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Showing 1 - 200 of 3049 Journals sorted alphabetically
A Practical Logic of Cognitive Systems     Full-text available via subscription   (Followers: 7)
AASRI Procedia     Open Access   (Followers: 15)
Academic Pediatrics     Hybrid Journal   (Followers: 25, SJR: 1.402, h-index: 51)
Academic Radiology     Hybrid Journal   (Followers: 22, SJR: 1.008, h-index: 75)
Accident Analysis & Prevention     Partially Free   (Followers: 86, 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: 364, 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: 229, 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: 1)
Acta Poética     Open Access   (Followers: 4)
Acta Psychologica     Hybrid Journal   (Followers: 24, 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: 6)
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: 133, 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: 26, 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 Cell Aging and Gerontology     Full-text available via subscription   (Followers: 4)
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: 27, 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: 7)
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: 45, SJR: 3.25, h-index: 43)
Advances in Engineering Software     Hybrid Journal   (Followers: 26, 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: 43, SJR: 5.465, h-index: 64)
Advances in Exploration Geophysics     Full-text available via subscription   (Followers: 3)
Advances in Fluorine Science     Full-text available via subscription   (Followers: 8)
Advances in Food and Nutrition Research     Full-text available via subscription   (Followers: 51, 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: 12)
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 Human Factors/Ergonomics     Full-text available via subscription   (Followers: 26)
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: 36, 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 Intl. Accounting     Full-text available via subscription   (Followers: 4)
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: 16, 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: 8, 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 Organ Biology     Full-text available via subscription   (Followers: 2)
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: 62)
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: 2, SJR: 0.1, h-index: 2)
Advances in Space Biology and Medicine     Full-text available via subscription   (Followers: 5)
Advances in Space Research     Full-text available via subscription   (Followers: 360, 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: 16)
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: 44, 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: 333, 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: 416, SJR: 1.385, h-index: 72)
Agri Gene     Hybrid Journal  
Agricultural and Forest Meteorology     Hybrid Journal   (Followers: 16, SJR: 2.18, h-index: 116)
Agricultural Systems     Hybrid Journal   (Followers: 30, SJR: 1.275, h-index: 74)
Agricultural Water Management     Hybrid Journal   (Followers: 40, 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: 55, 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: 11, 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   (Followers: 1)
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: 9, SJR: 0.158, h-index: 9)
Alzheimer's & Dementia     Hybrid Journal   (Followers: 46, SJR: 4.289, h-index: 64)
Alzheimer's & Dementia: Diagnosis, Assessment & Disease Monitoring     Open Access   (Followers: 4)
Alzheimer's & Dementia: Translational Research & Clinical Interventions     Open Access   (Followers: 4)
Ambulatory Pediatrics     Hybrid Journal   (Followers: 5)
American Heart J.     Hybrid Journal   (Followers: 49, SJR: 3.157, h-index: 153)
American J. of Cardiology     Hybrid Journal   (Followers: 48, SJR: 2.063, h-index: 186)
American J. of Emergency Medicine     Hybrid Journal   (Followers: 40, SJR: 0.574, h-index: 65)
American J. of Geriatric Pharmacotherapy     Full-text available via subscription   (Followers: 9, SJR: 1.091, h-index: 45)
American J. of Geriatric Psychiatry     Hybrid Journal   (Followers: 14, SJR: 1.653, h-index: 93)
American J. of Human Genetics     Hybrid Journal   (Followers: 32, SJR: 8.769, h-index: 256)
American J. of Infection Control     Hybrid Journal   (Followers: 26, 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: 46, 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: 198, SJR: 2.255, h-index: 171)
American J. of Ophthalmology     Hybrid Journal   (Followers: 59, SJR: 2.803, h-index: 148)
American J. of Ophthalmology Case Reports     Open Access   (Followers: 6)
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: 27, SJR: 2.653, h-index: 228)
American J. of Preventive Medicine     Hybrid Journal   (Followers: 25, SJR: 2.764, h-index: 154)
American J. of Surgery     Hybrid Journal   (Followers: 35, 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: 6)
Anaerobe     Hybrid Journal   (Followers: 4, SJR: 1.066, h-index: 51)
Anaesthesia & Intensive Care Medicine     Full-text available via subscription   (Followers: 58, SJR: 0.124, h-index: 9)
Anaesthesia Critical Care & Pain Medicine     Full-text available via subscription   (Followers: 12)
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: 168, 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: 12)
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: 173, SJR: 1.907, h-index: 126)

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Journal Cover Acta Astronautica
  [SJR: 0.726]   [H-I: 43]   [364 followers]  Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0094-5765
   Published by Elsevier Homepage  [3049 journals]
  • Sintering of micro-trusses created by extrusion-3D-printing of lunar
           regolith inks
    • Authors: Shannon L. Taylor; Adam E. Jakus; Katie D. Koube; Amaka J. Ibeh; Nicholas R. Geisendorfer; Ramille N. Shah; David C. Dunand
      Pages: 1 - 8
      Abstract: Publication date: February 2018
      Source:Acta Astronautica, Volume 143
      Author(s): Shannon L. Taylor, Adam E. Jakus, Katie D. Koube, Amaka J. Ibeh, Nicholas R. Geisendorfer, Ramille N. Shah, David C. Dunand
      The development of in situ fabrication methods for the infrastructure required to support human life on the Moon is necessary due to the prohibitive cost of transporting large quantities of materials from the Earth. Cellular structures, consisting of a regular network (truss) of micro-struts with ∼500 μm diameters, suitable for bricks, blocks, panels, and other load-bearing structural elements for habitats and other infrastructure are created by direct-extrusion 3D-printing of liquid inks containing JSC-1A lunar regolith simulant powders, followed by sintering. The effects of sintering time, temperature, and atmosphere (air or hydrogen) on the microstructures, mechanical properties, and magnetic properties of the sintered lunar regolith micro-trusses are investigated. The air-sintered micro-trusses have higher relative densities, linear shrinkages, and peak compressive strengths, due to the improved sintering of the struts within the micro-trusses achieved by a liquid or glassy phase. Whereas the hydrogen-sintered micro-trusses show no liquid-phase sintering or glassy phase, they contain metallic iron 0.1–2 μm particles from the reduction of ilmenite, which allows them to be lifted with magnets.

