Propulsion Elements Research Articles

Rim Driven Thruster as Innovative Propulsion Element for Dual Phase Flows in Plug Flow Reactors

The purpose of this work was to test a new setup to pump water with entrained air for application in gas fermentation. A mixed flow, where gas is contained in a liquid to be pumped, rapidly reduces the efficiency of a conventional pump, due to the compressibility of the gas. It is not always possible to degas the fluid, for instance in gas fermentation, which is preferably carried out in tubular reactors (loop fermenters) to achieve a high conversion rate of the gaseous feedstocks. Method: In this work, a rim-driven thruster (RDT) was tested in a lab-scale, cold flow model of a loop reactor with 5–30% (by volume) of gas fraction (air) in the liquid (water) as alternative propulsion element (6 m total pipe length, ambient temperature and pressure). As a result, it was found that the RDT, in connection with a guiding vane providing swirling motion to the two-phase fluid, could pump a mixed flow with up to 25.7% of gas content (by volume) at atmospheric pressure and 25 °C and 0.5 to 2 m/s flow speed. In conclusion, an RDT is advantageous over a classic propulsion element like a centrifugal pump or axial flow pump for transporting liquids with entrained gases. This article describes the potential of rim-driven thrusters, as known from marine propulsion, in biotechnology, the chemical industry, and beyond, to handle multiphase flows.

Cultural Heritage Recognition through Protection of Historical Value and Urban Regeneration: CSOA Forte Prenestino

The conformation and dynamics of metropolitanisation act as propulsive elements of territorial transformations. The deficiency of infrastructural equipment, the heterogeneity of urban fabric and the lack of services and public spaces contribute to severing the identity ties between settled communities and territories. In light of this, within the more general reflection concerning urban regeneration, we recall the role that cultural heritage plays in the physical and functional organisation of the city, as a reflection of the interaction between community and context. The contribution is contextualized in the research work on the activities related to Thematic Line 4 of the Extended Partnership 5—CHANGES (NRRP). The thematic line activities follow three phases: 1. contextualization; 2. operational phase; 3. experimentation. The research work presented here is part of the ‘operational phase’, to identify strategies and projects for heritage-led regeneration. The article analyses the pilot case of CSOA Forte Prenestino as a starting point for thinking about expanding the research activity to other similar cases. It is a self-managed community centre in Rome (Italy) located in the nineteenth-century Forte, which has become a symbol of collective identity. The case study was identified following three levels of investigation: 1. identification of the municipality, first-level administrative subdivision of the city of Rome (Italy); 2. identification of the main historical, archaeological and architectural emergencies of the municipality; 3. identification of an asset to be analysed as “Heritage by designation” (involvement of experts) and “Heritage by appropriation” (involvement of communities). The research results show the “Recognition Path” of Forte Prenestina: according to what has been ‘designated’ by urban planning instruments, project instruments, legislative instruments and authors of scientific publications and conferences; and on the basis of the bottom-up ‘appropriation’ process of the asset that has allowed its management, assessment of its cultural and social potential and its development. The research results allow us to reflect on heritage-led urban regeneration as a strategy capable of capturing and promoting the links between social integration and cultural–historical identity.

Gateway program status and overview

This paper provides an overview and status of the Gateway, which will be an outpost orbiting the Moon that provides vital support for a sustainable, long-term human return to the lunar surface and a steppingstone to Mars as part of the Artemis program. Gateway is a destination for deep space crew expeditions and science investigations, as well as a port for deep space transportation – for landers en route to the lunar surface or spacecraft embarking to destinations beyond the Earth-Moon system. The National Aeronautics and Space Administration (NASA) leads the Program and serves as the integrator of the spaceflight capabilities and contributions of U.S. commercial partners and international partners to develop the Gateway.This paper will provide an overview of each component of the Gateway: The Power and Propulsion Element, the Habitation and Logistics Outpost; Deep Space Logistics; the International Habitation module; External Robotics System; European System Providing Refueling, Infrastructure and Telecommunications; an Airlock; and Exploration ExtraVehicular Activity (xEVA).Expanding on the successful partnership that has provided over 20 years of continuous crew operations in low-Earth orbit on ISS, the Gateway is an evolution of this extraordinary partnership that leverages the capabilities of each partner to expand humankind's sustained exploration deeper into the cosmos. Highlighting the international program with participation from multiple international partners, this paper will also provide a status of the Gateway multilateral governance structure and international agreements.

