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MATHEMATICS (714 journals)                  1 2 3 4 | Last

Showing 1 - 200 of 538 Journals sorted alphabetically
Abakós     Open Access   (Followers: 4)
Abhandlungen aus dem Mathematischen Seminar der Universitat Hamburg     Hybrid Journal   (Followers: 4)
Academic Voices : A Multidisciplinary Journal     Open Access   (Followers: 2)
Accounting Perspectives     Full-text available via subscription   (Followers: 7)
ACM Transactions on Algorithms (TALG)     Hybrid Journal   (Followers: 15)
ACM Transactions on Computational Logic (TOCL)     Hybrid Journal   (Followers: 3)
ACM Transactions on Mathematical Software (TOMS)     Hybrid Journal   (Followers: 6)
ACS Applied Materials & Interfaces     Hybrid Journal   (Followers: 29)
Acta Applicandae Mathematicae     Hybrid Journal   (Followers: 1)
Acta Mathematica     Hybrid Journal   (Followers: 12)
Acta Mathematica Hungarica     Hybrid Journal   (Followers: 2)
Acta Mathematica Scientia     Full-text available via subscription   (Followers: 5)
Acta Mathematica Sinica, English Series     Hybrid Journal   (Followers: 6)
Acta Mathematica Vietnamica     Hybrid Journal  
Acta Mathematicae Applicatae Sinica, English Series     Hybrid Journal  
Advanced Science Letters     Full-text available via subscription   (Followers: 10)
Advances in Applied Clifford Algebras     Hybrid Journal   (Followers: 4)
Advances in Calculus of Variations     Hybrid Journal   (Followers: 3)
Advances in Catalysis     Full-text available via subscription   (Followers: 5)
Advances in Complex Systems     Hybrid Journal   (Followers: 7)
Advances in Computational Mathematics     Hybrid Journal   (Followers: 19)
Advances in Decision Sciences     Open Access   (Followers: 3)
Advances in Difference Equations     Open Access   (Followers: 3)
Advances in Fixed Point Theory     Open Access   (Followers: 5)
Advances in Geosciences (ADGEO)     Open Access   (Followers: 13)
Advances in Linear Algebra & Matrix Theory     Open Access   (Followers: 3)
Advances in Materials Science     Open Access   (Followers: 14)
Advances in Mathematical Physics     Open Access   (Followers: 4)
Advances in Mathematics     Full-text available via subscription   (Followers: 11)
Advances in Numerical Analysis     Open Access   (Followers: 5)
Advances in Operations Research     Open Access   (Followers: 12)
Advances in Porous Media     Full-text available via subscription   (Followers: 5)
Advances in Pure and Applied Mathematics     Hybrid Journal   (Followers: 6)
Advances in Pure Mathematics     Open Access   (Followers: 6)
Advances in Science and Research (ASR)     Open Access   (Followers: 6)
Aequationes Mathematicae     Hybrid Journal   (Followers: 2)
African Journal of Educational Studies in Mathematics and Sciences     Full-text available via subscription   (Followers: 5)
African Journal of Mathematics and Computer Science Research     Open Access   (Followers: 4)
Afrika Matematika     Hybrid Journal   (Followers: 1)
Air, Soil & Water Research     Open Access   (Followers: 11)
AKSIOMA Journal of Mathematics Education     Open Access   (Followers: 1)
Al-Jabar : Jurnal Pendidikan Matematika     Open Access   (Followers: 1)
Algebra and Logic     Hybrid Journal   (Followers: 6)
Algebra Colloquium     Hybrid Journal   (Followers: 4)
Algebra Universalis     Hybrid Journal   (Followers: 2)
Algorithmic Operations Research     Full-text available via subscription   (Followers: 5)
Algorithms     Open Access   (Followers: 11)
Algorithms Research     Open Access   (Followers: 1)
American Journal of Computational and Applied Mathematics     Open Access   (Followers: 5)
American Journal of Mathematical Analysis     Open Access  
American Journal of Mathematics     Full-text available via subscription   (Followers: 6)
American Journal of Operations Research     Open Access   (Followers: 5)
An International Journal of Optimization and Control: Theories & Applications     Open Access   (Followers: 8)
Analele Universitatii Ovidius Constanta - Seria Matematica     Open Access   (Followers: 1)
Analysis and Applications     Hybrid Journal   (Followers: 1)
Analysis and Mathematical Physics     Hybrid Journal   (Followers: 5)
Analysis Mathematica     Full-text available via subscription  
Analysis. International mathematical journal of analysis and its applications     Hybrid Journal   (Followers: 2)
Annales Mathematicae Silesianae     Open Access  
Annales mathématiques du Québec     Hybrid Journal   (Followers: 4)
Annales Universitatis Paedagogicae Cracoviensis. Studia Mathematica     Open Access  
Annali di Matematica Pura ed Applicata     Hybrid Journal   (Followers: 1)
Annals of Combinatorics     Hybrid Journal   (Followers: 4)
Annals of Data Science     Hybrid Journal   (Followers: 12)
Annals of Discrete Mathematics     Full-text available via subscription   (Followers: 6)
Annals of Mathematics     Full-text available via subscription   (Followers: 1)
Annals of Mathematics and Artificial Intelligence     Hybrid Journal   (Followers: 12)
Annals of Pure and Applied Logic     Open Access   (Followers: 3)
Annals of the Alexandru Ioan Cuza University - Mathematics     Open Access  
Annals of the Institute of Statistical Mathematics     Hybrid Journal   (Followers: 1)
Annals of West University of Timisoara - Mathematics     Open Access  
Annuaire du Collège de France     Open Access   (Followers: 5)
ANZIAM Journal     Open Access   (Followers: 1)
Applicable Algebra in Engineering, Communication and Computing     Hybrid Journal   (Followers: 2)
Applications of Mathematics     Hybrid Journal   (Followers: 2)
