Lightweight is a substantial theme in the research and development of aerospace and aeronautical equipment due to its decisive impact on the comprehensive performance and operational efficiency of the equipment. Over the past decades， a handful of innovative optimization design approaches， emerging high-performance materials， and revolutionary manufacturing technologies have been uninterruptedly developed， and the level of lightweighting in aerospace and aeronautical equipment has been significantly advanced. However， the increasing demands for comprehensive performance and multifunctionality of the next generation of equipment present serious challenges to existing lightweight design and manufacturing technologies. Therefore， with a particular emphasis on the layout design， electromechanical system design， materials and structures， high-performance manufacturing and assembly， this paper analyzes the posed challenges and future perspectives.

The future operational environment imposes higher and more comprehensive requirements for the performance of fighters， calling for deeper integration between fighter airframe and engine and closer collaborative design during fighter research and development. Building on theories and practices for optimum airframe-engine integration in fighter design in the past decades， this paper proposes a collaborative airframe-engine design concept. Through an analysis of the combat requirements of Penetrating Counter Air （PCA） and other operational concepts， this paper then presents the essential capabilities of high performance fighters and looks into the requirements of future-oriented collaborative airframe-engine design. The key technologies concerning flight performance， stealth characteristics， flight control and aircraft energy are discussed， and the possible implementation approaches and suggestions for design and research are also provided.

The future battlefield is confronted with the problems such as high complexity of the environment， strong antagonism of the game， high real-time response， information incompleteness， and boundary uncertainty. To win the future aerospace battlefield， the manned/unmanned aerial vehicle cooperative combat system can become the core key due to its advantages of dual effectiveness， complementarities of combat weaknesses， and high efficiency of action coordination. This paper focuses on the research status of Manned/Unmanned Aerial Vehicle （MAV/UAV） cooperative combat， which is a new direction of high difficulty， rapid development， broad prospects in applications and multidisciplinary combat. The research status of manned/unmanned cooperative combat is summarized from three aspects： system concepts， key technologies and challenges. The definitions of system combat， winning mechanism and application process and the key technologies such as detection and situational awareness， mission planning， command and decision making， formation control， and effectiveness evaluation are expounded. Finally， the challenges of MAV/UAV cooperative combat in the future battlefield are prospected， and new ideas for the development of intelligent combat technology in the future are provided.

Morphing aircraft， capable of real-time shape deformation according to task requirements and flight conditions to achieve optimal flight performance， has emerged as a significant direction for the future development of aircraft. This paper reviews the research status of deformation modes and key technologies of aerodynamic layout design for morphing aircraft. Firstly， the development of morphing aircraft can be divided into two stages by the progression of time： the mechanical deformation stage and the flexible and muti-dimensional deformation stage. Then， this article summarizes morphing solutions for different parts of the aircraft， namely， the head deformation， wing deformation， power plant deformation， and combined deformation. It particularly explores the developmental history of various wing morphing schemes， discusses their applications in different aerodynamic configurations including variable sweep wing， variable forward sweep wing， folding wing， telescopic wing， oblique wing， continuous variable curvature wing， and analyzes their aerodynamic and stability characteristics， respectively. Next， the implementation objectives of morphing aircraft are summarized and divided into three types： single domain optimal variable configuration， multi-domain fusion variable configuration， and one vessel multi-energy variable configuration. Subsequently， compared with fixed shape aircraft， the key technical challenges in aerodynamic layout and overall coordination design， time-varying aerodynamic effect evaluation， aerodynamic layout scheme optimization， and multidisciplinary coupling design derived from the implementation of morphing aircraft are analyzed， with particular focus on the research progress and current status of dynamic aerodynamic calculation methods and aerodynamic optimization design technologies for morphing aircraft. Finally， the future research direction and development prospects of morphing technologies are envisioned. Targeting at the needs of wide velocity domain and large airspace flight， exploring new conceptual deformation methods that can improve the performance of multiple flight missions and establishing intelligent morphing design model and multidisciplinary strong coupling integrated design system will become important development trends.

Technological breakthroughs have once again spawned a lot of attention to the commercialization of Urban Air Mobility （UAM） in urban low-altitude airspace. The urban low-altitude airspace environment is complex， the density of urban air traffic flow in commercial scenarios is high， and the specifications of vehicles are not uniform. As a new infrastructure for UAM， low-altitude public routes are an important means for UAM to carry out refined management. However， the planning methods of low-altitude public routes， the required infrastructure， and the urban air traffic operation and control mode are still unclear. In response to the above issues， this article sorts out the basic concepts and development history of UAM and low-altitude public air routes， as well as UAM management based on low-altitude public air routes； In addition， an UAM operation management framework is proposed. Suggestions and countermeasures are provided on the possible responsibilities of relevant administrative departments in the development UAM； Finally， the construction method of low-altitude public routes network， the difficulties in the development process of UAM and implementation suggestions are summarized， in order to shed light on the healthy and orderly development of the UAM.

