Vol.11 by Journal of Aerospace Technology and Management
Journal of Aerospace Technology and Management, 2019
This paper presents a detailed analysis about the implementation of a washout fi lter on the SIVO... more This paper presents a detailed analysis about the implementation of a washout fi lter on the SIVOR (Simulador de Voo Robótico-Robotic Flight Simulator) project. The main objective of this project is to develop, on an anthropomorphic robot, a fl ight simulator which can be used as an Engineering Development System (EDS) and a pilot training platform, capable of providing feelings the pilot would only have in more intensive maneuvers, such as losses/gains of G in aircraft fl ight tests. The SIVOR project also has the objective of providing a cost-effi cient and fl exible tool that can be used during the design phases of aircrafts. One of the demanded features of such simulator is a representative behavior of its motion system, which is achieved by an adequate implementation of the washout fi lter. To the best knowledge of the authors, there are no works in the literature that present a detailed discussion about the implementation of a classical washout fi lter in such fl ight simulator, especially when the translational channel is used to its limits. Experimental results to support the proposed solutions are presented herein.
Journal of Aerospace Technology and Management, 2019
Optimization is now an established tool for obtaining better solutions in engineering design. Nev... more Optimization is now an established tool for obtaining better solutions in engineering design. Nevertheless, the multiplicity of possible applications and the continuing search for better computational performance has motivated researchers in continuing to propose new methods, as well as improvements on existing ones. Not only optimization has allowed a better exploration of the design space, it also can signifi cantly reduce the time of the design process. In this paper the advantages of using a fully multiobjective and multicase approach for the design of space radiators is presented. The optimization of Amazonia-1 satellite batteries panel thermal design is investigated. Instead of conventional space radiators, in this work an innovative solution considering the fi n as heat absorber is analyzed. The results have shown that there are several viable confi gurations regarding to fi n coating material, heater power consumption and additional mass, and the choice of the appropriate radiator confi guration shall be evaluated based on system impact. The possibility of testing automatically different coatings and sizes for the fi n, allowed by the optimization approach, increased signifi cantly the probability of fi nding viable solutions on the design space.
Journal of Aerospace Technology and Management, 2019
In large-scale natural disasters and military supplies, multiple parafoils are more capable of pe... more In large-scale natural disasters and military supplies, multiple parafoils are more capable of performing actual tasks. The cooperative paths planning for multiple parafoils with different initial positions and headings is an important step in multiple parafoils airdrop, which has to satisfy multiple objectives, namely, parafoils can't collide with each other, parafoils should rendezvous at same target area, most of parafoils need to keep alignment against wind, and planned paths should be in the range of maneuver performance constraints to ensure that every parafoil's path is fl yable. Due to more factors need to be considered, it is more diffi cult to plan paths for multiple parafoils than single parafoil. In this paper an improved genetic algorithm is used to solve the multi-objective cooperative paths planning problem of multiple parafoils system. Parafoils' paths are encoded by real matrix, and the cooperative relationship between parafoils is realized by paths fi tness function. The random single point crossover and Gaussian mutation are introduced to accelerate algorithm convergence rate. Finally, a simulation example is given, simulation results show that proposed method can plan feasible paths for all parafoils, meanwhile, it satisfi es the requirements of anti-collision, rendezvous to target point, and keep alignment against the wind.
Journal of Aerospace Technology and Management, 2019
There are many problems facing aircraft in the air during fl ight, such as lightning strikes and ... more There are many problems facing aircraft in the air during fl ight, such as lightning strikes and ice accumulation on aircraft surfaces. These problems usually reduce aircraft effi ciency and lead to serious accidents and fatalities. However, the current protection systems used to solve these problems of aircraft represent excessive energy usage, a hazard to the environment, and they are generally bulky, heavy and costly. Therefore, there are new conductive composites containing an embedded layer of conductive fi bers such as graphene and carbon nanotube designed to carry lightning currents, in addition to that, there is a new deicing heater element made of graphene nanoribbons fi lms to be used in ice protection systems. This paper presents a review of some problems facing aircraft in the air, such as lightning and ice accumulation on the surfaces of the aircraft and the signifi cant efforts that have been exerted to address and solve these issues. Also, this paper reviews the contribution of composite materials in reducing the weight of the aircraft and fuel consumption as well as increasing the effi ciency of aircraft. This paper also will review the conductive composite materials and its application for aviation, in addition to their contribution to solving the most important problems in aviation.
Journal of Aerospace Technology and Management, 2019
Increased congestion at hub airports affects on-time airline performance to the detriment of cust... more Increased congestion at hub airports affects on-time airline performance to the detriment of customer satisfaction and may have substantially negative repercussions for airlines in a hypercompetitive environment. This paper concentrates on the on-time performance of British Airways (BA) at London Heathrow Airport (LHR) to identify BA's delays/disruption management; measure the passengers' expectations in case of a delay; and investigate the passenger satisfaction levels. A survey of 160 BA passengers based on a close-ended questionnaire was conducted, complemented by semi-structured interviews with four members of staff at BA's network operations department. The survey results show that BA has been able to satisfy its customers by matching or exceeding their expectations and that those customers will travel with BA again.Interestingly, the results contradict the widespread belief that BA passengers are annoyed by a service failure/delay at LHR; this is because they expect to experience such a delay anyway.