Applied Categorical Structures     Hybrid Journal   (Followers: 2)
Applied Computational Intelligence and Soft Computing     Open Access   (Followers: 11)
Applied Mathematics     Open Access   (Followers: 3)
Applied Mathematics     Open Access   (Followers: 7)
Applied Mathematics & Optimization     Hybrid Journal   (Followers: 6)
Applied Mathematics - A Journal of Chinese Universities     Hybrid Journal  
Applied Mathematics Letters     Full-text available via subscription   (Followers: 2)
Applied Mathematics Research eXpress     Hybrid Journal   (Followers: 1)
Applied Network Science     Open Access   (Followers: 3)
Applied Numerical Mathematics     Hybrid Journal   (Followers: 5)
Applied Spatial Analysis and Policy     Hybrid Journal   (Followers: 5)
Arab Journal of Mathematical Sciences     Open Access   (Followers: 3)
Arabian Journal of Mathematics     Open Access   (Followers: 2)
Archive for Mathematical Logic     Hybrid Journal   (Followers: 3)
Archive of Applied Mechanics     Hybrid Journal   (Followers: 5)
Archive of Numerical Software     Open Access  
Archives of Computational Methods in Engineering     Hybrid Journal   (Followers: 5)
Arkiv för Matematik     Hybrid Journal   (Followers: 1)
Armenian Journal of Mathematics     Open Access  
Arnold Mathematical Journal     Hybrid Journal   (Followers: 1)
Artificial Satellites     Open Access   (Followers: 20)
Asia-Pacific Journal of Operational Research     Hybrid Journal   (Followers: 3)
Asian Journal of Algebra     Open Access   (Followers: 1)
Asian Journal of Current Engineering & Maths     Open Access  
Asian-European Journal of Mathematics     Hybrid Journal   (Followers: 2)
Australian Mathematics Teacher, The     Full-text available via subscription   (Followers: 6)
Australian Primary Mathematics Classroom     Full-text available via subscription   (Followers: 4)
Australian Senior Mathematics Journal     Full-text available via subscription   (Followers: 1)
Automatic Documentation and Mathematical Linguistics     Hybrid Journal   (Followers: 5)
Axioms     Open Access   (Followers: 1)
Baltic International Yearbook of Cognition, Logic and Communication     Open Access   (Followers: 1)
Basin Research     Hybrid Journal   (Followers: 5)
BIBECHANA     Open Access   (Followers: 2)
BIT Numerical Mathematics     Hybrid Journal  
BoEM - Boletim online de Educação Matemática     Open Access  
Boletim Cearense de Educação e História da Matemática     Open Access  
Boletim de Educação Matemática     Open Access  
Boletín de la Sociedad Matemática Mexicana     Hybrid Journal  
Bollettino dell'Unione Matematica Italiana     Full-text available via subscription   (Followers: 1)
British Journal of Mathematical and Statistical Psychology     Full-text available via subscription   (Followers: 20)
Bruno Pini Mathematical Analysis Seminar     Open Access  
Buletinul Academiei de Stiinte a Republicii Moldova. Matematica     Open Access   (Followers: 12)
Bulletin des Sciences Mathamatiques     Full-text available via subscription   (Followers: 4)
Bulletin of Dnipropetrovsk University. Series : Communications in Mathematical Modeling and Differential Equations Theory     Open Access   (Followers: 1)
Bulletin of Mathematical Sciences     Open Access   (Followers: 1)
Bulletin of Symbolic Logic     Full-text available via subscription   (Followers: 2)
Bulletin of the Australian Mathematical Society     Full-text available via subscription   (Followers: 1)
Bulletin of the Brazilian Mathematical Society, New Series     Hybrid Journal  
Bulletin of the London Mathematical Society     Hybrid Journal   (Followers: 4)
Bulletin of the Malaysian Mathematical Sciences Society     Hybrid Journal  
Calculus of Variations and Partial Differential Equations     Hybrid Journal  
Canadian Journal of Science, Mathematics and Technology Education     Hybrid Journal   (Followers: 19)
Carpathian Mathematical Publications     Open Access   (Followers: 1)
Catalysis in Industry     Hybrid Journal   (Followers: 1)
CEAS Space Journal     Hybrid Journal   (Followers: 2)
CHANCE     Hybrid Journal   (Followers: 5)
Chaos, Solitons & Fractals     Hybrid Journal   (Followers: 3)
ChemSusChem     Hybrid Journal   (Followers: 7)
Chinese Annals of Mathematics, Series B     Hybrid Journal  
Chinese Journal of Catalysis     Full-text available via subscription   (Followers: 2)
Chinese Journal of Mathematics     Open Access  
Clean Air Journal     Full-text available via subscription   (Followers: 1)
Cogent Mathematics     Open Access   (Followers: 2)
Cognitive Computation     Hybrid Journal   (Followers: 4)
Collectanea Mathematica     Hybrid Journal  
COMBINATORICA     Hybrid Journal  
Combinatorics, Probability and Computing     Hybrid Journal   (Followers: 4)
Combustion Theory and Modelling     Hybrid Journal   (Followers: 14)
Commentarii Mathematici Helvetici     Hybrid Journal   (Followers: 1)
Communications in Combinatorics and Optimization     Open Access  
Communications in Contemporary Mathematics     Hybrid Journal  
Communications in Mathematical Physics     Hybrid Journal   (Followers: 2)
Communications On Pure & Applied Mathematics     Hybrid Journal   (Followers: 3)
Complex Analysis and its Synergies     Open Access   (Followers: 2)
Complex Variables and Elliptic Equations: An International Journal     Hybrid Journal  
Complexus     Full-text available via subscription  
Composite Materials Series     Full-text available via subscription   (Followers: 8)
Compositio Mathematica     Full-text available via subscription   (Followers: 1)
Comptes Rendus Mathematique     Full-text available via subscription   (Followers: 1)
