annular ejector of pneumatic transportation system

Purpose. To establish the regularities of two-phase flow of “gas-solid particles” in the operating area of an annular ejector where the following processes take place: air mixture ejecting, compressed air outflow from the ejector nozzle, air mixture flows mixing in the transport pipeline. In the work, the velocity distribution is also examined for dispersed phase and air phase of air mixture during its loading and accelerating in the transport pipeline of the pneumatic transport system. Methodology. The research is based on the fundamental approaches of mass point dynamics, aerodynamics, the theory of jet flows and iteration methods of numerical solution of equations. Findings. The mechanics of the air mixture flow under the ejection and aerodynamic force in the operating area of an annular ejector and at the beginning of transport pipeline is analyzed using the method of iterations. The impact of air mixture flow in the operating area of an annular ejector on energy performance of the pneumatic transport system is evaluated. Originality. The originality is that, for the first time, the regularities describing two-phase “gas–solid particles” flow at the loading area of the pneumatic transport system with an annular ejector have been obtained. This made it possible to characterize the velocity distribution of the dispersed and air phases of the air mixture during their loading and aerodynamic acceleration in the transport pipeline. Also, an innovative approach to the effectiveness of the use of pipeline pneumatic transport is the assessment of the energy indicators of the use of ejector-type pneumatic transport equipment depending on the rate of compressed air outflow from the ejector. Practical value. The implementation of the results in the modernization of existing and in the creation of new pneumatic transport systems with an annular ejector makes it possible to increase the efficiency of their use in the technological processes of moving dispersed materials at mining and metallurgical enterprises and in other areas of technology.

Trajectory Prediction of Hypersonic Glide Vehicle Based on Empirical Wavelet Transform and Attention Convolutional Long Short-Term Memory Network

Hypersonic glide vehicle (HGV) has brought severe challenges to the existing radar system. Its trajectory prediction is a new problem affecting aerospace security, but it has not attracted extensive attention. The existing approaches provide unsatisfactory accuracy of HGV trajectory prediction due to the neglect of noise processing and the single prediction method. Here, we propose a HGV trajectory prediction method based on empirical wavelet transform (EWT) and attention convolutional long short-term memory (AConvLSTM) network to solve this problem. Firstly, aerodynamic acceleration components of HGV are selected as the prediction parameters, and the dynamic tracking model of HGV is established to estimate the prediction parameters. Secondly, we decompose and reconstruct the prediction parameters of HGV by the EWT and grey correlation degree to reduce noise interference to the prediction model. Finally, the prediction parameters after denoising are used to train the AConvLSTM network to predict the trajectory of HGV. Simulations show that the proposed method can effectively predict the trajectory of HGV using radar tracking data and achieve better prediction accuracy than the existing approaches.

NSHV trajectory prediction algorithm based on aerodynamic acceleration EMD decomposition

Aiming at the problem of gliding near space hypersonic vehicle (NSHV) trajectory prediction, a trajectory prediction method based on aerodynamic acceleration empirical mode decomposition (EMD) is proposed. The method analyzes the motion characteristics of the skipping gliding NSHV and verifies that the aerodynamic acceleration of the target has a relatively stable rule. On this basis, EMD is used to extract the trend of aerodynamic acceleration into multiple sub-items, and aggregate sub-items with similar attributes. Then, a prior basis function is set according to the aerodynamic acceleration stability rule, and the aggregated data are fitted by the basis function to predict its future state. After that, the prediction data of the aerodynamic acceleration are used to drive the system to predict the target trajectory. Finally, experiments verify the effectiveness of the method. In addition, the distribution of prediction errors in space is discussed, and the reasons are analyzed.

Experimental and numerical studies on rebound characteristics of non-spherical particles impacting on stainless-steel at high temperature

In this paper, innovative test methods including aerodynamic acceleration, PIV measurement, separate statistics of incidence and rebound information were used to systematically investigate the rebound characteristics of flaky oxide particles and angular quartz sand impacting stainless steel at high temperature. Through the statistical analysis of a large number of experimental results and the measurement of the microscopic erosion morphology of the target surface, combined with the numerical simulation of the gas-solid two-phase flow of the test section, the intrinsic relationship between the rebound behavior of the particles and their erosion behavior was systematically explored for the first time. Meanwhile, the effects of the incident parameters, particle size and accelerated airflow on the rebound characteristics of the particles were revealed. The results have important guiding significance for further understanding the physical properties of particle-wall interaction and predicting the particle erosion characteristics and erosion distribution of industrial equipment components.

