Search

DLR is currently investigating the potential of hypersonic flight systems in the context of different mission scenarios. One configuration type of higher interest for civil and military purposes is the hypersonic glide vehicle (HGV). Such HGVs operate over broad flight envelopes and pose complex flight dynamic characteristics. This article presents DLR's generic hypersonic glide vehicle 2 (GHVG-2) and proposes an integrated non-linear flight control architecture that is based on the idea of the non-linear dynamic inversion and non-linear model following control methodologies. The proposed control scheme is designed to sufficiently and robustly handle the system dynamics of the over-actuated flight vehicle. The approach is first discussed, and the performance of the suggested control laws is later investigated via simulations of a high-fidelity non-linear flight dynamic model in the nominal case and under the presence of parametric uncertainties. The presented results demonstrate that the proposed NMFC approach provides benefits for the robust control of the regarded hypersonic system. [ABSTRACT FROM AUTHOR]

On 18 February 2021 the Mars 2020 mission's Perseverance rover successfully landed on Jezero crater. The spacecraft's entry, descent, and landing (EDL) sequence included a 21.53 m supersonically deployed disk-gap-band (DGB) parachute that was a strengthened version of the parachute used by the Mars Science Laboratory mission to land the Curiosity rover in 2012. This paper will provide an overview of the Mars 2020 parachute decelerator system, summarize the methodology and data sources used to reconstruct the spacecraft's trajectory, and describe the parachute system's performance in flight. The parachute system was found to have performed nominally throughout. The parachute was mortar deployed at a Mach number of 1.82 and a dynamic pressure of 518 Pa. The deployment, canopy extraction, and inflation were observed to be orderly with no significant causes for concern identified. The peak inflation force was 152.3 kN (34.2 klbf), which was well below the parachute's flight limit load of 222 kN (50 klbf). Following inflation, the supersonic and subsonic aerodynamics of the parachute and the dynamics of the system were nominal. [ABSTRACT FROM AUTHOR]

Jet fuel in aircraft fuel tanks moves due to acceleration resulting from maneuvers. The movement mentioned here directly impacts the Center of Gravity (CG). The aircraft's flight mechanics are significantly affected by the deviation of its CG on the aircraft body, and excessive deviation is undesirable. Preventing CG deviation is achieved by designing various baffles within the fuel tank. In this study, design details of the baffles were investigated with the help of an artificial neural network (ANN) model, 1D simulations, and computational fluid dynamics (CFD) calculations. The 1D simulations, which model the fuel movement, were used to understand the general behavior of the fluid in the tank. CFD calculations simulating turbulent fluid flow in three dimensions were used to confirm the results of the 1D simulations and provide more detailed information. A simulation set is created utilizing five parameters: barrier usage, volume fraction, cutout diameter, number of cutouts, and cutout location. Compared to the barrierless design, the barrier usage as a parameter changes either on baffle number 1, 3, and 6, or on baffle number 2, 4, and 7. The fuel volume fraction parameter accounts for 30%, 45%, and 60% of the interior volume. The diameters of the cutout holes vary between 30 mm and 156 mm and are used as categorized among the baffles. Cutout holes are applied on baffles in single, twin, and triplet forms and their locations are subjected to a divergence of either −20 mm or +20 mm from the z-axis. Based on these parameters, the maximum deviation and the retreat time of CG constitute the output parameters. The importance of the input parameters on the outputs was obtained with the help of an ANN algorithm created from the results of all possible combinations of a sufficient number of 1D simulations. To obtain more detailed results and confirm the importance of input parameters on outputs, selected cases were simulated with CFD. As a result of all analyses, it was revealed that barrier usage is the most dominant input parameter on CG deviation followed by volume fraction, cutout hole diameter, cutout divergence, and finally, the number of cutout holes. This study identifies the dominant input parameters to control fuel sloshing, specifically CG deviation and retreat time in the fuel tank, and proposes baffle designs to promote robust flight stability. [ABSTRACT FROM AUTHOR]

Launching a fixed-wing unmanned aerial vehicle (UAV) out of the cargo hold of a flying transport aircraft (TA) is numerically investigated. A numerical tool chain is established to capture the dynamic motion of the UAV during launch, in which the DLR-TAU Code flow solver is coupled with a flight mechanics tool. A parameter study investigates how the UAV launch speed, position, and orientation relative to the loading platform of two different TAs affect its trajectory and aerodynamic behaviors. Furthermore, the influence of the angle of attack of the TA on the UAV trajectory and pitch angle is analyzed. This information will help design a launch mechanism that ensures a safe separation and aerodynamically stable flight after launch. [ABSTRACT FROM AUTHOR]

