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Showing 1 - 200 of 3175 Journals sorted alphabetically
A Practical Logic of Cognitive Systems     Full-text available via subscription   (Followers: 9)
AASRI Procedia     Open Access   (Followers: 14)
Academic Pediatrics     Hybrid Journal   (Followers: 28, SJR: 1.402, h-index: 51)
Academic Radiology     Hybrid Journal   (Followers: 22, SJR: 1.008, h-index: 75)
Accident Analysis & Prevention     Partially Free   (Followers: 90, SJR: 1.109, h-index: 94)
Accounting Forum     Hybrid Journal   (Followers: 25, SJR: 0.612, h-index: 27)
Accounting, Organizations and Society     Hybrid Journal   (Followers: 33, SJR: 2.515, h-index: 90)
Achievements in the Life Sciences     Open Access   (Followers: 5)
Acta Anaesthesiologica Taiwanica     Open Access   (Followers: 6, SJR: 0.338, h-index: 19)
Acta Astronautica     Hybrid Journal   (Followers: 376, SJR: 0.726, h-index: 43)
Acta Automatica Sinica     Full-text available via subscription   (Followers: 2)
Acta Biomaterialia     Hybrid Journal   (Followers: 27, SJR: 2.02, h-index: 104)
Acta Colombiana de Cuidado Intensivo     Full-text available via subscription   (Followers: 2)
Acta de Investigación Psicológica     Open Access   (Followers: 3)
Acta Ecologica Sinica     Open Access   (Followers: 8, SJR: 0.172, h-index: 29)
Acta Haematologica Polonica     Free   (Followers: 1, SJR: 0.123, h-index: 8)
Acta Histochemica     Hybrid Journal   (Followers: 3, SJR: 0.604, h-index: 38)
Acta Materialia     Hybrid Journal   (Followers: 236, SJR: 3.683, h-index: 202)
Acta Mathematica Scientia     Full-text available via subscription   (Followers: 5, SJR: 0.615, h-index: 21)
Acta Mechanica Solida Sinica     Full-text available via subscription   (Followers: 9, SJR: 0.442, h-index: 21)
Acta Oecologica     Hybrid Journal   (Followers: 10, SJR: 0.915, h-index: 53)
Acta Otorrinolaringologica (English Edition)     Full-text available via subscription  
Acta Otorrinolaringológica Española     Full-text available via subscription   (Followers: 2, SJR: 0.311, h-index: 16)
Acta Pharmaceutica Sinica B     Open Access   (Followers: 1)
Acta Poética     Open Access   (Followers: 4)
Acta Psychologica     Hybrid Journal   (Followers: 25, 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: 3)
Actas Dermo-Sifiliográficas (English Edition)     Full-text available via subscription   (Followers: 2)
Actas Urológicas Españolas     Full-text available via subscription   (Followers: 3, SJR: 0.383, h-index: 19)
Actas Urológicas Españolas (English Edition)     Full-text available via subscription   (Followers: 1)
Actualites Pharmaceutiques     Full-text available via subscription   (Followers: 6, SJR: 0.141, h-index: 3)
Actualites Pharmaceutiques Hospitalieres     Full-text available via subscription   (Followers: 3, SJR: 0.112, h-index: 2)
Acupuncture and Related Therapies     Hybrid Journal   (Followers: 6)
Acute Pain     Full-text available via subscription   (Followers: 14)
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: 7)
Additive Manufacturing     Hybrid Journal   (Followers: 9, SJR: 1.039, h-index: 5)
Additives for Polymers     Full-text available via subscription   (Followers: 22)
Advanced Cement Based Materials     Full-text available via subscription   (Followers: 3)
Advanced Drug Delivery Reviews     Hybrid Journal   (Followers: 132, 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: 8, SJR: 0.299, h-index: 15)
Advances in Agronomy     Full-text available via subscription   (Followers: 12, SJR: 2.071, h-index: 82)
Advances in Anesthesia     Full-text available via subscription   (Followers: 27, SJR: 0.169, h-index: 4)
Advances in Antiviral Drug Design     Full-text available via subscription   (Followers: 2)
Advances in Applied Mathematics     Full-text available via subscription   (Followers: 10, 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: 14, 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: 2, SJR: 0.619, h-index: 48)
Advances in Cancer Research     Full-text available via subscription   (Followers: 28, SJR: 2.215, h-index: 78)
Advances in Carbohydrate Chemistry and Biochemistry     Full-text available via subscription   (Followers: 7, SJR: 0.9, h-index: 30)
Advances in Catalysis     Full-text available via subscription   (Followers: 5, SJR: 2.139, h-index: 42)
Advances in Cell Aging and Gerontology     Full-text available via subscription   (Followers: 3)
Advances in Cellular and Molecular Biology of Membranes and Organelles     Full-text available via subscription   (Followers: 12)
Advances in Chemical Engineering     Full-text available via subscription   (Followers: 27, SJR: 0.183, h-index: 23)
Advances in Child Development and Behavior     Full-text available via subscription   (Followers: 10, SJR: 0.665, h-index: 29)
Advances in Chronic Kidney Disease     Full-text available via subscription   (Followers: 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: 19, SJR: 2.314, h-index: 130)
Advances in Computers     Full-text available via subscription   (Followers: 14, SJR: 0.223, h-index: 22)
Advances in Dermatology     Full-text available via subscription   (Followers: 14)
Advances in Developmental Biology     Full-text available via subscription   (Followers: 10)
Advances in Digestive Medicine     Open Access   (Followers: 8)
Advances in DNA Sequence-Specific Agents     Full-text available via subscription   (Followers: 5)
Advances in Drug Research     Full-text available via subscription   (Followers: 21)
Advances in Ecological Research     Full-text available via subscription   (Followers: 42, SJR: 3.25, h-index: 43)
Advances in Engineering Software     Hybrid Journal   (Followers: 27, SJR: 0.486, h-index: 10)
Advances in Experimental Biology     Full-text available via subscription   (Followers: 6)
Advances in Experimental Social Psychology     Full-text available via subscription   (Followers: 42, SJR: 5.465, h-index: 64)
Advances in Exploration Geophysics     Full-text available via subscription   (Followers: 1)
Advances in Fluorine Science     Full-text available via subscription   (Followers: 7)
Advances in Food and Nutrition Research     Full-text available via subscription   (Followers: 53, 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: 7)
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: 9, SJR: 0.497, h-index: 31)
Advances in Human Factors/Ergonomics     Full-text available via subscription   (Followers: 23)
Advances in Imaging and Electron Physics     Full-text available via subscription   (Followers: 2, SJR: 0.396, h-index: 27)
Advances in Immunology     Full-text available via subscription   (Followers: 36, SJR: 4.152, h-index: 85)
Advances in Inorganic Chemistry     Full-text available via subscription   (Followers: 8, SJR: 1.132, h-index: 42)
Advances in Insect Physiology     Full-text available via subscription   (Followers: 2, SJR: 1.274, h-index: 27)
Advances in Integrative Medicine     Hybrid Journal   (Followers: 6)
Advances in Intl. Accounting     Full-text available via subscription   (Followers: 3)
Advances in Life Course Research     Hybrid Journal   (Followers: 8, SJR: 0.764, h-index: 15)
Advances in Lipobiology     Full-text available via subscription   (Followers: 1)
Advances in Magnetic and Optical Resonance     Full-text available via subscription   (Followers: 9)
Advances in Marine Biology     Full-text available via subscription   (Followers: 14, 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: 21)
Advances in Molecular and Cellular Endocrinology     Full-text available via subscription   (Followers: 8)
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: 3)
Advances in Oncobiology     Full-text available via subscription   (Followers: 1)
Advances in Organ Biology     Full-text available via subscription   (Followers: 1)
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: 6, SJR: 0.148, h-index: 11)
Advances in Parasitology     Full-text available via subscription   (Followers: 5, 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: 10)
Advances in Pharmacology     Full-text available via subscription   (Followers: 15, SJR: 1.718, h-index: 58)
Advances in Physical Organic Chemistry     Full-text available via subscription   (Followers: 8, SJR: 0.384, h-index: 26)
Advances in Phytomedicine     Full-text available via subscription  
Advances in Planar Lipid Bilayers and Liposomes     Full-text available via subscription   (Followers: 3, SJR: 0.248, h-index: 11)
Advances in Plant Biochemistry and Molecular Biology     Full-text available via subscription   (Followers: 7)
Advances in Plant Pathology     Full-text available via subscription   (Followers: 5)
Advances in Porous Media     Full-text available via subscription   (Followers: 5)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 17)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 18, SJR: 1.5, h-index: 62)
Advances in Psychology     Full-text available via subscription   (Followers: 59)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 6, SJR: 0.478, h-index: 32)
Advances in Radiation Oncology     Open Access  
Advances in Small Animal Medicine and Surgery     Hybrid Journal   (Followers: 3, SJR: 0.1, h-index: 2)
Advances in Space Biology and Medicine     Full-text available via subscription   (Followers: 5)
Advances in Space Research     Full-text available via subscription   (Followers: 375, SJR: 0.606, h-index: 65)
Advances in Structural Biology     Full-text available via subscription   (Followers: 5)
Advances in Surgery     Full-text available via subscription   (Followers: 9, SJR: 0.823, h-index: 27)
Advances in the Study of Behavior     Full-text available via subscription   (Followers: 29, SJR: 1.321, h-index: 56)
Advances in Veterinary Medicine     Full-text available via subscription   (Followers: 17)
Advances in Veterinary Science and Comparative Medicine     Full-text available via subscription   (Followers: 13)
Advances in Virus Research     Full-text available via subscription   (Followers: 5, SJR: 1.878, h-index: 68)
Advances in Water Resources     Hybrid Journal   (Followers: 46, SJR: 2.408, h-index: 94)
Aeolian Research     Hybrid Journal   (Followers: 6, SJR: 0.973, h-index: 22)
Aerospace Science and Technology     Hybrid Journal   (Followers: 333, SJR: 0.816, h-index: 49)
AEU - Intl. J. of Electronics and Communications     Hybrid Journal   (Followers: 8, SJR: 0.318, h-index: 36)
African J. of Emergency Medicine     Open Access   (Followers: 6, SJR: 0.344, h-index: 6)
Ageing Research Reviews     Hybrid Journal   (Followers: 9, SJR: 3.289, h-index: 78)
Aggression and Violent Behavior     Hybrid Journal   (Followers: 429, 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: 31, SJR: 1.275, h-index: 74)
Agricultural Water Management     Hybrid Journal   (Followers: 43, SJR: 1.546, h-index: 79)
Agriculture and Agricultural Science Procedia     Open Access   (Followers: 1)
Agriculture and Natural Resources     Open Access   (Followers: 2)
Agriculture, Ecosystems & Environment     Hybrid Journal   (Followers: 56, SJR: 1.879, h-index: 120)
Ain Shams Engineering J.     Open Access   (Followers: 5, SJR: 0.434, h-index: 14)
Air Medical J.     Hybrid Journal   (Followers: 5, SJR: 0.234, h-index: 18)
AKCE Intl. J. of Graphs and Combinatorics     Open Access   (SJR: 0.285, h-index: 3)
Alcohol     Hybrid Journal   (Followers: 11, SJR: 0.922, h-index: 66)
Alcoholism and Drug Addiction     Open Access   (Followers: 9)
Alergologia Polska : Polish J. of Allergology     Full-text available via subscription   (Followers: 1)
Alexandria Engineering J.     Open Access   (Followers: 1, SJR: 0.436, h-index: 12)
Alexandria J. of Medicine     Open Access   (Followers: 1)
Algal Research     Partially Free   (Followers: 9, SJR: 2.05, h-index: 20)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 2)
Allergologia et Immunopathologia     Full-text available via subscription   (Followers: 1, SJR: 0.46, h-index: 29)
Allergology Intl.     Open Access   (Followers: 5, SJR: 0.776, h-index: 35)
Alpha Omegan     Full-text available via subscription   (SJR: 0.121, h-index: 9)
ALTER - European J. of Disability Research / Revue Européenne de Recherche sur le Handicap     Full-text available via subscription   (Followers: 9, SJR: 0.158, h-index: 9)
Alzheimer's & Dementia     Hybrid Journal   (Followers: 48, SJR: 4.289, h-index: 64)
Alzheimer's & Dementia: Diagnosis, Assessment & Disease Monitoring     Open Access   (Followers: 4)
Alzheimer's & Dementia: Translational Research & Clinical Interventions     Open Access   (Followers: 4)
Ambulatory Pediatrics     Hybrid Journal   (Followers: 6)
American Heart J.     Hybrid Journal   (Followers: 50, SJR: 3.157, h-index: 153)
American J. of Cardiology     Hybrid Journal   (Followers: 50, SJR: 2.063, h-index: 186)
American J. of Emergency Medicine     Hybrid Journal   (Followers: 42, SJR: 0.574, h-index: 65)
American J. of Geriatric Pharmacotherapy     Full-text available via subscription   (Followers: 10, SJR: 1.091, h-index: 45)
American J. of Geriatric Psychiatry     Hybrid Journal   (Followers: 14, SJR: 1.653, h-index: 93)
American J. of Human Genetics     Hybrid Journal   (Followers: 31, SJR: 8.769, h-index: 256)
American J. of Infection Control     Hybrid Journal   (Followers: 26, SJR: 1.259, h-index: 81)
American J. of Kidney Diseases     Hybrid Journal   (Followers: 32, SJR: 2.313, h-index: 172)
American J. of Medicine     Hybrid Journal   (Followers: 42, 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: 189, SJR: 2.255, h-index: 171)
American J. of Ophthalmology     Hybrid Journal   (Followers: 62, SJR: 2.803, h-index: 148)
American J. of Ophthalmology Case Reports     Open Access   (Followers: 6)
American J. of Orthodontics and Dentofacial Orthopedics     Full-text available via subscription   (Followers: 6, SJR: 1.249, h-index: 88)
American J. of Otolaryngology     Hybrid Journal   (Followers: 25, SJR: 0.59, h-index: 45)
American J. of Pathology     Hybrid Journal   (Followers: 27, SJR: 2.653, h-index: 228)
American J. of Preventive Medicine     Hybrid Journal   (Followers: 27, SJR: 2.764, h-index: 154)
American J. of Surgery     Hybrid Journal   (Followers: 37, SJR: 1.286, h-index: 125)
American J. of the Medical Sciences     Hybrid Journal   (Followers: 12, SJR: 0.653, h-index: 70)
Ampersand : An Intl. J. of General and Applied Linguistics     Open Access   (Followers: 6)
Anaerobe     Hybrid Journal   (Followers: 4, SJR: 1.066, h-index: 51)
Anaesthesia & Intensive Care Medicine     Full-text available via subscription   (Followers: 61, SJR: 0.124, h-index: 9)
Anaesthesia Critical Care & Pain Medicine     Full-text available via subscription   (Followers: 14)
Anales de Cirugia Vascular     Full-text available via subscription  
Anales de Pediatría     Full-text available via subscription   (Followers: 2, SJR: 0.209, h-index: 27)
Anales de Pediatría (English Edition)     Full-text available via subscription  
Anales de Pediatría Continuada     Full-text available via subscription   (SJR: 0.104, h-index: 3)
Analytic Methods in Accident Research     Hybrid Journal   (Followers: 4, SJR: 2.577, h-index: 7)
Analytica Chimica Acta     Hybrid Journal   (Followers: 39, SJR: 1.548, h-index: 152)
Analytical Biochemistry     Hybrid Journal   (Followers: 164, SJR: 0.725, h-index: 154)
Analytical Chemistry Research     Open Access   (Followers: 10, 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   (Followers: 1)

