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Showing 1 - 200 of 3043 Journals sorted alphabetically
AASRI Procedia     Open Access   (Followers: 15)
Academic Pediatrics     Hybrid Journal   (Followers: 22, SJR: 1.402, h-index: 51)
Academic Radiology     Hybrid Journal   (Followers: 21, SJR: 1.008, h-index: 75)
Accident Analysis & Prevention     Partially Free   (Followers: 84, SJR: 1.109, h-index: 94)
Accounting Forum     Hybrid Journal   (Followers: 25, SJR: 0.612, h-index: 27)
Accounting, Organizations and Society     Hybrid Journal   (Followers: 30, SJR: 2.515, h-index: 90)
Achievements in the Life Sciences     Open Access   (Followers: 4)
Acta Anaesthesiologica Taiwanica     Open Access   (Followers: 5, SJR: 0.338, h-index: 19)
Acta Astronautica     Hybrid Journal   (Followers: 348, SJR: 0.726, h-index: 43)
Acta Automatica Sinica     Full-text available via subscription   (Followers: 3)
Acta Biomaterialia     Hybrid Journal   (Followers: 25, SJR: 2.02, h-index: 104)
Acta Colombiana de Cuidado Intensivo     Full-text available via subscription   (Followers: 1)
Acta de Investigación Psicológica     Open Access   (Followers: 2)
Acta Ecologica Sinica     Open Access   (Followers: 8, SJR: 0.172, h-index: 29)
Acta Haematologica Polonica     Free   (SJR: 0.123, h-index: 8)
Acta Histochemica     Hybrid Journal   (Followers: 3, SJR: 0.604, h-index: 38)
Acta Materialia     Hybrid Journal   (Followers: 252, SJR: 3.683, h-index: 202)
Acta Mathematica Scientia     Full-text available via subscription   (Followers: 5, SJR: 0.615, h-index: 21)
Acta Mechanica Solida Sinica     Full-text available via subscription   (Followers: 9, SJR: 0.442, h-index: 21)
Acta Oecologica     Hybrid Journal   (Followers: 10, SJR: 0.915, h-index: 53)
Acta Otorrinolaringologica (English Edition)     Full-text available via subscription   (Followers: 1)
Acta Otorrinolaringológica Española     Full-text available via subscription   (Followers: 3, SJR: 0.311, h-index: 16)
Acta Pharmaceutica Sinica B     Open Access   (Followers: 2)
Acta Poética     Open Access   (Followers: 4)
Acta Psychologica     Hybrid Journal   (Followers: 23, SJR: 1.365, h-index: 73)
Acta Sociológica     Open Access  
Acta Tropica     Hybrid Journal   (Followers: 6, SJR: 1.059, h-index: 77)
Acta Urológica Portuguesa     Open Access  
Actas Dermo-Sifiliograficas     Full-text available via subscription   (Followers: 4)
Actas Dermo-Sifiliográficas (English Edition)     Full-text available via subscription   (Followers: 3)
Actas Urológicas Españolas     Full-text available via subscription   (Followers: 4, SJR: 0.383, h-index: 19)
Actas Urológicas Españolas (English Edition)     Full-text available via subscription   (Followers: 2)
Actualites Pharmaceutiques     Full-text available via subscription   (Followers: 5, SJR: 0.141, h-index: 3)
Actualites Pharmaceutiques Hospitalieres     Full-text available via subscription   (Followers: 4, SJR: 0.112, h-index: 2)
Acupuncture and Related Therapies     Hybrid Journal   (Followers: 4)
Acute Pain     Full-text available via subscription   (Followers: 13)
Ad Hoc Networks     Hybrid Journal   (Followers: 11, SJR: 0.967, h-index: 57)
Addictive Behaviors     Hybrid Journal   (Followers: 15, SJR: 1.514, h-index: 92)
Addictive Behaviors Reports     Open Access   (Followers: 5)
Additive Manufacturing     Hybrid Journal   (Followers: 7, SJR: 1.039, h-index: 5)
Additives for Polymers     Full-text available via subscription   (Followers: 21)
Advanced Drug Delivery Reviews     Hybrid Journal   (Followers: 135, SJR: 5.2, h-index: 222)
Advanced Engineering Informatics     Hybrid Journal   (Followers: 11, SJR: 1.265, h-index: 53)
Advanced Powder Technology     Hybrid Journal   (Followers: 17, SJR: 0.739, h-index: 33)
Advances in Accounting     Hybrid Journal   (Followers: 9, SJR: 0.299, h-index: 15)
Advances in Agronomy     Full-text available via subscription   (Followers: 15, SJR: 2.071, h-index: 82)
Advances in Anesthesia     Full-text available via subscription   (Followers: 25, SJR: 0.169, h-index: 4)
Advances in Antiviral Drug Design     Full-text available via subscription   (Followers: 3)
Advances in Applied Mathematics     Full-text available via subscription   (Followers: 6, SJR: 1.054, h-index: 35)
Advances in Applied Mechanics     Full-text available via subscription   (Followers: 11, SJR: 0.801, h-index: 26)
Advances in Applied Microbiology     Full-text available via subscription   (Followers: 22, SJR: 1.286, h-index: 49)
Advances In Atomic, Molecular, and Optical Physics     Full-text available via subscription   (Followers: 16, SJR: 3.31, h-index: 42)
Advances in Biological Regulation     Hybrid Journal   (Followers: 4, SJR: 2.277, h-index: 43)
Advances in Botanical Research     Full-text available via subscription   (Followers: 3, SJR: 0.619, h-index: 48)
Advances in Cancer Research     Full-text available via subscription   (Followers: 25, SJR: 2.215, h-index: 78)
Advances in Carbohydrate Chemistry and Biochemistry     Full-text available via subscription   (Followers: 9, SJR: 0.9, h-index: 30)
Advances in Catalysis     Full-text available via subscription   (Followers: 5, SJR: 2.139, h-index: 42)
Advances in Cellular and Molecular Biology of Membranes and Organelles     Full-text available via subscription   (Followers: 12)
Advances in Chemical Engineering     Full-text available via subscription   (Followers: 26, SJR: 0.183, h-index: 23)
Advances in Child Development and Behavior     Full-text available via subscription   (Followers: 10, SJR: 0.665, h-index: 29)
Advances in Chronic Kidney Disease     Full-text available via subscription   (Followers: 9, SJR: 1.268, h-index: 45)
Advances in Clinical Chemistry     Full-text available via subscription   (Followers: 29, SJR: 0.938, h-index: 33)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 18, SJR: 2.314, h-index: 130)
Advances in Computers     Full-text available via subscription   (Followers: 16, SJR: 0.223, h-index: 22)
Advances in Dermatology     Full-text available via subscription   (Followers: 12)
Advances in Developmental Biology     Full-text available via subscription   (Followers: 11)
Advances in Digestive Medicine     Open Access   (Followers: 6)
Advances in DNA Sequence-Specific Agents     Full-text available via subscription   (Followers: 5)
Advances in Drug Research     Full-text available via subscription   (Followers: 22)
Advances in Ecological Research     Full-text available via subscription   (Followers: 41, SJR: 3.25, h-index: 43)
Advances in Engineering Software     Hybrid Journal   (Followers: 25, SJR: 0.486, h-index: 10)
Advances in Experimental Biology     Full-text available via subscription   (Followers: 7)
Advances in Experimental Social Psychology     Full-text available via subscription   (Followers: 41, SJR: 5.465, h-index: 64)
Advances in Exploration Geophysics     Full-text available via subscription   (Followers: 3)
Advances in Food and Nutrition Research     Full-text available via subscription   (Followers: 50, SJR: 0.674, h-index: 38)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 16)
Advances in Genetics     Full-text available via subscription   (Followers: 15, SJR: 2.558, h-index: 54)
Advances in Genome Biology     Full-text available via subscription   (Followers: 11)
Advances in Geophysics     Full-text available via subscription   (Followers: 6, SJR: 2.325, h-index: 20)
Advances in Heat Transfer     Full-text available via subscription   (Followers: 22, SJR: 0.906, h-index: 24)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 9, SJR: 0.497, h-index: 31)
Advances in Imaging and Electron Physics     Full-text available via subscription   (Followers: 2, SJR: 0.396, h-index: 27)
Advances in Immunology     Full-text available via subscription   (Followers: 35, SJR: 4.152, h-index: 85)
Advances in Inorganic Chemistry     Full-text available via subscription   (Followers: 9, SJR: 1.132, h-index: 42)
Advances in Insect Physiology     Full-text available via subscription   (Followers: 3, SJR: 1.274, h-index: 27)
Advances in Integrative Medicine     Hybrid Journal   (Followers: 6)
Advances in Life Course Research     Hybrid Journal   (Followers: 8, SJR: 0.764, h-index: 15)
Advances in Lipobiology     Full-text available via subscription   (Followers: 2)
Advances in Magnetic and Optical Resonance     Full-text available via subscription   (Followers: 9)
Advances in Marine Biology     Full-text available via subscription   (Followers: 15, SJR: 1.645, h-index: 45)
Advances in Mathematics     Full-text available via subscription   (Followers: 10, SJR: 3.261, h-index: 65)
Advances in Medical Sciences     Hybrid Journal   (Followers: 6, SJR: 0.489, h-index: 25)
Advances in Medicinal Chemistry     Full-text available via subscription   (Followers: 5)
Advances in Microbial Physiology     Full-text available via subscription   (Followers: 4, SJR: 1.44, h-index: 51)
Advances in Molecular and Cell Biology     Full-text available via subscription   (Followers: 22)
Advances in Molecular and Cellular Endocrinology     Full-text available via subscription   (Followers: 10)
Advances in Molecular Toxicology     Full-text available via subscription   (Followers: 7, SJR: 0.324, h-index: 8)
Advances in Nanoporous Materials     Full-text available via subscription   (Followers: 4)
Advances in Oncobiology     Full-text available via subscription   (Followers: 3)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 15, SJR: 2.885, h-index: 45)
Advances in Parallel Computing     Full-text available via subscription   (Followers: 7, SJR: 0.148, h-index: 11)
Advances in Parasitology     Full-text available via subscription   (Followers: 7, SJR: 2.37, h-index: 73)
Advances in Pediatrics     Full-text available via subscription   (Followers: 24, SJR: 0.4, h-index: 28)
Advances in Pharmaceutical Sciences     Full-text available via subscription   (Followers: 13)
Advances in Pharmacology     Full-text available via subscription   (Followers: 15, SJR: 1.718, h-index: 58)
Advances in Physical Organic Chemistry     Full-text available via subscription   (Followers: 8, SJR: 0.384, h-index: 26)
Advances in Phytomedicine     Full-text available via subscription  
Advances in Planar Lipid Bilayers and Liposomes     Full-text available via subscription   (Followers: 3, SJR: 0.248, h-index: 11)
Advances in Plant Biochemistry and Molecular Biology     Full-text available via subscription   (Followers: 8)
Advances in Plant Pathology     Full-text available via subscription   (Followers: 5)
Advances in Porous Media     Full-text available via subscription   (Followers: 4)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 17)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 20, SJR: 1.5, h-index: 62)
Advances in Psychology     Full-text available via subscription   (Followers: 61)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 5, SJR: 0.478, h-index: 32)
Advances in Radiation Oncology     Open Access  
Advances in Small Animal Medicine and Surgery     Hybrid Journal   (Followers: 3, SJR: 0.1, h-index: 2)
Advances in Space Research     Full-text available via subscription   (Followers: 353, SJR: 0.606, h-index: 65)
Advances in Structural Biology     Full-text available via subscription   (Followers: 8)
Advances in Surgery     Full-text available via subscription   (Followers: 7, SJR: 0.823, h-index: 27)
Advances in the Study of Behavior     Full-text available via subscription   (Followers: 30, SJR: 1.321, h-index: 56)
Advances in Veterinary Medicine     Full-text available via subscription   (Followers: 17)
Advances in Veterinary Science and Comparative Medicine     Full-text available via subscription   (Followers: 13)
Advances in Virus Research     Full-text available via subscription   (Followers: 5, SJR: 1.878, h-index: 68)
Advances in Water Resources     Hybrid Journal   (Followers: 43, SJR: 2.408, h-index: 94)
Aeolian Research     Hybrid Journal   (Followers: 5, SJR: 0.973, h-index: 22)
Aerospace Science and Technology     Hybrid Journal   (Followers: 326, SJR: 0.816, h-index: 49)
AEU - Intl. J. of Electronics and Communications     Hybrid Journal   (Followers: 8, SJR: 0.318, h-index: 36)
African J. of Emergency Medicine     Open Access   (Followers: 5, SJR: 0.344, h-index: 6)
Ageing Research Reviews     Hybrid Journal   (Followers: 8, SJR: 3.289, h-index: 78)
Aggression and Violent Behavior     Hybrid Journal   (Followers: 405, SJR: 1.385, h-index: 72)
Agri Gene     Hybrid Journal  
Agricultural and Forest Meteorology     Hybrid Journal   (Followers: 15, SJR: 2.18, h-index: 116)
Agricultural Systems     Hybrid Journal   (Followers: 30, SJR: 1.275, h-index: 74)
Agricultural Water Management     Hybrid Journal   (Followers: 39, SJR: 1.546, h-index: 79)
Agriculture and Agricultural Science Procedia     Open Access  
Agriculture and Natural Resources     Open Access   (Followers: 1)
Agriculture, Ecosystems & Environment     Hybrid Journal   (Followers: 54, SJR: 1.879, h-index: 120)
Ain Shams Engineering J.     Open Access   (Followers: 5, SJR: 0.434, h-index: 14)
Air Medical J.     Hybrid Journal   (Followers: 5, SJR: 0.234, h-index: 18)
AKCE Intl. J. of Graphs and Combinatorics     Open Access   (SJR: 0.285, h-index: 3)
Alcohol     Hybrid Journal   (Followers: 10, SJR: 0.922, h-index: 66)
Alcoholism and Drug Addiction     Open Access   (Followers: 8)
Alergologia Polska : Polish J. of Allergology     Full-text available via subscription   (Followers: 1)
Alexandria Engineering J.     Open Access   (Followers: 1, SJR: 0.436, h-index: 12)
Alexandria J. of Medicine     Open Access  
Algal Research     Partially Free   (Followers: 8, SJR: 2.05, h-index: 20)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 3)
Allergologia et Immunopathologia     Full-text available via subscription   (Followers: 1, SJR: 0.46, h-index: 29)
Allergology Intl.     Open Access   (Followers: 4, SJR: 0.776, h-index: 35)
Alpha Omegan     Full-text available via subscription   (SJR: 0.121, h-index: 9)
ALTER - European J. of Disability Research / Revue Européenne de Recherche sur le Handicap     Full-text available via subscription   (Followers: 8, SJR: 0.158, h-index: 9)
Alzheimer's & Dementia     Hybrid Journal   (Followers: 48, SJR: 4.289, h-index: 64)
Alzheimer's & Dementia: Diagnosis, Assessment & Disease Monitoring     Open Access   (Followers: 6)
Alzheimer's & Dementia: Translational Research & Clinical Interventions     Open Access   (Followers: 5)
American Heart J.     Hybrid Journal   (Followers: 49, SJR: 3.157, h-index: 153)
American J. of Cardiology     Hybrid Journal   (Followers: 47, SJR: 2.063, h-index: 186)
American J. of Emergency Medicine     Hybrid Journal   (Followers: 39, SJR: 0.574, h-index: 65)
American J. of Geriatric Pharmacotherapy     Full-text available via subscription   (Followers: 8, SJR: 1.091, h-index: 45)
American J. of Geriatric Psychiatry     Hybrid Journal   (Followers: 15, SJR: 1.653, h-index: 93)
American J. of Human Genetics     Hybrid Journal   (Followers: 31, SJR: 8.769, h-index: 256)
American J. of Infection Control     Hybrid Journal   (Followers: 25, SJR: 1.259, h-index: 81)
American J. of Kidney Diseases     Hybrid Journal   (Followers: 32, SJR: 2.313, h-index: 172)
American J. of Medicine     Hybrid Journal   (Followers: 45, SJR: 2.023, h-index: 189)
American J. of Medicine Supplements     Full-text available via subscription   (Followers: 3)
American J. of Obstetrics and Gynecology     Hybrid Journal   (Followers: 250, SJR: 2.255, h-index: 171)
American J. of Ophthalmology     Hybrid Journal   (Followers: 57, SJR: 2.803, h-index: 148)
American J. of Ophthalmology Case Reports     Open Access   (Followers: 5)
American J. of Orthodontics and Dentofacial Orthopedics     Full-text available via subscription   (Followers: 6, SJR: 1.249, h-index: 88)
American J. of Otolaryngology     Hybrid Journal   (Followers: 25, SJR: 0.59, h-index: 45)
American J. of Pathology     Hybrid Journal   (Followers: 26, SJR: 2.653, h-index: 228)
American J. of Preventive Medicine     Hybrid Journal   (Followers: 22, SJR: 2.764, h-index: 154)
American J. of Surgery     Hybrid Journal   (Followers: 34, SJR: 1.286, h-index: 125)
American J. of the Medical Sciences     Hybrid Journal   (Followers: 12, SJR: 0.653, h-index: 70)
Ampersand : An Intl. J. of General and Applied Linguistics     Open Access   (Followers: 5)
Anaerobe     Hybrid Journal   (Followers: 4, SJR: 1.066, h-index: 51)
Anaesthesia & Intensive Care Medicine     Full-text available via subscription   (Followers: 57, SJR: 0.124, h-index: 9)
Anaesthesia Critical Care & Pain Medicine     Full-text available via subscription   (Followers: 11)
Anales de Cirugia Vascular     Full-text available via subscription  
Anales de Pediatría     Full-text available via subscription   (Followers: 2, SJR: 0.209, h-index: 27)
Anales de Pediatría (English Edition)     Full-text available via subscription  
Anales de Pediatría Continuada     Full-text available via subscription   (SJR: 0.104, h-index: 3)
Analytic Methods in Accident Research     Hybrid Journal   (Followers: 4, SJR: 2.577, h-index: 7)
Analytica Chimica Acta     Hybrid Journal   (Followers: 37, SJR: 1.548, h-index: 152)
Analytical Biochemistry     Hybrid Journal   (Followers: 167, SJR: 0.725, h-index: 154)
Analytical Chemistry Research     Open Access   (Followers: 8, SJR: 0.18, h-index: 2)
Analytical Spectroscopy Library     Full-text available via subscription   (Followers: 11)
Anesthésie & Réanimation     Full-text available via subscription   (Followers: 1)
Anesthesiology Clinics     Full-text available via subscription   (Followers: 22, SJR: 0.421, h-index: 40)
Angiología     Full-text available via subscription   (SJR: 0.124, h-index: 9)
Angiologia e Cirurgia Vascular     Open Access  
Animal Behaviour     Hybrid Journal   (Followers: 160, SJR: 1.907, h-index: 126)
Animal Feed Science and Technology     Hybrid Journal   (Followers: 5, SJR: 1.151, h-index: 83)
Animal Reproduction Science     Hybrid Journal   (Followers: 5, SJR: 0.711, h-index: 78)
Annales d'Endocrinologie     Full-text available via subscription   (Followers: 1, SJR: 0.394, h-index: 30)
Annales d'Urologie     Full-text available via subscription  
Annales de Cardiologie et d'Angéiologie     Full-text available via subscription   (SJR: 0.177, h-index: 13)
Annales de Chirurgie de la Main et du Membre Supérieur     Full-text available via subscription  
Annales de Chirurgie Plastique Esthétique     Full-text available via subscription   (Followers: 2, SJR: 0.354, h-index: 22)
Annales de Chirurgie Vasculaire     Full-text available via subscription   (Followers: 1)

