Frontiers in Space Technologies最新文献

{"title":"Proton Spectra for the Interplanetary Space Derived From Different Environmental Models","authors":"E. Klein, M. Sznajder, P. Seefeldt","doi":"10.3389/frspt.2022.933340","DOIUrl":"https://doi.org/10.3389/frspt.2022.933340","url":null,"abstract":"Knowledge about the space radiation environment is crucial for the design and selection of materials and components used for space applications. This environment is characterized not only by the Sun’s electromagnetic radiation but also by charged particles categorized into solar wind, solar energetic particles (SEP) and galactic cosmic rays (GCR). Especially for material engineering and qualification testing, differential and integral spectra for particle energies ranging from keVs to GeVs are required. Up to now, a wide variety of models is available, whereas it is difficult to keep the overview. Although, e.g., the European Cooperation for Space Standardization (ECSS) standard includes instructions on how to investigate particle radiation, it does not provide an overall view. This paper shall support those in need of a comprehensive overview and provide comprehensive information about proton radiation spectra that can potentially be of use for space engineering tasks ranging from mission analysis to material and component design as well as qualification testing. The publicly accessible platforms OLTARIS, SPENVIS, and OMERE were examined for available proton spectra to be used. Exemplary, the particle radiation of solar cycle 23 is considered, which comprehends the years 1996–2008. A common drawback of the available models is their restriction to the MeV-range. Particularly when materials are directly exposed to the space environment, low energetic particles, specifically, the keV-range, are of high interest, since these particle transfer all their energy to the material. Therefore, additional data sources were used in order to include the usually neglected low energy protons into the derived spectrum. The data was transferred to common set of units and eventually could be compared and merged together. This includes a comparison of the most common models, incorporating data foundation, applicability, and accessibility. As a result, extensive and continues spectra are fitted that take all different models with its different energies and fluxes into account. Each covered year is represented by a fitted spectrum including confidence level as applicable. For solar active and quite times spectra are provided.","PeriodicalId":137674,"journal":{"name":"Frontiers in Space Technologies","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116636531","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"CFD-Based Feasibility Study of Laser-Directed Energy Deposition With a Metal Wire for On-Orbit Manufacturing","authors":"S. N. R. Noori Rahim Abadi, P. Hagqvist, F. Sikström, I. Choquet","doi":"10.3389/frspt.2022.880012","DOIUrl":"https://doi.org/10.3389/frspt.2022.880012","url":null,"abstract":"Additive manufacturing of parts on-site in space requires investigating the feasibility of adapting to zero-gravity and near-vacuum conditions, a technology applied today on Earth at standard conditions. While a few studies have been conducted for powder bed fusion, a feasibility study remains to be explored for direct energy deposition using a laser beam and a metal wire. This is the purpose of this study, which is conducted using a modeling approach based on computational fluid dynamics. The simulation model developed includes melting, re-solidification, vaporization, prediction of beam energy absorption as a function of the local surface temperature and curvature, ray tracing, tracking of free surface deformation and metal transfer, and wire-resistive heating. The study is carried out by starting from process parameters suited for stable on-Earth metal deposition. These conditions were also studied experimentally to validate the simulation model, leading to satisfactorily results. A total of three other test cases with ambient pressure lowered down to near-vacuum and/or gravitation down to zero are investigated. It is found that, compared to on-Earth conditions, in-space conditions can induce vaporization of the metal alloy that is large enough to result in a curvature of the melt pool free surface but too small to lead to the formation of a keyhole. The in-space conditions can also modify the force balance at the liquid melt bridge between the wire and the melt pool, leading to small changes in the curvature and temperature field at the free surface of the wire tip. Among the observed consequences are a small increase of the melt pool length and a small elevation of the bead height. More importantly, for process control, changing to in-space conditions might also affect the stability of the process, which could be assessed through the width of the liquid metal bridge. However, by using appropriate process control to maintain a continuous liquid metal bridge, it is concluded that direct energy deposition of metal using a laser and a wire could be used for manufacturing metal parts in-space in a tempered atmosphere.","PeriodicalId":137674,"journal":{"name":"Frontiers in Space Technologies","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122863061","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Transport Properties of Critical Sulfur Hexafluoride From Multiscale Analysis of Density Fluctuations","authors":"A. Oprisan, Dereck Morgado, David Dorf, Seth