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Journal Cover Acta Astronautica
  [SJR: 0.726]   [H-I: 43]   [376 followers]  Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0094-5765
   Published by Elsevier Homepage  [3175 journals]
  • Speed-constrained three-axes attitude control using kinematic steering
    • Authors: Hanspeter Schaub; Scott Piggott
      Pages: 1 - 8
      Abstract: Publication date: June 2018
      Source:Acta Astronautica, Volume 147
      Author(s): Hanspeter Schaub, Scott Piggott
      Spacecraft attitude control solutions typically are torque-level algorithms that simultaneously control both the attitude and angular velocity tracking errors. In contrast, robotic control solutions are kinematic steering commands where rates are treated as the control variable, and a servo-tracking control subsystem is present to achieve the desired control rates. In this paper kinematic attitude steering controls are developed where an outer control loop establishes a desired angular response history to a tracking error, and an inner control loop tracks the commanded body angular rates. The overall stability relies on the separation principle of the inner and outer control loops which must have sufficiently different response time scales. The benefit is that the outer steering law response can be readily shaped to a desired behavior, such as limiting the approach angular velocity when a large tracking error is corrected. A Modified Rodrigues Parameters implementation is presented that smoothly saturates the speed response. A robust nonlinear body rate servo loop is developed which includes integral feedback. This approach provides a convenient modular framework that makes it simple to interchange outer and inner control loops to readily setup new control implementations. Numerical simulations illustrate the expected performance for an aggressive reorientation maneuver subject to an unknown external torque.

      PubDate: 2018-04-12T08:29:20Z
      DOI: 10.1016/j.actaastro.2018.03.022
      Issue No: Vol. 147 (2018)
  • Design and landing dynamic analysis of reusable landing leg for a
           near-space manned capsule
    • Authors: Shuai Yue; Hong Nie; Ming Zhang; Xiaohui Wei; Shengyong Gan
      Pages: 9 - 26
      Abstract: Publication date: June 2018
      Source:Acta Astronautica, Volume 147
      Author(s): Shuai Yue, Hong Nie, Ming Zhang, Xiaohui Wei, Shengyong Gan
      To improve the landing performance of a near-space manned capsule under various landing conditions, a novel landing system is designed that employs double chamber and single chamber dampers in the primary and auxiliary struts, respectively. A dynamic model of the landing system is established, and the damper parameters are determined by employing the design method. A single-leg drop test with different initial pitch angles is then conducted to compare and validate the simulation model. Based on the validated simulation model, seven critical landing conditions regarding nine crucial landing responses are found by combining the radial basis function (RBF) surrogate model and adaptive simulated annealing (ASA) optimization method. Subsequently, the adaptability of the landing system under critical landing conditions is analyzed. The results show that the simulation effectively results match the test results, which validates the accuracy of the dynamic model. In addition, all of the crucial responses under their corresponding critical landing conditions satisfy the design specifications, demonstrating the feasibility of the landing system.

      PubDate: 2018-04-12T08:29:20Z
      DOI: 10.1016/j.actaastro.2018.02.043
      Issue No: Vol. 147 (2018)
  • Investigation on thermo-acoustic instability dynamic characteristics of
           hydrocarbon fuel flowing in scramjet cooling channel based on wavelet
           entropy method
    • Authors: Hao Zan; Haowei Li; Yuguang Jiang; Meng Wu; Weixing Zhou; Wen Bao
      Pages: 27 - 36
      Abstract: Publication date: June 2018
      Source:Acta Astronautica, Volume 147
      Author(s): Hao Zan, Haowei Li, Yuguang Jiang, Meng Wu, Weixing Zhou, Wen Bao
      As part of our efforts to find ways and means to further improve the regenerative cooling technology in scramjet, the experiments of thermo-acoustic instability dynamic characteristics of hydrocarbon fuel flowing have been conducted in horizontal circular tubes at different conditions. The experimental results indicate that there is a developing process from thermo-acoustic stability to instability. In order to have a deep understanding on the developing process of thermo-acoustic instability, the method of Multi-scale Shannon Wavelet Entropy (MSWE) based on Wavelet Transform Correlation Filter (WTCF) and Multi-Scale Shannon Entropy (MSE) is adopted in this paper. The results demonstrate that the developing process of thermo-acoustic instability from noise and weak signals is well detected by MSWE method and the differences among the stability, the developing process and the instability can be identified. These properties render the method particularly powerful for warning thermo-acoustic instability of hydrocarbon fuel flowing in scramjet cooling channels. The mass flow rate and the inlet pressure will make an influence on the developing process of the thermo-acoustic instability. The investigation on thermo-acoustic instability dynamic characteristics at supercritical pressure based on wavelet entropy method offers guidance on the control of scramjet fuel supply, which can secure stable fuel flowing in regenerative cooling system.

      PubDate: 2018-04-12T08:29:20Z
      DOI: 10.1016/j.actaastro.2018.03.015
      Issue No: Vol. 147 (2018)
  • Development of a hardware-in-the-loop testbed to demonstrate multiple
           spacecraft operations in proximity
    • Authors: Youngho Eun; Sang-Young Park; Geuk-Nam Kim
      Pages: 48 - 58
      Abstract: Publication date: June 2018
      Source:Acta Astronautica, Volume 147
      Author(s): Youngho Eun, Sang-Young Park, Geuk-Nam Kim
      This paper presents a new state-of-the-art ground-based hardware-in-the-loop test facility, which was developed to verify and demonstrate autonomous guidance, navigation, and control algorithms for space proximity operations and formation flying maneuvers. The test facility consists of two complete spaceflight simulators, an aluminum-based operational arena, and a set of infrared motion tracking cameras; thus, the testbed is capable of representing space activities under circumstances prevailing on the ground. The spaceflight simulators have a maximum of five-degree-of-freedom in a quasi-momentum-free environment, which is produced by a set of linear/hemispherical air-bearings and a horizontally leveled operational arena. The tracking system measures the real-time three-dimensional position and attitude to provide state variables to the agents. The design of the testbed is illustrated in detail for every element throughout the paper. The practical hardware characteristics of the active/passive measurement units and internal actuators are identified in detail from various perspectives. These experimental results support the successful development of the entire facility and enable us to implement and verify the spacecraft proximity operation strategy in the near future.

      PubDate: 2018-04-12T08:29:20Z
      DOI: 10.1016/j.actaastro.2018.03.030
      Issue No: Vol. 147 (2018)
  • Quasi-model free control for the post-capture operation of a
           non-cooperative target
    • Authors: Yuchen She; Jun Sun; Shuang Li; Wendan Li; Ting Song
      Pages: 59 - 70
      Abstract: Publication date: June 2018
      Source:Acta Astronautica, Volume 147
      Author(s): Yuchen She, Jun Sun, Shuang Li, Wendan Li, Ting Song
      This paper investigates a quasi-model free control (QMFC) approach for the post-capture control of a non-cooperative space object. The innovation of this paper lies in the following three aspects, which correspond to the three challenges presented in the mission scenario. First, an excitation-response mapping search strategy is developed based on the linearization of the system in terms of a set of parameters, which is efficient in handling the combined spacecraft with a high coupling effect on the inertia matrix. Second, a virtual coordinate system is proposed to efficiently compute the center of mass (COM) of the combined system, which improves the COM tracking efficiency for time-varying COM positions. Third, a linear online corrector is built to reduce the control error to further improve the control accuracy, which helps control the tracking mode within the combined system's time-varying inertia matrix. Finally, simulation analyses show that the proposed control framework is able to realize combined spacecraft post-capture control in extremely unfavorable conditions with high control accuracy.

