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Showing 1 - 200 of 3044 Journals sorted alphabetically
AASRI Procedia     Open Access   (Followers: 15)
Academic Pediatrics     Hybrid Journal   (Followers: 22, SJR: 1.402, h-index: 51)
Academic Radiology     Hybrid Journal   (Followers: 21, SJR: 1.008, h-index: 75)
Accident Analysis & Prevention     Partially Free   (Followers: 84, SJR: 1.109, h-index: 94)
Accounting Forum     Hybrid Journal   (Followers: 23, SJR: 0.612, h-index: 27)
Accounting, Organizations and Society     Hybrid Journal   (Followers: 29, 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: 343, 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: 214, SJR: 3.683, h-index: 202)
Acta Mathematica Scientia     Full-text available via subscription   (Followers: 5, SJR: 0.615, h-index: 21)
Acta Mechanica Solida Sinica     Full-text available via subscription   (Followers: 9, SJR: 0.442, h-index: 21)
Acta Oecologica     Hybrid Journal   (Followers: 10, SJR: 0.915, h-index: 53)
Acta Otorrinolaringologica (English Edition)     Full-text available via subscription   (Followers: 1)
Acta Otorrinolaringológica Española     Full-text available via subscription   (Followers: 3, SJR: 0.311, h-index: 16)
Acta Pharmaceutica Sinica B     Open Access   (Followers: 2)
Acta Poética     Open Access   (Followers: 4)
Acta Psychologica     Hybrid Journal   (Followers: 23, SJR: 1.365, h-index: 73)
Acta Sociológica     Open Access  
Acta Tropica     Hybrid Journal   (Followers: 6, SJR: 1.059, h-index: 77)
Acta Urológica Portuguesa     Open Access  
Actas Dermo-Sifiliograficas     Full-text available via subscription   (Followers: 4)
Actas Dermo-Sifiliográficas (English Edition)     Full-text available via subscription   (Followers: 3)
Actas Urológicas Españolas     Full-text available via subscription   (Followers: 4, SJR: 0.383, h-index: 19)
Actas Urológicas Españolas (English Edition)     Full-text available via subscription   (Followers: 2)
Actualites Pharmaceutiques     Full-text available via subscription   (Followers: 5, SJR: 0.141, h-index: 3)
Actualites Pharmaceutiques Hospitalieres     Full-text available via subscription   (Followers: 4, SJR: 0.112, h-index: 2)
Acupuncture and Related Therapies     Hybrid Journal   (Followers: 3)
Acute Pain     Full-text available via subscription   (Followers: 13)
Ad Hoc Networks     Hybrid Journal   (Followers: 11, SJR: 0.967, h-index: 57)
Addictive Behaviors     Hybrid Journal   (Followers: 15, SJR: 1.514, h-index: 92)
Addictive Behaviors Reports     Open Access   (Followers: 5)
Additive Manufacturing     Hybrid Journal   (Followers: 7, SJR: 1.039, h-index: 5)
Additives for Polymers     Full-text available via subscription   (Followers: 21)
Advanced Drug Delivery Reviews     Hybrid Journal   (Followers: 134, SJR: 5.2, h-index: 222)
Advanced Engineering Informatics     Hybrid Journal   (Followers: 11, SJR: 1.265, h-index: 53)
Advanced Powder Technology     Hybrid Journal   (Followers: 17, SJR: 0.739, h-index: 33)
Advances in Accounting     Hybrid Journal   (Followers: 9, SJR: 0.299, h-index: 15)
Advances in Agronomy     Full-text available via subscription   (Followers: 15, SJR: 2.071, h-index: 82)
Advances in Anesthesia     Full-text available via subscription   (Followers: 25, SJR: 0.169, h-index: 4)
Advances in Antiviral Drug Design     Full-text available via subscription   (Followers: 3)
Advances in Applied Mathematics     Full-text available via subscription   (Followers: 6, SJR: 1.054, h-index: 35)
Advances in Applied Mechanics     Full-text available via subscription   (Followers: 10, SJR: 0.801, h-index: 26)
Advances in Applied Microbiology     Full-text available via subscription   (Followers: 22, SJR: 1.286, h-index: 49)
Advances In Atomic, Molecular, and Optical Physics     Full-text available via subscription   (Followers: 16, SJR: 3.31, h-index: 42)
Advances in Biological Regulation     Hybrid Journal   (Followers: 4, SJR: 2.277, h-index: 43)
Advances in Botanical Research     Full-text available via subscription   (Followers: 3, SJR: 0.619, h-index: 48)
Advances in Cancer Research     Full-text available via subscription   (Followers: 25, SJR: 2.215, h-index: 78)
Advances in Carbohydrate Chemistry and Biochemistry     Full-text available via subscription   (Followers: 9, SJR: 0.9, h-index: 30)
Advances in Catalysis     Full-text available via subscription   (Followers: 5, SJR: 2.139, h-index: 42)
Advances in Cellular and Molecular Biology of Membranes and Organelles     Full-text available via subscription   (Followers: 12)
Advances in Chemical Engineering     Full-text available via subscription   (Followers: 25, 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: 10, SJR: 1.268, h-index: 45)
Advances in Clinical Chemistry     Full-text available via subscription   (Followers: 28, 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: 5)
Advances in DNA Sequence-Specific Agents     Full-text available via subscription   (Followers: 5)
Advances in Drug Research     Full-text available via subscription   (Followers: 22)
Advances in Ecological Research     Full-text available via subscription   (Followers: 41, SJR: 3.25, h-index: 43)
Advances in Engineering Software     Hybrid Journal   (Followers: 25, SJR: 0.486, h-index: 10)
Advances in Experimental Biology     Full-text available via subscription   (Followers: 7)
Advances in Experimental Social Psychology     Full-text available via subscription   (Followers: 40, SJR: 5.465, h-index: 64)
Advances in Exploration Geophysics     Full-text available via subscription   (Followers: 3)
Advances in Food and Nutrition Research     Full-text available via subscription   (Followers: 48, SJR: 0.674, h-index: 38)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 15)
Advances in Genetics     Full-text available via subscription   (Followers: 15, SJR: 2.558, h-index: 54)
Advances in Genome Biology     Full-text available via subscription   (Followers: 11)
Advances in Geophysics     Full-text available via subscription   (Followers: 6, SJR: 2.325, h-index: 20)
Advances in Heat Transfer     Full-text available via subscription   (Followers: 21, SJR: 0.906, h-index: 24)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 8, SJR: 0.497, h-index: 31)
Advances in Imaging and Electron Physics     Full-text available via subscription   (Followers: 2, SJR: 0.396, h-index: 27)
Advances in Immunology     Full-text available via subscription   (Followers: 35, SJR: 4.152, h-index: 85)
Advances in Inorganic Chemistry     Full-text available via subscription   (Followers: 9, SJR: 1.132, h-index: 42)
Advances in Insect Physiology     Full-text available via subscription   (Followers: 3, SJR: 1.274, h-index: 27)
Advances in Integrative Medicine     Hybrid Journal   (Followers: 6)
Advances in Life Course Research     Hybrid Journal   (Followers: 8, SJR: 0.764, h-index: 15)
Advances in Lipobiology     Full-text available via subscription   (Followers: 2)
Advances in Magnetic and Optical Resonance     Full-text available via subscription   (Followers: 9)
Advances in Marine Biology     Full-text available via subscription   (Followers: 15, SJR: 1.645, h-index: 45)
Advances in Mathematics     Full-text available via subscription   (Followers: 10, SJR: 3.261, h-index: 65)
Advances in Medical Sciences     Hybrid Journal   (Followers: 6, SJR: 0.489, h-index: 25)
Advances in Medicinal Chemistry     Full-text available via subscription   (Followers: 5)
Advances in Microbial Physiology     Full-text available via subscription   (Followers: 4, SJR: 1.44, h-index: 51)
Advances in Molecular and Cell Biology     Full-text available via subscription   (Followers: 22)
Advances in Molecular and Cellular Endocrinology     Full-text available via subscription   (Followers: 10)
Advances in Molecular Toxicology     Full-text available via subscription   (Followers: 7, SJR: 0.324, h-index: 8)
Advances in Nanoporous Materials     Full-text available via subscription   (Followers: 4)
Advances in Oncobiology     Full-text available via subscription   (Followers: 3)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 15, SJR: 2.885, h-index: 45)
Advances in Parallel Computing     Full-text available via subscription   (Followers: 7, SJR: 0.148, h-index: 11)
Advances in Parasitology     Full-text available via subscription   (Followers: 7, SJR: 2.37, h-index: 73)
Advances in Pediatrics     Full-text available via subscription   (Followers: 24, SJR: 0.4, h-index: 28)
Advances in Pharmaceutical Sciences     Full-text available via subscription   (Followers: 13)
Advances in Pharmacology     Full-text available via subscription   (Followers: 15, SJR: 1.718, h-index: 58)
Advances in Physical Organic Chemistry     Full-text available via subscription   (Followers: 7, 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: 18)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 19, SJR: 1.5, h-index: 62)
Advances in Psychology     Full-text available via subscription   (Followers: 61)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 5, SJR: 0.478, h-index: 32)
Advances in Radiation Oncology     Open Access  
Advances in Small Animal Medicine and Surgery     Hybrid Journal   (Followers: 2, SJR: 0.1, h-index: 2)
Advances in Space Research     Full-text available via subscription   (Followers: 348, 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: 43, SJR: 2.408, h-index: 94)
Aeolian Research     Hybrid Journal   (Followers: 5, SJR: 0.973, h-index: 22)
Aerospace Science and Technology     Hybrid Journal   (Followers: 317, 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: 408, SJR: 1.385, h-index: 72)
Agri Gene     Hybrid Journal  
Agricultural and Forest Meteorology     Hybrid Journal   (Followers: 15, SJR: 2.18, h-index: 116)
Agricultural Systems     Hybrid Journal   (Followers: 30, SJR: 1.275, h-index: 74)
Agricultural Water Management     Hybrid Journal   (Followers: 39, SJR: 1.546, h-index: 79)
Agriculture and Agricultural Science Procedia     Open Access  
Agriculture and Natural Resources     Open Access   (Followers: 1)
Agriculture, Ecosystems & Environment     Hybrid Journal   (Followers: 54, SJR: 1.879, h-index: 120)
Ain Shams Engineering J.     Open Access   (Followers: 5, SJR: 0.434, h-index: 14)
Air Medical J.     Hybrid Journal   (Followers: 5, SJR: 0.234, h-index: 18)
AKCE Intl. J. of Graphs and Combinatorics     Open Access   (SJR: 0.285, h-index: 3)
Alcohol     Hybrid Journal   (Followers: 9, SJR: 0.922, h-index: 66)
Alcoholism and Drug Addiction     Open Access   (Followers: 8)
Alergologia Polska : Polish J. of Allergology     Full-text available via subscription   (Followers: 1)
Alexandria Engineering J.     Open Access   (Followers: 1, SJR: 0.436, h-index: 12)
Alexandria J. of Medicine     Open Access  
Algal Research     Partially Free   (Followers: 8, SJR: 2.05, h-index: 20)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 3)
Allergologia et Immunopathologia     Full-text available via subscription   (Followers: 1, SJR: 0.46, h-index: 29)
Allergology Intl.     Open Access   (Followers: 4, SJR: 0.776, h-index: 35)
Alpha Omegan     Full-text available via subscription   (SJR: 0.121, h-index: 9)
ALTER - European J. of Disability Research / Revue Européenne de Recherche sur le Handicap     Full-text available via subscription   (Followers: 8, SJR: 0.158, h-index: 9)
Alzheimer's & Dementia     Hybrid Journal   (Followers: 47, SJR: 4.289, h-index: 64)
Alzheimer's & Dementia: Diagnosis, Assessment & Disease Monitoring     Open Access   (Followers: 5)
Alzheimer's & Dementia: Translational Research & Clinical Interventions     Open Access   (Followers: 3)
American Heart J.     Hybrid Journal   (Followers: 48, SJR: 3.157, h-index: 153)
American J. of Cardiology     Hybrid Journal   (Followers: 45, SJR: 2.063, h-index: 186)
American J. of Emergency Medicine     Hybrid Journal   (Followers: 39, SJR: 0.574, h-index: 65)
American J. of Geriatric Pharmacotherapy     Full-text available via subscription   (Followers: 6, SJR: 1.091, h-index: 45)
American J. of Geriatric Psychiatry     Hybrid Journal   (Followers: 16, SJR: 1.653, h-index: 93)
American J. of Human Genetics     Hybrid Journal   (Followers: 31, SJR: 8.769, h-index: 256)
American J. of Infection Control     Hybrid Journal   (Followers: 24, 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: 192, SJR: 2.255, h-index: 171)
American J. of Ophthalmology     Hybrid Journal   (Followers: 56, SJR: 2.803, h-index: 148)
American J. of Ophthalmology Case Reports     Open Access   (Followers: 4)
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: 24, SJR: 0.59, h-index: 45)
American J. of Pathology     Hybrid Journal   (Followers: 26, SJR: 2.653, h-index: 228)
American J. of Preventive Medicine     Hybrid Journal   (Followers: 21, SJR: 2.764, h-index: 154)
American J. of Surgery     Hybrid Journal   (Followers: 34, SJR: 1.286, h-index: 125)
American J. of the Medical Sciences     Hybrid Journal   (Followers: 12, SJR: 0.653, h-index: 70)
Ampersand : An Intl. J. of General and Applied Linguistics     Open Access   (Followers: 5)
Anaerobe     Hybrid Journal   (Followers: 4, SJR: 1.066, h-index: 51)
Anaesthesia & Intensive Care Medicine     Full-text available via subscription   (Followers: 55, SJR: 0.124, h-index: 9)
Anaesthesia Critical Care & Pain Medicine     Full-text available via subscription   (Followers: 9)
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: 2, SJR: 2.577, h-index: 7)
Analytica Chimica Acta     Hybrid Journal   (Followers: 37, SJR: 1.548, h-index: 152)
Analytical Biochemistry     Hybrid Journal   (Followers: 166, SJR: 0.725, h-index: 154)
Analytical Chemistry Research     Open Access   (Followers: 8, SJR: 0.18, h-index: 2)
Analytical Spectroscopy Library     Full-text available via subscription   (Followers: 11)
Anesthésie & Réanimation     Full-text available via subscription   (Followers: 1)
Anesthesiology Clinics     Full-text available via subscription   (Followers: 22, SJR: 0.421, h-index: 40)
Angiología     Full-text available via subscription   (SJR: 0.124, h-index: 9)
Angiologia e Cirurgia Vascular     Open Access  
Animal Behaviour     Hybrid Journal   (Followers: 156, SJR: 1.907, h-index: 126)
Animal Feed Science and Technology     Hybrid Journal   (Followers: 5, SJR: 1.151, h-index: 83)
Animal Reproduction Science     Hybrid Journal   (Followers: 5, SJR: 0.711, h-index: 78)
Annales d'Endocrinologie     Full-text available via subscription   (Followers: 1, SJR: 0.394, h-index: 30)
Annales d'Urologie     Full-text available via subscription  
Annales de Cardiologie et d'Angéiologie     Full-text available via subscription   (SJR: 0.177, h-index: 13)
Annales de Chirurgie de la Main et du Membre Supérieur     Full-text available via subscription  
Annales de Chirurgie Plastique Esthétique     Full-text available via subscription   (Followers: 2, SJR: 0.354, h-index: 22)
Annales de Chirurgie Vasculaire     Full-text available via subscription   (Followers: 1)