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Journal Cover Acta Astronautica
  [SJR: 0.726]   [H-I: 43]   [348 followers]  Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0094-5765
   Published by Elsevier Homepage  [3043 journals]
  • Red Dragon drill missions to Mars
    • Authors: Jennifer L. Heldmann; Carol R. Stoker; Andrew Gonzales; Christopher P. McKay; Alfonso Davila; Brian J. Glass; Larry L. Lemke; Gale Paulsen; David Willson; Kris Zacny
      Abstract: Publication date: December 2017
      Source:Acta Astronautica, Volume 141
      Author(s): Jennifer L. Heldmann, Carol R. Stoker, Andrew Gonzales, Christopher P. McKay, Alfonso Davila, Brian J. Glass, Larry L. Lemke, Gale Paulsen, David Willson, Kris Zacny
      We present the concept of using a variant of a Space Exploration Technologies Corporation (SpaceX) Dragon space capsule as a low-cost, large-capacity, near-term, Mars lander (dubbed “Red Dragon”) for scientific and human precursor missions. SpaceX initially designed the Dragon capsule for flight near Earth, and Dragon has successfully flown many times to low-Earth orbit (LEO) and successfully returned the Dragon spacecraft to Earth. Here we present capsule hardware modifications that are required to enable flight to Mars and operations on the martian surface. We discuss the use of the Dragon system to support NASA Discovery class missions to Mars and focus in particular on Dragon's applications for drilling missions. We find that a Red Dragon platform is well suited for missions capable of drilling deeper on Mars (at least 2 m) than has been accomplished to date due to its ability to land in a powered controlled mode, accommodate a long drill string, and provide payload space for sample processing and analysis. We show that a Red Dragon drill lander could conduct surface missions at three possible targets including the ice-cemented ground at the Phoenix landing site (68 °N), the subsurface ice discovered near the Viking 2 (49 °N) site by fresh impact craters, and the dark sedimentary subsurface material at the Curiosity site (4.5 °S).

