Progress in Aerospace Sciences最新文献

In recent years, the realm of space exploration has undergone a transformative shift, marked by the emergence of a thriving new space economy. This evolution has not only redefined existing space infrastructures and services but has also democratized access to space, accelerating exploration endeavors. At the core of such evolution is additive manufacturing (AM), a groundbreaking technology that has fundamentally altered the landscape of designing and producing launchers and space systems. AM not only enhances the efficiency of existing space missions but also unlocks novel avenues for space exploration and the establishment of sustainable human settlements beyond Earth. This paper provides a comprehensive and current exploration of the industrial catalysts driving AM adoption across key space domains. It delves into existing applications and uncharted frontiers, exploring innovative advancements while spotlighting industry gaps and obstacles. Motivated by the maturation of AM technologies, the proven track record of additively manufactured components in space missions, and the surge in research and investments aligning with major space market trends, this paper aims to provide aerospace and manufacturing communities with a panoramic view of present and future opportunities for AM within the rapidly expanding new space economy. Additionally, it sheds light on the profound impact and momentum gathering in this field, all the while examining the significant challenges that demand concerted attention.

Advanced Air Mobility (AAM) represents a collaborative vision shared by NASA, regulatory agencies, and global industry leaders, aimed at establishing a robust and reliable air transportation ecosystem, which is expected to facilitate safe and efficient movement of both people and cargo within urban, suburban, and regional environments. This paper presents a holistic review and analysis encompassing various aircraft designs, including different propulsion system designs and architectures (electric, hybrid electric, turboelectric, etc.), for different AAM aircraft applications, and state-of-the-art air traffic management, cybersecurity, and infrastructure strategies. Recent academic and industry literature on these aspects is critically reviewed and summarized, and a compilation of the aircraft models currently in development is also provided. The aircraft designs are categorized into a set of core groups, which include lift + cruise, tilt-wing, tiltrotor, multirotor, and rotorcraft, to analyze the existing literature systematically. For each of these core groups, literature on different propulsion system designs and architectures is reviewed and analyzed. Next, these core groups, including their variations based on propulsion system designs and architectures, are analyzed through a set of evaluation lenses. This provides a comprehensive insight into their respective strengths, weakness, and gaps in design considerations. The identified lenses include range and payload, performance, environmental impact, feasibility, traffic and infrastructure, noise, vehicle safety, and cybersecurity. Finally, directions for future research in AAM aircraft and overall ecosystem development are identified. In general, a more in-depth, quantitative analysis on the various evaluation lenses identified in this study and appropriate consideration to all these evaluation lenses at the design and development stage are highly recommended. This type of holistic approach will drive AAM aircraft designs towards convergence and help build an efficient, affordable, and sustainable AAM ecosystem.

The main goal of this paper is to present a vision for the future of aviation. Developing such a vision is always a complex matter, but in times of environmental emergencies and unjustifiable wars it becomes even more difficult. One of the main reasons of this paper is to show that there is still room for advancing clean technology developments and to demonstrate that the aviation sector is ready for embarking on new challenge.

Green and environmentally sustainable aviation, in our opinion, can be achieved with continuous improvements along multiple parallel paths, ramp up of SAF (Sustainable Aviation Fuel) production, and of course, breakthrough technologies. The latter will require a significant amount of research, testing and probably mistakes need to be made before reaching the level of transportation efficiency and mission safety obtained with traditional propulsion, but these drawbacks should only encourage scientists, engineers, politicians and visionaries to strongly pursue the objectives of a new eco-aviation.

Aviation decarbonization requires a strategy change from near term improvements in aircraft fuel efficiency to long term (from neutral to zero carbon emissions) fuel switching. The successful introduction of long-term solutions requires transdisciplinary research into technological, operational and economy fields.

New technologies should probably be introduced into smaller aircraft segments first then migrate into the larger segments as the technologies mature. We should expect a first electric and hydrogen fuel cell commuter aircraft entry into service by the end of this decade, with hydrogen combustion-powered narrow bodies around 2040.

In 2019, aviation accounted for approximately 2.3% of global greenhouse gas emissions, with global commercial fleet CO₂ emissions totaling 0.918 Gigatonnes. Narrowbody and widebody aircraft produce over 95% of the industry's greenhouse gas emissions, therefore, while the introduction of new technologies on smaller aircraft will be important for the development of sustainable solutions, they will have minimal impact on the overall carbon footprint until they make their way onto larger platforms. However, carbon-free fueled (electric, hydrogen) aircraft will require significant infrastructure investments to develop the novel transportation network and the re-fueling procedures that will be required to support their use. Therefore, their success will require the coordinated combined efforts of the entire industry (airlines, airports, air navigation service providers, manufacturers) and significant government support.