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Journal Cover Acta Astronautica
  [SJR: 0.726]   [H-I: 43]   [343 followers]  Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0094-5765
   Published by Elsevier Homepage  [3044 journals]
  • SWEET CubeSat – Water detection and water quality monitoring for the
           21st century
    • Authors: Kelly Antonini; Martin Langer; Ahmed Farid; Ulrich Walter
      Pages: 10 - 17
      Abstract: Publication date: November 2017
      Source:Acta Astronautica, Volume 140
      Author(s): Kelly Antonini, Martin Langer, Ahmed Farid, Ulrich Walter
      Water scarcity and contamination of clean water have been identified as major challenges of the 21st century, in particular for developing countries. According to the International Water Management Institute, about 30% of the world's population does not have reliable access to clean water. Consequently, contaminated water contributes to the death of about 3 million people every year, mostly children. Access to potable water has been proven to boost education, equality and health, reduce hunger, as well as help the economy of the developing world. Currently used in-situ water monitoring techniques are sparse, and often difficult to execute. Space-based instruments will help to overcome these challenges by providing means for water level and water quality monitoring of medium-to-large sweet (fresh) water reservoirs. Data from hyperspectral imaging instruments on past and present governmental missions, such as Envisat and Aqua, has been used for this purpose. However, the high cost of large multi-purpose space vessels, and the lack of dedicated missions limits the continuous monitoring of inland and coastal water quality. The proposed CubeSat mission SWEET (Sweet Water Earth Education Technologies) will try to fill this gap. The SWEET concept is a joint effort between the Technical University of Munich, the German Space Operations Center and the African Steering Committee of the IAF. By using a novel Fabry-Perot interferometer-based hyperspectral imager, the mission will deliver critical data directly to national water resource centers in Africa with an unmatched cost per pixel ratio and high temporal resolution. Additionally, SWEET will incorporate education of students in CubeSat design and water management. Although the aim of the mission is to deliver local water quality and water level data to African countries, further coverage could be achieved with subsequent satellites. Finally, a constellation of SWEET-like CubeSats would extend the coverage to the whole planet, delivering daily data to ensure reliable access to clean water for millions of people worldwide.

      PubDate: 2017-08-27T14:57:51Z
      DOI: 10.1016/j.actaastro.2017.07.046
      Issue No: Vol. 140 (2017)
  • Mechanism of shock train rapid motion induced by variation of attack angle
    • Authors: Kejing Xu; Juntao Chang; Weixing Zhou; Daren Yu
      Pages: 18 - 26
      Abstract: Publication date: November 2017
      Source:Acta Astronautica, Volume 140
      Author(s): Kejing Xu, Juntao Chang, Weixing Zhou, Daren Yu
      Numerical simulation was conducted to study the effect of attack angle variation on the quasi-steady motion characteristics of shock train leading edge. Simulation results indicate the motion of shock train has jumping feature, which is mainly caused by the strength changing of the local flow separation. During the process of attack angle decreasing, the reflection points of background wave move downstream, and the one of which approaches the separation zone of shock train. Thus a rapid forward movement is induced by the increasing local adverse pressure gradients. In attack angle increasing case, shock train is not moving back continuously but can be temporarily stabilized at the front part of the reflection point, because of the local adverse pressure gradient that formed by background waves. Once the refection point moves forward and surmounts leading edge of shock train, the pressure boost from background wave to the separation zone is lost, and a suddenly backward jumping will occur.

      PubDate: 2017-08-27T14:57:51Z
      DOI: 10.1016/j.actaastro.2017.08.009
      Issue No: Vol. 140 (2017)
  • Accurate analytical periodic solution of the elliptical Kepler equation
           using the Adomian decomposition method
    • Authors: Aisha Alshaery; Abdelhalim Ebaid
      Pages: 27 - 33
      Abstract: Publication date: November 2017
      Source:Acta Astronautica, Volume 140
      Author(s): Aisha Alshaery, Abdelhalim Ebaid
      Kepler's equation is one of the fundamental equations in orbital mechanics. It is a transcendental equation in terms of the eccentric anomaly of a planet which orbits the Sun. Determining the position of a planet in its orbit around the Sun at a given time depends upon the solution of Kepler's equation, which we will solve in this paper by the Adomian decomposition method (ADM). Several properties of the periodicity of the obtained approximate solutions have been proved in lemmas. Our calculations demonstrated a rapid convergence of the obtained approximate solutions which are displayed in tables and graphs. Also, it has been shown in this paper that only a few terms of the Adomian decomposition series are sufficient to achieve highly accurate numerical results for any number of revolutions of the Earth around the Sun as a consequence of the periodicity property. Numerically, the four-term approximate solution coincides with the Bessel-Fourier series solution in the literature up to seven decimal places at some values of the time parameter and nine decimal places at other values. Moreover, the absolute error approaches zero using the nine term approximate Adomian solution. In addition, the approximate Adomian solutions for the eccentric anomaly have been used to show the convergence of the approximate radial distances of the Earth from the Sun for any number of revolutions. The minimal distance (perihelion) and maximal distance (aphelion) approach 147 million kilometers and 152.505 million kilometers, respectively, and these coincide with the well known results in astronomical physics. Therefore, the Adomian decomposition method is validated as an effective tool to solve Kepler's equation for elliptical orbits.