      PubDate: 2017-10-07T22:36:59Z
      DOI: 10.1016/j.actaastro.2017.10.002
      Issue No: Vol. 141 (2017)
  • Study on the criterion to determine the bottom deployment modes of a
           coilable mast
    • Authors: Haibo Ma; Hai Huang; Jianbin Han; Wei Zhang; Xinsheng Wang
      Abstract: Publication date: December 2017
      Source:Acta Astronautica, Volume 141
      Author(s): Haibo Ma, Hai Huang, Jianbin Han, Wei Zhang, Xinsheng Wang
      A practical design criterion that allows the coilable mast bottom to deploy in local coil mode was proposed. The criterion was defined with initial bottom helical angle and obtained by bottom deformation analyses. Discretizing the longerons into short rods, analyses were conducted based on the cylinder assumption and Kirchhoff's kinetic analogy theory. Then, iterative calculations aiming at the bottom four rods were carried out. A critical bottom helical angle was obtained while the angle changing rate equaled to zero. The critical value was defined as a criterion for judgement of bottom deployment mode. Subsequently, micro-gravity deployment tests were carried out and bottom deployment simulations based on finite element method were developed. Through comparisons of bottom helical angles in critical state, the proposed criterion was evaluated and modified, that is, an initial bottom helical angle less than critical value with a design margin of −13.7% could ensure the mast bottom deploying in local coil mode, and further determine a successful local coil deployment of entire coilable mast.

      PubDate: 2017-10-07T22:36:59Z
      DOI: 10.1016/j.actaastro.2017.09.035
      Issue No: Vol. 141 (2017)
  • Detumbling control for kinematically redundant space manipulator
           post-grasping a rotational satellite
    • Authors: Mingming Wang; Jianjun Luo; Jianping Yuan; Ulrich Walter
      Abstract: Publication date: December 2017
      Source:Acta Astronautica, Volume 141
      Author(s): Mingming Wang, Jianjun Luo, Jianping Yuan, Ulrich Walter
      The objective of this paper is to establish a detumbling strategy and a coordination control scheme for a kinematically redundant space manipulator post-grasping a rotational satellite. First, the dynamics of the kinematically redundant space robot after grasping the target is presented, which lays the foundation for the coordination controller design. Subsequently, optimal detumbling and motion planning strategy for the post-capture phase is proposed based on the quartic Bézier curves and adaptive differential evolution (DE) algorithm subject to the specific constraints. Both detumbling time and control torques are taken into account for the generation of the optimal detumbling strategy. Furthermore, a coordination control scheme is presented to track the designed reference path while regulating the attitude of the chaser to a desired value, which successfully dumps the initial angular velocity of the rotational satellite and controls the base attitude synchronously. Simulation results are presented for detumbling a target with rotational motion using a 7 degree-of-freedom (DOF) redundant space manipulator, which demonstrates the effectiveness of the proposed method.

      PubDate: 2017-10-07T22:36:59Z
      DOI: 10.1016/j.actaastro.2017.09.025
      Issue No: Vol. 141 (2017)
  • Numerical and experimental investigation of the effect of geometry on
           combustion characteristics of solid-fuel ramjet
    • Authors: Lunkun Gong; Xiong Chen; Omer Musa; Haitao Yang; Changsheng Zhou
      Abstract: Publication date: December 2017
      Source:Acta Astronautica, Volume 141
      Author(s): Lunkun Gong, Xiong Chen, Omer Musa, Haitao Yang, Changsheng Zhou
      Numerical and experimental investigation on the solid-fuel ramjet was carried out to study the effect of geometry on combustion characteristics. The two-dimensional axisymmetric program developed in the present study adopted finite rate chemistry and second-order moment turbulence-chemistry models, together with k-ω shear stress transport (SST) turbulence model. Experimental data were obtained by burning cylindrical polyethylene using a connected pipe facility. The simulation results show that a fuel-rich zone near the solid fuel surface and an air-rich zone in the core exist in the chamber, and the chemical reactions occur mainly in the interface of this two regions; The physical reasons for the effect of geometry on regression rate is the variation of turbulent viscosity due to the geometry change. Port-to-inlet diameter ratio is the main parameter influencing the turbulent viscosity, and a linear relationship between port-to-inlet diameter and regression rate were obtained. The air mass flow rate and air-fuel ratio are the main influencing factors on ramjet performances. Based on the simulation results, the correlations between geometry and air-fuel ratio were obtained, and the effect of geometry on ramjet performances was analyzed according to the correlation. Three-dimensional regression rate contour obtained experimentally indicates that the regression rate which shows axisymmetric distribution due to the symmetry structure increases sharply, followed by slow decrease in axial direction. The radiation heat transfer in recirculation zone cannot be ignored. Compared with the experimental results, the deviations of calculated average regression rate and characteristic velocity are about 5%. Concerning the effect of geometry on air-fuel ratio, the deviations between experimental and theoretical results are less than 10%.

      PubDate: 2017-10-07T22:36:59Z
      DOI: 10.1016/j.actaastro.2017.09.027
      Issue No: Vol. 141 (2017)
  • Concept design and cluster control of advanced space connectable
           intelligent microsatellite
    • Authors: Xiaohui Wang; Shuang Li; Yuchen She
      Pages: 1 - 7
      Abstract: Publication date: December 2017
      Source:Acta Astronautica, Volume 141
      Author(s): Xiaohui Wang, Shuang Li, Yuchen She
      In this note, a new type of advanced space connectable intelligent microsatellite is presented to extend the range of potential application of microsatellite and improve the efficiency of cooperation. First, the overall concept of the micro satellite cluster is described, which is characterized by autonomously connecting with each other and being able to realize relative rotation through the external interfaces. Second, the multi-satellite autonomous assembly algorithm and control algorithm of the cluster motion are developed to make the cluster system combine into a variety of configurations in order to achieve different types of functionality. Finally, the design of the satellite cluster system is proposed, and the possible applications are discussed.

      PubDate: 2017-09-30T07:51:11Z
      DOI: 10.1016/j.actaastro.2017.09.024
      Issue No: Vol. 141 (2017)
  • The Phobos-Grunt microgravity soil preparation system
    • Authors: Kai-leung Yung; Chi Wo Lam; Sui Man Ko; James Abbott Foster
      Pages: 22 - 29
      Abstract: Publication date: December 2017
      Source:Acta Astronautica, Volume 141
      Author(s): Kai-leung Yung, Chi Wo Lam, Sui Man Ko, James Abbott Foster
      To understand the composition of regolith on distant bodies it is important to make quantitative measurement of its composition. However, many instruments on board space missions can only make qualitative measurements. The SOil Preparation SYStem (SOPSYS) designed for the Phobos-grunt mission in 2011 was a unique spacecraft subsystem that can grind, sieve, transport and measure samples of regolith in the absence of gravity. Its mission was to produce a compact plug of regolith sample composed of particles no larger than 1 mm for a gas analytic package. It delivers a sample with specified volume enabling a quantitative analysis of the volatiles produced at different temperatures through heating. To minimize cross contamination, SOPSYS self-cleans after each sample is delivered. The apparatus was a cooperative development between China and Russia for the Phobos-Grunt mission to the Martian moon Phobos and will be reused on the upcoming reattempt of that mission and other similar missions. The paper presents an overview of the subsystem and the results of qualification model testing. The flight unit of SOPSYS has a low mass of 622 g including control electronics and compact dimensions of 247 mm by 102 mm by 45 mm.

      PubDate: 2017-09-30T07:51:11Z
      DOI: 10.1016/j.actaastro.2017.09.026
      Issue No: Vol. 141 (2017)
  • Effects of materials surface preparation for use in spacecraft potable
           water storage tanks
    • Authors: William T. Wallace; Sarah L. Wallace; Leslie J. Loh; C.K. Mike Kuo; Edgar K. Hudson; Tyler J. Marlar; Daniel B. Gazda
      Pages: 30 - 35
      Abstract: Publication date: December 2017
      Source:Acta Astronautica, Volume 141
      Author(s): William T. Wallace, Sarah L. Wallace, Leslie J. Loh, C.K. Mike Kuo, Edgar K. Hudson, Tyler J. Marlar, Daniel B. Gazda
      Maintaining a safe supply of potable water is of utmost importance when preparing for long-duration spaceflight missions, with the minimization of microbial growth being one major aspect. While biocides, such as ionic silver, historically have been used for microbial control in spaceflight, their effectiveness is sometimes limited due to surface reactions with the materials of the storage containers that reduce their concentrations below the effective range. For the Multi-Purpose Crew Vehicle, the primary wetted materials of the water storage system are stainless steel and a titanium alloy, and ionic silver has been chosen to serve as the biocide. As an attempt to understand what processes might reduce the known losses of silver, different treatment processes were attempted and samples of the wetted materials were tested, individually and together, to determine the relative loss of biocide under representative surface area-to-volume ratios. The results of testing presented here showed that the materials could be treated by a nitric acid rinse or a high-concentration silver spike to reduce the loss of silver and bacterial growth. It was also found that the minimum biocidal concentration could be maintained for over 28 days. These results have pointed to approaches that could be used to successfully maintain silver in spacecraft water systems for long-duration missions.