Locomotion-induced ocular motor behavior in larval Xenopus is developmentally tuned by visuo-vestibular reflexes

Locomotion in vertebrates is accompanied by retinal image-stabilizing eye movements that derive from sensory-motor transformations and predictive locomotor efference copies. During development, concurrent maturation of locomotor and ocular motor proficiency depends on the structural and neuronal capacity of the motion detection systems, the propulsive elements and the computational capability for signal integration. In developing Xenopus larvae, we demonstrate an interactive plasticity of predictive locomotor efference copies and multi-sensory motion signals to constantly elicit dynamically adequate eye movements during swimming. During ontogeny, the neuronal integration of vestibulo- and spino-ocular reflex components progressively alters as locomotion parameters change. In young larvae, spino-ocular motor coupling attenuates concurrent angular vestibulo-ocular reflexes, while older larvae express eye movements that derive from a combination of the two components. This integrative switch depends on the locomotor pattern generator frequency, represents a stage-independent gating mechanism, and appears during ontogeny when the swim frequency naturally declines with larval age.

Design, Analysis, and Testing of a Scaled Propeller for an Innovative Regional Turboprop Aircraft

This paper describes the design, numerical analyses, and wind tunnel tests of the scaled model of a propeller serving as a propulsive element for the experimental tests of an advanced regional turboprop aircraft with engines installed on the horizontal tailplane tips. The design has been performed by complying with the thrust similarity from the full-scale aircraft propulsive requirements. Numerical analyses with a high-fidelity aerodynamic solver confirmed that the initial design made with XROTOR would achieve the expected performance. Finally, a strengthened version of the propeller has been manufactured via 3D printing and tested in the wind tunnel. Test data include measurements of thrust as well as propeller normal force at different angles of attack. Good agreement between numerical and experimental results has been observed, enabling the propeller to be used confidently in the aircraft wind tunnel powered test campaign.

NASA lunar exploration – gateway's power and propulsion element communications links

NASA lunar exploration – gateway's power and propulsion element communications links

Propulsive Element Normal Force Based on Acceleration Measurements Experienced by a Subcarangiform Robotic Fish

Propulsive Element Normal Force Based on Acceleration Measurements Experienced by a Subcarangiform Robotic Fish

Comparing the characteristics of positional and nonpositional sleep apnea patients among the Jordanian population.

Obstructive sleep apnea (OSA) is a common cause of sleep-disordered breathing with a large proportion of the patients exhibiting positional OSA (POSA). In this study, we aimed to evaluate the differences in the demographics, comorbidities, and polysomnographic features between POSA and non-POSA (NPOSA) in a Jordanian sample to further discern the propulsive elements for each group. In this study, we evaluated 1037 adult patients with OSA. POSA was defined as an overall apnea and hypopnea index (AHI) >5, an overall AHI severity at least 1.4 times the nonsupine severity (overall/NS-AHI), and a minimum amount of time (i.e., 20 min) in the supine and nonsupine positions. To compare the clinical characteristics between POSA and NPOSA patients, statistical analyses were performed. The prevalence of POSA was 41.7%. In comparison to NPOSA patients, POSA patients had higher female sex prevalence, milder OSA, lower body mass index, lower hypertension prevalence, and lower hemoglobin A1C levels compared to NPOSA patients. Moreover, sleep efficiency, total sleep time, and supine sleep time were significantly higher in POSA patients. Nonsupine sleep time, total AHI, rapid eye movement (REM) AHI, non-REM (NREM) AHI, supine AHI, nonsupine AHI, left and right AHI, mean oxyhemoglobin saturation (SpO2) awake, mean REM and NREM SpO2, SpO2 nadir, and time SpO2 below 90% were significantly lower among POSA patients. The multivariate regression analysis showed that only female gender and hypertension were significantly associated with POSA. POSA is common among OSA patients and demonstrates different clinical characteristics in comparison to NPOSA. Future prospective studies are needed to better characterize the POSA patients and investigate the benefit of positional therapy.