      PubDate: 2017-08-27T14:57:51Z
      DOI: 10.1016/j.actaastro.2017.07.034
      Issue No: Vol. 140 (2017)
  • Orbit-attitude coupled motion around small bodies: Sun-synchronous orbits
           with Sun-tracking attitude motion
    • Authors: Shota Kikuchi; Kathleen C. Howell; Yuichi Tsuda; Jun'ichiro Kawaguchi
      Pages: 34 - 48
      Abstract: Publication date: November 2017
      Source:Acta Astronautica, Volume 140
      Author(s): Shota Kikuchi, Kathleen C. Howell, Yuichi Tsuda, Jun'ichiro Kawaguchi
      The motion of a spacecraft in proximity to a small body is significantly perturbed due to its irregular gravity field and solar radiation pressure. In such a strongly perturbed environment, the coupling effect of the orbital and attitude motions exerts a large influence that cannot be neglected. However, natural orbit-attitude coupled dynamics around small bodies that are stationary in both orbital and attitude motions have yet to be observed. The present study therefore investigates natural coupled motion that involves both a Sun-synchronous orbit and Sun-tracking attitude motion. This orbit-attitude coupled motion enables a spacecraft to maintain its orbital geometry and attitude state with respect to the Sun without requiring active control. Therefore, the proposed method can reduce the use of an orbit and attitude control system. This paper first presents analytical conditions to achieve Sun-synchronous orbits and Sun-tracking attitude motion. These analytical solutions are then numerically propagated based on non-linear coupled orbit-attitude equations of motion. Consequently, the possibility of implementing Sun-synchronous orbits with Sun-tracking attitude motion is demonstrated.

      PubDate: 2017-08-27T14:57:51Z
      DOI: 10.1016/j.actaastro.2017.07.043
      Issue No: Vol. 140 (2017)
  • Resonantly interacting non-linear waves in a van der Waals gas
    • Authors: Triloki Nath; R.K. Gupta; L.P. Singh
      Pages: 91 - 95
      Abstract: Publication date: November 2017
      Source:Acta Astronautica, Volume 140
      Author(s): Triloki Nath, R.K. Gupta, L.P. Singh
      The present paper uses the method of multiple time scales to derive the asymptotic solution of system of one-dimensional quasilinear hyperbolic equations for the generalized geometry in van der Waals gas. The transport equation for the amplitude of resonantly interacting high frequency waves propagating into non-ideal gas is derived. Further, we discuss the cases when the initial data for the wave amplitude is of 2 π periodicity. The evolutionary behavior of non-resonant wave modes culminating into shock wave and its location are examined in van der Waals fluid.

      PubDate: 2017-08-27T14:57:51Z
      DOI: 10.1016/j.actaastro.2017.08.010
      Issue No: Vol. 140 (2017)
  • VZLUSAT-1: Nanosatellite with miniature lobster eye X-ray telescope and
           qualification of the radiation shielding composite for space application
    • Authors: Martin Urban; Ondrej Nentvich; Veronika Stehlikova; Tomas Baca; Vladimir Daniel; Rene Hudec
      Pages: 96 - 104
      Abstract: Publication date: November 2017
      Source:Acta Astronautica, Volume 140
      Author(s): Martin Urban, Ondrej Nentvich, Veronika Stehlikova, Tomas Baca, Vladimir Daniel, Rene Hudec
      In the upcoming generation of small satellites there is a great potential for testing new sensors, processes and technologies for space and also for the creation of large in situ sensor networks. It plays a significant role in the more detailed examination, modelling and evaluation of the orbital environment. Scientific payloads based on the CubeSat technology are also feasible and the miniature X-ray telescope described in this paper may serve as an example. One of these small satellites from CubeSat family is a Czech CubeSat VZLUSAT-1, which is going to be launched during QB50 mission in 2017. This satellite has dimensions of 100 mm × 100 mm × 230 mm. The VZLUSAT-1 has three main payloads. The tested Radiation Hardened Composites Housing (RHCH) has ambitions to be used as a structural and shielding material to protect electronic devices in space or for constructions of future manned and unmanned spacecraft as well as Moon or Martian habitats. The novel miniaturized X-ray telescope with a Lobster Eye (LE) optics represents an example of CubeSat's scientific payload. The telescope has a wide field of view and such systems may be essential in detecting the X-ray sources of various physical origin. VZLUSAT-1 also carries the FIPEX payload which measures the molecular and atomic oxygen density among part of the satellite group in QB50 mission. The VZLUSAT-1 is one of the constellation in the QB50 mission that create a measuring network around the Earth and provide multipoint, in-situ measurements of the atmosphere.

      PubDate: 2017-08-27T14:57:51Z
      DOI: 10.1016/j.actaastro.2017.08.004
      Issue No: Vol. 140 (2017)
  • Coronal Mass Ejection early-warning mission by solar-photon sailcraft
    • Authors: Giovanni Vulpetti; Christian Circi; Tommaso Pino
      Pages: 113 - 125
      Abstract: Publication date: November 2017
      Source:Acta Astronautica, Volume 140
      Author(s): Giovanni Vulpetti, Christian Circi, Tommaso Pino
      A preliminary investigation of the early warning of solar storms caused by Coronal Mass Ejection has been carried out. A long warning time could be obtained with a sailcraft synchronous with the Earth-Moon barycenter, and stationed well below the L1 point. In this paper, the theory of heliocentric synchronous sailcraft is set up, its perturbed orbit is analyzed, and a potential solution capable of providing an annual synchrony is carried out. A simple analysis of the response from a low-mass electrochromic actuator for the realization of station-keeping attitude maneuvers is put forwards, and an example of propellantless re-orientation maneuver is studied.

      PubDate: 2017-08-30T15:01:03Z
      DOI: 10.1016/j.actaastro.2017.07.042
      Issue No: Vol. 140 (2017)
  • Investigation of flameholding characteristics in a kerosene-fueled
           scramjet combustor with tandem dual-cavity
    • Authors: Yu-hang Wang; Wen-yan Song; De-yong Shi
      Pages: 126 - 132
      Abstract: Publication date: November 2017
      Source:Acta Astronautica, Volume 140
      Author(s): Yu-hang Wang, Wen-yan Song, De-yong Shi
      The flameholding characteristics in a kerosene-fueled scramjet combustor with a tandem dual-cavity were investigated experimentally under various inlet stagnation pressure conditions. Flame stabilization locations were judged by the pressure distributions and flame luminescence images. The results show that at lower and higher equivalence ratios, the flame was stabilized in the downstream and upstream cavities, respectively. While at intermediate range of equivalence ratio the flame was oscillating between the two cavities. The inlet stagnation pressure has a significant impact on the flameholding characteristics by affecting the relative pressure rise and the flame speed. The transition of flame stabilization location can occur in a higher local flow Mach number in the case of the higher inlet stagnation pressure.

      PubDate: 2017-08-30T15:01:03Z
      DOI: 10.1016/j.actaastro.2017.08.014
      Issue No: Vol. 140 (2017)
  • Development of solid-gas equilibrium propulsion system for small
    • Authors: Toshihiro Chujo; Osamu Mori; Yuki Kubo
      Pages: 133 - 139
      Abstract: Publication date: November 2017
      Source:Acta Astronautica, Volume 140
      Author(s): Toshihiro Chujo, Osamu Mori, Yuki Kubo
      A phase equilibrium propulsion system is a kind of cold-gas jet in which the phase equilibrium state of the fuel is maintained in a tank and its vapor is ejected when a valve is opened. One such example is a gas-liquid equilibrium propulsion system that uses liquefied gas as fuel. This system was mounted on the IKAROS solar sail and has been demonstrated in orbit. The system has a higher storage efficiency and a lighter configuration than a high-pressure cold-gas jet because the vapor pressure is lower, and is suitable for small spacecraft. However, the system requires a gas-liquid separation device in order to avoid leakage of the liquid, which makes the system complex. As another example of a phase equilibrium propulsion system, we introduce a solid-gas equilibrium propulsion system, which uses a sublimable substance as fuel and ejects its vapor. This system has an even lower vapor pressure and does not require such a separation device, instead requiring only a filter to keep the solid inside the tank. Moreover, the system is much simpler and lighter, making it more suitable for small spacecraft, especially CubeSat-class spacecraft, and the low thrust of the system allows spacecraft motion to be controlled precisely. In addition, the thrust level can be controlled by controlling the temperature of the fuel, which changes the vapor pressure. The present paper introduces the concept of the proposed system, and describes ejection experiments and its evaluation. The basic function of the proposed system is demonstrated in order to verify its usefulness.

      PubDate: 2017-08-30T15:01:03Z
      DOI: 10.1016/j.actaastro.2017.07.050
      Issue No: Vol. 140 (2017)
  • The detection of cold dark matter with the Mössbauer effect in earth
    • Authors: Friedwardt Winterberg
      Pages: 140 - 141
      Abstract: Publication date: November 2017
      Source:Acta Astronautica, Volume 140
      Author(s): Friedwardt Winterberg
      It is proposed that cold dark matter (CDM) consists of gravitationally interacting Planck mass particles. With the weakness of the gravitational interaction compensated by the large Planck mass m ≅ 10 − 5 g , it becomes possible to detect Planck mass particles by their classical gravitational scattering on small macroscopic particles provided the impact velocity is small. While Planck mass particles falling towards the sun are expected to have a velocity of ≅ 300 k m s , this would not be the case for by the gravitational field of the Earth entrapped Planck mass particles moving with same velocity as an earth satellite in the same orbit. For this reason, the collision of a Planck mass particle with a macroscopic particle in an Earth satellite might be detected by a small increment in the velocity of the macroscopic particle with the Mössbauer effect.