      PubDate: 2018-04-12T08:29:20Z
      DOI: 10.1016/j.actaastro.2018.03.041
      Issue No: Vol. 147 (2018)
  • Orbital resonances of Taiwan’s FORMOSAT-2 remote sensing satellite
    • Authors: Shin-Fa Lin; Cheinway Hwang
      Pages: 71 - 85
      Abstract: Publication date: June 2018
      Source:Acta Astronautica, Volume 147
      Author(s): Shin-Fa Lin, Cheinway Hwang
      Unlike a typical remote sensing satellite that has a global coverage and non-integral orbital revolutions per day, Taiwan’s FORMOSAT-2 (FS-2) satellite has a non-global coverage due to the mission requirements of one-day repeat cycle and daily visit around Taiwan. These orbital characteristics result in an integer number of revolutions a day and orbital resonances caused by certain components of the Earth’s gravity field. Orbital flight data indicated amplified variations in the amplitudes of FS-2’s Keplerian elements. We use twelve years of orbital observations and maneuver data to analyze the cause of the resonances and explain the differences between the simulated (at the pre-launch stage) and real orbits of FS-2. The differences are quantified using orbital perturbation theories that describe secular and long-period orbital evolutions caused by resonances. The resonance-induced orbital rising rate of FS-2 reaches +1.425 m/day, due to the combined (modeled) effect of resonances and atmospheric drags (the relative modeling errors < 10%). The concave shapes in the time-evolution of the longitude of descending node (LonDN) coincide with the positive rates of daily semi-major axis (SMA) change, also caused by resonances. The non-zonal geopotential coefficients causing the resonance effects contributed up to 45% of FS-2’s inclination decline. Our retrospective analysis of FS-2’s resonant orbit can provide lessons for a remote sensing mission similar to FS-2, especially in the early mission design and planning phase.

      PubDate: 2018-04-12T08:29:20Z
      DOI: 10.1016/j.actaastro.2018.02.023
      Issue No: Vol. 147 (2018)
  • Autonomous assembly with collision avoidance of a fleet of flexible
           spacecraft based on disturbance observer
    • Authors: Ti Chen; Hao Wen
      Pages: 86 - 96
      Abstract: Publication date: June 2018
      Source:Acta Astronautica, Volume 147
      Author(s): Ti Chen, Hao Wen
      This paper presents a distributed control law with disturbance observer for the autonomous assembly of a fleet of flexible spacecraft to construct a large flexible space structure. The fleet of flexible spacecraft is driven to the pre-assembly configuration firstly, and then to the desired assembly configuration. A distributed assembly control law with disturbance observer is proposed by treating the flexible dynamics as disturbances acting on the rigid motion of the flexible spacecraft. Theoretical analysis shows that the control law can actuate the fleet to the desired configuration. Moreover, the collision avoidance between the members is also considered in the process from initial configuration to pre-assembly configuration. Finally, a numerical example is presented to verify the feasibility of proposed mission planning and the effectiveness of control law.

      PubDate: 2018-04-12T08:29:20Z
      DOI: 10.1016/j.actaastro.2018.03.027
      Issue No: Vol. 147 (2018)
  • Simulations of momentum transfer process between solar wind plasma and
           bias voltage tethers of electric sail thruster
    • Authors: Guangqing Xia; Yajie Han; Liuwei Chen; Yanming Wei; Yang Yu; Maolin Chen
      Pages: 107 - 113
      Abstract: Publication date: June 2018
      Source:Acta Astronautica, Volume 147
      Author(s): Guangqing Xia, Yajie Han, Liuwei Chen, Yanming Wei, Yang Yu, Maolin Chen
      The interaction between the solar wind plasma and the bias voltage of long tethers is the basic mechanism of the electric sail thruster. The momentum transfer process between the solar wind plasma and electric tethers was investigated using a 2D full particle PIC method. The coupled electric field distribution and deflected ion trajectory under different bias voltages were compared, and the influence of bias voltage on momentum transfer process was analyzed. The results show that the high potential of the bias voltage of long tethers will slow down, stagnate, reflect and deflect a large number of ions, so that ion cavities are formed in the vicinity of the tether, and the ions will transmit the axial momentum to the sail tethers to produce the thrust. Compared to the singe tether, double tethers show a better thrust performance.

      PubDate: 2018-04-12T08:29:20Z
      DOI: 10.1016/j.actaastro.2018.03.049
      Issue No: Vol. 147 (2018)
  • System analysis and test-bed for an atmosphere-breathing electric
           propulsion system using an inductive plasma thruster
    • Authors: F. Romano; B. Massuti-Ballester; T. Binder; G. Herdrich; S. Fasoulas; T. Schönherr
      Pages: 114 - 126
      Abstract: Publication date: June 2018
      Source:Acta Astronautica, Volume 147
      Author(s): F. Romano, B. Massuti-Ballester, T. Binder, G. Herdrich, S. Fasoulas, T. Schönherr
      Challenging space mission scenarios include those in low altitude orbits, where the atmosphere creates significant drag to the S/C and forces their orbit to an early decay. For drag compensation, propulsion systems are needed, requiring propellant to be carried on-board. An atmosphere-breathing electric propulsion system (ABEP) ingests the residual atmosphere particles through an intake and uses them as propellant for an electric thruster. Theoretically applicable to any planet with atmosphere, the system might allow to orbit for unlimited time without carrying propellant. A new range of altitudes for continuous operation would become accessible, enabling new scientific missions while reducing costs. Preliminary studies have shown that the collectible propellant flow for an ion thruster (in LEO) might not be enough, and that electrode erosion due to aggressive gases, such as atomic oxygen, will limit the thruster lifetime. In this paper an inductive plasma thruster (IPT) is considered for the ABEP system. The starting point is a small scale inductively heated plasma generator IPG6-S. These devices are electrodeless and have already shown high electric-to-thermal coupling efficiencies using O 2 and CO 2 . The system analysis is integrated with IPG6-S tests to assess mean mass-specific energies of the plasma plume and estimate exhaust velocities.

      PubDate: 2018-04-12T08:29:20Z
      DOI: 10.1016/j.actaastro.2018.03.031
      Issue No: Vol. 147 (2018)
  • Flame structure of methane/oxygen shear coaxial jet with velocity ratio
           using high-speed imaging and OH*, CH* chemiluminescence
    • Authors: Myungbo Shim; Kwanyoung Noh; Woongsup Yoon
      Pages: 127 - 132
      Abstract: Publication date: June 2018
      Source:Acta Astronautica, Volume 147
      Author(s): Myungbo Shim, Kwanyoung Noh, Woongsup Yoon
      In this study, the effects of gaseous methane/oxygen injection velocity ratio on the shear coaxial jet flame structure are analyzed using high-speed imaging along with OH* and CH* chemiluminescence. The images show that, as the velocity ratio is increased, the visual flame length increases and wrinkles of the flame front are developed further downstream. The region near the equivalence ratio 1 condition in the flame could be identified by the maximum OH* position, and this region is located further downstream as the velocity ratio is increased. The dominant CH* chemiluminescence is found in the near-injector region. As the velocity ratio is decreased, the signal intensity is higher at the same downstream distance in each flame. From the results, as the velocity ratio is decreased, there is increased entrainment of the external jet, the mixing of the two jets is enhanced, the region near the stoichiometric mixture condition is located further upstream, and consequently, the flame length decreases.

      PubDate: 2018-04-12T08:29:20Z
      DOI: 10.1016/j.actaastro.2018.03.053
      Issue No: Vol. 147 (2018)
  • Micromechanical analysis of composites with fibers distributed randomly
           over the transverse cross-section
    • Authors: Jingmeng Weng; Weidong Wen; Haitao Cui; Bo Chen
      Pages: 133 - 140
      Abstract: Publication date: June 2018
      Source:Acta Astronautica, Volume 147
      Author(s): Jingmeng Weng, Weidong Wen, Haitao Cui, Bo Chen
      A new method to generate the random distribution of fibers in the transverse cross-section of fiber reinforced composites with high fiber volume fraction is presented in this paper. Based on the microscopy observation of the transverse cross-sections of unidirectional composite laminates, hexagon arrangement is set as the initial arrangement status, and the initial velocity of each fiber is arbitrary at an arbitrary direction, the micro-scale representative volume element (RVE) is established by simulating perfectly elastic collision. Combined with the proposed periodic boundary conditions which are suitable for multi-axial loading, the effective elastic properties of composite materials can be predicted. The predicted properties show reasonable agreement with experimental results. By comparing the stress field of RVE with fibers distributed randomly and RVE with fibers distributed periodically, the predicted elastic modulus of RVE with fibers distributed randomly is greater than RVE with fibers distributed periodically.

      PubDate: 2018-04-12T08:29:20Z
      DOI: 10.1016/j.actaastro.2018.03.056
      Issue No: Vol. 147 (2018)
  • Energy-driven scheduling algorithm for nanosatellite energy harvesting
    • Authors: L.K. Slongo; S.V. Martínez; B.V.B. Eiterer; T.G. Pereira; E.A. Bezerra; K.V. Paiva
      Pages: 141 - 151
      Abstract: Publication date: June 2018
      Source:Acta Astronautica, Volume 147
      Author(s): L.K. Slongo, S.V. Martínez, B.V.B. Eiterer, T.G. Pereira, E.A. Bezerra, K.V. Paiva
      The number of tasks that a satellite may execute in orbit is strongly related to the amount of energy its Electrical Power System (EPS) is able to harvest and to store. The manner the stored energy is distributed within the satellite has also a great impact on the CubeSat's overall efficiency. Most CubeSat's EPS do not prioritize energy constraints in their formulation. Unlike that, this work proposes an innovative energy-driven scheduling algorithm based on energy harvesting maximization policy. The energy harvesting circuit is mathematically modeled and the solar panel I-V curves are presented for different temperature and irradiance levels. Considering the models and simulations, the scheduling algorithm is designed to keep solar panels working close to their maximum power point by triggering tasks in the appropriate form. Tasks execution affects battery voltage, which is coupled to the solar panels through a protection circuit. A software based Perturb and Observe strategy allows defining the tasks to be triggered. The scheduling algorithm is tested in FloripaSat, which is an 1U CubeSat. A test apparatus is proposed to emulate solar irradiance variation, considering the satellite movement around the Earth. Tests have been conducted to show that the scheduling algorithm improves the CubeSat energy harvesting capability by 4.48% in a three orbit experiment and up to 8.46% in a single orbit cycle in comparison with the CubeSat operating without the scheduling algorithm.

