Aerospace Engineering

This paper introduces a class of Monte Carlo algorithms which are based upon the simulation of a Markov process whose quasi-stationary distribution coincides with a distribution of interest. This differs fundamentally from, say, current Markov chain Monte Carlo methods which simulate a Markov chain whose stationary distribution is the target. We show how to approximate distributions of interest by carefully combining sequential Monte Carlo methods with methodology for the exact simulation of diffusions. The methodology introduced here is particularly promising in that it is applicable to the same class of problems as gradient based Markov chain Monte Carlo algorithms but entirely circumvents the need to conduct Metropolis-Hastings type accept/reject steps whilst retaining exactness: the paper gives theoretical guarantees ensuring the algorithm has the correct limiting target distribution. Furthermore, this methodology is highly amenable to big data problems. By employing a modification to existing naïve sub-sampling and control variate techniques it is possible to obtain an algorithm which is still exact but has sub-linear iterative cost as a function of data size.

Conventional Fowler–Nordheim theory assumes that the emitter is planar, while most tips used in practice have curved emitting surfaces. Using a revised potential distribution, standard image theory and a dimensionless parameter x, we express the experimental current as a multiple σ of the current calculated using standard free-electron supply. A plot of σ(x) for one carbon emitter shows a maximum at a value of x corresponding to the known emitter radius. The calculated field strength at the emitter surface varies little with x. The values found for σ are sensitive to the accuracy of calculation and, to test the theory further, it is desirable both to improve the modelling of image effects and to obtain measurements of current–voltage characteristics and emitting radii together for more types of emitter.

A general methodology for estimating the requirements for defeating an explosive-containing mortar threat by an intercepting array of explosively generated natural and controlled fragments is discussed along with the experimental data supporting quantitative interpretation. The target response of covered TNT impacted by single fragments is predicted through numerically determined shock-to-detonation thresholds as well as empirical penetration equations. Included in the methodology is a comprehensive, deterministic endgame model that consists of an intercept model, a static and dynamic fragment model, and a hit model generating the number of effective hits for arbitrary intercept situations. Experimental data supporting the assumptions of the models are reported. The model is also useful in establishing interceptor requirements.

Stress analysis on a beam for hat cross-section with fixed ends was done. Only top and lower flanges were fixed without fixing the web, statically making the ends fixed. It was found that stress at edges was far superior to that at the middle for a uniformly distributed loaded beam. This paper presents a FEA study for reducing the stress at the beam ends by providing simple support along with fixed flanges. The simple support is provided at the lower flanges of hat cross-section beam. The support length was varied along the length of beam at both the ends. Optimized length of flange was found for minimized stress in the beam.

The initial development of negatively buoyant jets has been investigated experimental and numerically, more specifically the role played by gravity in the development of the leading vortex ring. A classical pistoncylinder arrangement has been used to produce the negatively buoyant jets. Under the experimental conditions considered in this work, the Froude number, Fr, which compares the jet momentum and the buoyancy flux is the most important parameter characterizing the dynamics of the flow. When the value of this parameter is sufficiently small the initial vortex ring generated at the start of the motion is pushed upwards by the gravity force before it can entrain enough vorticity to acquire a self induced velocity. However when the Froude number exceeds a critical value, Frc ∼ 1, the vortex ring can travel downwards and entrainins vorticity from the trailing jet during a longer time. Total and vortex circulation, as well as the trajectory of the leading vortex have been measured to clarify the effect of gravity on the distribution of vorticity during the initial development of negatively buoyant jets.

Aerodynamic parameters have a huge impact on the trajectory of a projectile which in turn results in its range and accuracy. The influence aerodynamic parameters for the estimation of trajectory elements are drag Coefficients, lift Coefficients, angles of attack, muzzle velocity, atmospheric conditions, and the projectile shape and size. Thus proper methods for determining the drag and lift forces of the projectile is very important. The trajectory of a projectile through the air is affected both by gravity and by aerodynamic forces. In this paper 57 mm and 37 mm anti aircraft projectile was considered for the analysis. Here main emphasis was given to determine pressure coefficient, Drag coefficients, lift coefficient of the projectiles at different angle of attack. To study the aerodynamic parameters the experiment was conducted in an open circuit subsonic wind tunnel where uniform flow velocity is maintained across the flow direction. For the experiment varied angles of the attack was considered. Here inclined manometer was used to find out the surface static pressure and the pressure coefficient was determined from that. Then the drag & lift forces and their coefficients was determined. Finally, for the computational analysis, the ANSYS Software was used to simulate the experimental data.