Computational and Applied Mathematics     Hybrid Journal   (Followers: 2)
Computational and Mathematical Methods in Medicine     Open Access   (Followers: 2)
Computational and Mathematical Organization Theory     Hybrid Journal   (Followers: 2)
Computational Complexity     Hybrid Journal   (Followers: 4)
Computational Mathematics and Modeling     Hybrid Journal   (Followers: 8)
Computational Mechanics     Hybrid Journal   (Followers: 5)
Computational Methods and Function Theory     Hybrid Journal  
Computational Optimization and Applications     Hybrid Journal   (Followers: 7)
Computers & Mathematics with Applications     Full-text available via subscription   (Followers: 8)
Concrete Operators     Open Access   (Followers: 5)
Confluentes Mathematici     Hybrid Journal  
Contributions to Game Theory and Management     Open Access  
COSMOS     Hybrid Journal  
Cryptography and Communications     Hybrid Journal   (Followers: 13)
Cuadernos de Investigación y Formación en Educación Matemática     Open Access  
Cubo. A Mathematical Journal     Open Access  
Current Research in Biostatistics     Open Access   (Followers: 9)
Czechoslovak Mathematical Journal     Hybrid Journal   (Followers: 1)
Demographic Research     Open Access   (Followers: 11)
Demonstratio Mathematica     Open Access  
Dependence Modeling     Open Access  
Design Journal : An International Journal for All Aspects of Design     Hybrid Journal   (Followers: 29)
Developments in Clay Science     Full-text available via subscription   (Followers: 1)
Developments in Mineral Processing     Full-text available via subscription   (Followers: 3)
Dhaka University Journal of Science     Open Access  
Differential Equations and Dynamical Systems     Hybrid Journal   (Followers: 3)
Differentsial'nye Uravneniya     Open Access  
Discrete Mathematics     Hybrid Journal   (Followers: 8)
Discrete Mathematics & Theoretical Computer Science     Open Access  
Discrete Mathematics, Algorithms and Applications     Hybrid Journal   (Followers: 2)
Discussiones Mathematicae - General Algebra and Applications     Open Access  
Discussiones Mathematicae Graph Theory     Open Access   (Followers: 1)
Diskretnaya Matematika     Full-text available via subscription  
Dnipropetrovsk University Mathematics Bulletin     Open Access  
Doklady Akademii Nauk     Open Access  
Doklady Mathematics     Hybrid Journal  
Duke Mathematical Journal     Full-text available via subscription   (Followers: 1)
Eco Matemático     Open Access  
Edited Series on Advances in Nonlinear Science and Complexity     Full-text available via subscription  
Electronic Journal of Combinatorics     Open Access  
Electronic Journal of Differential Equations     Open Access  
Electronic Journal of Graph Theory and Applications     Open Access   (Followers: 2)
Electronic Notes in Discrete Mathematics     Full-text available via subscription   (Followers: 2)
Elemente der Mathematik     Full-text available via subscription   (Followers: 4)
Energy for Sustainable Development     Hybrid Journal   (Followers: 9)
Enseñanza de las Ciencias : Revista de Investigación y Experiencias Didácticas     Open Access  

        1 2 3 4 | Last

Journal Cover
CEAS Space Journal
Journal Prestige (SJR): 0.278
Citation Impact (citeScore): 1
Number of Followers: 2  
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1868-2510 - ISSN (Online) 1868-2502
Published by Springer-Verlag Homepage  [2348 journals]
  • Calibration OGSEs for multichannel radiometers for Mars atmosphere studies
    • Authors: J. J. Jiménez; F. J Álvarez; M. Gonzalez-Guerrero; V. Apéstigue; I. Martín; J. M. Fernández; A. A. Fernán; I. Arruego
      Pages: 127 - 145
      Abstract: This work describes several Optical Ground Support Equipment (OGSEs) developed by INTA (Spanish Institute of Aerospace Technology—Instituto Nacional de Técnica Aeroespacial) for the calibration and characterization of their self-manufactured multichannel radiometers (solar irradiance sensors—SIS) developed for working on the surface of Mars and studying the atmosphere of that planet. Nowadays, INTA is developing two SIS for the ESA ExoMars 2020 and for the JPL/NASA Mars 2020 missions. These calibration OGSEs have been improved since the first model in 2011 developed for Mars MetNet Precursor mission. This work describes the currently used OGSE. Calibration tests provide an objective evidence of the SIS performance, allowing the conversion of the electrical sensor output into accurate physical measurements (irradiance) with uncertainty bounds. Calibration results of the SIS on board of the Dust characterisation, Risk assessment, and Environment Analyzer on the Martian Surface (DREAMS) on board the ExoMars 2016 Schiaparelli module (EDM—entry and descent module) are also presented, as well as their error propagation. Theoretical precision and accuracy of the instrument are determined by these results. Two types of OGSE are used as a function of the pursued aim: calibration OGSEs and Optical Fast Verification (OFV) GSE. Calibration OGSEs consist of three setups which characterize with the highest possible accuracy, the responsivity, the angular response and the thermal behavior; OFV OGSE verify that the performance of the sensor is close to nominal after every environmental and qualification test. Results show that the accuracy of the calibrated sensors is a function of the accuracy of the optical detectors and of the light conditions. For normal direct incidence and diffuse light, the accuracy is in the same order of uncertainty as that of the reference cell used for fixing the irradiance, which is about 1%.