      PubDate: 2018-04-12T08:29:20Z
      DOI: 10.1016/j.actaastro.2018.03.052
      Issue No: Vol. 147 (2018)
  • Periodic orbit-attitude solutions along planar orbits in a perturbed
           circular restricted three-body problem for the Earth-Moon system
    • Authors: Lorenzo Bucci; Michèle Lavagna; Davide Guzzetti; Kathleen C. Howell
      Pages: 152 - 162
      Abstract: Publication date: June 2018
      Source:Acta Astronautica, Volume 147
      Author(s): Lorenzo Bucci, Michèle Lavagna, Davide Guzzetti, Kathleen C. Howell
      Interest on Large Space Structures (LSS), orbiting in strategic and possibly long-term stable locations, is nowadays increasing in the space community. LSS can serve as strategic outpost to support a variety of manned and unmanned mission, or may carry scientific payloads for astronomical observations. The paper focuses on analysing LSS in the Earth-Moon system, exploring dynamical structures that are available within a multi-body gravitational environment. Coupling between attitude and orbital dynamics is investigated, with particular interest on the gravity gradient torque exerted by the two massive attractors. First, natural periodic orbit-attitude solutions are obtained; a LSS that exploits such solutions would benefit of a naturally periodic body rotation synchronous with the orbital motion, easing the effort of the attitude control system to satisfy pointing requirements. Then, the solar radiation pressure is introduced into the fully coupled dynamical model and its effects investigated, discovering novel periodic attitude solutions. Benefits of periodic behaviours that incorporate solar radiation pressure are discussed, and analysed via the variation of some parameters (e.g reflection/absorption coefficients, position of the centre of pressure). As a final step to refine the current perturbed orbit-attitude model, a structure flexibility is also superimposed to a reference orbit-attitude rigid body motion via a simple, yet effective model. The coupling of structural vibrations and attitude motion is preliminarily explored, and allows identification of possible challenges, that may be faced to position a LSS in a periodic orbit within the Earth-Moon system.

      PubDate: 2018-04-12T08:29:20Z
      DOI: 10.1016/j.actaastro.2018.03.042
      Issue No: Vol. 147 (2018)
  • Effects of atomic oxygen on titanium dioxide thin film
    • Authors: Naoki Shimosako; Yukihiro Hara; Kazunori Shimazaki; Eiji Miyazaki; Hiroshi Sakama
      Pages: 1 - 6
      Abstract: Publication date: May 2018
      Source:Acta Astronautica, Volume 146
      Author(s): Naoki Shimosako, Yukihiro Hara, Kazunori Shimazaki, Eiji Miyazaki, Hiroshi Sakama
      In low earth orbit (LEO), atomic oxygen (AO) has shown to cause degradation of organic materials used in spacecrafts. Similar to other metal oxides such as SiO2, Al2O3 and ITO, TiO2 has potential to protect organic materials. In this study, the anatese-type TiO2 thin films were fabricated by a sol-gel method and irradiated with AO. The properties of TiO2 were compared using mass change, scanning electron microscope (SEM), atomic force microscope (AFM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), transmittance spectra and photocatalytic activity before and after AO irradiation. The results indicate that TiO2 film was hardly eroded and resistant against AO degradation. AO was shown to affects only the surface of a TiO2 film and not the bulk. Upon AO irradiation, the TiO2 films were slightly oxidized. However, these changes were very small. Photocatalytic activity of TiO2 was still maintained in spite of slight decrease upon AO irradiation, which demonstrated that TiO2 thin films are promising for elimination of contaminations outgassed from a spacecraft's materials.

      PubDate: 2018-04-12T08:29:20Z
      DOI: 10.1016/j.actaastro.2018.02.024
      Issue No: Vol. 146 (2018)
  • Investigation of titanium dioxide/ tungstic acid -based photocatalyst for
           human excrement wastewater treatment
    • Authors: Fei Xu; Can Wang; Kemeng Xiao; Yufeng Gao; Tong Zhou; Heng Xu
      Pages: 7 - 14
      Abstract: Publication date: May 2018
      Source:Acta Astronautica, Volume 146
      Author(s): Fei Xu, Can Wang, Kemeng Xiao, Yufeng Gao, Tong Zhou, Heng Xu
      An activated carbon (AC) coated with tungstic acid (WO3)/titanium dioxide (TiO2) nanocomposites photocatalytic material (ACWT) combined with Three-phase Fluidized Bed (TFB) was investigated for human excrement wastewater treatment. Under the ultraviolet (UV) and fluorescent lamp illumination, the ACWT had shown a good performance on chemical oxygen demand (COD) and total nitrogen (TN) removal but inefficient on ammonia nitrogen (NH3-N) removal. Optimized by Taguchi method, COD and TN removal efficiency was up to 88.39% and 55.07%, respectively. Among all the parameters, the dosage of ACWT had the largest contribution on the process. Bacterial community changes after treatment demonstrated that this photocatalytic system had a great sterilization effect on wastewater. These results confirmed that ACWT could be applied for the human excrement wastewater treatment.

      PubDate: 2018-04-12T08:29:20Z
      DOI: 10.1016/j.actaastro.2018.02.025
      Issue No: Vol. 146 (2018)
  • Effect of mass variation on dynamics of tethered system in orbital
    • Authors: Liang Sun; Guowei Zhao; Hai Huang
      Pages: 15 - 23
      Abstract: Publication date: May 2018
      Source:Acta Astronautica, Volume 146
      Author(s): Liang Sun, Guowei Zhao, Hai Huang
      In orbital maneuvering, the mass variation due to fuel consumption has an obvious impact on the dynamics of tethered system, which cannot be neglected. The contributions of the work are mainly shown in two aspects: 1) the improvement of the model; 2) the analysis of dynamics characteristics. As the mass is variable, and the derivative of the mass is directly considered in the traditional Lagrange equation, the expression of generalized force is complicated. To solve this problem, the coagulated derivative is adopted in the paper; besides, the attitude dynamics equations derived in this paper take into account the effect of mass variation and the drift of orbital trajectory at the same time. The bifurcation phenomenon, the pendular motion angular frequency, and amplitudes of tether vibration revealed in this paper can provide a reference for the parameters and controller design in practical engineering. In the article, a dumbbell model is adopted to analyze the dynamics of tethered system, in which the mass variation of base satellite is fully considered. Considering the practical application, the case of orbital transfer under a transversal thrust is mainly studied. Besides, compared with the analytical solutions of librational angles, the effects of mass variation on stability and librational characteristic are studied. Finally, in order to make an analysis of the effect on vibrational characteristic, a lumped model is introduced, which reveals a strong coupling of librational and vibrational characteristics.

      PubDate: 2018-04-12T08:29:20Z
      DOI: 10.1016/j.actaastro.2018.02.016
      Issue No: Vol. 146 (2018)
  • The Deflector Selector: A machine learning framework for prioritizing
           hazardous object deflection technology development
    • Authors: E.R. Nesvold; A. Greenberg; N. Erasmus; E. van Heerden; J.L. Galache; E. Dahlstrom; F. Marchis
      Pages: 33 - 45
      Abstract: Publication date: May 2018
      Source:Acta Astronautica, Volume 146
      Author(s): E.R. Nesvold, A. Greenberg, N. Erasmus, E. van Heerden, J.L. Galache, E. Dahlstrom, F. Marchis
      Several technologies have been proposed for deflecting a hazardous Solar System object on a trajectory that would otherwise impact the Earth. The effectiveness of each technology depends on several characteristics of the given object, including its orbit and size. The distribution of these parameters in the likely population of Earth-impacting objects can thus determine which of the technologies are most likely to be useful in preventing a collision with the Earth. None of the proposed deflection technologies has been developed and fully tested in space. Developing every proposed technology is currently prohibitively expensive, so determining now which technologies are most likely to be effective would allow us to prioritize a subset of proposed deflection technologies for funding and development. We present a new model, the Deflector Selector, that takes as its input the characteristics of a hazardous object or population of such objects and predicts which technology would be able to perform a successful deflection. The model consists of a machine-learning algorithm trained on data produced by N-body integrations simulating the deflections. We describe the model and present the results of tests of the effectiveness of nuclear explosives, kinetic impactors, and gravity tractors on three simulated populations of hazardous objects.

      PubDate: 2018-04-12T08:29:20Z
      DOI: 10.1016/j.actaastro.2018.01.049
      Issue No: Vol. 146 (2018)
  • Three-dimensional multi-physics coupled simulation of ignition transient
           in a dual pulse solid rocket motor
    • Authors: Yingkun Li; Xiong Chen; Jinsheng Xu; Changsheng Zhou; Omer Musa
      Pages: 46 - 65
      Abstract: Publication date: May 2018
      Source:Acta Astronautica, Volume 146
      Author(s): Yingkun Li, Xiong Chen, Jinsheng Xu, Changsheng Zhou, Omer Musa
      In this paper, numerical investigation of ignition transient in a dual pulse solid rocket motor has been conducted. An in-house code has been developed in order to solve multi-physics governing equations, including unsteady compressible flow, heat conduction and structural dynamic. The simplified numerical models for solid propellant ignition and combustion have been added. The conventional serial staggered algorithm is adopted to simulate the fluid structure interaction problems in a loosely-coupled manner. The accuracy of the coupling procedure is validated by the behavior of a cantilever panel subjected to a shock wave. Then, the detailed flow field development, flame propagation characteristics, pressure evolution in the combustion chamber, and the structural response of metal diaphragm are analyzed carefully. The burst-time and burst-pressure of the metal diaphragm are also obtained. The individual effects of the igniter's mass flow rate, metal diaphragm thickness and diameter on the ignition transient have been systemically compared. The numerical results show that the evolution of the flow field in the combustion chamber, the temperature distribution on the propellant surface and the pressure loading on the metal diaphragm surface present a strong three-dimensional behavior during the initial ignition stage. The rupture of metal diaphragm is not only related to the magnitude of pressure loading on the diaphragm surface, but also to the history of pressure loading. The metal diaphragm thickness and diameter have a significant effect on the burst-time and burst-pressure of metal diaphragm.

      PubDate: 2018-04-12T08:29:20Z
      DOI: 10.1016/j.actaastro.2018.01.058
      Issue No: Vol. 146 (2018)
  • B-dot algorithm steady-state motion performance
    • Authors: M. Yu. Ovchinnikov; D.S. Roldugin; S.S. Tkachev; V.I. Penkov
      Pages: 66 - 72
      Abstract: Publication date: May 2018
      Source:Acta Astronautica, Volume 146
      Author(s): M. Yu. Ovchinnikov, D.S. Roldugin, S.S. Tkachev, V.I. Penkov
      Satellite attitude motion subject to the well-known B-dot magnetic control is considered. Unlike the majority of studies the present work focuses on the slowly rotating spacecraft. The attitude and the angular velocity acquired after detumbling the satellite is determined. This task is performed using two relatively simple geomagnetic field models. First the satellite is considered moving in the simplified dipole model. Asymptotically stable rotation around the axis of the maximum moment of inertia is found. This axis direction in the inertial space and the rotation rate are found. This result is then refined using the direct dipole geomagnetic field. Simple stable rotation transforms into the periodical motion, the rotation rate is also refined. Numerical analysis with the gravitational torque and the inclined dipole model verifies the analytical results.