      PubDate: 2017-10-07T22:36:59Z
      DOI: 10.1016/j.actaastro.2017.09.034
      Issue No: Vol. 141 (2017)
  • Parametric study of sensor placement for vision-based relative navigation
           system of multiple spacecraft
    • Authors: Junho Jeong; Seungkeun Kim; Jinyoung Suk
      Pages: 36 - 49
      Abstract: Publication date: December 2017
      Source:Acta Astronautica, Volume 141
      Author(s): Junho Jeong, Seungkeun Kim, Jinyoung Suk
      In order to overcome the limited range of GPS-based techniques, vision-based relative navigation methods have recently emerged as alternative approaches for a high Earth orbit (HEO) or deep space missions. Therefore, various vision-based relative navigation systems use for proximity operations between two spacecraft. For the implementation of these systems, a sensor placement problem can occur on the exterior of spacecraft due to its limited space. To deal with the sensor placement, this paper proposes a novel methodology for a vision-based relative navigation based on multiple position sensitive diode (PSD) sensors and multiple infrared beacon modules. For the proposed method, an iterated parametric study is used based on the farthest point optimization (FPO) and a constrained extended Kalman filter (CEKF). Each algorithm is applied to set the location of the sensors and to estimate relative positions and attitudes according to each combination by the PSDs and beacons. After that, scores for the sensor placement are calculated with respect to parameters: the number of the PSDs, number of the beacons, and accuracy of relative estimates. Then, the best scoring candidate is determined for the sensor placement. Moreover, the results of the iterated estimation show that the accuracy improves dramatically, as the number of the PSDs increases from one to three.

      PubDate: 2017-10-07T22:36:59Z
      DOI: 10.1016/j.actaastro.2017.09.020
      Issue No: Vol. 141 (2017)
  • Design of tipping structure for 110 m high-precision radio telescope
    • Authors: Shufei Feng; Congsi Wang; Baoyan Duan; You Ban
      Pages: 50 - 56
      Abstract: Publication date: December 2017
      Source:Acta Astronautica, Volume 141
      Author(s): Shufei Feng, Congsi Wang, Baoyan Duan, You Ban
      Considering the stringent surface accuracy and pointing accuracy specifications of the 110 m radio telescope, the homologous deformation characteristics of the reflector is first studied, and key design points of the tipping structure are presented further. Then, a novel Reflector-Alidade Connecting Structure (RACS) scheme for large telescope is proposed based on these points. Finally, the new design scheme is applied to the numerical example of 110 m telescope, and the results verify the feasibility and effectiveness of the new scheme.

      PubDate: 2017-10-07T22:36:59Z
      DOI: 10.1016/j.actaastro.2017.09.036
      Issue No: Vol. 141 (2017)
  • Multifunctional fiber reinforced polymer composites using carbon and boron
           nitride nanotubes
    • Authors: Behnam Ashrafi; Michael B. Jakubinek; Yadienka Martinez-Rubi; Meysam Rahmat; Drazen Djokic; Kurtis Laqua; Daesun Park; Keun-Su Kim; Benoit Simard; Ali Yousefpour
      Pages: 57 - 63
      Abstract: Publication date: December 2017
      Source:Acta Astronautica, Volume 141
      Author(s): Behnam Ashrafi, Michael B. Jakubinek, Yadienka Martinez-Rubi, Meysam Rahmat, Drazen Djokic, Kurtis Laqua, Daesun Park, Keun-Su Kim, Benoit Simard, Ali Yousefpour
      Recent progress in nanotechnology has made several nano-based materials available with the potential to address limitations of conventional fiber reinforced polymer composites, particularly in reference to multifunctional structures. Carbon nanotubes (CNTs) are the most prevalent case and offer amazing properties at the individual nanotube level. There are already a few high-profile examples of the use of CNTs in space structures to provide added electrical conductivity for static dissipation and electromagnetic shielding. Boron nitride nanotubes (BNNTs), which are structurally analogous to CNTs, also present a range of attractive properties. Like the more widely explored CNTs, individual BNNTs display remarkable mechanical properties and high thermal conductivity but with contrasting functional attributes including substantially higher thermal stability, high electrical insulation, polarizability, high neutron absorption and transparency to visible light. This presents the potential of employing either or both BNNTs and CNTs to achieve a range of lightweight, functional composites for space structures. Here we present the case for application of BNNTs, in addition to CNTs, in space structures and describe recent advances in BNNT production at the National Research Council Canada (NRC) that have, for the first time, provided sufficiently large quantities to enable commercialization of high-quality BNNTs and accelerate development of chemistry, composites and applications based on BNNTs. Early demonstrations showing the fabrication and limited structural testing of polymer matrix composites, including glass fiber-reinforced composite panels containing BNNTs will be discussed.

      PubDate: 2017-10-07T22:36:59Z
      DOI: 10.1016/j.actaastro.2017.09.023
      Issue No: Vol. 141 (2017)
  • Numerical simulation of a Rotating Detonation with a realistic injector
           designed for separate supply of gaseous hydrogen and oxygen
    • Authors: T. Gaillard; D. Davidenko; F. Dupoirieux
      Pages: 64 - 78
      Abstract: Publication date: December 2017
      Source:Acta Astronautica, Volume 141
      Author(s): T. Gaillard, D. Davidenko, F. Dupoirieux
      This paper presents numerical results for a Rotating Detonation (RD) propagating in a layer of combustible mixture, created by injection of gaseous hydrogen and oxygen. 3D Large Eddy Simulations (LES) of a reacting flow have been performed in a domain of planar geometry in order to eliminate possible effects of the chamber curvature. First, the results for a 2D case with uniformly distributed premixed injection are presented to characterize the RD propagation under the most idealized conditions. Then a 3D concept is introduced for the injector composed of a series of injection elements. The RD propagation is simulated under the conditions of premixed and separate injection of the propellants at globally stoichiometric proportions. The case of separate propellant injection is the most realistic one. The computational results, represented by instantaneous and averaged flowfields, are analyzed to characterize the flowfield and the conditions of RD propagation. This analysis allows identifying the effects due to two major factors: the injection through discrete holes with respect to the distributed one and the separate propellant feeding with respect to the premixed one. Macroscopic quantities, such as the RD propagation speed, mean chamber pressure, average parameters of the mixture, and mixing efficiency are evaluated and compared in order to characterize the studied effects.

      PubDate: 2017-10-07T22:36:59Z
      DOI: 10.1016/j.actaastro.2017.09.011
      Issue No: Vol. 141 (2017)
  • Post-Newtonian equations of motion for LEO debris objects and space-based
           acquisition, pointing and tracking laser systems
    • Authors: J.M. Gambi; M.L. García del Pino; J. Gschwindl; E.B. Weinmüller
      Pages: 132 - 142
      Abstract: Publication date: December 2017
      Source:Acta Astronautica, Volume 141
      Author(s): J.M. Gambi, M.L. García del Pino, J. Gschwindl, E.B. Weinmüller
      This paper deals with the problem of throwing middle-sized low Earth orbit debris objects into the atmosphere via laser ablation. The post-Newtonian equations here provided allow (hypothetical) space-based acquisition, pointing and tracking systems endowed with very narrow laser beams to reach the pointing accuracy presently prescribed. In fact, whatever the orbital elements of these objects may be, these equations will allow the operators to account for the corrections needed to balance the deviations of the line of sight directions due to the curvature of the paths the laser beams are to travel along. To minimize the respective corrections, the systems will have to perform initial positioning manoeuvres, and the shooting point-ahead angles will have to be adapted in real time. The enclosed numerical experiments suggest that neglecting these measures will cause fatal errors, due to differences in the actual locations of the objects comparable to their size.

      PubDate: 2017-10-14T14:47:50Z
      DOI: 10.1016/j.actaastro.2017.10.006
      Issue No: Vol. 141 (2017)
  • Nonlinear electromechanical modelling and dynamical behavior analysis of a
           satellite reaction wheel
    • Authors: Alireza Aghalari; Morteza Shahravi
      Pages: 143 - 157
      Abstract: Publication date: December 2017
      Source:Acta Astronautica, Volume 141
      Author(s): Alireza Aghalari, Morteza Shahravi
      The present research addresses the satellite reaction wheel (RW) nonlinear electromechanical coupling dynamics including dynamic eccentricity of brushless dc (BLDC) motor and gyroscopic effects, as well as dry friction of shaft-bearing joints (relative small slip) and bearing friction. In contrast to other studies, the rotational velocity of the flywheel is considered to be controllable, so it is possible to study the reaction wheel dynamical behavior in acceleration stages. The RW is modeled as a three-phases BLDC motor as well as flywheel with unbalances on a rigid shaft and flexible bearings. Improved Lagrangian dynamics for electromechanical systems is used to obtain the mathematical model of the system. The developed model can properly describe electromechanical nonlinear coupled dynamical behavior of the satellite RW. Numerical simulations show the effectiveness of the presented approach.

      PubDate: 2017-10-14T14:47:50Z
      DOI: 10.1016/j.actaastro.2017.10.010
      Issue No: Vol. 141 (2017)
  • Semi-analytical methods for rapid pre-dimensioning of launcher structures
           subjected to Booster load introduction
    • Authors: Andreas Rittweger
      Pages: 158 - 171
      Abstract: Publication date: December 2017
      Source:Acta Astronautica, Volume 141
      Author(s): Andreas Rittweger
      This paper describes a new analysis method for orthotropic cylindrical shell structures with arbitrary stiffness distribution. The structural model consists of ring frame elements, orthotropic membrane panels and longitudinal stiffeners (stringer). The element stiffness matrix of the orthotropic panel is based on the displacements functions of its boundary only. The boundary value problem is solved by developing the stresses in Taylor series and applying the principal of virtual work (virtual forces). By this way it is possible to have large elements able to describe stress peaks. The method is applied for Booster load introduction into launcher structures and reduces the number of degrees of freedom drastically, allowing rapid analyses necessary for parametric optimization in the pre-design phase.

      PubDate: 2017-10-14T14:47:50Z
      DOI: 10.1016/j.actaastro.2017.09.031
      Issue No: Vol. 141 (2017)
  • Design of a three-dimensional scramjet nozzle considering lateral
           expansion and geometric constraints
    • Authors: Zheng Lv; Jinglei Xu; Jianwei Mo
      Pages: 172 - 182
      Abstract: Publication date: December 2017
      Source:Acta Astronautica, Volume 141
      Author(s): Zheng Lv, Jinglei Xu, Jianwei Mo
      A new method based on quasi two-dimensional supersonic flow and maximum thrust theory to design a three-dimensional nozzle while considering lateral expansion and geometric constraints is presented in this paper. To generate the configuration of the three-dimensional nozzle, the inviscid flowfield is calculated through the method of characteristics, and the reference temperature method is applied to correct the boundary layer thickness. The computational fluid dynamics approach is used to obtain the aerodynamic performance of the nozzle. Results show that the initial arc radius slightly influences the axial thrust coefficient, whereas the variations in the lateral expansion contour, the length and initial expansion angle of the lower cowl significantly affect the axial thrust coefficient. The three-dimensional nozzle designed by streamline tracing technique is also investigated for comparison to verify the superiority of the new method. The proposed nozzle shows increases in the axial thrust coefficient, lift, and pitching moment of 6.86%, 203.15%, and 642.86%, respectively, at the design point, compared with the nozzle designed by streamline tracing approach. In addition, the lateral expansion accounts for 22.46% of the entire axial thrust, while it has no contribution to the lift and pitching moment in the proposed nozzle.