      PubDate: 2018-06-01
      DOI: 10.1007/s12567-018-0194-8
      Issue No: Vol. 10, No. 2 (2018)
  • Model-based software engineering for an optical navigation system for
    • Authors: T. Franz; D. Lüdtke; O. Maibaum; A. Gerndt
      Pages: 147 - 156
      Abstract: The project Autonomous Terrain-based Optical Navigation (ATON) at the German Aerospace Center (DLR) is developing an optical navigation system for future landing missions on celestial bodies such as the moon or asteroids. Image data obtained by optical sensors can be used for autonomous determination of the spacecraft’s position and attitude. Camera-in-the-loop experiments in the Testbed for Robotic Optical Navigation (TRON) laboratory and flight campaigns with unmanned aerial vehicle (UAV) are performed to gather flight data for further development and to test the system in a closed-loop scenario. The software modules are executed in the C++ Tasking Framework that provides the means to concurrently run the modules in separated tasks, send messages between tasks, and schedule task execution based on events. Since the project is developed in collaboration with several institutes in different domains at DLR, clearly defined and well-documented interfaces are necessary. Preventing misconceptions caused by differences between various development philosophies and standards turned out to be challenging. After the first development cycles with manual Interface Control Documents (ICD) and manual implementation of the complex interactions between modules, we switched to a model-based approach. The ATON model covers a graphical description of the modules, their parameters and communication patterns. Type and consistency checks on this formal level help to reduce errors in the system. The model enables the generation of interfaces and unified data types as well as their documentation. Furthermore, the C++ code for the exchange of data between the modules and the scheduling of the software tasks is created automatically. With this approach, changing the data flow in the system or adding additional components (e.g., a second camera) have become trivial.
      PubDate: 2018-06-01
      DOI: 10.1007/s12567-017-0173-5
      Issue No: Vol. 10, No. 2 (2018)
  • A concept of active mount for space applications
    • Authors: A. Souleille; T. Lampert; V. Lafarga; S. Hellegouarch; A. Rondineau; G. Rodrigues; C. Collette
      Pages: 157 - 165
      Abstract: Sensitive payloads mounted on top of launchers are subjected to many sources of disturbances during the flight. The most severe dynamic loads arise from the ignition of the motors, gusts, pressure fluctuations in the booster and from the separation of the boosters. The transmission of these dynamic forces can be reduced by mounting payloads on passive isolators, which comes at the expense of harmful amplifications of the motion at low frequency due to suspension resonances. To bypass this shortcoming, this paper presents a novel concept of active mount for aerospace payloads, which is easy to install, and meets two objectives. The first one is a high damping authority on both suspension resonances and flexible resonances without compromising the isolation and large stability margins of the closed loop system due to the collocation of the actuator and the sensor. The second one is a broadband reduction of the dynamic force transmitted to the payload, which was achieved in terms of 16 dB. The concept is presented in the first part of the paper and studied numerically and experimentally on a single degree of freedom isolator. A commercial isolator has been chosen for the purpose of the demonstration. The second part of the paper is dedicated to experimental validations on multi-degree of freedom scaled test benches. It is shown that the force feedback allows damping of both suspension and flexible modes (first and second modes, respectively), and significantly reducing the force transmitted in some broad frequency ranges.
      PubDate: 2018-06-01
      DOI: 10.1007/s12567-017-0180-6
      Issue No: Vol. 10, No. 2 (2018)
  • The Aurora space launcher concept
    • Authors: Alexander Kopp; Sven Stappert; David Mattsson; Kurt Olofsson; Erik Marklund; Guido Kurth; Erwin Mooij; Evelyne Roorda
      Pages: 167 - 187
      Abstract: This paper gives an overview about the Aurora reusable space launcher concept study that was initiated in late-2015/early-2016. Within the Aurora study, several spaceplane-like vehicle configurations with different geometries, propulsion systems and mission profiles will be designed, investigated and evaluated with respect to their technical and economic feasibility. The first part of this paper will discuss the study logic and the current status of the Aurora studies and introduces the first vehicle configurations and their system design status. As the identification of highly efficient structural designs is of particular interest for Aurora, the structural design and analysis approach will be discussed in higher level of detail. A special design feature of the Aurora vehicle configurations is the utilization of the novel thin-ply composite material technology for structural mass reductions. Therefore, the second part of this paper will briefly discuss this technology and investigate the application and potential mass savings on vehicle level within simplified structural analysis studies. The results indicate that significant mass savings could be possible. Finally, an outlook on the next steps is provided.