This paper tries to summarize the most important aspects for a vision on sustainable green aviation and to indicate a possible roadmap for reaching this goal.

Sustainability has recently been identified as the greatest challenge facing the modern aviation field. Given the extreme power and energy characteristics of transport-class aircraft today,achieving sustainability goals across the aviation sector is a tremendous challenge when compared to other modes of transportation. Several key energy carriers have emerged, promising an environmentally sustainable aviation future. Those considered here include bio-jet fuel pathways for synthetic kerosene, power-to-liquid pathways for synthetic kerosene, liquid hydrogen, ammonia, liquid natural gas, ethanol, methanol, and battery electric systems, all of which are compared to conventional fossil-derived aviation turbine fuel. However, these alternate energy carriers bring forward significant technoeconomic considerations that must be addressed before such approaches can be viably implemented. These factors include material properties impacting aircraft performance and fuel handling, emissions, cost and scalability, resource and land requirements, and social impacts. The purpose of this review is to provide a summary of current approaches to alternative aviation energy carriers, which includes a discussion of key advantages, challenges, and implications determining the future viability of each approach. It is found that bio-jet fuels, power-to-liquid synthetic kerosene, liquid natural gas, and liquid hydrogen all have technical feasibility and can contribute to improved environmental outcomes. However, hydrocarbon fuels and non-renewable production pathways for carbon-free energy carriers are not viable permanent solutions for a fully sustainable aviation ecosystem. As a result, potential transition scenarios from fossil-derived aviation turbine fuel to synthetic kerosene, with simultaneous development for adoption of liquid hydrogen and battery-electric systems, are recommended.

The continuously increasing interest in alternative aircraft propulsion systems is caused by the requirements and demands set by international institutions and government organizations. For instance, nowadays in the European Union, the objective called the European Green Deal seems most demanding. According to this regulation, the members of the European Union should ensure the net zero emission of greenhouse gases by the year 2050. This is why many efforts are devoted to finding ecological solutions for the aviation sector which almost completely relies on fossil fuels at the moment. One of the solutions, which has already proved beneficial for the automotive industry, is the hybrid gas-electric propulsion. Combining the advantages of the electric motors and batteries with the Internal Combustion Engines (ICE) creates an opportunity to reduce fuel consumption, thereby decreasing the greenhouse gas emission. However, challenges such as the immature batteries technology, complicated power management system or the cooling system for high power propulsion systems, among others, need to be dealt with. These all offer great potential for scientific studies, thus the associated literature is accumulating very quickly. The aim of this paper is to update the status and review the state of the art concerning aircraft with hybrid gas-electric propulsion systems. However, the other alternative propulsion systems are also described to indicate and emphasize drawbacks and benefits coming from the hybrid gas-electric propulsion.

Civil aviation provides an essential transportation network that connects the world and supports global economic growth. To maintain these benefits while meeting environmental goals, next-generation aircraft must have drastically reduced climate impacts. Hydrogen-powered aircraft have the potential to fly existing routes with no carbon emissions and reduce or eliminate other emissions. This paper is a comprehensive guide to hydrogen-powered aircraft that explains the fundamental physics and reviews current technologies. We discuss the impact of these technologies on aircraft design, cost, certification, and environment. In the long term, hydrogen aircraft appear to be the most compelling alternative to today’s kerosene-powered aircraft. Using hydrogen also enables novel technologies, such as fuel cells and superconducting electronics, which could lead to aircraft concepts that are not feasible with kerosene. Hydrogen-powered aircraft are technologically feasible but require significant research and development. Lightweight liquid hydrogen tanks and their integration with the airframe is one of the critical technologies. Fuel cells can eliminate in-flight emissions but must become lighter, more powerful, and more durable to make large, fuel cell-powered transport aircraft feasible. Hydrogen turbofans already have these desirable characteristics but produce some emissions, albeit much less damaging than kerosene turbofans. Beyond airframe and propulsion technologies, the viability of hydrogen aircraft hinges on low-cost green hydrogen production, which requires massive investments in the energy infrastructure.

