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Showing 1 - 200 of 3043 Journals sorted alphabetically
AASRI Procedia     Open Access   (Followers: 15)
Academic Pediatrics     Hybrid Journal   (Followers: 20, SJR: 1.402, h-index: 51)
Academic Radiology     Hybrid Journal   (Followers: 18, SJR: 1.008, h-index: 75)
Accident Analysis & Prevention     Partially Free   (Followers: 83, 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: 27, 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: 331, 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: 211, 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: 9, 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)
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: 8, SJR: 1.039, h-index: 5)
Additives for Polymers     Full-text available via subscription   (Followers: 20)
Advanced Drug Delivery Reviews     Hybrid Journal   (Followers: 128, 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: 16, 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: 24, 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 Developmental Biology     Full-text available via subscription   (Followers: 11)
Advances in Digestive Medicine     Open Access   (Followers: 4)
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 Fluorine Science     Full-text available via subscription   (Followers: 8)
Advances in Food and Nutrition Research     Full-text available via subscription   (Followers: 47, 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 Human Factors/Ergonomics     Full-text available via subscription   (Followers: 25)
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: 5)
Advances in Intl. Accounting     Full-text available via subscription   (Followers: 4)
Advances in Life Course Research     Hybrid Journal   (Followers: 8, SJR: 0.764, h-index: 15)
Advances in Lipobiology     Full-text available via subscription   (Followers: 2)
Advances in Magnetic and Optical Resonance     Full-text available via subscription   (Followers: 9)
Advances in Marine Biology     Full-text available via subscription   (Followers: 16, SJR: 1.645, h-index: 45)
Advances in Mathematics     Full-text available via subscription   (Followers: 10, SJR: 3.261, h-index: 65)
Advances in Medical Sciences     Hybrid Journal   (Followers: 6, SJR: 0.489, h-index: 25)
Advances in Medicinal Chemistry     Full-text available via subscription   (Followers: 5)
Advances in Microbial Physiology     Full-text available via subscription   (Followers: 4, SJR: 1.44, h-index: 51)
Advances in Molecular and Cell Biology     Full-text available via subscription   (Followers: 22)
Advances in Molecular and Cellular Endocrinology     Full-text available via subscription   (Followers: 10)
Advances in Molecular Toxicology     Full-text available via subscription   (Followers: 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: 60)
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: 343, 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: 15)
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: 307, SJR: 0.816, h-index: 49)
AEU - Intl. J. of Electronics and Communications     Hybrid Journal   (Followers: 8, SJR: 0.318, h-index: 36)
African J. of Emergency Medicine     Open Access   (Followers: 5, SJR: 0.344, h-index: 6)
Ageing Research Reviews     Hybrid Journal   (Followers: 8, SJR: 3.289, h-index: 78)
Aggression and Violent Behavior     Hybrid Journal   (Followers: 405, SJR: 1.385, h-index: 72)
Agri Gene     Hybrid Journal  
Agricultural and Forest Meteorology     Hybrid Journal   (Followers: 15, SJR: 2.18, h-index: 116)
Agricultural Systems     Hybrid Journal   (Followers: 30, SJR: 1.275, h-index: 74)
Agricultural Water Management     Hybrid Journal   (Followers: 38, 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: 53, 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: 6)
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)
ALTER - European J. of Disability Research / Revue Européenne de Recherche sur le Handicap     Full-text available via subscription   (Followers: 7, SJR: 0.158, h-index: 9)
Alzheimer's & Dementia     Hybrid Journal   (Followers: 48, SJR: 4.289, h-index: 64)
Alzheimer's & Dementia: Diagnosis, Assessment & Disease Monitoring     Open Access   (Followers: 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: 38, 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: 33, 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: 191, SJR: 2.255, h-index: 171)
American J. of Ophthalmology     Hybrid Journal   (Followers: 54, SJR: 2.803, h-index: 148)
American J. of Ophthalmology Case Reports     Open Access   (Followers: 3)
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: 23, 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: 10)
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: 38, SJR: 1.548, h-index: 152)
Analytical Biochemistry     Hybrid Journal   (Followers: 162, 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: 157, 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]   [331 followers]  Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0094-5765
   Published by Elsevier Homepage  [3043 journals]
  • 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)
  • A modified modal method for solving the mission-oriented inverse
           kinematics of hyper-redundant space manipulators for on-orbit servicing
    • Authors: Wenfu Xu; Zonggao Mu; Tianliang Liu; Bin Liang
      Pages: 54 - 66
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): Wenfu Xu, Zonggao Mu, Tianliang Liu, Bin Liang
      A hyper-redundant space manipulator has extreme flexibility and is suitable to work in highly cluttered or multi-obstacles environment. However, its inverse kinematics is very challenging due to a large number of degrees of freedom (DOFs). In this paper, a modified modal method is proposed to solve the mission-oriented inverse kinematics. The spatial backbone of the manipulator is defined using a mode function, according to the mission requirement and working environment. All the universal joints are divided into M/2 groups, i.e. two adjacent universal joints comprise a group (M is the number of universal joints; it is assumed an even number. If it is an odd number, the remaining universal joint is a separated group). The whole manipulator is then segmented into M/2 sub-manipulators. Each sub-manipulator has 4-DOFs and is redundant for position or orientation. The last sub-manipulator is used to match the desired direction vector and the position of the end-effector with respect to the previous sub-manipulator's end. The remaining sub-manipulators are used to control the relative position between each other with one redundant degree of freedom. The equivalent link is fitted to the backbone function. The Cartesian coordinates of each node is then determined by combining the total length of the manipulator and the mode function. Then, the joint angles are solved through the position of each node. For each 4-DOF group, a parameter called arm angle is used to denote the redundancy and optimize its local configuration. Finally, typical cases of a 12-DOF and a 20-DOF manipulators are simulated. The results show that the method is very efficient for resolving the inverse kinematics of hyper-redundant space manipulators.

      PubDate: 2017-07-08T02:03:34Z
      DOI: 10.1016/j.actaastro.2017.06.015
      Issue No: Vol. 139 (2017)
  • Effects of injection pressure variation on mixing in a cold supersonic
           combustor with kerosene fuel
    • Authors: Wei-Lai Liu; Lin Zhu; Yin-Yin Qi; Jia-Ru Ge; Feng Luo; Hao-Ran Zou; Min Wei; Tien-Chien Jen
      Pages: 67 - 76
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): Wei-Lai Liu, Lin Zhu, Yin-Yin Qi, Jia-Ru Ge, Feng Luo, Hao-Ran Zou, Min Wei, Tien-Chien Jen
      Spray jet in cold kerosene-fueled supersonic flow has been characterized under different injection pressures to assess the effects of the pressure variation on the mixing between incident shock wave and transverse cavity injection. Based on the real scramjet combustor, a detailed computational fluid dynamics model is developed. The injection pressures are specified as 0.5, 1.0, 2.0, 3.0 and 4.0 MPa, respectively, with the other constant operation parameters (such as the injection diameter, angle and velocity). A three dimensional Couple Level Set & Volume of Fluids approach incorporating an improved Kelvin-Helmholtz & Rayleigh-Taylor model is used to investigate the interaction between kerosene and supersonic air. The numerical simulations primarily concentrate on penetration depth, span expansion area, angle of shock wave and sauter mean diameter distribution of the kerosene droplets with/without evaporation. Validation has been implemented by comparing the calculated against the measured in literature with good qualitative agreement. Results show that the penetration depth, span-wise angle and expansion area of the transverse cavity jet are all increased with the injection pressure. However, when the injection pressure is further increased, the value in either penetration depth or expansion area increases appreciably. This study demonstrates the feasibility and effectiveness of the combination of Couple Level Set & Volume of Fluids approach and an improved Kelvin-Helmholtz & Rayleigh-Taylor model, in turn providing insights into scramjet design improvement.

      PubDate: 2017-07-08T02:03:34Z
      DOI: 10.1016/j.actaastro.2017.06.031
      Issue No: Vol. 139 (2017)
  • Fast spacecraft adaptive attitude tracking control through immersion and
           invariance design
    • Authors: Haowei Wen; Xiaokui Yue; Peng Li; Jianping Yuan
      Pages: 77 - 84
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): Haowei Wen, Xiaokui Yue, Peng Li, Jianping Yuan
      This paper presents a novel non-certainty-equivalence adaptive control method for the attitude tracking control problem of spacecraft with inertia uncertainties. The proposed immersion and invariance (I&I) based adaptation law provides a more direct and flexible approach to circumvent the limitations of the basic I&I method without employing any filter signal. By virtue of the adaptation high-gain equivalence property derived from the proposed adaptive method, the closed-loop adaptive system with a low adaptation gain could recover the high adaptation gain performance of the filter-based I&I method, and the resulting control torque demands during the initial transient has been significantly reduced. A special feature of this method is that the convergence of the parameter estimation error has been observably improved by utilizing an adaptation gain matrix instead of a single adaptation gain value. Numerical simulations are presented to highlight the various benefits of the proposed method compared with the certainty-equivalence-based control method and filter-based I&I control schemes.

