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Publisher: Elsevier   (Total: 3184 journals)

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Showing 1 - 200 of 3184 Journals sorted alphabetically
Academic Pediatrics     Hybrid Journal   (Followers: 37, SJR: 1.655, CiteScore: 2)
Academic Radiology     Hybrid Journal   (Followers: 26, SJR: 1.015, CiteScore: 2)
Accident Analysis & Prevention     Partially Free   (Followers: 100, SJR: 1.462, CiteScore: 3)
Accounting Forum     Hybrid Journal   (Followers: 28, SJR: 0.932, CiteScore: 2)
Accounting, Organizations and Society     Hybrid Journal   (Followers: 40, SJR: 1.771, CiteScore: 3)
Achievements in the Life Sciences     Open Access   (Followers: 6)
Acta Anaesthesiologica Taiwanica     Open Access   (Followers: 7)
Acta Astronautica     Hybrid Journal   (Followers: 434, SJR: 0.758, CiteScore: 2)
Acta Automatica Sinica     Full-text available via subscription   (Followers: 2)
Acta Biomaterialia     Hybrid Journal   (Followers: 28, SJR: 1.967, CiteScore: 7)
Acta Colombiana de Cuidado Intensivo     Full-text available via subscription   (Followers: 3)
Acta de Investigación Psicológica     Open Access   (Followers: 3)
Acta Ecologica Sinica     Open Access   (Followers: 11, SJR: 0.18, CiteScore: 1)
Acta Histochemica     Hybrid Journal   (Followers: 3, SJR: 0.661, CiteScore: 2)
Acta Materialia     Hybrid Journal   (Followers: 306, SJR: 3.263, CiteScore: 6)
Acta Mathematica Scientia     Full-text available via subscription   (Followers: 5, SJR: 0.504, CiteScore: 1)
Acta Mechanica Solida Sinica     Full-text available via subscription   (Followers: 9, SJR: 0.542, CiteScore: 1)
Acta Oecologica     Hybrid Journal   (Followers: 12, SJR: 0.834, CiteScore: 2)
Acta Otorrinolaringologica (English Edition)     Full-text available via subscription  
Acta Otorrinolaringológica Española     Full-text available via subscription   (Followers: 2, SJR: 0.307, CiteScore: 0)
Acta Pharmaceutica Sinica B     Open Access   (Followers: 1, SJR: 1.793, CiteScore: 6)
Acta Poética     Open Access   (Followers: 4, SJR: 0.101, CiteScore: 0)
Acta Psychologica     Hybrid Journal   (Followers: 25, SJR: 1.331, CiteScore: 2)
Acta Sociológica     Open Access   (Followers: 1)
Acta Tropica     Hybrid Journal   (Followers: 6, SJR: 1.052, CiteScore: 2)
Acta Urológica Portuguesa     Open Access  
Actas Dermo-Sifiliograficas     Full-text available via subscription   (Followers: 3, SJR: 0.374, CiteScore: 1)
Actas Dermo-Sifiliográficas (English Edition)     Full-text available via subscription   (Followers: 2)
Actas Urológicas Españolas     Full-text available via subscription   (Followers: 3, SJR: 0.344, CiteScore: 1)
Actas Urológicas Españolas (English Edition)     Full-text available via subscription   (Followers: 1)
Actualites Pharmaceutiques     Full-text available via subscription   (Followers: 7, SJR: 0.19, CiteScore: 0)
Actualites Pharmaceutiques Hospitalieres     Full-text available via subscription   (Followers: 3)
Acupuncture and Related Therapies     Hybrid Journal   (Followers: 8)
Acute Pain     Full-text available via subscription   (Followers: 15, SJR: 2.671, CiteScore: 5)
Ad Hoc Networks     Hybrid Journal   (Followers: 11, SJR: 0.53, CiteScore: 4)
Addictive Behaviors     Hybrid Journal   (Followers: 18, SJR: 1.29, CiteScore: 3)
Addictive Behaviors Reports     Open Access   (Followers: 9, SJR: 0.755, CiteScore: 2)
Additive Manufacturing     Hybrid Journal   (Followers: 11, SJR: 2.611, CiteScore: 8)
Additives for Polymers     Full-text available via subscription   (Followers: 23)
Advanced Drug Delivery Reviews     Hybrid Journal   (Followers: 183, SJR: 4.09, CiteScore: 13)
Advanced Engineering Informatics     Hybrid Journal   (Followers: 12, SJR: 1.167, CiteScore: 4)
Advanced Powder Technology     Hybrid Journal   (Followers: 17, SJR: 0.694, CiteScore: 3)
Advances in Accounting     Hybrid Journal   (Followers: 9, SJR: 0.277, CiteScore: 1)
Advances in Agronomy     Full-text available via subscription   (Followers: 17, SJR: 2.384, CiteScore: 5)
Advances in Anesthesia     Full-text available via subscription   (Followers: 29, SJR: 0.126, CiteScore: 0)
Advances in Antiviral Drug Design     Full-text available via subscription   (Followers: 2)
Advances in Applied Mathematics     Full-text available via subscription   (Followers: 11, SJR: 0.992, CiteScore: 1)
Advances in Applied Mechanics     Full-text available via subscription   (Followers: 11, SJR: 1.551, CiteScore: 4)
Advances in Applied Microbiology     Full-text available via subscription   (Followers: 24, SJR: 2.089, CiteScore: 5)
Advances In Atomic, Molecular, and Optical Physics     Full-text available via subscription   (Followers: 15, SJR: 0.572, CiteScore: 2)
Advances in Biological Regulation     Hybrid Journal   (Followers: 4, SJR: 2.61, CiteScore: 7)
Advances in Botanical Research     Full-text available via subscription   (Followers: 2, SJR: 0.686, CiteScore: 2)
Advances in Cancer Research     Full-text available via subscription   (Followers: 33, SJR: 3.043, CiteScore: 6)
Advances in Carbohydrate Chemistry and Biochemistry     Full-text available via subscription   (Followers: 9, SJR: 1.453, CiteScore: 2)
Advances in Catalysis     Full-text available via subscription   (Followers: 5, SJR: 1.992, CiteScore: 5)
Advances in Cell Aging and Gerontology     Full-text available via subscription   (Followers: 5)
Advances in Cellular and Molecular Biology of Membranes and Organelles     Full-text available via subscription   (Followers: 14)
Advances in Chemical Engineering     Full-text available via subscription   (Followers: 29, SJR: 0.156, CiteScore: 1)
Advances in Child Development and Behavior     Full-text available via subscription   (Followers: 10, SJR: 0.713, CiteScore: 1)
Advances in Chronic Kidney Disease     Full-text available via subscription   (Followers: 10, SJR: 1.316, CiteScore: 2)
Advances in Clinical Chemistry     Full-text available via subscription   (Followers: 26, SJR: 1.562, CiteScore: 3)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 20, SJR: 1.977, CiteScore: 8)
Advances in Computers     Full-text available via subscription   (Followers: 14, SJR: 0.205, CiteScore: 1)
Advances in Dermatology     Full-text available via subscription   (Followers: 15)
Advances in Developmental Biology     Full-text available via subscription   (Followers: 13)
Advances in Digestive Medicine     Open Access   (Followers: 12)
Advances in DNA Sequence-Specific Agents     Full-text available via subscription   (Followers: 7)
Advances in Drug Research     Full-text available via subscription   (Followers: 26)
Advances in Ecological Research     Full-text available via subscription   (Followers: 43, SJR: 2.524, CiteScore: 4)
Advances in Engineering Software     Hybrid Journal   (Followers: 29, SJR: 1.159, CiteScore: 4)
Advances in Experimental Biology     Full-text available via subscription   (Followers: 8)
Advances in Experimental Social Psychology     Full-text available via subscription   (Followers: 51, SJR: 5.39, CiteScore: 8)
Advances in Exploration Geophysics     Full-text available via subscription   (Followers: 1)
Advances in Fluorine Science     Full-text available via subscription   (Followers: 9)
Advances in Food and Nutrition Research     Full-text available via subscription   (Followers: 65, SJR: 0.591, CiteScore: 2)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 17)
Advances in Genetics     Full-text available via subscription   (Followers: 21, SJR: 1.354, CiteScore: 4)
Advances in Genome Biology     Full-text available via subscription   (Followers: 10, SJR: 12.74, CiteScore: 13)
Advances in Geophysics     Full-text available via subscription   (Followers: 7, SJR: 1.193, CiteScore: 3)
Advances in Heat Transfer     Full-text available via subscription   (Followers: 26, SJR: 0.368, CiteScore: 1)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 11, SJR: 0.749, CiteScore: 3)
Advances in Human Factors/Ergonomics     Full-text available via subscription   (Followers: 24)
Advances in Imaging and Electron Physics     Full-text available via subscription   (Followers: 3, SJR: 0.193, CiteScore: 0)
Advances in Immunology     Full-text available via subscription   (Followers: 36, SJR: 4.433, CiteScore: 6)
Advances in Inorganic Chemistry     Full-text available via subscription   (Followers: 10, SJR: 1.163, CiteScore: 2)
Advances in Insect Physiology     Full-text available via subscription   (Followers: 2, SJR: 1.938, CiteScore: 3)
Advances in Integrative Medicine     Hybrid Journal   (Followers: 6, SJR: 0.176, CiteScore: 0)
Advances in Intl. Accounting     Full-text available via subscription   (Followers: 3)
Advances in Life Course Research     Hybrid Journal   (Followers: 9, SJR: 0.682, CiteScore: 2)
Advances in Lipobiology     Full-text available via subscription   (Followers: 1)
Advances in Magnetic and Optical Resonance     Full-text available via subscription   (Followers: 8)
Advances in Marine Biology     Full-text available via subscription   (Followers: 21, SJR: 0.88, CiteScore: 2)
Advances in Mathematics     Full-text available via subscription   (Followers: 12, SJR: 3.027, CiteScore: 2)
Advances in Medical Sciences     Hybrid Journal   (Followers: 8, SJR: 0.694, CiteScore: 2)
Advances in Medicinal Chemistry     Full-text available via subscription   (Followers: 6)
Advances in Microbial Physiology     Full-text available via subscription   (Followers: 5, SJR: 1.158, CiteScore: 3)
Advances in Molecular and Cell Biology     Full-text available via subscription   (Followers: 24)
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: 0.182, CiteScore: 0)
Advances in Nanoporous Materials     Full-text available via subscription   (Followers: 5)
Advances in Oncobiology     Full-text available via subscription   (Followers: 2)
Advances in Organ Biology     Full-text available via subscription   (Followers: 2)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 18, SJR: 1.875, CiteScore: 4)
Advances in Parallel Computing     Full-text available via subscription   (Followers: 7, SJR: 0.174, CiteScore: 0)
Advances in Parasitology     Full-text available via subscription   (Followers: 5, SJR: 1.579, CiteScore: 4)
Advances in Pediatrics     Full-text available via subscription   (Followers: 27, SJR: 0.461, CiteScore: 1)
Advances in Pharmaceutical Sciences     Full-text available via subscription   (Followers: 18)
Advances in Pharmacology     Full-text available via subscription   (Followers: 17, SJR: 1.536, CiteScore: 3)
Advances in Physical Organic Chemistry     Full-text available via subscription   (Followers: 9, SJR: 0.574, CiteScore: 1)
Advances in Phytomedicine     Full-text available via subscription  
Advances in Planar Lipid Bilayers and Liposomes     Full-text available via subscription   (Followers: 3, SJR: 0.109, CiteScore: 1)
Advances in Plant Biochemistry and Molecular Biology     Full-text available via subscription   (Followers: 10)
Advances in Plant Pathology     Full-text available via subscription   (Followers: 6)
Advances in Porous Media     Full-text available via subscription   (Followers: 5)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 19)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 20, SJR: 0.791, CiteScore: 2)
Advances in Psychology     Full-text available via subscription   (Followers: 66)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 6, SJR: 0.371, CiteScore: 1)
Advances in Radiation Oncology     Open Access   (Followers: 1, SJR: 0.263, CiteScore: 1)
Advances in Small Animal Medicine and Surgery     Hybrid Journal   (Followers: 3, SJR: 0.101, CiteScore: 0)
Advances in Space Biology and Medicine     Full-text available via subscription   (Followers: 6)
Advances in Space Research     Full-text available via subscription   (Followers: 420, SJR: 0.569, CiteScore: 2)
Advances in Structural Biology     Full-text available via subscription   (Followers: 5)
Advances in Surgery     Full-text available via subscription   (Followers: 13, SJR: 0.555, CiteScore: 2)
Advances in the Study of Behavior     Full-text available via subscription   (Followers: 37, SJR: 2.208, CiteScore: 4)
Advances in Veterinary Medicine     Full-text available via subscription   (Followers: 20)
Advances in Veterinary Science and Comparative Medicine     Full-text available via subscription   (Followers: 15)
Advances in Virus Research     Full-text available via subscription   (Followers: 5, SJR: 2.262, CiteScore: 5)
Advances in Water Resources     Hybrid Journal   (Followers: 53, SJR: 1.551, CiteScore: 3)
Aeolian Research     Hybrid Journal   (Followers: 6, SJR: 1.117, CiteScore: 3)
Aerospace Science and Technology     Hybrid Journal   (Followers: 381, SJR: 0.796, CiteScore: 3)
AEU - Intl. J. of Electronics and Communications     Hybrid Journal   (Followers: 8, SJR: 0.42, CiteScore: 2)
African J. of Emergency Medicine     Open Access   (Followers: 6, SJR: 0.296, CiteScore: 0)
Ageing Research Reviews     Hybrid Journal   (Followers: 12, SJR: 3.671, CiteScore: 9)
Aggression and Violent Behavior     Hybrid Journal   (Followers: 473, SJR: 1.238, CiteScore: 3)
Agri Gene     Hybrid Journal   (Followers: 1, SJR: 0.13, CiteScore: 0)
Agricultural and Forest Meteorology     Hybrid Journal   (Followers: 18, SJR: 1.818, CiteScore: 5)
Agricultural Systems     Hybrid Journal   (Followers: 31, SJR: 1.156, CiteScore: 4)
Agricultural Water Management     Hybrid Journal   (Followers: 45, SJR: 1.272, CiteScore: 3)
Agriculture and Agricultural Science Procedia     Open Access   (Followers: 4)
Agriculture and Natural Resources     Open Access   (Followers: 3)
Agriculture, Ecosystems & Environment     Hybrid Journal   (Followers: 58, SJR: 1.747, CiteScore: 4)
Ain Shams Engineering J.     Open Access   (Followers: 5, SJR: 0.589, CiteScore: 3)
Air Medical J.     Hybrid Journal   (Followers: 7, SJR: 0.26, CiteScore: 0)
AKCE Intl. J. of Graphs and Combinatorics     Open Access   (SJR: 0.19, CiteScore: 0)
Alcohol     Hybrid Journal   (Followers: 12, SJR: 1.153, CiteScore: 3)
Alcoholism and Drug Addiction     Open Access   (Followers: 11)
Alergologia Polska : Polish J. of Allergology     Full-text available via subscription   (Followers: 1)
Alexandria Engineering J.     Open Access   (Followers: 2, SJR: 0.604, CiteScore: 3)
Alexandria J. of Medicine     Open Access   (Followers: 1, SJR: 0.191, CiteScore: 1)
Algal Research     Partially Free   (Followers: 11, SJR: 1.142, CiteScore: 4)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 2)
Allergologia et Immunopathologia     Full-text available via subscription   (Followers: 1, SJR: 0.504, CiteScore: 1)
Allergology Intl.     Open Access   (Followers: 5, SJR: 1.148, CiteScore: 2)
Alpha Omegan     Full-text available via subscription   (SJR: 3.521, CiteScore: 6)
ALTER - European J. of Disability Research / Revue Européenne de Recherche sur le Handicap     Full-text available via subscription   (Followers: 10, SJR: 0.201, CiteScore: 1)
Alzheimer's & Dementia     Hybrid Journal   (Followers: 54, SJR: 4.66, CiteScore: 10)
Alzheimer's & Dementia: Diagnosis, Assessment & Disease Monitoring     Open Access   (Followers: 6, SJR: 1.796, CiteScore: 4)
Alzheimer's & Dementia: Translational Research & Clinical Interventions     Open Access   (Followers: 6, SJR: 1.108, CiteScore: 3)
Ambulatory Pediatrics     Hybrid Journal   (Followers: 5)
American Heart J.     Hybrid Journal   (Followers: 58, SJR: 3.267, CiteScore: 4)
American J. of Cardiology     Hybrid Journal   (Followers: 63, SJR: 1.93, CiteScore: 3)
American J. of Emergency Medicine     Hybrid Journal   (Followers: 46, SJR: 0.604, CiteScore: 1)
American J. of Geriatric Pharmacotherapy     Full-text available via subscription   (Followers: 12)
American J. of Geriatric Psychiatry     Hybrid Journal   (Followers: 14, SJR: 1.524, CiteScore: 3)
American J. of Human Genetics     Hybrid Journal   (Followers: 37, SJR: 7.45, CiteScore: 8)
American J. of Infection Control     Hybrid Journal   (Followers: 29, SJR: 1.062, CiteScore: 2)
American J. of Kidney Diseases     Hybrid Journal   (Followers: 36, SJR: 2.973, CiteScore: 4)
American J. of Medicine     Hybrid Journal   (Followers: 50)
American J. of Medicine Supplements     Full-text available via subscription   (Followers: 3, SJR: 1.967, CiteScore: 2)
American J. of Obstetrics and Gynecology     Hybrid Journal   (Followers: 248, SJR: 2.7, CiteScore: 4)
American J. of Ophthalmology     Hybrid Journal   (Followers: 66, SJR: 3.184, CiteScore: 4)
American J. of Ophthalmology Case Reports     Open Access   (Followers: 5, SJR: 0.265, CiteScore: 0)
American J. of Orthodontics and Dentofacial Orthopedics     Full-text available via subscription   (Followers: 6, SJR: 1.289, CiteScore: 1)
American J. of Otolaryngology     Hybrid Journal   (Followers: 25, SJR: 0.59, CiteScore: 1)
American J. of Pathology     Hybrid Journal   (Followers: 32, SJR: 2.139, CiteScore: 4)
American J. of Preventive Medicine     Hybrid Journal   (Followers: 28, SJR: 2.164, CiteScore: 4)
American J. of Surgery     Hybrid Journal   (Followers: 39, SJR: 1.141, CiteScore: 2)
American J. of the Medical Sciences     Hybrid Journal   (Followers: 12, SJR: 0.767, CiteScore: 1)
Ampersand : An Intl. J. of General and Applied Linguistics     Open Access   (Followers: 7)
Anaerobe     Hybrid Journal   (Followers: 4, SJR: 1.144, CiteScore: 3)
Anaesthesia & Intensive Care Medicine     Full-text available via subscription   (Followers: 66, SJR: 0.138, CiteScore: 0)
Anaesthesia Critical Care & Pain Medicine     Full-text available via subscription   (Followers: 24, SJR: 0.411, CiteScore: 1)
Anales de Cirugia Vascular     Full-text available via subscription   (Followers: 1)
Anales de Pediatría     Full-text available via subscription   (Followers: 3, SJR: 0.277, CiteScore: 0)
Anales de Pediatría (English Edition)     Full-text available via subscription  
Anales de Pediatría Continuada     Full-text available via subscription  
Analytic Methods in Accident Research     Hybrid Journal   (Followers: 5, SJR: 4.849, CiteScore: 10)
Analytica Chimica Acta     Hybrid Journal   (Followers: 44, SJR: 1.512, CiteScore: 5)
Analytica Chimica Acta : X     Open Access  
Analytical Biochemistry     Hybrid Journal   (Followers: 207, SJR: 0.633, CiteScore: 2)
Analytical Chemistry Research     Open Access   (Followers: 13, SJR: 0.411, CiteScore: 2)
Analytical Spectroscopy Library     Full-text available via subscription   (Followers: 14)
Anesthésie & Réanimation     Full-text available via subscription   (Followers: 2)
Anesthesiology Clinics     Full-text available via subscription   (Followers: 25, SJR: 0.683, CiteScore: 2)
Angiología     Full-text available via subscription   (SJR: 0.121, CiteScore: 0)
Angiologia e Cirurgia Vascular     Open Access   (Followers: 1, SJR: 0.111, CiteScore: 0)
Animal Behaviour     Hybrid Journal   (Followers: 217, SJR: 1.58, CiteScore: 3)
Animal Feed Science and Technology     Hybrid Journal   (Followers: 6, SJR: 0.937, CiteScore: 2)
Animal Reproduction Science     Hybrid Journal   (Followers: 7, SJR: 0.704, CiteScore: 2)