      PubDate: 2017-11-24T17:46:02Z
      DOI: 10.1016/j.actaastro.2017.11.005
      Issue No: Vol. 143 (2017)
  • Spherical gyroscopic moment stabilizer for attitude control of
    • Authors: Sajjad Keshtkar; Jaime A. Moreno; Hirohisa Kojima; Kenji Uchiyama; Masahiro Nohmi; Keisuke Takaya
      Pages: 9 - 15
      Abstract: Publication date: February 2018
      Source:Acta Astronautica, Volume 143
      Author(s): Sajjad Keshtkar, Jaime A. Moreno, Hirohisa Kojima, Kenji Uchiyama, Masahiro Nohmi, Keisuke Takaya
      This paper presents a new and improved concept of recently proposed two-degrees of freedom spherical stabilizer for triaxial orientation of microsatellites. The analytical analysis of the advantages of the proposed mechanism over the existing inertial attitude control devices are introduced. The extended equations of motion of the stabilizing satellite including the spherical gyroscope, for control law design and numerical simulations, are studied in detail. A new control algorithm based on continuous high-order sliding mode algorithms, for managing the torque produced by the stabilizer and therefore the attitude control of the satellite in the presence of perturbations/uncertainties, is presented. Some numerical simulations are carried out to prove the performance of the proposed mechanism and control laws.

      PubDate: 2017-11-24T17:46:02Z
      DOI: 10.1016/j.actaastro.2017.10.033
      Issue No: Vol. 143 (2017)
  • Trajectory design for Saturnian Ocean Worlds orbiters using
           multidimensional Poincaré maps
    • Authors: Diane Craig Davis; Sean M. Phillips; Brian P. McCarthy
      Pages: 16 - 28
      Abstract: Publication date: February 2018
      Source:Acta Astronautica, Volume 143
      Author(s): Diane Craig Davis, Sean M. Phillips, Brian P. McCarthy
      Missions based on low-energy orbits in the vicinity of planetary moons, such as Titan or Enceladus, involve significant end-to-end trajectory design challenges due to the gravitational effects of the distant larger primary. To address these challenges, the current investigation focuses on the visualization and use of multidimensional Poincaré maps to perform preliminary design of orbits with significant out-of-plane components, including orbits that provide polar coverage. Poincaré maps facilitate the identification of families of solutions to a given orbit problem and provide the ability to easily respond to changing inputs and requirements. A visual-based design process highlights a variety of trajectory options near Saturn's ocean worlds, including both moon-centered orbits and libration point orbits.

      PubDate: 2017-11-24T17:46:02Z
      DOI: 10.1016/j.actaastro.2017.11.004
      Issue No: Vol. 143 (2017)
  • Interstellar communication. II. Application to the solar gravitational
    • Authors: Michael Hippke
      Pages: 64 - 74
      Abstract: Publication date: January 2018
      Source:Acta Astronautica, Volume 142
      Author(s): Michael Hippke
      We have shown in paper I of this series [1] that interstellar communication to nearby (pc) stars is possible at data rates of bits per second per Watt between a 1 m sized probe and a large receiving telescope (E-ELT, 39 m), when optimizing all parameters such as frequency at 300–400 nm. We now apply our framework of interstellar extinction and quantum state calculations for photon encoding to the solar gravitational lens (SGL), which enlarges the aperture (and thus the photon flux) of the receiving telescope by a factor of > 10 9 . For the first time, we show that the use of the SGL for communication purposes is possible. This was previously unclear because the Einstein ring is placed inside the solar coronal noise, and contributing factors are difficult to determine. We calculate point-spread functions, aperture sizes, heliocentric distance, and optimum communication frequency. The best wavelength for nearby ( < 100 pc) interstellar communication is limited by current technology to the UV and optical band. To suppress coronal noise, an advanced coronograph is required, alternatively an occulter could be used which would require a second spacecraft in formation flight 78 km from the receiver, and ≈ 10 m in size. Data rates scale approximately linear with the SGL telescope size and with heliocentric distance. Achievable (receiving) data rates from α Cen are of order 10 Mbits per second per Watt for a pair of meter-sized telescopes, an improvement of 10 7 compared to using the same receiving telescope without the SGL. A 1 m telescope in the SGL can receive data at rates comparable to a km-class “normal” telescope.

      PubDate: 2017-11-11T07:43:12Z
      DOI: 10.1016/j.actaastro.2017.10.022
      Issue No: Vol. 142 (2017)
  • Recovering area-to-mass ratio of resident space objects through data
    • Authors: Hao Peng; Xiaoli Bai
      Pages: 75 - 86
      Abstract: Publication date: January 2018
      Source:Acta Astronautica, Volume 142
      Author(s): Hao Peng, Xiaoli Bai
      The area-to-mass ratio (AMR) of a resident space object (RSO) is an important parameter for improved space situation awareness capability due to its effect on the non-conservative forces including the atmosphere drag force and the solar radiation pressure force. However, information about AMR is often not provided in most space catalogs. The present paper investigates recovering the AMR information from the consistency error, which refers to the difference between the orbit predicted from an earlier estimate and the orbit estimated at the current epoch. A data mining technique, particularly the random forest (RF) method, is used to discover the relationship between the consistency error and the AMR. Using a simulation-based space catalog environment as the testbed, this paper demonstrates that the classification RF model can determine the RSO's category AMR and the regression RF model can generate continuous AMR values, both with good accuracies. Furthermore, the paper reveals that by recording additional information besides the consistency error, the RF model can estimate the AMR with even higher accuracy.