      PubDate: 2017-07-08T02:03:34Z
      DOI: 10.1016/j.actaastro.2017.06.024
      Issue No: Vol. 139 (2017)
  • Numerical simulation on the powder propellant pickup characteristics of
           feeding system at high pressure
    • Authors: Haijun Sun; Chunbo Hu; Xiaofei Zhu
      Pages: 85 - 97
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): Haijun Sun, Chunbo Hu, Xiaofei Zhu
      A numerical study of powder propellant pickup progress at high pressure was presented in this paper by using two-fluid model with kinetic theory of granular flow in the computational fluid dynamics software package ANSYS/Fluent. Simulations were conducted to evaluate the effects of initial pressure, initial powder packing rate and mean particle diameter on the flow characteristics in terms of velocity vector distribution, granular temperature, pressure drop, particle velocity and volume. The numerical results of pressure drop were also compared with experiments to verify the TFM model. The simulated results show that the pressure drop value increases as the initial pressure increases, and the granular temperature under the conditions of different initial pressures and packing rates is almost the same in the area of throttling orifice plate. While there is an appropriate value for particle size and packing rate to form a “core-annulus” structure in powder box, and the time-averaged velocity vector distribution of solid phase is inordinate.

      PubDate: 2017-07-08T02:03:34Z
      DOI: 10.1016/j.actaastro.2017.06.030
      Issue No: Vol. 139 (2017)
  • Breakthrough Listen – A new search for life in the universe
    • Authors: S. Pete Worden; Jamie Drew; Andrew Siemion; Dan Werthimer; David DeBoer; Steve Croft; David MacMahon; Matt Lebofsky; Howard Isaacson; Jack Hickish; Danny Price; Vishal Gajjar; Jason T. Wright
      Pages: 98 - 101
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): S. Pete Worden, Jamie Drew, Andrew Siemion, Dan Werthimer, David DeBoer, Steve Croft, David MacMahon, Matt Lebofsky, Howard Isaacson, Jack Hickish, Danny Price, Vishal Gajjar, Jason T. Wright

      PubDate: 2017-07-08T02:03:34Z
      DOI: 10.1016/j.actaastro.2017.06.008
      Issue No: Vol. 139 (2017)
  • Cultural ethology as a new approach of interplanetary crew's behavior
    • Authors: Carole Tafforin; Francisco Giner Abati
      Pages: 102 - 110
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): Carole Tafforin, Francisco Giner Abati
      From an evolutionary perspective, during short-term and medium-term orbital flights, human beings developed new spatial and motor behaviors to compensate for the lack of terrestrial gravity. Past space ethological studies have shown adaptive strategies to the tri-dimensional environment, with the goal of optimizing relationships between the astronaut and unusual sensorial-motor conditions. During a long-term interplanetary journey, crewmembers will have to develop new individual and social behaviors to adapt, far from earth, to isolation and confinement and as a result to extreme conditions of living and working together. Recent space psychological studies pointed out that heterogeneity is a feature of interplanetary crews, based on personality, gender mixing, internationality and diversity of backgrounds. Intercultural issues could arise between space voyagers. As a new approach we propose to emphasize the behavioral strategies of human groups' adaptation to this new multicultural dimension of the environment. Methodology Potential outcomes of applying ethological methods to the study of culture-specific human behaviors are investigated. Ethological and anthropological tools are used, based on observations and descriptions of individuals acting in a micro-society with their rules for living, their work habits and their specific customs and values. We focus the present study on interpersonal communications and organizations in diverse space simulation experiments and analogous environments (Mars-500 experiment, Mars Desert Research Station - MDRS, Tara-Arctic expedition and Concordia South pole station). Results During the Mars-500 experiment, the crewmembers (RU, EU, CH) were differently involved in the activities of daily living. At MDRS in the Desert of Utah, the crewmembers (FR, US, AU, DK) communicated differently in verbal discussions. During the Tara drift in the pack ice, the crewmembers (FR, MC, EE, NZ, NO) were differently positioned in the collective space. At Concordia station, the crewmembers (IT, FR) were grouped preferentially according to their living habits. The results show that cultural heterogeneity has different effects on interpersonal communications and organizations. When considering the isolated and confined crews like an evolving micro-society in unexplored environments, our preliminary analysis raises new questions as to the phylogenetic and epigenetic bases to which cultural ethology linked to anthropology may help to answer. Conclusion Cultural values, in addition to social values and personal values, have to be taken into consideration for future space exploration.

      PubDate: 2017-07-08T02:03:34Z
      DOI: 10.1016/j.actaastro.2017.06.017
      Issue No: Vol. 139 (2017)
  • Sliding mode disturbance observer-enhanced adaptive control for the
           air-breathing hypersonic flight vehicle
    • Authors: Hao An; Changhong Wang; Baris Fidan
      Pages: 111 - 121
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): Hao An, Changhong Wang, Baris Fidan
      This paper presents a backstepping procedure to design an adaptive controller for the air-breathing hypersonic flight vehicle (AHFV) subject to external disturbances and actuator saturations. In each step, a sliding mode exact disturbance observer (SMEDO) is exploited to exactly estimate the lumped disturbance in finite time. Specific dynamics are introduced to handle the possible actuator saturations. Based on SMEDO and introduced dynamics, an adaptive control law is designed, along with the consideration on “explosion of complexity” in backstepping design. The developed controller is equipped with fast disturbance rejection and great capability to accommodate the saturated actuators, which also lead to a wider application scope. A simulation study is provided to show the effectiveness and superiority of the proposed controller.

      PubDate: 2017-07-08T02:03:34Z
      DOI: 10.1016/j.actaastro.2017.06.026
      Issue No: Vol. 139 (2017)
  • Satellite single-axis attitude determination based on Automatic Dependent
           Surveillance - Broadcast signals
    • Authors: Kaixing Zhou; Xiucong Sun; Hai Huang; Xinsheng Wang; Guangwei Ren
      Pages: 130 - 140
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): Kaixing Zhou, Xiucong Sun, Hai Huang, Xinsheng Wang, Guangwei Ren
      The space-based Automatic Dependent Surveillance - Broadcast (ADS-B) is a new technology for air traffic management. The satellite equipped with spaceborne ADS-B system receives the broadcast signals from aircraft and transfers the message to ground stations, so as to extend the coverage area of terrestrial-based ADS-B. In this work, a novel satellite single-axis attitude determination solution based on the ADS-B receiving system is proposed. This solution utilizes the signal-to-noise ratio (SNR) measurement of the broadcast signals from aircraft to determine the boresight orientation of the ADS-B receiving antenna fixed on the satellite. The basic principle of this solution is described. The feasibility study of this new attitude determination solution is implemented, including the link budget and the access analysis. On this basis, the nonlinear least squares estimation based on the Levenberg-Marquardt method is applied to estimate the single-axis orientation. A full digital simulation has been carried out to verify the effectiveness and performance of this solution. Finally, the corresponding results are processed and presented minutely.

      PubDate: 2017-07-08T02:03:34Z
      DOI: 10.1016/j.actaastro.2017.05.038
      Issue No: Vol. 139 (2017)
  • Power matching between plasma generation and electrostatic acceleration in
           helicon electrostatic thruster
    • Authors: D. Ichihara; Y. Nakagawa; A. Uchigashima; A. Iwakawa; A. Sasoh; T. Yamazaki
      Pages: 157 - 164
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): D. Ichihara, Y. Nakagawa, A. Uchigashima, A. Iwakawa, A. Sasoh, T. Yamazaki
      The effects of a radio-frequency (RF) power on the ion generation and electrostatic acceleration in a helicon electrostatic thruster were investigated with a constant discharge voltage of 300 V using argon as the working gas at a flow rate either of 0.5 Aeq (Ampere equivalent) or 1.0 Aeq. A RF power that was even smaller than a direct-current (DC) discharge power enhanced the ionization of the working gas, thereby both the ion beam current and energy were increased. However, an excessively high RF power input resulted in their saturation, leading to an unfavorable increase in an ionization cost with doubly charged ion production being accompanied. From the tradeoff between the ion production by the RF power and the electrostatic acceleration made by the direct current discharge power, the thrust efficiency has a maximum value at an optimal RF to DC discharge power ratio of 0.6 – 1.0.