In the present paper, the initial theoretical results on wave-like aquatic propulsion of marine craft by propagating flexural waves are reported. Recent experimental investigations of small model boats propelled by propagating flexural waves carried out by the present author and his co-workers demonstrated viability of this type of propulsion as an alternative to a well-known screw propeller. In the attempts of theoretical explanation of the obtained experimental results using the theory of Lighthill for fish locomotion, it was found that this theory predicts zero thrust for such model boats, which is in contradiction with the results of the experiments. One should note in this connection that the theory developed by Lighthill assumes that the amplitudes of propulsive waves created by fish body motion grow from zero on the front (at fish heads) to their maximum values at the tails. This is consistent with fish body motion in nature, but is not compatible with the behaviour of localised flexural waves used for propulsion in the experimental model vessels. To overcome the problem of predicting zero thrust for the above vessels, it is suggested in the present work that nonlinear distortion of localised flexural waves may be responsible for generation of thrust. This hypothesis is explored in the present work by adding nonlinear harmonics of propulsive flexural waves to the formula derived by Lighthill for generated thrust. For simplicity, only the lowest (third) harmonic growing linearly with the distance of propagation was used. The resulting formula for the averaged thrust shows that, due to the effect of the third harmonic, the thrust is no longer zero, thereby demonstrating that nonlinear distortion of the propulsive flexural waves may be paramount for the existence of wave-like aquatic propulsion of small marine craft using freely propagating flexural waves.

The whirligig beetle, claimed to be one of the most energy-efficient swimmers in the animal kingdom, has evolved a series of propulsion strategies that may serve as a source of inspiration for the design of propulsion mechanisms for energy-efficient surface swimming. In this paper, we introduce a robot platform that was developed to test an energy-efficient propulsion mechanism inspired by the whirligig beetle. A propulsor-body-fluid interaction dynamics model is proposed, and based on this model, the propulsor flexural rigidity and beating patterns are optimized in order to achieve energy-efficient linear swimming and turning. The optimization results indicate that a propulsor with decreasing flexural rigidity enhances vortex shedding and improves thrust generation. It has also been found that an alternating asymmetrical beating sequence and optimal beating frequency of 0.71 Hz improves propulsion efficiency for linear swimming of the robot. The alternating beating of the outboard propulsors and the unfolded inboard propulsors working as brakes results in efficient turning with a smaller turning radius. Both simulation and experimental studies were conducted, and the results illustrate that decreasing flexural rigidity along the propulsor length, an oscillating body motion, and an S-shaped trajectory are critical for energy-efficient propulsion of the robot.

This paper concerns the problem of adequate identification of controlled events in alarm systems. There are two incorrect reactions: non identified event (system does not react) and false alarms. For calculation of these probabilities a new quantitative formulas based on set theory are investigated. There are given calculation examples to illustrate new formulas. A criterion for perfect identification is defined.

This paper concerns the problem of adequate identification of controlled events in alarm systems. There are two incorrect reactions: non identified event (system does not react) and false alarms. For calculation of these probabilities a new quantitative formulas based on set theory are investigated. There are given calculation examples to illustrate new formulas. A criterion for perfect identification is defined.

The study of course leadership in higher education focusses on an understudied area of research, with a limited number of publications discussing the role of the course leader in higher education, and a distinct lack of research on how course leaders in higher education undertake their professional practice. This lack of a pre-existing theory points the researcher towards grounded theory to investigate and generate a new theory on course leaders' experiences. Since leadership, and therefore course leadership, is an inherent complex social process, selection of grounded theory as a research methodology to explain how course leaders in higher education practice seems a logical choice. Grounded theory has been successfully used to investigate phenomena in education and in leadership practice in other disciplines. We therefore argue that grounded theory is an appropriate selection for research in education and higher education settings for areas of research where no theory currently exists. Moreover, grounded theories focussing on professional practice have been published in various contexts demonstrating that it is an appropriate method for investigating course leaders' professional practice. Finally, this paper outlines some perceived weaknesses of using a grounded theory approach for researching course leadership, and offers means to navigate these.