Design principles and digital control of advanced distributed propulsion systems

The integration of advanced distributed propulsion (DP) systems within various aircraft configurations holds the potential to greatly increase aircraft performance, particularly in terms of fuel efficiency, reduction of harmful emissions and reduction of take-off field length requirements. This has been enabled by modern analysis tools, materials technology and control systems which take advantage of the positive interactions between the propulsive configuration and the aerodynamics of the aircraft. In particular, synergies are maximized when the propulsion system uses distributed nozzles, crossflow fans and multiple distributed fans. Recent advances in electric propulsion have encouraged the hybridization of propulsive systems, with airliners having multiple electric fans powered by one or two gas turbine engines. Furthermore, due to recent advances in airframe integration solutions, the propulsive element can become an integral part of the control and stability augmentation capabilities of the aircraft. Thereby, the digital control of advanced DP systems is crucial for the purpose of thrust modulation and intelligent management of engine resources and health. This not only aids in mission optimization but also supports the case for airworthiness certification of novel aircraft configurations integrating advanced DP systems. This paper presents a critical review of the existing literature on the subject of DP, identifying the benefits and drawbacks of this technology as well as its proposed practical applications. The review also discusses contemporary advances in hybrid electric technology, aeroelasticity research and the fundamental design steps to integrate advanced DP systems in fixed-wing aircraft. Additionally, an evolutionary outlook is presented on digital control of DP systems with a focus on advancing the techniques for mission optimization and engine health management for enhanced safety and sustainability. Based on the proposed design principles and digital control methodology, conclusions are drawn about the suitability of advanced DP for various applications and recommendations are made for future research and development.

Propulsive performance and vortex wakes of multiple tandem foils pitching in-line

Numerical studies are presented on the propulsive performance and vortex dynamics of multiple hydrofoils pitching in an in-line configuration. The study is motivated by the quest to understand the hydrodynamics of multiple fin–fin interactions in fish swimming. Using the flow conditions (Strouhal and Reynolds numbers) obtained from a solitary pitching foil of zero net thrust, the effect of phase differences between neighboring foils on the hydrodynamic performance is examined both in position-fixed two- and three-foil systems at Reynolds number Re=500. It is found that the three-foil system achieves a thrust enhancement up to 118% and an efficiency enhancement up to 115% compared to the two-foil system. Correspondingly, the leading-edge vortex (LEV) and the trailing-edge vortex (TEV) of the hindmost foil combine to form a ‘2P’ wake structure behind the three-foil system with the optimal phase differences instead of a ‘2S’ wake, a coherent wake pattern observed behind the optimal two-foil system. The finding suggests that a position-fixed three-foil system can generate a ‘2P’ wake to achieve the maximum thrust production and propulsive efficiency simultaneously by deliberately choosing the undulatory phase for each foil. When increasing Reynolds number to 1000, though the maximum thrust and propulsive efficiency are not achieved simultaneously, the most efficient case still produces more thrust than most of the other cases. Besides, the study on the effects of three-dimensionality shows that when the foils have a larger aspect ratio, the three-foil system has a better hydrodynamic performance, and it follows a similar trend as the two-dimensional (2D) foil system. This work aids in the future design of high-performance underwater vehicles with multiple controlled propulsion elements.