Aerodynamic interference effects of a proposed super high-rise building on the aerodynamic forces and responses of an existing building

Though designers pay careful attention to the aerodynamic interference of existing buildings on a proposed building, they often ignore the aerodynamic interference of the proposed building on existing surrounding buildings, even when the former is much larger or taller than the latter. In the present study, the aerodynamic interference effects of a proposed supertall high-rise building, an adjacent twin building of equal height, and other relatively short buildings on a target building are studied via wind tunnel tests. The results show that the overall aerodynamic forces and acceleration responses of the target building dramatically increase when the proposed supertall high-rise building was constructed upstream because of the induced air flow deflection and vortex shedding. In dense urban centres, the interference effects of constructing a supertall high-rise building on existing surrounding buildings cannot be ignored, even if they are weakened by the presence of shorter surrounding buildings.

Robust-Backstepping Missile Autopilot Design Considering Time-Varying Parameters and Uncertainty

Missile autopilots for aerodynamic angle control and acceleration control are designed for fin-controlled missiles during the boost phase. In the boost phase, the speed change and the parameter variation of the missile are fast and large. To deal with the time-varying characteristics of the missile, the time-varying parameters are considered in nonlinear dynamics, and the parametric uncertainties are modeled. A state-feedback controller is designed for aerodynamic angle control based on a robust-backstepping scheme. Also, an output feedback controller is designed for acceleration control, where the acceleration dynamics are derived using input–output linearization. Numerical simulations are performed to demonstrate the performance of the proposed controllers.

Probabilistic simulation model of fragmentation risk

This paper presents a probabilistic concept of fragmentation risk assessment based on simulation modeling. An original probabilistic mass method for the assessment of fragmentation scenarios of a tank has been proposed. It has been concluded that the generation of individual fragments is accompanied by aleatoric uncertainty, regardless of their mass. The highest frequency of fragmentation occurs with generation of two fragments (17%) and three fragments (average 11%) if their masses range from 10% to 20% of the total mass of the tank. The epistemic uncertainty of the velocity, acceleration and attack angle of a fragment is eliminated by the introduction of initial acceleration and uniform fluctuation of variable parameters (coefficients of aerodynamic and lift acceleration). The range of fragments having a mass between 200 kg and 3500 kg can be adequately described by Weibull's distribution, while 70% of the fragments have a range of 298 m–902 m (average 638 m). The proposed methodological concept has been realized in terms of eliminating epistemic uncertainty in the fragmentation of a tank and is applicable to the analysis of explosions of a variety of process equipment in the process industry.

Dynamics of rebounding Bacillus subtilis spores determined using image-charge detection.

A novel image-charge detection technique was used to investigate the mechanical elasticity of bare bacterial spores during high-velocity impact. Spores of Bacillus subtilis introduced to vacuum using electrospray and aerodynamic acceleration impacted and rebounded off of a glass plate. A dual-stage, asymmetric image-charge detector measured the velocity and direction of each spore both before and after impact with the glass surface. Two ranges of impact velocity were investigated, with average initial velocities of 197±17 and 145±12m/s. Impacts were strongly inelastic, with most of the translational kinetic energy lost upon impact, similar to polystyrene particles of similar size under similar impact velocities. Specifically, 69% (± 16%) and 74% (± 11%) of initial kinetic energy was lost in impacts at the two velocity ranges, respectively. The average coefficients of restitution for the two velocity regimes were 0.53±0.15 and 0.49±0.12. There was no statistically significant difference in the fractional kinetic energy loss between these two populations. The variance of these results is much larger than experiments using polystyrene spheres of comparable size. These results imply significant plastic deformation of the spore-a striking result given that spores of this strain of B. subtilis are known to survive impacts on glass at these velocities. Triboelectric charge transfer during impact was also observed. Although much is known about spore elasticity from static measurements, this is the first study to investigate the elastic properties of bacterial spores in a dynamic scenario, as well as the first demonstration of an image charge detector for measurements of rebounding particles.