      PubDate: 2017-10-14T14:47:50Z
      DOI: 10.1016/j.actaastro.2017.09.033
      Issue No: Vol. 141 (2017)
  • Building large telescopes in orbit using small satellites
    • Authors: Chris Saunders; Dan Lobb; Martin Sweeting; Yang Gao
      Pages: 183 - 195
      Abstract: Publication date: December 2017
      Source:Acta Astronautica, Volume 141
      Author(s): Chris Saunders, Dan Lobb, Martin Sweeting, Yang Gao
      In many types of space mission there is a constant desire for larger and larger instrument apertures, primarily for the purposes of increased resolution or sensitivity. In the Radio Frequency domain, this is currently addressed by antennas that unfold or deploy on-orbit. However, in the optical and infrared domains, this is a significantly more challenging problem, and has up to now either been addressed by simply having large monolithic mirrors (which are fundamentally limited by the volume and mass lifting capacity of any launch vehicle) or by complex ‘semi-folding’ designs such as the James Webb Space Telescope. An alternative is to consider a fractionated instrument which is launched as a collection of individual smaller elements which are then assembled (or self-assemble) once in space, to form a much larger overall instrument. SSTL has been performing early concept assessment work on such systems for high resolution science observations from high orbits (potentially also for persistent surveillance of Earth). A point design of a 25 m sparse aperture (annular ring) telescope is presented. Key characteristics of 1) multiple small elements launched separately and 2) on-orbit assembly to form a larger instrument are included in the architecture. However, on-orbit assembly brings its own challenges in terms of guidance navigation and control, robotics, docking mechanisms, system control and data handling, optical alignment and stability, and many other elements. The number and type of launchers used, and the technologies and systems used heavily affect the outcome and general cost of the telescope. The paper describes one of the fractionated architecture concepts currently being studied by SSTL, including the key technologies and operational concepts that may be possible in the future.

      PubDate: 2017-10-14T14:47:50Z
      DOI: 10.1016/j.actaastro.2017.09.022
      Issue No: Vol. 141 (2017)
  • Effects of dynamic backpressure on shock train motions in straight
    • Authors: Jian Sun; Jin Zhou; Shijie Liu; Zhiyong Lin; Jianhua Cai
      Pages: 388 - 401
      Abstract: Publication date: Available online 7 October 2017
      Source:Acta Astronautica
      Author(s): Jianhua Cai, Jin Zhou, Shijie Liu, Zhiyong Lin
      A numerical study of an oscillating shock train under different types of sinusoidal backpressure in a straight isolator is conducted. In comparison, the shock train location and structure under steady backpressure are explored at first. The results reveal that the shock train moves upstream in a nonlinear way with the increasing backpressure and it keeps nearly the same structure in the process of moving upstream under a certain range of backpressure. Secondly, the typical characteristic of shock train motions under dynamic backpressure is investigated from many aspects. When subjected to sinusoidal backpressure, the shock train undergoes a consistent and repeatable periodic motion, which is similar to the simple harmonic motion. Moreover, the impacts of frequency, amplitude and the average of dynamic backpressure on shock train motions are discussed systematically in this paper. It is found that the average backpressure has a great influence on the location of shock train oscillating region, which moves upstream as the average backpressure is increased. The amplitude of dynamic backpressure has a noticeable effect on the size of shock train oscillating region, which is positively correlated with the amplitude. The frequency affects both the location and size of shock train oscillating region. As the frequency increases, the oscillating region becomes smaller and closer to the exit of the isolator.

      PubDate: 2017-10-07T22:36:59Z
      DOI: 10.1016/j.actaastro.2017.09.008
      Issue No: Vol. 140 (2017)
  • Combustion characteristics and turbulence modeling of swirling reacting
           flow in solid fuel ramjet
    • Authors: Omer Musa; Chen Xiong; Zhou Changsheng
      Pages: 1 - 17
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): Omer Musa, Chen Xiong, Zhou Changsheng
      This paper reviews the historical studies have been done on the solid-fuel ramjet engine and difficulties associated with numerical modeling of swirling flow with combustible gases. A literature survey about works related to numerical and experimental investigations on solid-fuel ramjet as well as using swirling flow and different numerical approaches has been provided. An overview of turbulence modeling of swirling flow and the behavior of turbulence at streamline curvature and system rotation are presented. A new and simple curvature/correction factor is proposed in order to reduce the programming complexity of SST-CC turbulence model. Finally, numerical and experimental investigations on the impact of swirling flow on SFRJ have been carried out. For that regard, a multi-physics coupling code is developed to solve the problems of multi-physics coupling of fluid mechanics, solid pyrolysis, heat transfer, thermodynamics, and chemical kinetics. The connected-pipe test facility is used to carry out the experiments. The results showed a positive impact of swirling flow on SFRJ along with, three correlations are proposed.

      PubDate: 2017-10-07T22:36:59Z
      DOI: 10.1016/j.actaastro.2017.06.023
      Issue No: Vol. 139 (2017)
  • Torque distribution algorithm for effective use of reaction wheel torques
           and angular momentums
    • Authors: Mikihiro Sugita
      Pages: 18 - 23
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): Mikihiro Sugita
      In attitude control of spacecraft using more than three reaction wheels, the distribution of the attitude control torque to the wheels is not unique because of the redundancy. There are several wheel torque distribution algorithms which optimize the wheel torques or other factors. In particular, the optimal torque distribution algorithm is acknowledged as algorithm which minimizes the maximum wheel torque. This algorithm is advantageous to make maximum use of the wheel torques, because each wheel torque must be lower than the wheel torque capability and torque is the primary driver in many cases. However, as a result of minimizing the maximum wheel torque, the distribution of the wheel angular momentums is not calculated by a similar formula for the wheel torques distribution. In other words, the wheel angular momentums cannot be derived from the current attitude angular momentum. When certain wheel reaches maximum angular momentum earlier than the other wheels, this prohibits maximum use of the other wheels' capability. Therefore, minimizing the maximum wheel torque is not always effective when other constraint such as angular momentum matters. Recently, it has become more important that both wheel torques and angular momentums are used more effectively in order to improve the performance of the spacecraft agility, such as the high angular acceleration and rate, by using minimum spacecraft resources (i.e. minimum number of wheels which satisfies certain agility requirements). In this paper, shown is the wheel torque distribution algorithm which is effective in terms of both the wheel torques and angular momentums as much as possible. In the proposed algorithm, the wheel torques/angular momentums distributed from the current attitude torque/angular momentum can be optimal for particular direction like the spacecraft X/Y/Z axis. In addition, it is shown by numerical simulation that the proposed algorithm improves the usage of attitude control angular momentum by up to 60% compared to the optimal torque distribution algorithm.

      PubDate: 2017-10-07T22:36:59Z
      DOI: 10.1016/j.actaastro.2017.06.014
      Issue No: Vol. 139 (2017)
  • Experimental study of cone-struts and cavity flameholders in a
           kerosene-fueled round scramjet combustor
    • Authors: Dongqing Zhang; Wenyan Song
      Pages: 24 - 33
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): Dongqing Zhang, Wenyan Song
      Experimental investigations of liquid kerosene ignition and flameholding in a round supersonic combustor are presented. Three kinds of flameholders, a cone-struts structure, a cavity and the combination of the both, are studied for the kerosene ignition and flameholding. Results show that ignition and flameholding cannot be achieved by using the sole cone-struts flameholder, although flames are observed at the combustor outlet. The ignition and flameholding are achieved in a narrow range of equivalence ratios by using the cavity flameholder. This range is widened by employing the combination of the cone-struts and the cavity flameholders. It is observed that the back pressure disrupts the isolator entrance flow slightly by using the larger cone-struts (CR = 0.261). However, it does not happen when the smaller cone-struts (CR = 0.221) is employed. Then a characteristic air mass flow rate in the round combustor is redefined to calculate a modified Damkohler number that correlates the nonpremixed flame stability limits. The correlations are in good agreements with the experimental results.

      PubDate: 2017-10-07T22:36:59Z
      DOI: 10.1016/j.actaastro.2017.06.025
      Issue No: Vol. 139 (2017)
  • Analysis of the effect of attachment point bias during large space debris
           removal using a tethered space tug
    • Authors: Zhongyi Chu; Jingnan Di; Jing Cui
      Pages: 34 - 41
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): Zhongyi Chu, Jingnan Di, Jing Cui
      Space debris occupies a valuable orbital resource and is an inevitable and urgent problem, especially for large space debris because of its high risk and the possible crippling effects of a collision. Space debris has attracted much attention in recent years. A tethered system used in an active debris removal scenario is a promising method to de-orbit large debris in a safe manner. In a tethered system, the flexibility of the tether used in debris removal can possibly induce tangling, which is dangerous and should be avoided. In particular, attachment point bias due to capture error can significantly affect the motion of debris relative to the tether and increase the tangling risk. Hence, in this paper, the effect of attachment point bias on the tethered system is studied based on a dynamic model established based on a Newtonian approach. Next, a safety metric of avoiding a tangle when a tether is tensioned with attachment point bias is designed to analyse the tangling risk of the tethered system. Finally, several numerical cases are established and simulated to validate the effects of attachment point bias on a space tethered system.

      PubDate: 2017-10-07T22:36:59Z
      DOI: 10.1016/j.actaastro.2017.06.028
      Issue No: Vol. 139 (2017)
  • A modified modal method for solving the mission-oriented inverse
           kinematics of hyper-redundant space manipulators for on-orbit servicing
    • Authors: Wenfu Xu; Zonggao Mu; Tianliang Liu; Bin Liang
      Pages: 54 - 66
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): Wenfu Xu, Zonggao Mu, Tianliang Liu, Bin Liang
      A hyper-redundant space manipulator has extreme flexibility and is suitable to work in highly cluttered or multi-obstacles environment. However, its inverse kinematics is very challenging due to a large number of degrees of freedom (DOFs). In this paper, a modified modal method is proposed to solve the mission-oriented inverse kinematics. The spatial backbone of the manipulator is defined using a mode function, according to the mission requirement and working environment. All the universal joints are divided into M/2 groups, i.e. two adjacent universal joints comprise a group (M is the number of universal joints; it is assumed an even number. If it is an odd number, the remaining universal joint is a separated group). The whole manipulator is then segmented into M/2 sub-manipulators. Each sub-manipulator has 4-DOFs and is redundant for position or orientation. The last sub-manipulator is used to match the desired direction vector and the position of the end-effector with respect to the previous sub-manipulator's end. The remaining sub-manipulators are used to control the relative position between each other with one redundant degree of freedom. The equivalent link is fitted to the backbone function. The Cartesian coordinates of each node is then determined by combining the total length of the manipulator and the mode function. Then, the joint angles are solved through the position of each node. For each 4-DOF group, a parameter called arm angle is used to denote the redundancy and optimize its local configuration. Finally, typical cases of a 12-DOF and a 20-DOF manipulators are simulated. The results show that the method is very efficient for resolving the inverse kinematics of hyper-redundant space manipulators.

