Space Applications Research Articles

Mixed Finite Element Formulation in Nonlinear Geometrical Analysis of Space Trusses and Application to Trusses With Member Length Imperfection

Abstract Space trusses usually have a significant number of elements. As a result, it is inevitable that some elements have imperfections. In this study, the authors proposed a mixed finite element method for nonlinear geometrical analysis of space trusses. The post-buckling behavior of space trusses with length imperfections was predicted using a code list written in the programming software. The numerical results indicate that when the length imperfection approaches zero, the results converge to those obtained in studies on standard trusses. A second approach based on the displacement model is also proposed, in which the Lagrange multiplier method is used to deal with the member length imperfection. The results show that the two approaches proposed by the authors are effective, in which the mix formulation based on the finite element model is superior to that based on the displacement model. These results verify the accuracy of the method. Based on the proposed method, the effects of imperfections in the element layers on the truss were studied. The results show that the imperfections in the top two element layers have the maximum influence on the limit load value, whereas the remaining layers have a negligible influence. The combination of the imperfect lengths of these two layers of elements can produce results in which the limit load value is much larger than in the case of a perfect system. Based on the obtained results, it is possible to provide a solution for improving the overall stability of truss structures by creating reasonable imperfections.

The Geometry and Dynamics of Meaning.

An enigma for human languages is that children learn to understand words in their mother tongue extremely fast. The cognitive sciences have not been able to fully understand the mechanisms behind this highly efficient learning process. In order to provide at least a partial answer to this problem, I have developed a cognitive model of the semantics of natural language in terms of conceptual spaces. I present a background to conceptual spaces and provide a brief summary of their main features, in particular how it handles learning of concepts. I then apply the model to give a geometric account of the semantics of different word classes. In particular, I propose a "single-domain hypotheses" for the semantics of all word classes except nouns. These hypotheses provide a partial answer to the enigma of how words are learned. Next, a dynamic cognitive model of events is introduced that replaces and extends the function of thematic roles. I apply it to analyze the meanings of different kinds of verbs. I argue that the model also explains some aspects of syntactic structure. In particular, I propose that a sentence typically refers to an event. Some further applications of conceptual spaces are briefly presented.

Analysis on future development of solar cells focusing on materials and devices

In recent times, solar cells have garnered significant attention due to their numerous advantages. These include continuously improving energy conversion efficiency, a simple solution preparation method, flexibility, lightweight design, wearability, suitability for ultra-lightweight space applications, and low-cost material components. Perovskite solar cells have achieved impressive efficiencies of over 25% by using high-quality perovskite films synthesized at low temperatures and by making advancements in compatible interface and electrode materials. Moreover, the stability of cells has become a major focus of research. This paper analyzes the development history, material system, device structure, challenges, and future development direction of perovskite solar cells. The unique photoelectric properties and tunable band gap of materials have made them a hot topic in the field of solar cells. In this paper, the basic characteristics and synthesis methods of perovskite materials are introduced before discussing the device structure, interface engineering, and stability of perovskite solar cells in detail. Finally, it prospects on the future development trend of perovskite solar cells.

Measuring the radiation hardness of terahertz devices for space applications

The application of terahertz technology in space is frontier for the development of 6G technologies. Terahertz transceiver devices based on gallium arsenide Schottky barrier diodes (GaAs SBDs) have the characteristics of small size, light weight and low power consumption, making them suitable for application on spacecraft. However, there is currently a lack of experimental assessments on their space adaptability. Here, we study the radiation hardness of terahertz devices to determine their adaptability in complex space environments. We exposed GaAs SBDs and terahertz multipliers as typical terahertz devices to gamma rays and protons. The experimental results showed that the terahertz devices exhibited good tolerance to protons, but prolonged exposure to gamma rays could significantly increase the leakage current of the GaAs SBDs and alter its C-V characteristics, leading to the failure of the terahertz multiplier. Nevertheless, the terahertz devices maintained a good level of radiation hardness, making them highly suitable for use in Low Earth Orbit (LEO) satellites. The comparison between the results of proton and gamma ray tests indicated that the terahertz devices exhibited high inherent radiation hardness against displacement damage but were more sensitive to ionization damage, requiring higher shielding requirements.