      PubDate: 2018-06-01
      DOI: 10.1007/s12567-017-0184-2
      Issue No: Vol. 10, No. 2 (2018)
  • Modal analysis of passive flow control for the turbulent wake of a generic
           planar space launcher
    • Authors: S. Loosen; V. Statnikov; M. Meinke; W. Schröder
      Pages: 189 - 202
      Abstract: The turbulent wake of a generic planar space launcher equipped with two passive flow control devices is simulated using a zonal RANS–LES method and analyzed by dynamic mode decomposition (DMD). In the first approach, the effect of a classical boat tail on the wake is examined. In the second concept, a flow control device consisting of semi-circular lobes integrated at the base shoulder of the main body is used. The objective of the two concepts is to reduce the reattachment length and thus the lever arm of the forces as well as to stabilize the separated shear layer. Using a boat tail, the reattachment length can be reduced by 50%. Furthermore, it is shown that the semi-circular lobes enhance the turbulent mixing and the shear layer growth rate. Hence, they significantly reduce the reattachment length by about 75%. The semi-circular lobes partially reduce undesired low-frequency pressure fluctuations on the nozzle surface. However, this reduction is achieved at the expense of an increase of high-frequency pressure fluctuations due to intensified small turbulent scales. The DMD analysis of the velocity field reveals that the large-scale coherent structures featuring a wave length of two step heights observed in the reference configuration without flow control can be suppressed by the lobes. The spanwise wave length of the coherent structures seems to depend on the geometry of the lobes, since all detected spatial DMD modes show a spanwise periodicity being equal to the distance between two lobes.
      PubDate: 2018-06-01
      DOI: 10.1007/s12567-017-0183-3
      Issue No: Vol. 10, No. 2 (2018)
  • Experimental assessment of the performance of ablative heat shield
           materials from plasma wind tunnel testing
    • Authors: S. Löhle; T. Hermann; F. Zander
      Pages: 203 - 211
      Abstract: A method for assessing the performance of typical heat shield materials is presented in this paper. Three different material samples, the DLR material Zuram, the Airbus material Asterm and the carbon preform Calcarb were tested in the IRS plasma wind tunnel PWK1 at the same nominal condition. State of the art diagnostic tools, i.e., surface temperature with pyrometry and thermography and boundary layer optical emission spectroscopy were completed by photogrammetric surface recession measurements. These data allow the assessment of the net heat flux for each material. The analysis shows that the three materials each have a different effect on heat flux mitigation with ASTERM showing the largest reduction in surface heat flux. The effect of pyrolysis and blowing is clearly observed and the heat flux reduction can be determined from an energy balance.
      PubDate: 2018-06-01
      DOI: 10.1007/s12567-017-0186-0
      Issue No: Vol. 10, No. 2 (2018)
  • Experimental validation of solid rocket motor damping models
    • Authors: Cristina Riso; Sebastiaan Fransen; Franco Mastroddi; Giuliano Coppotelli; Francesco Trequattrini; Alessio De Vivo
      Pages: 213 - 230
      Abstract: In design and certification of spacecraft, payload/launcher coupled load analyses are performed to simulate the satellite dynamic environment. To obtain accurate predictions, the system damping properties must be properly taken into account in the finite element model used for coupled load analysis. This is typically done using a structural damping characterization in the frequency domain, which is not applicable in the time domain. Therefore, the structural damping matrix of the system must be converted into an equivalent viscous damping matrix when a transient coupled load analysis is performed. This paper focuses on the validation of equivalent viscous damping methods for dynamically condensed finite element models via correlation with experimental data for a realistic structure representative of a slender launch vehicle with solid rocket motors. A second scope of the paper is to investigate how to conveniently choose a single combination of Young’s modulus and structural damping coefficient—complex Young’s modulus—to approximate the viscoelastic behavior of a solid propellant material in the frequency band of interest for coupled load analysis. A scaled-down test article inspired to the Z9-ignition Vega launcher configuration is designed, manufactured, and experimentally tested to obtain data for validation of the equivalent viscous damping methods. The Z9-like component of the test article is filled with a viscoelastic material representative of the Z9 solid propellant that is also preliminarily tested to investigate the dependency of the complex Young’s modulus on the excitation frequency and provide data for the test article finite element model. Experimental results from seismic and shock tests performed on the test configuration are correlated with numerical results from frequency and time domain analyses carried out on its dynamically condensed finite element model to assess the applicability of different equivalent viscous damping methods to describe damping properties of slender launch vehicles in payload/launcher coupled load analysis.