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Similar Journals
Journal Cover
Acta Astronautica
Journal Prestige (SJR): 0.758
Citation Impact (citeScore): 2
Number of Followers: 434  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0094-5765
Published by Elsevier Homepage  [3184 journals]
  • Effects of deorbit evolution on space-based pulse laser irradiating
           centimeter-scale space debris in LEO
    • Abstract: Publication date: Available online 14 September 2019Source: Acta AstronauticaAuthor(s): Yingwu Fang, Jun Pan, Yijia Luo, Chunwang Li The aim of this work is to address the dynamic response rules of deorbit evolution for removing centimeter-scale dangerous space debris near the international space station (ISS) by space-based single laser station. According to the theory of orbital dynamics and laser irradiation technology, the deorbit model of space-based laser irradiating the centimeter-scale debris in low earth orbit (LEO) was established. The deorbit process of driving the centimeter-scale debris was simulated by analyzing the orbit and laser parameters in coplanar/non-coplanar conditions, and the distribution rules of irradiation distance with action time were also obtained. Furthermore, the dynamic characteristics of deorbit evolution were investigated by calculating the flight paths and orbital elements after the dangerous debris is irradiated, and the interaction mechanism between space-based nanosecond pulse laser and the dangerous debris was detailedly discussed by estimating collision risk between the dangerous debris and the ISS. The simulation results indicated that the collision risk between the dangerous debris and the ISS was successfully eliminated based on the designed removal scheme and given clearance windows. Therefore, it is highly important for exploring excellent clear method to master removal rules of centimeter-scale dangerous space debris in LEO by the space-based nanosecond pulse laser.
       
  • Configuration design and collision avoidance control of an electromagnetic
           vibration isolation system on satellites considering environmental
           disturbances
    • Abstract: Publication date: Available online 14 September 2019Source: Acta AstronauticaAuthor(s): Chao Sheng, Yao Zhang, Quan Hu, Jingrui Zhang This paper presents an electromagnetic vibration isolation system (EVIS) that connects the support module (SM) and the payload module (PM) by electromagnetic interaction, where there is no mechanical connection between the two parts to keep the PM free from disturbances while working on orbit. The configuration and the control method of the EVIS are designed to realize vibration isolation, collision avoidance and accurate control for the PM. First, the configuration of the EVIS is presented and the relative motion equations between the SM and the PM including translation and rotation equations are built, considering disturbances from the SM and space environment. Based on the dynamic equations and the collision constraint between the SM and the PM, the control method which realizes collision avoidance and accurate control for relative motion of the two parts is presented. Finally, the accuracy and efficiency of this study are validated through numerical simulations.
       
  • Prospects for applying BaSO4 powders as pigments for spacecraft
           thermal control coatings
    • Abstract: Publication date: Available online 12 September 2019Source: Acta AstronauticaAuthor(s): M.M. Mikhailov, S.A. Yuryev, A.N. Lapin The authors carried out a comparative analysis on the diffuse reflectance spectra within 250 - 2500 nm and on the solar absorptance of BaSO4, ZnO, and TiO2 reflective powders. The authors also considered the powders’ change after irradiation with electron fluence of (1 and 3)∙1016cm-2 with 30 keV and recorded the spectra in a vacuum on the spot (in situ). It has been established that BaSO4 powder exceeds ZnO and TiO2 both in its initial optical properties and in its radiation stability. BaSO4 powder can efficiently function as a pigment for spacecraft thermal control coatings. Additionally, the authors performed the solid-state modification of BaSO4 powder with SiO2 and ZrO2 nanoparticles. An increase in the radiation resistance of the modified BaSO4 powder is shown to be 1.65-1.93 times in comparison with the non-modified one.
       
  • Pseudostate theory based iterative preliminary design method for powered
           gravity-assist interplanetary trajectories
    • Abstract: Publication date: Available online 9 September 2019Source: Acta AstronauticaAuthor(s): Bin Yang, Hongwei Yang, Shuang Li The patched conic method is usually used for preliminarily design of gravity-assist transfer trajectories. However, gravity assist is usually simplified as an instantaneous velocity impulse and the time of flight for gravity assist is ignored, which differs from actual scenarios. In this paper, gravity assist is considered as a continuous process and a novel method employing the pseudostate theory is proposed to design gravity-assist transfer trajectories. The mission trajectory is categorized as gravity-assist segments and interplanetary transfer segments. A powered gravity-assist model based on the pseudostate theory is used to solve the gravity-assist segments with the restricted three-body dynamics. Then, these gravity-assist segments thus solved are patched with the interplanetary transfer segments using an adaptive iterative patching technique, which adopts an adaptive parameter adjustment strategy to improve the efficiency and robustness. Thereafter, a consecutive interplanetary mission trajectory is finally obtained. In addition, a new estimation formula of the sweepback duration is derived according to the radius of gravity field and the excess velocity. The simulation results verify the effectiveness and accuracy of the proposed formula. The transfer trajectories to Jupiter with Venus, Earth and Mars gravity assists are respectively obtained by the proposed method. Compared with patched conic methods, the fuel optimal and more realistic trajectories are efficiently solved utilizing the proposed method for gravity-assist interplanetary mission.
       
  • Luni-solar resonances and effect on long-term evolution of inclined
           geostationary transfer orbits
    • Abstract: Publication date: Available online 9 September 2019Source: Acta AstronauticaAuthor(s): Xuhui Luo, Yue Wang In this paper, a singly-averaged, semi-analytical orbital dynamic model in terms of Milankovitch elements is given for geostationary transfer orbits (GTOs), which includes the Earth's oblateness, luni-solar perturbations, atmospheric drag and solar radiation pressure (SRP). The orbital dynamic model is verified through a numerical simulation compared with the Semi-analytic Tool for End of Life Analysis software (STELA) by CNES. We find that if the area-to-mass ratio of the object is relatively large, the SRP will have a significant impact on the long-term evolution of GTOs. Then, the long-term dynamical evolution and orbital resonances of rocket upper stages in inclined geostationary transfer orbits (IGTOs) are studied. It has been found that the luni-solar secular resonances, which are inclination-dependent-only, play a leading role in the long-term evolution of IGTOs. By comparing and analyzing long-term dynamical evolution of orbits with different initial inclinations, the effects of luni-solar secular resonances are studied in details. Finally, a mitigation method for IGTO objects by utilizing luni-solar secular resonances is proposed, in which the eccentricity growth caused by the resonances is used for an early atmospheric re-entry.
       
  • Impact of solar radiation pressure modeling on orbital dynamics in the
           vicinity of binary asteroids
    • Abstract: Publication date: Available online 7 September 2019Source: Acta AstronauticaAuthor(s): Isabelle Jean, Alfred Ng, Arun K. Misra Missions to asteroids are now an important component of the space exploration program of major space agencies in the world, with the goal of better understanding the formation of the Solar system and learn about their dynamics to be able to react in case of a possible collision with the Earth. As binary asteroids compose approximately 16% of near Earth asteroids, they are getting more attention from researchers. One mission is currently being planned to binary asteroid system 65803 Didymos. This mission motivates research on the dynamics of a spacecraft near a binary asteroid. Since the primary bodies of these binary systems have small masses, perturbations like the Solar Radiation Pressure (SRP) or the shape of the primary bodies have a great influence on the dynamics of a spacecraft in their vicinity. Studies that already exist on the effect of the SRP on the dynamics of a spacecraft near binary asteroid systems have mostly used low-fidelity SRP acceleration models, such as the cannonball model or simple flat plate model with a purely reflecting spacecraft. This study shows how the choice of the model influences the strength of the SRP acceleration acting on the spacecraft and how it is possible to take advantage of the choice of the nominal attitude of the spacecraft to influence how the SRP affects the spacecraft dynamics when using a more complex SRP acceleration model. Various types of trajectories are studied, with different results and conclusions.
       
  • Space systems resilience optimisation under epistemic uncertainty
    • Abstract: Publication date: Available online 7 September 2019Source: Acta AstronauticaAuthor(s): Gianluca Filippi, Massimiliano Vasile, Daniel Krpelik, Peter Zeno Korondi, Mariapia Marchi, Carlo Poloni This paper introduces the concept of Resilience Engineering in the context of space systems design and a model of Global System Reliability and Robustness that accounts for epistemic uncertainty and imprecision. In particular, Dempster-Shafer Theory of evidence is used to model uncertainty in both system and environmental parameters. A resilience model is developed to account for the transition from functional to degraded states, and back, during the operational life and the dependency of these transitions on system level design choices and uncertainties. The resilience model is embedded in a network representation of a complex space system. This network representation, called Evidence Network Model (ENM), allows for a fast quantification of the global robustness and reliability of system. A computational optimisation algorithm is then proposed to derive design solutions that provide an optimal compromise between resilience and performance. The result is a set of design solutions that maximise the probability of a system to recover functionalities in the case of a complete or partial failure and at the same time maximises the belief in the desired target value of the performance index.
       
