Aerospace Systems Research Articles

Deep learning-based inverse design of microstructured materials for optical optimization and thermal radiation control

Microstructures with engineered properties are critical to thermal management in aerospace and space applications. Due to the overwhelming number of microstructure design variables, traditional approaches to material optimization can have time-consuming processes and limited use cases. Here, we combine a surrogate optical neural network with an inverse neural network and dynamic post-processing to form an aggregated neural network inverse design process. Our surrogate network emulates finite-difference time-domain simulations (FDTD) by developing a relationship between the microstructure’s geometry, wavelength, discrete material properties, and the output optical properties. The surrogate optical solver works in tandem with an inverse neural network to predict a microstructure’s design properties that will match an input optical spectrum. As opposed to conventional approaches that are constrained by material selection, our network can identify new material properties that best optimize the input spectrum and match the output to an existing material. The output is evaluated using critical design constraints, simulated in FDTD, and used to retrain the surrogate—forming a self-learning loop. The presented framework is applicable to the inverse design of various optical microstructures, and the deep learning-derived approach will allow complex and user-constrained optimization for thermal radiation control in future aerospace and space systems.

Electrically Insulative Film Adhesive with Enhanced Thermal Performance to Assemble High Power Density Electronic Devices

Assembly adhesives play a critical role in microelectronic packaging and contribute significant value for circuit assembly interconnection, protection, and thermal management. Of particular interest with today’s more powerful systems is thermal management of high-power density electronic systems, including power modules, power amplifiers, communication systems, and directed energy systems. As requirements for performance and functionality increase, heat generated from these devices increases exponentially. For example, local heat flux can easily exceed 50 W/cm2 for IGBT power modules while it may reach several hundred Watts/cm2 at active areas for Gallium Nitride (GaN) power amplifiers. Simultaneously, many of these systems demand a higher level of electrical insulation to eliminate or minimize current leakage to ensure high reliability over a long service life. Effectively and safely dissipating the high heat and ensuring excellent electrical insulation has become an increasingly critical and challenging task in the microelectronics packaging technology for aerospace and defense systems. This paper presents integration of thermally conductive adhesives with an electrically insulative polyimide film into a carefully engineered laminate, which enables high thermal transfer and robust electrical insulation. This new film adhesive provides outstanding compliance and augmented tolerance to large topographical features and warpage (5-7 mils). This film adhesive is one of the potential solutions to addresses the evolving needs of the electronics assembly industry in the areas of management of high-power systems

A Hybrid Pressure-less Silver Sintering Technology for High-power Density Electronics

Integration of smaller, higher-functioning devices and use of advanced high thermal chip structures present thermal management challenges in the aerospace sector where reliability is the top priority and fail-safe processes/materials are the standard. As power density increases rapidly, traditional die attaching technology is becoming an increasingly limiting factor in microelectronics packaging for the next generation aerospace and defense systems. This paper introduces an advanced hybrid silver sintering technology, which incorporates ultra-high thermal and electrical performance of silver sintering with high reliability and process friendly of epoxy-based die attach technology. Unlike traditional silver sintering that requires high temperature and pressure, this hybrid sintering paste can be processed without applying any pressures in temperature ranges that are normal in microelectronics packaging processes. This paper presents results of an application study aimed at developing this unique technology in the field of high-power density devices for aerospace applications.

Formal Verification of Safety-Critical Aerospace Systems

Developments in autonomous aircraft, such as <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">electrical vertical take-off and landing</i> (eVTOL) vehicles and multicopter drones, raise safety-critical concerns in populated areas. This article presents the ASSURE ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"/> <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">A</b> <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">nalysis of</i> <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</b> <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">afety-Critical</i> <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</b> <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ystems</i> <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">U</b> <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sing Formal Methods-Based</i> <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</b> <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">untime</i> <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E</b> <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">valuation</i> ) framework, which is a collection of techniques for aiding in the formal verification of safety-critical aerospace systems. ASSURE supports the rigorous verification of deterministic and non-deterministic properties of both distributed and centralized aerospace applications by using formal theorem proving tools. We present verifiable algorithms and software, formal reasoning models, formal <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">proof libraries</i> , and a data-driven runtime verification approach for aerospace systems towards a provably safe <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Internet of Planes</i> (IoP) infrastructure.

