 Subjects -> AERONAUTICS AND SPACE FLIGHT (Total: 124 journals)
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- Publisher Correction: Hygrothermal Effects in Aeronautical Composite
Materials Subjected to Freeze–Thaw Cycling-
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PubDate: 2024-09-01
- Near-Optimal Feedback Guidance for Low-Thrust Earth Orbit Transfers
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Abstract: Abstract This research describes a near-optimal feedback guidance, based on nonlinear orbit control, for low-thrust Earth orbit transfers. Lyapunov stability theory leads to proving that although several equilibria exist, only the desired operational conditions are associated with a stable equilibrium. This ensures quasi-global asymptotic convergence toward the desired final orbit. The dynamical model includes the effect of eclipsing on the available thrust, as well as all the relevant orbit perturbations, such as several harmonics of the geopotential, solar radiation pressure, aerodynamic drag, and gravitational attraction due to the Sun and the Moon. Near-optimality of the feedback guidance comes from careful selection of the control gains. They are identified in two steps. Step (a) is an extensive table search in which the gains are changed in a large interval. Step (b) uses a numerical optimization algorithm that refines the gains found in (a), while minimizing the time of flight. For the numerical simulations, two scenarios are defined: (i) nominal conditions and (ii) nonnominal conditions, which arise from orbit injection errors and stochastic failures of the propulsion system. For case (i), gain optimization leads to obtaining numerical results very close to those corresponding to a known optimal orbit transfer with eclipse arcs. Moreover, for case (ii), extensive Monte Carlo simulations demonstrate that the nonlinear feedback guidance at hand is effective in driving a spacecraft from a low Earth orbit to a geostationary orbit, also in the presence of nonnominal flight conditions.
PubDate: 2024-09-01
- Development of a Ferrofluid-Based Attitude Control Actuator for
Verification on the ISS-
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Abstract: Abstract Ferrofluid-based systems provide an opportunity for increasing the durability and reliability of systems, where mechanical parts are prone to wear and tear. Conventional reaction control systems are based on mechanically mounted rotating disks. Due to inherent friction, they suffer from degradation, which may eventually lead to failure. This problem is further intensified due to the limited possibility for repair and maintenance. Ferrofluid-based systems aim to replace mechanical components by exploiting ferrofluidic suspended motion. Ferrofluids consist of magnetic nanoparticles suspended in a carrier fluid and can be manipulated by external magnetic fields. This paper describes the working principle, design, and integration of a working prototype of a ferrofluid-based attitude control system (ACS), called Ferrowheel. It is based on a stator of a brushless DC motor in combination with a rotor on a ferrofluidic bearing. The prototype will be verified in a microgravity environment on the International Space Station, as part of the Überflieger 2 student competition of the German Aerospace Center. First ground tests deliver positive results and confirm the practicability of such a system.
PubDate: 2024-09-01
- Extended Sufficient Conditions of Strong Minimality for the Bolza Problem
with Bang Bang Controls. Applications to Space Trajectory Optimization-
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Abstract: Abstract This paper presents extended sufficiency results for the local minimality of an extremal of the Bolza problem. These results provide an essential improvement in the state of the art because they are applicable for bang–bang control without requiring the strict Legendre and controllability conditions. Extended sufficient conditions subsume the classic Jacobi conjugate point sufficiency conditions. Necessary conditions of the second order allow to exclude the minimality when sufficiency is not verified. All these results are applicable to space trajectory optimization both in low thrust and in impulsive transfer.
PubDate: 2024-09-01
- A Combustion-Driven Facility for Hypersonic Sustained Flight Simulation
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Abstract: Abstract This study reports on the development of a new Blowdown-Induction Facility driven by two different Oxygen-Fueled Guns. The facility has been conceived and realized to simulate different flow conditions in the context of hypersonic sustained flight. Here the underlying principles are illustrated critically, along with a focused description of the various facility subsystems, their interconnections and the procedures specifically conceived to overcome some of the technical complexities on which this facility relies. Its performances are finally presented in relation to some prototype applications, together with an indication of the related limits, advantages and possible directions for future improvements.