      PubDate: 2017-11-11T07:43:12Z
      DOI: 10.1016/j.actaastro.2017.09.030
      Issue No: Vol. 142 (2017)
  • Space strategy and governance of ESA small member states
    • Authors: Daniel Sagath; Angeliki Papadimitriou; Maarten Adriaensen; Christina Giannopapa
      Pages: 112 - 120
      Abstract: Publication date: January 2018
      Source:Acta Astronautica, Volume 142
      Author(s): Daniel Sagath, Angeliki Papadimitriou, Maarten Adriaensen, Christina Giannopapa
      The European Space Agency (ESA) has twenty-two Member States with a variety of governance structures and strategic priorities regarding their space activities. The objective of this paper is to provide an up-to date overview and a holistic assessment of the national space governance structures and strategic priorities of the eleven smaller Member States (based on annual ESA contributions). A link is made between the governance structure and the main strategic objectives. The specific needs and interests of small and new Member States in the frame of European Space Integration are addressed. The first part of the paper focuses on the national space governance structures in the eleven smaller ESA Member States. The governance models of these Member States are identified including the responsible ministries and the entities entrusted with the implementation of space strategy/policy and programmes of the country. The second part of this paper focuses on the content and analysis of the national space strategies and indicates the main priorities and trends in the eleven smaller ESA Member States. The priorities are categorised with regards to technology domains, the role of space in the areas of sustainability and the motivators for space investments. In a third and final part, attention is given to the specific needs and interests of the smaller Member States in the frame of European space integration. ESA instruments are tailored to facilitate the needs and interests of the eleven smaller and/or new Member States.

      PubDate: 2017-11-11T07:43:12Z
      DOI: 10.1016/j.actaastro.2017.09.029
      Issue No: Vol. 142 (2017)
  • Formation mechanisms and characteristics of transition patterns in oblique
    • Authors: Shikun Miao; Jin Zhou; Shijie Liu; Xiaodong Cai
      Pages: 121 - 129
      Abstract: Publication date: January 2018
      Source:Acta Astronautica, Volume 142
      Author(s): Shikun Miao, Jin Zhou, Shijie Liu, Xiaodong Cai
      The transition structures of wedge-induced oblique detonation waves (ODWs) in high-enthalpy supersonic combustible mixtures are studied with two-dimensional reactive Euler simulations based on the open-source program AMROC (Adaptive Mesh Refinement in Object-oriented C++). The formation mechanisms of different transition patterns are investigated through theoretical analysis and numerical simulations. Results show that transition patterns of ODWs depend on the pressure ratio P d/P s, (P d, P s are the pressure behind the ODW and the pressure behind the induced shock, respectively). When P d/P s > 1.3, an abrupt transition occurs, while when P d/P s < 1.3, a smooth transition appears. A parameter ε is introduced to describe the transition patterns quantitatively. Besides, a criterion based on the velocity ratio Φ=U 0 /U CJ is proposed to predict the transition patterns based on the inflow conditions. It is concluded that an abrupt transition appears when Φ < 0.98Φ * , while a smooth transition occurs when Φ > 1.02Φ ∗ (Φ ∗ is the critical velocity ratio calculated with an empirical formula).

      PubDate: 2017-11-11T07:43:12Z
      DOI: 10.1016/j.actaastro.2017.10.035
      Issue No: Vol. 142 (2017)
  • Similarity solutions for unsteady flow behind an exponential shock in a
           self-gravitating non-ideal gas with azimuthal magnetic field
    • Authors: G. Nath; R.P. Pathak; Mrityunjoy Dutta
      Pages: 152 - 161
      Abstract: Publication date: January 2018
      Source:Acta Astronautica, Volume 142
      Author(s): G. Nath, R.P. Pathak, Mrityunjoy Dutta
      Similarity solutions for the flow of a non-ideal gas behind a strong exponential shock driven out by a piston (cylindrical or spherical) moving with time according to an exponential law is obtained. Solutions are obtained, in both the cases, when the flow between the shock and the piston is isothermal or adiabatic. The shock wave is driven by a piston moving with time according to an exponential law. Similarity solutions exist only when the surrounding medium is of constant density. The effects of variation of ambient magnetic field, non-idealness of the gas, adiabatic exponent and gravitational parameter are worked out in detail. It is shown that the increase in the non-idealness of the gas or the adiabatic exponent of the gas or presence of magnetic field have decaying effect on the shock wave. Consideration of the isothermal flow and the self-gravitational field increase the shock strength. Also, the consideration of isothermal flow or the presence of magnetic field removes the singularity in the density distribution, which arises in the case of adiabatic flow. The result of our study may be used to interpret measurements carried out by space craft in the solar wind and in neighborhood of the Earth's magnetosphere.

      PubDate: 2017-11-11T07:43:12Z
      DOI: 10.1016/j.actaastro.2017.10.029
      Issue No: Vol. 142 (2017)
  • Tether cutting maneuver in swing-by trajectory
    • Authors: Tsubasa Yamasaki; Mai Bando; Shinji Hokamoto
      Pages: 212 - 220
      Abstract: Publication date: January 2018
      Source:Acta Astronautica, Volume 142
      Author(s): Tsubasa Yamasaki, Mai Bando, Shinji Hokamoto
      The swing-by maneuver is known as a method to change the velocity of a spacecraft by using the gravity force of the celestial body. The powered swing-by has been studied to enhance the velocity change during the swing-by maneuver. This paper studies another way of the powered swing-by using tether cutting, which does not require additional propellant consumption, and shows that the proposed powered swing-by can increase the effect of the swing-by as same as using impulsive thrust. Moreover, it is discussed whether the system has possibility to realize both the powered swing-by of a mother satellite and the planetary capture of a subsatellite simultaneously.