      PubDate: 2017-07-20T14:25:28Z
      DOI: 10.1016/j.actaastro.2017.06.032
      Issue No: Vol. 139 (2017)
  • Pose estimation and tracking of non-cooperative rocket bodies using
           Time-of-Flight cameras
    • Authors: Harvey Gómez Martínez; Gabriele Giorgi; Bernd Eissfeller
      Pages: 165 - 175
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): Harvey Gómez Martínez, Gabriele Giorgi, Bernd Eissfeller
      This paper presents a methodology for estimating the position and orientation of a rocket body in orbit – the target – undergoing a roto-translational motion, with respect to a chaser spacecraft, whose task is to match the target dynamics for a safe rendezvous. During the rendezvous maneuver the chaser employs a Time-of-Flight camera that acquires a point cloud of 3D coordinates mapping the sensed target surface. Once the system identifies the target, it initializes the chaser-to-target relative position and orientation. After initialization, a tracking procedure enables the system to sense the evolution of the target's pose between frames. The proposed algorithm is evaluated using simulated point clouds, generated with a CAD model of the Cosmos-3M upper stage and the PMD CamCube 3.0 camera specifications.

      PubDate: 2017-07-20T14:25:28Z
      DOI: 10.1016/j.actaastro.2017.07.002
      Issue No: Vol. 139 (2017)
  • Agent-based algorithm for fault detection and recovery of gyroscope's
           drift in small satellite missions
    • Authors: Johan Carvajal-Godinez; Jian Guo; Eberhard Gill
      Pages: 181 - 188
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): Johan Carvajal-Godinez, Jian Guo, Eberhard Gill
      Failure detection, isolation, and recovery is an essential requirement of any space mission design. Several spacecraft components, especially sensors, are prone to performance deviation due to intrinsic physical effects. For that reason, innovative approaches for the treatment of faults in onboard sensors are necessary. This work introduces the concept of agent-based fault detection and recovery for sensors used in satellite attitude determination and control. Its focuses on the implementation of an algorithm for addressing linear drift bias in gyroscopes. The algorithm was implemented using an agent-based architecture that can be integrated into the satellite's onboard software. Numerical simulations were carried out to show the effectiveness of this scheme in satellite's operations. The proposed algorithm showed a reduction of up to 50% in the stabilization time for the detumbling maneuver, and also an improvement in the pointing accuracy of up to 20% when it was applied in precise payload pointing procedures. The relevance of this contribution is its added value for optimizing the launch and early operation of small satellite missions, as well as, an enabler for innovative satellite functions, for instance, optical downlink communication.

      PubDate: 2017-07-20T14:25:28Z
      DOI: 10.1016/j.actaastro.2017.07.001
      Issue No: Vol. 139 (2017)
  • Structural testing and analysis of a braided, inflatable fabric torus
    • Authors: Andrew C. Young; William G. Davids; Daniel J. Whitney; Joshua D. Clapp; Andrew J. Goupee
      Pages: 189 - 200
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): Andrew C. Young, William G. Davids, Daniel J. Whitney, Joshua D. Clapp, Andrew J. Goupee
      Inflatable structural members have military, disaster relief, aerospace and other important applications as they possess low mass, can be stored in a relatively small volume and have significant load-carrying capacity once pressurized. Of particular interest to the present research is the Hypersonic Inflatable Aerodynamic Decelerator (HIAD) structure under development by NASA. In order to make predictions about the structural response of the HIAD system, it is necessary to understand the response of individual inflatable tori composing the HIAD structure. These inflatable members present unique challenges to structural testing and modeling due to their internal inflation pressure and relative compliance. Structural testing was performed on a braided, inflatable, toroidal structural member with axial reinforcing cords. The internal inflation pressure, magnitude of enforced displacement and loading methodology were varied. In-plane and out-of-plane experimental results were compared to model predictions using a three dimensional, corotational, flexibility-based fiber-beam finite element model including geometric and material nonlinearities, as well as the effects of inflation pressure. It was found that in order to approximate the load-deformation response observed in experimentation it is necessary to carefully control the test and model boundary conditions and loading scheme.

      PubDate: 2017-07-20T14:25:28Z
      DOI: 10.1016/j.actaastro.2017.07.004
      Issue No: Vol. 139 (2017)
  • Drift-free solar sail formations in elliptical Sun-synchronous orbits
    • Authors: Khashayar Parsay; Hanspeter Schaub
      Pages: 201 - 212
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): Khashayar Parsay, Hanspeter Schaub
      To study the spatial and temporal variations of plasma in the highly dynamic environment of the magnetosphere, multiple spacecraft must fly in a formation. The objective for this study is to investigate the feasibility of solar sail formation flying in the Earth-centered, Sun-synchronous orbit regime. The focus of this effort is to enable formation flying for a group of solar sails that maintain a nominally fixed Sun-pointing attitude during formation flight, solely for the purpose of precessing their orbit apse lines Sun-synchronously. A fixed-attitude solar sail formation is motivated by the difficulties in the simultaneous control of orbit and attitude in flying solar sails. First, the secular rates of the orbital elements resulting from the effects of solar radiation pressure (SRP) are determined using averaging theory for a Sun-pointing attitude sail. These averaged rates are used to analytically derive the first-order necessary conditions for a drift-free solar sail formation in Sun-synchronous orbits, assuming a fixed Sun-pointing orientation for each sail in formation. The validity of the first-order necessary conditions are illustrated by designing quasi-periodic relative motions. Next, nonlinear programming is applied to design truly drift-free two-craft solar sail formations. Lastly, analytic expressions are derived to determine the long-term dynamics and sensitivity of the formation with respect to constant attitude errors, uncertainty in orbital elements, and uncertainty in a sail's characteristic acceleration.

      PubDate: 2017-07-20T14:25:28Z
      DOI: 10.1016/j.actaastro.2017.06.027
      Issue No: Vol. 139 (2017)
  • Non-cooperative spacecraft pose tracking based on point cloud feature
    • Authors: Ying He; Bin Liang; Jin He; Shunzhi Li
      Pages: 213 - 221
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): Ying He, Bin Liang, Jin He, Shunzhi Li
      On-orbit services have been paid more and more attention for its role in spacecraft life-extension, capacity improvement and on-orbit debris removal. As most of on-orbit targets are non-cooperative, relatively accurate pose measurement is very essential for subsequent operations. However, with the rapid development of TriDAR, flash LIDAR and other laser scanning equipment in non-cooperative target measurement, it becomes more imperative to research methods for non-cooperative target pose tracking based on 3D point cloud feature. In this paper, a method for non-cooperative target pose tracking based on point cloud feature is proposed. Firstly, the target is identified using curvature, normal, density and other geometric features of the point cloud. Then the particle filter algorithm is used to recognize the position and orientation of the target being tracked by calculating the similarity of the point cloud features of two adjacent frames. Experimental results showed that the proposed method could effectively identify the features of non-cooperative targets and track their position and attitude.

      PubDate: 2017-07-20T14:25:28Z
      DOI: 10.1016/j.actaastro.2017.06.021
      Issue No: Vol. 139 (2017)
  • Change of growth promotion and disease resistant of wheat seedling by
           application of biocontrol bacterium Pseudochrobactrum kiredjianiae A4
           under simulated microgravity
    • Authors: Yuming Fu; Han Gao; Hongyan Li; Youcai Qin; Wen Tang; Jinying Lu; Ming Li; Lingzhi Shao; Hong Liu
      Pages: 222 - 227
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): Yuming Fu, Han Gao, Hongyan Li, Youcai Qin, Wen Tang, Jinying Lu, Ming Li, Lingzhi Shao, Hong Liu
      Plant disease control and prevention in microgravity are critical for space plant cultivation. This study investigated the effects of a biocontrol bacterium Pseudochrobactrum kiredjianiae A4 on growth development and antifungal potential of wheat seedlings under simulated microgravity. The growth, antioxidant status and plant immune hormone of both non-infected and infected wheat seedlings were detected before and after inoculation of A4 strains under simulated microgravity condition (μG) and ground condition (1G). Our results showed that bacteria A4 promoted wheat growth by increasing root length and biomass accumulation and meanwhile enhancing fungal disease resistance through improving the antioxidant enzyme activities and plant hormone secretion. Moreover, A4 exhibited a weaker promotion ability on wheat biomass accumulation and disease resistance under μG condition compared to that under 1G. These results not only expand our understanding of the impact of microgravity on plant-microbe interaction, but also provide valuable insights into using plant beneficial microbes for plant cultivation and crop protection in space.