PubDate: 2024-09-01
- Modeling, Simulation, and Control of a Formation of Multirotor Aircraft
for Transportation of Suspended Loads-
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Abstract: Abstract This work aims to contribute to the innovation in the urban air mobility and delivery sector and represents a starting point for air logistics and its future scenarios. The dissertation focuses on modeling, simulation, and control of a formation of multirotor aircraft for cooperative load transportation, with particular attention to the stabilization of payload swing motion. Starting from the mathematical model of two identical multirotors, formation-flight-keeping and collision-avoidance algorithms are implemented to ensure the safety of the vehicles within the formation and that of the payload. Then, a mathematical model for the suspended load is implemented, as well as an active controller for its stabilization. The focus of this section is thus represented by the analysis of payload oscillatory motion, whose kinetic energy decay is investigated. Several test cases are presented to establish the most effective and safe strategy in light of future aerospace applications.
PubDate: 2024-09-01
- Hygrothermal Effects in Aeronautical Composite Materials Subjected to
Freeze–Thaw Cycling-
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Abstract: Abstract Fiber-reinforced composites (FRC) have gained widespread recognition in the aerospace, automotive, and energy industries due to their exceptional strength to-weight ratio. However, comprehending their performance within varying environmental contexts poses a multifaceted challenge. Specifically, the influence of humidity, temperature fluctuations, and freeze–thaw cycles on the structural integrity of FRC components requires careful examination. This research work seeks to provide insights into the effects of humidity, temperature, and freeze thaw cycles on FRC inter-laminar regions and the critical matrix/fiber interface. The experimental methodology employed includes a comprehensive array of techniques, such as thermal analysis, X-Ray tomography, and ILSS mechanical testing. Through these methods, an effort is made to discern the material’s response to the environmental variables. Carbon-reinforced composites exhibited a shear strength reduction of 16.9% at 80 °C, and glass-reinforced composites displayed a reduction of 18.4%. Further increasing the temperature to 125 °C resulted in a reduction of 32.5% for carbon-reinforced composites and 38.8% for glass-reinforced composites. In hot-wet conditions, which combine humidity saturation and a testing temperature of 80 °C, the shear strength reductions were the most pronounced, with a reduction of 48.7% for carbon-reinforced composites and 60.2% for glass-reinforced composites. Moreover, freeze–thaw cycle has been performed. The findings of this research endeavor hold profound implications for both the design and maintenance of FRC components. As FRCs continue to gain prominence in critical applications, an enhanced understanding of their behavior in diverse environmental conditions becomes increasingly imperative.
PubDate: 2024-09-01
- Simulation of In-Space Fragmentation Events
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Abstract: Abstract In the next years, the space debris population is expected to progressively grow due to in-space collisions and break-up events; in addition, anti-satellite tests can further affect the debris environment by generating large clouds of fragments. The simulation of these events allows identifying the main parameters affecting fragmentation and obtaining statistically accurate populations of generated debris, both above and below detection thresholds for ground-based observatories. Such information can be employed to improve current fragmentation models and to reproduce historical events to better understand their influence on the non-detectable space debris population. In addition, numerical simulation can also be used as input to identify the most critical objects to be removed to reduce the risk of irreversible orbit pollution. In this paper, the simulation of historical in-orbit fragmentation events is discussed and the generated debris populations are presented. The presented case-studies include the COSMOS-IRIDIUM collision, the COSMOS 1408 anti-satellite test, the 2022-151B CZ-6A in-orbit break-up, and a potential collision of ENVISAT with a spent rocket stage; for these events, results are presented in terms of cumulative fragments distributions and debris orbital distributions.