Underwater Bending Actuator Based on Integrated Anisotropic Textile Materials and a Conductive Hydrogel Electrode

Electroactive polymers (EAPs), especially dielectric elastomer actuators (DEAs), belong to a very promising and emerging class of functional materials. While DEAs are mostly utilized to rely on carbon-based electrodes, there are certain shortcomings of the use of carbon electrodes in the field of soft robotics. In this work we present a fish-like bending structure to serve as possible propulsion element, completely avoiding carbon-based electrodes. The presented robot is moving under water, using a particularly tailored conductive hydrogel as inner electrode and a highly anisotropic textile material to manipulate the bending behavior of the robot. The charge separation to drive two DEAs on the outsides of the robot is provided by the conductive hydrogel while the surrounding water serves as counter electrode. To characterize the hydrogel, tensile tests and impedance spectroscopy are used as measurement methods of choice. The performance of the robot was evaluated using a digital image correlation (DIC) measurement for its bending deflections under water. The developed fish-like robot was able to perform a dynamic bending movement, based on a tri-stable actuator setup. The performed measurements underpin the sufficient characteristics for an underwater application of conductive hydrogel electrodes as well as the applicability of the robotic concept for under water actuations.

Computational Study of the Propeller Position Effects in Wing-Mounted, Distributed Electric Propulsion with Boundary Layer Ingestion in a 25 kg Remotely Piloted Aircraft

Distributed electric propulsion and boundary layer ingestion are two attractive technologies to reduce the power consumption of fixed wing aircraft. Through careful distribution of the propulsive system elements, higher aerodynamic and propulsive efficiency can be achieved, as well as a lower risk of total loss of aircraft due to foreign object damage. When used on the wing, further reductions of the bending moment on the wing root can even lead to reductions of its structural weight, thus mitigating the expected increase of operating empty weight due to the extra components needed. While coupling these technologies in fixed-wing aircraft is being actively studied in the big aircraft segment, it is also an interesting approach for increasing the efficiency even for aircraft with maximum take-off masses as low as 25 kg, such as the A3 open subcategory for civil drones from EASA. This paper studies the effect of changing the propellers’ position in the aerodynamic performance parameters of a distributed electric propulsion with boundary layer ingestion system in a 25 kg fixed-wing aircraft, as well as in the performance of the propellers. The computational results show the trade-offs between the aerodynamic efficiency and the propeller efficiency when the vertical position is varied.

Required Moment Sets: Enhanced Controllability Analysis for Nonlinear Aircraft Models

Attainable moment sets (AMS) are a powerful method to assess aircraft controllability. However, as attainable moment sets only take into account the achievable moment set of the control effectors, they do not assess the required moment set to fulfill the aircraft mission requirements. This paper proposes to calculate a corresponding required moment set (RMS) which defines a set of moments sufficient for fulfilling aircraft controllability requirements in the mission flight envelope. The paper applies the required moment set approach to a nonlinear simulation model of an electric vertical take off vehicle (eVTOL) transition drone in hover. By comparing the required moment set to the AMS of the aircraft model, moment set margins are derived and used to assess the controllability of the considered aircraft. The results indicate that the combined evaluation directly identifies critical moment channels and margins, which is advantageous when compared to a pure AMS-based evaluation. The proposed approach enables the execution of simulation-based assessments in aircraft design and flight control development. In the early stages of aircraft design, required moment sets can support sizing, positioning and tilting of control effectors (e.g., propulsive elements) to fit the AMS to the actual required force and moment set for the specific system.