      PubDate: 2017-11-24T17:46:02Z
      DOI: 10.1016/j.actaastro.2017.11.002
      Issue No: Vol. 142 (2017)
  • Concentrated energy addition for active drag reduction in hypersonic flow
    • Authors: M. Ashwin Ganesh; Bibin John
      Pages: 221 - 231
      Abstract: Publication date: January 2018
      Source:Acta Astronautica, Volume 142
      Author(s): M. Ashwin Ganesh, Bibin John
      Numerical optimization of hypersonic drag reduction technique based on concentrated energy addition is presented in this study. A reduction in wave drag is realized through concentrated energy addition in the hypersonic flowfield upstream of the blunt body. For the exhaustive optimization presented in this study, an in-house high precision inviscid flow solver has been developed. Studies focused on the identification of “optimum energy addition location” have revealed the existence of multiple minimum drag points. The wave drag coefficient is observed to drop from 0.85 to 0.45 when 50 Watts of energy is added to an energy bubble of 1 mm radius located at 74.7 mm upstream of the stagnation point. A direct proportionality has been identified between energy bubble size and wave drag coefficient. Dependence of drag coefficient on the upstream added energy magnitude is also revealed. Of the observed multiple minimum drag points, the energy deposition point (EDP) that offers minimum wave drag just after a sharp drop in drag is proposed as the most optimum energy addition location.

      PubDate: 2017-11-24T17:46:02Z
      DOI: 10.1016/j.actaastro.2017.11.003
      Issue No: Vol. 142 (2017)
  • Dynamics and offset control of tethered space-tug system
    • Authors: Jingrui Zhang; Keying Yang; Rui Qi
      Pages: 232 - 252
      Abstract: Publication date: January 2018
      Source:Acta Astronautica, Volume 142
      Author(s): Jingrui Zhang, Keying Yang, Rui Qi
      Tethered space-tug system is regarded as one of the most promising active debris removal technologies to effectively decrease the steep increasing population of space debris. In order to suppress the spin of space debris, single-tethered space-tug system is employed by regulating the tether. Unfortunately, this system is underactuated as tether length is the only input, and there are two control objectives: the spinning debris and the vibration of tether. Thus, it may suffer great oscillations and result in failure in space debris removal. This paper presents the study of attitude stabilization of the single-tethered space-tug system using not only tether length but also the offset of tether attachment point to suppress the spin of debris, so as to accomplish the space debris removal mission. Firstly, a precise 3D mathematical model in which the debris and tug are both treated as rigid bodies is developed to study the dynamical evolution of the tethered space-tug system. The relative motion equation of the system is described using Lagrange method. Secondly, the dynamic characteristic of the system is analyzed and an offset control law is designed to stabilize the spin of debris by exploiting the variation of tether offset and the regulation of tether length. Besides, an estimation formula is proposed to evaluate the capability of tether for suppressing spinning debris. Finally, the effectiveness of attitude stabilization by the utilization of the proposed scheme is demonstrated via numerical case studies.

      PubDate: 2017-11-24T17:46:02Z
      DOI: 10.1016/j.actaastro.2017.10.020
      Issue No: Vol. 142 (2017)
  • An adaptive reentry guidance method considering the influence of blackout
    • Authors: Yu Wu; Jianyao Yao; Xiangju Qu
      Pages: 253 - 264
      Abstract: Publication date: January 2018
      Source:Acta Astronautica, Volume 142
      Author(s): Yu Wu, Jianyao Yao, Xiangju Qu
      Reentry guidance has been researched as a popular topic because it is critical for a successful flight. In view that the existing guidance methods do not take into account the accumulated navigation error of Inertial Navigation System (INS) in the blackout zone, in this paper, an adaptive reentry guidance method is proposed to obtain the optimal reentry trajectory quickly with the target of minimum aerodynamic heating rate. The terminal error in position and attitude can be also reduced with the proposed method. In this method, the whole reentry guidance task is divided into two phases, i.e., the trajectory updating phase and the trajectory planning phase. In the first phase, the idea of model predictive control (MPC) is used, and the receding optimization procedure ensures the optimal trajectory in the next few seconds. In the trajectory planning phase, after the vehicle has flown out of the blackout zone, the optimal reentry trajectory is obtained by online planning to adapt to the navigation information. An effective swarm intelligence algorithm, i.e. pigeon inspired optimization (PIO) algorithm, is applied to obtain the optimal reentry trajectory in both of the two phases. Compared to the trajectory updating method, the proposed method can reduce the terminal error by about 30% considering both the position and attitude, especially, the terminal error of height has almost been eliminated. Besides, the PIO algorithm performs better than the particle swarm optimization (PSO) algorithm both in the trajectory updating phase and the trajectory planning phases.

      PubDate: 2017-11-24T17:46:02Z
      DOI: 10.1016/j.actaastro.2017.10.041
      Issue No: Vol. 142 (2017)
  • Determination of disturbances acting on small satellite mock-up on air
           bearing table
    • Authors: D. Ivanov; M. Koptev; Y. Mashtakov; M. Ovchinnikov; N. Proshunin; S. Tkachev; A. Fedoseev; M. Shachkov
      Pages: 265 - 276
      Abstract: Publication date: January 2018
      Source:Acta Astronautica, Volume 142
      Author(s): D. Ivanov, M. Koptev, Y. Mashtakov, M. Ovchinnikov, N. Proshunin, S. Tkachev, A. Fedoseev, M. Shachkov
      In this paper the facility for the simulation of satellite motion based on planar air-bearing deweighting is considered. The air bearing provides almost frictionless horizontal motion of the small satellite mock-ups. Due to the presence of gravitational and air flow disturbances the motion is far from rectilinear and uniform. This paper is devoted to the determination of these disturbances.