      PubDate: 2017-10-07T22:36:59Z
      DOI: 10.1016/j.actaastro.2017.06.015
      Issue No: Vol. 139 (2017)
  • Effects of injection pressure variation on mixing in a cold supersonic
           combustor with kerosene fuel
    • Authors: Wei-Lai Liu; Lin Zhu; Yin-Yin Qi; Jia-Ru Ge; Feng Luo; Hao-Ran Zou; Min Wei; Tien-Chien Jen
      Pages: 67 - 76
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): Wei-Lai Liu, Lin Zhu, Yin-Yin Qi, Jia-Ru Ge, Feng Luo, Hao-Ran Zou, Min Wei, Tien-Chien Jen
      Spray jet in cold kerosene-fueled supersonic flow has been characterized under different injection pressures to assess the effects of the pressure variation on the mixing between incident shock wave and transverse cavity injection. Based on the real scramjet combustor, a detailed computational fluid dynamics model is developed. The injection pressures are specified as 0.5, 1.0, 2.0, 3.0 and 4.0 MPa, respectively, with the other constant operation parameters (such as the injection diameter, angle and velocity). A three dimensional Couple Level Set & Volume of Fluids approach incorporating an improved Kelvin-Helmholtz & Rayleigh-Taylor model is used to investigate the interaction between kerosene and supersonic air. The numerical simulations primarily concentrate on penetration depth, span expansion area, angle of shock wave and sauter mean diameter distribution of the kerosene droplets with/without evaporation. Validation has been implemented by comparing the calculated against the measured in literature with good qualitative agreement. Results show that the penetration depth, span-wise angle and expansion area of the transverse cavity jet are all increased with the injection pressure. However, when the injection pressure is further increased, the value in either penetration depth or expansion area increases appreciably. This study demonstrates the feasibility and effectiveness of the combination of Couple Level Set & Volume of Fluids approach and an improved Kelvin-Helmholtz & Rayleigh-Taylor model, in turn providing insights into scramjet design improvement.

      PubDate: 2017-10-07T22:36:59Z
      DOI: 10.1016/j.actaastro.2017.06.031
      Issue No: Vol. 139 (2017)
  • Fast spacecraft adaptive attitude tracking control through immersion and
           invariance design
    • Authors: Haowei Wen; Xiaokui Yue; Peng Li; Jianping Yuan
      Pages: 77 - 84
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): Haowei Wen, Xiaokui Yue, Peng Li, Jianping Yuan
      This paper presents a novel non-certainty-equivalence adaptive control method for the attitude tracking control problem of spacecraft with inertia uncertainties. The proposed immersion and invariance (I&I) based adaptation law provides a more direct and flexible approach to circumvent the limitations of the basic I&I method without employing any filter signal. By virtue of the adaptation high-gain equivalence property derived from the proposed adaptive method, the closed-loop adaptive system with a low adaptation gain could recover the high adaptation gain performance of the filter-based I&I method, and the resulting control torque demands during the initial transient has been significantly reduced. A special feature of this method is that the convergence of the parameter estimation error has been observably improved by utilizing an adaptation gain matrix instead of a single adaptation gain value. Numerical simulations are presented to highlight the various benefits of the proposed method compared with the certainty-equivalence-based control method and filter-based I&I control schemes.

      PubDate: 2017-10-07T22:36:59Z
      DOI: 10.1016/j.actaastro.2017.06.024
      Issue No: Vol. 139 (2017)
  • Numerical simulation on the powder propellant pickup characteristics of
           feeding system at high pressure
    • Authors: Haijun Sun; Chunbo Hu; Xiaofei Zhu
      Pages: 85 - 97
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): Haijun Sun, Chunbo Hu, Xiaofei Zhu
      A numerical study of powder propellant pickup progress at high pressure was presented in this paper by using two-fluid model with kinetic theory of granular flow in the computational fluid dynamics software package ANSYS/Fluent. Simulations were conducted to evaluate the effects of initial pressure, initial powder packing rate and mean particle diameter on the flow characteristics in terms of velocity vector distribution, granular temperature, pressure drop, particle velocity and volume. The numerical results of pressure drop were also compared with experiments to verify the TFM model. The simulated results show that the pressure drop value increases as the initial pressure increases, and the granular temperature under the conditions of different initial pressures and packing rates is almost the same in the area of throttling orifice plate. While there is an appropriate value for particle size and packing rate to form a “core-annulus” structure in powder box, and the time-averaged velocity vector distribution of solid phase is inordinate.

      PubDate: 2017-10-07T22:36:59Z
      DOI: 10.1016/j.actaastro.2017.06.030
      Issue No: Vol. 139 (2017)
  • Breakthrough Listen – A new search for life in the universe
    • Authors: S. Pete Worden; Jamie Drew; Andrew Siemion; Dan Werthimer; David DeBoer; Steve Croft; David MacMahon; Matt Lebofsky; Howard Isaacson; Jack Hickish; Danny Price; Vishal Gajjar; Jason T. Wright
      Pages: 98 - 101
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): S. Pete Worden, Jamie Drew, Andrew Siemion, Dan Werthimer, David DeBoer, Steve Croft, David MacMahon, Matt Lebofsky, Howard Isaacson, Jack Hickish, Danny Price, Vishal Gajjar, Jason T. Wright

      PubDate: 2017-10-07T22:36:59Z
      DOI: 10.1016/j.actaastro.2017.06.008
      Issue No: Vol. 139 (2017)
  • Cultural ethology as a new approach of interplanetary crew's behavior
    • Authors: Carole Tafforin; Francisco Giner Abati
      Pages: 102 - 110
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): Carole Tafforin, Francisco Giner Abati
      From an evolutionary perspective, during short-term and medium-term orbital flights, human beings developed new spatial and motor behaviors to compensate for the lack of terrestrial gravity. Past space ethological studies have shown adaptive strategies to the tri-dimensional environment, with the goal of optimizing relationships between the astronaut and unusual sensorial-motor conditions. During a long-term interplanetary journey, crewmembers will have to develop new individual and social behaviors to adapt, far from earth, to isolation and confinement and as a result to extreme conditions of living and working together. Recent space psychological studies pointed out that heterogeneity is a feature of interplanetary crews, based on personality, gender mixing, internationality and diversity of backgrounds. Intercultural issues could arise between space voyagers. As a new approach we propose to emphasize the behavioral strategies of human groups' adaptation to this new multicultural dimension of the environment. Methodology Potential outcomes of applying ethological methods to the study of culture-specific human behaviors are investigated. Ethological and anthropological tools are used, based on observations and descriptions of individuals acting in a micro-society with their rules for living, their work habits and their specific customs and values. We focus the present study on interpersonal communications and organizations in diverse space simulation experiments and analogous environments (Mars-500 experiment, Mars Desert Research Station - MDRS, Tara-Arctic expedition and Concordia South pole station). Results During the Mars-500 experiment, the crewmembers (RU, EU, CH) were differently involved in the activities of daily living. At MDRS in the Desert of Utah, the crewmembers (FR, US, AU, DK) communicated differently in verbal discussions. During the Tara drift in the pack ice, the crewmembers (FR, MC, EE, NZ, NO) were differently positioned in the collective space. At Concordia station, the crewmembers (IT, FR) were grouped preferentially according to their living habits. The results show that cultural heterogeneity has different effects on interpersonal communications and organizations. When considering the isolated and confined crews like an evolving micro-society in unexplored environments, our preliminary analysis raises new questions as to the phylogenetic and epigenetic bases to which cultural ethology linked to anthropology may help to answer. Conclusion Cultural values, in addition to social values and personal values, have to be taken into consideration for future space exploration.

      PubDate: 2017-10-07T22:36:59Z
      DOI: 10.1016/j.actaastro.2017.06.017
      Issue No: Vol. 139 (2017)
  • Sliding mode disturbance observer-enhanced adaptive control for the
           air-breathing hypersonic flight vehicle
    • Authors: Hao An; Changhong Wang; Baris Fidan
      Pages: 111 - 121
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): Hao An, Changhong Wang, Baris Fidan
      This paper presents a backstepping procedure to design an adaptive controller for the air-breathing hypersonic flight vehicle (AHFV) subject to external disturbances and actuator saturations. In each step, a sliding mode exact disturbance observer (SMEDO) is exploited to exactly estimate the lumped disturbance in finite time. Specific dynamics are introduced to handle the possible actuator saturations. Based on SMEDO and introduced dynamics, an adaptive control law is designed, along with the consideration on “explosion of complexity” in backstepping design. The developed controller is equipped with fast disturbance rejection and great capability to accommodate the saturated actuators, which also lead to a wider application scope. A simulation study is provided to show the effectiveness and superiority of the proposed controller.

      PubDate: 2017-10-07T22:36:59Z
      DOI: 10.1016/j.actaastro.2017.06.026
      Issue No: Vol. 139 (2017)
  • Asymptotic stability of a satellite with electrodynamic attitude control
           in the orbital frame
    • Authors: A. Yu. Aleksandrov; A.A. Tikhonov
      Pages: 122 - 129
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): A. Yu. Aleksandrov, A.A. Tikhonov
      A satellite in a circular near-Earth orbit is under consideration. The three-axis stabilization of the satellite in the orbital coordinate system with the use of electrodynamic attitude control system is studied. No constraints are imposed on the Earth's magnetic field approximation. The gravity gradient disturbing torque acting on the satellite attitude dynamics is taken into account as the largest disturbing torque. With the use of the Lyapunov direct method, conditions under which electrodynamic control solves the problem are obtained. The restrictions on the control parameter values for which one can guarantee the asymptotic stability of the programmed satellite motion are found and represented in an explicit form. Comparison of the results of numerical simulation and analytical investigation demonstrate effectiveness of the proposed approach.