      PubDate: 2017-07-20T14:25:28Z
      DOI: 10.1016/j.actaastro.2017.06.022
      Issue No: Vol. 139 (2017)
  • The elements of a commercial human spaceflight safety reporting system
    • Authors: Ian Christensen
      Pages: 228 - 232
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): Ian Christensen
      In its report on the SpaceShipTwo accident the National Transportation Safety Board (NTSB) included in its recommendations that the Federal Aviation Administration (FAA) “in collaboration with the commercial spaceflight industry, continue work to implement a database of lessons learned from commercial space mishap investigations and encourage commercial space industry members to voluntarily submit lessons learned.” In its official response to the NTSB the FAA supported this recommendation and indicated it has initiated an iterative process to put into place a framework for a cooperative safety data sharing process including the sharing of lessons learned, and trends analysis. Such a framework is an important element of an overall commercial human spaceflight safety system. As the industry matures and approaches a time of regular operational flights carrying paying commercial passengers, the time is right to consider the development of an industry-wide safety reporting system focused on operational hazards, incidents, and close calls. Mature safety reporting systems of this nature exist, both in the aerospace sector and in other industries. For example: • The Aviation Safety Reporting System (ASRS) in the United States • The Federal Railroad Authority Confidential Close Call Reporting System • The NASA Safety Reporting System (NSRS) • Aviation Safety Reporting Systems operated by several civil aviation authorities around the globe These successful systems offer a number of lessons learned and operational best practices that might be applied to a prospective commercial human spaceflight safety reporting system. Through a review of these programs, focusing on systems in the U.S., this paper will describe elements of a safety reporting system that might be developed in support of the commercial human spaceflight industry. Factors to be addressed include: • Origins and motivations for the system • Organizational and operational approaches • Treatment of confidentiality, both for reporters' personally identifiable information, and for proprietary or commercially sensitive information • Relationship to lessons learned and safety data exchange programs • Authority to act upon information received One element that these systems often have in common is that they were established following a tragic incident involving the loss of multiple lives. The FAA's efforts to analyze and implement a commercial spaceflight; safety lessons learned database offers a window to develop a safety reporting system, in consultation with; industry, prior to similar tragic incidents involving commercial spaceflight participants;

      PubDate: 2017-07-20T14:25:28Z
      DOI: 10.1016/j.actaastro.2017.07.012
      Issue No: Vol. 139 (2017)
  • A non-saturated sliding-mode control of shaft deflection for magnetically
    • Authors: Chao Han; Xinwei Wang; Yuanjin Yu; Zhaohua Yang
      Pages: 233 - 242
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): Chao Han, Xinwei Wang, Yuanjin Yu, Zhaohua Yang
      The magnetically suspended momentum wheel (MSMW) expands its fresh functions through deflecting the rotary shaft. An improved nonsingular terminal sliding-mode control (NTSMC) method is proposed to achieve high precision tracking of shaft deflection for the MSMW under coupled disturbance and saturated amplifier. A novel structure designed for this MSMW is introduced initially. Its magnetic torque model and coupled disturbance are analyzed, and a tracking error dynamic model is established. Then a NTSMC method is applied to shaft tracking control. As the saturation of amplifier influences tracking performances, an improved NTSMC is designed to deal with saturation problem. Finally, several simulations are performed to validate the effectiveness of the proposed method. The results indicate the proposed method improves the tracking precision and velocity compared with the conventional integral sliding-mode method, and solves the saturation problem compared with existing NTSMC method.

      PubDate: 2017-07-20T14:25:28Z
      DOI: 10.1016/j.actaastro.2017.07.016
      Issue No: Vol. 139 (2017)
  • A combined impedance-PD approach for controlling a dual-arm space
           manipulator in the capture of a non-cooperative target
    • Authors: A. Stolfi; P. Gasbarri; M. Sabatini
      Pages: 243 - 253
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): A. Stolfi, P. Gasbarri, M. Sabatini
      In the near future robotic systems will be playing an increasingly important role in space applications such as repairing, refueling, re-orbiting spacecraft and cleaning up the increasing amount of space debris. Space Manipulator Systems (SMSs) are robotic systems made of a platform (which has its own actuators such as thrusters and reaction wheels) equipped with one or more deployable arms. The present paper focuses on the issue of maintaining a stable first contact between the arms terminal parts (i.e. the end-effectors) and a target satellite, before the actual grasp is performed. The selected approach is a modified version of the Impedance Control algorithm, in which the end-effector is controlled in order to make it behave like a mass-spring-damper system regardless of the reaction motion of the base, so to absorb the impact energy. The usual approach consists in considering a point mass target and one-dimensional contact dynamics; however, the contact between the chaser and the target could generate a perturbation on the attitude of the target. On account of this, in the present work a more realistic scenario, consisting in a 2D rigid target and a relevant 2D contact dynamics, is considered. A two-arm configuration of the SMS is modelled and its effectiveness analyzed. The performance of the proposed control architecture is evaluated by means of a co-simulation involving the MSC Adams multibody code (for describing the dynamics of the space robot and target) together with Simulink (for the determination of the control actions). The co-simulation is a particularly useful tool to implement robust control applied to detailed dynamic systems. Several numerical results complete the work.

      PubDate: 2017-07-20T14:25:28Z
      DOI: 10.1016/j.actaastro.2017.07.014
      Issue No: Vol. 139 (2017)
  • Galaxy travel via Alcubierre's warp drive
    • Authors: M. Fil'chenkov; Yu. Laptev
      Pages: 254 - 257
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): M. Fil'chenkov, Yu. Laptev
      The possibilities of interstellar flights for extraterrestrial civilizations have been considered. A superluminal motion (hypermotion) via M. Alcubierre's warp drive is considered. Parameters of the warp drive have been estimated. The equations of starship geodesics have been solved. The starship velocity has been shown to exceed the speed of light, with the local velocity relative to the deformed space-time being subluminal. Hawking's radiation does not prove to affect the ship interior considerably. Difficulties related to a practical realization of the hypermotion are indicated.

      PubDate: 2017-07-20T14:25:28Z
      DOI: 10.1016/j.actaastro.2017.07.011
      Issue No: Vol. 139 (2017)
  • Visualization of the heat release zone of highly turbulent premixed jet
    • Authors: Liang Lv; Jianguo Tan; Jiajian Zhu
      Pages: 258 - 265
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): Liang Lv, Jianguo Tan, Jiajian Zhu
      Visualization of the heat release zone (HRZ) of highly turbulent flames is significantly important to understand the interaction between turbulence and chemical reactions, which is the foundation to design and optimize engines. Simultaneous measurements of OH and CH2O using planar laser-induced fluorescence (PLIF) were performed to characterize the HRZ. A well-designed piloted premixed jet burner was employed to generate four turbulent premixed CH4/air jet flames, with different jet Reynolds numbers (Re jet ) ranging from 4900 to 39200. The HRZ was visualized by both the gradient of OH and the pixel-by-pixel product of OH and CH2O. It is shown that turbulence has an increasing effect on the spatial structure of the flame front with an increasing height above the jet exit for the premixed jet flames, which results in the broadening of the HRZ and the increase of the wrinkling. The HRZ remains thin as the Re jet increases, whereas the preheat zone is significantly broadened and thickened. This indicates that the smallest turbulent eddies can only be able to enter the flame front rather than the HRZ in the present flame conditions. The flame quenching is observed with Re jet  = 39200, which may be due to the strong entrainment of the cold air from outside of the burned gas region.

      PubDate: 2017-07-20T14:25:28Z
      DOI: 10.1016/j.actaastro.2017.07.005
      Issue No: Vol. 139 (2017)
  • Dynamic analysis of the tether transportation system using absolute nodal
           coordinate formulation
    • Authors: Xin Sun; Ming Xu; Rui Zhong
      Pages: 266 - 277
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): Xin Sun, Ming Xu, Rui Zhong
      Long space tethers are becoming a rising concern as an alternate way for transportation in space. It benefits from fuel economizing. This paper focuses on the dynamics of the tether transportation system, which consists of two end satellites connected by a flexible tether, and a movable vehicle driven by the actuator carried by itself. The Absolute Nodal Coordinate Formulation is applied to the establishment of the equation of motion, so that the influence caused by the distributed mass and elasticity of the tether is introduced. Moreover, an approximated method for accelerating the calculation of the generalized gravitational forces on the tether is proposed by substituting the volume integral every step into summation of finite terms. Afterwards, dynamic evolutions of such a system in different configurations are illustrated using numerical simulations. The deflection of the tether and the trajectory of the crawler during the transportation is investigated. Finally, the effect on the orbit of the system due to the crawler is revealed.