Journal of Aerospace Technology and Management, 2019
In the almost dictatorial academic scenario of “publish or perish”, the time elapsed between sub... more In the almost dictatorial academic scenario of “publish or perish”, the time elapsed between submission and final decision has become one of the biggest concerns of authors and their institutions. Although expectations about a new submission are usually high, publication of peer-reviewed articles demands its own time, so that only those which really bring new contributions to the subject area are selected. In fact, this selection is part of an ethical responsibility assumed by everyone involved in scientific publishing, including authors, reviewers, editors, and publishers
Vol.10 by Journal of Aerospace Technology and Management
Journal of Aerospace Technology and Management, 2018
Lately, nanomaterials have been largely studied as reinforcements for epoxy resin. Although their... more Lately, nanomaterials have been largely studied as reinforcements for epoxy resin. Although their usage is highly promising, the literature has reported some drawbacks regarding the improvement of mechanical properties in nanocomposites. These difficulties are usually due to dispersion of nanomaterials and its adhesion to the polymeric matrix. One approach to this problem is the functionalization of nanomaterials such as carbon nanotubes (CNTs) and graphene. In this work, we have studied the synthesis and functionalization process of CNTs and graphene oxide (GO) to be used as reinforcements for epoxy resin nanocomposites. CNTs were synthesized at 850 °C in a quartz furnace, from hexane and ferrocene vapor, and functionalized by acids and ethylenediamine treatments. GO was obtained by graphite exfoliation through a modified Hummer's method. The nanomaterials were characterized by Raman spectrum, FT-IR, XRD, and SEM images. Nanocomposites were prepared using these nanomaterials and evaluated by DMA. While both nanomaterials showed an improvement in mechanical properties, suggesting a chemical bond between nanomaterial and the epoxy matrix, it was clear that GO reinforced samples presented a higher storage modulus.
Journal of Aerospace Technology and Management, 2018
In this study, an efficient methodology is proposed for robust design optimization by using prefe... more In this study, an efficient methodology is proposed for robust design optimization by using preference function and fuzzy logic concepts. In this method, the experience of experts is used as an important source of information during the design optimization process. The case study in this research is wing design optimization of Boeing 747. Optimization problem has two objective functions (wing weight and wing drag) so that they are transformed into new forms of objective functions based on fuzzy preference functions. Design constraints include transformation of fuel tank volume and lift coefficient into new constraints based on fuzzy preference function. The considered uncertainties are cruise velocity and altitude, which Monte Carlo simulation method is used for modeling them. The non-dominated sorting genetic algorithm is used as the optimization algorithm that can generate set of solutions as Pareto frontier. Ultimate distance concept is used for selecting the best solution among Pareto frontier. The results of the probabilistic analysis show that the obtained configuration is less sensitive to uncertainties.
Journal of Aerospace Technology and Management, 2018
This study describes the main regularities for the construction of deployable metal shells of a c... more This study describes the main regularities for the construction of deployable metal shells of a cylindrical type. The comparative analysis of the efficiency of compact folding methods of thin metal shells of cylindrical and conical types, capable of maintaining the initial load-carrying capacity after unfolding without applying the additional strengthening methods, is presented. The range of possible parameters of long-length structures, constructed on the basis of rigid deployable pressurized shells, is characterized. The paper gives the qualitative and quantitative evaluation of basic functional characteristics of folding inflatable metal structures of cylindrical and conical types under the action of a complex of characteristic external loads, close to the maximum allowable ones. The result of experimental operability confirmation of the proposed structures' configurations is presented.
Journal of Aerospace Technology and Management, 2018
The carbon/carbon composite manufacturing processes generally use flammable and toxic precursors.... more The carbon/carbon composite manufacturing processes generally use flammable and toxic precursors. In order to make these processes safer, it is interesting to use less toxic and safer precursors to the environment and people. The present study investigates the types of pyrocarbon resulting from composite carbon/carbon densification produced by the technique of Film Boiling Chemical Vapor Infiltration using as carbon precursors: soybean oil, ethanol and hexane, the latter as control. The microstructure produced was analyzed through SEM techniques, PLOM, XRD and Raman. The pyrocarbons observed are Smooth Laminar, Rought Laminar and Regenerative Laminar types. Soybean oil resulted in porous bodies while other precursors resulted in denser bodies. The crystallites made with ethanol and hexane have preferential growth in the c direction, while those made with soybean oil grow preferentially in a direction.
This study takes a Jacobian-free approach based on the Arnoldi iteration to present a method to p... more This study takes a Jacobian-free approach based on the Arnoldi iteration to present a method to perform hydrodynamic instability analysis based on Direct Numerical Simulations. The method employs high order spatial and temporal discretizations for the flow simulation and has very low requirements of computational time and memory, compared to conventional matrix-forming methods. Details of the numerical treatment applied to guarantee consistency in the numerical solution are discussed, such as mesh and domain dependencies, and buffer zones for the open boundary conditions. The implementation presented here is applicable to any flow with Cartesian geometry, however, the method can be extended to complex geometries and three-dimensional flows.
This work studies the performance and dry mass of the under development LOX/Ethanol L75 liquid ro... more This work studies the performance and dry mass of the under development LOX/Ethanol L75 liquid rocket engine. To this end, an object-oriented program written in C++ was developed. The program is intended to be versatile and easily extensible in order to analyze different configurations of liquid rocket engines. The UML (Unified Modeling Language) tool is used to model the architecture of the codes. UML diagrams help to visualize the code structure and the communication between objects, enabling a high degree of abstraction. The cryogenics Vulcain and HM7B engines power cycles along with the staged-combustion SSME engine perform the verification of the codes. Finally, the influence of changes in design parameters on the performance and dry mass of the L75 rocket engine is analyzed.
The present study investigates the influence of fiber content on thermal properties of short sili... more The present study investigates the influence of fiber content on thermal properties of short silica fiber (SSF) reinforced modified resole resin (MRR) composites. For this purpose, different SSF loading composites were prepared: 40, 55, and 65 wt.%. The ablation resistance related to mass loss parameters was quantified by testing under an oxyacetylene flame up to 2300 °C for 30 s. The thermal conductivity of the composite was studied via experimental steady state technique. Thermal stability of the composite material was estimated by means of thermo-gravimetric analysis (TGA), both in air and nitrogen atmosphere. The ablated composite material was characterized by different techniques (XRD, FTIR, and SEM). The results showed that the back-face surface temperature of SSF/MRR composites follows the typical variation curve, and linear ablation rate, mass ablation rate, and char yield decrease with increasing silica fiber content. This confirms that 55 and 65 wt.% SSF loading exhibited the best anti-ablation performance and the lowest percentage of char yield. XRD and FTIR analysis of the ablated specimen zone showed the absence of new phase. The thermo-gravimetric analysis confirmed the thermal resistance of SSF/MRR composites in comparison with MRR matrix and the decrease of char with increasing SSF loading. The thermal conductivity of these composites was significantly enhanced by the SSF into the modified resole matrix. This thermal conductivity follows both the rule of mixture and Maxwell models. The overall thermal characteristics of the SSF/MRR composites meet most of the necessary high temperature application criteria.