      PubDate: 2018-06-01
      DOI: 10.1007/s12567-017-0191-3
      Issue No: Vol. 10, No. 2 (2018)
  • Architectural elements of hybrid navigation systems for future space
    • Authors: Guilherme F. Trigo; Stephan Theil
      Pages: 231 - 250
      Abstract: The fundamental limitations of inertial navigation, currently employed by most launchers, have raised interest for GNSS-aided solutions. Combination of inertial measurements and GNSS outputs allows inertial calibration online, solving the issue of inertial drift. However, many challenges and design options unfold. In this work we analyse several architectural elements and design aspects of a hybrid GNSS/INS navigation system conceived for space transportation. The most fundamental architectural features such as coupling depth, modularity between filter and inertial propagation, and open-/closed-loop nature of the configuration, are discussed in the light of the envisaged application. Importance of the inertial propagation algorithm and sensor class in the overall system are investigated, being the handling of sensor errors and uncertainties that arise with lower grade sensory also considered. In terms of GNSS outputs we consider receiver solutions (position and velocity) and raw measurements (pseudorange, pseudorange-rate and time-difference carrier phase). Receiver clock error handling options and atmospheric error correction schemes for these measurements are analysed under flight conditions. System performance with different GNSS measurements is estimated through covariance analysis, being the differences between loose and tight coupling emphasized through partial outage simulation. Finally, we discuss options for filter algorithm robustness against non-linearities and system/measurement errors. A possible scheme for fault detection, isolation and recovery is also proposed.
      PubDate: 2018-06-01
      DOI: 10.1007/s12567-017-0187-z
      Issue No: Vol. 10, No. 2 (2018)
  • Multiple spacecraft configuration designs for coordinated flight missions
    • Authors: Federico Fumenti; Stephan Theil
      Pages: 251 - 271
      Abstract: Coordinated flight allows the replacement of a single monolithic spacecraft with multiple smaller ones, based on the principle of distributed systems. According to the mission objectives and to ensure a safe relative motion, constraints on the relative distances need to be satisfied. Initially, differential perturbations are limited by proper orbit design. Then, the induced differential drifts can be properly handled through corrective maneuvers. In this work, several designs are surveyed, defining the initial configuration of a group of spacecraft while counteracting the differential perturbations. For each of the investigated designs, focus is placed upon the number of deployable spacecraft and on the possibility to ensure safe relative motion through station keeping of the initial configuration, with particular attention to the required \(\varDelta V\) budget and the constraints violations.
      PubDate: 2018-06-01
      DOI: 10.1007/s12567-018-0193-9
      Issue No: Vol. 10, No. 2 (2018)
  • Finite element modelling and performance optimization of an ion thruster
           depending on the nature of the propellant
    • Authors: Ionuț-Florian Popa; Anna-Maria Theodora Andreescu; Dan Ifrim; Radu Mihalache; Dragoș Mihai; Grigore Cican
      Abstract: The electrostatic propulsion is a class of space propulsion which makes use of electrical power and this kind of systems are characterized by high exhaust velocities and specific impulse, enhancing the propulsive performances of thrusters compared to conventional chemical thrusters. Since the ionized particle exhaust velocity is a function of the ratio between the electrical charge and their molecular mass, the obvious solution is to use ions with low electrical charge–molecular mass ratio. Currently, the most used propellant for the space propulsion is the Xenon gas, as it has a series of important advantages, but is quite expensive when compared to other propellants. This paper aims to make an optimization of the ideal ion propulsion systems depending on the nature of the propellant, like common used substances in the space propulsion, but also other substances which are potential candidates for this application. A variety of ion thruster performances will be analyzed, such as force, specific impulse, efficiency for the same power available onboard, the same accelerating voltage, and the same ion current. Also, for the Xenon case a numerical simulation was performed to highlight the behavior and trajectory of the ionized particles and their velocity. The conclusion obtained following the study is that a reasonable ion thruster regarding the dimensions should use an accelerating potential of at least 4000 V and 2 A of ion current.
      PubDate: 2018-08-13
      DOI: 10.1007/s12567-018-0218-4
  • A GMSK VHF-uplink/UHF-downlink transceiver for the CubeSat missions
    • Authors: Yaseen Zaidi; Robert Ryk van Zyl; Norman G. Fitz-Coy
      Abstract: Functional and thermal performance characteristics of a very high frequency/ultra high frequency (VHF/UHF) transceiver based on Gaussian minimum shift keying (GMSK) modulation are presented. The transceiver has been designed for CubeSats telemetry and commanding needs or low rate data download. The design is validated at 27 dBm, 30 dBm and 33 dBm transmitting powers over −20 \(^\circ \hbox {C}\) to +51 \(^\circ \hbox {C}\) . Under these thermal conditions, the transmitter spurious dynamic response shows little if any change and the average sensitivity of receiver at the 12 dB signal noise and distortion (SINAD) is −116.7 dBm at 140 MHz and −116.78 dBm at 149.98 MHz. The transmitter and receiver frequencies are stable and the current consumption as well the output RF levels are steady. The design has been verified against a simulation model which allows system tradeoff analysis. The measurements demonstrate the transceiver made with commercial grade parts has dependable performance at the low earth altitudes and orbital heating conditions.