АНАЛІЗ НОРМАТИВНИХ ВИМОГ ДО МАТЕРІАЛУ ДЛЯ ВИГОТОВЛЕННЯ ГРЕБНИХ ГВИНТІВ

Мета. На підставі порівняльного аналізу нормативних вимог до використовуваних матеріалів визначити ефективні напрями удосконалення складів та технології обробки сплавів для виготовлення гребних гвинтів морських суден. З урахуванням одержаних даних, встановити перспективні матеріали та шляхи підвищення надійності і довговічності роботи виробів для судноплавства. Методика. В роботі використано метод зіставного аналізу з метою обґрунтування перспективи використання спеціальних бронз для виготовлення деталей, що аналізуються.Результати. Встановлено, що найбільш доцільним матеріалом для виготовлення гребних гвинтів з точки зору сукупності показників конструкційної міцності, зносостійкості та експлуатаційної надійності є алюмінієві бронзи додатково леговані манганом та оловом. Наукова новизна. Новизна технічного рішення полягає в тому, що на підставі аналізу нормативно-технічних вимог до алюмінієвих бронз, які стандартно використовують для виробництва гребних гвинтів, відмічена перспективність додаткового їх легування оловом, що дозволить підвищити корозійну стійкість та опір абразивному зносу, а також манганом, у раціональній кількості, з метою підвищення міцності.Практична цінність. Надана актуальна інформація щодо проблеми підвищення надійності та довговічності роботи гребних гвинтів, одним з методів вирішення якої є цілеспрямований вибір матеріалу для їх виготовлення. Запропоновані у якості ефективних матеріалів для виготовлення виконавчих рушійних елементів морських суден алюмінієві бронзи з аргументовано обґрунтованою кількістю легуючих домішок.

A Flexible Lunar Architecture for Exploration (FLARE) supporting NASA's Artemis Program

The Flexible Lunar Architecture for Exploration (FLARE) is a concept to deliver four crew to the lunar surface for a minimum of seven days and then return them safely to Earth. FLARE can be implemented whenever the component vehicles are operational. FLARE was developed as an alternative to NASA's Human Landing System (HLS) reference architecture from the Design Analysis Cycle (DAC) #2 created in 2019. The DAC2 guidelines required utilization of the Gateway vehicle in a Near- Rectilinear Halo Orbit (NRHO). Instead, FLARE chooses a Low Lunar Frozen Polar Orbit (LLFPO) for lunar rendezvous of components, and an optional Gateway vehicle. The LLFPO provides a stable orbit that overflies the south pole every 2 h, ensuring easy access to the lunar surface for surface aborts with a much lower propellant requirement than NRHO. The minimum FLARE concept uses one Space Launch System (SLS) launch, one Orion, one European Service Module (ESM), and one human lander (launched on commercial vehicle(s)). FLARE adds the SpaceTug, based upon the mature and successful ULA “Common” Centaur Upper Stage vehicle, with modifications to create an Earth-Moon transfer vehicle. In the FLARE baseline mission, the SpaceTug provides propulsion needed to return the Orion + ESM from LLFPO to Earth. The SpaceTug also provides propulsion to deliver the separate human lander components – the Descent Element (DE) and the Ascent Element (AE) - from Low Earth Orbit (LEO) to LLFPO. The SLS Block 1 then launches the Orion + ESM and completes a rendezvous with the mated DE + AE components in LLFPO. FLARE offers optional phases beyond the baseline mission. The SpaceTug can deliver components of the planned Gateway, including the Power and Propulsion Element (PPE) and the Habitable and Logistics Outpost (HALO), to LLFPO. FLARE provides an option to deliver precursor equipment to the lunar surface to enhance and extend the human mission. With these components, including an inflatable habitation module and airlock, individual crew mobility vehicle(s), an In-Situ Resource Utilization (ISRU) demonstration, and science and technology experiments, the crew can explore and conduct science on the lunar surface for up to 14 days.

Tip to End Analysis of Air Breathing Rotating Detonation Engine System

A discovery was made recently that the heat release would be very efficient if it is associated with detonation phenomenon. A detonation wave imparts high pressure to the products of combustion which in turn produces large propulsive power as a result of expansion through the propulsive element. This kind of pressure gain combustor is a new idea which is going to be incorporated in the futuristic propulsive devices. A representative air breathing propulsive system configuration powered by the continuous detonation wave engine is chosen for the present investigation. This includes understanding of various processes occurring in the air intake, isolator, rotating detonation wave engine and flow expansion system. A detailed numerical modelling and simulation based on steady 1-D flow have been carried out. This analysis gave insight into the overall propulsion system performance taking into consideration of the interaction between various sub systems.