      PubDate: 2017-11-24T17:46:02Z
      DOI: 10.1016/j.actaastro.2017.11.010
      Issue No: Vol. 142 (2017)
  • Observability of satellite launcher navigation with INS, GPS, attitude
           sensors and reference trajectory
    • Authors: Yanick Beaudoin; André Desbiens; Eric Gagnon; René Landry
      Pages: 277 - 288
      Abstract: Publication date: January 2018
      Source:Acta Astronautica, Volume 142
      Author(s): Yanick Beaudoin, André Desbiens, Eric Gagnon, René Landry
      The navigation system of a satellite launcher is of paramount importance. In order to correct the trajectory of the launcher, the position, velocity and attitude must be known with the best possible precision. In this paper, the observability of four navigation solutions is investigated. The first one is the INS/GPS couple. Then, attitude reference sensors, such as magnetometers, are added to the INS/GPS solution. The authors have already demonstrated that the reference trajectory could be used to improve the navigation performance. This approach is added to the two previously mentioned navigation systems. For each navigation solution, the observability is analyzed with different sensor error models. First, sensor biases are neglected. Then, sensor biases are modelled as random walks and as first order Markov processes. The observability is tested with the rank and condition number of the observability matrix, the time evolution of the covariance matrix and sensitivity to measurement outlier tests. The covariance matrix is exploited to evaluate the correlation between states in order to detect structural unobservability problems. Finally, when an unobservable subspace is detected, the result is verified with theoretical analysis of the navigation equations. The results show that evaluating only the observability of a model does not guarantee the ability of the aiding sensors to correct the INS estimates within the mission time. The analysis of the covariance matrix time evolution could be a powerful tool to detect this situation, however in some cases, the problem is only revealed with a sensitivity to measurement outlier test. None of the tested solutions provide GPS position bias observability. For the considered mission, the modelling of the sensor biases as random walks or Markov processes gives equivalent results. Relying on the reference trajectory can improve the precision of the roll estimates. But, in the context of a satellite launcher, the roll estimation error and gyroscope bias are only observable if attitude reference sensors are present.

      PubDate: 2017-11-24T17:46:02Z
      DOI: 10.1016/j.actaastro.2017.10.038
      Issue No: Vol. 142 (2017)
  • Investigation of drag and heat reduction induced by a novel combinational
           lateral jet and spike concept in supersonic flows based on conjugate heat
           transfer approach
    • Authors: Liang Zhu; Xiong Chen; Yingkun Li; Omer Musa; Changsheng Zhou
      Pages: 300 - 313
      Abstract: Publication date: January 2018
      Source:Acta Astronautica, Volume 142
      Author(s): Liang Zhu, Xiong Chen, Yingkun Li, Omer Musa, Changsheng Zhou
      When flying at supersonic or hypersonic speeds through the air, the drag and severe heating have a great impact on the vehicles, thus the drag reduction and thermal protection studies have attracted worldwide attention. In the current study, the Reynolds-averaged Navier-Stokes (RANS) equations coupled with the shear stress transport (SST) k − ω turbulence model have been employed to investigate the flow behavior induced by a novel combinational lateral jet and spike concept in supersonic flows. A coupling conjugate heat transfer (CHT) approach has been applied to investigate the thermal protection, which takes the heat transfer of structure into consideration. After the code was validated by the available experimental results and the gird independency analysis was carried out, the influences of the spike length ratio, lateral jet pressure ratio and lateral jet location on the drag and heat reduction performance are analyzed comprehensively. The obtained results show that a remarkable reduction in the drag and heat flux is achieved when a lateral jet is added to the spike. This implies that the combinational lateral jet and spike concept in supersonic flows have a great benefit to the drag and heat reduction. Both the drag and heat reduction decrease with the increase of the lateral jet pressure ratio, and the heat flux is more sensitive to the lateral jet pressure ratio. The lateral jet should not be located in the bottom of the spike in order to realize better drag and heat reduction performance. The drag and heat flux could be reduced by about 45% by reasonable lateral jet location. The drag decreases with the increase of the spike length ratio whereas the heat flux is affected by the spike length ratio just in a certain range.

      PubDate: 2017-11-24T17:46:02Z
      DOI: 10.1016/j.actaastro.2017.11.001
      Issue No: Vol. 142 (2017)
  • 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)
  • Open innovation in the European space sector: Existing practices,
           constraints and opportunities
    • Authors: Elco van Burg; Christina Giannopapa; Isabelle M.M.J. Reymen
      Pages: 17 - 21
      Abstract: Publication date: December 2017
      Source:Acta Astronautica, Volume 141
      Author(s): Elco van Burg, Christina Giannopapa, Isabelle M.M.J. Reymen
      To enhance innovative output and societal spillover of the European space sector, the open innovation approach is becoming popular. Yet, open innovation, referring to innovation practices that cross borders of individual firms, faces constraints. To explore these constraints and identify opportunities, this study performs interviews with government/agency officials and space technology entrepreneurs. The interviews highlight three topic areas with constraints and opportunities: 1) mainly one-directional knowledge flows (from outside the space sector to inside), 2) knowledge and property management, and 3) the role of small- and medium sized companies. These results bear important implications for innovation practices in the space sector.

      PubDate: 2017-11-05T17:02:28Z
      DOI: 10.1016/j.actaastro.2017.09.019
      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)
  • Planar rigid-flexible coupling spacecraft modeling and control considering
           solar array deployment and joint clearance
    • Authors: Yuanyuan Li; Zilu Wang; Cong Wang; Wenhu Huang
      Pages: 243 - 255
      Abstract: Publication date: Available online 28 October 2017
      Source:Acta Astronautica
      Author(s): Yuanyuan Li, Zilu Wang, Cong Wang, Wenhu Huang
      Based on Nodal Coordinate Formulation (NCF) and Absolute Nodal Coordinate Formulation (ANCF), this paper establishes rigid-flexible coupling dynamic model of the spacecraft with large deployable solar arrays and multiple clearance joints to analyze and control the satellite attitude under deployment disturbance. Considering torque spring, close cable loop (CCL) configuration and latch mechanisms, a typical spacecraft composed of a rigid main-body described by NCF and two flexible panels described by ANCF is used as a demonstration case. Nonlinear contact force model and modified Coulomb friction model are selected to establish normal contact force and tangential friction model, respectively. Generalized elastic force are derived and all generalized forces are defined in the NCF-ANCF frame. The Newmark-β method is used to solve system equations of motion. The availability and superiority of the proposed model is verified through comparing with numerical co-simulations of Patran and ADAMS software. The numerical results reveal the effects of panel flexibility, joint clearance and their coupling on satellite attitude. The effects of clearance number, clearance size and clearance stiffness on satellite attitude are investigated. Furthermore, a proportional-differential (PD) attitude controller of spacecraft is designed to discuss the effect of attitude control on the dynamic responses of the whole system.