The history of flight safety: methodology, experience, prospects

The formulation of the flight safety history problem is stated. The article shows that it is problematic to scientifically substantiate, systematize, analyze and generalize the theoretical and empirical flight safety material accumulated in various fields. From a historical perspective, the necessity for a socio-humanitarian assessment of the transformation processes of scientific and applied experience in the field of flight safety is substantiated. New multidisciplinary line of research, making use of a specific scientific apparatus and methodological tools, i.e., the history of flight safety, the subject basis of which covers social activities throughout the life cycle of all aerospace engineering (artificial flying objects in the Earth's atmosphere and space, aircraft, crews, passengers, other aerospace system specialists), including aeronautics, aviation, cosmonautics over a span of the entire history of mankind, is proposed. A brief overview of publications on the issue of flight safety is offered. The experience of flight safety history research is analyzed. The periodization of flight safety history in the XX–XXI centuries, giving prominence to three stages: 1. Generating ideas, technologies, flight safety systems (10–40s of the XX century). 2. Establishing the national and international systems to ensure flight safety, scientific research, personnel education and training in the field of flight safety (50–80s of the XX century). 3. Developing new ideas, technologies, projects, flight safety management systems, active ensuring of flight safety, etc. (since the 90s of the XX century), is proposed. The foundations of the conceptual model of the flight safety history are presented, the methodology, experience and prospects of research are considered. It is recommended to organize systematic studies of the flight safety history, covering the aspects of the world and domestic science, education and practice; to create a unified information system on the history of flight safety based on new information technologies, the ultimate aim of which can be a virtual worldwide museum of flight safety; to initiate a pilot project of the National Flight Safety Museum of Russia and to start its development in the year of the 100th anniversary of our civil aviation; in the future, to develop a new academic discipline "History of Flight Safety" for training aerospace industry specialists and researchers.

TECHNICAL AND ECONOMIC SUBSTANTIATION OF THE AIR LAUNCH AEROSPACE SYSTEM PARAMETERS

The substantiation of the technical and economic parameters of the air launch aerospace system, which consists of a reusable unmanned aerial vehicle and integrated launch vehicle, is given. A combination of a turbofan engine and a ramjet engine is used as the unmanned aerial vehicle propulsion system. The considered vehicle is capable of delivering a payload into low-Earth orbits without the use of a spaceport. We have developed the methodology of the technical and economic substantiation of the parameters of the air launch aerospace system. The results were obtained by searching for the minimum of the objective function, which established the relationship between the technical and economic parameters of the aerospace system. For the objective function solution, the design parameters of the integrated launch vehicle and unmanned aerial vehicle were determined, as well as the limitation of the total acceleration velocity of the aerospace system. The methods used allowed us to determine the velocity constraints provided by the operation of the turbofan engine, ramjet engine, and the three solid propellant motors of integrated launch vehicle stages, as well as maximum dynamic pressure and maximum permissible temperature on the unmanned aerial vehicle surface. We determined the scheme for estimating the cost of launching the spacecraft into Earth orbit by the air launch aerospace system. The result of the substantiation is the determination of the technical and economic parameters of the integrated launch vehicle, unmanned aerial vehicle, and the aerospace system as a whole. The influence of the maximum temperature on the surface of the unmanned aerial vehicle and the specific impulse of the ramjet engine on the parameters of the aerospace system was also evaluated. The substantiation is the first step towards the creation of the Ukrainian aerospace air launch system.

Experimental Evaluation of Fatigue Strength of AlSi10Mg Lattice Structures Fabricated by AM

There is evidence that Additive Manufacturing (AM) plays a crucial role in the fourth industrial revolution. The design freedom provided by this technology is disrupting limits and rules from the past, enabling engineers to produce new products that are otherwise unfeasible. Recent developments in the field of Selective Laser Melting (SLM) have led to a renewed interest in lattice structures that can be produced non-stochastically in previously unfeasible dimensional scales. One of the primary applications is aerospace engineering where the need for light weights and performance is urgent to reduce the carbon footprint of civil transport around the globe. Of particular concern is fatigue strength. Being able to predict fatigue life in both LCF (Low Cycle Fatigue) and HCF (High Cycle Fatigue) is crucial for a safe and reliable design in aerospace systems and structures. In the present work, an experimental evaluation of compressive–compressive fatigue behavior has been performed to evaluate the fatigue curves of different cells, varying sizes and relative densities. A Design of Experiment (DOE) approach has been adopted in order to maximize the information extractable in a reliable form.