      PubDate: 2017-08-30T15:01:03Z
      DOI: 10.1016/j.actaastro.2017.08.006
      Issue No: Vol. 140 (2017)
  • Sliding mode predictive guidance for terminal rendezvous in eccentric
    • Authors: Seyed Aliakbar Kasaeian; Nima Assadian; Masoud Ebrahimi
      Pages: 142 - 155
      Abstract: Publication date: November 2017
      Source:Acta Astronautica, Volume 140
      Author(s): Seyed Aliakbar Kasaeian, Nima Assadian, Masoud Ebrahimi
      This paper presents a robust guidance algorithm for a chaser spacecraft to rendezvous with a target spacecraft in Earth orbit. The basis of the proposed guidance method is finding an appropriate set of states as close as possible to the current states that would lead the spacecraft to the target in the desired mission time. In order to provide the prediction of states, the relative dynamics equations of motion are solved analytically for the chaser spacecraft rendezvous considering constant acceleration. Although the equations are solved for rendezvous with circular orbit target, it is shown by several simulations that the proposed guidance algorithm is applicable in perturbed elliptical orbits rendezvous as well. The sliding mode method as a robust nonlinear method is utilized as the steering law. The robust steering law tracks the desired states computed by the predictive guidance method. The Lyapunov stability method proves the asymptotic stability of the integrated guidance and steering laws. Because the proposed closed-loop guidance is simple and computationally easy, it is suitable for implementation in real-time applications. Some numerical simulations are conducted to show the performance of the proposed guidance method in different conditions. It is illustrated that compared with other steering laws, the fuel consumption is reduced utilizing the proposed guidance approach. The results reveal that the sliding mode guarantees the tracking of the required states and minimum final errors even in the presence of uncertainties and disturbances.

      PubDate: 2017-08-30T15:01:03Z
      DOI: 10.1016/j.actaastro.2017.08.012
      Issue No: Vol. 140 (2017)
  • Ascent phase trajectory optimization for vehicle with multi-combined cycle
           engine based on improved particle swarm optimization
    • Authors: Hongyu Zhou; Xiaogang Wang; Yuliang Bai; Naigang Cui
      Pages: 156 - 165
      Abstract: Publication date: November 2017
      Source:Acta Astronautica, Volume 140
      Author(s): Hongyu Zhou, Xiaogang Wang, Yuliang Bai, Naigang Cui
      An improved particle swarm optimization (IPSO) algorithm is proposed to optimize the ascent phase trajectory for vehicle with multi-combined cycle engine. Aerodynamic and thrust models are formulated in couple with flying states and environment. Conventional PSO has advantages in solving complicated optimization problems but has troubles in constraints handling and premature convergence preventing. To handle constraints, a modification in the fitness function of infeasible particles is executed based on the constraints violation and a comparation is executed to choose the better particle according to the fitness. To prevent premature, a diminishing number of particles are chosen to be mutated on the velocity by random times and directions. The ascent trajectory is divided into sub-phases according to engine modes. Different constraints, control parameters and engine models are considered in each sub-phase. Though the proposed algorithm is straightforward in comprehension and implementation, the numerical examples demonstrate that the algorithm has better performance than other PSO variants. In comparation with the commercial software GPOPS, the performance index of IPSO is almost the same as GPOPS but the results are less oscillating and dependent on initial values.

      PubDate: 2017-08-30T15:01:03Z
      DOI: 10.1016/j.actaastro.2017.08.024
      Issue No: Vol. 140 (2017)
  • A new star tracker concept for satellite attitude determination based on a
           multi-purpose panoramic camera
    • Authors: Roberto Opromolla; Giancarmine Fasano; Giancarlo Rufino; Michele Grassi; Claudio Pernechele; Cesare Dionisio
      Pages: 166 - 175
      Abstract: Publication date: November 2017
      Source:Acta Astronautica, Volume 140
      Author(s): Roberto Opromolla, Giancarmine Fasano, Giancarlo Rufino, Michele Grassi, Claudio Pernechele, Cesare Dionisio
      This paper presents an innovative algorithm developed for attitude determination of a space platform. The algorithm exploits images taken from a multi-purpose panoramic camera equipped with hyper-hemispheric lens and used as star tracker. The sensor architecture is also original since state-of-the-art star trackers accurately image as many stars as possible within a narrow- or medium-size field-of-view, while the considered sensor observes an extremely large portion of the celestial sphere but its observation capabilities are limited by the features of the optical system. The proposed original approach combines algorithmic concepts, like template matching and point cloud registration, inherited from the computer vision and robotic research fields, to carry out star identification. The final aim is to provide a robust and reliable initial attitude solution (lost-in-space mode), with a satisfactory accuracy level in view of the multi-purpose functionality of the sensor and considering its limitations in terms of resolution and sensitivity. Performance evaluation is carried out within a simulation environment in which the panoramic camera operation is realistically reproduced, including perturbations in the imaged star pattern. Results show that the presented algorithm is able to estimate attitude with accuracy better than 1° with a success rate around 98% evaluated by densely covering the entire space of the parameters representing the camera pointing in the inertial space.

      PubDate: 2017-08-30T15:01:03Z
      DOI: 10.1016/j.actaastro.2017.08.020
      Issue No: Vol. 140 (2017)
  • Investigations on the influences of elastic foundations on the
           aerothermoelastic flutter and thermal buckling properties of lattice
           sandwich panels in supersonic airflow
    • Authors: Yu-Yang Chai; Zhi-Guang Song; Feng-Ming Li
      Pages: 176 - 189
      Abstract: Publication date: November 2017
      Source:Acta Astronautica, Volume 140
      Author(s): Yu-Yang Chai, Zhi-Guang Song, Feng-Ming Li
      The lattice sandwich panels supported on elastic mediums are often applied in the construction of aerospace structures because of the low specific weight, excellent bending rigidity and outstanding vibration properties. This elastic medium can be any spring materials including damping tapes or heat shields which are attached to one side of the sandwich panel. Therefore, in this paper, aerothermoelastic flutter and thermal buckling characteristics of sandwich panels with the pyramidal lattice core resting on elastic foundations in supersonic airflow are studied. The influences of geometrical parameters and elastic foundation on the panel flutter and thermal buckling of the structures are analyzed in detail. In the structural modeling, the first-order shear deformation theory is applied, and the effective material properties of the lattice core are used. The aerodynamic pressure is evaluated by the supersonic piston theory. Hamilton's principle and the assumed modes method are applied to formulate the equation of motion. The highlight point of this investigation is that an effective thermal buckling suppression method utilizing the elastic foundation is proposed, based on which the thermal buckling of the structure can be completely eliminated with the natural frequencies remaining unchanged when the shearing layer parameter is equal to the thermal load. Through the numerical results, the influences of the elastic foundation, aspect ratio, core-to-facesheet thickness ratio, and inclination angle of the core truss on the aerothermoelastic behaviors of the lattice sandwich panel are analyzed, and the thermal buckling elimination effects are also examined.

      PubDate: 2017-08-30T15:01:03Z
      DOI: 10.1016/j.actaastro.2017.08.016
      Issue No: Vol. 140 (2017)
  • Glucocorticoid: A potential role in microgravity-induced bone loss
    • Authors: Jiancheng Yang; Zhouqi Yang; Wenbin Li; Yanru Xue; Huiyun Xu; Jingbao Li; Peng Shang
      Pages: 206 - 212
      Abstract: Publication date: November 2017
      Source:Acta Astronautica, Volume 140
      Author(s): Jiancheng Yang, Zhouqi Yang, Wenbin Li, Yanru Xue, Huiyun Xu, Jingbao Li, Peng Shang
      Exposure of animals and humans to conditions of microgravity, including actual spaceflight and simulated microgravity, results in numerous negative alterations to bone structure and mechanical properties. Although there are abundant researches on bone loss in microgravity, the explicit mechanism is not completely understood. At present, it is widely accepted that the absence of mechanical stimulus plays a predominant role in bone homeostasis disorders in conditions of weightlessness. However, aside from mechanical unloading, nonmechanical factors such as various hormones, cytokines, dietary nutrition, etc. are important as well in microgravity induced bone loss. The stress-induced increase in endogenous glucocorticoid (GC) levels is inevitable in microgravity environments. Moreover, it is well known that GCs have a detrimental effect to bone health at excess concentrations. Therefore, GC plays a potential role in microgravity-induced bone loss. This review summarizeds several studies and their prospective solutions to this hypothesis.

      PubDate: 2017-09-06T14:54:01Z
      DOI: 10.1016/j.actaastro.2017.08.007
      Issue No: Vol. 140 (2017)
  • Optimal sensor placement for deployable antenna module health monitoring
           in SSPS using genetic algorithm
    • Authors: Chen Yang; Xuepan Zhang; Xiaoqi Huang; ZhengAi Cheng; Xinghua Zhang; Xinbin Hou
      Pages: 213 - 224
      Abstract: Publication date: November 2017
      Source:Acta Astronautica, Volume 140
      Author(s): Chen Yang, Xuepan Zhang, Xiaoqi Huang, ZhengAi Cheng, Xinghua Zhang, Xinbin Hou
      The concept of space solar power satellite (SSPS) is an advanced system for collecting solar energy in space and transmitting it wirelessly to earth. However, due to the long service life, in-orbit damage may occur in the structural system of SSPS. Therefore, sensor placement layouts for structural health monitoring should be firstly considered in this concept. In this paper, based on genetic algorithm, an optimal sensor placement method for deployable antenna module health monitoring in SSPS is proposed. According to the characteristics of the deployable antenna module, the designs of sensor placement are listed. Furthermore, based on effective independence method and effective interval index, a combined fitness function is defined to maximize linear independence in targeted modes while simultaneously avoiding redundant information at nearby positions. In addition, by considering the reliability of sensors located at deployable mechanisms, another fitness function is constituted. Moreover, the solution process of optimal sensor placement by using genetic algorithm is clearly demonstrated. At last, a numerical example about the sensor placement layout in a deployable antenna module of SSPS is presented, which by synthetically considering all the above mentioned performances. All results can illustrate the effectiveness and feasibility of the proposed sensor placement method in SSPS.

      PubDate: 2017-09-06T14:54:01Z
      DOI: 10.1016/j.actaastro.2017.08.025
      Issue No: Vol. 140 (2017)
  • Soft landing on an irregular shape asteroid using Multiple-Horizon
           Multiple-Model Predictive Control
    • Authors: MohammadAmin AlandiHallaj; Nima Assadian
      Pages: 225 - 234
      Abstract: Publication date: November 2017
      Source:Acta Astronautica, Volume 140
      Author(s): MohammadAmin AlandiHallaj, Nima Assadian
      This study has introduced a predictive framework including a heuristic guidance law named Predictive Path Planning and Multiple-Horizon Multiple-Model Predictive Control as the control scheme for soft landing on an irregular-shaped asteroid. The dynamical model of spacecraft trajectory around an asteroid is introduced. The reference-landing trajectory is generated using Predictive Path Planning. Not only does the presented guidance law satisfy the collision avoidance constraint, but also guarantees the landing accuracy and vertical landing condition. Multiple-Horizon Multiple-Model Predictive Control is employed to make the spacecraft track the designed reference trajectory. The proposed control approach, which is a Model Predictive Control scheme, utilizes several prediction models instead of one. In this manner, it heritages the advantages of optimality and tackling external disturbances and model uncertainties from classical Model Predictive Control and at the same time has the advantage of lower computational burden than Model Predictive Control. Finally, numerical simulations are carried out to demonstrate the feasibility and effectiveness of the proposed control approach in achieving the desired conditions in presence of uncertainties and disturbances.