  • The active space debris removal mission RemoveDebris. Part 1: from concept
           to launch
    • Abstract: Publication date: Available online 6 September 2019Source: Acta AstronauticaAuthor(s): Jason L. Forshaw, Guglielmo S. Aglietti, Simon Fellowes, Thierry Salmon, Ingo Retat, Alexander Hall, Thomas Chabot, Aurélien Pisseloup, Daniel Tye, Cesar Bernal, François Chaumette, Alexandre Pollini, Willem H. SteynABSTRACTThis is the first of two companion papers that describe the development of the RemoveDEBRIS; mission. This first article focusses on the mission design and hardware development up to the delivery of the spacecraft to the launch authority. The Secord article describes the in-orbit operations.The European Commission funded RemoveDebris mission has been the world’s first Active Debris Removal (ADR) missions to demonstrate, in orbit, some cost effective key technologies, including net and harpoon capture; and elements of the whole sequence of operations, like the vision-based navigation, ultimately planning to terminate the mission with the deployment of the dragsail to de-orbit the craft. The mission has utilized two 2U CubeSats as artificial debris targets released from the main 100 kg satellite, to demonstrate the various technologies.This paper examines the design of the mission from initial concepts through to Manufacture, Assembly Integration and Testing of the payloads, up to launch, and apart from a general consideration of the mission, will focus on the elements of design and testing that differ from a conventional mission.
       
  • Equivalent two-dimensional numerical simulation of an ECR neutralizer
    • Abstract: Publication date: November 2019Source: Acta Astronautica, Volume 164Author(s): Yuliang Fu, Juan Yang, Yizhou Jin, Xu Xia, Haibo Meng The electron cyclotron resonance (ECR) neutralizer is a component of the 10-cm electron cyclotron resonance ion thruster (ECRIT) and its performance has a great effect on the overall performance of the thruster. To clarify the mechanisms of electron extraction of the ECR neutralizer, a particle-in-cell/Monte Carlo collision (PIC/MCC) solver was developed to simulate the plasma in the ECR neutralizer. This paper equivalently simplified the three-dimensional model of the ECR neutralizer into a two-dimensional axisymmetric one according to experimental results and the circumferential electric drift of charged particles. Hence, a two-dimensional three-velocity component full-particle calculation model was used in the solver. Through analyzing ECR heating mechanism, the validity and accuracy of the equivalent ring antenna were discussed. The distribution of plasma parameters and extracted electron current were obtained by tracking the motion of electrons and singly charged xenon ions, simulating the elasticity, excitation, ionization and Coulomb collisions. The results showed that the density of neutral particles can be adjusted to coincide simulation current with experiment. It was also found that due to the magnetic field gradient, plasma will migrate to the magnetic well, where the ion was in dominant position to form a potential well and hinder the extraction of electron.
       
  • Effect of solar cell efficiency and flight condition on optimal flight
           control and energy performance for Z-shaped wing stratospheric solar
           aircraft
    • Abstract: Publication date: November 2019Source: Acta Astronautica, Volume 164Author(s): Mingjian Wu, Zhiwei Shi, Tianhang Xiao, Z.L.J. Chen, Haisong Ang The parameters of solar cell efficiency, flight date of year, latitude and sun elevation angle are important to energy conversion of solar cells, which affect optimal flight control and energy performance of Z-shaped solar aircraft. This work is mainly focusing on studying the effect of varying these parameters on optimum attitude planning, optimum wing morphing control and maximum net energy input for Z-shaped solar aircraft. This study shows that, with higher solar cell efficiency, the solar aircraft prefers to more daylight hours configured as Z-shaped wing, larger morphing angle and larger angle between projection of sunlight and wingspan axis, which enhances to achieve more net power input. For the middle and high latitudes in winter with low sun elevation angles, the Z-shaped solar aircraft tends to large morphing angles and small angles between projection of sunlight and wingspan axis. For the low and middle latitudes of the other seasons with high sun elevation angles, it prefers to small morphing angles to make its central wing totally expose to the sunlight, and orient flight attitude to make the projection of sunlight coincide with wingspan axis. Moreover, the research on the impact of solar cell efficiency shows that, compared with the planar wing, the optimal Z-shaped wing is more effective to improve energy margin and extend perpetual flight days with the same increase of solar cell efficiency. The results can provide valuable engineering reference on optimum wing morphing control and optimum attitude planning for Z-shaped stratospheric solar aircraft.
       
  • Iron overload as a high risk factor for microgravity-induced bone loss
    • Abstract: Publication date: November 2019Source: Acta Astronautica, Volume 164Author(s): Xin Chen, Jiancheng Yang, Dandan Dong, Huanhuan Lv, Bin Zhao, Yanru Xue, Peng Shang Exposure to microgravity during long-term habitation in space results in numerous physiological alterations in the human body. Among them, reduction in bone mineral density is well known as one of the most important changes, which limits further space exploration by humans. Although numerous studies have been conducted on microgravity-induced bone loss, the explicit mechanism behind its occurrence has not been fully elucidated. Even though mechanical unloading has been generally accepted as a dominant cause of microgravity-induced bone loss, the risks of iron-loading and oxidative damage due to increased iron stores and dietary iron intake during spaceflight have attracted much attention, especially in bone. Indeed, excessive iron accumulation has been found in astronauts exposed to microgravity during spaceflight. Moreover, a great deal of evidence from clinical, animal, and cellular studies indicates that iron-loading has direct adverse effects on bone metabolism. This review summarizes the latest findings on bone loss and iron status in microgravity conditions, as well as the association between iron-loading and bone abnormalities. We discuss the possible mechanisms of iron overload-induced skeletal involution. Finally, we hypothesize that, in addition to mechanical unloading, iron overload due to long-term spaceflight missions is a high risk factor for microgravity-induced bone loss. The underlying mechanism by which it occurs is iron-loading that leads to an imbalance in bone remodeling, involving bone formation and bone resorption, mediated by oxidative stress via the Fenton reaction.
       
  • Stellar Engines: Design Considerations for Maximizing Acceleration
    • Abstract: Publication date: Available online 4 September 2019Source: Acta AstronauticaAuthor(s): Matthew E. Caplan Stellar engines, megastructures used to control the motion of a star system, may be constructible by technologically advanced civilizations and used to avoid dangerous astrophysical events or transport a star system into proximity with another for colonization. This work considers two designs for stellar engines, for both human applications in the solar system and for advanced civilizations around arbitrary stars more generally, and presents analytic calculations of the maximum acceleration and deflection of a star in its galactic orbit. The first is a large ‘passive’ solar sail, similar to that proposed by Shkadov, which we find produces accelerations of order 10−12m/s2 for sun-like stars. The second ‘active’ engine uses a thermonuclear driven jet, as in a Bussard ramjet, which collects matter from the solar wind to drive He fusion. This engine requires additional mass to be lifted from the sun, beyond what is provided by the nascent solar wind, but may achieve accelerations up to 10−9m/s2 producing deflections of 10 pc in as little as 1 Myr for a sun-like star. While passive engines may be insufficient for catastrophe avoidance on short timescales, they can produce arbitrary deflections of a star in its galactic orbit over a stellar lifetime. Active engines are sufficient for retrograde galactic orbits or galactic escape trajectories, which we argue are useful to expansionist civilizations. These populations of stars may be candidates for observationally detecting megastructures.
       
  • Multidisciplinary Modeling and Simulation Framework for Launch Vehicle
           System Dynamics and Controlt1
    • Abstract: Publication date: Available online 3 September 2019Source: Acta AstronauticaAuthor(s): Lâle Evrim Briese, Paul Acquatella B, Klaus Schnepper Future concepts and key technologies for reusable launch vehicles are currently investigated by the DLR project Akira, focusing on vertical takeoff and horizontal landing (VTHL), as well as horizontal takeoff and horizontal landing (HTHL) concepts. Dedicated developments of multidisciplinary frameworks for launch vehicle modeling and preliminary design optimization have been presented in the relevant literature. These activities are often performed by several independent and discipline-specific tools; such an approach can only account for limited interactions of the involved disciplines with the overall system dynamics.Therefore, the objective of this paper is to focus on a multidisciplinary launch vehicle dynamics modeling, guidance, and control framework to support reusable launch vehicle design activities at DLR while taking into account the highly interconnected disciplines involved and changing environmental conditions. The modeling framework is based on the object-oriented, multidisciplinary, and equation-based modeling language Modelica. Dedicated 3-DOF and 6-DOF model implementations, covering the kinematics and dynamics formulation, environmental effects, aerodynamics, and propulsion models are presented.Within this framework, a method to obtain a direct connection between 3-DOF and 6-DOF models is shown. This is done by considering results from the trajectory optimization package ‘trajOpt’ in combination with nonlinear 6-DOF inverse models obtained automatically by Modelica. Angular rates and resulting moments can be retrieved by this intermediate 6-DOF modeling approach for subsequent controllability studies. We discuss some of these benefits in terms of nonlinear flight control simulations for an HTHL reusable launch vehicle concept.
       
  • Influence of the secondary flow control on the transverse gaseous
           injection flow field properties in a supersonic flow
    • Abstract: Publication date: Available online 3 September 2019Source: Acta AstronauticaAuthor(s): Min-zhou Dong, Jun Liao, Gautam Choubey, Wei Huang The supersonic mixing process is a critical issue for the design of the scramjet engine. In this paper, the secondary flow control concept has been proposed and studied in order to strengthen the mixing process between the fuel and the incoming flow with the freestream Mach number being 3.75, and the influence of the secondary flow position on the mixing augmentation mechanism has been evaluated as well. The obtained results show that the secondary flow control concept has a great impact on the mixing augmentation mechanism in the transverse injection flow field, and the parameters should be properly selected, especially for the secondary flow position. When the upstream hole is close to the jet flow and the downstream hole is far away from the jet flow, the mixing process between the fuel and the incoming flow could be promoted, namely Case 1 is the best choice for the mixing augmentation in the range considered in the current study. This is due to the variation of the separation zone generated upstream of the fuel jet, and this issue should be evaluated quantitatively. The hydrogen plume shape changes from a “kidney” to a “lamp”, and it is far away from the bottom wall in Case 1. The premature ignition phenomenon could be prevented properly in Case 1.
       
  • Evaluating the Effectiveness of Common Aerospace Materials at Lowering the
           Whole Body Effective Dose Equivalent in Deep Space
    • Abstract: Publication date: Available online 22 August 2019Source: Acta AstronauticaAuthor(s): D.K. Bond, B. Goddard, R.C. Singleterry, S. Bilbao y Leóna Materials have a primary purpose in the design of space vehicles, such as fuels, walls, racks, windows, etc. Additionally, each will also affect space radiation protection. The shielding capabilities of 59 materials are evaluated for deep space travel, in terms of whole body effective dose equivalent and # of NucleonsVolume. The hydrogen rich materials were evaluated further using # of Hydrogen AtomsMass and # of Hydrogen AtomsVolume. All evaluated materials, through density, composition, and shielding ability, can be categorized into three groups: metals, polymers and composites, and fuels, hydrides, and liquid gases. The analyses presented in the article shows that a “magic” material is not possible; however polymers and composites should be used instead of metals, if they can serve their primary purpose. Polyethylene and magnesium borohydride are shown to be the best feasible materials from this sample. Thermal neutron absorbers, 6Li and 01B, do not have a significant effect on ED. Alloying of materials, such as aluminum, for strengthening purposes, do not increase ED. Ultimately, a space vehicle is a system of systems and radiation protection must be one of them.
       
  • Study of the effect of DC high-voltage electric fields on the regression
           rate of PMMA
    • Abstract: Publication date: Available online 21 August 2019Source: Acta AstronauticaAuthor(s): Xiaolong Yang, Zhijun Wei, Zelin Zhang, Jingjia Zhang Due to great demands on solid rocket motors and solid ramjets for thrust control, a study of the effect of high-voltage electric fields on the regression rate of polymethyl methacrylate (PMMA) has been undertaken. The flame shape was recorded by a CMOS camera. The regression rate of PMMA was measured. A numerical model of fluid-solid coupling, which is based on experiment and considers physico-chemical phenomena associated with the flame-field interaction process, has been developed to explain experimental observations. In order to reduce the computational workload, the radiation loss, including the soot radiation is not considered in the numerical simulation. The mechanism of the effect of electric fields on the regression rate of PMMA is analysed. The numerical simulation shows that the change of the regression rate of a PMMA tip under the action of electric fields is consistent with experimental results. Studies show that electric fields can change the regression rate of PMMA, increasing it by about 38%. The regression rate on the burning surface is increased when subjected to positive electric fields. Under a negative electric field, part of the burning surface is subjected to an increased regression rate, and some thereof is subjected to a decreased regression rate. The effect of electric fields on the regression rate of PMMA is mainly due to the interaction of buoyancy and the electric field induced volumetric body forces.
       
  • Experimental and numerical investigation of an embedded rocket ramjet
           combustor
    • Abstract: Publication date: Available online 21 August 2019Source: Acta AstronauticaAuthor(s): Guanlin Fang, Zhijun Wei, Zhiwen Wu, Rui Du, Ningfei Wang This study proposes an embedded rocket ramjet, a novel combined ramjet engine, that can operate at high altitude and low pressure. The embedded rocket ramjet combustor is investigated experimentally and numerically to predict its characteristics. Experiments are performed in a direct-connect ground test facility to measures the wall pressure and total pressure at the combustor exit. Three-dimensional Navier–Stokes equations and species transport equations are solved numerically. A compressible reactive shear stress transport k-ω turbulence model with reduced chemical kinetics of a surrogate model for kerosene is used to study the flow characteristics and overall performance of the combustor. Test results show that the embedded rocket can significantly increase the combustor pressure. Numerical analysis shows that the embedded rocket increases the mixing efficiency, combustion efficiency, and thrust but decreases the specific impulse.
       