With the increasing convenience of data acquisition for aerial photography of Unmanned Aerial Vehicle （UAV）， the multi-target detection and tracking technology based on the UAV platform has developed rapidly and has broad prospects for applications in civil and military fields. In recent years， the rapid progress of in-depth learning has also provided a variety of more effective solutions. However， the challenging problems such as sudden changes in the appearance of the target， serious occlusion of the target area， and disappearance and reappearance of the target from the perspective of UAV have not been completely solved. In this paper， we summarize the algorithms for multi-target detection and tracking in UAV aerial video based on deep learning， and summarize the latest progress in this field， including multi-target detection and multi-object tracking. The multi-object detection module is divided into two parts： two-stage and one-stage detection. For the multi-object tracking module， according to the two classical frameworks of tracking-based detection and joint-detection tracking， the principles of the two algorithms are described and their advantages and disadvantages are analyzed. Then， the existing public data sets are statistically analyzed， and the optimal schemes of the benchmark challenge VisDrone Challenge in the field of multi-target detection and tracking based on UAV aerial video in recent years are compared and analyzed. Finally， the paper discusses the urgent problems of multi-object detection and tracking from the perspective of UAV and the possible research directions in the future， providing a reference for the follow-up researchers.

Since the 1950s， scramjet has been regarded as a goal of the hypersonic propulsion system in the aerospace field， and extensive research work has been conducted in both theory and practical technology. At the beginning of the 21st century， the United States made a series of technological breakthroughs close to practical applications， pushing the research and application of the scramjet technology to a new stage. This paper briefly describes the working principle of the scramjet， discusses the difficulties and latest progress in key technologies such as dual-mode working process， hypersonic compression flow， supersonic combustion， ultra-high temperature structure and thermal protection， ground test and numerical simulation， and expounds the understanding and suggestions on the development direction of key technologies such as wide speed range， repeatability， and higher Mach number of scramjet.

Aeroengine amalgamates state-of-the-art technologies across diverse domains， serving as a comprehensive manifestation of a nation’s prowess in science and industry. Frequent malfunctions occur due to its complicated structure and harsh service environment. Therefore， it is essential to employ prognostic and health management technology to provide crucial support for aviation safety and reliable operations. As vibration faults constitute a primary failure mode in aeroengine， this paper， grounded in this premise， systematically reviews and analyzes existing vibration monitoring and fault diagnosis for aviation engines both domestically and internationally. The analysis is categorized into three dimensions， covering the application of overall vibration monitoring and diagnostic systems， typical fault characteristics and diagnostic methods， and the overall vibration fault diagnostic technology， including dynamic analysis， signal processing techniques， and relevant technologies such as deep learning. Then， the problems and challenges faced by the existing vibration fault diagnosis of aeroengine are identified. Furthermore， future development goals are provided.

The concepts of collaborative combat Unmanned Aerial Vehicles （UAVs） have been widely discussed in recent years. Entities such as the United States， Russia， and Europe are competing in the development of UAVs featured by enhanced collaboration and high performance. A cutting edge hotspot for investigation on the corresponding key technologies is forming in the region of aviation equipment. The differences in usages， mission capabilities， and technological features of collaborative combat UAVs compared to traditional UAVs have sparked new discussions and reconsiderations. This paper traces the evolution history of military UAVs by focusing on the transformation of human-machine relationships and the expansion of UAVs’ capabilities. The development requirements emerged in the context of great power competition for future UAVs， as well as the capability demands and key technologies which give definitions on high-performance collaborative combat UAVs， are analyzed. Moreover， the design orientations that worth attention， such as autonomy/collaboration， decentralization/centralization and high performance/low cost， are discussed. Recommendations for future development of high-performance collaborative combat UAVs are also proposed.

Multi-scale structure is one of the important directions of next-generation structural lightweighting and has great potential and strategic value for application in the aerospace field. Topology optimization techniques for multi-scale structures have also been extensively researched， leading to great progress and achievements. However， many challenges and difficulties remain before realizing actual engineering practice. This paper firstly introduces the mainstream methods and characteristics of single-scale structural topology optimization， the basic idea and special position of homogenization methods， as well as the relationship between topology optimization methods for multi-scale structures and topology optimization methods for single-scale structures. Then， using the structural distribution characteristics as the classification criteria， this paper systematically sorted out the topology optimization design methods for three distribution forms of multi-scale structures： periodic， functional gradient and heterogeneous. For the important issues， including structural connectivity， applicability of multi-scale methods， and application of machine learning technology in multi-scale structural topology optimization， relevant research progresses are reviewed and discussed. Finally， pressing challenges and important research directions in the field are summarized and prospected.