      PubDate: 2018-08-02
      DOI: 10.1007/s12567-018-0217-5
  • Computational modeling of nonlinear propellant sloshing for spacecraft
           AOCS applications
    • Authors: Manuel Hahn; Stefan Adami; Roger Förstner
      Abstract: During all operational phases, propellant sloshing may have a significant influence on spacecraft performance and stability. The proper description of propellant sloshing effects is then essential for the verification of the Attitude and Orbit Control System (AOCS). As soon as nonlinear effects predominate (e.g. for high-agility or in a micro-gravity environment), classical approaches as mechanical analog models (e.g. pendulums) fail and computational models need to be utilized to describe the propellant dynamics. These computational models currently lack the ability to accurately describe nonlinear effects like high-velocity impacts, as well as cohesion and adhesion forces in a micro-gravity environment. Additionally these models are computationally very expensive, so that they are commonly not directly used in AOCS verification campaigns, where a large number of simulations are performed. The scope of this work is the development of a computational model based on smoothed particle hydrodynamics, which is able to accurately describe nonlinear propellant sloshing effects in gravity-dominated regimes, which is of relevance for example for high-agility spacecraft missions. The newly developed code is validated using analytical expressions, experimental data as well as other numerical codes. Subsequently, a study is performed showing that the global variables like forces acting on the tank wall or the center of mass are still approximated reasonably well when using lower spatial resolutions, resulting in much faster simulation runs and making it feasible to use the computational model directly in AOCS verification campaigns. Finally, the coupling of the propellant sloshing code to an AOCS and Flight Dynamics rigid-body simulator is demonstrated by simulating a nonlinear forced-roll motion of a partially-filled tank under Earth-gravity.
      PubDate: 2018-08-01
      DOI: 10.1007/s12567-018-0216-6
  • Lunar landing navigation supported by ranging to an orbiter
    • Authors: Ennio Condoleo; Stephan Theil
      Abstract: Precise and safe landings on celestial bodies as the Moon are needed for the further exploration and potential future exploitation of solar system bodies. The current navigation systems for landing probes are based on sensor data fusion of inertial and optical sensor measurements to determine the current flight state with respect to the target body and the desired landing site. To improve the accuracy of lunar landing navigation, radiometric measurements (range and range-rate) with respect to an orbiting vehicle have been proposed in several studies. This paper analyzes the impact of range and range-rate measurements from an orbiting vehicle on the navigation accuracy. For that purpose, a baseline configuration of an optical navigation system is used which has already been taken as a reference for investigating the effect of ground-based beacons. First, the influence of the orbiter trajectory in relation to the landing trajectory is investigated. In particular, the line of sight between orbiter and lander permits a preliminary assessment of the navigation performance. Later, the effects of sensor noise for all measurements and of the orbiter ephemeris error are also evaluated. Finally, for a selected scenario, it is demonstrated that radiometric measurements with respect to an orbiter can reduce the positioning error by about 40%.
      PubDate: 2018-07-27
      DOI: 10.1007/s12567-018-0215-7
  • VHF Data Exchange System (VDES): an enabling technology for maritime
    • Authors: Francisco Lázaro; Ronald Raulefs; Wei Wang; Federico Clazzer; Simon Plass
      Abstract: This work presents an overview of the radio interface of VHF Data Exchange System (VDES), which is currently on its way to become an ITU standard supported by International Association of Marine Aids to Navigation and Lighthouse Authorities. VDES includes the already existing collision avoidance tracking system Automatic Identification System and the messaging system Application Specific Messages. Additionally, a new third component for digital maritime communications of any kind, named VHF Data Exchange is included. On the one hand, there is a traditional terrestrial component, on the other hand, a satellite communication link is also envisioned partly by the same spectrum usage. In this article, focus is given towards the technical design aspects and challenges of this hybrid communications transmission scheme.
      PubDate: 2018-07-20
      DOI: 10.1007/s12567-018-0214-8
  • Evaluating the stability of NASA’s space launch system with adaptive
           augmenting control
    • Authors: Tannen S. VanZwieten; Michael R. Hannan; John H. Wall
      Abstract: NASA’s baseline space launch system (SLS) flight control system (FCS) design includes an adaptive augmenting control (AAC) component that modifies the attitude control system response by augmenting the classical gain-scheduled architecture with additional performance and robustness. The NASA Engineering and Safety Center (NESC) teamed with the SLS Program to perform a comprehensive assessment of the stability and robustness of this FCS with emphasis on the AAC component. Multiple analysis techniques applicable to nonlinear systems were commissioned as part of this assessment, which was conducted in parallel with the program’s standard design analysis cycle. The following analyses were included, with each technique adding unique valuable insights: Lyapunov-based stability analysis, classical stability analysis with static AAC gain variations, circle criterion-based analysis of the FCS with a time-varying gain element, time-domain stability margin assessment, Monte Carlo simulations with expanded dispersions, and an extensive set of stressing cases. Several of the completed analyses focused on determining whether the inclusion of AAC introduced risk to the FCS, while others quantified the benefits of the adaptive augmentation.