The paper presents the first part of a dynamic study for a car's rear axle assembly, respective a modal analyze. The axle has a twistable beam, and the assembly has been studied considering all its parts, even the elastic elements that attach it on the body. The FEM was used as study method, and the calculation software was MSC/NASTRAN. Keywords Rear axle, modal analyze, FEM (Finite Elements Method).

The aerodynamic performance of an aircraft can be enhanced by incorporating wingtip devices, or winglets, which primarily reduce lift-induced drag created by wingtip vortices. This study outlines an optimization procedure for implementing winglets on a Class I fixed-wing mini-UAV to maximize aerodynamic efficiency and performance. After the Conceptual and Preliminary design phases, a baseline UAV was developed without winglets, adhering to specific layout constraints (e.g., wingspan, length). Various winglet designs-plate and blended types with differing heights, cant angles, and sweep angles-were then created and assessed. A Computational Fluid Dynamics (CFD) analysis was conducted to evaluate the flow around both the winglet-free UAV and configurations with each winglet design. The simulations employed Reynolds-Averaged Navier-Stokes (RANS) equations coupled with the Spalart-Allmaras turbulence model, targeting the optimal winglet configuration for enhanced aerodynamic characteristics during cruise. Charts of lift, drag, pitching moment coefficients, and lift-to-drag ratios are presented, alongside flow contours illustrating vortex characteristics for both baseline and optimized configurations. Additionally, dynamic stability analyses examined how winglets impact the UAV's stability and control. The results demonstrated a significant improvement in aerodynamic coefficients (C Lmax , L/D max , C La , C ma), leading to an increase in both range and endurance.

One of the principal objectives of vibration isolation technology is to isolate sensitive equipment from a vibrating structure or to isolate the structure from an uncertain exogenous disturbance source. In this paper, a dynamic observer-based active isolator is proposed that guarantees closed-loop asymptotic stabil- ity and disturbance decoupling between the vibrating structure and isolated structure. The proposed active isolator is applied to a uniaxial vibrational system and compared to an optimal linear-quadratic design.

A high voltage switch tube with a central cathode cy lindrically symmetric to and surrounded by a tubular anode, with a grid interposed between the cathode and anode. A high negative voltage is applied to the cath ode, but the flow of electrons to the anode is blocked by the grid which is held near cathode potential. After a space charge is created at the grid by electrons from the cathode, the grid is pulsed to ground potential, releasing electrons from the cathode to yield a very high current pulse. The cathode is preferably a graphite foam sleeve mounted on a support structure.

In the context of the COVID-19 prevention this article proposes an upgrade of a reliable method to detect in several conditions the wearing mask in some critical places. This paper contains the new innovative option which we added to the elevator prototype system the masked Face Recognition. This makes face recognition a very difficult task since certain parts of the face are hidden, we propose a reliable method based on discard masked region and deep learning-based features to address the problem of the masked face recognition process. This article presents the improvement works carried out in the operation of an elevator to improve the rate of prevention of covid, by proposing a study case of a microcomputerbased elevator system prototype, using DC motor, gear, controller circuit etc., that carries out an experimental implementation with the simulation software. In otherwise, a thermal detection system is implemented to react in case of detection of abnormal temperature and save this information in a database.