      PubDate: 2017-11-05T17:02:28Z
      DOI: 10.1016/j.actaastro.2016.12.032
      Issue No: Vol. 132 (2017)
  • Adaptive relative pose control of spacecraft with model couplings and
    • Authors: Liang Sun; Zewei Zheng
      Abstract: Publication date: Available online 11 November 2017
      Source:Acta Astronautica
      Author(s): Liang Sun, Zewei Zheng
      The spacecraft pose tracking control problem for an uncertain pursuer approaching to a space target is researched in this paper. After modeling the nonlinearly coupled dynamics for relative translational and rotational motions between two spacecraft, position tracking and attitude synchronization controllers are developed independently by using a robust adaptive control approach. The unknown kinematic couplings, parametric uncertainties, and bounded external disturbances are handled with adaptive updating laws. It is proved via Lyapunov method that the pose tracking errors converge to zero asymptotically. Spacecraft close-range rendezvous and proximity operations are introduced as an example to validate the effectiveness of the proposed control approach.

      PubDate: 2017-11-11T07:43:12Z
      DOI: 10.1016/j.actaastro.2017.11.006
  • Publication Information
    • Abstract: Publication date: December 2017
      Source:Acta Astronautica, Volume 141

      PubDate: 2017-11-05T17:02:28Z
  • Accuracy enhancement of navigation images using blind restoration method
    • Authors: Jianhui Zhao; Cundu Zhang; Tao Yu; Fan Li
      Abstract: Publication date: Available online 1 November 2017
      Source:Acta Astronautica
      Author(s): Jianhui Zhao, Cundu Zhang, Tao Yu, Fan Li
      Optical navigation is one of the most promising technologies in the area of deep space autonomous navigation. However, since the optical images are strict motion blurred images, it is difficult to extract the lines of sight (LOS) to the beacons to reckon the spacecraft attitude and orbital position during the deep space cruise phase. This paper proposes a new blind restoration approach to effectively recover the clear image. We use a modified median filter to eliminate the black and white noises, and also, construct a blind estimation model, built on the sparsity of the gradient of navigation image, to estimate the global point spread function (PSF). Moreover, we select a few bright beacons to recover the motion blurred image, where the average value of the beacon centroid is adopted to calculate the relative position for the optical navigation. We present the simulation and actual image restoration experiment to demonstrate the accuracy and consistency of the relative position of the recovered navigation image of the proposed method. We show that the proposed method presents superior performance in comparison with the multiple cross correlation method. The estimated PSF is close to real PSF and the distributed energy of the beacon is concentrated ensuring a high SNR, where the accuracy of the relative position is higher than 0.1 pixel.

      PubDate: 2017-11-05T17:02:28Z
      DOI: 10.1016/j.actaastro.2017.10.037
  • Numerical simulation of divergent rocket-based-combined-cycle performances
           under the flight condition of Mach 3
    • Authors: Peng Cui; WanWu Qinglian
      Abstract: Publication date: Available online 29 October 2017
      Source:Acta Astronautica
      Author(s): Peng Cui, WanWu Xu, Qinglian Li
      Currently, the upper operating limit of the turbine engine is Mach 2+, and the lower limit of the dual-mode scramjet is Mach 4. Therefore no single power systems can operate within the range between Mach 2 + and Mach 4. By using ejector rockets, Rocket-based-combined-cycle can work well in the above scope. As the key component of Rocket-based-combined-cycle, the ejector rocket has significant influence on Rocket-based-combined-cycle performance. Research on the influence of rocket parameters on Rocket-based-combined-cycle in the speed range of Mach 2 + to Mach 4 is scarce. In the present study, influences of Mach number and total pressure of the ejector rocket on Rocket-based-combined-cycle were analyzed numerically. Due to the significant effects of the flight conditions and the Rocket-based-combined-cycle configuration on Rocket-based-combined-cycle performances, flight altitude, flight Mach number, and divergence ratio were also considered. The simulation results indicate that matching lower altitude with higher flight Mach numbers can increase Rocket-based-combined-cycle thrust. For another thing, with an increase of the divergent ratio, the effect of the divergent configuration will strengthen and there is a limit on the divergent ratio. When the divergent ratio is greater than the limit, the effect of divergent configuration will gradually exceed that of combustion on supersonic flows. Further increases in the divergent ratio will decrease Rocket-based-combined-cycle thrust.

      PubDate: 2017-11-05T17:02:28Z
  • Real-time maneuver optimization of space-based robots in a dynamic
           environment: Theory and on-orbit experiments
    • Authors: Gregory Chamitoff; Alvar Saenz-Otero Jacob Katz Steve Ulrich Benjamin Morrell
      Abstract: Publication date: Available online 28 October 2017
      Source:Acta Astronautica
      Author(s): Gregory E. Chamitoff, Alvar Saenz-Otero, Jacob G. Katz, Steve Ulrich, Benjamin J. Morrell, Peter W. Gibbens
      This paper presents the development of a real-time path-planning optimization approach to controlling the motion of space-based robots. The algorithm is capable of planning three dimensional trajectories for a robot to navigate within complex surroundings that include numerous static and dynamic obstacles, path constraints and performance limitations. The methodology employs a unique transformation that enables rapid generation of feasible solutions for complex geometries, making it suitable for application to real-time operations and dynamic environments. This strategy was implemented on the Synchronized Position Hold Engage Reorient Experimental Satellite (SPHERES) test-bed on the International Space Station (ISS), and experimental testing was conducted onboard the ISS during Expedition 17 by the first author. Lessons learned from the on-orbit tests were used to further refine the algorithm for future implementations.