Abstract Background Mayflies are basal winged insects of crucial importance for the understanding of the early evolution of Pterygota. Unlike all other insects, they have two successive winged stages, the subimago and the imago. Their forewings feature so-called bullae, which are desclerotized spots in the anterior main veins. Up to now, they have been considered to play a major role in wing bending during flight. Results We investigated bullae by multiple methods to reveal their structure and arrangement and to gain new information on the evolution of insect flight. Bullae are mostly present in the anterior negative wing veins, disrupting the otherwise rigid veins. High-speed videography reveals that mayfly wings do not bend during flight. Likewise, different arrangements of bullae in different species do not correlate with different modes of flying. Observations on the moulting of subimagines unravel that they are essential for wing bending during the extraction of the imaginal wing from the subimaginal cuticle. Bullae define predetermined bending lines, which, together with a highly flexible wing membrane enriched with resilin, permit wing bending during subimaginal moulting. Bullae are only absent in those species that remain in the subimaginal stage or that use modified modes of moulting. Bullae are also visible in fossil mayflies and can be traced back to stemgroup mayflies of the Early Permian, the 270 million years old Protereismatidae, which most probably had bullae in both fore- and hind wings. Conclusions Bullae in mayfly wings do not play a role in flight as previously thought, but are crucial for wing bending during subimaginal moulting. Thus, the presence of bullae is a reliable morphological marker for a subimaginal life stage, confirming the existence of the subimago already in Permian Protereismatidae. A thorough search for bullae in fossils of other pterygote lineages may reveal wheather they also had subimagines and at what point in evolution this life stage was lost. In mayflies, however, the subimago may have been retained due to selective advantages in connection with the transition from aquatic to terrestrial life or due to morphological requirements for a specialized mating flight.

This paper focuses on the mission analysis of the return trajectory of a Vertical Landing Reusable Launch Vehicle, both for Return-to-Launch-Site (RTLS) and DownRange Landing (DRL) recovery strategies. The main objective is to assess the mission performance of propellant-optimal re-entry and landing trajectories from the Main Engine Cut-Off (MECO) while considering propellant budget and peak entry conditions constraints. As a result, performance envelopes and feasibility regions are built to comprehensively assess the required propellant and compare recovery strategies across a broad spectrum of MECO conditions. The results show that the DRL strategy achieves higher efficiency concerning the propellant consumption and a larger robustness regarding the dispersed MECO conditions. [ABSTRACT FROM AUTHOR]

• A novel guidance algorithm for drag-modulated aerocapture is presented. • The algorithm is compared in detail to an efficient implementation of the state of the art solution, a numerical predictor-corrector, and is shown to achieve equivalent targeting performance for significantly lower computational expense. • This contribution could thus meaningfully advance the near-term technical feasibility of drag-modulated aerocapture. Aerocapture is a method of achieving orbit insertion via a single pass through the atmosphere of the central body. Single-event jettison drag modulation is a simple way of achieving control during atmospheric flight by effecting a discrete change in the aerodynamics of the vehicle. A novel guidance algorithm, energy reference guidance, is developed and implemented for a reference scenario of a small satellite aerocapture demonstration at Earth, and is compared to the baseline numerical predictor–corrector solution. The new approach is shown to achieve equivalent apoapsis targeting performance as the baseline algorithm with significantly lower CPU demand during atmospheric flight, although more onboard memory is required in exchange. The relationship between targeting performance and required memory is quantitatively explored for the new algorithm; the selected configuration generates approximately 3.3 MB of data, which is expected to be well within the capability of relevant avionics systems. [ABSTRACT FROM AUTHOR]