Aerodynamic acceleration of heavy particles in a supersonic jet of a binary mixture of gases with disparate-mass components

The method of moments for the ellipsoidal distribution function was used for solving the Boltzmann equation describing binary gas mixtures with large mass disparity and highly diluted heavy component. Analysis of the system of moment equations results in a simple analytic expression for the terminal slip velocities of components that depends on the conditions in the source of jet, composition of mixture, and C6 constant of the attractive branch of the interaction potential. The results are in good agreement with experimental data including low pressure conditions when the Miller-Andres correlation is unsatisfactory.

Mechanical-optical-electro modulation by stretching a polymer-metal nanocomposite

We report the simultaneous investigation of both the plasmonic resonance and electrical conductance evolution in stretchable metal–polymer nanocomposite films. The films are produced by the implantation of neutral gold nanoparticles in a polydimethylsiloxane substrate by aerodynamic acceleration in a supersonic expansion. A redshift of the gold nanoparticle plasmon peak is found upon stretching as well as a strong correlation between the plasmonic peak wavelength and the nanocomposite electrical resistance. Optical simulations attribute the optical response to the compression of the polymer perpendicular to the stretching direction, which brings the gold particles closer to each other, increasing the plasmonic coupling. Mechanical stretching can induce a simultaneous modulation of the optical and electrical properties of the nanocomposite.

Indirect Trajectory Optimization for Mars Entry with Maximum Terminal Altitude

In this paper, a novel computational optimization framework is presented for the design of Mars entry trajectories with maximum terminal altitude. The second-order path constraints included in the framework are the constraints on the dynamic pressure, aerodynamic acceleration, and heat rate. The framework is built on the so-called Pontryagin’s maximum principle, exact penalty method, and simplicial homotopy method. In this framework, the exact penalty method is used to transform the original path-constrained maximum terminal altitude problem into an equivalent path-unconstrained maximum terminal altitude problem. A novel one-parameter penalty function, which is continuous and differentiable at any point, is introduced to penalize the performance index. Then, the resulting path-unconstrained maximum terminal altitude problem is converted to a two-point boundary value problem based on Pontryagin’s maximum principle. Several auxiliary problems are properly constructed such that the simplicial homotopy method can be applied to address the problem of initial guess. By doing so, a ballistic entry trajectory can be taken as an initial guess for the solution of the path-unconstrained maximum terminal altitude problem. Finally, numerical results are presented to demonstrate the effectiveness of the proposed computational optimization framework.

Model of $$J_2$$ J 2 perturbed satellite relative motion with time-varying differential drag

This work revisits the modeling of the relative motion between satellites flying in near-circular low-Earth-orbits. The motion is described through relative orbital elements and both Earth’s oblateness and differential drag perturbations are addressed. With respect to the former formulation, the description of the $$J_2$$ effect is improved by including also the changes that this perturbation produces in both relative mean longitude and relative inclination vector during a drifting phase, when a non-vanishing relative semi-major axis is required. The second major improvement consists in a general empirical formulation to include the mean effects produced by non-conservative perturbations, such as the differential aerodynamic drag acceleration. As a result, in addition to the well-known actions on the relative semi-major axis and on the mean along-track separation, the model is able to reflect the mean variation of the relative eccentricity vector due to atmospheric density oscillations produced by day and night transitions.

On the aerodynamic acceleration of heavy particles in a supersonic stream of a binary mixture with strongly disparate masses of components

Based on the moment method of solving the Boltzmann equation with an ellipsoidal velocity distribution function, the aerodynamic acceleration of particles of a heavy mixture component in trace amounts in a light carrier gas are considered. The simple analytical dependence of the limiting average velocity of heavy component particles on conditions in the source and the constant C6 of the attraction branch of interaction potential are obtained. This ratio well describes data from different experiments, including those at low pressures in the stream source, at which the currently known correlation ratios are unsatisfactory.