1 i FDM-A 2 a analogicznymi etapami w zjawiskach przesyłu informacji w radiotechnice. We wszystkich tych przypadkach odbywa się modulacja, transmisja i demodulacja FM. Inne są tylko rodzaje przesyłanych informacji: dla sygnału diagnostycznego w metodach FAM-C i FDM-A jest to informacja o stanie technicznym par kinematycznych zespołu napędowego (objawiająca się pewnymi zmodulowaniami prędkości kątowej par kinematycznych), a dla sygnału radiowego jest to mowa (sygnały akustyczne), muzyka lub pewne sekwencje dźwięków. Inne jest również środowisko przenoszenia: transmisja radiowa -w środowisku pośredniczącym pomiędzy nadajnikiem a odbiornikiem (np. powietrze, próżnia, woda), transmisja w metodach FAM-C i FDM-A -poprzez cięgna sztywne zespołu transmisji pomiędzy badanymi parami kinematycznymi a prądnicą. Inny jest również zakres częstotliwości nośnej: dla transmisji radiowej FM częstotliwość nośna wynosi od kilkunastu MHz do setek MHz zaś w metodach FAM-C i FDM-A od kilkudziesięciu Hz do kilku kHz. Także częstotliwości heterodyny 3 różnią się od siebie: w radiotechnice od kilkunastu MHz do setek MHz, w diagnostyce (w zależności od konstrukcji maszyny elektrycznej) od kilkuset Hz do kilku kHz. Słowa kluczowe: diagnostyka techniczna, diagnozowanie traktów przenoszenia napędu, modulacja częstotliwości, zbiór charakterystyczny, silnik turbinowy, łożysko toczne, współczynnik toczenia, heterodyna, odbicie lustrzane. 1 FAM-C -metoda diagnozowania napędów oparta na śledzeniu modulacji częstotliwości (FM -frequency modulation) napięcia wyjściowego prądnic prądu przemiennego (A -od liter AC = alternating current). 2 FDM-A -metoda diagnozowania napędów oparta na śledzeniu modulacji częstotliwościowej (FM -frequency modulation) dla pulsacji napięcia wyjściowego prądnic prądu stałego (D -od liter DC = direct current). 3 Heterodyna -generator wewnętrzny o zmienianej częstotliwości w celu uzyskania po zmieszaniu z częstotliwością nośną odbieranego sygnału częstotliwości pośredniej. Dla odbiorników pracujących w oparciu o modulację częstotliwości wartość częstotliwości pośredniej wynosi 10,7 MHz.

The emergence of Industry 4.0, characterized by the fusion of cutting-edge technology and digitization, has significantly altered the automotive industry. Automation, data interchange, and digital technology are combined in Industry 4.0 to produce a more productive and adaptable production environment. This technological advancement is not without its difficulties, such as a call for improvement on cybersecurity to prevent online attacks, up skilling and reskilling of industry employees to ensure high level of competencies, to mention a few. The auto industry is moving toward a new paradigm of connected vehicles and intelligent mobility options outside of the production environment thanks to Industry 4.0. With the integration of (IoT) the Internet of Things, cars have become sophisticated devices that can gather, process, and communicate enormous amounts of data. Sensors placed throughout the vehicle provide real-time monitoring of performance, external conditions, and driver behaviour. This increases safety protections, maximizes fuel efficiency, and paves the road for preventative maintenance. This study aims at developing a workforce framework that will help increase organizational effectiveness within the industry 4.0 paradigm. It also provides recent views on the development of the automobile industry due to Industry 4.0 incorporation, the perceived and current difficulties and possible solutions to identified challenges.

This paper proposes a smooth-trajectory estimator for the labelled multi-Bernoulli (LMB) filter by exploiting the special structure of the generalised labelled multi-Bernoulli (GLMB) filter. We devise a simple and intuitive approach to store the best association map when approximating the GLMB random finite set (RFS) to the LMB RFS. In particular, we construct a smooth-trajectory estimator (i.e., an estimator over the entire trajectories of labelled estimates) for the LMB filter based on the history of the best association map and all of the measurements up to the current time. Experimental results under two challenging scenarios demonstrate significant tracking accuracy improvements with negligible additional computational time compared to the conventional LMB filter. The source code is publicly available at , aimed at promoting advancements in MOT algorithms.