Background: Mayflies are basal winged insects of crucial importance for the understanding of the early evolution of Pterygota. Unlike all other insects, they have two successive winged stages, the subimago and the imago. Their forewings feature so-called bullae, which are desclerotized spots in the anterior main veins. Up to now, they have been considered to play a major role in wing bending during flight. Results: We investigated bullae by multiple methods to reveal their structure and arrangement and to gain new information on the evolution of insect flight. Bullae are mostly present in the anterior negative wing veins, disrupting the otherwise rigid veins. High-speed videography reveals that mayfly wings do not bend during flight. Likewise, different arrangements of bullae in different species do not correlate with different modes of flying. Observations on the moulting of subimagines unravel that they are essential for wing bending during the extraction of the imaginal wing from the subimaginal cuticle. Bullae define predetermined bending lines, which, together with a highly flexible wing membrane enriched with resilin, permit wing bending during subimaginal moulting. Bullae are only absent in those species that remain in the subimaginal stage or that use modified modes of moulting. Bullae are also visible in fossil mayflies and can be traced back to stemgroup mayflies of the Early Permian, the 270 million years old Protereismatidae, which most probably had bullae in both fore- and hind wings. Conclusions: Bullae in mayfly wings do not play a role in flight as previously thought, but are crucial for wing bending during subimaginal moulting. Thus, the presence of bullae is a reliable morphological marker for a subimaginal life stage, confirming the existence of the subimago already in Permian Protereismatidae. A thorough search for bullae in fossils of other pterygote lineages may reveal wheather they also had subimagines and at what point in evolution this life stage was lost. In mayflies, however, the subimago may have been retained due to selective advantages in connection with the transition from aquatic to terrestrial life or due to morphological requirements for a specialized mating flight. [ABSTRACT FROM AUTHOR]

Jet fuel in aircraft fuel tanks moves due to acceleration resulting from maneuvers. The movement mentioned here directly impacts the Center of Gravity (CG). The aircraft’s flight mechanics are significantly affected by the deviation of its CG on the aircraft body, and excessive deviation is undesirable. Preventing CG deviation is achieved by designing various baffles within the fuel tank. In this study, design details of the baffles were investigated with the help of an artificial neural network (ANN) model, 1D simulations, and computational fluid dynamics (CFD) calculations. The 1D simulations, which model the fuel movement, were used to understand the general behavior of the fluid in the tank. CFD calculations simulating turbulent fluid flow in three dimensions were used to confirm the results of the 1D simulations and provide more detailed information. A simulation set is created utilizing five parameters: barrier usage, volume fraction, cutout diameter, number of cutouts, and cutout location. Compared to the barrierless design, the barrier usage as a parameter changes either on baffle number 1, 3, and 6, or on baffle number 2, 4, and 7. The fuel volume fraction parameter accounts for 30%, 45%, and 60% of the interior volume. The diameters of the cutout holes vary between 30 mm and 156 mm and are used as categorized among the baffles. Cutout holes are applied on baffles in single, twin, and triplet forms and their locations are subjected to a divergence of either −20 mm or +20 mm from the z-axis. Based on these parameters, the maximum deviation and the retreat time of CG constitute the output parameters. The importance of the input parameters on the outputs was obtained with the help of an ANN algorithm created from the results of all possible combinations of a sufficient number of 1D simulations. To obtain more detailed results and confirm the importance of input parameters on outputs, selected cases were simulated with CFD. As a result of all analyses, it was revealed that barrier usage is the most dominant input parameter on CG deviation followed by volume fraction, cutout hole diameter, cutout divergence, and finally, the number of cutout holes. This study identifies the dominant input parameters to control fuel sloshing, specifically CG deviation and retreat time in the fuel tank, and proposes baffle designs to promote robust flight stability.

This paper presents a study on the aeromechanical characteristics of a box-wing aircraft configuration with a focus on stability, controllability, and the impact of aeromechanical constraints on the lifting system conceptual design. In the last decade, the box-wing concept has been the subject of several investigations in the aeronautical scientific community, as it has the potential to improve classic aerodynamic performance, aiming at reducing fuel consumption per unit of payload transported, and thus contributing to a reduction in aviation greenhouse emissions. This study characterises the aeromechanical features of a box-wing aircraft, with a specific focus on the correlations between the aeromechanical constraints and the (main) aircraft design parameters. The proposed approach provides specific insights into the aeromechanical characteristics of the box-wing concept, both in the longitudinal and lateral plane, which are useful to define some overall design criteria generally applicable when dealing with the conceptual design of such an unconventional aircraft configuration. [ABSTRACT FROM AUTHOR]

Flight has become a common everyday occurrence. We have engineered ever more efficient and reliable aircraft, facilitating safe transportation around the world. However, from the education literature on the topic of lift, online discussions, and YouTube, it becomes apparent that there are underlying pedagogical issues. The 2003 New York Times article by Chang and the 2020 Scientific American article by Regis conclude that no one really understands flight. These claims are made without regard for the underpinning science and engineering responsible for the modern aviation industry. Although, it does beg the question, why is there confusion about how wings work? Several factors have conspired together, resulting in this confusion. Fluid mechanics is a complex topic that stumped legends of physics and mathematics for centuries. It also contains paradoxes, exacerbating the complexity. However, the central thesis of this work is that knowledge about aerodynamics is not easy to construct due to two main factors. First, there are epistemological traps that directly lead to fallacious conclusions. Second, representativeness heuristics incorrectly apply behaviors of visible water to invisible air. While many assume they know how wings work, if they do not understand why there is confusion, rather than dismissing it, confusion will endure. [ABSTRACT FROM AUTHOR]