      PubDate: 2018-04-12T08:29:20Z
      DOI: 10.1016/j.actaastro.2018.02.019
      Issue No: Vol. 146 (2018)
  • A Delta-V map of the known Main Belt Asteroids
    • Authors: Anthony Taylor; Jonathan C. McDowell; Martin Elvis
      Pages: 73 - 82
      Abstract: Publication date: May 2018
      Source:Acta Astronautica, Volume 146
      Author(s): Anthony Taylor, Jonathan C. McDowell, Martin Elvis
      With the lowered costs of rocket technology and the commercialization of the space industry, asteroid mining is becoming both feasible and potentially profitable. Although the first targets for mining will be the most accessible near Earth objects (NEOs), the Main Belt contains 10 6 times more material by mass. The large scale expansion of this new asteroid mining industry is contingent on being able to rendezvous with Main Belt asteroids (MBAs), and so on the velocity change required of mining spacecraft (delta-v). This paper develops two different flight burn schemes, both starting from Low Earth Orbit (LEO) and ending with a successful MBA rendezvous. These methods are then applied to the ∼ 700,000 asteroids in the Minor Planet Center (MPC) database with well-determined orbits to find low delta-v mining targets among the MBAs. There are 3986 potential MBA targets with a delta-v < 8 km s − 1 , but the distribution is steep and reduces to just 4 with delta-v < 7 km s-1. The two burn methods are compared and the orbital parameters of low delta-v MBAs are explored.

      PubDate: 2018-04-12T08:29:20Z
      DOI: 10.1016/j.actaastro.2018.02.014
      Issue No: Vol. 146 (2018)
  • The cosmic gorilla effect or the problem of undetected non terrestrial
           intelligent signals
    • Authors: Gabriel G. De la Torre; Manuel A. Garcia
      Pages: 83 - 91
      Abstract: Publication date: May 2018
      Source:Acta Astronautica, Volume 146
      Author(s): Gabriel G. De la Torre, Manuel A. Garcia
      This article points to a long lasting problem in space research and cosmology, the problem of undetected signs of non terrestrial life and civilizations. We intentionally avoid the term extraterrestrial as we consider other possibilities that may arise but not fall strictly within the extraterrestrial scope. We discuss the role of new physics including dark matter and string theory in the search for life and other non terrestrial intelligence. A new classification for non terrestrial civilizations with three types and five dimensions is also provided. We also explain how our own neurophysiology, psychology and consciousness can play a major role in this search of non terrestrial civilizations task and how they have been neglected up to this date. To test this, 137 adults were evaluated using the cognitive reflection test, an attention/awareness questionnaire and a visuospatial searching task with aerial view images to determine the presence of inattentional blindness.

      PubDate: 2018-04-12T08:29:20Z
      DOI: 10.1016/j.actaastro.2018.02.036
      Issue No: Vol. 146 (2018)
  • Transfers from Earth to LEO and LEO to interplanetary space using lasers
    • Authors: Claude R. Phipps; Christophe Bonnal; Fréderic Masson; Michel Boustie; Laurent Berthe; Matthieu Schneider; Sophie Baton; Erik Brambrink; Jean-Marc Chevalier; Laurent Videau; Séverine A.E. Boyer
      Pages: 92 - 102
      Abstract: Publication date: May 2018
      Source:Acta Astronautica, Volume 146
      Author(s): Claude R. Phipps, Christophe Bonnal, Fréderic Masson, Michel Boustie, Laurent Berthe, Matthieu Schneider, Sophie Baton, Erik Brambrink, Jean-Marc Chevalier, Laurent Videau, Séverine A.E. Boyer
      New data on some materials at 80ps pulse duration and 1057 nm wavelength give us the option of proportionally combining them to obtain arbitrary values between 35 (aluminum) and 800 N/MW (POM, polyoxymethylene) for momentum coupling coefficient C m. Laser ablation physics lets us transfer to LEO from Earth, or to interplanetary space using repetitively pulsed lasers and C m values appropriate for each mission. We discuss practical results for lifting small payloads from Earth to LEO, and space missions such as a cis-Mars orbit with associated laser system parameters.

      PubDate: 2018-04-12T08:29:20Z
      DOI: 10.1016/j.actaastro.2018.02.018
      Issue No: Vol. 146 (2018)
  • Performance of high mach number scramjets - Tunnel vs flight
    • Authors: Will O. Landsberg; Vincent Wheatley; Michael K. Smart; Ananthanarayanan Veeraragavan
      Pages: 103 - 110
      Abstract: Publication date: May 2018
      Source:Acta Astronautica, Volume 146
      Author(s): Will O. Landsberg, Vincent Wheatley, Michael K. Smart, Ananthanarayanan Veeraragavan
      While typically analysed through ground-based impulse facilities, scramjets experience significant heating loads in flight, raising engine wall temperatures and the fuel used to cool them beyond standard laboratory conditions. Hence, the present work numerically compares an access-to-space scramjet's performance at both these conditions. The Mach 12 Rectangular-to-Elliptical Shape-Transitioning scramjet flow path is examined via three-dimensional and chemically reacting Reynolds-averaged Navier-Stokes solutions. Flight operation is modelled through 800 K and 1800 K inlet and combustor walls respectively, while fuel is injected at both inlet- and combustor-based stations at 1000 K stagnation temperature. Room temperature walls and fuel plena model shock tunnel conditions. Mixing and combustion performance indicates that while flight conditions promote rapid mixing, high combustor temperatures inhibit the completion of reaction pathways, with reactant dissociation reducing chemical heat release by 16%. However, the heated walls in flight ensured 28% less energy was absorbed by the walls. While inlet fuel injection promotes robust burning of combustor-injected fuel, premature ignition upon the inlet in flight suggests these injectors should be moved further downstream. Coupled with counteracting differences in heat release and loss to the walls, the optimal engine design for flight may differ considerably from that which gives the best performance in the tunnel.

      PubDate: 2018-04-12T08:29:20Z
      DOI: 10.1016/j.actaastro.2018.02.031
      Issue No: Vol. 146 (2018)
  • Latent viral reactivation is associated with changes in plasma
           antimicrobial protein concentrations during long-duration spaceflight
    • Authors: G. Spielmann; M.S. Laughlin; H. Kunz; B.E. Crucian; H.D. Quiriarte; S.K. Mehta; D.L. Pierson; R.J. Simpson
      Pages: 111 - 116
      Abstract: Publication date: May 2018
      Source:Acta Astronautica, Volume 146
      Author(s): G. Spielmann, M.S. Laughlin, H. Kunz, B.E. Crucian, H.D. Quiriarte, S.K. Mehta, D.L. Pierson, R.J. Simpson
      Long duration spaceflights are associated with profound dysregulation of the immune system and latent viral reactivations. However, little is known on the impact of long duration spaceflight on innate immunity which raises concerns on crewmembers' ability to fight infections during a mission. The aim of this study was to determine the effects of spaceflight on plasma antimicrobial proteins (AMPs) and how these changes impact latent herpesvirus reactivations. Plasma, saliva and urine samples were obtained from 23 crewmembers before, during and after a 6-month mission on the International Space Station (ISS). Plasma AMP concentrations were determined by ELISA, and saliva Epstein-Barr virus (EBV) and varicella zoster virus (VZV) and urine cytomegalovirus (CMV) DNA levels were quantified by Real-Time PCR. There was a non-significant increase in plasma HNP1-3 and LL-37 during the early and middle stages of the missions, which was significantly associated with changes in viral DNA during and after spaceflight. Plasma HNP1-3 and Lysozyme increased at the late mission stages in astronauts who had exhibited EBV and VZV reactivations during the early flight stages. Following return to Earth and during recovery, HNP1-3 and lysozyme concentrations were associated with EBV and VZV viral DNA levels, reducing the magnitude of viral reactivation. Reductions in plasma LL-37 upon return were associated with greater CMV reactivation. This study shows that biomarkers of innate immunity appeared to be partially restored after 6-months in space and suggests that following adaptation to the space environment, plasma HNP1-3 and lysozyme facilitate the control of EBV and VZV reactivation rate and magnitude in space and upon return on earth. However, the landing-associated decline in plasma LL-37 may enhance the rate of CMV reactivation in astronauts following spaceflight, potentially compromising crewmember health after landing.

      PubDate: 2018-04-12T08:29:20Z
      DOI: 10.1016/j.actaastro.2018.02.039
      Issue No: Vol. 146 (2018)
  • Application of virtual reality for crew mental health in extended-duration
           space missions
    • Authors: Nick Salamon; Jonathan M. Grimm; John M. Horack; Elizabeth K. Newton
      Pages: 117 - 122
      Abstract: Publication date: May 2018
      Source:Acta Astronautica, Volume 146
      Author(s): Nick Salamon, Jonathan M. Grimm, John M. Horack, Elizabeth K. Newton
      Human exploration of the solar system brings a host of environmental and engineering challenges. Among the most important factors in crew health and human performance is the preservation of mental health. The mental well-being of astronaut crews is a significant issue affecting the success of long-duration space missions, such as habitation on or around the Moon, Mars exploration, and eventual colonization of the solar system. If mental health is not properly addressed, these missions will be at risk. Upkeep of mental health will be especially difficult on long duration missions because many of the support systems available to crews on shorter missions will not be available. In this paper, we examine the use of immersive virtual reality (VR) simulations to maintain healthy mental states in astronaut crews who are removed from the essential comforts typically associated with terrestrial life. Various methods of simulations and their administration are analyzed in the context of current research and knowledge in the fields of psychology, medicine, and space sciences, with a specific focus on the environment faced by astronauts on long-term missions. The results of this investigation show that virtual reality should be considered a plausible measure in preventing mental state deterioration in astronauts, though more work is needed to provide a comprehensive view of the effectiveness and administration of VR methods.

      PubDate: 2018-04-12T08:29:20Z
      DOI: 10.1016/j.actaastro.2018.02.034
      Issue No: Vol. 146 (2018)
  • Numerical investigation of drag and heat flux reduction mechanism of the
           pulsed counterflowing jet on a blunt body in supersonic flows
    • Authors: Rui-rui Zhang; Wei Huang; Li Yan; Lang-quan Li; Shi-bin Li; R. Moradi
      Pages: 123 - 133
      Abstract: Publication date: May 2018
      Source:Acta Astronautica, Volume 146
      Author(s): Rui-rui Zhang, Wei Huang, Li Yan, Lang-quan Li, Shi-bin Li, R. Moradi
      To design a kind of aerospace vehicle, the drag and heat flux reduction are the most important factors. In the current study, the counterflowing jet, one of the effective drag and heat flux reduction concepts, is investigated numerically by the two-dimensional axisymmetric Reynolds-averaged Navier-Stokes equations coupled with the SST k-ω turbulence model. An axisymmetric numerical simulation mode of the counterflowing jet on the supersonic vehicle nose-tip is established, and the numerical method employed is validated by the experimental schlieren images and experimental data in the open literature. A pulsed counterflowing jet scheme is proposed, and it uses a sinusoidal function to control the total and static pressures of the counterflowing jet. The obtained results show that the long penetration mode does not exist in the whole turnaround, even in a relatively small range of the jet total and static pressures, and this is different from the phenomenon obtained under the steady condition in the open literature. At the same time, it is observed that the variation of the physical parameters, such as the Stanton number induced by the pulsed jet, has an obvious periodicity and hysteresis phenomenon.