Zoppelt, S. Oprisan, I. Hahn, Y. Garrabos, C. Lecoutre-Chabot, D. Beysens","doi":"10.3389/frspt.2022.883899","DOIUrl":"https://doi.org/10.3389/frspt.2022.883899","url":null,"abstract":"Density fluctuations near critical points have a wide range of sizes limited only by the boundaries of the enclosing container. How would a fluctuating image near the critical point look if we could break it into disjoint spatial scales, like decomposing white light into narrow-band, monochromatic waves? What are the scaling laws governing each spatial scale? How are the relaxation times of fluctuations at each spatial scale related to the dynamics of fluctuations in the original image? Fluctuations near the critical point of pure fluids lead to different phase separation patterns, which significantly influence the materials’ properties. Due to the diverging compressibility of pure fluids near the critical temperature, the critical phase collapses under its weight on Earth. It limits both the spatial extent of fluctuations and their duration. In microgravity, the buoyancy and convection are suppressed, and the critical state can be observed much closer to the critical point for a more extended period. Local density fluctuations induce light intensity fluctuations (the so-called “critical opalescence”), which we recorded for a sulfur hexafluoride (SF6) sample near the critical point in microgravity using the ALI (Alice-Like Instrumentation insert) of the DECLIC (Dispositif pour l’Etude de la Croissance et des Liquides Critiques) facility on the International Space Station (ISS). From the short (approximately 173 s total recording) data set very near, within 200 μK from the critical temperature, we determined the effective diffusion coefficient for fluctuations of different sizes. For transient and non-stationary data recorded very near the critical point immediately after a thermal quench that steps through critical temperature, we separated fluctuations of various sizes from the original images using the Bidimensional Empirical Mode Decomposition (BEMD) technique. Orthogonal and stationary Intrinsic Mode Function (IMF) images were analyzed using the Fourier-based Dynamic Differential Microscopy (DDM) method to extract the correlation time of fluctuations. We found that a single power-law exponent represented each IMF’s structure factor. Additionally, each Intermediate Scattering Function (ISF) was determined by fluctuations’ unique relaxation time constant. We found that the correlation time of fluctuations increases with IMF’s order, which indicates that small-size fluctuations have the shortest correlation time. Estimating thermophysical properties from short data sets affected by transient phenomena is possible within the BEMD framework.","PeriodicalId":137674,"journal":{"name":"Frontiers in Space Technologies","volume":"41 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128899253","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Mechanical Design of Self-Reconfiguring 4D-Printed OrigamiSats: A New Concept for Solar Sailing","authors":"Aloisia Russo, B. Robb, S. Soldini, P. Paoletti, Gilles Bailet, C. McInnes, J. Reveles, A. K. Sugihara, Stéphane Bonardi, Osamu Mori","doi":"10.3389/frspt.2022.876585","DOIUrl":"https://doi.org/10.3389/frspt.2022.876585","url":null,"abstract":"In this article, a self-reconfiguring OrigamiSat concept is presented. The reconfiguration of the proposed OrigamiSat is triggered by combining the effect of 4D material (i.e. origami’s edges) and changes in the local surface optical properties (i.e., origami’s facets) to harness the solar radiation pressure acceleration. The proposed OrigamiSat uses the principle of solar sailing to enhance the effect of the Sun radiation to generate momentum on the Aluminised Kapton (Al-Kapton) origami surface by transitioning from mirror-like to diffusely reflecting optical properties of each individual facet. Numerical simulations have demonstrated that local changes in the optical properties can trigger reconfiguration. A minimum of 1-m edge size facet is required for a thick-origami to generate enough forces from the Sun radiation. The thick-origami pattern is 3D-printed directly on a thin Al-Kapton film (the solar sail substrate which is highly reflective). An elastic filament (thermoplastic polyurethane TPU) showed best performance when printing directly on the Al-Kapton and the Acrylonitrile Butadiene Styrene with carbon fiber reinforcement (ABS/cc) is added to augment the origami mechanical properties. The 4D material (shape memory polymer) is integrated only at specific edges to achieve self-deployment by applying heat. Two different folding mechanisms were studied: 1) the cartilage-like, where the hinge is made combining the TPU and the 4D material which make the mounts or valleys fully stretchable, and 2) the mechanical hinge, where simple hinges are made solely of ABS/cc. Numerical simulations have demonstrated that the cartilage-like hinge is the most suitable design for light-weight reconfigurable OrigamiSat when using the solar radiation pressure acceleration. We have used build-in electric board to heat up the 4D material and trigger the folding. We envisage embedding the heat wire within the 4D hinge in the future.","PeriodicalId":137674,"journal":{"name":"Frontiers in Space Technologies","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132444738","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A comparison of Fourier and POD mode decomposition methods for high-speed Hall thruster