Considerations for a Micromirror Array Optimized for Compressive Sensing (VIS to MIR) in Space Applications

Earth observation (EO) is crucial for addressing environmental and societal challenges, but it struggles with revisit times and spatial resolution. The EU-funded SURPRISE project aims to improve EO capabilities by studying space instrumentation using compressive sensing (CS) implemented through spatial light modulators (SLMs) based on micromirror arrays (MMAs) to improve the ground sampling distance. In the SURPRISE project, we studied the development of an MMA that meets the requirements of a CS-based geostationary instrument working in the visible (VIS) and mid-infrared (MIR) spectral ranges. This paper describes the optical simulation procedure and the results obtained for analyzing the performance of such an MMA with the goal of identifying a mirror design that would allow the device to meet the optical requirements of this specific application.

Investigations of high-speed projectile impact on symmetric sandwich structures containing solid propellant with core perforations

The response of solid rocket motors (SRMs) to high-speed fragment impacts is crucial for their safety design and operational use in scenarios such as rocket launches and space applications. The visualized Burn to Violent Reaction (BVR) test is used to observe intense reactions induced by high-speed projectile impacts. Employing a two-stage light gas gun and optical diagnostic techniques including high-speed schlieren imaging and direct photography, the impact-induced deflagration/explosion behavior, and reaction growth behavior were investigated. The damage mechanisms of the casing and propellant samples were assessed, and the reaction growth and afterburn effects of the impact-induced fragment cloud were quantitatively analyzed. The results indicate that the ignition delay time is inversely correlated with the impact velocity, decreasing from ms to μs scale. Across a wide range of velocities (1050–2058 m/s), higher projectile velocities induce more sustained and vigorous combustion reactions within the propellant. Furthermore, increasing the propellant air gap to 7.8 cm does not trigger further reactions under the studied configurations. The reaction mechanisms are closely linked to the characteristics of the fragment cloud induced by the impact. The developed Smoothed Particle Hydrodynamics (SPH) method, incorporating material constitutive models, ignition criteria, and reaction growth models, was used to study the influence of projectile velocity on the reaction mechanisms. The simulation results were compared with experimental data, demonstrating satisfactory accuracy.

Wood and Wood-Based Materials in Space Applications—A Literature Review of Use Cases, Challenges and Potential

Current political and sociological efforts to respond to the need for more environmentally friendly technologies have inspired a revival of wood and wood-based material utilization in space systems. The popularity of these materials has faded since their widespread use in the early days of aerospace engineering. This work reviews the literature to provide an overview of use cases, the motivation for using wood and wood-based materials and the challenges involved. A small number of applications were identified in which wood and wood-based materials were preferred over non-renewable raw materials. They are mainly applied for less-stressed disposable components or as a thermal protection material. It can be shown that the applied wooden materials have advantages such as low production costs, easy availability, easy and environment-friendly decomposition and low weight. However, only a limited number of applications have achieved a high level of technological readiness so far. Properties such as anisotropy and a lack of uniformity, defects in wood, the quantity available material and a lack of standards for the certification of wooden materials represent challenges. These are addressed in the current research, which additionally focuses on sustainable growth, enhanced environmental friendliness and advanced lightweight design.

An experimental and analytical investigation to determine thermal conductivity of epoxy-filler composites for space applications

Thermal conductivity of epoxy-filler composite based Thermal Interface Materials (TIMs) is of utmost importance for thermal management systems used in space applications. Previous studies have shown that depending on the filler particle mixed into the epoxy, thermal conductivity of the composite can either be increased or decreased. Towards that, we have selected four different filler particles (micron sized) – aluminium, copper, zinc and silver to enhance the thermal conductivity of the base epoxy. Thermal conductivity of these 4 epoxy-filler composites has been determined experimentally using an indigenous developed setup at the temperatures ranging from 4.2 K to 323 K. The values have also been reported at various volume fractions (up to 15 %). In addition, after each preparation as the filler particles are mixed mechanically into the epoxy, they are randomly distributed, and this can affect the composite’s thermal conductivity (for the same volume fraction). The experimental determination of thermal conductivity for all the possible distributions is a time consuming, and cumbersome task. In the literature, thermal conductivity values are usually reported for few possible distributions. Therefore, we have developed a novel analytical model to predict all the possible values of thermal conductivity for a specific volume fraction. The predicted values compare well with our experimental data reported in this work at temperatures ranging between 338 K (above room temperature) to 4.2 K (liquid helium temperature). The predicted values are also in good agreement with the experimental values of different fillers such as red mud, pine wood dust and glass fiber etc. from the literature. Additionally, in comparison to other theoretical models like Lewis-Nielsen, Rule of mixture, and Poisson’s distribution, the present model predicts the thermal conductivity values more precisely. This work will be significant in the designing of components where heat transfer plays an important role towards the safety of the component.