The science education literature is littered with "new", "correct", "novel", "explanations", "theories", and "approaches" to aerodynamic lift. One might infer from reading the growing number of these articles that there is a fundamental gap in classical physics, where our scientific prowess has failed us. In fact, if you read popular sources, you would believe "no one can explain why planes stay in the air". This is a disconcerting thought to have while sitting inside a modern engineering marvel provided by Boeing or Airbus. However, rationally, since you are sat in that fuel-efficient and safe aeronautical wonder, the logical conclusion is that some are obviously aware of why planes stay in the air. In this paper, a century of educational literature on the topic of aerodynamic lift and flight is presented. The body of literature encompasses 140 articles, commencing in 1920. It is obvious from the content contained within them that there is more of a misunderstanding rather than an understanding of flight in the education context. There are two paradigms treated as mutually exclusive: those using Bernoulli and those using Newton. Throughout the literature, there are gems lost in the rubble; if the reader does not have an understanding, how will they know what is worth reading? This review attempts to clarify what is worth reading, by presenting a qualitative overview of aerodynamics education in undergraduate engineering, to understand why these opposing camps exist in the literature. [ABSTRACT FROM AUTHOR]

The aeronautics studies and particularly the development of drones represent an important field, in which there is a very large number of research and studies. This article aims to present an experimental aerodynamic study of an autonomous surveillance unmanned aerial vehicle (UAV) that is capable of combining the advantages of both categories, namely the fixed-wing drones and the rotary-wing drones. To achieve this objective, a wind tunnel was used to study the flow around this drone in order to better understand the aerodynamic phenomena and to obtain some initial estimates of the lift, drag and moment coefficients, at three different Reynolds numbers of 4.02×104, 6.03×104 and 8.04×104, and for different angles of attack, from [−45°, +45°] with step of 1°.The experimental results obtained in this work show an casi-symetrical variation between the negative and positive incidence angles of the lift coefficient, which indicate that the heliplane can fly in an inverted position, whatever the angle of incidence. Moreover, the minimum mean value of drag coefficient according 1° incidence angle is 0.0478 then the drag due to geometry and pitching moment can never be canceled.

China is one of the countries and regions significantly affected by wind damage, which can not only cause damage to engineering structures, but also lead to structural collapse. Windborne debris are a kind of high-speed motion debris formed by structural damage and destruction under strong wind, and their impact poses a secondary threat to the safety of the surrounding structures and personnel. Chinese and overseas scholars have carried out relevant research work on windborne debris in recent years. Based on this, the current domestic and foreign research progress was described from three aspects: formation mechanism, flight characteristics and impact effect of windborne debris. Future research suggestions and development directions were proposed, so as to provided reference for further deepening the research of windborne debris and their prevention and control work. [ABSTRACT FROM AUTHOR]

This paper focuses on the mission analysis of the return trajectory of a Vertical Landing Reusable Launch Vehicle, both for Return-to-Launch-Site (RTLS) and DownRange Landing (DRL) recovery strategies. The main objective is to assess the mission performance of propellant-optimal re-entry and landing trajectories from the Main Engine Cut-Off (MECO) while considering propellant budget and peak entry conditions constraints. As a result, performance envelopes and feasibility regions are built to comprehensively assess the required propellant and compare recovery strategies across a broad spectrum of MECO conditions. The results show that the DRL strategy achieves higher efficiency concerning the propellant consumption and a larger robustness regarding the dispersed MECO conditions.