  • Attitude motion path planning on Lyapunov periodic orbits in the circular
           restricted three-body problem
    • Abstract: Publication date: Available online 21 August 2019Source: Acta AstronauticaAuthor(s): Mo-yao Yu, Ya-zhong Luo The path of attitude motion for a rigid body in fully nonlinear Lyapunov periodic orbits is planned in the restricted three-body problem. The attitude dynamic characteristics in phase plane are analyzed, and the path constraint conditions are proposed to avoid the divergence of phase trajectories. Then, the path planning method for the three-body problem is proposed by employing the Pseudospectral method. Based on this, solving strategy of attitude-orbit coupled periodic solutions is obtained by adding event constraint conditions. Compared with previous work, the proposed method effectively avoids the divergence of attitude motion and saves a large amount of work on determining the initial guess. To verify the effectiveness of the proposed method, a large number of planning work are carried out. Besides, the paper addresses the question that how translational motions and configuration of the spacecraft affect the planned results.
       
  • An Extra Degree-of-Freedom Model for Combined Spacecraft Attitude Control
           with Unilateral Contact Constraint
    • Abstract: Publication date: Available online 20 August 2019Source: Acta AstronauticaAuthor(s): Yuchen She, Shuang Li This paper investigates the attitude control problem of a two-body combined spacecraft by considering the unilateral contact constraint on the active spacecraft’s end-effector. Previous work has shown that this constraint may cause a relative sliding motion between the end-effector and the target, which has a large impact on the combined spacecraft dynamics and postcapture control process. In this paper, an extra degree-of-freedom approach is adopted and a new dynamical model is developed to efficiently describe the movement of the combined spacecraft in both rigid connecting and relative motion modes. A new control law is also developed to reduce the relative sliding motion between the end-effector and the target while controlling the attitude of the combined system. Simulation results show that the extra degree-of-freedom model proposed in this paper has the correct dynamic properties and that the newly developed controller is a significant improvement over traditional PD controllers in maintaining the geometric configuration of the combined spacecraft.
       
  • Environmental Testing and Characterization of Fibre Reinforced Silica
           Aerogel Materials for Mars Exploration
    • Abstract: Publication date: Available online 19 August 2019Source: Acta AstronauticaAuthor(s): Helena Rocha, Ugo Lafont, Christopher Semprimoschnig Aerogels are promising materials for thermal insulation applications for Mars exploration mission. To assess the use of hydrophobic silica based aerogels for the specificity of the Mars environment, the samples were exposed to a laboratory simulation of the Mars environment, resorting to gamma radiation exposure and thermal cycling tests. To validate their use and study the effect of the simulated Mars environment on their thermal, mechanical and chemical properties, the aerogel materials were characterized before and after that environmental testing, to evaluate and identify eventual changes. Outgassing tests were also conducted. We found minor changes on the aerogels properties, showing that the materials can keep their thermal insulation performance after thermal cycling tests and that the storage modulus during dynamic mechanical analysis in compression mode was improved.
       
  • Effects of a new-type inner-canopy illuminant and light quality on spring
           wheat growth in CELSS
    • Abstract: Publication date: Available online 19 August 2019Source: Acta AstronauticaAuthor(s): Yunze Shen, Shuangsheng Guo, Gu Zeng Traditional plant illumination in Controlled Ecological Life Support System (CELSS) has been generally roof illumination (RI). In order to improve the utilization efficiency of light energy for cultivating plants, a new-type inner-canopy illuminant (ICI), which was embedded among the stems and leaves of spring wheat, was applied in the research. The experimental group was 50% ICI+ 50% RI, while the control group was 100% RI, both of which consumed the same total electric power. For each of the two groups, six different qualities of light were separately used to study the effects of red, blue and green light under simulated CELSS conditions. By comparing the two groups, it was found that the PPFD (Photosynthetic Photon Flux Density) on the leaf surface was increased in the experimental group, resulting in a shortened growth period, higher net photosynthetic rate (Pn), lower plant height, larger leaf area index (LAI), higher biomass and seed yield. The increased percent of PPFD across the leaf surface under the experimental group on average reached 8.6%-14.6% within 30 days, while PPFD increased by 3.9% - 8.0% in 70 days after sowing. An increased seed yield as large as 19.6% per day was achieved in the experimental group. In addition, Red, blue and green light contributed differently to photosynthetic efficiency. Firstly, red light promoted the shortening of growth period, while blue and green light had no significant effect on it. For example, reducing 20% red light caused a 12- or 13-day prolongation of the growth period. Secondly, increasing the ratio of red/blue could increase Pn, plant height, leaf area index, total biomass and seed yield. Thirdly, it can be seen that the green light did not contribute to photosynthesis directly, but it still had an important role in spring wheat growth. Green light significantly increased the tiller number and LAI, as well as total biomass and seed yield, but daily seed yield was not increased under 10% or more green light. The total seed yield was the highest in combination of 80% red + 10% blue + 10% green light, but the highest daily seed yield was achieved under 90% red + 10% blue light for a shorter growth period. The above results should provide a useful reference for choosing the suitable plant lighting method in CELSS.
       
  • Impact probability computation for NEO resonant returns through a
           polynomial representation of the Line of Variations
    • Abstract: Publication date: Available online 12 July 2019Source: Acta AstronauticaAuthor(s): Marcello Sciarra, Matteo Losacco, Daniele Santeramo, Pierluigi Di Lizia A differential algebra based representation and propagation of the Line of Variations for Near Earth Objects impact monitoring is presented in this paper. The Line of Variations is described at the initial epoch by a high-order polynomial that is propagated forward in time. An Automatic Domain Splitting algorithm is embedded in the numerical integrator, in such a way that when the polynomials truncation error becomes too large, the line is split as many times as necessary to meet accuracy requirements. The Line of Variations is propagated forward in time until an intersection with a properly defined target plane occurs for all the generated subdomains. The subdomains are then projected onto the target plane to compute the impact probability by numerically integrating an associated one-dimensional probability density function. The proposed approach is applied to several test-cases to assess the performance of the method for the different possible shapes of the initial confidence region. Starting from a case of direct encounter, the technique is tested up to the case of a resonant return, which features critical nonlinearities.
       
  • Zinc oxide aluminum doped slabs for heat-eliminating coatings of
           spacecrafts
    • Abstract: Publication date: Available online 10 July 2019Source: Acta AstronauticaAuthor(s): E.V. Shirshneva-Vaschenko, P.S. Shirshnev, Zh.G. Snezhnaia, L.A. Sokura, V.E. Bougrov, A.E. Romanov This paper discuss a possibility for using a thin-film functional coating based on transparent conducting thin films of aluminum doped zinc oxide (AZO) as a heat-eliminating material on the surface of a spacecraft. The structure of the functional coating has been chosen taking into account the plasmonic properties of AZO and silver and represents the AZO slabs with embedded silver nanoparticles deposited on AZO layer and AZO slabs with embedded silver nanoparticles deposited on thin film fused quartz layer. The paper contains COMSOL finite element simulations of the scattering cross section for thermal radiation in the IR band in the case the investigated coating deposited on a reflective aluminum film, and absorption cross section in the near UV and visible spectral bands when the coating deposited on silicon solar panels. The calculations demonstrate an increase in the scattering cross-section in the spectral band of blackbody radiation by several orders of magnitude, with the maximum in the scattering spectrum of the AZO slabs/ AZO /Al structure corresponding to the maximum intensity of the blackbody thermal radiation, which has been heated to 100 °C in the case the lattice period of the AZO slabs is equal to the resonance wavelength for AZO. Also an increase in the absorption cross-section of AZO slabs/ AZO /Si structure in visible spectral band is observed corresponding to plasmon absorption of embedded silver nanoparticles.
       
  • Radio seti observations of the interstellar object 'oumuamua
    • Abstract: Publication date: Available online 1 July 2019Source: Acta AstronauticaAuthor(s): Gerald R. Harp
       
  • Composite weighted average consensus filtering for space object tracking
    • Abstract: Publication date: Available online 29 June 2019Source: Acta AstronauticaAuthor(s): Hao Chen, Jianan Wang, Chunyan Wang, Jiayuan Shan, Ming Xin In this paper, a composite weighted average consensus filtering (CWACF) algorithm is proposed for space object tracking by combining two distributed heterogeneous nonlinear filters. In light of the sensors’ different sensing accuracy and computational capability, extended Kalman filter (EKF) and sparse-grid quadrature filter (SGQF) are compositely adopted on different sensors as local filters. Then, estimates from neighbours are fused based on the weighted average consensus framework to attain better estimation performance. Moreover, it is proved that the estimation error is exponentially bounded in mean square. The performances of the proposed algorithm, the distributed extended Kalman filtering (DEKF) and the distributed sparse-grid quadrature filter (DSGQF) are compared in a space object tracking problem.
       
  • Least-squares solution of a class of optimal space guidance problems via
           Theory of Connections
    • Abstract: Publication date: Available online 18 June 2019Source: Acta AstronauticaAuthor(s): Roberto Furfaro, Daniele Mortari In this paper, we apply a newly developed method to solve boundary value problems for differential equations to solve optimal space guidance problems in a fast and accurate fashion. The method relies on the least-squares solution of differential equations via orthogonal polynomials expansion and constrained expression as derived via Theory of Connection (ToC). The application of the optimal control theory to derive the first order necessary conditions for optimality, yields a Two-Point Boundary Value Problem (TPBVP) that must be solved to find state and costate. Combining orthogonal polynomials expansion and ToC, we solve the TPBVP for a class of optimal guidance problems including energy-optimal landing on planetary bodies and fixed-time optimal intercept for a target-interceptor scenario. The performance analysis in terms of accuracy shows the potential of the proposed methodology as applied to optimal guidance problems.
       
  • Influence of flow parameters on the dynamic performance for the supersonic
           jet element
    • Abstract: Publication date: Available online 17 June 2019Source: Acta AstronauticaAuthor(s): Y. Xu, G.Q. Zhang The influence of the inlet and outlet flow parameters on the dynamic performance for the supersonic jet element have been investigated numerically in details. And the precision and errors accumulation of the numerical method has also been estimated. The influence of the main jet pressure and the mass flow rate of the control flow on the output thrust as well as the switching time have been deeply studied. The results have shown that increasing the mass flow rate of the control flow can shorten the switching time and increase the effective thrust slightly, but it also can enhance the unsteadiness of flow in the wall-attached work state but decrease the energy utilization rate of the supersonic jet flow component. The effective thrust generated by the cold air is larger than the gas work medium. And the switching time for the gas working medium is also shorter, which is more conducive to the completion of the switch process. The vortical structures at different switching time together with the force variations inside the jet element have been obtained computationally and analyzed in details.
       
  • Calorimetric study on electrolytic decomposition of hydroxylammonium
           nitrate (HAN) ternary mixtures
    • Abstract: Publication date: Available online 5 June 2019Source: Acta AstronauticaAuthor(s): Wai Siong Chai, Jitkai Chin, Kean How Cheah, Kai Seng Koh, Tengku F.Wahida Ku Chik Electrolytic decomposition of hydroxylammonium nitrate (HAN) is appealing for development of chemical micropropulsion system due to its effectiveness in thermal management. In this paper we present the decomposition characteristics and behaviour of various HAN ternary mixtures prepared according to 0 Oxygen Balance (0 OB). There are multiple stages of decomposition depending on the type of fuels added into the HAN solution. While concentrated HAN solution (73 wt%) has only single stage of decomposition, the saccharides-based HAN ternary mixtures has three stages reaction with increased energy release. The addition of nitrogen-rich compounds has sustained the electrolytic decomposition process into the second stage of reaction, which produced the highest decomposition temperature. The study also reveals a linear relationship between the electrical resistivity of HAN ternary mixture and reaction rate in the first stage of reaction, indicating the presence of Joule heating in the process. The influence of electrical resistivity of the ternary mixture became negligible in the second stage of reaction. This work concludes the importance of combined electrical and thermal energy in the first stage decomposition of HAN ternary mixtures.Graphical abstractImage 1
       
  • An optimized analytical solution for geostationary debris removal using
           solar sails
    • Abstract: Publication date: Available online 5 June 2019Source: Acta AstronauticaAuthor(s): Patrick Kelly, Riccardo Bevilacqua Debris in geostationary Earth orbits is often uncontrollable, consisting of launch-vehicle upper stages and non-operational payloads. To help mitigate orbital debris congestion, a solar-sailing satellite concept is proposed which retrieves and relocates large debris for placement into the “graveyard” orbit above the geostationary regime. This work derives an analytical deorbit solution based on Lyapunov control theory combined with the calculus of variations. A dynamic constraint vector is introduced as a result, which dictates the orbital response of a spacecraft to some controlled perturbation. The resulting controller is simulated for various solar sailing platforms to characterize deorbit capability based on a system's area to mass ratio. User design parameters in these solutions are then optimized using a Particle Swarm Optimizer (PSO) to produce robust, locally time optimal solutions for orbital debris removal using solar sails. Solar sail deorbit times are shown to decrease as the reflective area increases, with additional performance dependencies based on the Earth's relative position from the sun.
       
  • Uncertain parameters analysis of powered-descent guidance based on
           Chebyshev interval method
    • Abstract: Publication date: Available online 26 May 2019Source: Acta AstronauticaAuthor(s): Long Cheng, Hao Wen, Dongping Jin This paper focuses on the powered-descent guidance (PDG) problem involving uncertain-but-bounded parameters. An efficient numerical algorithm based on the high approximation accuracy of the Chebyshev series expansion is presented to solve the nonlinear optimal control problem with interval uncertain parameters. First, an infinite number of uncertain optimal control problems is translated into a series of deterministic optimal control problems by exploiting the Chebyshev interval inclusion. Subsequently, the deterministic optimal control problem is solved by a convex optimization method based on the lossless convexification of the PDG problem. Afterwards, these techniques are used to generate the enclosure of the PDG trajectory with uncertainty and the upper and lower bounds of the minimum fuel consumption during the pinpoint landing mission. Finally, the effectiveness and superiority of the proposed approach are validated by illustrative numerical simulations.
       
  • Switching mechanism investigation for the supersonic jet element:
           Deflection, attachment and adjustment stages
    • Abstract: Publication date: Available online 22 May 2019Source: Acta AstronauticaAuthor(s): Y. Xu, G.Q. Zhang Based on the unsteady viscous flow simulation, the flow characteristics inside the supersonic jet Element have been investigated numerically. The results have revealed that once the specific structures of the supersonic jet element are finalized, even if the boundary conditions remain unchanged, the corresponding internal flow will also shows strong unsteady in a certain range of primary gas source pressure. The instability of the main vortex center is a main reason to make the output thrust of the supersonic jet components fluctuate all the time in the attached wall condition. At the deflection of the jet stage, once the static pressure for the right side of the wedge exceeds the left side, the transverse expansion for the stripping zone near the right output channel entrance can play a significant role in making the primary jet deflect successfully. When the jet starts to attach the wall layer, due to the “Coanda” effect, the jet also can attach the layer successfully even though the corresponding control flow is totally closed. When the jet enters the adjustment stage, the thrust changes process for the left and right outputs will experience two typical stages: adjusting and adjusted stages. The corresponding vortex structures at different switching time together with the force variations etc. inside the jet Element have been obtained computationally and analyzed in details.
       