      PubDate: 2017-07-20T14:25:28Z
      DOI: 10.1016/j.actaastro.2017.07.020
      Issue No: Vol. 139 (2017)
  • Investigation on the propagation process of rotating detonation wave
    • Authors: Li Deng; Hu Ma; Can Xu; Changsheng Zhou; Xiao Liu
      Pages: 278 - 287
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): Li Deng, Hu Ma, Can Xu, Changsheng Zhou, Xiao Liu
      Effects of mass flow rate and equivalence ratio on the wave speed performance and instantaneous pressure characteristics of rotating detonation wave are investigated using hydrogen and air mixtures. The interaction between air and fuel manifolds and combustion chamber is also identified. The results show that the rotating detonation waves are able to adapt themselves to the changes of equivalence ratio during the run, the rotating detonation waves decayed gradually and then quenched after the shutdown of reactants supply. The wave speed performance is closely related to the mass flow rate and the pressure ratio of the fuel to air manifolds at different equivalence ratios. The blockage ratio of the air manifold increases with the increasing of the wave speed due to high-pressure detonation products, while increasing of the equivalence ratios will reduce the blockage ratio of the hydrogen manifold. Higher equivalence ratio can enhance the stabilization of the rotating detonation wave and lower equivalence ratio will lead to the large fluctuations of the lap time and instantaneous pressure magnitude. The overpressure of rotating detonation wave is determined by the combination of mass flow rate and equivalence ratio, which increases with the increasing of mass flow rate in the equivalence ratio ranges that the rotating detonation wave propagates stably. The secondary spike in the instantaneous pressure and ionization signals indicates that a shocked mixing zone exists near the fuel injection holes and the reflection of shock in the mixing zone induces the reaction.

      PubDate: 2017-07-20T14:25:28Z
      DOI: 10.1016/j.actaastro.2017.07.024
      Issue No: Vol. 139 (2017)
  • Effect of thermochemical non-equilibrium on the aerodynamics of an
           osculating-cone waverider under different angles of attack
    • Authors: Zhen Liu; Jun Liu; Feng Ding; Kai Li; Zhixun Xia
      Pages: 288 - 295
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): Zhen Liu, Jun Liu, Feng Ding, Kai Li, Zhixun Xia
      In order to research the effect of thermochemical non-equilibrium on the aerodynamics of an osculating-cone waverider, thermochemical non-equilibrium flow and perfect gas model are employed to study the aerodynamics of an osculating-cone waverider under different angles of attack. The obtained results show that the slope of the oblique shock wave has little difference when considering the thermochemical non-equilibrium effect under the condition of zero angle of attack. However, under the condition of other attack angles, the slope of the oblique shock wave diminishes when considering the thermochemical non-equilibrium effect. Furthermore, the non-equilibrium effect moves the pressure center of the osculating-cone waverider forward by as much as 1.53% of the whole craft's length, which must be taken into consideration in the balance design of aircraft.

      PubDate: 2017-07-20T14:25:28Z
      DOI: 10.1016/j.actaastro.2017.07.013
      Issue No: Vol. 139 (2017)
  • Coordinated control of a space manipulator tested by means of an air
           bearing free floating platform
    • Authors: Marco Sabatini; Paolo Gasbarri; Giovanni B. Palmerini
      Pages: 296 - 305
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): Marco Sabatini, Paolo Gasbarri, Giovanni B. Palmerini
      A typical approach studied for the guidance of next generation space manipulators (satellites with robotic arms aimed at autonomously performing on-orbit operations) is to decouple the platform and the arm maneuvers, which are supposed to happen sequentially, mainly because of safety concerns. This control is implemented in this work as a two-stage Sequential control, where a first stage calls for the motion of the platform and the second stage calls for the motion of the manipulator. A second novel strategy is proposed, considering the platform and the manipulator as a single multibody system subject to a Coordinated control, with the goal of approaching and grasping a target spacecraft. At the scope, a region that the end effector can reach by means of the arm motion with limited reactions on the platform is identified (the so called Reaction Null workspace). The Coordinated control algorithm performs a gain modulation (finalized to a balanced contribution of the platform and arm motion) as a function of the target position within this Reaction Null map. The result is a coordinated maneuver in which the end effector moves thanks to the platform motion, predominant in a first phase, and to the arm motion, predominant when the Reaction-Null workspace is reached. In this way the collision avoidance and attitude over-control issues are automatically considered, without the need of splitting the mission in independent (and overall sub-optimal) segments. The guidance and control algorithms are first simulated by means of a multibody code, and successively tested in the lab by means of a free floating platform equipped with a robotic arm, moving frictionless on a flat granite table thanks to air bearings and on-off thrusters; the results will be discussed in terms of optimality of the fuel consumption and final accuracy.

      PubDate: 2017-07-20T14:25:28Z
      DOI: 10.1016/j.actaastro.2017.07.015
      Issue No: Vol. 139 (2017)
  • Integrating spaceflight human system risk research
    • Authors: Jennifer Mindock; Sarah Lumpkins; Wilma Anton; Maria Havenhill; Mark Shelhamer; Michael Canga
      Pages: 306 - 312
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): Jennifer Mindock, Sarah Lumpkins, Wilma Anton, Maria Havenhill, Mark Shelhamer, Michael Canga
      NASA is working to increase the likelihood of exploration mission success and to maintain crew health, both during exploration missions and long term after return to Earth. To manage the risks in achieving these goals, a system modelled after a Continuous Risk Management framework is in place. “Human System Risks” (Risks) have been identified, and 32 are currently being actively addressed by NASA's Human Research Program (HRP). Research plans for each of HRP's Risks have been developed and are being executed. Inter-disciplinary ties between the research efforts supporting each Risk have been identified; however, efforts to identify and benefit from these connections have been mostly ad hoc. There is growing recognition that solutions developed to address the full set of Risks covering medical, physiological, behavioural, vehicle, and organizational aspects of exploration missions must be integrated across Risks and disciplines. This paper discusses how a framework of factors influencing human health and performance in space is being applied as the backbone for bringing together sometimes disparate information relevant to the individual Risks. The resulting interrelated information enables identification and visualization of connections between Risks and research efforts in a systematic and standardized manner. This paper also discusses the applications of the visualizations and insights into research planning, solicitation, and decision-making processes.

      PubDate: 2017-07-20T14:25:28Z
      DOI: 10.1016/j.actaastro.2017.07.017
      Issue No: Vol. 139 (2017)
  • Optimal Bi-elliptic transfer between two generic coplanar elliptical
    • Authors: Elena V. Kiriliuk; Sergey A. Zaborsky
      Pages: 321 - 324
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): Elena V. Kiriliuk, Sergey A. Zaborsky
      In this article, we show the optimal total delta velocity for bi-elliptic and bi-parabolic (through infinity) transfers between non-coaxial boundary orbits. The bi-parabolic transfer is cotangential.

      PubDate: 2017-07-27T14:36:24Z
      DOI: 10.1016/j.actaastro.2017.07.006
      Issue No: Vol. 139 (2017)
  • Experiments and simulation of a net closing mechanism for tether-net
           capture of space debris
    • Authors: Inna Sharf; Benjamin Thomsen; Eleonora M. Botta; Arun K. Misra
      Pages: 332 - 343
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): Inna Sharf, Benjamin Thomsen, Eleonora M. Botta, Arun K. Misra
      This research addresses the design and testing of a debris containment system for use in a tether-net approach to space debris removal. The tether-net active debris removal involves the ejection of a net from a spacecraft by applying impulses to masses on the net, subsequent expansion of the net, the envelopment and capture of the debris target, and the de-orbiting of the debris via a tether to the chaser spacecraft. To ensure a debris removal mission's success, it is important that the debris be successfully captured and then, secured within the net. To this end, we present a concept for a net closing mechanism, which we believe will permit consistently successful debris capture via a simple and unobtrusive design. This net closing system functions by extending the main tether connecting the chaser spacecraft and the net vertex to the perimeter and around the perimeter of the net, allowing the tether to actuate closure of the net in a manner similar to a cinch cord. A particular embodiment of the design in a laboratory test-bed is described: the test-bed itself is comprised of a scaled-down tether-net, a supporting frame and a mock-up debris. Experiments conducted with the facility demonstrate the practicality of the net closing system. A model of the net closure concept has been integrated into the previously developed dynamics simulator of the chaser/tether-net/debris system. Simulations under tether tensioning conditions demonstrate the effectiveness of the closure concept for debris containment, in the gravity-free environment of space, for a realistic debris target. The on-ground experimental test-bed is also used to showcase its utility for validating the dynamics simulation of the net deployment, and a full-scale automated setup would make possible a range of validation studies of other aspects of a tether-net debris capture mission.