The present study assesses the infl uence of non-metallic constituents and manufacturing paramete... more The present study assesses the infl uence of non-metallic constituents and manufacturing parameters, such as compaction pressure and sintering temperature, to produce a metal matrix composite (MMC) of copper/iron, based on the brake disc of aircraft AT-29 SuperTucano. The samples were produced with six different compositions, by varying the amount of abrasive particles (quartz and zirconia silicate) and the solid lubricant (graphite), with one of the compositions manufactured without the addition of graphite. The compaction pressures were 210 and 420 MPa, with sintering temperatures of 950 °C and 1050 °C in a furnace with controlled atmosphere of argon + 10% H 2. After sintering, the effectiveness of the sintering process was evaluated through the apparent density (Archimedes's method), Brinell and Vickers hardness, and the microstructure by Scanning Electron Microscopy (SEM). The sintering process was severely affected by the solid lubricant (graphite): its reduction resulted in a density increase near 18%, and the hardness of the compound up to 62%. The hardness values demonstrated signifi cant variation with compaction pressure, with a pronounced effect on compounds with less non-metallic elements. SEM analysis demonstrated that not only graphite, but also the ceramic particles affected the sintering process through the agglomeration of inclusions into the metal-metal interface. The samples without graphite exhibited almost the same value of pores after sintering, regardless of the compaction pressure, indicating that the graphite content affects directly the sintering process, regardless of the compaction pressure.
Journal of Aerospace Technology and Management, 2018
GPS-based systems have been widely used in different critical sectors, including civilian and mil... more GPS-based systems have been widely used in different critical sectors, including civilian and military applications. Despite of being able to provide great benefi ts, under certain circumstances they show to be highly vulnerable to intentional interferences. In this context, this article aimed to evaluate the susceptibility of different complex GPS-dependent systems to intentional interferences, focusing on the technique known as spoofi ng. This technique presents a high complexity and a great potential for damaging/deceiving complex systems, besides being diffi cult to identify and to implement countermeasures. Complex systems, like mobile phones, automobile receivers and aircraft receivers were submitted to different levels of spoofi ng, in free space and in a semi-anechoic chamber, being corrupted with low power levels of interference.
Journal of Aerospace Technology and Management, 2018
AbstrAct: This paper presents a one-dimensional model for the analysis of the charring ablative m... more AbstrAct: This paper presents a one-dimensional model for the analysis of the charring ablative materials used in spacecraft thermal protection systems. The numerical method is based on an implicit fi nite difference formulation of the governing equations written for a system of mobile coordinates that accounts for the possible presence of surface recession. The maximum allowable operating temperature for the adhesive layer of the junction between the heat shield and the substructure is used as a design parameter for determining the minimum heat shield thickness. A case study on the re-entry of the Stardust capsule is presented. The model proposed as a useful dimensioning tool for the preliminary design phase of the heat shields of spacecraft entering the atmosphere. The model was validated through a survey of the literature related to the dimensioning of thermal shields, but based on numeric programs of highly representative industrial standards.
vol.9.no.4 by Journal of Aerospace Technology and Management
Journal of Aerospace Technology and Management, 2017
In order to make a sensible prediction on the air traffic flow management with conditions of wave... more In order to make a sensible prediction on the air traffic flow management with conditions of wave-off and bolter, a system dynamic model for the night recovery operations of embarked aircrafts is built to ensure the adaption of air traffic flow with the capacity of air control at each phase of the recovery operations. The model aims at the characteristics of multiple feedbacks, delays and complex time varying, builds a stock flow diagram and operation model with impact factors of the night recovery system, and is simulated in Vensim® Personal Learning Edition 5.9. The simulation shows a reasonable prediction result for the night recovery of embarked aircrafts with conditions of bolter and wave-off and can provide a theoretical basis for scheduling the air traffic flow management of embarked aircrafts formation recovery.
Journal of Aerospace Technology and Management, 2017
The air transport industry in Greece has been experiencing a significant growth. However, higher ... more The air transport industry in Greece has been experiencing a significant growth. However, higher education has missed so far this export opportunity. Public universities and technological educational institutes have very limited undergraduate offerings in the fields of aeronautical engineering and aircraft maintenance technology, respectively. These programs are offered only in the local language, practically restricting them to the indigenous market. Postgraduate offerings are currently inexistent. This study proposes a generic model for undergraduate and postgraduate aviation programs. This model, aligning with the world's best practice in aviation education, would have to be adjusted to meet the Greek aviation industry. A preliminary investigation to identify the characteristics of the model was conducted in the Greek aviation industry, through a survey supported with in-depth interviews. The research findings suggest that it is necessary to invest in the strengths of the Greek aviation industry (aviation services and aircraft maintenance) and the strategic advantages of the country (climate favorable for flight training and touristic attractiveness). The need for a postgraduate aviation program is highlighted, in contrast to the introduction of an undergraduate program, which came up as less desirable. Moreover, the need for export-driven target-oriented synergies between industry and academia has been a key observation.
Journal of Aerospace Technology and Management, 2017
The detection, location, identification and recognition are very important activities for the air... more The detection, location, identification and recognition are very important activities for the air forces. Imaging systems are tools used for those functions, so it is mandatory to characterize those systems to really know their actual operational limits. This paper presents a set of measurements for spectral, radiometric and spatial camera characterization to be applied to imaging systems operating in the thermal infrared. A SC5600 camera manufactured by FLIR® Systems was used and assembled with lenses of 27 or 54 mm equivalent focal length. The camera spectral characterization was done by comparison to a calibrated system composed by thermal source, monochromator and a broadband reference detector. The radiometric characterization was performed using an extensive blackbody (CI Systems) for temperatures between 10 and 55 °C to evaluate the camera accuracy and obtain the calibration curves. The spatial characterization was carried out using the same extensive blackbody and 2 standard USAF 1951 machined targets, one made of steel and other of aluminum, serving as masks for the blackbody. Using recycled material, a homemade extended blackbody for outdoor use was built. The results obtained using the 2 blackbodies in laboratory were similar.