Retrospective health analysis was performed having the data from 211 airline pilots and 168 flight mechanics with symptoms of chronic sensorineural hearing loss gathered in the period from 2015 to 2020. There were 2 control groups. One group consisted of bus drivers comparable to pilots in terms of acoustic environment and work intensity. The other group included power station operators working in standard acoustic environments and doing intensive work. The results of research revealed statistically significant differences between pilots and control group examinees in frequency of circulatory system diseases of pilots – 22.45 [– 7.08; 71.19], respiratory organs – 0.18 [0.07; 0.44], digestive organs – 17.13 [1.90; 154.21], musculoskeletal and connective tissue – 15.44 [0.93; 254.97], nervous, urogenital system – 11.49 [0.79; 167.61]. In comparison with the control groups, pilots were at a higher risk of cerebral atherosclerosis 13.79 [2.81; 67.58], essential hypertension 14.25 [1.01; 200.78], spinal osteochondrosis 3.00 [0.39; 22.95], prostate hyperplasia 2.29 [0.11; 48.82] and chronic prostatitis 3.43 [0.20 ; 57.65]. Also stated was a statistical difference in the medium of chronic diseases at the retirement age in pilots and flight mechanics in comparison with the control members: 6.0 (4.0–8.0) pilots, 6.0 (4.5–8.0) flight mechanics, 3.0 (1.0–5.0) drivers, 2.0 (1.0–3.0) operators; р < 0.05. [ABSTRACT FROM AUTHOR]

This paper presents a study on the aeromechanical characteristics of a box-wing aircraft configuration with a focus on stability, controllability, and the impact of aeromechanical constraints on the lifting system conceptual design. In the last decade, the box-wing concept has been the subject of several investigations in the aeronautical scientific community, as it has the potential to improve classic aerodynamic performance, aiming at reducing fuel consumption per unit of payload transported, and thus contributing to a reduction in aviation greenhouse emissions. This study characterises the aeromechanical features of a box-wing aircraft, with a specific focus on the correlations between the aeromechanical constraints and the (main) aircraft design parameters. The proposed approach provides specific insights into the aeromechanical characteristics of the box-wing concept, both in the longitudinal and lateral plane, which are useful to define some overall design criteria generally applicable when dealing with the conceptual design of such an unconventional aircraft configuration.

Flight has become a common everyday occurrence. We have engineered ever more efficient and reliable aircraft, facilitating safe transportation around the world. However, from the education literature on the topic of lift, online discussions, and YouTube, it becomes apparent that there are underlying pedagogical issues. The 2003 New York Times article by Chang and the 2020 Scientific American article by Regis conclude that no one really understands flight. These claims are made without regard for the underpinning science and engineering responsible for the modern aviation industry. Although, it does beg the question, why is there confusion about how wings work? Several factors have conspired together, resulting in this confusion. Fluid mechanics is a complex topic that stumped legends of physics and mathematics for centuries. It also contains paradoxes, exacerbating the complexity. However, the central thesis of this work is that knowledge about aerodynamics is not easy to construct due to two main factors. First, there are epistemological traps that directly lead to fallacious conclusions. Second, representativeness heuristics incorrectly apply behaviors of visible water to invisible air. While many assume they know how wings work, if they do not understand why there is confusion, rather than dismissing it, confusion will endure.

This paper introduces a new intelligent tuning for the model predictive control (MPC) based on an effective intelligent algorithm named the bat-inspired algorithm (BIA) for the aircraft longitudinal flight. The tuning of MPC horizon parameters represents the main challenge to adjust the system performance. So, the BIA algorithm is intended to overcome the tuning issue of MPC parameters due to conventional methods, such as trial and error or designer experience. The BIA is adopted to explore the best parameters of MPC based on the minimization of various time domain objective functions. The suggested aircraft model takes into account the aircraft dynamics and constraints. The nonlinear dynamics of aircraft, gust disturbance, parameters uncertainty and environment variations are considered the main issues against the control of aircraft to provide a good flight performance. The nonlinear autoregressive moving average (NARMA-L2) controller and proportional integral (PI) controller are suggested for aircraft control in order to evaluate the effectiveness of the proposed MPC based on BIA. The proposed MPC based on BIA and suggested controllers are evaluated against various criteria and functions to prove the effectiveness of MPC based on BIA. The results confirm that the accomplishment of the suggested BIA-based MPC is outstanding to the NARMA-L2 and traditional PI controllers according to the cross-correlation criteria, integral time absolute error (ITAE), system overshoot, response settling time, and system robustness. [ABSTRACT FROM AUTHOR]