Theoretical Analysis and Numerical Simulation of the Motion of RDX Deflagration-Driven Flyer Plate Based on Laser-Initiated Micro-Pyrotechnic Devices.

Miniaturized laser-initiated pyrotechnic devices have great application prospects in aerospace and modern weapon systems due to their excellent energy output performance and reliability. In order to develop a low-energy insensitive laser detonation technology based on a two-stage charge structure, it is important to deeply analyze the motion law of a titanium flyer plate driven by the deflagration of the first-stage charge (RDX). The effects of the charge mass of RDX, flyer plate mass, and barrel length on the motion law of flyer plates were studied through a numerical simulation method based on the Powder Burn deflagration model. The consistency between the numerical simulation and the experimental results was analyzed using the paired t confidence interval estimation method. The results show that the Powder Burn deflagration model can effectively describe the motion process of the RDX deflagration-driven flyer plate with a 90% confidence level, and its velocity error is ≤6.7%. The speed of the flyer plate is proportional to the mass of the RDX charge, inversely proportional to the mass of the flyer plate, and exponentially related to its moving distance. As the moving distance of the flyer plate increases, the RDX deflagration products and air in front of the flyer plate are compressed, which inhibits the motion of the flyer plate. In the optimum state (the mass of the RDX charge is 60 mg, the mass of the flyer is 85 mg, and the length of the barrel is 3 mm), the speed of the titanium flyer reaches 583 m/s, and the peak pressure of the RDX deflagration reaches 2182 MPa. This work will provide a theoretical basis for the refined design of a new generation of miniaturized high-performance laser-initiated pyrotechnic devices.

Numerical study on the thermal performance of foam-metal composite phase change material in different force fields

To make a better application of phase change material (PCM) in the thermal management of aerospace systems, this paper investigates effects of the variation of foam-metal pore structure on the thermal performance of composite PCM (CPCM) subjected to different force fields. A two-dimensional numerical model based on the enthalpy-porosity method and the two-temperature energy equation is developed and verified with the experimental data. The thermal behavior of CPCM with different porosities (ω = 20 PPI, ε = 0.91, 0.93, 0.95 and 0.97) and different pore densities (ε = 0.95, ω = 10, 20, 40 and 80 PPI) are investigated under centrifugal acceleration conditions of 0, 5 and -5 g, respectively. A novel index of "end-state isobars" is introduced to describe the melting process of CPCM. The results show that the isotherms of CPCM liquid phase evolve gradually towards the interface parallel to end-state isobars in all conditions. At 0 g, decreasing the porosity effectively improves the thermal conduction of CPCM and slows down the approaching of the isotherms to the end-state isobars. Similarly, increasing the pore density significantly weakens the natural convection of liquid PCM and can also slows down the approaching isotherms to the end-state isobars. At 5 g, the isotherms can match exactly with the end-state isobars, after which the heat transfer process mainly depends on conductive. And decreasing the porosity can significantly improve the thermal performance of CPCM, while adjusting the pore density has almost no effect. At -5 g, the natural convection strength of CPCM is enhanced, changing porosity has limited effect on the heat transfer performance of CPCM, while decreasing pore density can significantly enhance the heat transfer performance. The results may provide some valuable reference for the evaluation and design of latent heat thermal energy storage (LHTES) system suitable to the aerospace field.