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Vol.11 by Journal of Aerospace Technology and Management
Vol.10 by Journal of Aerospace Technology and Management
vol.9.no.4 by Journal of Aerospace Technology and Management
voltage source, being fed from current, for instance, the
photovoltaic battery. It is shown that LCL-T resonant tank has
intrinsic ability to convert stable AC current into stable AC
voltage thus parametrically regulating output voltage at a fixed
value. This mode of operation is made possible by the use
of active (synchronous) rectifier to recoup energy from the
output back to the LCL-T resonant tank. Basic characteristics
of resonant LCL-T converter regulated by phase shift between
inverter and rectifier regardless of a solar battery current drift
have been defined. It is shown that phase control guarantees
0 voltage and 0 current on switching; however, turn-off
current could be substantial. Calculations and assumptions
made in this study have been confirmed by simulation and
hardware prototype.
of second surface with low absorptivity/emissivity ratio
and negligible degradation in the space environment,
which makes it an excellent coating for thermal control of
satellites. It works as a radiator and is used in particular
parts of the external surfaces of the satellites in order
to reject the undesirable heat to the deep space. In the
Brazilian Space Programs, the radiators of the satellites
are generally painted with special white paints in order to
reject heat instead of the use of optical solar reflector. The
problem of white-ink radiators is the high degradation of the
thermo-optical properties that happen over the useful lives.
Thus, a process of manufacturing and assembly of optical
solar reflector was developed in Brazil. To validate this
process in terms of mechanical and thermal properties, 3
types of optical solar reflector radiators were manufactured,
and their absorptivity and emissivity properties at the
temperature of 23 °C were measured. Optical solar reflector
coupons were mounted on aluminum plates to perform
vibration, thermal vacuum and thermal-shock tests. A study
was also done to optimize the thickness of the glue to fix
the structure of the satellite on the optical solar reflector. It
showed an excellent environmental stability and maintained
and the complex permittivity of a magnetic ceramic material
made of copper, cobalt, and iron oxides. The index of refraction
and the extinction coefficient of the CuCo-ferrite exhibit an
almost frequency independent behavior and were averaged
to n = 3.62 ± 0.05 and k = 0.06 ± 0.02, respectively, over
the frequency range from 0.2 to 1 THz. The corresponding
complex permittivity was ε’ = 13.12 ± 0.35 for the real part
and ε’’ = 0.46 ± 0.15 for the imaginary one. The absorption
coefficient and the transmittance of the CuCo-ferrite were
also determined. The absorption coefficient exhibits a dip
at ~0.35 THz, which corresponds to a peak in transmittance at
this frequency. The impact of the observations on the potential
realization of novel THz electronic devices is discussed.
other physicochemical properties, with major applications in
aeronautical, space, telecommunication, automotive, and medical
areas. This research evaluates electromagnetic properties of
multifunctional composites based on glass fiber woven fabric
pre-impregnated with epoxy resin laminated together carbon
fiber non-woven veil metalized with Ni. In this way, searching
for possible application as radar absorbing structures or
electromagnetic interference shielding structures. The scattering
parameters, in the frequency range of 8.2 to 12.4 GHz, show
that the epoxy resin/glass fiber prepreg allows the transmission
of the electromagnetic waves through its microstructure,
independently of the glass fiber reinforcement orientation
(98% transmission, S24 = −0.09 dB). However, the carbon
fiber/Ni veil shows highly reflector behavior (91% reflection,
S22 = −0.43 dB). Energy dispersive spectroscopy of the veil, before
and after nitric acid attacks, confirmed the Ni coating removal
from the carbon fiber surface. Still, the scattering parameters
show reflector behavior (77% reflection, S22 = −1.13 dB),
attributed to the electrical conductivity of carbon fibers.
Multifunctional composites based on glass fiber/epoxy/carbon
fiber/Ni veil laminates were processed by hot compression
molding. The scattering parameters show that the laminates do
not behave as good radar absorbing structures. Nevertheless,
the laminates present promising results for application as
light weight and low thickness structural composites with
electromagnetic interference shielding effectiveness (91.4%
reflection for 0.36 mm thickness and 100% for ~ 1.1 mm) for
buildings, aircraft, and space components.
behaviour of energetic materials under external thermal stimuli.
Numerical simulation became a powerful tool to reduce the
costs with experimental tests. However, numerical simulations
are not able to predict the violence of thermal response, but
instead accurately reproduce radial heat flow in the test vehicle
and satisfactorily predict the delay time to ignition and ignition
temperature. This paper describes the slow cook-off simulation of
3 selected PBX based on RDX in a small-scale test vehicle, using
the equilibrium equation of Frank-Kaminetskii and testing 2 kinetic
models: Johnson-Mehl-Avrami (n) and Šesták-Berggren (m, n).
The influence of successive addition of binder elements (HTPB,
DOS, and IPDI) on slow cook-off results of selected PBX was
assessed. The variation of ±10% in input data was performed
to determine the influence on the slow cook-off results. Results
showed that the addition of binder elements reduces the delay
time to ignition as well as ignition temperature and that the
Šesták-Berggren (m, n) kinetic model generates smaller values
and with less deviation linked to the variation of input data. The
selection of kinetic model as well as the variation of ±10% in
input data had a negligible influence on the slow cook-off results
of cured PBX.
in studies concerning ionization sensors for aerospace
applications, power generation, and fundamental research.