  • A techno-economic analysis of asteroid mining
    • Abstract: Publication date: Available online 10 May 2019Source: Acta AstronauticaAuthor(s): Andreas M. Hein, Robert Matheson, Dan Fries Asteroid mining has been proposed as an approach to complement Earth-based supplies of rare earth metals and supplying resources in space, such as water. However, existing studies on the economic viability of asteroid mining have remained rather simplistic and do not provide much guidance on which technological improvements would be needed for increasing its economic viability. This paper develops a techno-economic analysis of asteroid mining with the objective of providing recommendations for future technology development and performance improvements. Both, in-space resource provision such as water and return of platinum to Earth are considered. Starting from first principles of techno-economic analysis, gradually additional economic and technological factors are added to the analysis model. Applied to mining missions involving spacecraft reuse, learning curve effect, and multiple spacecraft, their economic viability is assessed. A sensitivity analysis with respect to throughput rate, spacecraft mass, and resource price is performed. Furthermore, a sample asteroid volatile mining architecture based on small CubeSat-class spacecraft is presented. It is concluded that key technological drivers for asteroid mining missions are throughput rate, number of spacecraft per mission, and the rate in which successive missions are conducted. Furthermore, for returning platinum to Earth, market reaction strongly influences its economic viability.
       
  • A new principle of separation of gas mixtures in non-stationary
           transitional flows
    • Abstract: Publication date: Available online 10 May 2019Source: Acta AstronauticaAuthor(s): Artem Yakunchikov, Vasily Kosyanchuk The paper studies non-stationary gas flow in a transitional regime in a region with a moving boundary. Interest in this problem is due to the search for new principles of gas separation, which can be implemented in practice as a microelectromechanical system (MEMS). The diminutiveness of such systems makes them relevant for aerospace applications. To solve the problem, the method of event-driven molecular dynamics (EDMD) was used, which was extended by the authors to the case of computational domain with moving boundaries (simulating moving elements of the device). A new principle of operation of the separation device was proposed and investigated. It was obtained that the separation coefficient of proposed device can be significantly higher than that of the diffusion method.
       
  • Protection of inflatable modules of orbital stations against impacts of
           particles of space debris
    • Abstract: Publication date: Available online 27 April 2019Source: Acta AstronauticaAuthor(s): E.P. Buslov, I.S. Komarov, V.V. Selivanov, V.A. Titov, N.A. Tovarnova, V.A. Feldstein Provides the describing the impact micrometeoroid and orbital debris (MMOD) on the Micrometeoroids and Debris Protection System (MDPS) for inflatable modules for lunar orbital application. MDPS flexibility and compactness are achieved by the use as screens packets fabric materials. These materials have effective crushing properties due to absorption of impact energy in the breakdown of tissue layers. The soft materials used to create inflatable modules are proving they can perform just as well as more rigid structures in space, but the impact physics is different. The development of method of describing the impact MMOD linked with this type of shields will lead to an improvement in their design, in terms of mass, efficiency and costs. The results are hypervelocity impact test campaign on the MDPS for inflatable modules for lunar orbital application presented.
       
  • Rapid trajectory design in complex environments enabled by reinforcement
           learning and graph search strategies
    • Abstract: Publication date: Available online 25 April 2019Source: Acta AstronauticaAuthor(s): A. Das-Stuart, K.C. Howell, D. Folta Designing trajectories in dynamically complex environments is challenging and easily becomes intractable. Recasting the problem may reduce the design time and offer global solutions by leveraging phase space mapping patterns available as accessible regions, and the application of search techniques from combinatorics. A computationally efficient search process produces potential trajectory concepts to meet unique design requirements over a broad range of mission types, including low-thrust scenarios. A successful framework is summarized in terms of four components: (i) Accessible regions - establishing reachable regions within the design space for a given thruster/engine capability. (ii) Database exploitation - discretization of well known dynamical structures to form a searchable 2D or 3D volume or map. (iii) Automated pathfinding - exploiting machine learning techniques to determine the transport sequence to deliver an efficient path. (iv) Convergence/optimization - once the transport sequence is determined as a globally efficient concept, it is optimized locally by traditional numerical strategies.
       
  • Design of fault-tolerant microprocessors for space applications
    • Abstract: Publication date: Available online 16 April 2019Source: Acta AstronauticaAuthor(s): M.S. Gorbunov We discuss the main design concepts for fault-tolerant microprocessors, Instruction Set Architectures (ISA) of microprocessors for space applications and the achievable characteristics considering the KOMDIV microprocessors designed by SRISA. The trade-off between the fault-tolerance, performance and power consumption is considered for microprocessors designed using the silicon-on-insulator (SOI) and bulk CMOS technologies.
       
  • Dynamics of the gas-dust cloud observed in the upper atmosphere on October
           26, 2017
    • Abstract: Publication date: Available online 4 April 2019Source: Acta AstronauticaAuthor(s): Sergey Nikolayshvili, Stanislav Kozlov, Yulii Platov, Andrey Repin The results of the study of the gas-dust cloud of solid fuel combustion products dynamics formed under a rocket stages separation are presented. The sequence of the digital images obtained in the twilight condition at a distance of ∼1500 km from the missile trajectory was analyzed. The height of the cloud center reaches up to ∼900 km, and its diameter is ∼2000 km. The glow of the cloud is determined by the scattering of sunlight on dispersed particles of the combustion products. The obtained data allow to specify the dispersed composition of the cloud and dynamic parameters of its development. The proposed methodology can be used to clarify the physical picture of the interaction of the combustion products of solid propellant with the environment, as well as environmental conditions and processes in the upper atmosphere.
       
  • Fault detection and diagnosis algorithms for transient state of an
           open-cycle liquid rocket engine using nonlinear Kalman filter methods
    • Abstract: Publication date: Available online 29 March 2019Source: Acta AstronauticaAuthor(s): Jihyoung Cha, Sangho Ko, Soon-Young Park, Eunhwan Jeong This paper deals with an application of the fault detection and diagnosis algorithm based on nonlinear Kalman filter methods for transient state of an open-cycle liquid propellant rocket engine. In order to develop the algorithm, we designed two types of the nonlinear Kalman filter which are the extended Kalman filter and unscented Kalman filter with non-linear model of the liquid propellant rocket engine. Then using the measurement data of some important parameters of the engine, the residuals from the nonlinear Kalman filters are obtained. Using the residuals, we can detect and diagnose faults in the components of the engine by using the multiple model method. To confirm the fault detection and diagnosis algorithm, we developed mathematical model of an open-cycle liquid propellant rocket engine and artificially injected various faults such as decreasing turbopump efficiency. And then, perform the fault detection and diagnosis algorithm and check the performance of the algorithm. This process is numerically demonstrated for the open-cycle liquid propellant rocket engine under start-up process by using the simulated measurement data from the mathematical model of the engine.
       
  • High-order state transition polynomial with time expansion based on
           differential algebra
    • Abstract: Publication date: Available online 28 March 2019Source: Acta AstronauticaAuthor(s): Zhen-Jiang Sun, Pierluigi Di Lizia, Franco Bernelli-Zazzera, Ya-Zhong Luo, Kun-Peng Lin In this study, a high-order state transition polynomial with time expansion (STP-T) method is developed to propagate an initial orbital state around its reference value to a variable final time based on the differential algebra (DA) technique. STP-T is a high-order Taylor polynomial of the final orbital state expanded around the reference initial state and reference propagation time. Since the final state usually shows different nonlinearity with respect to different components of initial state and propagation time, a weighted-order scheme is combined with STP-T, which enables the STP-T to have higher orders on the components with higher nonlinearity and lower orders on the components with lower nonlinearity. Then, an error estimation method is presented, which can a priori provide the error profiles of a STP-T and is useful for selecting a proper order and determining the corresponding valid ranges of displacements. Finally, the STP-T method is tested for orbit propagation under three typical orbital dynamics: the unperturbed Keplerian dynamics, the J2 perturbed two-body dynamics, and the nonlinear relative dynamics. The numerical simulation results indicate that the STP-T supplies a good approximation of the final state within certain valid ranges of initial state and propagation time, the a priori estimated error is close to the exact error in sense of trend and magnitude, and the computational cost can be significantly saved by the weighted-order scheme without loss of accuracy.
       
  • A new gyroscopic principle. New gyroscopic effects on cold atoms and on de
           Broglie waves, different from the Sagnac effect
    • Abstract: Publication date: Available online 28 March 2019Source: Acta AstronauticaAuthor(s): Nikolay I. Krobka This article provides a brief overview of the state-of-the-art development of a new generation of gyros on cold atoms for space applications. The problem of narrowing the dynamic range of atomic interferometers in comparison with optical interferometers and method for resolving this problem are discussed. Three new results are presented for the first time in the world: 1) A new “kinematic” gyroscopic principle that allows one to determine uniquely the absolute angular velocity without limitations on the measurement range, in contrast to the interferometric gyroscopic principle; 2) Accurate expressions of gyroscopic effects on cold atoms and on de Broglie waves based on kinematic and interferometric gyroscopic principles, which are fundamentally different from the Sagnac effect; 3) The asymmetry of the particle-wave duality seen in gyroscopy: an increase in the sensitivity to rotation when stepping from photons to cold atoms is colossally greater than the increase in sensitivity when stepping from light waves to de Broglie waves of the order of (1013 ÷ 107) at atom temperature of the order of (10−9 ÷ 10−3) K.
       
  • Interaction between hypervelocity elongated projectile and screen
           protection of space vehicles
    • Abstract: Publication date: Available online 27 March 2019Source: Acta AstronauticaAuthor(s): B.V. Rumyantsev, I.V. Guk, A.I. Kozachuk, A.I. Mikhaylin, S.I. Pavlov, M.V. Silnikov In the article, we study the efficiency of screen protection of space vehicles against hypervelocity elongated projectiles that are an analog of the most dangerous space debris. We analyze the kinetics of an elongated projectile penetration into a target after the projectile passes through screen protection. Parameters of an elongated projectile impact with copper and aluminum screens and a state of a cavern surface formed as a result of projectile penetration into metal target have been found. Rapid unloading of the penetration zone, the emergence of pores in the volume of the projectile material before their destruction in a jet flow region can explain the increase of efficiency of screen protection when evaporating space junk.
       
  • Water quality monitoring during interplanetary space flights
    • Abstract: Publication date: Available online 26 March 2019Source: Acta AstronauticaAuthor(s): G.Yu. Grigoriev, A.S. Lagutin, Sh.Sh. Nabiev, B.K. Zuev, V.A. Filonenko, A.V. Legin, D.O. Kirsanov Advanced approaches to the development of analytical modules for water quality on-line monitoring during long-time orbital piloted missions are discussed. The first module is intended for an analysis of water ionic composition and its microbiological toxicity with individual selective sensors. The second module operating with the use of an oxythermographic method ensures recirculating water monitoring for the content of total carbon and specific hydrocarbons, e.g., ethanol. Both modules represent subsystems of an integrated analytical complex for an on-line control of air and water quality onboard spacecrafts.
       
  • Non-stationary process of accelerating the measuring probe in the
           laboratory ballistic module
    • Abstract: Publication date: Available online 21 March 2019Source: Acta AstronauticaAuthor(s): M. Yu Sotskiy, V.A. Veldanov, V.V. Selivanov A variant of the technology of dynamic contact sensing of rheological media, including a wired connection for connecting the measuring probe with the recorder, is presented. The results of a series of laboratory experiments with high-speed imaging of the process from the beginning of the movement of the measuring probe and the wire of electrical communication in the starting device to the end of the movement of the probe in the target medium are shown. The process of the impact of the detonation products of the working gas on the probe and on the elements of the measuring assembly is analyzed. Based on the analysis of the evolution of the shape of the electric wire, conditions were determined that ensure the reliability of recording the motion parameters of the measuring probe on the flight path and in the target.
       
  • HMGB1 mediated autophagy protects glioblastoma cells from carbon-ion beam
           irradiation injury
    • Abstract: Publication date: Available online 19 March 2019Source: Acta AstronauticaAuthor(s): Runhong Lei, Liben Yan, Yulin Deng, Jin Xu, Tuo Zhao, M. Umer Farooq Awan, Qiang Li, Guangming Zhou, Xiao Wang, Hong Ma The present study investigated autophagy changes and the expression of HMGB1 in human glioblastoma cells, responding to carbon-ion beam irradiation (35 keV/μm, 80.55 MeV/u). U251 cells were irradiated with carbon-ion beams and cell proliferation was measured by counting the number of living cells. The expression of Light Chain 3 beta (LC3B), Beclin 1, high-mobility-group box 1 (HMGB1), pro-form caspase-3 and Cellular FLICE-like inhibitory protein (c-FLIP) was analyzed by western blotting. Caspase enzyme activity was determined via a caspase cleavage based florescent substrate commercial Kit. Living cell counting demonstrated a time- and dose-dependent cell death in U251 cells. The expression of LC3B and Beclin 1 revealed that, a high level of autophagy was induced 24 h after irradiation with 1 Gy carbon ions and then decreased in a time- and dose-dependent manner. The expression of the whole HMGB1 showed a well correlation with the dynamic autophagic level. Cytoplasmic HMGB1 maintained autophagy was concluded. Enzyme-Linked Immuno Sorbent Assay (ELISA) measurement found that, HMGB1 was released into the extracellular space in a time- and dose-dependent manner. Lower intracellular HMGB1 levels correlated with decreased autophagy as measured by the expression of LC3B. Decreased expression of pro-form caspase-3 and c-FLIP as well as the increased caspase enzyme activity indicated that apoptosis was induced by carbon-ion beam irradiation. Inhibition of HMGB1 release from the area of intracellular to that of extracellular significantly increased cell survival. In summary, carbon-ion beam irradiation could elevate autophagy and HMGB1 expression efficiently, which would protect the cells from programmed cell death via inducing autophagy. Apoptosis as measured by expression of caspase activities increased as the dose increased, which was accompanied with decreased levels of LC3B and HMGB1.
       