Influence of Element Lead (Pb) Content in Tin Plating on Tin Whisker Initiation/Growth

The implementation of the Restriction of Hazardous Substances (RoHS) European Union (EU) Directive in 2005 resulted in the introduction of pure tin as an acceptable surface finish for printed circuit boards and component terminations. A drawback of pure tin surface finishes is the potential to form tin whiskers. Tin whiskers are a metallurgical phenomenon that is associated with tin rich/pure tin materials and has been a topic of intense industry interest. The acceptance and usage of pure tin by the electronics industry component fabricators is understandable as the pure tin surface finishes are inexpensive, are simple plating systems to operate and have reasonable solderability characteristics. However, high performance/harsh environment electronics typically have product life cycles that are measured in decades and therefore are much more susceptible to the potential long term threat of tin whiskers. The GEIA-STD-0005-2 “Standard for Mitigating the Effects of Tin Whiskers in Aerospace and High Performance Electronic Systems” established the definition of the term “Pb-free tin” as : “Pb-free Tin is defined to be pure tin or any tin alloy with &lt;3% lead (Pb) content by weight. A functional definition of “pure tin” was necessary so that the electronics industry could establish tin whisker risk protocols against a known acceptable target value in terms of soldering materials and processes. An investigation was conducted to determine the influence of 1% - 5% elemental lead (Pb) content in tin plating on tin whisker initiation and growth. The investigation results were used in the revision of the GEIA-STD-0005-2 “Standard for Mitigating the Effects of Tin Whiskers in Aerospace and High Performance Electronic Systems” specification technical discussions.

Constructing Highly Reliable and Adaptive Primary Explosive Composites for Micro-Initiator Assisting by a Hybrid Template of Metal-Organic Frameworks and Cross-Linked Polymers.

Primary explosive, as a reliable initiator for secondary explosives, is the central component of micro-initiators for modern aerospace systems and military operations. However, they are typically prepared as powders, posing potential safety risks because of the inevitable particles scattering issues in the actual working environments. Here, the fabrication of a highly adaptive bulk material of copper azide (CA)-based safe primary explosive for micro-initiators is demonstrated. This bulk material, as derived by a complete azidation reaction of the carbonized metal-organic framework/cross-linked polymer hybrid template, enables the firm embedding of active CA species in a cross-linked carbon network (denoted as CA-C). Interestingly, this CA-C bulk material demonstrates multifarious mechanical stabilities (e.g., good shock and vibration resistance, and anti-overload capacity) in the simulated working conditions. Meanwhile, the CA contents in the CA-C bulk material reached as high as 70.3%, ensuring its detonation power. As a proof of concept, CA-C bulk material assembling in a micro-detonator can efficiently detonate the secondary explosive of CL-20 under laser irradiation. This work hereby advances the fabrication of safe and powerful primary explosives for the fulfillment of safe micro-initiator in a broad range of applications in aerospace systems.

Development of Tribological Coatings for Aerospace and Missile Applications

Tribological coatings play a key role in enhancing the performance and service life of engineering systems and components. Over the years, DMRL has worked extensively in studying various aspects of tribological coatings used in aerospace and missile propulsion systems where harsh and hostile environments prevail. The coatings have been deposited mostly by thermal spray processes for these applications. The studies have been done to understand the relationship between microstructure, mechanical properties and tribological behaviour of coatings. In this work, a cermet coating based on carbide to resist wear and an abradable coating based on cobalt alloy to control clearance between the blade tip and shroud for gas turbine aeroengine application and a low friction coating developed for a missile application will be discussed.&#x0D;

Graphene Nanocomposites in Space Sector—Fundamentals and Advancements

Graphene is one of the most significant carbon nanomaterials, with a one-atom-thick two-dimensional nanostructure. Like other nanocarbons, graphene has been used as a polymer reinforcement. This review explores the impact of graphene and graphene-based nanocomposites on aerospace applications. The fabrication and indispensable features of graphene-derived nanocomposites have been considered. Numerous polymers and nanocomposites have been employed for aerospace systems such as reinforced thermosetting/thermoplastic polymers and epoxy/graphene nanocomposites. Moreover, graphene-modified carbon-fiber-based composites have been discussed for the space sector. Aerospace nanocomposites with graphene have been investigated for superior processability, structural features, morphology, heat stability, mechanical properties, flame resistance, electrical/thermal conductivity, radiation protection, and adhesion applications. Subsequently, epoxy and graphene-derived nanocomposites have been explored for heat/mechanically stable aerospace engineering structures, radiation-shielding materials, adhesives, coatings, etc.