      PubDate: 2017-07-27T14:36:24Z
      DOI: 10.1016/j.actaastro.2017.07.026
      Issue No: Vol. 139 (2017)
  • A methodology to study the possible occurrence of chugging in liquid
           rocket engines during transient start-up
    • Authors: Marco Leonardi; Francesco Nasuti; Francesco Di Matteo; Johan Steelant
      Pages: 344 - 356
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): Marco Leonardi, Francesco Nasuti, Francesco Di Matteo, Johan Steelant
      An investigation on the low frequency combustion instabilities due to the interaction of combustion chamber and feed line dynamics in a liquid rocket engine is carried out implementing a specific module in the system analysis software EcosimPro. The properties of the selected double time lag model are identified according to the two classical assumptions of constant and variable time lag. Module capabilities are evaluated on a literature experimental set up consisting of a combustion chamber decoupled from the upstream feed lines. The computed stability map results to be in good agreement with both experimental data and analytical models. Moreover, the first characteristic frequency of the engine is correctly predicted, giving confidence on the use of the module for the analysis of chugging instabilities. As an example of application, a study is carried out on the influence of the feed lines on the system stability, correctly capturing that the lines extend the stable regime of the combustion chamber and that the propellant domes play a key role in coupling the dynamics of combustion chamber and feed lines. A further example is presented to discuss on the role of pressure growth rate and of the combustion chamber properties on the possible occurrence of chug instability during engine start-up and on the conditions that lead to its damping or growth.

      PubDate: 2017-07-27T14:36:24Z
      DOI: 10.1016/j.actaastro.2017.07.027
      Issue No: Vol. 139 (2017)
  • Attitude and vibration control of a satellite containing flexible solar
           arrays by using reaction wheels, and piezoelectric transducers as sensors
           and actuators
    • Authors: Ijar M. da Fonseca; Domingos A. Rade; Luiz C.S. Goes; Thiago de Paula Sales
      Pages: 357 - 366
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): Ijar M. da Fonseca, Domingos A. Rade, Luiz C.S. Goes, Thiago de Paula Sales
      The primary purpose of this paper is to provide insight into control-structure interaction for satellites comprising flexible appendages and internal moving components. The physical model considered herein aiming to attend such purpose is a rigid-flexible satellite consisting of a rigid platform containing two rotating flexible solar panels. The solar panels rotation is assumed to be in a sun-synchronous configuration mode. The panels contain surface-bonded piezoelectric patches that can be used either as sensors for the elastic displacements or as actuators to counteract the vibration motion. It is assumed that in the normal mode operation the satellite platform points towards the Earth while the solar arrays rotate so as to follow the Sun. The vehicle moves in a low Earth polar orbit. The technique used to obtain the mathematical model combines the Lagrangian formulation with the Finite Elements Method used to describe the dynamics of the solar panel. The gravity-gradient torque as well as the torque due to the interaction of the Earth magnetic field and the satellite internal residual magnetic moment is included as environmental perturbations. The actuators are three reaction wheels for attitude control and piezoelectric actuators to control the flexible motion of the solar arrays. Computer simulations are performed using the MATLAB® software package. The following on-orbit satellite operating configurations are object of analysis: i) Satellite pointing towards the Earth (Earth acquisition maneuver) by considering the initial conditions in the elastic displacement equal to zero, aiming the assessment of the flexible modes excitation by the referred maneuver; ii) the satellite pointing towards the Earth with the assumption of an initial condition different from zero for the flexible motion such that the attitude alterations are checked against the elastic motion disturbance; and iii) attitude acquisition accomplished by taking into account initial conditions different from zero for both attitude and elastic vibrations. Additionally, the control efforts for the three cases are compared. Results indicate that the attitude control is able to excite the solar panels' vibration modes and vice-versa. The piezoelectric vibration control shows significant performance improvement when compared to contributions of the attitude control to the vibration damping.

      PubDate: 2017-07-27T14:36:24Z
      DOI: 10.1016/j.actaastro.2017.07.018
      Issue No: Vol. 139 (2017)
  • An adaptive optics aided differential optical positioning for passive
           orbit determination of the space debris at the geostationary orbit
    • Authors: Piotr Piatrou; Francois Rigaut
      Pages: 367 - 376
      Abstract: Publication date: October 2017
      Source:Acta Astronautica, Volume 139
      Author(s): Piotr Piatrou, Francois Rigaut
      Proliferation of space debris presents an imminent threat to all space assets. The problem is especially severe for the geostationary band of orbits (GEO) because the GEO objects never leave their orbit and, at the same time, are difficult to observe and operate due to large distance from the Earth. Under the influence of tidal forces, even passive GEO objects achieve high local velocities without vacating GEO positions, which may potentially lead to devastating collisions. Our ability to predict collisions in GEO is limited by the scarcity of the accurate orbital data, especially about the small and passive objects. The efforts to address this omission strongly rely on the ground-based optical sensors and, consequently, on the efficient space object detection and tracking techniques. In this paper we propose a passive differential optical debris tracking technique combining adaptive optics and a high accuracy astrometric references resulting in a significant improvement in the GEO object positioning accuracy. The achievable accuracy is estimated via detailed numerical simulations of two telescopes in different locations.

      PubDate: 2017-07-27T14:36:24Z
      DOI: 10.1016/j.actaastro.2017.07.028
      Issue No: Vol. 139 (2017)
  • A new analytical solution of the hyperbolic Kepler equation using the
           Adomian decomposition method
    • Authors: Abdelhalim Ebaid; Randolph Rach; Essam El-Zahar
      Pages: 1 - 9
      Abstract: Publication date: September 2017
      Source:Acta Astronautica, Volume 138
      Author(s): Abdelhalim Ebaid, Randolph Rach, Essam El-Zahar
      In this paper, the Adomian decomposition method (ADM) is proposed to solve the hyperbolic Kepler equation which is often used to describe the eccentric anomaly of a comet of extrasolar origin in its hyperbolic trajectory past the Sun. A convenient method is therefore needed to solve this equation to accurately determine the radial distance and/or the Cartesian coordinates of the comet. It has been shown that Adomian's series using a few terms are sufficient to achieve extremely accurate numerical results even for much higher values of eccentricity than those in the literature. Besides, an exceptionally rapid rate of convergence of the sequence of the obtained approximate solutions has been demonstrated. Such approximate solutions possess the odd property in the mean anomaly which are illustrated through several plots. Moreover, the absolute remainder error, using only three components of Adomian's solution decreases across a specified domain, approaches zero as the eccentric anomaly tends to infinity. Also, the absolute remainder error decreases by increasing the number of components of the Adomian decomposition series. In view of the obtained results, the present method may be the most effective approach to treat the hyperbolic Kepler equation.

      PubDate: 2017-05-25T20:18:08Z
      DOI: 10.1016/j.actaastro.2017.05.006
      Issue No: Vol. 138 (2017)
  • Predictor-corrector entry guidance with waypoint and no-fly zone
    • Authors: Tao Wang; Hongbo Zhang; Guojian Tang
      Pages: 10 - 18
      Abstract: Publication date: September 2017
      Source:Acta Astronautica, Volume 138
      Author(s): Tao Wang, Hongbo Zhang, Guojian Tang
      With the requirement of the future entry mission, the guidance method not only needs to be robust, reliable and autonomous, but also needs to have the ability to meet the constraints of no-fly zone and waypoint. The paper proposes a predictor-corrector entry guidance method that satisfies the constraints of no-fly zone and waypoint. The trajectory prediction is realized by numerical integration and the corrector is based on fuzzy logic. No-fly zones and waypoints are transformed to a series of reference points. For each reference point, one bank angle reversal is designed. The attack angle, the magnitude and reversal times of bank angle are cooperatively corrected to meet all constraints. The proposed method can guide longitudinal motion and lateral motion synergistically, so it is more robust and flexible. Only one bank angle reversal is needed for a no-fly zone or waypoint, so the reversal times are few. Moreover, without iteration, only a single trajectory prediction is required in a correction cycle, which is favorable for on-board calculation.