  • Atmosphere composition control during long-duration space missions
    • Abstract: Publication date: Available online 16 March 2019Source: Acta AstronauticaAuthor(s): G.Yu. Grigoriev, A.S. Lagutin, Sh.Sh. Nabiev, A.A. Vasiliev, O.I. Orlov, L.N. Mukhamedieva, A.A. Pakhomova, A.V. Rodin, V.M. Semenov, D.B. Stavrovskii, M.G. Golubkov A concept and strategy of the monitoring of chemical composition of the atmosphere in manned spacecrafts applicable during long-term and interplanetary flights are considered. The suggested concept and strategy are applicable for the life support system in spacecraft, which includes a system of gas composition support, a water supply system, a system of sanitary and hygienic support, a food supply system and a thermal control system. Major risk factors related with changes of the atmosphere composition during interplanetary space missions are evaluated.An advanced design of the analytical complex is described for the control of air quality in manned spacecraft's taking into account these risk factors. The simultaneous use of several methods of gas analysis is proposed together with partial overlapping of the set of substances to be detected with regard to the substances of particular (critical) importance. Application of such gas control system will provide a tool for the analyzing of a wide range of substances and will ensure the analysis of the atmosphere even in case of the failure of some of its parts.
       
  • Geostationary station-keeping with electric propulsion in full and failure
           modes
    • Abstract: Publication date: Available online 14 March 2019Source: Acta AstronauticaAuthor(s): Lincheng Li, Jingrui Zhang, Yanyan Li, Shuge Zhao This paper focuses on geostationary satellites with an electric propulsion system and develops two efficient station-keeping strategies in full and failure modes. High-precision mean orbital elements are calculated by an estimator and used as the inputs of two control strategies. In the full mode, an optimization-based maneuver planner, which requires the computations of future orbits, is proposed to achieve long-term minimum-fuel station-keeping. In the failure mode, a fault detection algorithm is designed to diagnose the thruster failure and compute the orbital deviation caused by faulted thruster. Subsequently, a real-time control law as well as a threshold function is formulated to produce the on-off commands of electric thrusters, which correct the orbital deviation. Finally, numerical simulations are made to validate the accuracy and efficiency of two strategies.
       
  • High-frequency electromagnetic radiation affecting moving conductive
           screens
    • Abstract: Publication date: Available online 14 March 2019Source: Acta AstronauticaAuthor(s): M.N. Smirnova, V.V. Tyurenkova, S.N. Kosinov, V.F. Nikitin Protection of on board electronic devises subjected to high-frequency electromagnetic emission is a crucial problem of Space flight safety. The present paper contains the results of theoretical investigation of the effects of high frequency electromagnetic radiation on a moving conductive screen. Methods are developed and results are presented aimed at evaluating conductive screen protective properties depending on thermophysical and electromagnetic properties of material, radiation intensity and frequency, as well as relative velocity of the radiation source and the target.
       
  • Study on the damping capacity of a fluidic baffle under different
           injection conditions
    • Abstract: Publication date: Available online 13 March 2019Source: Acta AstronauticaAuthor(s): Wooseok Song, Jongkwon Lee, Jaye Koo Passive control methods have been widely used to decrease the intensity of combustion instability, and a structural baffle injector has been applied in liquid rocket-engine development. However, the development cost of a structural baffle injector increases because the thrust of a liquid rocket engine should increase as the weight increases. The objective of this paper is to analyze the damping capacity of a fluidic baffle injector using a dissimilar injector arrangement. In this study, a cold-flow test was conducted to observe the effect of using a fluidic baffle injector, and a pulse gun was adopted to generate the pressure wave. A gas-centered swirl coaxial injector and a shear coaxial injector were used to inject the bipropellant. Gaseous nitrogen and liquid water were used for the bipropellant. In addition, multi injectors and a pulse gun were used to compare the effects of a gas-centered swirl coaxial injector and a shear coaxial injector, each acting as the fluidic baffle, on the spray intensity under different conditions. When the gas-centered swirl coaxial injector was used as the fluidic baffle injector, the amplitude increase rate increased as the momentum flux ratio decreased. However, the shear coaxial injector obstructed the pressure-wave propagation. Therefore, the shear coaxial injector was a better fluidic baffle injector than the gas-centered swirl coaxial injector.
       
  • Dual-arm coordinated capturing of an unknown tumbling target based on
           efficient parameters estimation
    • Abstract: Publication date: Available online 12 March 2019Source: Acta AstronauticaAuthor(s): Jianqing Peng, Wenfu Xu, ErZhen Pan, Lei Yan, Bin Liang, Ai-guo Wu A malfunctioned satellite or other space debris is generally non-cooperative and tumbling, bringing great challenge to capture and remove it. In this paper, we propose a dual-arm coordinated capturing method based on efficient parameters estimation. Firstly, the dynamics model of a tumbling target is deduced in details. Its motion characteristics are then analyzed. Secondly, we design an efficient Hybrid Kalman Filter (HKF) by combining Extended Kalman Filter (EKF) with Unscented Kalman Filter (UKF). It effectively overcomes the shortcoming of low accuracy of EKF and long iteration time of UKF, and improves the speed and accuracy of the Kalman Filter iteration algorithm. Two movement cases of an uncontrolled target are considered: one is rotation around the principal axes of inertia; the other is rotation around arbitrary axes. Thirdly, the estimated motion and inertia parameters are used to plan the trajectories of a dual-arm space robot to capture the tumbling target. Finally, the simulation environment is created and the proposed method is verified. The simulation results show that the proposed HKF algorithm can estimate the attitude quaternion, angular velocity, and the inertia tensor (including Ixx, Iyy, Izz, Ixy, Ixz and Iyz) with higher accuracy (compared to EKF) and lower computation cost (compared to UKF); the planned trajectories of the dual-arm space robot are effectively for tumbling target capturing.Graphical abstractImage 1
       
  • Visibility optimization of satellite constellations using a hybrid method
    • Abstract: Publication date: Available online 12 March 2019Source: Acta AstronauticaAuthor(s): Chao Han, Shengzhou Bai, Sihang Zhang, Xinwei Wang, Xiaohui Wang For the visibility optimization problem of satellite constellations, this paper presents an efficient hybrid optimization method taking multiple constraints into account. To reduce the time needed for the optimization, the satellite constellation is assumed to have a specific configuration. The optimization includes two steps. The first step searches for optima over a large scale, while the second step is designed to obtain the accurate optimal solution based on the result of the first-step optimization. Based on the analysis of the coverage performance function, a linear adaptive population method is proposed for the first step. When compared with the traditional optimization method, calculation time can be efficiently reduced while ensuring an accurate optimization. Several numerical simulations are conducted for validation. It proves to be a practical choice for engineering applications.
       
  • Experimental study and numerical simulation of chemiluminescence emission
           during the self-ignition of hydrocarbon fuels
    • Abstract: Publication date: Available online 6 March 2019Source: Acta AstronauticaAuthor(s): A.M. Tereza, S.P. Medvedev, V.N. Smirnov The time evolution of the chemiluminescence emission signals of CH*, OH*, C2*, and CO2* during the self-ignition of a number of the simple hydrocarbons is studied. The experiments are performed behind reflected shock waves over a temperature range of 1100–1900 K at a pressure of ∼1 bar. The effects of fuel-to-oxidizer equivalence ratio and the structure of the hydrocarbon molecule on the time profiles of the signals for each of the emitters are examined. A detailed kinetic mechanism for describing the emission signals from CH*, OH*, C2*, and CO2* recorded during the self-ignition of hydrocarbons is developed. To make the simulations more rigorous and reliable, the NASA thermodynamic polynomials for C2*, and CO2* were calculated based on the respective rotational and vibrational parameters given in the literature. Numerical simulations satisfactorily reproduce the measured time profiles of the signals from the studied emitters.
       
  • Experimental investigation of the effect of nozzle throat diameter on the
           performance of a hybrid rocket motor with swirling injection of
           high-concentration hydrogen peroxide
    • Abstract: Publication date: November 2019Source: Acta Astronautica, Volume 164Author(s): S.S. Wei, M.C. Lee, Y.H. Chien, T.H. Chou, J.S. Wu One of the issues of using a normal graphite nozzle for the hybrid rocket propulsion is the serious throat erosion due to combustion with a higher O/F ratio. This may undermine the throttling capability of the hybrid rocket engine. In this study, we would like to address how the propulsion performance changes under the conditions of different nozzle throat diameters and O/F ratios. We designed and tested a 40-kgf class single-port hybrid rocket motor with the swirling injection of oxidizer, which utilizes the 90 wt% hydrogen peroxide and polypropylene (PP) as oxidizer and fuel, respectively. Three different diameters of graphite nozzle throat (10, 11, and 12 mm) were used to approximate various conditions of nozzle erosion, while the mass flow rates of the injected oxidizer were kept the same. The hot-fire test results indicated that the thrust was nearly the same even the nozzle throat diameters and O/F ratios were different. Especially, the discrepancies among the measured thrusts and oxidizer ISP under various test conditions were found to be less than 1%, which is highly beneficial for the purpose of the thrust control using mass flow rate control of the oxidizer for a hybrid rocket engine with swirling injection of high-concentration hydrogen peroxide.
       
  • Mars Science Laboratory Alpha Particle X-ray Spectrometer Trace Elements:
           Situational Sensitivity to Co, Ni, Cu, Zn, Ga, Ge, and Br
    • Abstract: Publication date: Available online 31 August 2019Source: Acta AstronauticaAuthor(s): S.J. VanBommel, R. Gellert, J.A. Berger, A.S. Yen, N.I. Boyd Alongside major and minor elements, trace elements in Martian samples quantified through geochemical analyses by the Mars Science Laboratory (MSL, Curiosity) Alpha Particle X-ray Spectrometer (APXS) provide insight into ancient environments on Mars. APXS spectrum simulations facilitated the characterization of trace elements measured by the APXS under experimental situations commonly encountered on Mars. The precise quantification limits (PQL) obtained under ideal conditions are consistent with limits of detection in the literature and increase with degrading spectral quality. Major trace element species, such nickel, zinc, and bromine, with typical concentrations in the 100s of μg/g (or less), are quantifiable even with short (e.g., 20 minute) early morning measurements between drives given the typical concentrations at the MSL site, Gale Crater. Target compositions currently in the public domain with major trace element species below the derived PQL specific to each measurement are noted.Quantification of copper, gallium, and germanium at 30 ppm and
       
  • Investigations on quantitative measurement of heat release rate using
           chemiluminescence in premixed methane-air flames
    • Abstract: Publication date: November 2019Source: Acta Astronautica, Volume 164Author(s): Yue Hu, Jianguo Tan, Liang Lv, Xiangdong Li Numerical and experimental studies on 1-D, steady premixed methane-air flames were performed to investigate the quantitative measurement of heat release rate (HRR) using chemiluminescence. A detailed reaction mechanism, incorporating sub-reaction models for excited state radicals (CH* and OH*) was employed in the numerical study. The numerical work utilized the CHEMKIN-PRO package to investigate the distribution rule of excited state radicals and HRR. The heat release characteristic of elementary reactions and the relationship between net reaction rate and HRR were analyzed as well. According to the result of numerical study, experimental work was conducted to measure the HRR and chemiluminescence of OH* and CH* in the flat flames. The distributions of HRR and chemiluminescent intensity were measured by high-accuracy coated Pt/13%-Rh-Pt thermocouple and ICCD camera, respectively. The results shows that OH* and CH* are located in the narrow area where severe chemical reactions occur with much heat release. Compared to CH*, OH* is more effective in marking the spatial distribution of HRR and the correlation between chemiluminescent intensity and HRR possesses characteristic of linearity. Thus, the HRR quantitative measurement method using chemiluminescence has been acquired.
       
  • Heat reduction mechanism of hypersonic spiked blunt body with installation
           angle at large angle of attack
    • Abstract: Publication date: November 2019Source: Acta Astronautica, Volume 164Author(s): Jie Huang, Wei-Xing Yao, Ning Qin The spiked blunt body is usually adopted to reduce the aerodynamic heating of hypersonic vehicles. In this paper, the heat reduction mechanism of hypersonic spiked blunt body with installation angle at large angle of attack is studied by the CFD numerical method. The AUSM+ scheme and Menter's SST k-ω turbulent model are adopted for the spatial discretization and turbulent simulation respectively. The results show that the maximum wall heat flux of blunt body is sensitive to the angle of attack. The increase of angle of attack causes the aerodynamic heating to rise sharply. The installation angle of the spike can effectively reduce the maximum heat flux of blunt body at large angle of attack, which is very beneficial to the thermal protection of blunt body. There is an optimal installation angle to minimize the maximum heat flux of blunt body. The optimal installation angle is about 1.5° greater than the angle of attack. All the investigations in this paper show the feasibility and advantages of spiked blunt body with installation angle in the engineering applications.
       
  • The effect of a magnetic field at a nozzle on the performance of a
           microwave discharge cathode
    • Abstract: Publication date: Available online 30 August 2019Source: Acta AstronauticaAuthor(s): Takato Morishita, Ryudo Tsukizaki, Shunya Morita, Daiki Koda, Kazutaka Nishiyama, Hitoshi Kuninaka The microwave cathode was developed as a neutralizer for the microwave ion thrusters of the Japanese asteroid explorers Hayabusa and Hayabusa2. Since it emits hundreds of mA of electron current, ion currents collect at the wall of the cathode, which causes fatal destruction due to sputtering. In an effort to reduce the sputtering voltage, this study investigates the effect of the strength of the magnetic field at the nozzle on the anode voltage. Firstly, a magnetic field is applied at the nozzle by a coil. Using the coil, decreasing the magnetic field intensity increases the electron density at the exit of the nozzle. It is presumed that the applied magnetic field facilitates the detachment of magnetic lines by the electrons inside the microwave cathode, resulting in a reduction of the anode voltage. By weakening the nozzle magnetic field, trapped electrons are reduced and the transportability to the outside is improved. Secondly, to realize the same magnetic field intensity achieved in the first experiment without any additional power consumption, the author proposes the use of a magnetic shield. The magnetic shield reduces the anode voltage from 37 V to 32 V at 180 mA, the nominal current of the flight model. Since the sputtering rate exponentially increases with the anode voltage, reducing the anode voltage through these techniques is effective in increasing the lifetime of the cathode.
       
  • Experiments on dust removal performance of a novel PLZT driven lunar dust
           mitigation technique
    • Abstract: Publication date: Available online 30 August 2019Source: Acta AstronauticaAuthor(s): Jing Jiang, Yifan Lu, Hongyue Zhao, Lei Wang Lunar dust removal has proved to be one of the most important issues to be solved in lunar exploration. A novel lunar dust removal technique based on the anomalous photovoltaic effect of lanthanum-modified lead zirconate titanate (PLZT) has been developed in our previous research which could be used for conductor surface dust mitigation. In this study, the working performance of this novel dust removal technique is investigated. Since the particle size of the dust has a strong influence on the lunar dust removal performance, the particle size range which is applicable for this technique is explored first. Then the relation between the dust particle size and charge is discussed theoretically and experimentally. An experimental platform is built up for testing the working performance of this technique and the results indicate that a 95% dust removal efficiency can be achieved on a 320mm×125mm dust covered surface, which is very promising for future lunar dust mitigation.
       