Residual stress mitigation in directed energy deposition

Directed Energy Deposition (DED), a class of additive manufacturing techniques, has seen rapid growth over the last decade for potential applications in aerospace, medical devices, and energy systems. Despite notable progress in the research and development of AM, control and mitigation of residual stress during DED remains a challenge. In this work, we propose a novel approach that can be used for the mitigation of residual stresses in additively manufactured components. Specifically, we propose to mitigate the residual stress state of as-deposited components using alloy design, engineering of solid-state transformations, and the introduction of both hard and soft metallic phases. We demonstrate this strategy with a model system consisting of pure Fe and Fe–Cu. Experimental results indicate that residual stresses can be successfully manipulated by adjusting the alloy composition as a soft metallic phase can accommodate plastic deformation. Moreover, our findings suggest that the solid-state transformations experienced by the Fe and Fe-rich phases contribute to the observed differences in magnitude and location of residual stresses. This study is the first to suggest using residual stress as an engineering criterion in the design of alloys for metal additive manufacturing.

Engineering the electronic structure on MXenes via multidimensional component interlayer insertion for enhanced electromagnetic shielding

• CNTs/Ni hybrids were used as an isolation agent to disperse Ti 3 C 2 T x sheets in the interlayers, which form a multiple-dimensional laminated structure. • Introduction of 2D hexagonal magnetic Ni flakes boosts interfacial polarization and magnetic-responding ability, visualized by electron holography. • The 3D freestanding films can achieve precise regulation of components and excellent EMI shielding performance (67.4 dB). MXene-based functional electromagnetic interference (EMI) shielding films are highly desirable for modern integrated electronic and telecommunication systems in aerospace, military, artificial intelligence, and smart and wearable electronics field. In this work, 3D freestanding Ti 3 C 2 T x /CNTs/Ni film assembled by 1D multi-walled carbon nanotubes (MWCNTs)/Ni and 2D Ti 3 C 2 T x MXene sheets was synthesized by a facile vacuum filtration process. By electrostatic incorporation, hexagonal nickel plates embed on the CNTs and then the CNTs/Ni insert into the Ti 3 C 2 T x layers to form magnetized Ti 3 C 2 T x -based functional film with a compact and laminated structure. Due to the outstanding electron migration capacity in the highly conductive Ti 3 C 2 T x sheet and multiple internal reflections from porous and segregated structures, the optimized Ti 3 C 2 T x /CNTs/Ni composite films show excellent EMI shielding effectiveness of 67.4 dB with electrical conductivity of 744 S cm –1 . Surprisingly, a magnetization compensation strategy is built to boost the EMI shielding effectiveness with decreased conductivity. Meanwhile, the visual magnetic coupling phenomenon and charge distribution in the heterogeneous interfaces could be observed in the reconstructed electron holography images. Those encouraging results shed light on novel magnetized MXene-based functional films for high-performance EMI shielding.

Looking at the Bigger Picture with Hulya Kirkici

At the heart of all Hulya Kirkici's work is a commitment to solving humanity's problems. This was instilled in her by her family at a very young age and has grounded her throughout a career of pioneering research in electrical insulation of aerospace and space power systems, lasers, plasma physics, and beyond. Long before becoming a PhD, IEEE Fellow, Eric 0. Forster Distinguished Service Award recipient (and many more accolades), she was a little girl fascinated by numbers.

An experimental investigation of subcooled pool boiling on downward-facing surfaces with microchannels

Upward-facing pooling boiling enhancement employing micro-structure has been extensively studied, yet it is rarely applied in the cooling system in microgravity or In-Vessel Retention (IVR) in nuclear industry. The main challenge lies in effective removal of the vapor columns and replenishment of the fresh liquid without the aid of the buoyancy force. To solve the issue, additional pressure induced by microchannel is introduced to yield spontaneous bubble removal and liquid replenishment in the present work. Downward-facing pool boiling of subcooled FC-72 are conducted on Plain, Straight- and Expanding-Channeled Surfaces (PS, SCS and ECS) with visualization experiments. The superheat at the onset of nucleate boiling (ONB) on channeled surfaces was decreased about 3 K compared to that of the PS, and the maximum heat transfer coefficient (HTC) of the SCS and ECS were improved by 149 % and 217 %, respectively. Compared to PS, the channeled surfaces are more independent from saturated pressure, displaying high and relatively consistent heat transfer coefficients under various pressure conditions. Additionally, with the increasing subcooling degree, channeled surfaces showed greater enhancement in heat transfer performance. Proved by the bubble dynamics, the ECS enabled a directional movement and effective removal of vapor bubbles even though the buoyancy force cannot be utilized under downward-facing condition. The proposed enhancement mechanism attributed to separated vapor–liquid flow paths is independent on gravity and achieves a satisfied pool boiling performance, thus is expected to provide a promising solution for thermal management systems in aerospace and nuclear industry.