This paper investigates the potential pathways and associated requirements to meet a goal of net-zero greenhouse gas (GHG) emissions from the US commercial aviation sector by 2050 as outlined in the US 2021 Aviation Climate Action Plan. Aviation traffic (RTK) is projected to grow at an average of 2.0% per annum between 2019 and 2050, suggesting that a progressive and ultimately total decoupling of emissions from traffic growth will be required to meet the US aviation sector goal. Aircraft technology advancements, operational efficiency improvements, sustainable aviation fuels, and market-based measures (MBM) are considered as emissions reductions measures towards the goal. A parametric analysis framework is used to develop low, medium, and high emission reduction scenarios for each of these emissions reduction measures. If aircraft technology, operations, and fuels were frozen at 2019 levels, the aviation sector is projected to emit ≈430 million tonnes of CO₂ (MtCO₂) in 2050. Retirements of older aircraft, replaced by current-generation alternatives, may contribute 17% of the total 2050 emissions reduction goal. Further introduction of advanced aircraft technologies may contribute an additional system-level 11% emissions reductions towards the goal. Operational improvements may contribute ≈2% with a range from 1.5 to 4%. The remaining 70% of emissions in 2050 will be addressed through a combination of sustainable fuels and MBM, where appropriate. The level of contribution from fuels will be dependent on continued production ramp-up to meet aviation demand as well as improvements in lifecycle emissions reduction factor (ERF) for current and future fuel feedstock and production pathways, ranging from 0% for current petroleum-based fuels to 100% for sustainable aviation fuels with zero life-cycle emissions. Meeting a net-zero emissions goal by 2050 with SAF would require an increase in SAF production by 57% annually from 2022 to 2030 and 13% per year thereafter, reaching 100% emissions reductions factor by 2050. MBM may fill the gap between residual lifecycle emissions after accounting for all other in-sector improvement opportunities and the goal.

Reducing greenhouse gas emissions has become a priority for civil transport aviation. One of the possible solutions investigated by current aeronautics research is the introduction of electric propulsion, which would drastically reduce greenhouse gas emissions related to flight. This paper addresses this topic in depth; the work is structured in two intertwined parts. The first relates to an extensive review of the state of the art, starting with the analysis of electrical technology enablers for aviation applications, and leading to the investigation of current proposals of aircraft conceptual designs, both for short-medium range and regional class. This review section, which is presented with a critical approach, provides the relevant indications for the definition of the technical framework of the second part of the paper, in which the conceptual development of a novel hybrid-electric aircraft is proposed. Specifically, the outcomes from the analysis of the state of the art suggest that the hybrid-electric aircraft should belong to the regional category, and that energy efficient solutions for the airframe should be considered. Moreover, potentials and limitations of integrating hybrid-electric propulsion are carefully detailed, and reasonably realistic technology levels for the next decade have been selected for the design of the proposed aircraft. A box-wing airframe architecture has been adopted as it has the potential to minimize induced aerodynamic drag while increasing the load transport capacity, thus representing an aerodynamic efficient solution. A design and optimization framework has been developed to evaluate the integration of the hybrid-electric propulsion with the box-wing lifting system. The coupling of these two technologies, together with a paradigm change in the aircraft design approach, allow to identify conceptual solutions that minimize fuel consumption throughout the typical regional mission envelope, leading to a potential emission-free regional aircraft.

The continued emission of greenhouse gases presents an existential threat to civilization on our planet. Although the aviation sector of the global economy contributes only a small percentage of the total greenhouse gas emissions it will become increasingly important to decarbonize this sector no later than 2050 if the danger of irreversible climate change is to be averted. In this special issue an attempt is made to provide the readers of ‘‘Progress in Aerospace Sciences” with easy access to the views of twentyfive active researchers in the field of sustainable aviation in eight comprehensive review papers on the current status and the challenges to achieve the transition to green aviation by mid-century.

The use of fossil fuels, which are employed to supply the energy needs of aircraft, is currently causing severe environmental concerns, placing pressure on the aviation industry and mandating specific action. Sustainable aviation fuels that would lessen the aviation industry's environmental effects are viewed as a potential substitute for fossil fuels. Hydrogen, a clean energy carrier, is regarded as the most promising of these fuels. This paper provides a historical overview of hydrogen-powered aviation, as well as an analysis of the hydrogen supply network, which is regarded as a critical component. As part of the Sustainable Development Goals (SDGs), this study offers a future-oriented concept as well as challenges, prospects, potential future orientation and modifications that can be made to the hydrogen supply network for full decarbonization.