      PubDate: 2017-09-06T14:54:01Z
      DOI: 10.1016/j.actaastro.2017.08.019
      Issue No: Vol. 140 (2017)
  • A Cartesian relative motion approach to optimal formation flight using
           Lorentz forces and impulsive thrusting
    • Authors: Behrad Vatankhahghadim; Christopher J. Damaren
      Pages: 255 - 263
      Abstract: Publication date: November 2017
      Source:Acta Astronautica, Volume 140
      Author(s): Behrad Vatankhahghadim, Christopher J. Damaren
      Hybrid combination of Lorentz forces and impulsive thrusts, provided by modulating spacecraft's electrostatic charge and propellant usage, respectively, is proposed for formation flight applications. A hybrid linear quadratic regulator, previously proposed in another work using a differential orbital elements-based model, is reconsidered for a Cartesian coordinates-based description of the spacecraft's relative states. In addition, the effects of adopting circular versus elliptic reference solutions on the performance of the controller are studied. Numerical simulation results are provided to demonstrate the functionality of the proposed controller in the presence of J 2 perturbations, and to illustrate the improvements gained by assuming an elliptic reference and incorporating auxiliary impulsive thrusts.

      PubDate: 2017-09-06T14:54:01Z
      DOI: 10.1016/j.actaastro.2017.08.023
      Issue No: Vol. 140 (2017)
  • Adaptive robust control with input shaping technology for solar array
           drive system
    • Authors: Tong Zhou; Hong Guo; Jinquan Xu; Chuanchuan Lin
      Pages: 264 - 272
      Abstract: Publication date: November 2017
      Source:Acta Astronautica, Volume 140
      Author(s): Tong Zhou, Hong Guo, Jinquan Xu, Chuanchuan Lin
      In this paper, the angular position control problem of solar array drive system is considered. The system contains uncertainty due to parametric inaccuracy and external disturbance torque. Furthermore, the system is flexible, which may cause the flexible vibration. We propose an input shaping approach based on the reference model, which is able to suppress the flexible vibration by designing the command trajectory. To improve the angular position control performance, an adaptive robust control is proposed, which can guarantee the uniform boundedness and uniform ultimate boundedness of the system, regardless of the uncertainty. The simulation shows that the proposed controller is able to guarantee the system performance and suppress the flexible vibration even under arbitrary uncertainty.

      PubDate: 2017-09-06T14:54:01Z
      DOI: 10.1016/j.actaastro.2017.08.031
      Issue No: Vol. 140 (2017)
  • From outer space to Earth—The social significance of isolated and
           confined environment research in human space exploration
    • Authors: Koji Tachibana; Shoichi Tachibana; Natsuhiko Inoue
      Pages: 273 - 283
      Abstract: Publication date: November 2017
      Source:Acta Astronautica, Volume 140
      Author(s): Koji Tachibana, Shoichi Tachibana, Natsuhiko Inoue
      Human space exploration requires massive budgets every fiscal year. Especially under severe financial constraint conditions, governments are forced to justify to society why spending so much tax revenue for human space exploration is worth the cost. The value of human space exploration might be estimated in many ways, but its social significance and cost-effectiveness are two key ways to gauge that worth. Since these measures should be applied country by country because sociopolitical conditions differ in each country and must be taken into consideration, the study on the social significance of human space exploration must take the coloration of a case-study. This paper, focusing on the case of Japan with surveying Japanese literary and national documents as well as taking its sociopolitical conditions into account, examines the social significance of human space exploration. First, we give an overview of the circumstances surrounding Japan's human space exploration program. Derived from the statements of such relevant parties as scholars, journalists, policy makers, and astronauts, this overview indicates that the main concerns about human space exploration in Japan are its social significance and cost-effectiveness (Section 1). Next, an overview of behavioral science—an essential field for human space exploration (referred to in this paper as space behavioral science) that provides support for astronauts—is presented from the perspective of stress research in isolated and confined environments (Section 2). We then give two examples of where such knowledge from space behavioral science research has been applied to terrestrial isolated and confined environments. One is JAXA’s support in 2009 for people who were vulnerable to infection by a new strain of flu and accordingly placed in an isolated and confined facility under the Infectious Disease Law and the Quarantine Law. The other is NASA's support in 2010 for Chilean mine workers who were trapped 700 m underground after a mining accident (Section 3). Based on these case studies, we illustrate the further social utility of such knowledge through a discussion of potential applications in other situations in Japan. Focusing on Japan for its geographical and social features in being an earthquake-prone archipelago and having the world's preeminent aging society, we show that refugees living in evacuation centers and people in an elderly-elderly homecare situation pose socially problematic situations specific to Japan. We then argue that space behavioral scientific knowledge can be applied to support people under these and other isolated and confined environments in various ways (Section 4). Finally, we demonstrate that such an application can be understood as an ethical contribution to Japanese society and that this contribution can be embedded in Japan's space policy (Section 5). We conclude that human space exploration can be a socially significant and cost-effective endeavor that is worthy of tax revenue expenditures because space behavioral science is highly likely to provide unique and useful knowledge to help address various social problems concerning terrestrial isolated and confined environments and support people in sufferings there.

      PubDate: 2017-09-06T14:54:01Z
      DOI: 10.1016/j.actaastro.2017.08.015
      Issue No: Vol. 140 (2017)
  • Research on shock wave characteristics in the isolator of central strut
           rocket-based combined cycle engine under Ma5.5
    • Authors: Xianggeng Wei; Rui Xue; Fei Qin; Chunbo Hu; Guoqiang He
      Pages: 284 - 292
      Abstract: Publication date: November 2017
      Source:Acta Astronautica, Volume 140
      Author(s): Xianggeng Wei, Rui Xue, Fei Qin, Chunbo Hu, Guoqiang He
      A numerical calculation of shock wave characteristics in the isolator of central strut rocket-based combined cycle (RBCC) engine fueled by kerosene was carried out in this paper. A 3D numerical model was established by the DES method. The kerosene chemical kinetic model used the 9-component and 12-step simplified mechanism model. Effects of fuel equivalence ratio, inflow total temperature and central strut rocket on-off on shock wave characteristics were studied under Ma5.5. Results demonstrated that with the increase of equivalence ratio, the leading shock wave moves toward upstream, accompanied with higher possibility of the inlet unstart. However, the leading shock wave moves toward downstream as the inflow total temperature rises. After the central strut rocket is closed, the leading shock wave moves toward downstream, which can reduce risks of the inlet unstart. State of the shear layer formed by the strut rocket jet flow and inflow can influence the shock train structure significantly.

      PubDate: 2017-09-06T14:54:01Z
      DOI: 10.1016/j.actaastro.2017.08.013
      Issue No: Vol. 140 (2017)
  • Statistical multi-criteria evaluation of non-nuclear asteroid deflection
    • Authors: Nicolas Thiry; Massimiliano Vasile
      Pages: 293 - 307
      Abstract: Publication date: November 2017
      Source:Acta Astronautica, Volume 140
      Author(s): Nicolas Thiry, Massimiliano Vasile
      In this paper we assess and compare the effectiveness of four classes of non-nuclear asteroid deflection methods applied to a wide range of virtual collision scenarios. We consider the kinetic impactor, laser ablation, the ion beaming technique and two variants of the gravity tractor. A simple but realistic model of each deflection method was integrated within a systematic approach to size the spacecraft and predict the achievable deflection for a given mission and a given maximum mass at launch. A sample of 100 synthetic asteroids was then created from the current distribution of NEAs and global optimisation methods were used to identify the optimal solution in each case according to two criteria: the minimum duration between the departure date and the time of virtual impact required to deflect the NEA by more than two Earth radii and the maximum miss-distance achieved within a total duration of 10 years. Our results provide an interesting insight into the range of applicability of individual deflection methods and argue the need to develop multiple methods in parallel for a global mitigation of all possible threats.

      PubDate: 2017-09-06T14:54:01Z
      DOI: 10.1016/j.actaastro.2017.08.021
      Issue No: Vol. 140 (2017)
  • A hybrid online scheduling mechanism with revision and progressive
           techniques for autonomous Earth observation satellite
    • Authors: Guoliang Li; Lining Xing; Yingwu Chen
      Pages: 308 - 321
      Abstract: Publication date: November 2017
      Source:Acta Astronautica, Volume 140
      Author(s): Guoliang Li, Lining Xing, Yingwu Chen
      The autonomicity of self-scheduling on Earth observation satellite and the increasing scale of satellite network attract much attention from researchers in the last decades. In reality, the limited onboard computational resource presents challenge for the online scheduling algorithm. This study considered online scheduling problem for a single autonomous Earth observation satellite within satellite network environment. It especially addressed that the urgent tasks arrive stochastically during the scheduling horizon. We described the problem and proposed a hybrid online scheduling mechanism with revision and progressive techniques to solve this problem. The mechanism includes two decision policies, a when-to-schedule policy combining periodic scheduling and critical cumulative number-based event-driven rescheduling, and a how-to-schedule policy combining progressive and revision approaches to accommodate two categories of task: normal tasks and urgent tasks. Thus, we developed two heuristic (re)scheduling algorithms and compared them with other generally used techniques. Computational experiments indicated that the into-scheduling percentage of urgent tasks in the proposed mechanism is much higher than that in periodic scheduling mechanism, and the specific performance is highly dependent on some mechanism-relevant and task-relevant factors. For the online scheduling, the modified weighted shortest imaging time first and dynamic profit system benefit heuristics outperformed the others on total profit and the percentage of successfully scheduled urgent tasks.