Fault Diagnosis of Power Components with Reliability Assessment in Extraterrestrial Microgrids

This research investigates the possible failures caused by aging and other environmental and external factors that could significantly impact the performance of extraterrestrial power systems. Additionally, it presents a reliability assessment model for the space microgrid based on fault tree analysis (FTA). The reliability assessment model developed in this paper represents a tool that can be used by engineers to harden the system design for operational and economic benefits. To improve the reliability of the system, this work provides a broad review of the different fault detection and diagnosis (FDD) algorithms used for power microgrids and space applications. Using data sets from the Habitat Simulator developed through the NASA-funded Resilient Extraterrestrial Habitat Institute, this paper compares the applicability and accuracy of the different FDD methods. The primary FDD approach proposed and assessed in this work is based on the Markov reliability model. It predicts and detects future faults in the space microgrids by using past data samples and categorizing them into different classes. Data-driven-based models such as artificial neural networks are also investigated, tested, and evaluated using simulation data sets. According to the simulation results and the broad FDD algorithm comparison, this study provides the crew or maintenance engineers with a clear methodology to detect and localize power system failures.

Application of a Two-Step Space–Time EOF Statistical Postprocessing Algorithm to Mitigate Subseasonal 200-hPa Geopotential Height Forecast Error

Abstract The time-extended empirical orthogonal function (EEOF) patterns of error developed in a companion paper are applied in this study for model data postprocessing. Projecting forecast anomalies from the model seasonal cycle from GEFSv12 outputs onto these EEOF patterns reconstructs the error principal components (PCs) in a manner that can be applied in real time. When these reconstructed error anomalies are compared with the original GEFSv12 200-hPa geopotential height (Z200) reforecast error anomalies, the projected and validation error signals tend to align temporally. When distributed globally, projection and validation error anomalies have statistically significant positive Pearson correlation coefficients with each other at most grid points outside of the tropics. Categorical Heidke skill score (HSS) analysis reaffirms that by lead day 16 of a forecast, the algorithm skillfully predicts systematic errors for locations outside of the tropics. Hemispheric winter demonstrates that the highest magnitude HSS values are in the high latitudes, illustrating the underlying seasonality of Z200 behavior and predictability. On average, wintertime HSS values hover around 20%, with high-latitude locations exceeding mean values of 40%. Comparatively, summertime values generally exceed 10% improvement outside of the tropics. High-latitude storm-track regions, such as the North Atlantic, North Pacific, and South Pacific, contain the most Z200 variance in the globe and the highest HSS values. This algorithm will be applied to real-time forecasts and additional variables in future work, with the end goal of implementation into the NOAA-CPC subseasonal forecasts.

Near‐Real‐Time Identification of the Source of Ionospheric Disturbances

AbstractThe ionosphere is characterized by a large number of disturbances generated in response to a wide range of phenomena, including natural hazards, space weather and man‐made events. Identification of the origin of ionospheric disturbances (ID), especially in real or near‐real‐time (NRT), is an extremely difficult task, and it is one of the most interesting fundamental scientific questions. In this paper we present, for the first time, an approach for an automatic and NRT‐compatible detection and recognition of the source of ionospheric disturbances in time series of total electron content (TEC) measured by the Global Navigation Satellite Systems (GNSS) method. The main idea is (a) to analyze main characteristics (such as spatio‐temporal features and frequency content) of ID generated by known sources, and (b) in NRT, to rapidly examine ID's features, and, based on this information, recognize their source. Currently, our database contains TEC data series with response to earthquakes, volcanic eruptions, tornadoes, explosions, rocket launches, equatorial plasma bubbles and geomagnetic storms. Our developments are important for the future assessment of natural hazards from the ionosphere, and also for NRT Space Weather nowcast and applications. Also, our work presents important information about the physical properties of ID of different origins.