      PubDate: 2018-04-12T08:29:20Z
      DOI: 10.1016/j.actaastro.2018.02.040
      Issue No: Vol. 146 (2018)
  • Thrust and torque vector characteristics of axially-symmetric E-sail
    • Authors: Marco Bassetto; Giovanni Mengali; Alessandro A. Quarta
      Pages: 134 - 143
      Abstract: Publication date: May 2018
      Source:Acta Astronautica, Volume 146
      Author(s): Marco Bassetto, Giovanni Mengali, Alessandro A. Quarta
      The Electric Solar Wind Sail is an innovative propulsion system concept that gains propulsive acceleration from the interaction with charged particles released by the Sun. The aim of this paper is to obtain analytical expressions for the thrust and torque vectors of a spinning sail of given shape. Under the only assumption that each tether belongs to a plane containing the spacecraft spin axis, a general analytical relation is found for the thrust and torque vectors as a function of the spacecraft attitude relative to an orbital reference frame. The results are then applied to the noteworthy situation of a Sun-facing sail, that is, when the spacecraft spin axis is aligned with the Sun-spacecraft line, which approximatively coincides with the solar wind direction. In that case, the paper discusses the equilibrium shape of the generic conducting tether as a function of the sail geometry and the spin rate, using both a numerical and an analytical (approximate) approach. As a result, the structural characteristics of the conducting tether are related to the spacecraft geometric parameters.

      PubDate: 2018-04-12T08:29:20Z
      DOI: 10.1016/j.actaastro.2018.02.035
      Issue No: Vol. 146 (2018)
  • Shallow transient liquid water environments on present-day mars, and their
           implications for life
    • Authors: Eriita G. Jones
      Pages: 144 - 150
      Abstract: Publication date: May 2018
      Source:Acta Astronautica, Volume 146
      Author(s): Eriita G. Jones
      The identification and characterisation of subsurface liquid water environments on Mars are of high scientific interest. Such environments have the potential to support microbial life, and, more broadly, to develop our understanding of the habitability of planets and moons beyond Earth. Given our current state of knowledge of life on Earth, three pre-requisites are necessary for an environment to be considered ‘habitable’ and therefore capable of supporting terrestrial-like life: energy, biogenic elements, and liquid water with a sufficiently high water activity. The surface of Mars today is predominately cold and dry, and any liquid water exposed to the atmosphere will vaporise or freeze on timescales of hours to days. These conditions have likely persisted for much of the last 10 million years, and perhaps longer. Despite this, briny liquid water flows (Recurrent Slope Linea) have been observed in a number of locations in the present-day. This review examines evidence from the Phoenix Lander (2008) and the Mars Science Laboratory (2012-current), to assess the occurrence of habitable conditions in the shallow Martian regolith. It will be argued that shallow, transient, liquid water brines are potentially habitable by microbial life, are likely a widespread occurrence on Mars, and that future exploration aimed at finding present-day habitable conditions and potential biology should ‘follow the salt’.

      PubDate: 2018-04-12T08:29:20Z
      DOI: 10.1016/j.actaastro.2018.02.027
      Issue No: Vol. 146 (2018)
  • Materials and structures technology insertion into spacecraft systems:
           Successes and challenges
    • Authors: Suraj Rawal
      Pages: 151 - 160
      Abstract: Publication date: May 2018
      Source:Acta Astronautica, Volume 146
      Author(s): Suraj Rawal
      Over the last 30 years, significant advancements have led to the use of multifunctional materials and structures technologies in spacecraft systems. This includes the integration of adaptive structures, advanced composites, nanotechnology, and additive manufacturing technologies. Development of multifunctional structures has been directly influenced by the implementation of processes and tools for adaptive structures pioneered by Prof. Paolo Santini. Multifunctional materials and structures incorporating non-structural engineering functions such as thermal, electrical, radiation shielding, power, and sensors have been investigated. The result has been an integrated structure that offers reduced mass, packaging volume, and ease of integration for spacecraft systems. Current technology development efforts are being conducted to develop innovative multifunctional materials and structures designs incorporating advanced composites, nanotechnology, and additive manufacturing. However, these efforts offer significant challenges in the qualification and acceptance into spacecraft systems. This paper presents a brief overview of the technology development and successful insertion of advanced material technologies into spacecraft structures. Finally, opportunities and challenges to develop and mature next generation advanced materials and structures are presented.

      PubDate: 2018-04-12T08:29:20Z
      DOI: 10.1016/j.actaastro.2018.02.046
      Issue No: Vol. 146 (2018)
  • Surviving global risks through the preservation of humanity's data on the
    • Authors: Alexey Turchin; David Denkenberger
      Pages: 161 - 170
      Abstract: Publication date: May 2018
      Source:Acta Astronautica, Volume 146
      Author(s): Alexey Turchin, David Denkenberger
      Many global catastrophic risks are threatening human civilization, and a number of ideas have been suggested for preventing or surviving them. However, if these interventions fail, society could preserve information about the human race and human DNA samples in the hopes that the next civilization on Earth will be able to reconstruct Homo sapiens and our culture. This requires information preservation of an order of magnitude of 100 million years, a little-explored topic thus far. It is important that a potential future civilization discovers this information as early as possible, thus a beacon should accompany the message in order to increase visibility. The message should ideally contain information about how humanity was destroyed, perhaps including a continuous recording until the end. This could help the potential future civilization to survive. The best place for long-term data storage is under the surface of the Moon, with the beacon constructed as a complex geometric figure drawn by small craters or trenches around a central point. There are several cost-effective options for sending the message as opportunistic payloads on different planned landers.

      PubDate: 2018-04-12T08:29:20Z
      DOI: 10.1016/j.actaastro.2018.02.042
      Issue No: Vol. 146 (2018)
  • Visual navigation using edge curve matching for pinpoint planetary landing
    • Authors: Pingyuan Cui; Xizhen Gao; Shengying Zhu; Wei Shao
      Pages: 171 - 180
      Abstract: Publication date: May 2018
      Source:Acta Astronautica, Volume 146
      Author(s): Pingyuan Cui, Xizhen Gao, Shengying Zhu, Wei Shao
      Pinpoint landing is challenging for future Mars and asteroid exploration missions. Vision-based navigation scheme based on feature detection and matching is practical and can achieve the required precision. However, existing algorithms are computationally prohibitive and utilize poor-performance measurements, which pose great challenges for the application of visual navigation. This paper proposes an innovative visual navigation scheme using crater edge curves during descent and landing phase. In the algorithm, the edge curves of the craters tracked from two sequential images are utilized to determine the relative attitude and position of the lander through a normalized method. Then, considering error accumulation of relative navigation, a method is developed. That is to integrate the crater-based relative navigation method with crater-based absolute navigation method that identifies craters using a georeferenced database for continuous estimation of absolute states. In addition, expressions of the relative state estimate bias are derived. Novel necessary and sufficient observability criteria based on error analysis are provided to improve the navigation performance, which hold true for similar navigation systems. Simulation results demonstrate the effectiveness and high accuracy of the proposed navigation method.

      PubDate: 2018-04-12T08:29:20Z
      DOI: 10.1016/j.actaastro.2018.02.033
      Issue No: Vol. 146 (2018)
  • Collocation of equilibria in gravitational field of triangular body via
           mass redistribution
    • Authors: Alexander A. Burov; Anna D. Guerman; Vasily I. Nikonov
      Pages: 181 - 184
      Abstract: Publication date: May 2018
      Source:Acta Astronautica, Volume 146
      Author(s): Alexander A. Burov, Anna D. Guerman, Vasily I. Nikonov
      We consider a gravitating system with triangular mass distribution that can be used as approximation of gravitational field for small irregular celestial bodies. In such system, the locations of equilibrium points, that is, the points where the gravitational forces are balanced, are analyzed. The goal is to find the mass distribution which provides equilibrium in a pre-assigned location near the triangular system, and to study the stability of this equilibrium.

      PubDate: 2018-04-12T08:29:20Z
      DOI: 10.1016/j.actaastro.2018.02.032
      Issue No: Vol. 146 (2018)
  • The establishment and application of direct coupled
           electrostatic-structural field model in electrostatically controlled
           deployable membrane antenna
    • Authors: Yongzhen Gu; Baoyan Duan; Jingli Du
      Pages: 185 - 191
      Abstract: Publication date: May 2018
      Source:Acta Astronautica, Volume 146
      Author(s): Yongzhen Gu, Baoyan Duan, Jingli Du
      The electrostatically controlled deployable membrane antenna (ECDMA) is a promising space structure due to its low weight, large aperture and high precision characteristics. However, it is an extreme challenge to describe the coupled field between electrostatic and membrane structure accurately. A direct coupled method is applied to solve the coupled problem in this paper. Firstly, the membrane structure and electrostatic field are uniformly described by energy, considering the coupled problem is an energy conservation phenomenon. Then the direct coupled electrostatic-structural field governing equilibrium equations are obtained by energy variation approach. Numerical results show that the direct coupled method improves the computing efficiency by 36% compared with the traditional indirect coupled method with the same level accuracy. Finally, the prototype has been manufactured and tested and the ECDMA finite element simulations show good agreement with the experiment results as the maximum surface error difference is 6%.

      PubDate: 2018-04-12T08:29:20Z
      DOI: 10.1016/j.actaastro.2018.01.041
      Issue No: Vol. 146 (2018)
  • Shape adjustment optimization and experiment of cable-membrane reflectors
    • Authors: Jingli Du; Yongzhen Gu; Hong Bao; Congsi Wang; Xiaofeng Chen
      Pages: 192 - 201
      Abstract: Publication date: May 2018
      Source:Acta Astronautica, Volume 146
      Author(s): Jingli Du, Yongzhen Gu, Hong Bao, Congsi Wang, Xiaofeng Chen
      Cable-membrane structures are widely employed for large space reflectors due to their lightweight, compact and easy package. In these structures, membranes are attached to cable net, serving as reflectors themselves or as supporting structures for other reflective surface. The cable length and membrane shape have to be carefully designed and fabricated to guarantee the desired reflector surface shape. However, due to inevitable error in cable length and membrane shape during the manufacture and assembly of cable-membrane reflectors, some cables have to be designed to be capable of length adjustment. By carefully adjusting the length of these cables, the degeneration in reflector shape precision due to this inevitable error can be effectively reduced. In the paper a shape adjustment algorithm for cable-membrane reflectors is proposed. Meanwhile, model updating is employed during shape adjustment to decrease the discrepancy of the numerical model with respect to the actual reflector. This discrepancy has to be considered because during attaching membranes to cable net, the accuracy of the membrane shape is hard to guarantee. Numerical examples and experimental results demonstrate the proposed method.

      PubDate: 2018-04-12T08:29:20Z
      DOI: 10.1016/j.actaastro.2018.02.037
      Issue No: Vol. 146 (2018)
  • Motivational profiles of retired cosmonauts
    • Authors: Peter Suedfeld; Phyllis J. Johnson; Vadim Gushin; Jelena Brcic
      Pages: 202 - 205
      Abstract: Publication date: May 2018
      Source:Acta Astronautica, Volume 146
      Author(s): Peter Suedfeld, Phyllis J. Johnson, Vadim Gushin, Jelena Brcic
      Motivational patterns have been shown to be related to outcomes such as occupational success and satisfaction, innovation, aggressiveness, cooperation, and conformity. They are likely to be important in adaptation to the demands of flying in a space crew. Autobiographical interviews with 20 retired long-duration male cosmonauts were scored for references to three core motives: the needs for Achievement, Power, and Affiliation. Overall, the cosmonauts mentioned need for Affiliation most often, followed by need for Achievement, with need for Power the least frequently mentioned. However, need for Power increased between reminiscences of one's pre-flight career to those concerning the in-flight and post-flight periods. Imagery related to both other needs decreased. Cosmonauts who had spent less than a year in space mentioned need for Achievement significantly more frequently than those who had spent more than a year. Other space-experience and demographic variables, and changes across pairs of career phases, were not significant. The high scores for need for Affiliation indicate the importance of selecting compatible teams and fostering friendship and cooperation during training and deployment. A relatively flat hierarchical organization would be harmonious with low Power motivation; but the increase during missions indicates a desire for autonomy. After retirement from spaceflight, former space crews should be afforded opportunities for leadership and decision-making to satisfy continuing need for Power. Comparison is made to the same measures applied to a sample of ISS crewmembers, and to the ISS vs. veteran data for 8 cosmonauts who were included in both sets of data.