In aerospace research, they have been used for studies
of shock and detonation waves. Two key features of these
sensors are their short response time, of the order of
microseconds, and the fact that they are activated when
exposed to high temperature air. In this sense, the present
paper describes the development of an ionization sensor
to be used in shock tube facilities. The sensor consists
of 2 thorium-tungsten electrodes insulated by ceramic,
with a stainless steel adapter for proper mounting, as
well as 2 copper seal rings. An electrical circuit was also
built with 2 main purposes: to provide the electrodes
with a sufficient large voltage difference in order to ease
ionization of the air and to assure a short time response
of the sensor. The tests were carried out in a shock tube
with the objective of observing the response of the sensor
under stagnation conditions. For that, we chose initial
driven pressures of 1.0; 1.2 and 1.5 kgf/cm², with a
constant driver pressure equal to 70 kgf/cm². We
analyzed the response of the sensor as a function of
the initial driven pressure, stagnation temperature, and
density. For the studied conditions, the results showed
that the mean amplitude of the ionization sensor signal
varied from 8.29 to 19.70 mV.
nature of flow around airfoil by producing asymmetric Von-
Karman vortex in its wake. Most of the investigations on
Gurney flapped airfoils have modeled the flow using a quasisteady
approach, resulting in time-averaged values with no
information on the unsteady features of the flow. Among
these, some investigations have shown that quasi-steady
approach does a good job on predicting the aerodynamic
coefficients and physics of flow. Previous studies on Gurney
flap have shown that the calculated aerodynamic coefficients
such as lift and drag coefficients from quasi-steady approach
are in good agreement with the time averaged values of these
quantities in time accurate computations. However, these
investigations were conducted in regimes of medium to high
Reynolds numbers where the flow is turbulent. Whether this
is true for the regime of ultra-low Reynolds number is open
to question. Therefore, it is deemed necessary to examine
the previous investigations in the regime of ultra-low Reynolds
numbers. The unsteady incompressible laminar flow over a
Gurney flapped airfoil is investigated using three approaches;
namely unsteady accurate, unsteady inaccurate, and quasisteady.
Overall, all the simulations showed that at ultra-low
Reynolds numbers quasi-steady solution does not necessarily
have the same correlation with the time averaged results
over the unsteady accurate solution. In addition, it was observed
that results of unsteady inaccurate approach with very
small time steps can be used to predict time-averaged
quantities fairly accurate with less computational cost.
to be complex especially in steep descent where the rotor
is operating inside its own wake. It is often reported that, in
this flight condition, the rotor is susceptible to severe wake
interactions causing unsteady blade load, severe vibration,
loss of performance, as well as poor control and handling.
So far, there is little data from experimental and numerical
analysis available for rotors in axial flight. In this paper,
the steady Reynolds-Averaged Navier-Stokes Computational
Fluid Dynamics solver Helicopter Multi-Block was used to
predict the performance of rotors in axial flight. The main
objective of this study was to improve the basic knowledge
about the subject and to validate the flow solver used.
The results obtained are presented in the form of surface
pressure, rotor performance parameters, and vortex wake
trajectories. The detailed velocity field of the tip vortex
for a rotor in hover was also investigated, and a strong
self-similarity of the swirl velocity profile was found. The
predicted results obtained when compared with available
experimental data showed a reasonably agreement
for hover and descent rate, suggesting unsteady solution for
rotors in vortex-ring state.
investigation with a VLM-1 model in 1:50 scale is carried out at the Brazilian Pilot Transonic Wind Tunnel, located in the Aerodynamics Division of the mentioned Institute, using the classical schlieren flow visualization technique. Schlieren images are obtained for nominal Mach number varying from 0.9 to 1.01. Numerical simulation using Stanford’s SU2 code is conducted together with the experimental investigation in order to improve the understanding of the complex physical phenomena associated with the experimental results of this particular regime. The combination of the 2 techniques allowed the assessment of some important aspects on the flow field around the vehicle in the conditions considered in this study, such as shock wave/boundary-layer interaction. The numerical simulation is also very important, allowing the quantification of some important parameters and confirming the shock wave formation patterns observed in the simulation when compared with the Schlieren images. A good agreement regarding the position of the shock wave, when compared with the schlieren images, with a maximum error of about 6%, is observed over the VLM model.
based multidisciplinary design optimization are based on probability mathematics (transformation to standard space), calculating an approximation of the constraint functions in standard space and finding the most probable point, which is the best possible one. The current approach used in this paper was inspired on interval modeling, so it is good when there is insufficient data to develop a good estimate of the probability density function shape or parameters. This approach has been implemented for an existing Unmanned Aerial Vehicle (UAV, Global Hawk) designed for purposes of comparison and validation. The advantages of the provided approach are independence of probability mathematics, appropriate when there is insufficient data to approximate the uncertainties variables, appropriate speed to calculate the best reliable response, and proper success rate in the presence of uncertainties.
measurement of a 6-GHz Frequency Selective Surface filter
is presented. The prototyping resolution of a large (A4 sheet
size) Frequency Selective Surface with small loops as elements
is checked, as well as the correlation with measurements
performed with a 3-D full-wave solver. The test also involved
the effect of cascading two different Frequency Selective
Surfaces with a viewpoint towards a narrower frequency
range, which provided good results.
to the university classroom for the aerospace and aviation
industry personnel, given the fast-paced change taking place
in both the industry and the education sectors. A synopsis of
the current challenges faced in the educational field is outlined,
followed by a mapping of the future of both education and air
platforms, in an attempt to set the basis of the needed skills
framework. The Assessment and Teaching of 21st Century
Skills Project is used as a baseline for the definition of the
future “critical” skill set, which is considered well aligned with
the future needs of the aerospace industry. It is suggested
that this critical skill set can be translated to the higher
education environment through an effective redesign of the
existing teaching and learning philosophy and the practices.
information between the UAVs is proposed for the system. The stability analysis of the proposed formation control protocol is also performed. The research suggests
that, when the time delay, communication topology, and control protocol satisfy the stability condition, the formation control protocol will guide the multi-UAV system to
asymptotically converge to the desired velocity and shape the expected formation team, respectively. Numerical simulations verify the effectiveness of the formation control system.
strong scattering sources, which are located on the spatial cone target, are deduced under three micro-motion types including nutation, precession, and spinning, and the correctness is verified by the electromagnetic simulation. By comparison, differences are found among the projection of the scattering sources with different micro-motions, the coordinate information of the scattering sources in the Inverse Synthetic Aperture Radar sequences is extracted by the CLEAN algorithm, and the spinning is recognized by setting the threshold value of Doppler. The double observation points Interacting Multiple Model Kalman Filter is used to separate the scattering sources projection of the nutation target or precession target, and the cross point number of each scattering source’s projection track is used to classify the nutation or precession. Finally, the electromagnetic simulation data are used to verify the effectiveness of the micro-motion recognition method.