PubDate: 2024-09-01
- Numerical Analysis of the Impact of Process Parameters on the Residual
Stress of a Flat Composite Part-
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Abstract: Abstract This paper presents a numerical approach to assess the influence of process parameters on a composite part’s mechanical properties. A one-dimensional thermochemical model is used to predict the curing progress of the resin during the curing cycle. Material properties are derived using the cure hardening instantaneous linear elastic model, and a refined one-dimensional model derived within the Carrera Unified Formulation framework is used to obtain accurate results concerning process-induced stresses. Various process parameters, such as the holding temperature and heating rate, are evaluated. The results show that some process parameters, such as the fiber volume fraction and holding temperature, significantly influence composite characteristics and process-induced stresses. It is also shown that modifications to curing cycles leading to reduced energy overhead may not affect performances.
PubDate: 2024-08-01
- Continuum and Discrete Analytical Methods for Vibration and Buckling
Eigenvalues Shape Sensitivities-
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Abstract: Abstract Gradient-based optimization techniques need precise and efficient sensitivities. Numerical sensitivity methods such as finite differences are easy to implement but imprecise and computationally inefficient. In contrast, analytical sensitivity methods, such as the discrete and continuum ones are highly accurate and efficient. Continuum Sensitivity Analysis (CSA) is an analytical method used to calculate derivatives of shape or value parameters. While CSA has been successfully applied in static analysis and dynamic problems in the time domain, this work presents an extension of the approach to eigenvalue sensitivities for the first time. However, CSA revealed limitations, prompting the exploration of an alternative approach based on discrete analytical differentiation. This method is employed for the first time in shape sensitivities. The derivatives of the stiffness and mass matrices required by the method are calculated analytically, resulting in high accuracy and computational efficiency. In addition, an element agnostic approach has been developed leveraging primary analysis matrices to calculate their derivative. This characteristic, along with the nonintrusivity, makes the method employable with standard commercial software. Both approaches have been applied and validated in a wide range of scenarios, involving vibration and buckling problems.
PubDate: 2024-07-31
- AIDAA News #23
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PubDate: 2024-07-04
- Considerations for a Spaceport in Venezuela: A Developing Country
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Abstract: Abstract The reduction of components and the development of more powerful satellites with smaller dimensions have allowed an increasing number of users, including universities, research centers, and space agencies in developing countries, to have access to technologies and/or equipment that would have been impossible a few decades ago, paving the way for the development of low-cost space missions. However, the space drive in developing countries includes not only the acquisition of small satellite components, or the construction of CubeSats, but also the creation of spaceports, from which agencies could launch their own delivery vehicles. The rapid worldwide increase of CubeSats, and the long waiting periods between launches of the main payloads, prompted the present investigation, where the main factors to consider in the selection of a spaceport location were stipulated. Therefore, to meet the objective of studying the various factors, a series of points to be analyzed were established: low latitudes, azimuth limitations, natural factors, political and social considerations, airspace, accessibility, and political stability. After analyzing the factors, we proceeded to the analysis of various locations in Venezuela for small space vector missions, where starting from three possible locations and after analyzing each one, we obtained as a result “El Pao”, a location in the Venezuelan plains, far from urban centers, with good communication routes, latitude of only 9° and few azimuth limitations. However, the factors analyzed in this research are not exclusively framed in the Venezuelan space effort as they are common to any country wishing to establish a spaceport in its territory.
PubDate: 2024-07-04
- Material Characterisation of Deflated Structured Fabrics
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Abstract: Abstract Structured fabrics are made by interwoven rigid elements that form flexible garments such as chain mail armours. Traditionally, the mechanical properties of these materials were considered fixed. However, recent research has revealed their mechanical properties may be varied. Notably, studies have demonstrated that applying vacuum pressure between layers of 3D-printed chain mails enclosed in a bag induces particle and layer jamming of the elements, thereby affecting the material’s bending modulus. This arises from both compressive frictional forces and the complex geometrical interlocking of the rigid elements. This paper presents a comprehensive set of experimental tests for the characterisation of the stiffness and damping properties with respect to the type and number of fabrics and with respect to the vacuum pressure. More specifically, the study examines experimentally the changes in static properties in response to vacuum pressure changes evaluated on a four- and six-point bending setups. The outcome of this measurement campaign is then reported into the Ashby diagrams to compare the mechanical properties of the in-vacuum structured fabrics with those of classical materials. The potential applications of this research include the development of lightweight adaptive and semi-active vibration mitigation devices.