  • Fast-swirl space non-cooperative target spin state measurements based on a
           monocular camera
    • Abstract: Publication date: Available online 28 August 2019Source: Acta AstronauticaAuthor(s): Gu Yingying, Wang Li Measuring the motion state of space non-cooperative targets is in the fields of space on-orbit services and debris removal. This paper proposes a method for the measurements of the spin rate of fast-swirl non-cooperative targets through a monocular camera, for image features that have been degraded at a medium and long distance. First, the coordinate system between the tracking satellite and the target is established, and the relationship between the target spin period and its image projection angle is deduced. An image processing method which can extract the projection angle of the target image stably under complex illumination conditions is then proposed. Next, considering the characteristics of the sequence projection angle of the fast-spinning target at a long distance, the spin rate of the target is calculated using a sinusoidal polynomial fitting method. The proposed method is validated by simulated and on-orbit data. Experiment results show that the method has strong adaptability, measurement reliability and practical engineering application prospects.
       
  • Glide Trajectory Optimization for Hypersonic Vehicles via Dynamic Pressure
           Control
    • Abstract: Publication date: Available online 27 August 2019Source: Acta AstronauticaAuthor(s): Hongyu Zhou, Xiaogang Wang, Naigang Cui This paper researches the optimal glide trajectory for hypersonic vehicles, which is extremely challenging because of the strong nonlinearity of the optimization problem. Compared to conventional methods that refer to complicated optimization algorithms, a novel optimization model is developed based on a dynamic pressure profile. By analyzing the effect of the dynamic pressure on aerodynamics and flight states, path constraints are incorporated into the profile and the terminal constraints are integrated into the restriction on the terminal altitude. Therefore, no path constraints, and only one terminal constraint, exist in the optimization model. In addition, the angle-of attack (AOA) and the bank angle can be directly derived from the profile, so the mapping between the trajectory commands and the performance index is avoided. Finally, the original problem is converted to a parameter optimization problem, which is less complex and easier to solve. The trajectory is optimized by an improved particle swarm optimization (PSO) method, in which the constraint is addressed by a comparison mechanism and the search is facilitated by a mutation mechanism. Numerical simulation indicates the effectiveness of the proposed method via various scenarios and by comparison with other methods.
       
  • Assessment on Density Discrepancy of Supercritical Reactive Hydrocarbon
           Fuels Using the Monte-Carlo Method
    • Abstract: Publication date: Available online 26 August 2019Source: Acta AstronauticaAuthor(s): Xuanfei Yu, Silong Zhang, Wen Bao, Weixing Zhou, Daren Yu In order to assist the developing of mass flow rate measurement methods for supercritical reactive hydrocarbon fuels, the possible variation of fuel density caused by thermal cracking is evaluated. A one-dimensional model of the flow process inside scramjet cooling channels is developed and validated through experiment for the assessment, with the Monte-Carlo method adopted to define the test conditions. The results indicate that pyrolysis of the fuel is very sensitive to the distribution of heat flux (HFD). For the case of total heating power of 12.5kW, the relative discrepancies of 88% and 7.2% are observed for channel outlet fuel mass conversion and density respectively due to the variation of HFD, with the corresponding outlet temperature is varied between 890∼950K accordingly. Also it reveals that within the entire chemical non-equilibrium region, the maximum difference of fuel mass conversion can be as high as 60% for equal channel outlet fuel temperature, with the maximum relative discrepancy for fuel density is up to 140% approximately. Meanwhile, it seems that the density discrepancy cannot be decreased to the acceptable level by selecting the design and operation parameters of the cooling channel, i.e., within the interval of fuel pressure, mass flow flux and tube length evaluated, the maximum relative discrepancy of channel outlet fuel density varies between 112.1∼150%, which is far beyond the proposed maximum acceptable value in term of mass flow measurement.
       
  • A mathematical model for the separation behavior of a split type low-shock
           separation bolt
    • Abstract: Publication date: Available online 26 August 2019Source: Acta AstronauticaAuthor(s): Dae-Hyun Hwang, Jae-Hung Han, Juho Lee, YeungJo Lee, Dongjin Kim Pressure cartridge type separation devices which are widely used in fairing, stage separations of space launch systems, and many other aerospace fields generate much lower pyroshock and produce no high-speed debris compared to frangible explosive separation devices. However, because the operation is completed in a few milliseconds and the releasing mechanism is complicated, their separation behavior is difficult to experimentally identify. This paper presents a mathematical model to simulate the separation behaviors for a split-type separation bolt, one of the pressure cartridge type separation devices. The mathematical model includes a combustion model, buckling resisting model, split behavior model related to static and dynamic friction, O-ring friction model, contact force model, and slip angle model. Each composing models are obtained by mathematical formulation or numerical analysis. An efficient contact model is constructed by using virtual penetration model appropriately for complex contact phenomenon. To validate the established model, separation experiments were performed; the results are then compared with the mathematical model. Present study show that complex mechanical behaviors coupled with combustion of solid propellant charge can be efficiently simulated by the mathematical model.
       
  • Experimental and numerical investigation on initial flame kernel blow-out
           in a supersonic combustor with a rear-wall-expansion cavity flameholder
    • Abstract: Publication date: Available online 26 August 2019Source: Acta AstronauticaAuthor(s): Taiyu Wang, Yixin Yang, Zhenguo Wang, Zun Cai, Mingbo Sun, Guangxin Li The initial flame kernel blow-out process in an ethylene fueled scramjet combustor with a rear-wall-expansion cavity was investigated experimentally and numerically. In the experiment, it was observed that the initial flame kernel was blew off quickly after ignition under 5 different global equivalence ratios. A high precision numerical method was then adopted and the method was validated by comparing numerical results with available experimental data. It is found that the physical process from ignition to flame complete blow-out is well simulated by the numerical solver. Based on the numerical results, the blow-out process is divided into 6 stages and the characteristics of each stage are concluded. It is analyzed that the combined effect of the cavity recirculation zone and the cavity shear layer as well as the upper mainflow reduces the retention time of the initial flame kernel before it can develop to a steady flame base, which is the reason for the unsuccessful ignition in the rear-wall-expansion cavity.
       
  • Effects of Pintle Injector on Ethylene-air Rocket-based Continuous
           Rotating Detonation
    • Abstract: Publication date: Available online 26 August 2019Source: Acta AstronauticaAuthor(s): Si-yuan Huang, Jin Zhou, Shi-jie Liu, Hao-yang Peng Continuous Rotating Detonation (CRD) shares many similarities with the High-Frequency Tangential Instability (HFTI) in liquid rocket engine, and it may be one cause of the HFTI. To investigate the self-sustaining mechanism of CRD/HFTI, a pintle-like injection scheme is adopted in this paper, and series of ethylene-air tests have been conducted. The pintle injector effects on the CRD operation range have been analyzed firstly. By decreasing the diameter of pintle injector, the lean equivalence ratio boundary increases, and the primary combustion mode transfers from CRD to sawtooth-wave mode. By increasing the insertion length, the enlarging of the head recirculation zone is helpful for the realization of multi-CRD waves. Based on the high-frequency pressure results, the propagation characteristics of single-wave, two-waves and sawtooth-wave modes are detailed. Theoretical intrinsic frequencies of the hollow chamber have been calculated and compared with the test results. The single-wave and two-waves modes show good agreements with the first tangential and second tangential theoretical results, respectively, with the relative deviations within just 6%. But the frequency of sawtooth-wave mode is much less than the first tangential theoretical value, and the deviation reaches about 20%. Because the diameter of traditional rocket pintle injector is much smaller than that of combustor, CRD cannot be achieved due to the propellant deficiency around the outer combustor, leading to the depress of HFTI. This paper could improve the understanding of the self-sustaining mechanisms of CRD and HFTI.
       
  • Jet transport-based nonlinear state and parameter estimation for
           geostationary spacecraft
    • Abstract: Publication date: Available online 24 August 2019Source: Acta AstronauticaAuthor(s): Jianlin Chen, Josep J. Masdemont, Gerard Gómez, Jianping Yuan Based on the jet transport technique, this paper proposes a novel nonlinear Kalman filter for simultaneously estimating the spacecraft state vector and uncertain parameters, either physically related with the spacecraft or with the measurement procedure. Two different coordinate representations, including Cartesian and hybrid geostationary orbital elements, are exploited in the new nonlinear estimators. The performance and sensitivity analyses of the proposed jet transport-based nonlinear estimators are assessed by numerical simulations and compared with the classical extended Kalman filter.
       
  • Modeling and Collision Avoidance Control for the Disturbance-Free Payload
           Spacecraft
    • Abstract: Publication date: Available online 24 August 2019Source: Acta AstronauticaAuthor(s): Hongjie Yang, Lei Liu, Hai Yun, Xinguo Li The Disturbance-Free Payload(DFP) spacecraft, which includes the payload module(PM) and the support module(SM) connecting through voice coil motors(VCM), can provide unprecedented control and motion stability for the sensitive payload. The payload module and the support module have a high collision probability because of close proximity formation. In order to perform collision avoidance control on two modules, this paper establishes the dynamics model of the DFP spacecraft and proposes a collision avoidance control strategy based on the model predictive control(MPC). The established model synthesizes the back-Electromotive-Force(back-EMF) of the VCM and the stiffness and damping of the flexible cables. The MPC controller converts the collision avoidance problem into a quadratic programming problem. The control forces are obtained by solving the quadratic programming problem. The collision avoidance control of the DFP spacecraft has performed while the payload module subjects to sudden disturbance. The simulation results verify the effectiveness of the proposed control strategy and show that the proposed MPC controller exhibits better collision avoidance capability than that of the PD controller.
       
  • Contribution Analysis of Inter-satellite Ranging Observation to BDS-2
           Satellite Orbit Determination Based on Regional Tracking Stations
    • Abstract: Publication date: Available online 24 August 2019Source: Acta AstronauticaAuthor(s): Zhang Rui, Tu Rui, Fan Lihong, Zhang Pengfei, Liu Jinhai, Han Junqiang, Lu Xiaochun In order to analyse the contribution of inter-satellite ranging observation to the BeiDou regional navigation satellite system (BDS-2) satellite orbit determination under the condition of regional ground tracking stations, first, the methods of using the observation model, the dynamic parameters dilution of precision (DPDOP), and the satellite position dilution of precision (SPDOP) to describe the contribution of inter-satellite ranging observation to orbit determination accuracy are proposed. Then, based on the measured observation data of the regional ground tracking stations located in China, as well as simulated inter-satellite ranging observation data, the contribution of inter-satellite ranging observation to orbit determination accuracy for the three types of satellites used by BDS-2 is analysed. The results show that the inter-satellite ranging observation improves the solution strength of the dynamic parameters by adding redundant observations without adding new parameters to be estimated, which effectively improves the orbit determination accuracy of the along-track component of Geostationary Earth Orbit (GEO) satellite and the cross-track and radial components of Inclined Geosynchronous Orbit (IGSO) and Medium Earth Orbit (MEO) satellites. In addition, under the condition of the regional tracking stations, the inter-satellite ranging observation compensates for the disadvantage that the satellite cannot be tracked by the whole arc segment. The accuracy and continuous stability of the orbit determination solution and the geometry structure of satellites that can be observed by stations and other satellites are significant improved, for which the average DPDOP values of GEO, IGSO, and MEO satellites are improved 50.2%, 73.0%, and 72.1%, respectively.
       
  • Mindfulness and relaxation training for long duration spaceflight:
           evidences from analog environments and military settings
    • Abstract: Publication date: Available online 23 August 2019Source: Acta AstronauticaAuthor(s): Pagnini Francesco, Phillips Deborah, Bercovitz Katherine, Langer Ellen As space missions move from low-earth orbit operations to long duration exploration, the mission’s crews will face a different set of experiences and stressors. In order to help prevent the development of cognitive or behavioral symptoms during these missions it is important to define preventative countermeasures. Recent evidence points to mindfulness and relaxation techniques as promising countermeasures for promoting cognitive and behavioral health.We conducted a narrative review of the scientific literature to identify key factors relevant to the role of mindfulness and relaxation techniques in the military and other analog settings, which share some important similarities with the space exploration context. Our results indicate that cognitive (non-meditative) mindfulness is an important psychological construct that can help to promote resilience and to reduce stress in analog environments and particularly in the military. While the literature suggests that mindfulness can be promoted through focused interventions, most of the studied interventions to date are based on meditation. While efficacious, meditation-based interventions generally require a significant amount of time for training. Alternative mindfulness approaches have not yet been explored in these settings but have yielded potentially relevant results for space. Relaxation training is a helpful tool to manage stress and to reduce anxiety. In the military, relaxation techniques are sometimes integrated into psychological training before deployment, leading to improved performance and reduced negative emotions.Even with a lack of specific literature about the application of these concepts in space, literature that describes the experiences from analog environments and military contexts as well as other studies on challenging conditions, suggest further exploration of interventions in these areas.
       
  • Corrigendum to “Integrated guidance for Mars entry and powered descent
           using reinforcement learning and pseudospectral method” [Acta Astronaut.
           (2019) in press doi: 10.1016/j.actaastro.2018.12.033]”
    • Abstract: Publication date: Available online 23 August 2019Source: Acta AstronauticaAuthor(s): Xiuqiang Jiang, Shuang Li, Roberto Furfaro
       
  • Out-of-plane Relative Control of an Ion Beam Shepherd Satellite Using Yaw
           Attitude Deviations
    • Abstract: Publication date: Available online 22 August 2019Source: Acta AstronauticaAuthor(s): S. Khoroshylov According to the concept of active debris removal, named "ion beam shepherd", a shepherd satellite must be controlled to move at a certain small distance in front of a space debris object during the de-orbiting phase. Due to the considerable duration of this phase, the propellant consumption is a key driver for the control system design. As shown in recent studies, the in-plane relative motion of such a formation can be controlled using a thrust variation of only one compensation thruster of the shepherd. This control strategy allows designers to significantly reduce the propellant mass needed to fulfill a de-orbiting mission but does not ensure the controllability of the formation in the out-of-plane direction. To fill this gap this paper proposes to deviate the yaw attitude of the shepherd for applying control actions in the out-of-plane direction. The laws of the yaw angle variation are designed to effectively damp out the out-of-plane oscillations. Computer simulations demonstrate that a required relative spatial position of the formation can be maintained by varying only two values: the yaw angle of the shepherd and thrust of the compensation thruster. The analysis shows that the de-orbiting rate deteriorates insignificantly due to the attitude deviation of the ion beam.
       