Many of the currently planned astronomy missions will go into orbits around the L 2 libration point in the Sun-Earth system. Two ESA projects at L 2 , GAIA (2012) and DARWIN (2016) will use a Soyuz launch from the currently constructed launch facility at Kourou. Soyuz will launch into a low circular parking orbit from which the Fregat upper stage will inject to the transfer. The nearly parabolic transfer orbits can be reached at inclinations of up to 30 • with little mass penalty compared to low inclination orbits. This allows to reach a Lissajous orbit with a maximum Sun-spacecraft-Earth angle of 15 • (GAIA baseline) with an insertion maneuver of less than 130 m/s for a full year launch window. Or by selecting the parking orbit near the lunar orbit plane, a lunar gravity assist can be used to reach the stable manifold of an even smaller amplitude (e.g. 7 • ) Lissajous orbit without any deterministic maneuver during the transfer. Another interesting case of transfers to orbits around L 2 has been studied for the DARWIN mission. DARWIN consists of four spacecraft. One studied option is to launch them in pairs, on two Soyuz launches from Kourou. The launch dates have to be at least 20 days apart, but the spacecraft have to rendezvous in an orbit around L 2 . It has been shown that without any phasing orbits for a given separation of the launch dates of up to 60 days, a target orbit can be defined in which the two stacks of spacecraft can be brought to the same position with a small V .

The paper presents a comparison of the dissipation rate obtained from numerical differentiation of the time-resolved velocity, analog differentiation of the hot-wire signal, integration of the velocity derivative spectra obtained from the velocity spectra, and the application of a power decay law. Hot-wire measurements downstream of an active-grid provide the timeresolved velocity with a Taylor Reynolds number in the range of 200-470, turbulence intensities in the range of 5.8-11%, and nominal mean velocities of 4, 6, and 8 m s -1 . The dissipation rate calculated using a ninth-order central-difference scheme differs at most by ± 4% from the value obtained by analog differentiation. For comparison, a 23rd-order central-difference scheme offers negligible (0.02%) difference relative to the ninth-order scheme. Correction for an apparent uncertainty in the calibration of the analog differentiator reduces the difference to ± 2.5%. In contrast, integration of the velocity derivative spectra obtained from the velocity spectra leads to a dissipation rate 14-45% larger than the corresponding values obtained using analog differentiation. Results obtained from the application of a power decay law of turbulence kinetic energy with a nonzero virtual origin to determine the dissipation rate deviate by 1.7%, 1.6%, and 3.6% relative to the corresponding values obtained from the analog differentiator based on the ensemble average of downstream locations with a ±5.6% scatter about the ensemble average.

This paper examines the tracing of the trajectories of weak waves behind a shock wave induced flow in order to establish how the domain shape influences the flow both from a spatial and temporal perspective. The basic principle is that if a particle produces a series of point disturbances in a flow field the perturbations induced will propagate outwards at the local sonic velocity whilst at the same time being convected along with the local flow velocity. A number of issues may be identified for an unsteady flow. Firstly the flow field at later times may be influenced by perturbations produced at earlier times. Secondly, if the positions of the perturbations can be monitored as a function of time then the trajectory and velocity of the particle may be deduced. Thirdly, if a perturbation arises from a point on a boundary then its influence, if any, on any particular part of the flow can be established.

A predominantly experimental investigation into the nature of transonic flow within an aerodynamic corner is treated. The work focuses on exploring the shock-induced separation that can occur due to the corner. Effects of dihedral angle, and sharp and filleted 90 o corners were studied on a RAE2822 profile wing. Tests were conducted in a shock tube operating as a short-duration transonic tunnel, using oil-film surface flow visualisation techniques. The experimental results are compared to numerical simulation studies. The CFD results correlate well with the experiments. It is shown that a fillet radius disperses the region of separated and reversed flow outwardly from the centre of the corner. Increasing the dihedral angle of the corner significantly delays and weakens the separated region.

In the reflection of shock waves off a surface von Neumann’s theory assumes compressible and inviscid flow. It also assumes the reflecting surface to be perfectly smooth, nonporous, and adiabatic. It is found to be accurate for a wide range of regular reflection patterns and limited to very strong shocks in the case of Mach reflection. However experiments have shown that regular reflection persists beyond the theoretical limit. It has been postulated that this is due to the development of a viscous boundary layer behind the reflection point, an explanation now well accepted. However, the assumption of an adiabatic wall has persisted over many years. An experiment has been devised where two inclined surfaces on either side of a symmetry plane and impacted by a propagating shock wave normal to the plane would show any differences in reflection behaviour, if they were equally smooth but of different conductivities. Tests were conducted at incident shock Mach numbers from 1.30 to 1.59, ...