      PubDate: 2017-11-05T17:02:28Z
  • Which benefits and limits derive from ESA membership for European
           Countries owning “medium-sized” space agencies'
    • Authors: Giorgio Petroni; Barbara Bigliardi; Francesco Galati; Alberto Petroni
      Abstract: Publication date: Available online 28 October 2017
      Source:Acta Astronautica
      Author(s): Giorgio Petroni, Barbara Bigliardi, Francesco Galati, Alberto Petroni
      This study investigates the benefits and limits deriving from membership with ESA of six medium-sized space agencies in terms of strengthening and development (or not) of space technologies, as well as their contribution to the growth of productive activities and to the increase of services for citizens. This research contributes to the more general issue of the usefulness of space activities, not only for scientific or military-political purposes but also for economic and social development. Results show that, on the one hand, the membership with ESA has allowed smaller Countries to access space programs, to develop advanced technologies and to support the growth of their firms in some significant markets, but, on the other hand, the membership has also limited the access to space to few companies, without encouraging the broad dissemination of technological knowledge.

      PubDate: 2017-10-28T13:08:43Z
      DOI: 10.1016/j.actaastro.2017.10.032
  • Institutional patterns in the Austrian space sector
    • Authors: Annie Wong; Elco van Burg; Christina Giannopapa
      Abstract: Publication date: Available online 27 October 2017
      Source:Acta Astronautica
      Author(s): Annie Wong, Elco van Burg, Christina Giannopapa
      This paper employs the institutional logics perspective to understand how space policies and regulations influences entrepreneurship and innovation. We conducted interviews with entrepreneurs, ESA policy makers and governmental representatives in Austria and identified six prevailing institutional practices: geographical return, the SME-initiatives, the national support pattern, the size pattern, the consortium pattern and the experience pattern. Together, these patterns make up the semi-governmental logic of the space sector. We find that space actors adhere to these patterns to earn legitimacy, which is a condition for support and access to resources. This study adds to our understanding in the consequences of policies and contributes to the design of new space policies and programmes.

      PubDate: 2017-10-28T13:08:43Z
      DOI: 10.1016/j.actaastro.2017.10.030
  • Analysis of atomic oxygen and ultraviolet exposure effects on
           cycloaliphatic epoxy resins reinforced with octa-functional POSS
    • Authors: Agnieszka Suliga; Ewa M. Jakubczyk; Ian Hamerton; Andrew Viquerat
      Abstract: Publication date: Available online 25 October 2017
      Source:Acta Astronautica
      Author(s): Agnieszka Suliga, Ewa M. Jakubczyk, Ian Hamerton, Andrew Viquerat
      In this study, novel nanocomposites were created by incorporation of Silsesquioxane containing eight glycidylether groups (octa-POSS) into a cycloaliphatic epoxy cured by an anhydride. The developed resin system, with different nanoparticle concentrations, was used on the outer layers of an ultra-thin CFRP structure in order to provide better environmental resistance to the environment of low Earth orbit (LEO) which was tested in a ground-simulation facility. The developed resins were subjected to space-like degrading factors and their response to corrosion, radiation and elevated temperatures was monitored by mass loss, together with measuring changes in surface chemistry (ATR-FTIR), functionality development (contact angle measurement and XPS), roughness (scanning laser microscopy) and morphology (SEM). The influence of increasing octa-POSS content on thermo-mechanical properties was measured with DMTA and the strength and modulus of elasticity were determined by flexural test. The addition of octa-POSS in any loading improves the environmental resistance, however, the most significant retention of mass and mechanical and surface properties after space-like exposure was observed in the 20 wt% octa-POSS reinforced cycloaliphatic epoxy. The results presented here may contribute to the development of novel class of nanocomposites which can offer an extended service life in LEO.

      PubDate: 2017-10-28T13:08:43Z
      DOI: 10.1016/j.actaastro.2017.10.018
  • High-frequency counter-flow plasma synthetic jet actuator and its
           application in suppression of supersonic flow separation
    • Authors: Hongyu Wang; Jun Li; Di Jin; Mengxiao Tang; Yun Wu; Lianghua Xiao
      Abstract: Publication date: Available online 21 October 2017
      Source:Acta Astronautica
      Author(s): Hongyu Wang, Jun Li, Di Jin, Mengxiao Tang, Yun Wu, Lianghua Xiao
      We come up with a control strategy for suppression of supersonic flow separation based on high-frequency Counter-flow Plasma Synthetic Jet Actuator (CPSJA). The main purpose of this investigation is to verify if its control authority can be enhanced by the jet/shock interaction. We use a blunt nose to generate a bow shock, a step on a flat plate to introduce a massive separation in a Mach 2 wind tunnel, and the CPSJA to generate Plasma Synthetic Jet (PSJ). In this study, pulsed capacitive discharge is provided for an array of CPSJAs, which makes the actuation (discharge) frequency f 1 = 1 kHz, f 2 = 2 kHz and f 3 = 3 kHz. We use the high-speed schlieren imaging and fast response pressure transducers as well as a numerical simulation to investigate the quiescent PSJ properties, the interaction between the jet and bow shock, and its disturbance effect on the downstream separated region. The schlieren images show that PSJ is characterized by a succession of vortex rings; the jet strength weakens with the increase of frequency. A 4.5 mN jet thrust is found for all the frequencies. The simulation results show that jet/shock interaction produces vorticity in the vortex ring of the jet, enhancing turbulent mixing in PSJ so that a great deal of momentum is produced into the flow. We found the downstream flow is significantly disturbed by the enhanced actuation. Actuation with frequency of f 2, f 3 which is close to the natural frequency f n of the separation bubble suppresses the separation with the upstream laminar boundary layer being periodically attenuated, which has a better control effect than f 1. The control effect is sensitive to the position where PSJ interacts with the shear layer, but the amount of energy deposited in one pulse is not crucial in a separation reduction in the experiment.