Mixed-Field Radiation of 3-D MLC Flash Memories for Space Applications

Mixed-Field Radiation of 3-D MLC Flash Memories for Space Applications

Experimental study of a gas-coupled pulse tube cold finger with both active piston and cold inertance tube as phase shifters for 8 K applications

Stirling-type pulse tube cryocoolers (SPTCs) working at temperatures below 8 K represent advantages in very long wave infrared detection, terahertz detection, etc. It is essential for SPTCs to obtain reasonable distribution of impedance to achieve good cooling performance. However, adjusting the distribution of impedance to an optimal value is hard as temperature decreases. It is critical for muti-stage SPTCs working at temperatures below 8 K to arrange appropriate phase shifter at each stage. This paper introduces a gas-coupled pulse tube cold finger with active piston and cold inertance tube as phase shifters for 8 K applications. The cold finger consists of pulse tube 1 (PT1) which works at liquid hydrogen temperatures and pulse tube 2 (PT2) which operates at liquid helium temperatures. Active piston is the phase shifter of PT1. It could adjust the impedance to any value theoretically and make the cold finger highly adaptable. The phase shifter of PT2 is cold inertance tube and gas reservoir. Cold inertance tube and gas reservoir has simple structure which makes it suitable for space applications. The impact of frequency and operating parameters of active piston on no-load temperature is investigated by experiments. A lowest no-load temperature of 5.16 K is achieved in experiments. The effect of temperature distribution of cold finger on cooling capacity at 8 K is also researched. A cooling capacity of 74 mW at 8 K can be obtained with the electric input power of 177.5 W and a pre-cooling capacity of 9.1 W/70 K.

A Review on Adsorption in Nanoporous Adsorbents for Gas Decontamination: Space Applications and Beyond

A Review on Adsorption in Nanoporous Adsorbents for Gas Decontamination: Space Applications and Beyond

Theory and applications of the sum-of-squares technique

Abstract The sum-of-squares (SOS) approximation method is a technique used in optimization problems to derive lower bounds on the optimal value of an objective function. By representing the objective function as a sum of squares in a feature space, the SOS method transforms non-convex global optimization problems into solvable semidefinite programs. This note presents an overview of the SOS method. We start with its application in finite-dimensional feature spaces and, subsequently, we extend it to infinite-dimensional feature spaces using reproducing kernels (k-SOS). Additionally, we highlight the utilization of SOS for estimating some relevant quantities in information theory, including the log-partition function.

Geopolymers for Space Applications Part II: Synthesis and Physical Characterization

This Technical Note presents the continuation of the results regarding the synthesis, and physical and rheological evaluation of geopolymers for space applications. In the first part, the ability of these geopolymers to resist cosmic radiation was evaluated. This second part of the research aims to present the synthesis of the geopolymers, their physical and rheological evaluation, and the fabrication of panels for placement in nanosatellites and deployer systems. Manufacturing the 2 mm-thick geopolymer panel proved to be quite a challenge due to the nature of geopolymers. Three geopolymer formulations MKG-01, MKG-02, and MKG-03 were synthesized with an adequate balance of fluidity and malleability required to manufacture the panels. The formulations offered an open window of approximately 8 h. The mass loss in the formulations was closely related to the solid/liquid ratio of the formulation. The MKG-01 presented lower viscosity and low shear stress for handling, indicating a more homogeneous dispersion than the more viscous samples MKG-02 and MKG-03.

A BIONIC-INSPIRED DRAGONFLY ALGORITHM FOR PARAMETRIC OPTIMIZATION AND DAMAGE INVESTIGATION DURING MACHINING OF MODIFIED POLYMER NANOCOMPOSITE