      PubDate: 2017-05-31T03:05:39Z
      DOI: 10.1016/j.actaastro.2017.05.009
      Issue No: Vol. 138 (2017)
  • Concurrent rendezvous control of underactuated spacecraft
    • Authors: Vijay Muralidharan; M. Reza Emami
      Pages: 28 - 42
      Abstract: Publication date: September 2017
      Source:Acta Astronautica, Volume 138
      Author(s): Vijay Muralidharan, M. Reza Emami
      The concurrent control of spacecraft equipped with one-axis unilateral thruster and three-axis attitude actuator is considered in this paper. The proposed control law utilizes attitude control channels along with the single thrust force concurrently, for three-dimensional trajectory tracking and rendezvous with a target object. The concurrent controller also achieves orbital transfer to low Earth orbits with long range separation. To demonstrate the orbit transfer capabilities of the concurrent controller, a smooth elliptical orbit transfer trajectory for co-planar circular orbits is designed. The velocity change and energy consumption of the designed orbit transfer trajectory is observed to be equivalent to that of Hohmann transfer.

      PubDate: 2017-05-31T03:05:39Z
      DOI: 10.1016/j.actaastro.2017.05.003
      Issue No: Vol. 138 (2017)
  • Mars Colony in situ resource utilization: An integrated architecture and
           economics model
    • Authors: Robert Shishko; René Fradet; Sydney Do; Serkan Saydam; Carlos Tapia-Cortez; Andrew G. Dempster; Jeff Coulton
      Pages: 53 - 67
      Abstract: Publication date: September 2017
      Source:Acta Astronautica, Volume 138
      Author(s): Robert Shishko, René Fradet, Sydney Do, Serkan Saydam, Carlos Tapia-Cortez, Andrew G. Dempster, Jeff Coulton
      This paper reports on our effort to develop an ensemble of specialized models to explore the commercial potential of mining water/ice on Mars in support of a Mars Colony. This ensemble starts with a formal systems architecting framework to describe a Mars Colony and capture its artifacts' parameters and technical attributes. The resulting database is then linked to a variety of “downstream” analytic models. In particular, we integrated an extraction process (i.e., “mining”) model, a simulation of the colony's environmental control and life support infrastructure known as HabNet, and a risk-based economics model. The mining model focuses on the technologies associated with in situ resource extraction, processing, storage and handling, and delivery. This model computes the production rate as a function of the systems' technical parameters and the local Mars environment. HabNet simulates the fundamental sustainability relationships associated with establishing and maintaining the colony's population. The economics model brings together market information, investment and operating costs, along with measures of market uncertainty and Monte Carlo techniques, with the objective of determining the profitability of commercial water/ice in situ mining operations. All told, over 50 market and technical parameters can be varied in order to address “what-if” questions, including colony location.

      PubDate: 2017-05-31T03:05:39Z
      DOI: 10.1016/j.actaastro.2017.05.024
      Issue No: Vol. 138 (2017)
  • Absolute navigation for Mars final approach using relative measurements of
           X-ray pulsars and Mars orbiter
    • Authors: Shuo Wang; Pingyuan Cui; Ai Gao; Zhengshi Yu; Menglong Cao
      Pages: 68 - 78
      Abstract: Publication date: September 2017
      Source:Acta Astronautica, Volume 138
      Author(s): Shuo Wang, Pingyuan Cui, Ai Gao, Zhengshi Yu, Menglong Cao
      To achieve a precise Mars landing, the autonomous navigation performance of Mars final approach phase need to be further improved. In this paper, an absolute navigation scheme for Mars finial approach phase using relative measurements of X-ray pulsars and Mars orbiter is proposed. By introducing the difference of time of arrival (DTOA) measurement, the states of approach spacecraft and orbiter are estimated at the same time. Compared to the navigation scheme based on the absolute measurements of pulsars, the error sources such as planetary ephemeris error, pulsar parameter uncertainties, and radio beacon position deviations, are correspondingly reduced or eliminated. Through observability analysis, the method of absolute navigation using relative information is proved observable under the condition of reasonable pulsars selection. The design optimization of beacon configuration based on the Fisher Information Matrix (FIM) is also carried out for achieving a better observability. Two navigation schemes respectively based on the absolute/relative measurements of X-ray pulsars are compared by numerical simulations, and the navigation performance is assessed and the feasibility of the proposed scheme is verified.

      PubDate: 2017-05-31T03:05:39Z
      DOI: 10.1016/j.actaastro.2017.05.017
      Issue No: Vol. 138 (2017)
  • Experimental investigation on laser-induced plasma ignition of hydrocarbon
           fuel in scramjet engine at takeover flight conditions
    • Authors: Xipeng Li; Weidong Liu; Yu Pan; Leichao Yang; Bin An
      Pages: 79 - 84
      Abstract: Publication date: September 2017
      Source:Acta Astronautica, Volume 138
      Author(s): Xipeng Li, Weidong Liu, Yu Pan, Leichao Yang, Bin An
      Laser-induced plasma ignition of an ethylene fuelled cavity is successfully conducted in a model scramjet engine combustor with dual cavities. The simulated flight condition corresponds to takeover flight Mach 4, with isolator entrance Mach number of 2.1, the total pressure of 0.65 MPa and stagnation temperature of 947 K. Ethylene is injected 35 mm upstream of cavity flameholder from four orifices with 2-mm-diameter. The 1064 nm laser beam, from a Q-switched Nd:YAG laser source running at 10 Hz and 940 mJ per pulse, is focused into cavity for ignition. High speed photography is used to capture the transient ignition process. The laser-induced gas breakdown, flame kernel generation and propagation are all recorded and ensuing stable supersonic combustion is established in cavity. The highly ionized plasma zone is almost round at starting, and then the surface of the flame kernel is wrinkled severely in 150 μs after the laser pulse due to the strong turbulence flow in cavity. The flame kernel is found rotating anti-clockwise and gradually moves upstream as the entrainment of circulation flow in cavity. The flame is stabilized at the corner of the cavity for about 200 μs, and then spreads from leading edge to trailing edge via the under part of shear layer to fully fill the entire cavity. The corner recirculation zone of cavity is of great importance for flame spreading. Eventually, a cavity shear-layer stabilized combustion is established in the supersonic flow roughly 2.9 ms after the laser pulse. Both the temporal evolution of normalized chemiluminescence intensity and normalized flame area show that the entire ignition process can be divided into four stages, which are referred as turbulent dissipation stage, combustion enhancement stage, reverting stage and combustion stabilization stage. The results show promising potentials of laser induced plasma for ignition in real scramjets.

      PubDate: 2017-06-05T03:08:17Z
      DOI: 10.1016/j.actaastro.2017.05.036
      Issue No: Vol. 138 (2017)
  • Inertial frames and breakthrough propulsion physics
    • Authors: Marc G. Millis
      Pages: 85 - 94
      Abstract: Publication date: September 2017
      Source:Acta Astronautica, Volume 138
      Author(s): Marc G. Millis
      The term “Breakthrough Propulsion Physics” comes from the NASA project by that name which examined non-rocket space drives, gravity control, and faster-than-light travel. The focus here is on space drives and the related unsolved physics of inertial frames. A “space drive” is a generic term encompassing any concept for using as-yet undiscovered physics to move a spacecraft instead of existing rockets, sails, or tethers. The collective state of the art spans mostly steps 1–3 of the scientific method: defining the problem, collecting data, and forming hypotheses. The key issues include (1) conservation of momentum, (2) absence of obvious reaction mass, and (3) the net-external thrusting requirement. Relevant open problems in physics include: (1) the sources and mechanisms of inertial frames, (2) coupling of gravitation to the other fundamental forces, and (3) the nature of the quantum vacuum. Rather than following the assumption that inertial frames are an immutable, intrinsic property of space, this paper revisits Mach's Principle, where it is posited that inertia is relative to the distant surrounding matter. This perspective allows conjectures that a space drive could impart reaction forces to that matter, via some as-yet undiscovered interaction with the inertial frame properties of space. Thought experiments are offered to begin a process to derive new hypotheses. It is unknown if this line of inquiry will be fruitful, but it is hoped that, by revisiting unsolved physics from a propulsion point of view, new insights will be gained.