Noninvasive fluid bubble detection based on capacitive micromachined ultrasonic transducers

Ultrasonic fluid bubble detection is important in industrial controls, aerospace systems and clinical medicine because it can prevent fatal mechanical failures and threats to life. However, current ultrasonic technologies for bubble detection are based on conventional bulk PZT-based transducers, which suffer from large size, high power consumption and poor integration with ICs and thus are unable to implement real-time and long-term monitoring in tight physical spaces, such as in extracorporeal membrane oxygenation (ECMO) systems and dialysis machines or hydraulic systems in aircraft. This work highlights the prospect of capacitive micromachined ultrasonic transducers (CMUTs) in the aforementioned application situations based on the mechanism of received voltage variation caused by bubble-induced acoustic energy attenuation. The corresponding theories are established and well validated using finite element simulations. The fluid bubbles inside a pipe with a diameter as small as 8 mm are successfully measured using our fabricated CMUT chips with a resonant frequency of 1.1 MHz. The received voltage variation increases significantly with increasing bubble radii in the range of 0.5–2.5 mm. Further studies show that other factors, such as bubble positions, flow velocities, fluid medium types, pipe thicknesses and diameters, have negligible effects on fluid bubble measurement, demonstrating the feasibility and robustness of the CMUT-based ultrasonic bubble detection technique.

Nano-Voids in Ultrafine Explosive Particles: Characterization and Effects on Thermal Stability.

Ultrafine explosives show high safety and reliable initiation and have been widely used in aerospace, military, and industrial systems. The outstanding performance of ultrafine explosives is largely given by the unique void defects according to the simulation results. However, the structures and effects of internal nano-voids in ultrafine explosive particles have been rarely investigated experimentally. In this work, contrast-variation small angle X-ray scattering was verified to reliably measure the structures of internal nano-voids in ultrafine explosive 2,6-diamino-3,5-dinitropyrazine-1-oxide (LLM-105) and 2,2',4,4',6,6'-hexanitro diphenylethylene (HNS). The size of nano-voids is around 10 nm, and the estimated number of nano-voids in a single particle is considerable. Moreover, the thermal stability of ultrafine LLM-105 was improved via changing the structures of nano-voids. This work provides a methodology for the study of nano-void defects in ultrafine organic particles and may pave the path to enhance the performance of ultrafine explosives via defect engineering.

Deep Clustering-Based Anomaly Detection and Health Monitoring for Satellite Telemetry

Satellite telemetry data plays an ever-important role in both the safety and the reliability of a satellite. These two factors are extremely significant in the field of space systems and space missions. Since it is challenging to repair space systems in orbit, health monitoring and early anomaly detection approaches are crucial for the success of space missions. A large number of efficient and accurate methods for health monitoring and anomaly detection have been proposed in aerospace systems but without showing enough concern for the patterns that can be mined from normal operational telemetry data. Concerning this, the present paper proposes DCLOP, an intelligent Deep Clustering-based Local Outlier Probabilities approach that aims at detecting anomalies alongside extracting realistic and reasonable patterns from the normal operational telemetry data. The proposed approach combines (i) a new deep clustering method that uses a dynamically weighted loss function with (ii) the adapted version of Local Outlier Probabilities based on the results of deep clustering. The DCLOP approach effectively monitors the health status of a spacecraft and detects the early warnings of its on-orbit failures. Therefore, this approach enhances the validity and accuracy of anomaly detection systems. The performance of the suggested approach is assessed using actual cube satellite telemetry data. The experimental findings prove that the suggested approach is competitive to the currently used techniques in terms of effectiveness, viability, and validity.