Landing a helicopter to the ship flight deck is most demanding even for the most experienced pilots and modeling and simulation of the ship-helicopter dynamic interface is a substantially challenging technical problem. In this paper, a coupling numerical method was developed to simulate the fully coupled ship-helicopter flow-field under complete wind-over-deck conditions. The steady actuator disk model based on the momentum source approach and the resolved blade method based on the moving overset mesh method were employed to model the rotor. Two different ship-helicopter combinations were studied. The helicopter flight mechanics model was established and then the influences of coupled airwake on the helicopter were analyzed. Finally, based on the derived rejection criterion of safe landing and the developed numerical method, the flight envelopes for these two ship-helicopter combinations were predicted. The steady actuator disk model was found to be effective in the study of helicopter operations in the shipboard environment. The calculated flight envelopes indicate that an appropriate wind direction angle is beneficial to increasing the allowable maximum wind speed and the operating boundary is affected by the rotation direction of the main rotor. [ABSTRACT FROM AUTHOR]

The science education literature is littered with “new”, “correct”, “novel”, “explanations”, “theories”, and “approaches” to aerodynamic lift. One might infer from reading the growing number of these articles that there is a fundamental gap in classical physics, where our scientific prowess has failed us. In fact, if you read popular sources, you would believe “no one can explain why planes stay in the air”. This is a disconcerting thought to have while sitting inside a modern engineering marvel provided by Boeing or Airbus. However, rationally, since you are sat in that fuel-efficient and safe aeronautical wonder, the logical conclusion is that some are obviously aware of why planes stay in the air. In this paper, a century of educational literature on the topic of aerodynamic lift and flight is presented. The body of literature encompasses 140 articles, commencing in 1920. It is obvious from the content contained within them that there is more of a misunderstanding rather than an understanding of flight in the education context. There are two paradigms treated as mutually exclusive: those using Bernoulli and those using Newton. Throughout the literature, there are gems lost in the rubble; if the reader does not have an understanding, how will they know what is worth reading? This review attempts to clarify what is worth reading, by presenting a qualitative overview of aerodynamics education in undergraduate engineering, to understand why these opposing camps exist in the literature.

We present a method for numerical simulations of a maneuvering aircraft, which uses a first-order unsteady panel method as the only source of aerodynamic forces and moments. By using the proposed method, it is possible to simulate a motion of an aircraft, while the only required inputs are geometry and inertia characteristics, which significantly reduces the time required to start the simulation. We validated the method by a comparison of recordings of flight parameters (position, velocities, accelerations) from an actual aerobatic flight of a glider and the results obtained from the simulations. The simulation was controlled by deflections of control surfaces recorded during the actual flight. We found a reasonable agreement between the experimental data and the simulation. The design of our method allows to evaluate not only the integral kinematic quantities but also instant local pressure and inertia loads. This makes our method useful also for a load evaluation of an aircraft. A significant advantage of the proposed method is that only an ordinary workstation computer is required to perform the simulation.

In this work, a comparison of potential flight control methodologies for Neptune aerocapture trajectories is presented. Lifting trajectories pertaining to bank angle modulation and direct force control as well as ballistic trajectories pertaining to continuously-variable drag modulation are investigated. A parametric study of vehicle configurations is explored to quantitatively compare the flight envelope between lifting and ballistic trajectories. A closed-loop numerical predictor–corrector aerocapture guidance architecture is utilized to unify each flight control technique for trajectory comparisons. A series of Monte Carlo simulations of blunt body Neptune aerocapture trajectories are conducted to assess each flight control's robustness to uncertainties in vehicle aerodynamics, atmospheric knowledge, and entry state. Direct force control can achieve 100% successful science orbit insertion within a 120 m/s total Δ V budget. Bank angle modulation can achieve 100% successful science orbit insertion within a 300 m/s total Δ V budget. Continuously-variable drag modulation can achieve 99.3% successful science orbit insertion within a 190 m/s total Δ V budget but at 3 times lower peak stagnation point convective heating rate. • Qualitative comparison between lifting and ballistic aerocapture trajectories. • Modular aerocapture guidance architecture developed for quantitative simulations. • Direct force control, bank angle modulation, and drag modulation flight controls. • For Neptune, direct force control provides best orbit insertion. • For Neptune, drag modulation can reduce aerodynamic heating by a factor of 3. [ABSTRACT FROM AUTHOR]

This paper discusses analytical method for realization of preliminary missile stability design calculations. Action has been taken to estimate influence of replacing massive blocks of analogue electronics with compact solutions of digital electronics in missiles remaining in operation. On an example of a short-range 9M33M3 missile from 9K33 „OSA” set and its previously analysed aerodynamic characteristics, the analysis of the centre of gravity location impact was carried out to determine maximum loads occurring in the two most interesting phases of flight: after booster engine burnout and directly after cruise engine burnout. The suggestion for modification suggestion of flight parameters’ optimization is presented which defines stability and its critical impact of these parameters on aeronautical engineering. For the tested missile, the methodology suggestions for the modification is discussed with the comparison of serially produced copies to define the ability of improving the flight parameters. The paper includes visualizations and quantity analysis of: maximal loads on the fuselage, minimal turn radius, and control wing inclination angle as missile’s angle of attack function.