      PubDate: 2018-04-12T08:29:20Z
      DOI: 10.1016/j.actaastro.2018.02.038
      Issue No: Vol. 146 (2018)
  • A relative navigation sensor for CubeSats based on LED fiducial markers
    • Authors: Francesco Sansone; Francesco Branz; Alessandro Francesconi
      Pages: 206 - 215
      Abstract: Publication date: May 2018
      Source:Acta Astronautica, Volume 146
      Author(s): Francesco Sansone, Francesco Branz, Alessandro Francesconi
      Small satellite platforms are becoming very appealing both for scientific and commercial applications, thanks to their low cost, short development times and availability of standard components and subsystems. The main disadvantage with such vehicles is the limitation of available resources to perform mission tasks. To overcome this drawback, mission concepts are under study that foresee cooperation between autonomous small satellites to accomplish complex tasks; among these, on-orbit servicing and on-orbit assembly of large structures are of particular interest and the global scientific community is putting a significant effort in the miniaturization of critical technologies that are required for such innovative mission scenarios. In this work, the development and the laboratory testing of an accurate relative navigation package for nanosatellites compliant to the CubeSat standard is presented. The system features a small camera and two sets of LED fiducial markers, and is conceived as a standard package that allows small spacecraft to perform mutual tracking during rendezvous and docking maneuvers. The hardware is based on off-the-shelf components assembled in a compact configuration that is compatible with the CubeSat standard. The image processing and pose estimation software was custom developed. The experimental evaluation of the system allowed to determine both the static and dynamic performances. The system is capable to determine the close range relative position and attitude faster than 10 S/s, with errors always below 10 mm and 2 deg.

      PubDate: 2018-04-12T08:29:20Z
      DOI: 10.1016/j.actaastro.2018.02.028
      Issue No: Vol. 146 (2018)
  • Spacecraft-plasma-debris interaction in an ion beam shepherd mission
    • Authors: Filippo Cichocki; Mario Merino; Eduardo Ahedo
      Pages: 216 - 227
      Abstract: Publication date: May 2018
      Source:Acta Astronautica, Volume 146
      Author(s): Filippo Cichocki, Mario Merino, Eduardo Ahedo
      This paper presents a study of the interaction between a spacecraft, a plasma thruster plume and a free floating object, in the context of an active space debris removal mission based on the ion beam shepherd concept. The analysis is performed with the EP2PLUS hybrid code and includes the evaluation of the transferred force and torque to the target debris, its surface sputtering due to the impinging hypersonic ions, and the equivalent electric circuit of the spacecraft-plasma-debris interaction. The electric potential difference that builds up between the spacecraft and the debris, the ion backscattering and the backsputtering contamination of the shepherd satellite are evaluated for a nominal scenario. A sensitivity analysis is carried out to evaluate quantitatively the effects of electron thermodynamics, ambient plasma, heavy species collisions, and debris position.

      PubDate: 2018-04-12T08:29:20Z
      DOI: 10.1016/j.actaastro.2018.02.030
      Issue No: Vol. 146 (2018)
  • Learning-based adaptive prescribed performance control of postcapture
           space robot-target combination without inertia identifications
    • Authors: Caisheng Wei; Jianjun Luo; Honghua Dai; Zilin Bian; Jianping Yuan
      Pages: 228 - 242
      Abstract: Publication date: May 2018
      Source:Acta Astronautica, Volume 146
      Author(s): Caisheng Wei, Jianjun Luo, Honghua Dai, Zilin Bian, Jianping Yuan
      In this paper, a novel learning-based adaptive attitude takeover control method is investigated for the postcapture space robot-target combination with guaranteed prescribed performance in the presence of unknown inertial properties and external disturbance. First, a new static prescribed performance controller is developed to guarantee that all the involved attitude tracking errors are uniformly ultimately bounded by quantitatively characterizing the transient and steady-state performance of the combination. Then, a learning-based supplementary adaptive strategy based on adaptive dynamic programming is introduced to improve the tracking performance of static controller in terms of robustness and adaptiveness only utilizing the input/output data of the combination. Compared with the existing works, the prominent advantage is that the unknown inertial properties are not required to identify in the development of learning-based adaptive control law, which dramatically decreases the complexity and difficulty of the relevant controller design. Moreover, the transient and steady-state performance is guaranteed a priori by designer-specialized performance functions without resorting to repeated regulations of the controller parameters. Finally, the three groups of illustrative examples are employed to verify the effectiveness of the proposed control method.

      PubDate: 2018-04-12T08:29:20Z
      DOI: 10.1016/j.actaastro.2018.03.007
      Issue No: Vol. 146 (2018)
  • Near-critical density filling of the SF6 fluid cell for the ALI-R-DECLIC
           experiment in weightlessness
    • Authors: C. Lecoutre; S. Marre; Y. Garrabos; D. Beysens; I. Hahn
      Pages: 243 - 248
      Abstract: Publication date: May 2018
      Source:Acta Astronautica, Volume 146
      Author(s): C. Lecoutre, S. Marre, Y. Garrabos, D. Beysens, I. Hahn
      Analyses of ground-based experiments on near-critical fluids to precisely determine their density can be hampered by several effects, especially the density stratification of the sample, the liquid wetting behavior at the cell walls, and a possible singular curvature of the “rectilinear” diameter of the density coexisting curve. For the latter effect, theoretical efforts have been made to understand the amplitude and shape of the critical hook of the density diameter, which depart from predictions from the so-called ideal lattice-gas model of the uniaxial 3D-Ising universality class. In order to optimize the observation of these subtle effects on the position and shape of the liquid-vapor meniscus in the particular case of SF6, we have designed and filled a cell that is highly symmetrized with respect to any median plane of the total fluid volume. In such a viewed quasi-perfect symmetrical fluid volume, the precise detection of the meniscus position and shape for different orientations of the cell with respect to the Earth's gravity acceleration field becomes a sensitive probe to estimate the cell mean density filling and to test the singular diameter effects. After integration of this cell in the ALI-R insert, we take benefit of the high optical and thermal performances of the DECLIC Engineering Model. Here we present the sensitive imaging method providing the precise ground-based SF6 benchmark data. From these data analysis it is found that the temperature dependence of the meniscus position does not reflect the expected critical hook in the rectilinear density diameter. Therefore the off-density criticality of the cell is accurately estimated, before near future experiments using the same ALI-R insert in the DECLIC facility already on-board the International Space Station.

      PubDate: 2018-04-12T08:29:20Z
      DOI: 10.1016/j.actaastro.2018.03.004
      Issue No: Vol. 146 (2018)
  • Revisiting the configuration of small satellites structures in the
           framework of 3D Additive Manufacturing
    • Authors: P. Gaudenzi; S. Atek; V. Cardini; M. Eugeni; G. Graterol Nisi; L. Lampani; M. Pasquali; L. Pollice
      Pages: 249 - 258
      Abstract: Publication date: May 2018
      Source:Acta Astronautica, Volume 146
      Author(s): P. Gaudenzi, S. Atek, V. Cardini, M. Eugeni, G. Graterol Nisi, L. Lampani, M. Pasquali, L. Pollice
      In this paper the AM-induced evolution of the design process for small satellites is investigated, leading to the identification of optimal design strategies and the definition of a new MAIT concept. A review of the open literature is presented and some introductory concepts are exposed to highlight the effect of the introduction of AM technologies in the development of new satellites systems. In particular, an innovative structural configuration for the CubeSat class of satellites is proposed, with the ultimate goal of minimizing system complexity via parts reduction and the integration of subsystems through an innovative assembly configuration, as an example to be considered for larger satellites.

      PubDate: 2018-04-12T08:29:20Z
      DOI: 10.1016/j.actaastro.2018.01.036
      Issue No: Vol. 146 (2018)
  • Coordinated trajectory planning of dual-arm space robot using constrained
           particle swarm optimization
    • Authors: Mingming Wang; Jianjun Luo; Jianping Yuan; Ulrich Walter
      Pages: 259 - 272
      Abstract: Publication date: May 2018
      Source:Acta Astronautica, Volume 146
      Author(s): Mingming Wang, Jianjun Luo, Jianping Yuan, Ulrich Walter
      Application of the multi-arm space robot will be more effective than single arm especially when the target is tumbling. This paper investigates the application of particle swarm optimization (PSO) strategy to coordinated trajectory planning of the dual-arm space robot in free-floating mode. In order to overcome the dynamics singularities issue, the direct kinematics equations in conjunction with constrained PSO are employed for coordinated trajectory planning of dual-arm space robot. The joint trajectories are parametrized with Bézier curve to simplify the calculation. Constrained PSO scheme with adaptive inertia weight is implemented to find the optimal solution of joint trajectories while specific objectives and imposed constraints are satisfied. The proposed method is not sensitive to the singularity issue due to the application of forward kinematic equations. Simulation results are presented for coordinated trajectory planning of two kinematically redundant manipulators mounted on a free-floating spacecraft and demonstrate the effectiveness of the proposed method.

      PubDate: 2018-04-12T08:29:20Z
      DOI: 10.1016/j.actaastro.2018.03.012
      Issue No: Vol. 146 (2018)
  • Numerical investigation of over expanded flow behavior in a single
           expansion ramp nozzle
    • Authors: Seyed Mahmood Mousavi; Reza Pourabidi; Ebrahim Goshtasbi-Rad
      Pages: 273 - 281
      Abstract: Publication date: May 2018
      Source:Acta Astronautica, Volume 146
      Author(s): Seyed Mahmood Mousavi, Reza Pourabidi, Ebrahim Goshtasbi-Rad
      The single expansion ramp nozzle is severely over-expanded when the vehicle is at low speed, which hinders its ability to provide optimal configurations for combined cycle engines. The over-expansion leads to flow separation as a result of shock wave/boundary-layer interaction. Flow separation, and the presence of shocks themselves, result in a performance loss in the single expansion ramp nozzle, leading to reduced thrust and increased pressure losses. In the present work, the unsteady two dimensional compressible flow in an over expanded single expansion ramp nozzle has been investigated using finite volume code. To achieve this purpose, the Reynolds stress turbulence model and full multigrid initialization, in addition to the Smirnov's method for examining the errors accumulation, have been employed and the results are compared with available experimental data. The results show that the numerical code is capable of predicting the experimental data with high accuracy. Afterward, the effect of discontinuity jump in wall temperature as well as the length of straight ramp on flow behavior have been studied. It is concluded that variations in wall temperature and length of straight ramp change the shock wave boundary layer interaction, shock structure, shock strength as well as the distance between Lambda shocks.