PubDate: 2024-07-02
- Prediction of Helicopter Rotor Loads and Fatigue Damage Evaluation with
Neural Networks-
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Abstract: Abstract In recent years, machine learning algorithms have experienced rapid advancement, driven by the exponential growth of data availability and computational capabilities. Among these algorithms, artificial neural networks stand out as one of the most renowned and effective classes, possessing the ability to discern relationships within data. In this study, we harness neural networks to deduce the relationship between flight mechanics parameters and resulting loads in an articulated rotor configuration. The accuracy of these algorithms hinges closely on the quality of the dataset used for training. Given that rotor loads manifest as time-periodic signals with precise harmonic content, we train dedicated neural networks to predict each harmonic individually. Subsequently, the load time history is reconstructed post hoc by amalgamating predictions from each individual network. Various network architectures are explored, and a sensitivity analysis is conducted on hyper-parameters to determine the optimal configuration for this specific application. Moreover, these predictions serve as input for a fatigue damage calculation algorithm.
PubDate: 2024-07-02
- Some Comments About the Quality and Quantity of Papers
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PubDate: 2024-06-28
- Dust Mitigation Strategies Enabling Moon Exploration Missions
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Abstract: Abstract Micrometric dust particles of lunar regolith represent one of the most serious issues of the harsh Moon environment. Indeed, the extremely high vacuum conditions expose the lunar soil minerals to intense ultraviolet and galactic cosmic rays’ bombardment during the Moon’s daylight producing photoionization of the constituent’s atoms and electron release. Moreover, the Moon periodically interacts with the surrounding solar wind which generates a continuous flux of charged particles accompanied by electric fields around the terminator region able to lift off the lunar regolith dust up to ~100 km above the geometrical surface. In this way, micrometric granular matter forms a subtle veil of contaminants. This electrically charged and extremely adhering dust environment not only can cause various critical drawbacks to several robotic parts, e.g., mechanical components, electronic devices, solar panels, thermal radiators, rover seals and bearings, etc. but also can dramatically damage the respiratory systems of humans if accidentally inhaled. For these reasons, lunar dust was recognized, by several agencies including NASA and ESA, as one of the main hazards for the ongoing robotic and manned exploration and colonization of our natural satellite. To overcome or at least mitigate these issues, several technologies were developed and assessed ranging from the active ones requiring a source of energy, e.g., mechanical, fluidal, and, above all, electric devices, to the passive technologies involving suitable material design and development. The work here reported presents several possible active and passive chemical and physical strategies for protecting sensitive surfaces of space systems against granular contamination. This paper is intended as a survey of dust mitigation issues and technical mitigation with the approach pursued by the Italian Aerospace Research Centre (CIRA) related to a hybrid technique with an innovative material. The strategy that is under implementation by CIRA is based on the combination of active and passive techniques and consists of the design and development of innovative high-performance polymers exhibiting simultaneously outstanding thermo-mechanical properties and superior non-sticking capacity, i.e., abhesion.
PubDate: 2024-06-19
- Characterization of the Spray System of the TerraXcube Icing Wind Tunnel
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Abstract: Abstract In recent years, the field of Unmanned Aerial Vehicles has shown great technological progress, and many new applications were born. To assess the potential of this technology and to improve the availability and reliability of the rising services it is critical to overcome operational limitations. One key operational hazard is atmospheric in-flight icing, resulting in large aerodynamic penalties, unbalances and other detrimental phenomena that can sometimes lead to catastrophic consequences. In this paper, a new ice tunnel developed in the large hypobaric and climatic chamber of the terraXcube facility of Eurac will be presented. Following a preliminary characterization of the nozzles employed in the tunnel by shadowgraphy at the Free University of Bolzano, a characterization and calibration of the spray system has been performed following the EASA regulation reported in the Easy Access Rules for Large Rotorcraft (CS-29).