      PubDate: 2017-06-05T03:08:17Z
      DOI: 10.1016/j.actaastro.2017.05.028
      Issue No: Vol. 138 (2017)
  • Extending the coverage of the internet of things with low-cost
           nanosatellite networks
    • Authors: Vicente Almonacid; Laurent Franck
      Pages: 95 - 101
      Abstract: Publication date: September 2017
      Source:Acta Astronautica, Volume 138
      Author(s): Vicente Almonacid, Laurent Franck
      Recent technology advances have made CubeSats not only an affordable means of access to space, but also promising platforms to develop a new variety of space applications. In this paper, we explore the idea of using nanosatellites as access points to provide extended coverage to the Internet of Things (IoT) and Machine-to-Machine (M2M) communications. This study is mainly motivated by two facts: on the one hand, it is already obvious that the number of machine-type devices deployed globally will experiment an exponential growth over the forthcoming years. This trend is pushed by the available terrestrial cellular infrastructure, which allows adding support for M2M connectivity at marginal costs. On the other hand, the same growth is not observed in remote areas that must rely on space-based connectivity. In such environments, the demand for M2M communications is potentially large, yet it is challenged by the lack of cost-effective service providers. The traffic characteristics of typical M2M applications translate into the requirement for an extremely low cost per transmitted message. Under these strong economical constraints, we expect that nanosatellites in the low Earth orbit will play a fundamental role in overcoming what we may call the IoT digital divide. The objective of this paper is therefore to provide a general analysis of a nanosatellite-based, global IoT/M2M network. We put emphasis in the engineering challenges faced in designing the Earth-to-Space communication link, where the adoption of an efficient multiple-access scheme is paramount for ensuring connectivity to a large number of terminal nodes. In particular, the trade-offs energy efficiency–access delay and energy efficiency–throughput are discussed, and a novel access approach suitable for delay-tolerant applications is proposed. Thus, by keeping a system-level standpoint, we identify key issues and discuss perspectives towards energy efficient and cost-effective solutions.

      PubDate: 2017-06-05T03:08:17Z
      DOI: 10.1016/j.actaastro.2017.05.030
      Issue No: Vol. 138 (2017)
  • The Lunar Space Tug: A sustainable bridge between low Earth orbits and
           the Cislunar Habitat
    • Authors: M. Mammarella; C.A. Paissoni; N. Viola; A. Denaro; E. Gargioli; F. Massobrio
      Pages: 102 - 117
      Abstract: Publication date: September 2017
      Source:Acta Astronautica, Volume 138
      Author(s): M. Mammarella, C.A. Paissoni, N. Viola, A. Denaro, E. Gargioli, F. Massobrio
      The International Space Station is the first space human outpost and over the last 15 years, it has represented a peculiar environment where science, technology and human innovation converge together in a unique microgravity and space research laboratory. With the International Space Station entering the second part of its life and its operations running steadily at nominal pace, the global space community is starting planning how the human exploration could move further, beyond Low-Earth-Orbit. According to the Global Exploration Roadmap, the Moon represents the next feasible path-way for advances in human exploration towards the nal goal, Mars. Based on the experience of the ISS, one of the most widespread ideas is to develop a Cislunar Station in preparation of long duration missions in a deep space environment. Cislunar space is de ned as the area of deep space under the influence of Earth-Moon system, including a set of special orbits, e.g. Earth-Moon Libration points and Lunar Retrograde Orbit. This habitat represents a suitable environment for demonstrating and testing technologies and capabilities in deep space. In order to achieve this goal, there are several crucial systems and technologies, in particular related to transportation and launch systems. The Orion Multi-Purpose Crew Vehicle is a reusable transportation capsule designed to provide crew transportation in deep space missions, whereas NASA is developing the Space Launch System, the most powerful rocket ever built, which could provide the necessary heavy-lift launch capability to support the same kind of missions. These innovations would allow quite-fast transfers from Earth to the Cislunar Station and vice versa, both for manned and unmanned missions. However, taking into account the whole Concept of Operations for both the growth and sustainability of the Cislunar Space Station, the Lunar Space Tug can be considered as an additional, new and fundamental element for the mission architecture. The Lunar Space Tug represents an alternative to the SLS scenario, especially for what concerns all unmanned or logistic missions (e.g. cargo transfer, on orbit assembly, samples return), from Low Earth Orbit to Cislunar space. The paper focuses on the mission analysis and conceptual design of the Lunar Space Tug to support the growth and sustainment of the Cislunar Station. Particular attention is dedicated to the analysis of the propulsion subsystem effects of the Lunar Space Tug design. Main results are presented and discussed, and main conclusions are drawn.

      PubDate: 2017-06-05T03:08:17Z
      DOI: 10.1016/j.actaastro.2017.05.034
      Issue No: Vol. 138 (2017)
  • Ignition and combustion characteristics of molded amorphous boron under
           different oxygen pressures
    • Authors: Daolun Liang; Jianzhong Liu; Yunan Zhou; Junhu Zhou; Kefa Cen
      Pages: 118 - 128
      Abstract: Publication date: September 2017
      Source:Acta Astronautica, Volume 138
      Author(s): Daolun Liang, Jianzhong Liu, Yunan Zhou, Junhu Zhou, Kefa Cen
      Ignition and combustion characteristics of amorphous boron (B) have received much attention from researchers in recent decades. A pressurized concentrated ignition experimental system was designed to evaluate the ignition and combustion characteristics of molded B samples. The ignition experiments were carried out under different oxygen pressures (1–9 atm). The condensed combustion products were then analyzed using a scanning electron microscope, an X-ray energy dispersive spectrometer, and an X-ray diffractometer. Furthermore, the complete oxidation rates of the samples were detected by inductively coupled plasma chromatography. As the oxygen pressure increased, the combustion intensity of the samples steadily increased, and the ignition delay time and combustion time both decreased. Under the oxygen pressure of 9 atm, the average ignition delay time and combustion time were 2640 ms and 2596 ms, respectively, and the highest combustion temperature reached 1561.5 °C. The initial diffusion flame on the sample surface was green and the brightest, which was produced by an intermediate combustion product, BO2 (corresponding molecular emission spectrum wavelength, 547.3 nm). Emission spectra of another intermediate product, BO (431.9 nm) was also detected. Two different types of structures were found in the condensed combustion products of the samples. The first type was the flaky B2O3 structure, and the second type was the flocculent structure of incomplete combustion products. The B2O3 content in the condensed combustion products increased with the oxygen pressure during combustion. The complete oxidation ratio of the samples also increased with the oxygen pressure, and reached the maximum value of 68.71% under 9 atm. Overall, the samples showed better ignition and combustion characteristics under higher oxygen pressure.

      PubDate: 2017-06-05T03:08:17Z
      DOI: 10.1016/j.actaastro.2017.05.019
      Issue No: Vol. 138 (2017)
  • Experimental validation of damping properties and solar pressure effects
           on flexible, high area-to-mass ratio debris model
    • Authors: Sittiporn Channumsin; Matteo Ceriotti; Gianmarco Radice; Ian Watson
      Pages: 129 - 144
      Abstract: Publication date: September 2017
      Source:Acta Astronautica, Volume 138
      Author(s): Sittiporn Channumsin, Matteo Ceriotti, Gianmarco Radice, Ian Watson
      Multilayer insulation (MLI) is a recently-discovered type of debris originating from delamination of aging spacecraft; it is mostly detected near the geosynchronous orbit (GEO). Observation data indicates that these objects are characterised by high reflectivity, high area-to-mass ratio (HAMR), fast rotation, high sensitivity to perturbations (especially solar radiation pressure) and change of area-to-mass ratio (AMR) over time. As a result, traditional models (e.g. cannonball) are unsuitable to represent and predict this debris' orbital evolution. Previous work by the authors effectively modelled the flexible debris by means of multibody dynamics to improve the prediction accuracy. The orbit evolution with the flexible model resulted significantly different from using the rigid model. This paper aims to present a methodology to determine the dynamic properties of thin membranes with the purpose to validate the deformation characteristics of the flexible model. A high-vacuum chamber (10−4 mbar) to significantly decrease air friction, inside which a thin membrane is hinged at one end but free at the other provides the experimental setup. A free motion test is used to determine the damping characteristics and natural frequency of the thin membrane via logarithmic decrement and frequency response. The membrane can swing freely in the chamber and the motion is tracked by a static, optical camera, and a Kalman filter technique is implemented in the tracking algorithm to reduce noise and increase the tracking accuracy of the oscillating motion. Then, the effect of solar radiation pressure on the thin membrane is investigated: a high power spotlight (500–2000 W) is used to illuminate the sample and any displacement of the membrane is measured by means of a high-resolution laser sensor. Analytic methods from the natural frequency response and Finite Element Analysis (FEA) including multibody simulations of both experimental setups are used for the validation of the flexible model by comparing the experimental results of amplitude decay, natural frequencies and deformation. The experimental results show good agreement with both analytical results and finite element methods.

      PubDate: 2017-06-10T03:14:30Z
      DOI: 10.1016/j.actaastro.2017.05.015
      Issue No: Vol. 138 (2017)
School of Mathematical and Computer Sciences
Heriot-Watt University
Edinburgh, EH14 4AS, UK
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Fax: +00 44 (0)131 4513327
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