Analytical Framework for Staging of Space Propulsion Systems

Staging of space propulsion systems would allow lifetime limitations inherent to small propulsion systems to be bypassed in order to enable high- capabilities for small spacecraft, in particular mass and volume constrained CubeSats. In addition, staging can be used to provide redundancy in the propulsion system, counteract thruster degradation, or open up new avenues of mission optimization. Analytical approximations are developed in order to provide a computationally simple approach to the design, analysis, definition of propulsion technology requirements, and online autonomous decision making for systems that make use of staging of propulsion elements. In addition, the analytical approximations provide insight into the dependencies of performance metrics on system parameters. Equations are developed for any mission, defined by its , and then specialized for escape trajectories.

About the Operator’s Gaits in the Passive Exoskeleton of the Lower Extremities when Using the Fixed Knee Mode

A dynamic model of motion in the sagittal plane of the passive exoskeleton of the lower extremities, integrated with a similar model of a human operator that determines the movement of the whole structure, is considered. The exoskeleton is designed to help the operator to move additional point load, placed in the "backpack" on the back. The design of the exoskeleton does not have active propulsive elements in the joints; it is endowed with only a semi-automatic system for locking or releasing the knee joints at certain stages of movement, which, however, affect the overall gait pattern. The energy costs and peak values of the control torques that the human operator applies in the process of moving the exoskeleton on certain types of regular, flat, single-support walkings are studied. The results obtained allow us to estimate the effectiveness of the mode of locking-releasing the knee joint used by such devices. Both cases of impact-free transitions to the locked knee mode and transitions accompanied by the occurrence of shock effects in a dynamic system were investigated. In mathematical modeling, the mass inertial characteristics of the human body were taken into account in accordance with the data adopted in anthropology.

Opportunities and challenges for electric propulsion of airliners

The growth of air traffic implies an increase of emissions (greenhouse and ozone depleting gases) from the global air fleet. Innovative solutions are therefore urgently required. Among them, electric aviation is the object of much current interest. The present paper discusses the accompanying opportunities as well as challenges, with a focus on costs and operability. In order to take full advantage of electric propulsion, dedicated airframes are indicated, featuring boundary layer ingestion, distributed propulsion and other elements. Different options for electric propulsion are reviewed, and their pros and cons highlighted. In particular, all electric aircrafts suffer from severe range limitations, turbo electric aircrafts become appealing only if fed with liquid hydrogen (with the accompanying problems), while hybrid-electric aircrafts can lead to a somewhat reduced wing area (then weight). Other economical and operational issues are also considered, including cost per kWh (however shown to be a misleading indicator) and that per unit payload mass, maintenance, sources of electric energy for recharge.

Opportunities and challenges for electric propulsion of airliners

The growth of air traffic implies an increase of emissions (greenhouse and ozone depleting gases) from the global air fleet. Innovative solutions are therefore urgently required. Among them, electric aviation is the object of much current interest. The present paper discusses the accompanying opportunities as well as challenges, with a focus on costs and operability. In order to take full advantage of electric propulsion, dedicated airframes are indicated, featuring boundary layer ingestion, distributed propulsion and other elements. Different options for electric propulsion are reviewed, and their pros and cons highlighted. In particular, all electric aircrafts suffer from severe range limitations, turbo electric aircrafts become appealing only if fed with liquid hydrogen (with the accompanying problems), while hybrid-electric aircrafts can lead to a somewhat reduced wing area (then weight). Other economical and operational issues are also considered, including cost per kWh (however shown to be a misleading indicator) and that per unit payload mass, maintenance, sources of electric energy for recharge.