PubDate: 2024-06-18
DOI: 10.1007/s42496-024-00224-6
- Development and Preliminary Testing of the ATEMO Multi-Purpose Sensing
Platform-
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Abstract: Abstract In the current global context, where the issue of climate change has gained significant prominence, the ATEMO (Aerospace Technologies for Earth Monitoring and Observation) project introduces an innovative and scalable platform capable of measuring multiple environmental factors, including air pollution, light pollution, and vegetation analysis. This versatile platform can be seamlessly integrated onto various aerial vehicles, such as drones, stratospheric balloons, and tethered balloons. Its primary goal is to establish a comprehensive framework for environmental analysis on multiple fronts, while also contributing valuable data to the scientific literature. Furthermore, it offers a cost-effective alternative with enhanced spatial and temporal resolution for ground-based comparisons. During the initial year of research, ATEMO project focused on amalgamating the technological expertise of the research group into a single device. This device facilitated ground-based light source observations, multi-spectral vegetation analysis, and air quality assessments. The first test campaign, carried out during the summer of 2023, was aimed at estimating vegetation indices and comparing them over time with satellite-derived data. This article provides insights into the current configuration of ATEMO, outlines the testing procedures, and presents the preliminary findings.
PubDate: 2024-06-15
DOI: 10.1007/s42496-024-00222-8
- Enabling Civil Single-Pilot Operations: A State-of-the-Art Review
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Abstract: Abstract Advanced avionics and automation technologies have significantly transformed cockpit operations, resulting in a gradual reduction of the crew members on-board. Single-pilot operations (SPO) concept is gaining significant attention in the aviation industry due to its potential for cost savings and to cope with the anticipated pilot shortage and the increasing air traffic demand. This paper conducts a scoping literature review on SPOs, serving as an initial step to map the scientific peer-reviewed content on the subject. The survey focuses on three thematic domains, which are, respectively, operations, automation, and the emerging field of digital and cognitive flight assistants. The methodology involved the use of Google Scholar and IEEE Xplore databases. Sources were selected adapting the search criteria to the proposed sub-topics and prioritizing either the most cited and recent contributions. The analysis of the literature reveals a growing body of work in the recent years. This review also highlights interest in the human-centered design for automation solutions which are responsive to cognitive and behavioral states of the pilot. While acknowledging the potential safety and operational challenges associated with SPOs and the pilot-automation cooperation, this work suggests that great research efforts should be made on the human factor and regulatory subjects to pave the way for a feasible and safe implementation of the single-pilot paradigm in commercial aviation.
PubDate: 2024-06-13
DOI: 10.1007/s42496-024-00223-7
- Upgrading the Compressor Stage of the CAT250TJ Micro Gas Turbine Engine
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Abstract: Abstract Due to their simplicity and relative ease of manufacture, single-stage centrifugal and mixed flow micro gas turbine (MGT) engines are preferred in thrust-based remotely piloted aerial vehicles. A single-stage mixed-flow compressor upgrade for the 200 N CAT250TJ MGT engine is numerically evaluated and presented. An in-house developed mean line application and commercial CFD software is used for the design and performance evaluation of the proposed upgrade configurations. The CAT250TJ – Gen1 engine features a single-stage centrifugal compressor, annular combustor, and single stage axial turbine. Apart from an upgraded impeller, a new crossover diffuser configuration is introduced to replace the wedge-type, straight outlet diffuser configuration of the Gen1 engine. The new single vane crossover diffuser configuration provides a design point total-to-total efficiency and pressure ratio increase of 8.3% and 12.1%, respectively. A disadvantage of a single-vaned crossover diffuser compared to legacy diffusers is a narrower operating range. To alleviate this issue, various combinations of tandem and splitter vane crossover diffuser configurations are proposed. These provide an enhanced operating range, comparable with the operating range displayed by the Gen1 configuration. A turbine power matching analysis is additionally completed to ensure proper compressor integration. Gas turbine cycle software is used to evaluate the on-engine performance of the upgraded compressor configurations. It is shown that the new baseline, single vane crossover diffuser configuration provides a 10.74% increase in design point static thrust.
PubDate: 2024-06-05
DOI: 10.1007/s42496-024-00221-9
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