release pyrotechnic compositions is common in
the space and defense areas. Pyrotechnic compositions of
magnesium/Teflon/Viton are widely used in military flares
and pyrogen igniters for igniting the solid propellant of a
rocket motor. Pyrotechnic components are considered highrisk
products as they may cause catastrophic accidents
if initiated or ignited inadvertently. To reduce the hazards
involved in the handling, storage and transportation of
these devices, the magnesium/Teflon/Viton composition
was subjected to various sensitivity tests, DSC and had its
stability and compatibility tested with other materials. This
composition obtained satisfactory results in all the tests,
which qualifies it as safe for production, handling, use,
storage and transportation.
simulated scenarios are the primary source of data for
evaluating different target tracking algorithms in most
researches presented in the literature. Despite the
convenience of simulation, ultimate evaluation of a tracking
algorithm must be made in real scenarios. Unfortunately,
real radar measurements as well as accurate aircraft
position, necessary for calculating tracking errors, are not
easily available. In this paper, we present an evaluation of the
well-known Interacting Multiple-Model with Probabilistic Data
Association Filtering algorithm using data obtained from a flight
inspection of a Brazilian Air Force ground-based long-range
surveillance radar. The presented results show that, in this
scenario the Interacting Multiple-Model with Probabilistic Data
Association Filtering algorithm performance using real data is
worse compared to simulation. Statistical properties of the
real radar measurements are also investigated, and some
evidence is found that embedded noise is not well modeled
as perfectly white.
Niño/Southern Oscillation-neutral years was studied for
the Centro de Lançamento de Alcântara region. Monthly
precipitation, sea surface temperature, wind at 925 hPa
and outgoing longwave radiation data from various gridded
datasets for the 1951–2010 period (60 years) were used.
The data grouping was based on terciles. For the Centro de
Lançamento de Alcântara in El Niño/Southern Oscillationneutral
years, March is the month of the rainy quarter
(March to May) when the interhemispheric gradient of the
sea surface temperature anomalies over the Atlantic (GRAD)
and the atmospheric circulation at 925 hPa over the Centro
de Lançamento de Alcântara were able to best explain the
variability of precipitation. In this month, the wind direction at
925 hPa was the factor that explained the highest fraction
of precipitation variance (40%), followed by GRAD (30%) and
the wind magnitude (20%). For the Centro de Lançamento de
Alcântara, in general, above-average precipitation was related
to weak north-northeasterly low-level winds and southward
GRAD, while below-average precipitation was related to strong
east-northeasterly low-level winds and northward GRAD.
These features were related to an eastward expansion of the
Amazon convection towards the northern Northeast Brazil
and might be related to a slight southward displacement
of the Intertropical Convergence Zone in above-average
precipitation years.
at the same time, of aircraft stability and control
parameters taking into account dynamic damping derivatives.
Such derivatives, due to the rate of change of the
angle of attack, are usually neglected. So the damping
characteristics of aircraft dynamics are attributed only on
pitch rate derivatives. To cope with the dynamic effects of
these derivatives, authors developed devoted procedures
to estimate them. In the present paper, a complete model
of aerodynamic coefficients has been tuned-up to identify
simultaneously the whole set of derivatives. Besides,
in spite of the employed reduced order model and/or
decoupled dynamics, a six degrees of freedom model has
been postulated without decoupling longitudinal and lateral
dynamics. A recursive non-linear filtering approach via
Extended Kalman Filter is proposed, and the filter tuning is
performed by inserting the effects of dynamic derivatives
into the mentioned mathematical model of the studied
aircraft. The tuned-up procedure allows determining with
noticeable precision the stability and control derivatives. In
fact, either by activating maneuvers generated by all the
control surfaces or by inserting noticeable measurement
noise, the identified derivatives show very small values of
standard deviation. The present study shows the possibility
to identify simultaneously the aircraft derivatives without
using devoted procedures and decoupled dynamics. The
proposed technique is particularly suited for on-line parametrical
identification of Unmanned Aerial Systems. In fact,
to estimate both state and aircraft parameters, low power
and time are required even using measurement noises
typical of low-cost sensors.
work reports on a comparative study of the enhanced
radiation properties of a standard X-band horn antenna
loaded by a wire medium. Acting as an artificial dielectric,
the wire medium consists of an array of parallel metallic
wires installed into the antenna with the wires oriented in the
direction of the incident electric field. As compared with the
properties of the air horn antenna, the wire-medium antenna
produces an appreciable reduction in the side-lobe levels with
an improvement of 10 dB at 8.87 GHz in the first side lobe.
For the wire-medium antenna, the E- and H-plane radiation
patterns look similar, a property desired for precision radar
and radiometric mapping systems.
effect of carboxyl and amino functionalization of multiwalled
carbon nanotubes on the mechanical property of
the epoxy resin filled with modified carbon nanotubes. The
carbon nanotubes were treated with sulfuric and nitric
acids and also with hexamethylenediamine. The presence
of acid and amine chemical groups on the carbon nanotube
surface was confirmed by X-ray photoelectron spectroscopy.
The composites were produced with epoxy resin and
modified carbon nanotubes. Vickers hardness tests were
carried out on the composites and neat resin. The results
showed an increase of hardness in the composite prepared
with functionalized carbon nanotubes. This phenomenon is
due to the fact that the chemical interaction between
modified carbon nanotube and epoxy resin is much stronger
than between pristine carbon nanotube and epoxy resin.
This stronger interaction is related to the presence of
functionalized carbon nanotubes.
measurement of electrical energy required for EEDs ignition is necessary. The electrical energy of EEDs has been determined experimentally by instrumentation and measurement setup using hall sensor and photo detector. The hall sensor is used to measure the actual current passing through EEDs when power supply is applied to them. Photo detector is used to detect the flash produced during EED ignition. By conducting repeated trials, it was observed that this method is reliable to determine the electrical energy required for EEDs ignition. With this parameter, the actual current to be supplied and the pulse width of supplied current for repeated ignition delays can be determined. Knowing the electrical energy of a particular EED by the proposed method, the required firing cable length and power supply for ignition of critical delay applications can
be selected. This method also helps to design explosive-based ignition systems in defence applications.
parts, binder matrix (prepolymer, plasticizer, cross linker,
antioxidant and curative etc.) and solid ingredients (oxidizer,
metal fuel, burn rate modifier, combustion stabilizer etc.). Its
processing involves several stages like ingredient preparation
(grinding, 1.1 Hazard Division – 1.1 HD), mixing (1.1 HD),
casting (1.1 HD), curing (1.3 HD) and extraction (1.3 HD).