video","authors":"J. Brooks, A. Kaptanoglu, M. McDonald, Chris Volkmar, Technische Hochschule, Mittelhessen, Germany, Kristof Holste, Jens Schmidt","doi":"10.3389/frspt.2023.1220011","DOIUrl":"https://doi.org/10.3389/frspt.2023.1220011","url":null,"abstract":"Hall thrusters are susceptible to large-amplitude plasma oscillations that impact thruster performance and lifetime and are also difficult to model. High-speed cameras are a popular tool to study these dynamics due to their spatial resolution and are a popular, nonintrusive complement to in situ probes. High-speed video of thruster oscillations can be isolated (decomposed) into coherent structures (modes) with algorithms that help us better understand the evolution and interactions of each. This work provides an introduction, comparison, and step-by-step tutorial on established Fourier and newer Proper Orthogonal Decomposition (POD) algorithms as applied to high-speed video of the unshielded H6 6-kW laboratory model Hall thruster. From this dataset, both sets of algorithms identify and characterize m = 0 and m > 0 modes in the discharge channel and cathode regions of the thruster plume, as well as mode hopping between the m = 3 and m = 4 rotating spokes in the channel. The Fourier methods are ideal for characterizing linear modal structures and also provide intuitive dispersion relationships. By contrast, the POD method tailors a basis set using energy minimization techniques that better captures the nonlinear nature of these structures and with a simpler implementation. Together, the Fourier and POD methods provide a more complete toolkit for studying Hall thruster plasma instabilities and mode dynamics. Specifically, we recommend first applying POD to quickly identify the nature and location of global dynamics and then using Fourier methods to isolate dispersion plots and other wave-based physics.","PeriodicalId":137674,"journal":{"name":"Frontiers in Space Technologies","volume":"74 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120882162","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"FPGA-Based CNN for Real-Time UAV Tracking and Detection","authors":"P. Hobden, S. Srivastava, Edmond Nurellari","doi":"10.3389/frspt.2022.878010","DOIUrl":"https://doi.org/10.3389/frspt.2022.878010","url":null,"abstract":"Neural networks (NNs) are now being extensively utilized in various artificial intelligence platforms specifically in the area of image classification and real-time object tracking. We propose a novel design to address the problem of real-time unmanned aerial vehicle (UAV) monitoring and detection using a Zynq UltraScale FPGA-based convolutional neural network (CNN). The biggest challenge while implementing real-time algorithms on FPGAs is the limited DSP hardware resources available on FPGA platforms. Our proposed design overcomes the challenge of autonomous real-time UAV detection and tracking using a Xilinx’s Zynq UltraScale XCZU9EG system on a chip (SoC) platform. Our proposed design explores and provides a solution for overcoming the challenge of limited floating-point resources while maintaining real-time performance. The solution consists of two modules: UAV tracking module and neural network–based UAV detection module. The tracking module uses our novel background-differencing algorithm, while the UAV detection is based on a modified CNN algorithm, designed to give the maximum field-programmable gate array (FPGA) performance. These two modules are designed to complement each other and enabled simultaneously to provide an enhanced real-time UAV detection for any given video input. The proposed system has been tested on real-life flying UAVs, achieving an accuracy of 82%, running at the full frame rate of the input camera for both tracking and neural network (NN) detection, achieving similar performance than an equivalent deep learning processor unit (DPU) with UltraScale FPGA-based HD video and tracking implementation but with lower resource utilization as shown by our results.","PeriodicalId":137674,"journal":{"name":"Frontiers in Space Technologies","volume":"48 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-05-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123617874","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Review on Transport Phenomena Near the Critical Point of Fluids Under Weightlessness","authors":"D. Beysens","doi":"10.3389/frspt.2022.876642","DOIUrl":"https://doi.org/10.3389/frspt.2022.876642","url":null,"abstract":"Fluids near their liquid-vapor critical point, liquid mixtures near their miscibility critical point, exhibit universal behavior in their transport properties. Weightlessness is most often mandatory to properly evidence these properties. This review is concerned with some of the most important results obtained thanks to space experiments concerning thermal, mass, and momentum transport. Thermal aspects in pure fluids are mainly concerned with the discovery of a new thermalization process, the Piston Effect, leading to paradoxical effects such as a “critical speeding up” instead of the classical “critical slowing down”, heat seemingly flowing backwards and cooling resulting from heating. Mass transport deals with the process of boiling in the liquid phase, and phase transition when the fluid or the liquid mixture is thermally quenched from the homogeneous, supercritical region, to the two-phase region where it phase separates. Weightlessness makes universal the dynamics of phase separation. Momentum transport is concerned with the scaled behavior of viscosity