The development of electric Vertical Take-off and Landing （eVTOL） aircraft is greatly promoted for the advances in battery and motor technologies and the application of distributed electric propulsion system. In this paper， the advantages and disadvantages of different eVTOL configurations and their application scenarios are summarized， and a comprehensive comparison between eVTOL and conventional fuel aircraft is made in terms of performance， noise and cost. The interaction noise by rotors and rotor-wing is more prominent for eVTOL， but the electric propulsion rotor system with low tip speed and large rotor solidity greatly reduces its noise level （about a reduction of 15 dB）. Lithium-ion batteries are the main energy source for current and future eVTOL. The advanced battery material system， integrated design of battery-structure and excellent battery management system are effective ways to improve the energy density and energy security of the whole aircraft in the future. The redundant manipulation of eVTOL increases the difficulty of flight control system design， but improves the safety of the whole aircraft at the same time. Fault reconstruction and collaborative control are new challenges faced by eVTOL. A wide variety of configurations and novel design features such as high voltage power， electric propulsion， flight-by-wire flight system and electric actuation are proposed for eVTOLs. In the absence of flight test data， the system-based method is the main method for safety design of eVTOL.

Low-Altitude Intelligent Network （LAIN）， as a new type of intelligent network， relies on space-air-ground-sea facilities to constitute a digital intelligent network system. It is a key component of the space-air-ground integrated network， and can support the seamless and ubiquitous connections of the sixth generation communication technology and promote the development of intelligent network service from ground to low-altitude space. However， LAIN is still in the developing stage and faces the following key challenges： intractability of aerial control， severe spectrum interference， and multi-dimensional resource limitation. This article focuses on the issues of LAIN architecture and safety control， including the current development status of low-altitude network and its significance for industrial technology transformation. Then， from the perspective of spectrum resources， network resources， and airspace resource management， the recent related works are analyzed. Furthermore， we analyze the key technologies such as low-altitude aircraft air-ground spectrum sharing， sensing， transmission， computing networking coverage， low-altitude airspace intelligent supervision， and point out future development directions. Finally， an application demonstration of LAIN is proposed， aiming to satisfy the significant requirements for efficient operation and safety in low-altitude airspace， and providing the theoretical basis as well as technology for the further development of the next generation space-air-ground integrated network.

As an important part of aero engine， blade damage and maintenance have an important impact on aircraft operation safety and operating cost. To improve the maintenance quality and efficiency， scholars at home and abroad have carried out considerable theoretical and technological research on blade maintenance. To further analyze the maintenance process of damaged blades， firstly， the damage types and causes of fan blades， compressor blades， turbine blades and integral disk blades were summarized， and the maintenance technical routes under different damage conditions were analyzed in detail. The research field of in situ maintenance is weak. Therefore， the related technology and equipment of in situ maintenance are explained in detail， as well as the related optimization method and the application of new technology. Finally， the research and development direction of aero engine blade maintenance are prospected， which can provide reference for future researchers in this field.

Reusable launch vehicles are an important way for humans to enter and exit space on a large scale and at a low cost. Starting from the technical requirements of vertical takeoff and landing reusable launch vehicles， this paper summarizes the technical challenges faced by vertical takeoff and landing reusable launch vehicles， and analyzes the key technologies of vertical takeoff and landing reusable launch vehicles. The research progress and future development directions of key technologies for vertical takeoff and landing reusable launch vehicles are then discussed in terms of overall optimization design， power， structure and thermal protection， navigation， guidance and control， and health management， which can provide reference for the technical research of reusable launch vehicles.

Hydrogen fuel has significant importance in mitigating global climate change and protecting the environment by achieving zero carbon emission in aviation engines， aerospace propulsion engines， and ground gas turbines. However， the application of hydrogen combustion technology still faces many challenges. Hydrogen combustion in traditional burners poses a risk of flashback and high nitrogen oxide （NO _x ） emission. Thus， it requires exploration of new combustion technologies and pollution control measures to satisfy the urgent need of hydrogen energy. Micromix combustion technology implements hundreds of microchannels combined with micro-injection of hydrogen to rapidly mix air and hydrogen to form small-scale flames. The residence time of N₂ in the high-temperature zone is shortened to the level of milliseconds， significantly reducing the production of nitrogen oxide. This paper reviews the application history of hydrogen in gas turbine engines and the progress of hydrogen combustion simulation and experimental studies， summarizes the hydrogen characteristics， NO _x generation mechanism， micromix combustion principle， premixed combustion， diffusion combustion and dome structure characteristics， and discusses the influence of critical parameters of micromix combustors on aerothermodynamic process， NO _x generation and control measures， providing theoretical and empirical bases for the engineering design of hydrogen combustion chambers. Finally， the future development of hydrogen combustion technology is prospected.