This paper examines the tracing of the trajectories of weak waves behind a shock wave induced flow in order to establish how the domain shape influences the flow both from a spatial and temporal perspective. The basic principle is that if a particle produces a series of point disturbances in a flow field the perturbations induced will propagate outwards at the local sonic velocity whilst at the same time being convected along with the local flow velocity. A number of issues may be identified for an unsteady flow. Firstly the flow field at later times may be influenced by perturbations produced at earlier times. Secondly, if the positions of the perturbations can be monitored as a function of time then the trajectory and velocity of the particle may be deduced. Thirdly, if a perturbation arises from a point on a boundary then its influence, if any, on any particular part of the flow can be established.

A number of high order accurate direct numerical simulation (DNS) calculations of a Mach 1.5 shock diffracting over a 30 • convex wall were completed. In all cases the same mesh was used and only the Reynolds number varied from Re = 20 000, 50 000, 100 000, 200 000 and 400 000. An examination of the velocity profiles at two locations on the wall showed that all the computations were resolved in the boundary layer along the lower wall of the domain. Schlieren images of the computational results showed no significant change in the results between the Re = 100 000 and Re = 200 000 cases but did show a degradation in flow feature resolution at the shear layer for the Re = 400 000 case. This was attributed to the mesh being too coarse locally for the high Reynolds number. While it is not currently practicable to perform DNS at the same Reynolds numbers as experiments, it is possible to get a computational solution at a Reynolds number that can provide an adequate comparison with what is experimentally possible.

In this study, design calculations and calculations of afterburner used in jet engines are presented by evaluating the results of analytical and computational analysis. Afterburner inlet values of 1050 K temperature, 300 kPa pressure and 3.6 kg/s mass flow rate are taken as the design conditions. Maximum length and diameter are 500 mm and 200 mm, respectively, for the sections to be designed as length constraints within the scope of the conceptual design. The tworing vee-gutter has 1.33 cm in diameter and 4.25 cm high. Jet A fuel is assumed to be injected into the core flow (90 degrees) from the spray bars. The spray is mounted in line with the veegutter to optimize the mixing of the flow. Analyses are performed for 4 cm between the spray bar and the vee-gutter. For the study, the GE J79 engine was examined from the literature and taken as a basis for the aerodynamic transition section design. Within the scope of TEKNOFEST 2023 Jet Engine Design Competition, a preliminary design of an afterburner module that can produce 700 pounds of thrust and has a life capacity of 25 hours should be realized in line with the design requirements and constraints. In the light of geometric constraints, one-dimensional combustion calculations of the module are made, and the parts are modelled using the relevant SolidWorks CAD program and these modelled parts are then transferred to ANSYS™ environment and the results and analyses are verified. The afterburner module flow analysis software program ANSYS™ is used to analyse the afterburner operation in both cold operating ranges (i.e. without combustion) using compressible, viscous and standard k-epsilon turbulence model. As a result, the effect of afterburner length on combustion performance is found to be significant. As a result of the calculations, afterburner length is found as 28.14 cm. It is found that the combustion efficiency is 81.5% and the temperature can be increased from 1050 K to 2044 K. The total pressure loss is 14.96% as pressure drop due to the geometric parameters and heat addition. The blockage ratio calculated due to the use of vee-gutter geometry is the most important parameter in the pressure drop. It is found that the jet engine producing 670 lbs (2981 N) of thrust when the afterburner is not working whereas it can provide a significant amount of power increment at the expense of a 50% increase in specific fuel consumption when the afterburner is active as well as providing a 738 lbs (3238 N) with a 10.1% thrust increase. The reason of the enhancement is mainly coming from the mixing effect of the vee-gutter on the flow structure.