      PubDate: 2018-06-28
      DOI: 10.1007/s12567-018-0211-y
  • AOCS design for the ATHENA X-ray telescope: challenges and solutions
    • Authors: T. Ott; S. Goerries; A. Schleicher; S. Winkler
      Abstract: The ATHENA—Advanced Telescope for High-ENergy Astrophysics—mission is currently assessed in a phase A feasibility study as L-class mission in ESA’s Cosmic Vision 2015–2025 plan, with launch foreseen in 2028. Primary mission goal is the mapping of hot gas structures and the determination of their physical properties to search for supermassive black holes. ATHENA is an X-ray telescope with a focal length of 12 m. It has a mass of ~ 7000 kg and it is ~ 15 m high with a diameter of ~ 3 m. The main mass is distributed to the mirror on the one side of the spacecraft and to the science instrument module on the other side of the spacecraft. To achieve its science goals, ATHENA performs a sky survey with precision line-of-sight pointing requirements in the order of arc seconds for absolute pointing and sub-arc seconds for relative pointing in time windows > 1 ks, all at 95% confidence level. That is very demanding for large X-ray telescopes. In addition to the precision pointing requirements, ATHENA cannot violate a certain sun exclusion zone. This is a hard constraint to prevent any stray-light falling onto the instruments, as it would immediately destroy them. The sky survey is defined by an observation plan that is demanding in terms of availability and thus spacecraft agility. The pointing and agility requirements and the fact that ATHENA is a spacecraft with high mass and volume introduce several design challenges for the attitude and orbit control system. This paper presents those challenges, corresponding solutions, and preliminary results, which have been achieved during the phase A study led by Airbus in Friedrichshafen, Germany. The main focus and contribution of this paper are the identification of research and development needs for attitude and orbit control systems to enable the ATHENA mission. In this respect, the ATHENA design challenges are discussed and addressed with the state-of-the-art design methods. This paper concludes with the main identified technology development needs and formulates specific research questions related to practical design problems. In particular, the following attitude and orbit control system design challenges are addressed: autonomous and agile large angle slew manoeuvres with exclusion zones, availability for science observations, precision line-of-sight determination as well as analysis during the design process using the ESA Pointing Error Engineering Tool and pointing control with a hexapod as line-of-sight actuator in the control loop. The last challenge, namely, the hexapod in the control loop, is without precedence in Europe and to the best knowledge of the authors in the world.
      PubDate: 2018-06-28
      DOI: 10.1007/s12567-018-0213-9
  • Beyond L ∞ reaction wheel commanding: increased on-board autonomy
           through enhanced wheel failure handling
    • Authors: Stefan Winkler; Maik Evers; Benjamin Kraft
      Abstract: Latest large spacecraft and/or agility requirements have led to configurations of five or more reaction wheels. To avoid (1) handling a significant amount of pre-stored parameters on board and (2) intervening by ground (classical approach) to recover single- and multiple-wheel failures, the orthogonal null space basis must be robustly computed on board. Two deterministic methods are presented in this paper: (1) via virtual torque commands using L∞ and L2 commanding, (2) via generalized inverse. Furthermore, a cascading null space control approach that autonomously respects predefined wheel momentum operating bands is introduced. The presented work is dedicated to the demand of high on-board autonomy driven by more and more customers requiring just a working spacecraft with minimum interventions by ground. The presented solutions are already part of the Airbus high-power satellite avionics system Astrobus AS400 for current and future missions such as MetOp-SG. Furthermore, the presented functionalities are essential towards on-board real-time spacecraft reconfiguration which is; however, beyond the scope of this paper.
      PubDate: 2018-06-18
      DOI: 10.1007/s12567-018-0212-x
  • Sentinel-1 near real-time application for maritime situational awareness
    • Authors: Detmar Krause; Egbert Schwarz; Sergey Voinov; Heiko Damerow; Daniel Tomecki
      Abstract: In the context of the project real-time services for maritime security (Echtzeitdienste für die Maritime Sicherheit—security), an experimental research platform for validation of maritime products derived from remote sensing data, was developed. This article describes the work carried out to derive ship-, wind-, and wave detection products out of Sentinel-1 remote-sensing data by DLR’s Maritime Safety and Security Lab in Neustrelitz, part of the German Remote Data Center DFD. The activity aims to the fulfilment of project requirements, primarily to support the need for near real-time performance up to 15 min, as those in maritime situational awareness. The development and implementation cover the task of level 0 processing, based on DLR’s front end processor, the implementation of the framework for real-time processing up to level 2 (value adding), as well as the development of a hardware-independent virtual-processing platform.
      PubDate: 2018-06-13
      DOI: 10.1007/s12567-018-0210-z
  • Thank you to our CEAS Space Journal Reviewers
    • PubDate: 2018-03-08
      DOI: 10.1007/s12567-018-0198-4
  • Autonomous vision-based navigation for proximity operations around binary
    • Authors: Jesus Gil-Fernandez; Guillermo Ortega-Hernando
      Abstract: Future missions to small bodies demand higher level of autonomy in the Guidance, Navigation and Control system for higher scientific return and lower operational costs. Different navigation strategies have been assessed for ESA’s asteroid impact mission (AIM). The main objective of AIM is the detailed characterization of binary asteroid Didymos. The trajectories for the proximity operations shall be intrinsically safe, i.e., no collision in presence of failures (e.g., spacecraft entering safe mode), perturbations (e.g., non-spherical gravity field), and errors (e.g., maneuver execution error). Hyperbolic arcs with sufficient hyperbolic excess velocity are designed to fulfil the safety, scientific, and operational requirements. The trajectory relative to the asteroid is determined using visual camera images. The ground-based trajectory prediction error at some points is comparable to the camera Field Of View (FOV). Therefore, some images do not contain the entire asteroid. Autonomous navigation can update the state of the spacecraft relative to the asteroid at higher frequency. The objective of the autonomous navigation is to improve the on-board knowledge compared to the ground prediction. The algorithms shall fit in off-the-shelf, space-qualified avionics. This note presents suitable image processing and relative-state filter algorithms for autonomous navigation in proximity operations around binary asteroids.
      PubDate: 2018-02-23
      DOI: 10.1007/s12567-018-0197-5
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