When a hovering hummingbird performs a rapid escape manoeuvre in response to a perceived threat from the front side, its body may go through simultaneous pitch, yaw and roll rotations. In this study, we examined the inertial coupling of the three-axis body rotations and its effect on the flight mechanics of the manoeuvre using analyses of high-speed videos as well as high-fidelity computational modelling of the aerodynamics and inertial forces. We found that while a bird's pitch-up was occurring, inertial coupling between yaw and roll helped slow down and terminate the pitch, thus serving as a passive control mechanism for the manoeuvre. Furthermore, an inertial coupling between pitch-up and roll can help accelerate yaw before the roll-yaw coupling. Different from the aerodynamic mechanisms that aircraft and animal flyers typically rely on for flight control, we hypothesize that inertial coupling is a built-in mechanism in the flight mechanics of hummingbirds that helps them achieve superb aerial agility.

Most aeronautical accidents happen during takeoff and landing. The main objective when studying those phases of the flight mission is to answer a seemingly simple questions: can the airplane safely takeoff and land on the stipulated runway dimensions with the intended weight? The main objective of the present paper is to obtain new analytical answer to those questions, for fixed wing airplanes. To our present knowledge such a solution, with the degree of generalisation proposed here, is new in the literature. Regarding previous studies, first a new power unit traction equation is employed to explicitly consider the influence of air density, angular velocity and diameter of the propeller. Then a new method for calculating the maximum weight is proposed. Next, the use of breaks is modeled and analysed and an equation to calculate the static gliding wind velocity is proposed. Finally, a toolbox created to perform the calculations is described. A thorough analysis of the influence of the airplane design parameters on the behavior of the motion equations is made, with special attention to the use of brakes. Numerical results are successfully compared with experimental data from two models of a commercial airplane, the Cessna 172 Skyhawk models N and S, and four UAV prototypes. The methodology employed uses simple laws of classical mechanics allied to basic calculus and is easy to understand by first year students of physics, engineering or mathematics.

Most aeronautical accidents happen during takeoff and landing. The main objective when studying those phases of the flight mission is to answer a seemingly simple questions: can the airplane safely takeoff and land on the stipulated runway dimensions with the intended weight? The main objective of the present paper is to obtain new analytical answer to those questions, for fixed wing airplanes. To our present knowledge such a solution, with the degree of generalisation proposed here, is new in the literature. Regarding previous studies, first a new power unit traction equation is employed to explicitly consider the influence of air density, angular velocity and diameter of the propeller. Then a new method for calculating the maximum weight is proposed. Next, the use of breaks is modeled and analysed and an equation to calculate the static gliding wind velocity is proposed. Finally, a toolbox created to perform the calculations is described. A thorough analysis of the influence of the airplane design parameters on the behavior of the motion equations is made, with special attention to the use of brakes. Numerical results are successfully compared with experimental data from two models of a commercial airplane, the Cessna 172 Skyhawk models N and S, and four UAV prototypes. The methodology employed uses simple laws of classical mechanics allied to basic calculus and is easy to understand by first year students of physics, engineering or mathematics. [ABSTRACT FROM AUTHOR]

Unmanned vehicles/systems (UVs/USs) technology has exploded in recent years. Unmanned vehicles are operated in the air, on the ground, or on/in the water. Unmanned vehicles play a more significant role in many civil application domains, such as remote sensing, surveillance, precision agriculture and rescue operations rather than manned systems. Unmanned vehicles outperform manned systems in terms of mission safety and operational costs. Unmanned aerial vehicles (UAVs) are widely utilized in the civil infrastructure because of their low maintenance costs, ease of deployment, hovering capability, and excellent mobility. The UAVs can gather photographs faster and more accurately than satellite imagery, allowing for more prompt assessment. This study provides a comprehensive overview of UAV civil applications, including classification and requirements. Also encompassed with research trends, critical civil challenges, and future insights on how UAVs with artificial intelligence (smart AI). Furthermore, this paper discusses the specifications of several drone models and simulators. According to the literature review, precision agriculture is one of the civil applications of smart UAVs. Unmanned aerial vehicles aid in the detection of weeds, crop management, and the identification of plant diseases, among other issues, paving the path for researchers to create drone applications in the future.