Each and every process is very hazardous. Removal of any
of the mentioned step will be a great achievement for solid
rocket motor processing. Mandrel is used to give proper
grain geometry. But for metal mandrel, its extraction process
(1.3 HD) is very dangerous. Proper safety precaution should
be taken to perform the said operation. Also, for a metal
mandrel, it is very difficult to develop intricate grain geometry
due to extraction problem. This paper mainly deals with
casting techniques of propellants (case bonded or cartridge
loaded) with a chemically collapsible mandrel. This mandrel is
collapsed in presence of suitable chemicals, hence extraction
step (1.3 HD) becomes simpler. As the extraction process
is very easy, intricate grain geometry can be developed in
solid rocket motor. The mandrel is cheap, recycleable and
relatively lightweight compared to the metal mandrel, thus
handling becomes very easy. The mandrel material and the
dissolution solvent have no effect on the propellant, which
will be confirmed by evaluation of physicochemical as well as
ballistic properties measurement.
different polymorphic forms, including hematite (α-Fe2O3),
magnetite (Fe3O4) and maghemite (γ-Fe2O3). Solid propulsion
technology nanoparticulate materials, such as hematite
and maghemite, exhibit high performance on thermal
decomposition of ammonium perchlorate. The enhanced
catalytic effect of metallic iron oxide nanoparticles is
attributed to their particle size, more active sites and
high surface area, which promotes more gas adsorption
during thermal oxidation reactions. Nowadays, metallic iron
nanoparticles can be synthesized via numerous methods,
such as co-precipitation, sol-gel, microemulsion, or thermal
decomposition. Although there are data on these synthetic
methods in the literature, there is a lack of details related
to nanoparticulate oxides and to their characterization
techniques. In this context, this short review based on
scientific papers, including data from the last two decades,
presents methods for obtaining nanoparticulate iron oxides
as well as the main aspects of the different characterization
techniques and also about the decomposition aspects of
these nanomaterials. Morphologies and structures of iron
oxides can be characterized through transmission electron
microscopy, scanning electron microscopy, X-ray powder
diffraction, and Fourier transform infrared spectroscopy.
As for textural properties, they are usually determined by
physical adsorption techniques.
that assists in planning flight activities of the Academia da
Força Aérea (AFA) so that meteorological data can be used to
predict the occurrence of fog. This system was developed in
MATLAB 8.0 by applying multilayer perceptron-type artificial
neural networks and using an error correction algorithm
called backpropagation. The methodology used to implement
the network comprises eight input variables, five neurons in the
intermediary layer, and one neuron in the output layer, which
corresponds to the presence or absence of fog. The fog
phenomenon is very important for the study and definition of
flight strategic planning. Data taken from 1989 to 2008 and
related to the input variables were used for the training
and validation of the proposed network. Consequently, the
multilayer perceptron network has a 95% reliability compared
with the data collected. This high level of reliability is an
exceptional result for the management, planning, and
decision making team of the AFA strategic group. Thus, it
can be concluded that the proposed system is efficient and
will subsidize, with good safety margin, AFA’s flight activity
planning and could also be applied to other air activities in Brazil.
essential activity during the development and operation of
launch vehicles, due to the complexity of such systems. Of
particular interest is the flight dynamics simulation, which
investigates the behavior of the vehicle in flight subjected to
forces and moments. This work presents a simulation tool
suited to perform six degrees-of-freedom flight dynamics
investigations of launch vehicles. Developed at the Instituto
Nacional de Pesquisas Espaciais (INPE) and the Instituto de
Aeronáutica e Espaço (IAE) in Brazil, the tool was implemented
following the requirement for flexibility, so that it can be used
to simulate different types of launch vehicles. The assessment
of the vehicle performance and the vehicle payload capacity
are some examples of analysis that can be performed with
the tool. A modular programming strategy was employed to
assure the tool flexibility. Therefore, the models presented
in the tool were implemented as separate modules. The
combination of these models can originate flight models of
different launch vehicles. Two flight scenarios of Brazilian
rockets were simulated and the results were verified against
simulation tools already employed by aerospace community.
The developed tool showed good agreement with respect to
the simulators used to perform the comparison.
method and simulate the deployment mechanism of inflatable
antenna structures. Different folded methods are developed
for the primary members of inflatable antenna structures,
which include inflatable tubes, an inflatable torus, a reflector
etc. The unstressed configuration and the folded configuration
of these members are modeled parametrically using the
developed folded methods. A simulation software is developed
for the deployment mechanism of inflatable structures by
the improved spring-mass system. The driving forces in the
deployment process, i.e. the gas pressure and the moment
of the fold hinges, are analyzed for each member. During
the development process, self-contact or collision with the
membrane occurs. A rule for identifying self-contact elements
is applied, and a penalty function method is developed to
solve this challenging problem. Finally, the equation of motion
is solved using finite difference method. The developed
simulation software is validated by simulating a cylindrical
inflatable tube that is folded in half, and the simulation agrees
well with the experiment. The deployment mechanism of
the antenna model similar to that for the Inflatable Antenna
Experiment (IAE) is modeled, analyzed and estimated. The
deployed configurations and the dynamic parameters of each
node are obtained. The numerical simulation results show
that the simulation software for the deployment mechanism
can correctly predict the deployment process of inflatable
antenna structures.
engineering field include, among others, the development of
increasingly lightweight and flexible materials, allowing better
performance of systems in applications such as Unmanned
Aerial Vehicles, photographic model airplanes, light weight
aircraft etc. This progress, however, can cause difficulties in
design and various types of tests, such as those performed in
modal analysis, since the instrumentation weight and shape
can influence the behavior of very light and aerodynamic
structures. This paper proposes a new technique to perform
modal analysis in simple structures, eliminating the use of
accelerometers, which must be numerous in this type of
analysis and have significant weight; the whole structure can
be analyzed at the same time, and this is an advantage in
comparison with other techniques as vibrometer laser, that
analyses one point at a time. The technique in question makes
use of infrared imaging, detecting, through the heat, the
structure deformation, allowing the trace of its modal shape.