      PubDate: 2017-09-11T12:43:52Z
      DOI: 10.1016/j.actaastro.2017.08.011
      Issue No: Vol. 140 (2017)
  • Gravitational force and torque on a solar power satellite considering the
           structural flexibility
    • Authors: Yi Zhao; Jingrui Zhang; Yao Zhang; Jun Zhang; Quan Hu
      Pages: 322 - 337
      Abstract: Publication date: November 2017
      Source:Acta Astronautica, Volume 140
      Author(s): Yi Zhao, Jingrui Zhang, Yao Zhang, Jun Zhang, Quan Hu
      The solar power satellites (SPS) are designed to collect the constant solar energy and beam it to Earth. They are traditionally large in scale and flexible in structure. In order to obtain an accurate model of such system, the analytical expressions of the gravitational force, gravity gradient torque and modal force are investigated. They are expanded to the fourth order in a Taylor series with the elastic displacements considered. It is assumed that the deformation of the structure is relatively small compared with its characteristic length, so that the assumed mode method is applicable. The high-order moments of inertia and flexibility coefficients are presented. The comprehensive dynamics of a large flexible SPS and its orbital, attitude and vibration evolutions with different order gravitational forces, gravity gradient torques and modal forces in geosynchronous Earth orbit are performed. Numerical simulations show that an accurate representation of the SPS′ dynamic characteristics requires the retention of the higher moments of inertia and flexibility. Perturbations of orbit, attitude and vibration can be retained to the 1-2nd order gravitational forces, the 1-2nd order gravity gradient torques and the 1-2nd order modal forces for a large flexible SPS in geosynchronous Earth orbit.

      PubDate: 2017-09-11T12:43:52Z
      DOI: 10.1016/j.actaastro.2017.08.029
      Issue No: Vol. 140 (2017)
  • Non-Fourier heat conduction and phase transition in laser ablation of
           polytetrafluoroethylene (PTFE)
    • Authors: Yu Zhang; Daixian Zhang; Jianjun Wu; Jian Li; Zhaofu He
      Pages: 338 - 350
      Abstract: Publication date: November 2017
      Source:Acta Astronautica, Volume 140
      Author(s): Yu Zhang, Daixian Zhang, Jianjun Wu, Jian Li, Zhaofu He
      The phase transition in heat conduction of polytetrafluoroethylene-like polymers was investigated and applied in many fields of science and engineering. Considering more details including internal absorption of laser radiation, reflectivity of material and non-Fourier effect etc., the combined heat conduction and phase transition in laser ablation of polytetrafluoroethylene were modeled and investigated numerically. The thermal and mechanic issues in laser ablation were illustrated and analyzed. Especially, the phenomenon of temperature discontinuity formed in the combined phase transition and non-Fourier heat conduction was discussed. Comparisons of target temperature profiles between Fourier and non-Fourier heat conduction in melting process were implemented. It was indicated that the effect of non-Fourier plays an important role in the temperature evolvement. The effect of laser fluence was proven to be significant and the thermal wave propagation was independent on the laser intensity for the non-Fourier heat conduction. Besides, the effect of absorption coefficients on temperature evolvements was studied. For different ranges of absorption coefficients, different temperature evolvements can be achieved. The above numerical simulation provided insight into physical processes of combined non-Fourier heat conduction and phase transition in laser ablation.

      PubDate: 2017-09-11T12:43:52Z
      DOI: 10.1016/j.actaastro.2017.08.028
      Issue No: Vol. 140 (2017)
  • Optimization design of energy deposition on single expansion ramp nozzle
    • Authors: Shengjun Ju; Chao Yan; Xiaoyong Wang; Yupei Qin; Zhifei Ye
      Pages: 351 - 361
      Abstract: Publication date: November 2017
      Source:Acta Astronautica, Volume 140
      Author(s): Shengjun Ju, Chao Yan, Xiaoyong Wang, Yupei Qin, Zhifei Ye
      Optimization design has been widely used in the aerodynamic design process of scramjets. The single expansion ramp nozzle is an important component for scramjets to produces most of thrust force. A new concept of increasing the aerodynamics of the scramjet nozzle with energy deposition is presented. The essence of the method is to create a heated region in the inner flow field of the scramjet nozzle. In the current study, the two-dimensional coupled implicit compressible Reynolds Averaged Navier–Stokes and Menter's shear stress transport turbulence model have been applied to numerically simulate the flow fields of the single expansion ramp nozzle with and without energy deposition. The numerical results show that the proposal of energy deposition can be an effective method to increase force characteristics of the scramjet nozzle, the thrust coefficient C T increase by 6.94% and lift coefficient C N decrease by 26.89%. Further, the non-dominated sorting genetic algorithm coupled with the Radial Basis Function neural network surrogate model has been employed to determine optimum location and density of the energy deposition. The thrust coefficient C T and lift coefficient C N are selected as objective functions, and the sampling points are obtained numerically by using a Latin hypercube design method. The optimized thrust coefficient C T further increase by 1.94%, meanwhile, the optimized lift coefficient C N further decrease by 15.02% respectively. At the same time, the optimized performances are in good and reasonable agreement with the numerical predictions. The findings suggest that scramjet nozzle design and performance can benefit from the application of energy deposition.

      PubDate: 2017-09-11T12:43:52Z
      DOI: 10.1016/j.actaastro.2017.09.004
      Issue No: Vol. 140 (2017)
  • Novel methodology for wide-ranged multistage morphing waverider based on
           conical theory
    • Authors: Zhen Liu; Jun Liu; Feng Ding; Zhixun Xia
      Pages: 362 - 369
      Abstract: Publication date: November 2017
      Source:Acta Astronautica, Volume 140
      Author(s): Zhen Liu, Jun Liu, Feng Ding, Zhixun Xia
      This study proposes the wide-ranged multistage morphing waverider design method. The flow field structure and aerodynamic characteristics of multistage waveriders are also analyzed. In this method, the multistage waverider is generated in the same conical flowfield, which contains a free-stream surface and different compression-stream surfaces. The obtained results show that the introduction of the multistage waverider design method can solve the problem of aerodynamic performance deterioration in the off-design state and allow the vehicle to always maintain the optimal flight state. The multistage waverider design method, combined with transfiguration flight strategy, can lead to greater design flexibility and the optimization of hypersonic wide-ranged waverider vehicles.

      PubDate: 2017-09-11T12:43:52Z
      DOI: 10.1016/j.actaastro.2017.09.006
      Issue No: Vol. 140 (2017)
  • Effects of injection nozzle exit width on rotating detonation engine
    • Authors: Jian Sun; Jin Zhou; Shijie Liu; Zhiyong Lin; Jianhua Cai
      Pages: 388 - 401
      Abstract: Publication date: November 2017
      Source:Acta Astronautica, Volume 140
      Author(s): Jian Sun, Jin Zhou, Shijie Liu, Zhiyong Lin, Jianhua Cai
      A series of numerical simulations of RDE modeling real injection nozzles with different exit widths are performed in this paper. The effects of nozzle exit width on chamber inlet state, plenum flowfield and detonation propagation are analyzed. The results are compared with that using an ideal injection model. Although the ideal injection model is a good approximation method to model RDE inlet, the two-dimensional effects of real nozzles are ignored in the ideal injection model so that some complicated phenomena such as the reflected waves caused by the nozzle walls and the reversed flow into the nozzles can not be modeled accurately. Additionally, the ideal injection model overpredicts the block ratio. In all the cases that stabilize at one-wave mode, the block ratio increases as the nozzle exit width gets smaller. The dual-wave mode case also has a relatively high block ratio. A pressure oscillation in the plenum with the same main frequency with the rotating detonation wave is observed. A parameter σ is applied to describe the non-uniformity in the plenum. σ increases as the nozzle exit width gets larger. Under some condition, the heat release on the interface of fresh premixed gas layer and detonation products can be strong enough to induce a new detonation wave. A spontaneous mode-transition process is observed for the smallest exit width case. Due to the detonation products existing in the premixed gas layer before the detonation wave, the detonation wave will propagate through reactants and products alternately, and therefore its strength will vary with time, especially near the chamber inlet. This tendency gets weaker as the injection nozzle exit width increases.

      PubDate: 2017-09-18T10:12:42Z
      DOI: 10.1016/j.actaastro.2017.09.008
      Issue No: Vol. 140 (2017)
  • Investigation of flameholding mechanisms in a kerosene-fueled scramjet
    • Authors: Yu-hang Wang; Wen-yan Song; De-yong Shi
      Pages: 402 - 408
      Abstract: Publication date: November 2017
      Source:Acta Astronautica, Volume 140
      Author(s): Yu-hang Wang, Wen-yan Song, De-yong Shi
      Laser-induced fluorescence and high-speed photography were employed to investigate the kerosene flame stabilization mechanism in a cavity-based scramjet combustor with an inlet condition corresponds to flight Mach number of 4. Pilot hydrogen was used to ignite the kerosene fuel. The PLIF results of kerosene distribution in the reacting cases showed that the mixing process was dramatically enhanced compared to the non-reacting cases. Sharp OH gradients were observed in the shear layer and the aft region of cavity, which indicated that the flame was located at these positions. A portion of hot products participated in the recirculation of the cavity and preheated the kerosene-air mixture in the leading edge. The heated mixture was ignited in the mid-cavity and the reaction zone spread into the mainstream flow. Due to the competition between the local flame speed and the local flow speed, the high-speed images showed that the spreading location was in fluctuation. This movement was observed to cause a low-frequency wall pressure fluctuation.

      PubDate: 2017-09-18T10:12:42Z
      DOI: 10.1016/j.actaastro.2017.09.010
      Issue No: Vol. 140 (2017)
  • Onsite vibrational characterization of DCMIX2/3 experiments
    • Authors: Judit Ollé; Diana Dubert; Josefina Gavaldà; Ana Laverón-Simavilla; Xavier Ruiz; Valentina Shevtsova
      Pages: 409 - 419
      Abstract: Publication date: November 2017
      Source:Acta Astronautica, Volume 140
      Author(s): Judit Ollé, Diana Dubert, Josefina Gavaldà, Ana Laverón-Simavilla, Xavier Ruiz, Valentina Shevtsova
      The SODI-DCMIX thermodiffusion series experiments are part of the fluid research program carried out by the European Space Agency on board of the International Space Station (ISS). In particular, DCIMIX2/3 were conducted in the past inside the Microgravity Science Glovebox in the US Laboratory. Due to the physical nature of the processes implied, these kind of runs were very long and particularly delicate because the low vibratory limit requirements must be maintained for hours. This restrictive condition not always is achieved, therefore, an accurate surveillance of the acceleration levels along the different experiments is necessary, to ensure a correct interpretation of the experimental results. This work analyzes onsite vibrational environment of DCMIX2/3 covering the periods in which the experiments were going on. To do so, acceleration signals only coming from the es03 sensor, nearest to the experimental equipment and located in the Glovebox, were downloaded from the PIMS NASA website. To be as precise as possible the signals have always been treated minute by minute. To detect the transient disturbances along the experiments, several warnings were considered. First, 1 min RMS values, for the three acceleration components were evaluated, in time and in frequency domain. Additional information was obtained by plotting the power spectral densities of the signals, PSD, and their spectrogram with the aim of characterizing long periods of acceleration data. Due to great influence of low frequencies in this type of experiments, the Frequency Factor Index, FFI, was evaluated each minute. Complementary, the spectral entropy evolution was proposed as a fast new indicator of external perturbations. It has been found a good correlation between the spectrogram, temporal RMS and spectral entropy. Finally, a graphic representation of the points associated to the 1-min RMS values in one-third-octave frequency intervals which exceed the ISS limit curve requirements, was considered as a new and easy strategy for depicting the warnings that recognize the main disturbances along the experiment.