      PubDate: 2017-10-07T22:36:59Z
      DOI: 10.1016/j.actaastro.2017.06.033
      Issue No: Vol. 139 (2017)
  • Satellite single-axis attitude determination based on Automatic Dependent
           Surveillance - Broadcast signals
    • Authors: Kaixing Zhou; Xiucong Sun; Hai Huang; Xinsheng Wang; Guangwei Ren
      Pages: 130 - 140
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): Kaixing Zhou, Xiucong Sun, Hai Huang, Xinsheng Wang, Guangwei Ren
      The space-based Automatic Dependent Surveillance - Broadcast (ADS-B) is a new technology for air traffic management. The satellite equipped with spaceborne ADS-B system receives the broadcast signals from aircraft and transfers the message to ground stations, so as to extend the coverage area of terrestrial-based ADS-B. In this work, a novel satellite single-axis attitude determination solution based on the ADS-B receiving system is proposed. This solution utilizes the signal-to-noise ratio (SNR) measurement of the broadcast signals from aircraft to determine the boresight orientation of the ADS-B receiving antenna fixed on the satellite. The basic principle of this solution is described. The feasibility study of this new attitude determination solution is implemented, including the link budget and the access analysis. On this basis, the nonlinear least squares estimation based on the Levenberg-Marquardt method is applied to estimate the single-axis orientation. A full digital simulation has been carried out to verify the effectiveness and performance of this solution. Finally, the corresponding results are processed and presented minutely.

      PubDate: 2017-10-07T22:36:59Z
      DOI: 10.1016/j.actaastro.2017.05.038
      Issue No: Vol. 139 (2017)
  • Power matching between plasma generation and electrostatic acceleration in
           helicon electrostatic thruster
    • Authors: D. Ichihara; Y. Nakagawa; A. Uchigashima; A. Iwakawa; A. Sasoh; T. Yamazaki
      Pages: 157 - 164
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): D. Ichihara, Y. Nakagawa, A. Uchigashima, A. Iwakawa, A. Sasoh, T. Yamazaki
      The effects of a radio-frequency (RF) power on the ion generation and electrostatic acceleration in a helicon electrostatic thruster were investigated with a constant discharge voltage of 300 V using argon as the working gas at a flow rate either of 0.5 Aeq (Ampere equivalent) or 1.0 Aeq. A RF power that was even smaller than a direct-current (DC) discharge power enhanced the ionization of the working gas, thereby both the ion beam current and energy were increased. However, an excessively high RF power input resulted in their saturation, leading to an unfavorable increase in an ionization cost with doubly charged ion production being accompanied. From the tradeoff between the ion production by the RF power and the electrostatic acceleration made by the direct current discharge power, the thrust efficiency has a maximum value at an optimal RF to DC discharge power ratio of 0.6 – 1.0.

      PubDate: 2017-10-07T22:36:59Z
      DOI: 10.1016/j.actaastro.2017.06.032
      Issue No: Vol. 139 (2017)
  • Pose estimation and tracking of non-cooperative rocket bodies using
           Time-of-Flight cameras
    • Authors: Harvey Gómez Martínez; Gabriele Giorgi; Bernd Eissfeller
      Pages: 165 - 175
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): Harvey Gómez Martínez, Gabriele Giorgi, Bernd Eissfeller
      This paper presents a methodology for estimating the position and orientation of a rocket body in orbit – the target – undergoing a roto-translational motion, with respect to a chaser spacecraft, whose task is to match the target dynamics for a safe rendezvous. During the rendezvous maneuver the chaser employs a Time-of-Flight camera that acquires a point cloud of 3D coordinates mapping the sensed target surface. Once the system identifies the target, it initializes the chaser-to-target relative position and orientation. After initialization, a tracking procedure enables the system to sense the evolution of the target's pose between frames. The proposed algorithm is evaluated using simulated point clouds, generated with a CAD model of the Cosmos-3M upper stage and the PMD CamCube 3.0 camera specifications.

      PubDate: 2017-10-07T22:36:59Z
      DOI: 10.1016/j.actaastro.2017.07.002
      Issue No: Vol. 139 (2017)
  • Agent-based algorithm for fault detection and recovery of gyroscope's
           drift in small satellite missions
    • Authors: Johan Carvajal-Godinez; Jian Guo; Eberhard Gill
      Pages: 181 - 188
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): Johan Carvajal-Godinez, Jian Guo, Eberhard Gill
      Failure detection, isolation, and recovery is an essential requirement of any space mission design. Several spacecraft components, especially sensors, are prone to performance deviation due to intrinsic physical effects. For that reason, innovative approaches for the treatment of faults in onboard sensors are necessary. This work introduces the concept of agent-based fault detection and recovery for sensors used in satellite attitude determination and control. Its focuses on the implementation of an algorithm for addressing linear drift bias in gyroscopes. The algorithm was implemented using an agent-based architecture that can be integrated into the satellite's onboard software. Numerical simulations were carried out to show the effectiveness of this scheme in satellite's operations. The proposed algorithm showed a reduction of up to 50% in the stabilization time for the detumbling maneuver, and also an improvement in the pointing accuracy of up to 20% when it was applied in precise payload pointing procedures. The relevance of this contribution is its added value for optimizing the launch and early operation of small satellite missions, as well as, an enabler for innovative satellite functions, for instance, optical downlink communication.

      PubDate: 2017-10-07T22:36:59Z
      DOI: 10.1016/j.actaastro.2017.07.001
      Issue No: Vol. 139 (2017)
  • Structural testing and analysis of a braided, inflatable fabric torus
    • Authors: Andrew C. Young; William G. Davids; Daniel J. Whitney; Joshua D. Clapp; Andrew J. Goupee
      Pages: 189 - 200
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): Andrew C. Young, William G. Davids, Daniel J. Whitney, Joshua D. Clapp, Andrew J. Goupee
      Inflatable structural members have military, disaster relief, aerospace and other important applications as they possess low mass, can be stored in a relatively small volume and have significant load-carrying capacity once pressurized. Of particular interest to the present research is the Hypersonic Inflatable Aerodynamic Decelerator (HIAD) structure under development by NASA. In order to make predictions about the structural response of the HIAD system, it is necessary to understand the response of individual inflatable tori composing the HIAD structure. These inflatable members present unique challenges to structural testing and modeling due to their internal inflation pressure and relative compliance. Structural testing was performed on a braided, inflatable, toroidal structural member with axial reinforcing cords. The internal inflation pressure, magnitude of enforced displacement and loading methodology were varied. In-plane and out-of-plane experimental results were compared to model predictions using a three dimensional, corotational, flexibility-based fiber-beam finite element model including geometric and material nonlinearities, as well as the effects of inflation pressure. It was found that in order to approximate the load-deformation response observed in experimentation it is necessary to carefully control the test and model boundary conditions and loading scheme.

      PubDate: 2017-10-07T22:36:59Z
      DOI: 10.1016/j.actaastro.2017.07.004
      Issue No: Vol. 139 (2017)
  • Drift-free solar sail formations in elliptical Sun-synchronous orbits
    • Authors: Khashayar Parsay; Hanspeter Schaub
      Pages: 201 - 212
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): Khashayar Parsay, Hanspeter Schaub
      To study the spatial and temporal variations of plasma in the highly dynamic environment of the magnetosphere, multiple spacecraft must fly in a formation. The objective for this study is to investigate the feasibility of solar sail formation flying in the Earth-centered, Sun-synchronous orbit regime. The focus of this effort is to enable formation flying for a group of solar sails that maintain a nominally fixed Sun-pointing attitude during formation flight, solely for the purpose of precessing their orbit apse lines Sun-synchronously. A fixed-attitude solar sail formation is motivated by the difficulties in the simultaneous control of orbit and attitude in flying solar sails. First, the secular rates of the orbital elements resulting from the effects of solar radiation pressure (SRP) are determined using averaging theory for a Sun-pointing attitude sail. These averaged rates are used to analytically derive the first-order necessary conditions for a drift-free solar sail formation in Sun-synchronous orbits, assuming a fixed Sun-pointing orientation for each sail in formation. The validity of the first-order necessary conditions are illustrated by designing quasi-periodic relative motions. Next, nonlinear programming is applied to design truly drift-free two-craft solar sail formations. Lastly, analytic expressions are derived to determine the long-term dynamics and sensitivity of the formation with respect to constant attitude errors, uncertainty in orbital elements, and uncertainty in a sail's characteristic acceleration.

      PubDate: 2017-10-07T22:36:59Z
      DOI: 10.1016/j.actaastro.2017.06.027
      Issue No: Vol. 139 (2017)
  • Non-cooperative spacecraft pose tracking based on point cloud feature
    • Authors: Ying He; Bin Liang; Jin He; Shunzhi Li
      Pages: 213 - 221
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): Ying He, Bin Liang, Jin He, Shunzhi Li
      On-orbit services have been paid more and more attention for its role in spacecraft life-extension, capacity improvement and on-orbit debris removal. As most of on-orbit targets are non-cooperative, relatively accurate pose measurement is very essential for subsequent operations. However, with the rapid development of TriDAR, flash LIDAR and other laser scanning equipment in non-cooperative target measurement, it becomes more imperative to research methods for non-cooperative target pose tracking based on 3D point cloud feature. In this paper, a method for non-cooperative target pose tracking based on point cloud feature is proposed. Firstly, the target is identified using curvature, normal, density and other geometric features of the point cloud. Then the particle filter algorithm is used to recognize the position and orientation of the target being tracked by calculating the similarity of the point cloud features of two adjacent frames. Experimental results showed that the proposed method could effectively identify the features of non-cooperative targets and track their position and attitude.

      PubDate: 2017-10-07T22:36:59Z
      DOI: 10.1016/j.actaastro.2017.06.021
      Issue No: Vol. 139 (2017)
  • The politics of space mining – An account of a simulation game
    • Authors: Deganit Paikowsky; Roey Tzezana
      Abstract: Publication date: Available online 14 October 2017
      Source:Acta Astronautica
      Author(s): Deganit Paikowsky, Roey Tzezana
      Celestial bodies like the Moon and asteroids contain materials and precious metals, which are valuable for human activity on Earth and beyond. Space mining has been mainly relegated to the realm of science fiction, and was not treated seriously by the international community. The private industry is starting to assemble towards space mining, and success on this front would have major impact on all nations. We present in this paper a review of current space mining ventures, and the international legislation, which could stand in their way - or aid them in their mission. Following that, we present the results of a role-playing simulation in which the role of several important nations was played by students of international relations. The results of the simulation are used as a basis for forecasting the potential initial responses of the nations of the world to a successful space mining operation in the future.