Polymer nanocomposite is commonly used to develop structural components of space, aircraft, biomedical, sensor, automobile, and battery sector applications. It remarkably substitutes the heavyweight metallic and nonmetallic engineering materials. The machining principles of polymer nanocomposites are intensely different and complex from traditional metals and alloys. The nonhomogeneity, abrasive, and anisotropic nature differs its machining aspect from conventional metallic materials. This investigation aims to execute the CNC drilling of modified nanocomposite using Graphene–carbon (G-C) @ epoxy matrix. The process constraints, namely, cutting speed (S), feed (F), and wt.% of graphene oxide (GO) vary up to three levels and are designed according to the response surface methodology (RSM) array. The nonlinear model is created to predict surface roughness (Ra) and delamination (Fd) on regression analysis. It has been found that the average error for Ra is 0.94% and for Fd it is 3.27%, which is acceptable in model predictions. The metaheuristics-based evolutionary Dragonfly algorithm (DA) evaluated the optimal parametric condition. The optimal setting prediction for the DA is observed as cutting speed (S)-37.68[Formula: see text]m/min, feed (F)-80[Formula: see text]mm/min, and wt.% of graphene oxide (GO)-1%. This algorithm demonstrates a higher application potential than the previous efforts in controlling Ra and Fd values. Both the drilling response values are found to be minimized when the cutting speed increases and the feed decreases. The best fitness value for the DA is 1.626 for surface roughness and 5.086 for delamination. This study agreed with the prediction model’s outcomes and the process parameters’ optimal condition. The defects generated during the sample drilling, such as fiber pull out, uncut/burr, and fiber breakage, were examined using FE-SEM analysis. The optimal findings of the DA module significantly controlled the damages during machining.

Fuel Ignition in HTP Hybrid Rockets at Very Low Mass Fluxes: Challenges and Pulsed Preheating Techniques Using Palladium-Coated Catalysts

In a worldwide scenario which sees an increasing number of small satellite launches, novel mission concepts may be unlocked providing the spacecrafts with the very precise and rapid maneuvering capability that electric thrusters cannot guarantee. In this context, chemical thrusters appear to be a possible solution. This work aimed to experimentally study and solve the problem of ignition for 10 N hybrid rockets based on hydrogen peroxide. Firstly, the study analyzed the performance of a monopropellant engine capable of functioning as a hybrid injection system. In particular, the effects of the liquid mass injected, the initial temperature, and the supply pressure on the pulsed engine performance were experimentally investigated. The injected mass showed a greater impact on the performance with respect to the starting chamber temperature and injection pressure. This thruster also showed a good potential for space applications. In the second part of the work, the objective was to find an ignition procedure that reduced propellant consumption and eliminated the need for a glow plug. This is important because the electrical power consumption in real applications significantly affects other subsystems and is undesirable for chemical engines. Different ignition procedures were tested to emphasize their respective advantages and disadvantages, and the findings indicated that the concept of pulsed preheating is feasible with only a small amount of propellant consumption, while substantially decreasing the ignition duration from approximately 45 min to a maximum of just 3 min. Finally, similar ignition procedures were adopted using different fuels. The results showed that PVC and ABS, under the same operating conditions, ignite more easily than HDPE, which requires an oxidizer consumption approximately double that of the other two fuels. Considerations about the effect of chamber pressure and oxidizer mass flow rate on engine ignition were also included.

Superadditivity between control methods in pest management

AbstractPest Management (PM) has its 1959 origin in Integrated Control, a combination of a reduced dose of insecticide with biological control. At the time, it was not recognised that the interaction between these two control methods was more than additive. This ‘superadditivity’ can also be achieved with the full dose of insecticide, for example, by localising its application in space. There is also likely to be superadditivity in the interaction between partial plant resistance and biological control. Pests on resistant hosts are usually smaller and the same mortality can often be obtained with just two‐thirds or one‐half of the dose of insecticide needed on susceptible plants, giving superadditivity between partial plant resistance and chemical control. These positive interactions between biological control, chemical control and partial host plant resistance form a ‘Pest Management Triad’, though legislation and risk‐aversion may limit the practicability of protocols based on the Triad.

Modelling and simulation in sim 3D software of a solar hybrid cell to using in PV power integration

A photovoltaic cell converts solar energy into electrical energy thanks to the photovoltaic effect. This technology is widely used in land and space applications. Many studies are being carried out to improve the models of these cells and for the proper functioning and to bring them to their maximum potency to be obtained. In this article, we present our photovoltaic cell model and for this we choose a GaAs-based pin cell, our studies carried out at the equilibrium of this cell. We used all our calculations on the SIM 3D simulator carried out in the “Component modelling and circuit design” team. This software is designed to study low geometry design components and to determine the volume of a structure, potential distributions and free carrier densities. The SIM 3D is under development by a group from the Mohamed Tahri University of Bechar. Algeria. We will present our photovoltaic cell model and our SIM 3D software development.