      PubDate: 2017-09-18T10:12:42Z
      DOI: 10.1016/j.actaastro.2017.09.007
      Issue No: Vol. 140 (2017)
  • The water treatment and recycling in 105-day bioregenerative life support
           experiment in the Lunar Palace 1
    • Authors: Beizhen Xie; Guorong Zhu; Bojie Liu; Qiang Su; Shengda Deng; Lige Yang; Guanghui Liu; Chen Dong; Minjuan Wang; Hong Liu
      Pages: 420 - 426
      Abstract: Publication date: November 2017
      Source:Acta Astronautica, Volume 140
      Author(s): Beizhen Xie, Guorong Zhu, Bojie Liu, Qiang Su, Shengda Deng, Lige Yang, Guanghui Liu, Chen Dong, Minjuan Wang, Hong Liu
      In the bioregenerative life support system (BLSS), water recycling is one of the essential issues. The Lunar Palace 1, a ground-based bioregenerative life support system experimental facility, has been developed by our team and a 105-day closed bioregenerative life support experiment with multi-crew involved has been accomplished within this large-scale facility. During the 105-day experiment, activated carbon-absorption/ultra-filtration, membrane-biological activated carbon reactor and reduced pressure distillation technology have been used to purify the condensate water, sanitary & kitchen wastewater and urine, respectively. The results demonstrated that the combination of those technologies can achieve 100% regeneration of the water inside the Lunar Palace 1. The purified condensate water (the clean water) could meet the standards for drinking water quality in China (GB5749-2006). The treatment capacity of the membrane-biological activated carbon reactor for sanitary & kitchen wastewater could reach 150 kg/d. During the 105-d experiment, the average volume loading of the bioreactor was 0.441 kgCOD/(m3d), and the average COD removal efficiency was about 85.3%. The quality of the purified sanitary & kitchen wastewater (the greywater) could meet the standards for irrigation water quality (GB 5084–2005). In addition, during the 105-day experiment, the total excreted urine volume of three crew members was 346 L and the contained water was totally treated and recovered. The removal efficiency of ion from urine was about 88.12%. Moreover, partial nitrogen within the urine was recovered as well and the average recovery ratio was about 20.5%. The study laid a foundation for the water recycling technologies which could be used in BLSS for lunar or Mars bases.

      PubDate: 2017-09-18T10:12:42Z
      DOI: 10.1016/j.actaastro.2017.08.026
      Issue No: Vol. 140 (2017)
  • Parametric investigation of secondary injection in post-chamber on
           combustion performance for hybrid rocket motor
    • Authors: Guobiao Cai; Binbin Cao; Hao Zhu; Hui Tian; Xuan Ma
      Pages: 427 - 438
      Abstract: Publication date: November 2017
      Source:Acta Astronautica, Volume 140
      Author(s): Guobiao Cai, Binbin Cao, Hao Zhu, Hui Tian, Xuan Ma
      The objective of this effort is to study the combustion performance of a hybrid rocket motor with the help of 3D steady-state numerical simulation, which applies 90% hydrogen peroxide as the oxidizer and hydroxyl-terminated polybutadiene as the fuel. A method of secondary oxidizer injection in post-chamber is introduced to investigate the flow field characteristics and combustion efficiency. The secondary injection medium is the mixed gas coming from liquid hydrogen peroxide catalytic decomposition. The secondary injectors are uniformly set along the circumferential direction of the post-chamber. The simulation results obtained by above model are verified by experimental data. Three influencing parameters are considered: secondary injection diameter, secondary injection angle and secondary injection numbers. Simulation results reveals that this design could improve the combustion efficiency with respect to the same motor without secondary injection. Besides, the secondary injection almost has no effect on the regression rate and fuel sueface temperature distribution. It is also presented that the oxidizer is injected by 8 secondary injectors with a diameter of 7–8 mm in the direction of 120°in post-chamber is identified as the optimized secondary injection pattern, through which combustion efficiency, specific impulse efficiency as well as utilization of propellants are all improved obviously.

      PubDate: 2017-09-18T10:12:42Z
      DOI: 10.1016/j.actaastro.2017.09.009
      Issue No: Vol. 140 (2017)
  • Combustion characteristics and turbulence modeling of swirling reacting
           flow in solid fuel ramjet
    • Authors: Omer Musa; Chen Xiong; Zhou Changsheng
      Pages: 1 - 17
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): Omer Musa, Chen Xiong, Zhou Changsheng
      This paper reviews the historical studies have been done on the solid-fuel ramjet engine and difficulties associated with numerical modeling of swirling flow with combustible gases. A literature survey about works related to numerical and experimental investigations on solid-fuel ramjet as well as using swirling flow and different numerical approaches has been provided. An overview of turbulence modeling of swirling flow and the behavior of turbulence at streamline curvature and system rotation are presented. A new and simple curvature/correction factor is proposed in order to reduce the programming complexity of SST-CC turbulence model. Finally, numerical and experimental investigations on the impact of swirling flow on SFRJ have been carried out. For that regard, a multi-physics coupling code is developed to solve the problems of multi-physics coupling of fluid mechanics, solid pyrolysis, heat transfer, thermodynamics, and chemical kinetics. The connected-pipe test facility is used to carry out the experiments. The results showed a positive impact of swirling flow on SFRJ along with, three correlations are proposed.

      PubDate: 2017-07-08T02:03:34Z
      DOI: 10.1016/j.actaastro.2017.06.023
      Issue No: Vol. 139 (2017)
  • Torque distribution algorithm for effective use of reaction wheel torques
           and angular momentums
    • Authors: Mikihiro Sugita
      Pages: 18 - 23
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): Mikihiro Sugita
      In attitude control of spacecraft using more than three reaction wheels, the distribution of the attitude control torque to the wheels is not unique because of the redundancy. There are several wheel torque distribution algorithms which optimize the wheel torques or other factors. In particular, the optimal torque distribution algorithm is acknowledged as algorithm which minimizes the maximum wheel torque. This algorithm is advantageous to make maximum use of the wheel torques, because each wheel torque must be lower than the wheel torque capability and torque is the primary driver in many cases. However, as a result of minimizing the maximum wheel torque, the distribution of the wheel angular momentums is not calculated by a similar formula for the wheel torques distribution. In other words, the wheel angular momentums cannot be derived from the current attitude angular momentum. When certain wheel reaches maximum angular momentum earlier than the other wheels, this prohibits maximum use of the other wheels' capability. Therefore, minimizing the maximum wheel torque is not always effective when other constraint such as angular momentum matters. Recently, it has become more important that both wheel torques and angular momentums are used more effectively in order to improve the performance of the spacecraft agility, such as the high angular acceleration and rate, by using minimum spacecraft resources (i.e. minimum number of wheels which satisfies certain agility requirements). In this paper, shown is the wheel torque distribution algorithm which is effective in terms of both the wheel torques and angular momentums as much as possible. In the proposed algorithm, the wheel torques/angular momentums distributed from the current attitude torque/angular momentum can be optimal for particular direction like the spacecraft X/Y/Z axis. In addition, it is shown by numerical simulation that the proposed algorithm improves the usage of attitude control angular momentum by up to 60% compared to the optimal torque distribution algorithm.

      PubDate: 2017-07-08T02:03:34Z
      DOI: 10.1016/j.actaastro.2017.06.014
      Issue No: Vol. 139 (2017)
  • Experimental study of cone-struts and cavity flameholders in a
           kerosene-fueled round scramjet combustor
    • Authors: Dongqing Zhang; Wenyan Song
      Pages: 24 - 33
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): Dongqing Zhang, Wenyan Song
      Experimental investigations of liquid kerosene ignition and flameholding in a round supersonic combustor are presented. Three kinds of flameholders, a cone-struts structure, a cavity and the combination of the both, are studied for the kerosene ignition and flameholding. Results show that ignition and flameholding cannot be achieved by using the sole cone-struts flameholder, although flames are observed at the combustor outlet. The ignition and flameholding are achieved in a narrow range of equivalence ratios by using the cavity flameholder. This range is widened by employing the combination of the cone-struts and the cavity flameholders. It is observed that the back pressure disrupts the isolator entrance flow slightly by using the larger cone-struts (CR = 0.261). However, it does not happen when the smaller cone-struts (CR = 0.221) is employed. Then a characteristic air mass flow rate in the round combustor is redefined to calculate a modified Damkohler number that correlates the nonpremixed flame stability limits. The correlations are in good agreements with the experimental results.

      PubDate: 2017-07-08T02:03:34Z
      DOI: 10.1016/j.actaastro.2017.06.025
      Issue No: Vol. 139 (2017)
  • Analysis of the effect of attachment point bias during large space debris
           removal using a tethered space tug
    • Authors: Zhongyi Chu; Jingnan Di; Jing Cui
      Pages: 34 - 41
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): Zhongyi Chu, Jingnan Di, Jing Cui
      Space debris occupies a valuable orbital resource and is an inevitable and urgent problem, especially for large space debris because of its high risk and the possible crippling effects of a collision. Space debris has attracted much attention in recent years. A tethered system used in an active debris removal scenario is a promising method to de-orbit large debris in a safe manner. In a tethered system, the flexibility of the tether used in debris removal can possibly induce tangling, which is dangerous and should be avoided. In particular, attachment point bias due to capture error can significantly affect the motion of debris relative to the tether and increase the tangling risk. Hence, in this paper, the effect of attachment point bias on the tethered system is studied based on a dynamic model established based on a Newtonian approach. Next, a safety metric of avoiding a tangle when a tether is tensioned with attachment point bias is designed to analyse the tangling risk of the tethered system. Finally, several numerical cases are established and simulated to validate the effects of attachment point bias on a space tethered system.