Study of the Boundary Layer on a Plate Aerodynamically Induced by Multiple DBD Plasma Based on PIV

The boundary layer aerodynamic flow acceleration with one atmosphere uniform induced by multiple dielectric-barrier-discharge plasma actuation were studied based on PIV. Through double actuators alternating discharge, the multiple dielectric barrier discharge mode have been proposed and tested. The efficiencies of the plasma actuators in Pulsed-pulsed, Steady-steady, Pulsed-steady and Steady-pulsed discharge modes were explored. Based on the above results, the boundary layer flow acceleration performance of multiple plasma actuators has been discussed and the more efficient discharge pattern has been proposed. The results of this study indicate that the airflow acceleration effect of multiple plasma actuators mainly occurs in paraelectric direction and the pulsed-pulsed is the more efficient multiple plasma actuation mode.

Research on Aerodynamic Flow Acceleration Induced by One Atmosphere Uniform DBD Plasma Based on PIV

The aerodynamic flow acceleration with one atmosphere uniform induced by dielectric-barrier-discharge plasma actuation were studied based on PIV. The flow fields induced by the dielectric barrier discharge with different discharge models and actuation parameters were investigated. In term of the obtained velocity distributions, a comparative study on the effect of excitation voltages, carrier frequencies, pulse frequencies and duty ratios on plasma actuation was presented and the optimum actuation parameters was provided. The results of this study indicate: 1) The induced velocity increases linearly with excitation voltage and frequency. 2) When fpfp>300Hz, it shows an opposite tendency.

Power Analysis of Light Electric Vehicles Using Fundamental Calculations

This paper presents a study of the power needed by batteries to drive an electric vehicle for specific purpose using basic theory and fundamental formulas. In order to develop an electric vehicle, the energy and power requirements of the vehicle in various driving environments need to be estimated. The energy efficiency of a vehicle depends primarily upon the specific vehicle design and the environment in which the vehicle is operated. Basic parameters are set off in the beginning such as car weight and much more comprehensive parameter will developed later such as vehicle cruising velocity. Generally, four forces affect vehicle motion; aerodynamic resistance, rolling resistance, climbing resistance and acceleration power. The total of these four forces will result in an estimation of maximum power needed for the electric vehicle.

Electrohydrodynamic force and aerodynamic flow acceleration in surface dielectric barrier discharge

Surface discharges created in dielectric barrier discharge (DBD) configurations have been proposed as actuators for flow control in aerodynamic applications. We focus on DBDs operating in a glow regime, i.e., where the discharge is sustained by ion-induced secondary electron emission from the surface and volume ionization. After a brief discussion of the force per unit volume acting on the flow and due to the momentum transfer from charged particles to neutral molecules, we present calculations of this force based on a two-dimensional fluid model of the surface discharge. We show that this force is of the same nature as the electric wind in a corona discharge. However, the force in a DBD is localized in the cathode sheath region of the discharge expanding along the dielectric surface. While its intensity is much larger than the analogous force in a direct-current corona discharge, it is active during less than one hundred nanoseconds for each discharge pulse and the time-averaged forces in the two cases are comparable, at least for the conditions we have chosen for this study.

Design and Evaluation of an Acceleration Guidance Algorithm for Entry

The design and performance evaluation of an entry guidance algorithm for future space transportation vehicles is presented. The guidance concept is to plan and track aerodynamic acceleration. This concept, on which the longitudinal entry guidance for the Space Shuttle Orbiter is based, is extended to integrated longitudinal and lateral guidance. With integrated longitudinal and lateral guidance, more extreme points in the landing footprint can be reached accurately; in particular, the cross-range capability is extended. The guidance algorithm consists of two components: a trajectory planner and a trajectory tracking law. The planner generates reference drag acceleration and heading angle profiles, along with reference state and bank angle profiles. The planner executes onboard and is capable of generating updates as the entry evolves. The tracking law, based on feedback linearization, commands the angles of bank and attack required to follow the reference drag and heading angle profiles. The planner and tracking law are described, along with additional higher level logic included in the algorithm. Extensive simulations for a set of return-from-orbit entries, including ones requiring large cross range, demonstrate that this algorithm consistently achieves the desired target conditions within allowable tolerances and satisfies all other entry constraints.