tures is generally substantially less than the dimensionality of the data itself. Thus, rather than transmitting the data in its entirety, if the features are extracted on-board and transmitted this can result in a significant amount of compression. without any loss of information. That is, the raw data can be

Submitted for the GEC16 Meeting of The American Physical Society Performance optimization of an EHD thruster: the influence of secondary emission and the electrodes gap. VICTOR H. GRANADOS, PAULO A. SA, University of Porto, MARIO J. PINHEIRO, IST University of Lisbon — We have developed a numerical model to study the performance (thrust, maximum output velocity of the fluid and thrust-to-power ratio) of a single-stage electrohydrodynamic (EHD) thruster with a rod anode and a funnel-like cathode configuration. The electrohydrodynamic processes embody interlocking aspects of non-compressible gas dynamics (Navier-Stokes equations), ionized gas physics, selfconsistent accelerating electric field adequately described by Poisson equation and migration of charged particles in an electric field in the drift-diffusion approximation. We considered the following neutral and ionized nitrogen species as the working media: N, N+, N2, N + 2 , and N + 4 . In order to optimize the thruster performan...

In data-sparse locations, the necessity for the integration of remote sensing and in-situ-based approaches in assessing greenhouse gases cannot be overstressed. Akin other countries in sub-Saharan Africa (SSA), Nigeria is yet to leverage on and fully maximize the potentialities offered by satellite remote sensing in monitoring and assessment of biophysical and ecological change indicators including greenhouse gases. This study was undertaken with the prime motivation of ascertaining the variations of greenhouse gases concentrations in Delta State, Nigeria as well as the correlation between in-situ measurement and satellite remote sensing observation. Datasets comprising carbon monoxide (CO), nitrogen dioxide (NO2) and sulfur dioxide (SO2) and were sourced from the archive of the European Space Agency and field sampling using Aeroqual S500 ambient air analyser. Descriptive statistics, independent Samples t-Test, analysis of variance (ANOVA), Tukey HSD test of multiple comparisons and...

The modeling, control, and dynamic stabilization of long-span suspension bridges are considered. By employing leading- and trailing-edge flaps in combination, we show that the critical wind speeds for flutter and torsional divergence can be increased significantly. The relatively less well known aerodynamic properties of leading-edge flaps will be studied in detail prior to their utilization in aeroelastic stability and control system design studies. The optimal approximation of the classical Theodorsen circulation function will be studied as part of the bridge section model building exercise. While a wide variety of control systems is possible, we focus on compensation schemes that can be implemented using passive mechanical components such as springs, dampers, gearboxes, and levers. A single-loop control system that controls the leading- and trailing-edge flaps by sensing the main deck pitch angle is investigated. The key finding is that the critical wind speeds for flutter and to...

In this paper, investigation was made into the design, experiment, and aerodynamic analysis of a novel flapping wing rotor applicable to micro aerial vehicles (MAV). Attention was firstly focused on the design of a simple, reliable and lightweight flapping rotor configuration and wing structure to meet the challenging demands for high mechanical and power efficiency and vertical take-off and landing (VTOL) capability of an MAV. The experimental work demonstrated the feasibility and effectiveness of the innovative design. The paper presents an approach of experiment and processing the measured flapping wing total dynamic forces to extract the unsteady aerodynamic force. A potential-flow-based method, unsteady panel method was used to calculate the lift created by flapping wing system. As the method is two dimensional, strip theory is adopted to evaluate the aerodynamics of three dimensional flapping wings. Compared with measured data, the numerical results show good agreement with the first order lift component, which is caused by the rigid wing.

The present paper discusses the advantages and disadvantages of the one-week Concurrent Engineering (CE) study approach applied currently in the Concurrent Engineering Faciliry (CEF) at DLR which has been operating since early 2009. Up to now, ca. 20 condensed studies have been performed at the DLR CEF. This paper compares this approach to the more stretched process, applied e. g. at ESA ESTEC's Concurrent Design Facility (CDF). The investigation takes into account the different space systems to be designed, the goals of the studies and the involved personnel, including both internal and external team members. In summary, this paper describes the last three years of CE at DLR, focussing on the mainly applied approach within different feasibility and preliminary design studies.