      PubDate: 2017-10-28T13:08:43Z
      DOI: 10.1016/j.actaastro.2017.10.023
  • Aerodynamics and Aerothermodynamics of undulated re-entry vehicles
    • Authors: Kaushikh Arunvinthan; Nadaraja Pillai
      Abstract: Publication date: Available online 20 October 2017
      Source:Acta Astronautica
      Author(s): K. Kaushikh, S. Arunvinthan, S. Nadaraja Pillai
      Aerodynamic and aerothermodynamic analysis is a fundamental basis for the design of a hypersonic vehicle. In this work, aerodynamic and aerothermodynamic analyses of a blunt body vehicle with undulations on its after-body are studied with the help of numerical simulations. A crew exploration vehicle (CEV) is taken for initial analysis and undulations with varying amplitude and wavelength are introduced on CEV's after-body. Numerical simulations were carried out for CEV and for CEV with undulations at Mach 3.0 and 7.0 for angles of attack ranging from −20° to +20° with increments of +5°. The results show that introduction of undulations did not have a significant impact on mono stability and lift-drag characteristics of the vehicle. It was also observed that introduction of undulations improved the aerothermodynamic characteristics of CEV. A reduction of about 36% in maximum heat flux at Mach 3.0 and about 21% at Mach 7.0 compared to the maximum heat flux for CEV was observed.

      PubDate: 2017-10-21T14:55:04Z
  • Pulsar navigation using time of arrival (TOA) and time differential TOA
    • Authors: Ning Xiaolin; Yang Yuqing Gui Mingzhen Weiren Fang Jiancheng Liu
      Abstract: Publication date: Available online 20 October 2017
      Source:Acta Astronautica
      Author(s): Ning Xiaolin, Yang Yuqing, Gui Mingzhen, Wu Weiren, Fang Jiancheng, Liu Gang
      Pulsar navigation is a novel autonomous navigation method for deep-space missions. The pulsar navigation method using the time of arrival (TOA) determines the absolute position of the spacecraft. However, its accuracy is greatly affected by system errors, including the ephemeris error of the pulsar and the satellite-borne clock error. The time differential technique is an innovative method to eliminate these system errors. However, pulsar navigation using time differential TOA (TDTOA) can only provide an accurate relative position, and the absolute position is missing. To solve the problem, pulsar navigation using both TOA and TDTOA is proposed in this paper because the measurement of pulsar navigation using TDTOA is not only related to the current state vector but to the previous state vector. The previous state vector is replaced with its estimation, and the covariance matrix of the measurement noise is also derived. Simulations show that the accuracy of the new proposed pulsar navigation method is better than that only using TOA or TDTOA. Besides, the impact factors of the new proposed method are analyzed by simulations.

      PubDate: 2017-10-21T14:55:04Z
  • The Strata-1 experiment on small body regolith segregation
    • Authors: Marc Fries; Paul Abell Julie Brisset Daniel Britt Joshua Colwell
      Abstract: Publication date: Available online 20 October 2017
      Source:Acta Astronautica
      Author(s): Marc Fries, Paul Abell, Julie Brisset, Daniel Britt, Joshua Colwell, Adrienne Dove, Dan Durda, Lee Graham, Christine Hartzell, Kenneth Hrovat, Kristen John, Dakotah Karrer, Matthew Leonard, Stanley Love, Joseph Morgan, Jayme Poppin, Vincent Rodriguez, Paul Sánchez-Lana, Dan Scheeres, Akbar Whizin
      The Strata-1 experiment studies the mixing and segregation dynamics of regolith on small bodies by exposing a suite of regolith simulants to the microgravity environment aboard the International Space Station (ISS) for one year. This will improve our understanding of regolith dynamics and properties on small asteroids, and may assist in interpreting analyses of samples from missions to small bodies such as OSIRIS-REx, Hayabusa-1 and -2, and future missions to small bodies. The Strata-1 experiment consists of four evacuated tubes partially filled with regolith simulants. The simulants are chosen to represent models of regolith covering a range of complexity and tailored to inform and improve computational studies. The four tubes are regularly imaged while moving in response to the ambient vibrational environment using dedicated cameras. The imagery is then downlinked to the Strata-1 science team about every two months. Analyses performed on the imagery includes evaluating the extent of the segregation of Strata-1 samples and comparing the observations to computational models. After Strata-1's return to Earth, x-ray tomography and optical microscopy will be used to study the post-flight simulant distribution. Strata-1 is also a pathfinder for the new “1E” ISS payload class, which is intended to simplify and accelerate emplacement of experiments on board ISS.

      PubDate: 2017-10-21T14:55:04Z
  • The soviet manned lunar program N1-L3
    • Authors: Christian Lardier
      Abstract: Publication date: Available online 16 October 2017
      Source:Acta Astronautica
      Author(s): Christian Lardier
      The conquest of space was marked by the Moon race in which the two superpowers, the United States and the Soviet Union, were engaged in the 1960s. On the American side, the Apollo program culminated with the Man on the Moon in July 1969, 50 years ago. At the same time, the Soviet Union carried out a similar program which was kept secret for 20 years. This N1-L3 program was unveiled in August 1989. Its goal was to arrive on the Moon before the Americans. It included an original super-rocket, development of which began in June 1960. But this program became a national priority only in August 1964 and the super-rocket failed four times between 1969 and 1972. This article analyses the reasons for these failures, which led to the cancellation of the program in 1974.

      PubDate: 2017-10-21T14:55:04Z
      DOI: 10.1016/j.actaastro.2017.10.007
  • 2D Necklace Flower Constellations
    • Authors: David Arnas; Daniel Casanova; Eva Tresaco
      Abstract: Publication date: Available online 16 October 2017
      Source:Acta Astronautica
      Author(s): David Arnas, Daniel Casanova, Eva Tresaco
      The 2D Necklace Flower Constellation theory is a new design framework based on the 2D Lattice Flower Constellations that allows to expand the possibilities of design while maintaining the number of satellites in the configuration. The methodology presented is a generalization of the 2D Lattice design, where the concept of necklace is introduced in the formulation. This allows to assess the problem of building a constellation in orbit, or the study of the reconfiguration possibilities in a constellation. Moreover, this work includes three counting theorems that allow to know beforehand the number of possible configurations that the theory can provide. This new formulation is especially suited for design and optimization techniques.

      PubDate: 2017-10-21T14:55:04Z
      DOI: 10.1016/j.actaastro.2017.10.017
  • 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
  • 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
  • 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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