      PubDate: 2017-07-08T02:03:34Z
      DOI: 10.1016/j.actaastro.2017.06.028
      Issue No: Vol. 139 (2017)
  • Weldability of an iron meteorite by Friction Stir Spot Welding: A
           contribution to in-space manufacturing
    • Abstract: Publication date: November 2017
      Source:Acta Astronautica, Volume 140
      Author(s): William Todd Evans, Kelsay E. Neely, Alvin M. Strauss, George E. Cook
      Friction Stir Welding has been proposed as an efficient and appropriate method for in space welding. It has the potential to serve as a viable option for assembling large scale space structures. These large structures will require the use of natural in space materials such as those available from iron meteorites. Impurities present in most iron meteorites limit its ability to be welded by other space welding techniques such as electron beam laser welding. This study investigates the ability to weld pieces of in situ Campo del Cielo meteorites by Friction Stir Spot Welding. Due to the rarity of the material, low carbon steel was used as a model material to determine welding parameters. Welded samples of low carbon steel, invar, and Campo del Cielo meteorite were compared and found to behave in similar ways. This study shows that meteorites can be Friction Stir Spot Welded and that they exhibit properties analogous to that of FSSW low carbon steel welds. Thus, iron meteorites can be regarded as another viable option for in-space or Martian construction.

      PubDate: 2017-09-24T01:14:48Z
  • Null motion strategy for spacecraft large angle agile maneuvering using
           hybrid actuators
    • Abstract: Publication date: November 2017
      Source:Acta Astronautica, Volume 140
      Author(s): Yun-Hua Wu, Feng Han, Bing Hua, Zhi-Ming Chen
      Control Moment Gyro (CMG) and Reaction Wheel (RW) generally serve in different spacecraft control tasks due to their unique characteristics, such as large output torque and control accuracy, respectively. The major concerns in using of CMG and RW are singularity and saturation, which could make spacecraft uncontrollable. RW as singularity escape equipment is adopted to construct hybrid actuator system named CMG & RW (CMGRW) to enhance and improve the spacecraft attitude performance as well as the CMG's. First, the attitude dynamic model of the spacecraft equipped with hybrid actuators is established and the corresponding singularity is analyzed thoroughly. Then null motion in CMGRW is further argued and proved feasible for both elliptical and hyperbolic singularities escape. A new performance index in terms of CMG and RW state is proposed, followed by a steering logic using gradient method with a feasible null motion vector to drive the hybrid actuator system to feasible states. Numerical simulations with initial conditions considering CMG singularity and RW saturation are selected to demonstrate the excellent performance of the hybrid actuators during the entire large angle agile maneuvering process, resulting in a group of feasible final states of the CMGRW that serves as great initial conditions for the next agile maneuvering.

      PubDate: 2017-09-24T01:14:48Z
  • On the secular decay of the LARES semi-major axis
    • Abstract: Publication date: November 2017
      Source:Acta Astronautica, Volume 140
      Author(s): C. Pardini, L. Anselmo, D.M. Lucchesi, R. Peron
      The laser-ranged satellite LARES is expected to provide new refined measurements of relativistic physics, as well as significant contributions to space geodesy and geophysics. The very low area-to-mass ratio of this passive and extremely dense satellite was chosen to reduce as much as possible the disturbing effects of non-gravitational perturbations. However, because of its height, about 1450 km compared with about 5800–5900 km for the two LAGEOS satellites, LARES is exposed to a much stronger drag due to neutral atmosphere. From a precise orbit determination, analyzing the laser ranging normal points of LARES over a time span of about 3.7 years with the GEODYN II (NASA/GSFC) code, it was found an average semi-major axis decay rate of −0.999 m per year, corresponding to a non-conservative net force acting nearly opposite to the velocity vector of the satellite and with a mean along-track acceleration of −1.444 × 10−11 m/s2. By means of a modified version of the SATRAP (ISTI/CNR) code, the neutral drag perturbation acting on LARES was evaluated over the same time span, taking into account the real evolution of solar and geomagnetic activities, with five thermospheric density models (JR-71, MSIS-86, MSISE-90, NRLMSISE-00 and GOST-2004). All of them provided consistent results, well within their acknowledged uncertainties. Moreover, when the same models (JR-71 and MSIS-86) were used within GEODYN II in a least-square fit of the tracking data, the differences between the average drag coefficients estimated with SATRAP and GEODYN were of the order of 1% or less. Unlike what happened for the two LAGEOS, where Yarkovsky thermal drag and charged particle drag were the leading causes, it was found that neutral atmosphere drag alone was able to explain most (≈98.6%) of the observed semi-major axis decay of LARES. The remaining ≈1.4%, corresponding to an average along-track acceleration of about −2 × 10−13 m/s2 (i.e. ≈1/70 of neutral drag), was probably linked to thermal thrust effects. It was 50%, or less, of the value previously reported in the literature, but further and more detailed investigations, including the detection of the signature of the periodic terms, will be needed in order to characterize such smaller non-gravitational perturbation.

      PubDate: 2017-09-24T01:14:48Z
  • Influence of micro-oxidation on joints of C/C composites and GH3044 for
           large-size aerospace parts
    • Abstract: Publication date: November 2017
      Source:Acta Astronautica, Volume 140
      Author(s): Xiaohong Shi, Xiuxiu Jin, Ningning Yan, Li Yang
      To improve the bonding strength of carbon/carbon (C/C) composites and GH3044 nickel-based superalloy, the bonding interlayer with Ti/Ni/Cu/Ni multiple foils were prepared by a two-step technique involving micro-oxidation and partial transient liquid phase (PTLP) process. Interface characteristics and mechanical behavior of joints were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), laser scanning confocal microscope (LSCM) and energy X-ray dispersive spectrometer (EDS). Results show that a porous layer on C/C composites is formed by micro-oxidation for more than 2 min at 1073 K in air, which provides a diffusion path for liquid phase to infiltrate into C/C substrate and generate a wedge interlocking interface. After micro-oxidation for 4 min, the shear strength of joints reaches 32.09 ± 1.98 MPa what is 36.73% higher than that of joints without micro-oxidation (23.47 ± 1.15 MPa). The increase of shear strength remarkably depends on physical interlocking and chemical bonding at porous interface.

      PubDate: 2017-09-24T01:14:48Z
  • Numerical simulation of wavy surface effect on the stability of a
           hypersonic boundary layer
    • Abstract: Publication date: November 2017
      Source:Acta Astronautica, Volume 140
      Author(s): Yunlong Zhou, Wei Liu, Zhenxia Chai, Xiaoliang Yang
      Generally the boundary layer transition is tripped by the surface roughness, while at certain circumstances, the surface roughness can delay the boundary layer transition. In this paper, by introducing the two-dimensional wall blow-suction upstream, high-order numerical method is used to simulate the Ma = 6 hypersonic boundary layer stability with a typical wavy-wall model. First, the mechanism of transition delay by the wavy wall is analyzed by comparison of the disturbance development in the flat-plate and wavy-wall boundary layer. Then the effects of the wavy-wall wave number, depth and streamwise location on the boundary layer stability are investigated. The results show that the disturbance development is closely related to the separation region. Compared with the flat plate, the wavy wall can suppress the second-mode instability via multiple separation regions, thus delaying the boundary layer transition. Concerning the wave number, the wavy wall with a single wave number has only a single short separation region, so the second-mode instability grows rapidly downstream; the wavy wall with multiple wave numbers means multiple separation regions and suppresses the second-mode instability sharply. As for the depth, the separation region grows with the increase of the wavy-wall depth and the second-mode instability is suppressed more evidently. Also as the location of the wavy wall moves downstream, the suppression on the second-mode instability is more obvious.

      PubDate: 2017-09-24T01:14:48Z
  • Embedded model control GNC for the Next Generation Gravity Mission
    • Abstract: Publication date: November 2017
      Source:Acta Astronautica, Volume 140
      Author(s): Luigi Colangelo, Luca Massotti, Enrico Canuto, Carlo Novara
      A Next Generation Gravity Mission (NGGM) concept for measuring the Earth's variable gravity field has been recently proposed by ESA. The mission objective consists in measuring the temporal variations of the Earth gravity field over a long-time span, with very high spatial and temporal resolutions. This paper focuses on the guidance, navigation and control (GNC) design for the science phase of the NGGM mission. NGGM will consist of a two-satellite long-distance formation like GRACE, where each satellite will be controlled to be drag-free like GOCE. Satellite-to-satellite distance variations, encoding gravity anomalies, will be measured by laser interferometry. The formation satellites, distant up to 200 km, will fly in a quasi-polar orbit at an Earth altitude between 300 and 450 km. Orbit and formation control counteract bias and drift of the residual drag-free accelerations, in order to reach orbit/formation long-term stability. Drag-free control allows the formation to fly counteracting the atmospheric drag, ideally subject only to gravity. Orbit and formation control, designed through the innovative Integrated Formation Control (IFC), have been integrated into a unique control system, aiming at stabilizing the formation triangle consisting of satellites and Earth Center of Masses. In addition, both spacecraft must align their control axis to the satellite-to-satellite line (SSL) with micro-radian accuracy. This is made possible by specific optical sensors and the inter-satellite laser interferometer, capable of materializing the SSL. Such sensors allow each satellite to pursue an autonomous alignment after a suitable acquisition procedure. Pointing control is severely constrained by the angular drag-free control, which must ideally zero the angular acceleration vector, in the science frequency band. The control unit has been designed according to the Embedded Model Control methodology and is organized in a hierarchical way, where the drag-free control plays the role of a wide-band inner loop, and orbit/formation and attitude/pointing controls are the narrow band outer loops. The relevant state equations were converted to discrete time providing the embedded model, a fundamental part of the control unit. The state predictor, control law and reference generator were built on and interfaced to the embedded model. Simulated results, via a high-fidelity simulator, prove the concept validity and show that the control performances are in agreement with the defined mission requirements. Indeed, the presented control strategy is shown to be capable of keeping the attitude and formation variables stable within the required boundaries, all over the 10-year mission, through a low-thrust authority in the order of a few milli-Newton.

      PubDate: 2017-09-24T01:14:48Z
  • Publication Information
    • Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139

      PubDate: 2017-08-27T14:57:51Z
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