The vulnerability of space qualified fuel pipes and heat pipes to hypervelocity impacts has been assessed. The equipment has been placed behind representative spacecraft structure walls and operated at simulated conditions (i. e. carrying pressurized water or N 2 gas). Several failure modes have been investigated, of which perforation has emerged as the most critical. Ballistic limit curves for failure mode "perforation" are presented and compared against the test results. Impact induced overpressure has been investigated. Impacts on structure walls at velocities below 7 km/s can generate highly inhomogeneous fragment clouds. When the equipment located behind the structure wall is laterally confined, the existing approach for determining the failure probability (perforation / no perforation limit) strongly underpredicts its vulnerability. An approach to deal with failure probability in this case is presented.

To analyze the quantity of space debris and micrometeoroids in space, an innovative in-situ impact detection method has been developed at DLR (German Aerospace Center) in Bremen, Germany. The method, Solar panel based Impact Detector "SOLID", uses solar panels for impact detection. The number of measured impacts depends on the detection area (in this case solar panel area), mission duration and the debris flux (orbit dependent). Since solar panels provide large detection areas, this method allows for the collection of large amounts of data, to be used e.g. for model validation. Furthermore, impact damage can be verified once more to confirm or to refute an impact. Both aspects can significantly improve the quality of model validation by using large amounts of highly reliable data. This paper describes the possibility of utilizing CubeSat solar panels for in-situ space debris and micrometeoroid detection. To evaluate the effectiveness of the SOLID debris sensor, an estimation of currently available total solar panel area of CubeSats was analyzed. The currently available total area of active CubeSats in orbit is estimated to be 6.1 m². This number is compared to the retrieved solar panel areas of the Hubble Space Telescope and the European Retrievable Carrier.

Collisions of spacecraft in orbit with Space Debris (SD) or Micro-Meteoroids (MM) lead to payload degradation, anomalies or failures in spacecraft operation or even to loss of a whole mission. Existing flux models and impact risk assessment tools, like MASTER or ORDEM, PIRAT, ESABASE2 and BUMPER II are used to analyze the mission risk concerning this hazard potential. The validation of the flux models so far is partly based on SD and MM impact data from in-situ impact detectors, e.g. DEBIE, GORID, capture cells and on the analyses of retrieved hardware from space, e.g. LDEF, HST or EURECA. However the knowledge on the small objects populations (millimeter down to micron sized) in space is rather limited and needs to be enhanced for reliable models. As a contribution Deto soft-ware validation in terms of data acquisition, a new type of impact detector is currently under development at DLR. The Solar Generator based Space Debris Impact Detector (SOLID) makes use of spacecraft solar pa...

The International Space Station ISS demonstrates long-term international cooperation between many partner governments as well as significant engineering and programmatic achievement mostly as a compromise of budget, politics, administration and technological feasibility. A paradigm shift to use the ISS more as an Earth observation platform and to more innovation and risk acceptance can be observed in the development of new markets by shifting responsibilities to private entities and broadening research disciplines, demanding faster access by users and including new launcher and experiment facilitator companies. A review of worldwide activities shows that all spacefaring nations are developing their individual programmes for the time after ISS. All partners are basically still interested in LEO and human spaceflight as discussed by the ISECG. ISS follow-on activities should comprise clear scientific and technological objectives combined with the long term view on space exploration. T...

The knowledge of small (>, 100 µm) but abundant objects in space is low. To analyze the quantity of those small objects in Earth orbit is a challenging issue and a number of different methods has been proposed and investigated in the past. However, until today there is no realised solution, which provides sufficient measure-ment data to be used for software validation. To im-prove our knowledge regarding the space environment, a new type of in-situ sensor was developed at DLR in Bremen, Germany. The Solar panel based Impact Detector “SOLID” is a large-area impact sensor that can be placed on a spacecraft in any orbit and can provide measurement data continuously. This paper provides an overview regarding the already performed as well as planned development of the SOLID system. Further-more, the main objectives corresponding the first and second on orbit verification of SOLID on TechnoSat mission (2017) and S²TEP (2019) respectively are out-lined.