In this paper, analytical expressions for cycle-averaged aerodynamic forces generated by flapping wings are derived using a force model and flapping kinematics suitable for the forward flight of avian creatures. A strip theory-based formulation is proposed and the analytical expressions are found as functions of the amplitude of twist profile, mean twist angle, the flow separation point on the upper surfaces of the wings, and Strouhal number. Numerical results are obtained for a rectangular planform as well as for a representative avian wing planform. Utilizing these results, it is shown that there exists a narrow Strouhal number range where cycle-averaged net thrust, lift, and lift to drag ratio are optimal for a given flow pattern over the upper surfaces of the wings. This narrow Strouhal number range, found to be between 0.1 and 0.3, corresponds to the cruising range for a large number of avian creatures, as documented in current literature. An explanation, based on force constraints and local optimization in aerodynamic force generation, is provided for the unique range of Strouhal numbers utilized in avian cruising flight. The results and the approach outlined in the paper can be utilized to design efficient bio-inspired flapping vehicles. [ABSTRACT FROM AUTHOR]

The flight mechanical model of tilt-rotor UAV is the basis of designing flight control rate and analyzing flight characteristics.Based on the engineering reality, the nonlinear flight mechanics model of a new configuration tilt-rotor UAV is set up.Features and advantages of the new type rotor-craft are analyzed compared with the traditional tilt-rotor.The flight dynamics models of helicopter mode, conversion mode and airplane mode are developed.Based on the flight mechanics model, taking helicopter mode for example, trim and stability are analyzed for different flight speed.The calculate results show that, this configuration tilting rotor has good lateral and directional stability in helicopter mode.The lateral and longitudinal coupling of helicopter hover mode is nearly little.

Within an enclosed shooting range of the EMJOT company, the process of firing one hundred single bullets from a Glauberyt machine pistol was recorded. The empirical test used 9x19 mm FMJ Luger (Parabellum) ammunition manufactured in the Czech Republic in 2017. As the weapon is dedicated to special forces, the shots were fired by an anti-terrorist operative, at a target located 25 m away. In order to determine bullet dispersion, the results of the experiment were subjected to statistical processing. Mean displacement and mean square displacement relative to the mean hit point, histograms, normal distribution, as well as statistical tests and hypotheses were used for estimation. The shots were recorded with a high speed digital camera Phantom v 9.1. The videos recorded were used to determine the initial kinematic parameters of the bullet trajectory.

Landing a helicopter to the ship flight deck is most demanding even for the most experienced pilots and modeling and simulation of the ship-helicopter dynamic interface is a substantially challenging technical problem. In this paper, a coupling numerical method was developed to simulate the fully coupled ship-helicopter flow-field under complete wind-over-deck conditions. The steady actuator disk model based on the momentum source approach and the resolved blade method based on the moving overset mesh method were employed to model the rotor. Two different ship-helicopter combinations were studied. The helicopter flight mechanics model was established and then the influences of coupled airwake on the helicopter were analyzed. Finally, based on the derived rejection criterion of safe landing and the developed numerical method, the flight envelopes for these two ship-helicopter combinations were predicted. The steady actuator disk model was found to be effective in the study of helicopter operations in the shipboard environment. The calculated flight envelopes indicate that an appropriate wind direction angle is beneficial to increasing the allowable maximum wind speed and the operating boundary is affected by the rotation direction of the main rotor.

Many migratory animals travel in large social groups. Large, avian migrants that fly in V‐formations were proposed do so for energy saving by the use of up‐wash by following individuals and regularly change leadership. As groups have been rather homogeneous in previous work, we aimed to explore leadership and its flight mechanics consequences in an extremely heterogeneous case of social migration, namely in spring migration of goose families. In families the experience of group members differs strongly and inclusive fitness may be important. We successfully collected overlapping spring migration tracking data of a complete family of greater white‐fronted geese Anser a. albifrons and extracted leadership, flapping frequency and wind conditions in flight. Our data revealed V‐formations where one parent was flying in front at all times. Although the father led the family group most of the time, he did not flap at higher frequency while doing so. In contrast, the mother flapped faster when leading, possibly because she experienced less supportive wind conditions than when the father led. We argue that in heterogeneous, social groups leadership might be fixed and not costly if supportive environmental conditions like wind can be used. [ABSTRACT FROM AUTHOR]