For this, a theoretical analysis and a thermomechanical
modeling of a known structure are performed, with
subsequent test to be validated, and finally the conclusions
and suggestions for future work are presented.
components are a complex multidisciplinary process. At
the beginning of the power class definition and engine
configuration it is necessary to conduct a market study. The
results obtained are used in gas turbine thermodynamic cycle
calculations and analysis in order to define the gas turbine
design point. Several possible design points are evaluated
during this procedure. After this step, the gas turbine
components are designed, including: compressor, combustion
chamber and turbine. For industrial gas turbine purposes, it
is common to use a free turbine after the gas generator, also
commonly named power turbine. In this work, a power turbine
was initially designed by meanline techniques, considering
internal loss mechanisms, to obtain the main dimensions.
The geometries of the components were generated in a 3-D
environment to make possible the mesh generation, process
to discretize the physical domain into a computational domain
and use a 3-D Computational Fluid Dynamics tool. The results
from the meanline approach and from the 3-D turbulent flow
numerical simulations were compared to verify the turbine
operational conditions and its predictions at design and offdesign
conditions. The gas turbine under study is a project,
derived from a low thrust turbojet previously developed by
Instituto de Aeronáutica e Espaço. The power turbine project
uses the same turbojet gas generator, already designed and
currently under tests.
Environmental Risk Analysis framework, a multi-disciplinary
optimisation tool developed by Cranfield University, is
utilised in conjunction with an in-house optimiser to carry
out aircraft engine cycle optimisation processes. The
central point here is the evaluation of the capabilities of the
in-house optimiser for performing this type of optimisation
processes. Simplifying hypotheses are thus considered
when both defining the aircraft flight trajectory and modelling
the different engine configurations analysed. Accordingly,
several optimum engine cycles minimising separately three
objective functions, (i) specific fuel consumption in cruise,
(ii) fuel burned, and (iii) oxides of nitrogen emitted, are
determined. The cycle optimisation processes carried out
yield results reflecting the general trends expected when
optimising according to these objective functions. It follows
then that the in-house optimiser is suitable for carrying
out gas turbine power plant optimisation processes. It is
expected that this optimiser be utilised in future for both
optimising the preliminary design of gas turbine engines and
determining optimum and “greener” aircraft engine cycles.
universally pretty low. On the basis of full analysis of aircraft assembly’s feature, this study proposes a forecasting model based on support vector machine (SVM), which is optimized by particle swarm optimization. It can carry out quantitative
prediction of the process’ man-hour during aircraft’s
assembly. Firstly, we decompose aircraft’s assembly work by the concept of work breakdown structure. Further, the process parameters related to man-hour were listed and we made necessary correlation analysis of these historical data. Parameters with high contribution are then used as input of forecasting model. A new forecasting model utilizing SVM is
proposed, which carries out the process as the minimum research granularity. Its performance is compared with back propagation neural network. The process of automatic drilling & riveting is adopted as an example in order to present and validate the model. Experimental results reflect that SVM has high forecast precision and good fitness, so that it is suitable for small sample prediction. Through the optimization, it can effectively predict man-hour of assembly work in a short time while maintaining sufficient accuracy.
satellite mission, named Libertad 2. It will carry out a system of image acquisition as a working tool for researches based on the obtained data. Complete methodologies are often used in the development of satellite missions for planning, execution and deployment, for example, the standards of the European Cooperation for Space Standardization; these methodologies, however, do not include technical specifications or requirements for the development of nano-satellites nor for their subsystems. For this reason, this article focuses on the identification of the characteristics, requirements and restrictions, which must be considered in the design of a remote sensing system for satellites under the CubeSat standard, in order to serve as a starting point for the development of the main payload of the Libertad 2 mission.
Turbomachines Department at ITA is the human resources training for design and development of aeronautical and industrial gas turbines, necessary for the Gas Turbine Program of the Departamento de Ciência e Tecnologia Aeroespacial (DCTA). The human resources training is carried out in undergraduate and graduate courses at ITA, where topics in gas turbine and turbomachinery are taught. The gas turbine topic is taught in the undergraduate degree, in Mechanical-Aeronautical Engineering course, and focuses on gas turbines’ performance for different configurations (turboshaft, turbojet and turbofan). Lecture notes containing the essential elements of the course are made available for the students, addressing the basic
theory of the gas turbines required for the performance study at the design and off-design point. The technological aspects are presented and discussed during detailed studies of the actual cycle. Simple gas turbines and more sophisticated ones are studied, for both aeronautical and industrial application. Performance calculations at design and off-design point of the main engine’s components and the cycle are done manually, encouraging students to develop spreadsheets. The theory is complemented with laboratory classes and technical visits, when the practicalities involving gas turbines operation and tests are presented to the students. As an activity laboratory class, the students perform disassembly-assembly of a small industrial gas turbine.
where deterministic calculations are costly and
confidence intervals of SEA are not satisfied, hybrid FEM/SEA models can be used. This work presents a coupled vibro-acoustic analysis methodology of the Brazilian Satellite Launcher Vehicle payload fairing. FEM/FEM model accounts for the low-frequency internal responses. The high-frequency responses are computed by a SEA coupled elasto-acoustic model, and a hybrid FEM/SEA model calculates the payload fairing mid-frequency behavior.
uses a single equivalent layer for the discretization of the mechanical displacement field and a layerwise representation of the electrical field is adopted. Temperature effects are neglected. Simulation results illustrate the effectiveness of the proposed vibration control methodology for composite structures.
in the development of new generation of electronic devices. The carbon nanotubes allow one fabrication of devices using nanometric scales. They can be used in projects of a wide range of electronic and optoelectronic components such as diodes, transistors and interconnection elements, among others. This paper presents the state-of-the-art of this area, emphasizing the influence of quantum effects on the characteristics of such components.