      PubDate: 2017-10-14T14:47:50Z
      DOI: 10.1016/j.actaastro.2017.10.016
  • Thermal probe design for Europa sample acquisition
    • Authors: Mera Horne
      Abstract: Publication date: Available online 13 October 2017
      Source:Acta Astronautica
      Author(s): Mera Horne
      The planned lander missions to the surface of Europa will access samples from the subsurface of the ice in a search for signs of life. A small thermal drill (probe) is proposed to meet the sample requirement of the Science Definition Team's (SDT) report for the Europa mission. The probe is 2 cm in diameter and 16 cm in length and is designed to access the subsurface to 10 cm deep and to collect five ice samples of 7 cm3 each, approximately. The energy required to penetrate the top 10 cm of ice in a vacuum is 26 Wh, approximately, and to melt 7 cm3 of ice is 1.2 Wh, approximately. The requirement stated in the SDT report of collecting samples from five different sites can be accommodated with repeated use of the same thermal drill. For smaller sample sizes, a smaller probe of 1.0 cm in diameter with the same length of 16 cm could be utilized that would require approximately 6.4 Wh to penetrate the top 10 cm of ice, and 0.02 Wh to collect 0.1 g of sample. The thermal drill has the advantage of simplicity of design and operations and the ability to penetrate ice over a range of densities and hardness while maintaining sample integrity.

      PubDate: 2017-10-14T14:47:50Z
      DOI: 10.1016/j.actaastro.2017.10.015
  • Combined high and low-thrust geostationary orbit insertion with radiation
    • Authors: Malcolm Macdonald; Steven Robert Owens
      Abstract: Publication date: Available online 12 October 2017
      Source:Acta Astronautica
      Author(s): Malcolm Macdonald, Steven Robert Owens
      The sequential use of an electric propulsion system is considered in combination with a high-thrust propulsion system for application to the propellant-optimal Geostationary Orbit insertion problem, whilst considering both temporal and radiation flux constraints. Such usage is found to offer a combined propellant mass saving when compared with an equivalent high-thrust only transfer. This propellant mass saving is seen to increase as the allowable transfer duration is increased, and as the thrust from the low-thrust system is increased, assuming constant specific impulse. It was found that the required plane change maneuver is most propellant-efficiently performed by the high-thrust system. The propellant optimal trajectory incurs a significantly increased electron flux when compared to an equivalent high-thrust only transfer. However, the electron flux can be reduced to a similar order of magnitude by increasing the high-thrust propellant consumption, whilst still delivering an improved mass fraction.

      PubDate: 2017-10-14T14:47:50Z
      DOI: 10.1016/j.actaastro.2017.10.011
  • Limits and signatures of relativistic spaceflight
    • Authors: Ulvi Yurtsever; Steven Wilkinson
      Abstract: Publication date: Available online 10 October 2017
      Source:Acta Astronautica
      Author(s): Ulvi Yurtsever, Steven Wilkinson
      While special relativity imposes an absolute speed limit at the speed of light, our Universe is not empty Minkowski spacetime. The constituents that fill the interstellar/intergalactic vacuum, including the cosmic microwave background photons, impose a lower speed limit on any object travelling at relativistic velocities. Scattering of cosmic microwave phtotons from an ultra-relativistic object may create radiation with a characteristic signature allowing the detection of such objects at large distances.

      PubDate: 2017-10-14T14:47:50Z
      DOI: 10.1016/j.actaastro.2017.10.014
  • Electrodynamical compensation of disturbing torque and attitude
           stabilization of a satellite in J2 perturbed orbit
    • Authors: A.A. Tikhonov; K.A. Antipov D.G. Korytnikov D.Yu. Nikitin
      Abstract: Publication date: Available online 7 October 2017
      Source:Acta Astronautica
      Author(s): A.A. Tikhonov, K.A. Antipov, D.G. Korytnikov, D.Yu. Nikitin
      The paper deals with a satellite in a circular near-Earth orbit, perturbed due to J 2 Earth's oblateness. The satellite interacts with the geomagnetic field by the moments of Lorentz and magnetic forces. The octupole approximation of the Earth's magnetic field is used. The possibility of electrodynamical attitude control for the satellite's stabilization in the orbital frame is analyzed. Once the problem of electrodynamical compensation of disturbing torque is solved, we can obtain the control algorithms for the satellite electromagnetic parameters which allows to stabilize the satellite attitude position in the orbital frame in the presence of disturbing gravity gradient torque. The total stability of the satellite programmed motion is proved analytically and verified by computer modeling.

      PubDate: 2017-10-07T22:36:59Z
  • A review of the performance and structural considerations of paraffin wax
           hybrid rocket fuels with additives
    • Authors: Kirsty Veale; Sarp Adali Jean Pitot Michael Brooks
      Abstract: Publication date: Available online 7 October 2017
      Source:Acta Astronautica
      Author(s): Kirsty Veale, Sarp Adali, Jean Pitot, Michael Brooks
      Paraffin wax as a hybrid rocket fuel has not been comprehensively characterised, especially regarding the structural feasibility of the material in launch applications. Preliminary structural testing has shown paraffin wax to be a brittle, low strength material, and at risk of failure under launch loading conditions. Structural enhancing additives have been identified, but their effect on motor performance has not always been considered, nor has any standard method of testing been identified between research institutes. A review of existing regression rate measurement techniques on paraffin wax based fuels and the results obtained with various additives are collated and discussed in this paper. The review includes 2D slab motors that enable visualisation of liquefying fuel droplet entrainment and the effect of an increased viscosity on the droplet entrainment mechanism, which can occur with the addition of structural enhancing polymers. An increased viscosity has been shown to reduce the regression rate of liquefying fuels. Viscosity increasing additives that have been tested include EVA and LDPE. Both these additives increase the structural properties of paraffin wax, where the elongation and UTS are improved. Other additives, such as metal hydrides, aluminium and boron generally offer improvements on the regression rate. However, very little consideration has been given to the structural effects these additives have on the wax grain. A 40% aluminised grain, for example, offers a slight increase in the UTS but reduces the elongation of paraffin wax. Geometrically accurate lab-scale motors have also been used to determine the regression rate properties of various additives in paraffin wax. A concise review of all available regression rate testing techniques and results on paraffin wax based hybrid propellants, as well as existing structural testing data, is presented in this paper.

      PubDate: 2017-10-07T22:36:59Z
  • Calcium dependent current recordings in Xenopus laevis oocytes in
    • Authors: Simon L. Wuest; Christian Roesch; Fabian Ille; Marcel Egli
      Abstract: Publication date: Available online 3 October 2017
      Source:Acta Astronautica
      Author(s): Simon L. Wuest, Christian Roesch, Fabian Ille, Marcel Egli
      Mechanical unloading by microgravity (or weightlessness) conditions triggers profound adaptation processes at the cellular and organ levels. Among other mechanisms, mechanosensitive ion channels are thought to play a key role in allowing cells to transduce mechanical forces. Previous experiments performed under microgravity have shown that gravity affects the gating properties of ion channels. Here, a method is described to record a calcium-dependent current in native Xenopus laevis oocytes under microgravity conditions during a parabolic flight. A 3-voltage-step protocol was applied to provoke a calcium-dependent current. This current increased with extracellular calcium concentration and could be reduced by applying extracellular gadolinium. The custom-made “OoClamp” hardware was validated by comparing the results of the 3-voltage-step protocol to results obtained with a well-established two-electrode voltage clamp (TEVC). In the context of the 2nd Swiss Parabolic Flight Campaign, we tested the OoClamp and the method. The setup and experiment protocol worked well in parabolic flight. A tendency that the calcium-dependent current was smaller under microgravity than under 1 g condition could be observed. However, a conclusive statement was not possible due to the small size of the data base that could be gathered.

      PubDate: 2017-10-07T22:36:59Z
      DOI: 10.1016/j.actaastro.2017.10.003
  • Thermal shock induced dynamics of a spacecraft with a flexible deploying
    • Authors: Zhenxing Shen; Huijian Li; Xiaoning Liu; Gengkai Hu
      Abstract: Publication date: Available online 3 October 2017
      Source:Acta Astronautica
      Author(s): Zhenxing Shen, Huijian Li, Xiaoning Liu, Gengkai Hu
      The dynamics in the process of deployment of a flexible extendible boom as a deployable structure on the spacecraft is studied. For determining the thermally induced vibrations of the boom subjected to an incident solar heat flux, an axially moving thermal-dynamic beam element based on the absolute nodal coordinate formulation which is able to precisely describe the large displacement, rotation and deformation of flexible body is presented. For the elastic forces formulation of variable-length beam element, the enhanced continuum mechanics approach is adopted, which can eliminate the Poisson locking effect, and take into account the tension-bending-torsion coupling deformations. The main body of the spacecraft, modeled as a rigid body, is described using the natural coordinates method. In the derived nonlinear thermal-dynamic equations of rigid-flexible multibody system, the mass matrix is time-variant, and a pseudo damping matrix which is without actual energy dissipation, and a heat conduction matrix which is relative to the moving speed and the number of beam element are arisen. Numerical results give the dynamic and thermal responses of the nonrotating and spinning spacecraft, respectively, and show that thermal shock has a significant influence on the dynamics of spacecraft.

      PubDate: 2017-10-07T22:36:59Z
      DOI: 10.1016/j.actaastro.2017.10.004
  • Publication Information
    • Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139

      PubDate: 2017-10-07T22:36:59Z
  • Mach-Effect thruster model
    • Authors: Tajmar
      Abstract: Publication date: December 2017
      Source:Acta Astronautica, Volume 141
      Author(s): M. Tajmar
      The Mach-Effect thruster is a propellantless propulsion concept that has been in development by J.F. Woodward for more than two decades. It consists of a piezo stack that produces mass fluctuations, which in turn can lead to net time-averaged thrusts. So far, thrust predictions had to use an efficiency factor to explain some two orders of magnitude discrepancy between model and observations. Here, a detailed 1D analytical model is presented that takes piezo material parameters and geometry dimensions into account leading to correct thrust predictions in line with experimental measurements. Scaling laws can now be derived to improve thrust range and efficiency. An important difference in this study is that only the mechanical power developed by the piezo stack is considered to be responsible for the mass fluctuations, whereas prior works focused on the electrical energy into the system. This may explain why some previous designs did not work as expected. The good match between this new mathematical formulation and experiments should boost confidence in the Mach effect thruster concept to stimulate further developments.

      PubDate: 2017-09-30T07:51:11Z
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