and the effects of vibrations. Vibrations lead to effects (interface position, instabilities) that resemble buoyancy effects seemingly caused by an artificial gravity. Although weightlessness has led to solve important problems, many questions are still opened.","PeriodicalId":137674,"journal":{"name":"Frontiers in Space Technologies","volume":"54 6","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-05-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"113933804","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Instabilities in a Spherical Liquid Drop","authors":"R. Prud’homme","doi":"10.3389/frspt.2022.835464","DOIUrl":"https://doi.org/10.3389/frspt.2022.835464","url":null,"abstract":"We examine cases of stationary vortices that can appear inside spherical liquid drops in microgravity conditions. The first case is that of an incompressible external flow of uniform speed at infinity, leading the liquid in the drop by friction to form a Hill vortex. In the second case, the external fluid does not interact by friction with the liquid, but the drop is subjected to an axial temperature gradient causing a variation in surface tension. This time it is the induced movement which entrains the internal liquid. Note that the two situations can lead to the same Hill vortex. Combined effects are envisioned. We are also interested in the time factor in these phenomena.","PeriodicalId":137674,"journal":{"name":"Frontiers in Space Technologies","volume":"106 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128859583","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"High Mass Resolution fs-LIMS Imaging and Manifold Learning Reveal Insight Into Chemical Diversity of the 1.88 Ga Gunflint Chert","authors":"R. Lukmanov, C. D. de Koning, Peter Keresztes Schmidt, D. Wacey, N. Ligterink, S. Gruchola, V. Grimaudo, A. Neubeck, A. Riedo, M. Tulej, P. Wurz","doi":"10.3389/frspt.2022.718943","DOIUrl":"https://doi.org/10.3389/frspt.2022.718943","url":null,"abstract":"Extraction of useful information from unstructured, large and complex mass spectrometric signals is a challenge in many application fields of mass spectrometry. Therefore, new data analysis approaches are required to help uncover the complexity of such signals. In this contribution, we examined the chemical composition of the 1.88 Ga Gunflint chert using the newly developed high mass resolution laser ionization mass spectrometer (fs-LIMS-GT). We report results on the following: 1) mass-spectrometric multi-element imaging of the Gunflint chert sample; and 2) identification of multiple chemical entities from spatial mass spectrometric data utilizing nonlinear dimensionality reduction and spectral similarity networks. The analysis of 40′000 mass spectra reveals the presence of chemical heterogeneity (seven minor compounds) and two large clusters of spectra registered from the organic material and inorganic host mineral. Our results show the utility of fs-LIMS imaging in combination with manifold learning methods in studying chemically diverse samples.","PeriodicalId":137674,"journal":{"name":"Frontiers in Space Technologies","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114082845","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Autonomous Crosslink Radionavigation for a Lunar CubeSat Mission","authors":"E. Turan, S. Speretta, E. Gill","doi":"10.3389/frspt.2022.919311","DOIUrl":"https://doi.org/10.3389/frspt.2022.919311","url":null,"abstract":"This study presents an autonomous orbit determination system based on crosslink radiometric measurements applied to a future lunar CubeSat mission to clearly highlight its advantages with respect to existing ground-based navigation strategies. This work is based on the Linked Autonomous Interplanetary Satellite Orbit Navigation (LiAISON) method which provides an autonomous navigation solution solely using satellite-to-satellite measurements, such as range and/or range-rate, to estimate absolute spacecraft states when at least one of the involved spacecraft has an orbit with a unique size, shape, and orientation. The lunar vicinity is a perfect candidate for this type of application due to the asymmetrical gravity field: the selected lunar mission, an Earth-Moon L2 (EML2) Halo orbiter, has an inter-satellite link between a lunar elliptical frozen orbiter. Simulation results show that, even in case of high-measurement errors (in the order of 100 m, 1σ), the navigation filter estimates the true states of spacecraft at EML2 with an error in the order of 500 m for position, and 2 mm/s for velocity, respectively and the elliptical lunar frozen orbiter states can be estimated in the order of 100 m for position and 1 cm/s for velocity, respectively. This study shows that range-only measurements provide better state estimation than range-rate-only measurements for this specific situation. Different bias handling strategies are also investigated. It has been found that even a less accurate ranging method, such as data-aided ranging, provides a sufficient orbit determination solution. This would simplify the communication system design for the selected CubeSat mission. The most observable states are found to be position states of the lunar orbiter via the observability analysis. In addition, the best tracking windows are also investigated for the selected mission scenario.","PeriodicalId":137674,"journal":{"name":"Frontiers in Space Technologies","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134578937","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}