With the development and application of artificial intelligent technologies in the military field， future intelligent warfare is to demonstrate the following traits： more complex cognition and decision making， more rapid changes and evolution， and access and denial in the whole warfare. The next-generation flight vehicles will be flight-demand oriented， artificial-intelligence centered， and changing flexible. Smart morphing aircraft， obviously characterized by intelligent technology and deformation technology， can have dual advantages of fast algorithm upgrades and extremely flexible hardware. It introduces new flight modes and combat capabilities， and will therefore become an important trend. However， smart morphing aircraft design requires complicated technologies. The costs of deformation， such as the increased complexity of the machine system， pose challenges to aerodynamic design， flight control， and structural implementation. The challenges include the full-profile optimization， structural application， and performance prediction and validation in the deformation process， where the core problem is to achieve the optimal design in each shape in the context of multidisciplinary engineering.

Small object detection in UAV aerial images based on deep learning has a wide range of applications in military intelligence reconnaissance， battlefield surveillance and assessment， military object capture and verification， intelligent traffic management， infrastructure inspection and maintenance， disaster prevention and control， search and rescue， crop management and analysis， ecological protection and monitoring and other fields， and has become a current research hotspot in recent years. This review article gives a comprehensive and in-depth investigation on small object detection in UAV aerial images based on deep learning in the past five years. First of all， the definition and challenges of small object detection in UAV aerial images are introduced. Secondly， small object detection methods in drone aerial images are summarized in terms of discriminative feature learning， super-resolution technology， real-time lightweight detection， and other improvement ideas. Then， small object detection datasets of UAV aerial images are systematically summarized， and the performances of different algorithms are analyzed based on the VisDrone Challenge. Finally， the specific applications of small object detection in UAV aerial images in the military and civilian fields are comprehensively presented， and the potential future development directions of small object detection in UAV aerial images and some concerns about UAV aerial photography are also discussed. It is expected that this review would inspire relevant researchers to further promote the development of small object detection in UAV aerial images based on deep learning.

With the rapid development of intelligent UAV technology， UAVs have the vast prospects in many fields， such as smart agriculture， post-disaster rescue， and battlefield reconnaissance. However， the limited perceptual and computing capabilities of an individual UAV make it difficult to meet the complex environment and task requirements in practice. Therefore， the efficient collaborative perception and computation of UAV swarms have become the main development direction in the future UAV field. In this paper， we first present the basic concepts of collaborative perception and collaborative computation. For the collaborative perception， we review the latest progress in swarm perceptual data collection and collaborative perception strategy. For the collaborative computation， the optimal schemes of computation task scheduling， resource allocation and data catching are summarized and compared. In addition， we discuss the urgent problems of collaborative perception and computation from the perspective of UAVs. Some potential research directions are presented， providing a reference for the follow-up researchers.

Bird Inspired Flapping-wing Micro Aerial Vehicles （BIFMAVs） have great development potential in terms of flight efficiency， stealth， and maneuverability， exhibiting high research value and application prospects. This article mainly reviews the research and development progress of BIFMAVs over the past 20 years， summarizing and analyzing the current state of research on their overall design methods， aerodynamic analysis methods， and key technologies of the driven system and the flight dynamics and control. The characteristics and developmental trends of， and the challenges faced by each technology are presented， and the prospects for the future development direction of BIFMAVs are ultimately proposed. By providing a comprehensive review of the current state of research and development direction of key technologies for BIFMAVs， it can serve as a reference for subsequent researchers working in this field.

Image matching is a key technology in aircraft visual navigation. The image matching methods based on deep learning have developed rapidly in recent years. The feature extraction network of the methods has obvious advantages over traditional methods， and has broad prospects for application. The image matching method based on deep learning can be divided into the single-link matching network model method and the end-to-end matching network model matching method according to different network structures. In this paper， the feature detection， descriptor learning， similarity measurement and error elimination network model of the network model of the single-link matching method network model are first investigated and analyzed. Then， the single-network structure method and multi-network structure combination method in the end-to-end matching network model are reviewed， and the classic end-to-end matching network model algorithm is introduced and analyzed. Finally， the problems of current image matching methods based on deep learning are pointed out， and the possible development trend and direction in the future are discussed to provide a certain reference for subsequent research on deep-learning based image matching.