      PubDate: 2018-04-12T08:29:20Z
      DOI: 10.1016/j.actaastro.2018.03.003
      Issue No: Vol. 146 (2018)
  • Is elevated CO2 in space really harmful to growth and development' A
           case study of Chufa (Cyperus esculentus L.) in Lunar Palace-1
    • Authors: Guanghui Liu; Chen Dong; Yuming Fu; Minjuan Wang; Lingzhi Shao; Juan Yu; Hong Liu
      Pages: 282 - 288
      Abstract: Publication date: May 2018
      Source:Acta Astronautica, Volume 146
      Author(s): Guanghui Liu, Chen Dong, Yuming Fu, Minjuan Wang, Lingzhi Shao, Juan Yu, Hong Liu
      CO2 concentration [CO2] level in artificial ecosystems such as greenhouse agriculture and space farming can easily exceed 1000 μmol mol−1 (or ppm). In order to understand how the growth and development in crop plants may respond to elevated CO2, it is necessary to determine if crop leaves in the closed artificial ecosystem have a fully developed photosynthetic apparatus, and whether or not photosynthesis in these leaves is more responsive to elevated CO2 concentration. To address this issue, we evaluated the response of photosynthetic characteristics, leaf water status and antioxidant capacity of Chufa (Cyperus esculentus L.), which is a sedge-like plant with 1–2 cm small sweet tubers in length, under elevated CO2 concentrations in an artificial closed ecosystem. The results showed that Chufa plants cultivated in the elevated CO2 environment from the seedling stage to the maturity stage were characterized by more appropriate chlorophyll content and photosynthetic rate. The photosynthetic rate of Chufa plants in the 1000 and 3000 ppm treatments was no significant difference with that in 500 ppm CO2 condition both at seedling stage and rapid growth stage. All the treatments had a high relative water content (RWC) about 60% at the maturity stage. However, there was no significant difference in membrane stability index (MSI) at the rapid growth stage. The antioxidase enzymes activities experienced a rise and a drop and reached the peak at the rapid growth stage. Elevated CO2, especially more than 1000 ppm conditions, may accelerant Chufa plants aging process.

      PubDate: 2018-04-12T08:29:20Z
      DOI: 10.1016/j.actaastro.2018.03.002
      Issue No: Vol. 146 (2018)
  • Trajectory optimization for lunar rover performing vertical takeoff
           vertical landing maneuvers in the presence of terrain
    • Authors: Lin Ma; Kexin Wang; Zuhua Xu; Zhijiang Shao; Zhengyu Song; Lorenz T. Biegler
      Pages: 289 - 299
      Abstract: Publication date: May 2018
      Source:Acta Astronautica, Volume 146
      Author(s): Lin Ma, Kexin Wang, Zuhua Xu, Zhijiang Shao, Zhengyu Song, Lorenz T. Biegler
      This study presents a trajectory optimization framework for lunar rover performing vertical takeoff vertical landing (VTVL) maneuvers in the presence of terrain using variable-thrust propulsion. First, a VTVL trajectory optimization problem with three-dimensional kinematics and dynamics model, boundary conditions, and path constraints is formulated. Then, a finite-element approach transcribes the formulated trajectory optimization problem into a nonlinear programming (NLP) problem solved by a highly efficient NLP solver. A homotopy-based backtracking strategy is applied to enhance the convergence in solving the formulated VTVL trajectory optimization problem. The optimal thrust solution typically has a “bang-bang” profile considering that bounds are imposed on the magnitude of engine thrust. An adaptive mesh refinement strategy based on a constant Hamiltonian profile is designed to address the difficulty in locating the breakpoints in the thrust profile. Four scenarios are simulated. Simulation results indicate that the proposed trajectory optimization framework has sufficient adaptability to handle VTVL missions efficiently.

      PubDate: 2018-04-12T08:29:20Z
      DOI: 10.1016/j.actaastro.2018.03.013
      Issue No: Vol. 146 (2018)
  • Testing the efficiency of rover science protocols for robotic sample
           selection: A GeoHeuristic Operational Strategies Test
    • Authors: R.A. Yingst; J.K. Bartley; T.C. Chidsey; B.A. Cohen; G.J. Gilleaudeau; B.M. Hynek; L.C. Kah; M.E. Minitti; R.M.E. Williams; S. Black; J. Gemperline; R. Schaufler; R.J. Thomas
      Pages: 300 - 315
      Abstract: Publication date: May 2018
      Source:Acta Astronautica, Volume 146
      Author(s): R.A. Yingst, J.K. Bartley, T.C. Chidsey, B.A. Cohen, G.J. Gilleaudeau, B.M. Hynek, L.C. Kah, M.E. Minitti, R.M.E. Williams, S. Black, J. Gemperline, R. Schaufler, R.J. Thomas
      The GHOST field tests are designed to isolate and test science-driven rover operations protocols, to determine best practices. During a recent field test at a potential Mars 2020 landing site analog, we tested two Mars Science Laboratory data-acquisition and decision-making methods to assess resulting science return and sample quality: a linear method, where sites of interest are studied in the order encountered, and a “walkabout-first” method, where sites of interest are examined remotely before down-selecting to a subset of sites that are interrogated with more resource-intensive instruments. The walkabout method cost less time and fewer resources, while increasing confidence in interpretations. Contextual data critical to evaluating site geology was acquired earlier than for the linear method, and given a higher priority, which resulted in development of more mature hypotheses earlier in the analysis process. Combined, this saved time and energy in the collection of data with more limited spatial coverage. Based on these results, we suggest that the walkabout method be used where doing so would provide early context and time for the science team to develop hypotheses-critical tests; and that in gathering context, coverage may be more important than higher resolution.

      PubDate: 2018-04-12T08:29:20Z
      DOI: 10.1016/j.actaastro.2018.02.029
      Issue No: Vol. 146 (2018)
  • Attitude control analysis of tethered de-orbiting
    • Authors: T.V. Peters; José Francisco Briz Valero; Diego Escorial Olmos; V. Lappas; P. Jakowski; I. Gray; A. Tsourdos; H. Schaub; R. Biesbroek
      Pages: 316 - 331
      Abstract: Publication date: May 2018
      Source:Acta Astronautica, Volume 146
      Author(s): T.V. Peters, José Francisco Briz Valero, Diego Escorial Olmos, V. Lappas, P. Jakowski, I. Gray, A. Tsourdos, H. Schaub, R. Biesbroek
      The increase of satellites and rocket upper stages in low earth orbit (LEO) has also increased substantially the danger of collisions in space. Studies have shown that the problem will continue to grow unless a number of debris are removed every year. A typical active debris removal (ADR) mission scenario includes launching an active spacecraft (chaser) which will rendezvous with the inactive target (debris), capture the debris and eventually deorbit both satellites. Many concepts for the capture of the debris while keeping a connection via a tether, between the target and chaser have been investigated, including harpoons, nets, grapples and robotic arms. The paper provides an analysis on the attitude control behaviour for a tethered de-orbiting mission based on the ESA e.Deorbit reference mission, where Envisat is the debris target to be captured by a chaser using a net which is connected to the chaser with a tether. The paper provides novel insight on the feasibility of tethered de-orbiting for the various mission phases such as stabilization after capture, de-orbit burn (plus stabilization), stabilization during atmospheric pass, highlighting the importance of various critical mission parameters such as the tether material. It is shown that the selection of the appropriate tether material while using simple controllers can reduce the effort needed for tethered deorbiting and can safely control the attitude of the debris/chaser connected with a tether, without the danger of a collision.

      PubDate: 2018-04-12T08:29:20Z
      DOI: 10.1016/j.actaastro.2018.03.016
      Issue No: Vol. 146 (2018)
  • Fault-tolerant feature-based estimation of space debris rotational motion
           during active removal missions
    • Authors: Gabriele Biondi; Stefano Mauro; Stefano Pastorelli; Massimo Sorli
      Pages: 332 - 338
      Abstract: Publication date: May 2018
      Source:Acta Astronautica, Volume 146
      Author(s): Gabriele Biondi, Stefano Mauro, Stefano Pastorelli, Massimo Sorli
      One of the key functionalities required by an Active Debris Removal mission is the assessment of the target kinematics and inertial properties. Passive sensors, such as stereo cameras, are often included in the onboard instrumentation of a chaser spacecraft for capturing sequential photographs and for tracking features of the target surface. A plenty of methods, based on Kalman filtering, are available for the estimation of the target's state from feature positions; however, to guarantee the filter convergence, they typically require continuity of measurements and the capability of tracking a fixed set of pre-defined features of the object. These requirements clash with the actual tracking conditions: failures in feature detection often occur and the assumption of having some a-priori knowledge about the shape of the target could be restrictive in certain cases. The aim of the presented work is to propose a fault-tolerant alternative method for estimating the angular velocity and the relative magnitudes of the principal moments of inertia of the target. Raw data regarding the positions of the tracked features are processed to evaluate corrupted values of a 3-dimentional parameter which entirely describes the finite screw motion of the debris and which primarily is invariant on the particular set of considered features of the object. Missing values of the parameter are completely restored exploiting the typical periodicity of the rotational motion of an uncontrolled satellite: compressed sensing techniques, typically adopted for recovering images or for prognostic applications, are herein used in a completely original fashion for retrieving a kinematic signal that appears sparse in the frequency domain. Due to its invariance about the features, no assumptions are needed about the target's shape and continuity of the tracking. The obtained signal is useful for the indirect evaluation of an attitude signal that feeds an unscented Kalman filter for the estimation of the global rotational state of the target. The results of the computer simulations showed a good robustness of the method and its potential applicability for general motion conditions of the target.

      PubDate: 2018-04-12T08:29:20Z
      DOI: 10.1016/j.actaastro.2018.01.029
      Issue No: Vol. 146 (2018)
  • Effects of gas liquid ratio on the atomization characteristics of
           gas-liquid swirl coaxial injectors
    • Authors: Zhongtao Kang; Qinglian Li; Jiaqi Zhang; Peng Cheng
      Abstract: Publication date: Available online 22 February 2018
      Source:Acta Astronautica
      Author(s): Zhongtao Kang, Qinglian Li, Jiaqi Zhang, Peng Cheng
      To understand the atomization characteristics and atomization mechanism of the gas-liquid swirl coaxial (GLSC) injector, a back-lighting photography technique has been employed to capture the instantaneous spray images with a high speed camera. The diameter and velocity of the droplets in the spray have been characterized with a Dantec Phase Doppler Anemometry (PDA) system. The effects of gas liquid ratio (GLR) on the spray pattern, Sauter mean diameter (SMD), diameter-velocity distribution and mass flow rate distribution were analyzed and discussed. The results show that the atomization of the GLSC injector is dominated by the film breakup when the GLR is small, and violent gas-liquid interaction when the GLR is large enough. The film breakup dominated spray can be divided into gas acceleration region and film breakup region while the violent gas-liquid interaction dominated spray can be divided into the gas acceleration region, violent gas-liquid interaction region and big droplets breakup region. The atomization characteristics of the GLSC injector is significantly influenced by the GLR. From the point of atomization performance, the increase of GLR has positive effects. It decreases the global Sauter mean diameter (GSMD) and varies the SMD distribution from a hollow cone shape (GLR = 0) to an inverted V shape, and finally slanted N shape. However, from the point of spatial distribution, the increase of GLR has negative effects, because the mass flow rate distribution becomes more nonuniform.

      PubDate: 2018-02-26T09:51:38Z
      DOI: 10.1016/j.actaastro.2018.02.026
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