  • Survivability of Carbon Nanotubes in Space
    • Abstract: Publication date: Available online 22 August 2019Source: Acta AstronauticaAuthor(s): Yoji Ishikawa, Yasuhiro Fuchita, Takashi Hitomi, Yoku Inoue, Motoyuki Karita, Kohei Hayashi, Takayuki Nakano, Naoko Baba Carbon nanotube (CNT) yarns were exposed to the space environment on the international space station (ISS) at low Earth orbit (LEO) of around 400 km altitude. Ground-based comparison tests, including irradiation of atomic oxygen (AO), electron beam (EB) and ultraviolet (UV) individually for different sets of samples, were performed. Significant deterioration of the outer surface and substantial reduction in tensile strength were found for AO irradiated CNT yarns among the ground-based comparison tests. Transmission electron microscopic observation revealed that crystal structure of CNT was physically damaged showing sharp graphene edges. As to the space exposure tests, quite similar damages and decrease in tensile strength were observed on the CNT yarns. We found that high kinetic energy impacts of the AO at LEO cause severe damages on carbon crystal materials.
       
  • Fine structures of self-sustaining dual jets in supersonic crossflow
    • Abstract: Publication date: Available online 22 August 2019Source: Acta AstronauticaAuthor(s): Qiang Liu, Zhenbing Luo, Xiong Deng, Dengpan Wang, Lin Wang, Yan Zhou, Pan Cheng The interaction between self-sustaining dual jets and supersonic laminar boundary layer is experimentally studied using the nanoparticle-based planar laser scattering in a Ma 2.95 supersonic low-turbulence wind tunnel for the first time. The typical fine flow structures, such as separation shock, “W” bow shock, barrel shock, horseshoe vortex, large-scale vortex structures and counter-rotating vortex pairs, are clearly identified by streamwise and spanwise flowfield images. The curves of jet penetration depth are fitted at the momentum ratio of 0.55 between self-sustaining dual jets and supersonic crossflow. The results play a significant role in further and comprehensive exploration of the active flow control for a supersonic flow.
       
  • Analyzing “Integral Indices” to quantify the effects of a perturbing
           force over satellites
    • Abstract: Publication date: Available online 22 August 2019Source: Acta AstronauticaAuthor(s): A.K. de Almeida, A.F. Bertachini de Almeida Prado, R. Vilhena de Moraes, M. Lara Integral indices are useful tools to be used to identify characteristics of an orbit. Using analytical solutions for a perturbative version of the Tsien problem (radial low thrust applieed to a spacecraft), two indices are defined and evaluated. They can make a map of the orbits disturbed by the thrust.
       
  • Improved Representation of Destructive Spacecraft Re-entry from Analysis
           of High Enthalpy Wind Tunnel Tests of Spacecraft and Equipment
    • Abstract: Publication date: Available online 21 August 2019Source: Acta AstronauticaAuthor(s): James C. Beck, Ian Holbrough, Thorn Schleutker, Ali Guelhan The assessment of casualty risk in destructive re-entry has historically been performed purely by simulation using heating correlations, which only have verification on basic shapes, and estimated phenomenology for fragmentation. As the application of space debris mitigation requirements is expected to result in a higher number of re-entries, this has brought a stricter enforcement of the casualty risk guidelines to proposed missions. In turn, this has increased the interest in designing spacecraft to demise in re-entry in order to allow uncontrolled re-entries to be performed. Initial testing of spacecraft materials and basic structures has demonstrated that the destructive re-entry tools do not capture the correct physics to be able to assist design in a meaningful way, and therefore, some means to improve the representativeness of the tools is required. The current understanding of the phenomenology of the fragmentation and demise processes is limited. As a consequence, it is vital to perform appropriate tests in order to improve the capability of the tools to assist the design process. To this end, a set of destructive tests on spacecraft materials, structures and components has been performed in an arc-heated supersonic wind tunnel. These tests include the first destructive wind tunnel tests ever performed on a complete nano-satellite and a reaction wheel. From these tests, it has been determined that the failure of aluminium structures is highly dependent upon the behaviour of the protective metal oxide layer, and that this can be catastrophic in nature. The tests on the nano-satellite have shown that the structure can be supported by stainless steel spacers between the electronics cards, and that glass fibre reinforced plastic PCBs are more resistant to melting than had been anticipated. The reaction wheel test has shown that the connections between parts are critical to the fragmentation and demise processes, as the glued housing separates quickly, well before melt temperature is reached at the joint. It has also demonstrated the importance of radiative cooling, as the flywheel and ball-bearing unit have survived a test at over 800kW/m2 with little damage.
       
  • Optimal Design and Robust Analysis of a Net of Active Devices for
           Micro-vibration Control of an On-orbit Large Space Antenna
    • Abstract: Publication date: Available online 20 August 2019Source: Acta AstronauticaAuthor(s): Federica Angeletti, Paolo Gasbarri, Marco Sabatini Large deployable antennas are required for the advancement of space communications, Earth observation, radio astronomy and deep space exploration. Most contemporary space antennas have exceeded the size of launching vehicles, leading to the necessity of stowed concepts to overcome the limitation. Many structural models have been investigated by different organizations. Generally, mesh deployable reflectors are currently more mature compared to other foldable solutions and will be the topic of this paper. Orbital disturbances, perturbations originated by on-board sources and thermal deformations affecting the deployed configuration can deteriorate the accuracy of the communications system. Undesired dynamic behaviour of structural components has to be predicted and counteracted. Therefore, vibration control is a key technology to correct the distortions altering the proper functioning of the system. An intelligent active structure is introduced as a structure configured with distributed actuators and sensors and guided by a controller to modify the dynamic response of the system. In this paper, the supporting structure of a very large mesh reflector is described. A FEM formulation is adopted to assemble the frame and it is validated by comparing it with commercial codes. According to the adopted model, the active elements can be embedded in the middle of the truss elements. Of course, active control of all the devices at the same time requires a control effort which could be not affordable in space applications. However, the effectiveness is not the same for all the actuators. In this study, two cascade optimization procedure are performed to assess the best positioning and velocity feedback gains of the actuators that must be controlled to damp vibrations. In particular, a gradient-based technique is used after both a Genetic Algorithm and a Reinforcement Learning methodology to find the best set of gains for the controller. The objective function is set as a weighted sum of power consumption of the actuators. As a study case, the spacecraft implements a velocity feedback strategy when performing a generic attitude manoeuvre to coordinate the simultaneous action of the devices to ensure the damping performance of the system is enhanced. In addition, the impact of damaged actuators and uncertainties on the mechanical properties of the passive structure has been discussed and analysed.
       
  • Influence of Lobe Geometry on Mixing and Heat Release Characteristics of
           Solid Fuel Rocket Scramjet Combustor
    • Abstract: Publication date: Available online 20 August 2019Source: Acta AstronauticaAuthor(s): Gao Yonggang, Liu Yang, Chai Zexin, Li Xiaocong, Hu Chunbo, Yu Xiaojing The highly efficient and organized combustion of combustors should be achieved to improve the performance of solid fuel rocket scramjets. This study investigated the influence of changes in lobe sweep angle and height on the mixing and heat release characteristics of a solid fuel scramjet combustor on the basis of a staggered support plate structure introduced in a previous experimental study. The goal was to determine the optimal parameters of lobe sweep angle and height for subsequent engine design. Numerical simulation was conducted to quantitatively analyze the mixing and heat release characteristics of the combustor at different lobe sweep angles and heights in terms of combustion efficiency, gas mixing degree, and oxygen–fuel ratio. Results demonstrate that 1) the lobe sweep angle should be based on the width and straight section length of the staggered support plate structure. Engine performance improves with the decrease of the lobe sweep angle. 2) There is an optimum lobe height in the range of 0–24 mm, and the optimum value point is approximately 14 mm according to the proposed engine configuration.
       
  • Effect of blockage ratio on the existence of multiple waves in rotating
           detonation engine
    • Abstract: Publication date: Available online 20 August 2019Source: Acta AstronauticaAuthor(s): Gaoyang Ge, Li Deng, Hu Ma, Xiao Liu, Le Jin, Changsheng Zhou The effect of blockage ratio on the existence of multiple waves in rotating detonation engine was investigated through experimental approach. It has been shown experimentally that four typical detonation propagation modes (single wave, hybrid mode of single wave and double waves, double waves, longitudinal pulsed detonation) were obtained by varying blockage ratios and air mass flow rates at the global equivalence ratio of around 1.60. The results show that the increase of blockage ratio reduces the critical mass flow rate for the occurrence of multiple waves. The occurrence of multiple waves experiences coexistence of single wave and two co-rotating detonation waves, and steady two co-rotating detonation waves. The increase of blockage ratio intensifies the effect of reflected oblique shock waves on fresh reactants and elevates average pressure in the combustor, which play important role in the occurrence of multiple waves. Moreover, the increase of blockage ratio elevates the pre-combustion pressure. The high pre-combustion pressure resulting from high blockage ratio leads to the existence of volumetric explosion immediately after ignition, which extends the formation time of rotating detonation wave. Further increasing of blockage ratio triggers the longitudinal pulsed detonation (LPD), and the highly decreased injection pressure ratio is considered to be the main reason for the occurrence of LPD.
       
  • Debris Removal in GEO by Heavy Orbital Collector
    • Abstract: Publication date: Available online 20 August 2019Source: Acta AstronauticaAuthor(s): Vladimir S. Aslanov A new way to removal small space debris using a heavy collector in GEO is considered. The proposed scenario involves three types of consecutive maneuvers: capturing of debris into an area bounded by Hill sphere of the heavy collector, towing and discharging debris in a graveyard orbit. The plane motion equations of the debris relative to the collector are written in the Local-Vertical-Local-Horizontal frame taking into account the engine thrust of the collector. Also considering the engine thrust, the equation motion of the collector in oscillating elements is written. The interaction of the debris and the collector is described by means of the inelastic impact theory. The values of the thrust force of the collector are determined, at which the debris can be captured and towed or discharged in the graveyard orbit. It has been shown numerical simulation, that the proposed maneuvers can be implemented.
       
  • Influence of the vortex generator on the performance of solid rocket
           scramjet combustor
    • Abstract: Publication date: Available online 20 August 2019Source: Acta AstronauticaAuthor(s): Chaolong Li, Xiang Zhao, Zhixun Xia, Likun Ma, Binbin Chen In this paper, the influence of vortex generator on the performance of solid scramjet was investigated by means of direct-connected fire tests. The experiments simulated a flight Mach number 5.5 at 23km. Hydrocarbon fuel was used as the fuel-rich solid propellant. The experimental results show that compared with the benchmark configuration, where no vortex generator was employed, the configurations with vortex generator can promote significantly the ignition and stable combustion of the primary fuel-rich mixture produced in the gas generator. The combustion efficiency of the test no.3 (with a strut) in the supersonic combustor reaches 0.60, while it is only 0.11 in the benchmark test. The vortex generators (ramp or strut) can promote the ignition of the primary fuel-rich mixture and therefore decrease significantly the ignition delay time in the supersonic combustor. And the ignition delay time in the test no.3 (a strut) is shorter than that of in test no.2 (a ramp). In summary, the vortex generators in these experiments play an important role in ignition, and flame stabilization of the fuel-rich mixture in the supersonic combustor of the solid rocket scramjet.
       
  • The Utility of Hyperbaric Oxygen Therapy for Human Spaceflight –
           Past, Present, and Future
    • Abstract: Publication date: Available online 20 August 2019Source: Acta AstronauticaAuthor(s): Amit Padaki, Ashrithpal Police Reddy, Kris Lehnhardt In order for astronauts to live and work in outer space, environmental conditions must be maintained within very strict parameters. Any change in these conditions (such as atmospheric composition, pressure, and/or temperature) could pose a risk to the astronauts and ultimately to the success of the mission itself. In particular, changes in pressure could place the astronaut at risk for decompression illness (DCI), a potentially life-threatening condition related to the presence of nitrogen bubbles within the body. There are a number of strategies in human spaceflight designed to minimize the risk of DCI or treat it if necessary. However, as humans prepare again to travel beyond Low Earth Orbit (LEO), the risk of developing DCI may increase, as would the difficulties in treating it, given that evacuation to Earth will become substantially less feasible. Even though hyperbaric oxygen therapy (HBOT) is the accepted gold standard for the treatment of DCI on Earth, there is currently limited capacity for this treatment option in space. Expanding HBOT capacity in human spaceflight could prove useful, given that this medical capability can also be used for the treatment of a number of other potentially life-threatening conditions, such as carbon monoxide poisoning, thermal burns, and gangrene. This paper will examine the current issues related to HBOT in space and discuss the opportunities for its use in future human spaceflight endeavors.
       
  • Interaction between Rotating Detonation Wave Propagation and Reactant
           Mixing
    • Abstract: Publication date: Available online 20 August 2019Source: Acta AstronauticaAuthor(s): Jian Sun, Jin Zhou, Shijie Liu, Zhiyong Lin Rotating detonation engines (RDEs) are widely studied because of their compact configurations and high thermal cycle efficiency. In previous literatures, many investigations on the mixing process in an RDE and the rotating detonation wave (RDW) propagation under non-premixed conditions have been published. However, the two issues were investigated separately, and the interaction between the RDW propagation and reactant mixing has not been studied yet. In this paper, a series of three-dimensional numerical simulations of the mixing process and the RDW propagation in an RDE are performed. The transient explicit density-based solver in ANSYS Fluent is used to perform the simulations. In the cold mixing flowfield, as the back pressure at the chamber exit increases, the axial velocity decreases, and the average resident time of reactant in the chamber increases. Thus the fuel has more time to mix with air in the chamber to provide a better mixing quality. The RDW velocity is very stable during the operation time, whose average value is about 1895 m/s. The velocity deficit is very small. After RDW initiation, the pressure in the combustion chamber increases due to the detonation process. The increased pressure slows down the flowing of the reactant, thus the average resident time of reactant within the height of the RDW increases, making the mixing quality better. The enhanced mixing quality of reactant in turn makes the RDW stronger. Thus, there is a positive feedback between RDW propagation and the reactant mixing.
       
  • Trajectory Planning of Dual-Arm Space Robots for Target Capturing and Base
           Manoeuvring
    • Abstract: Publication date: Available online 20 August 2019Source: Acta AstronauticaAuthor(s): Shuji Yang, Hao Wen, Dongping Jin This paper presents a trajectory planning method for a dual-arm space robot that is free-floating and receives no actuation from the base spacecraft. The task is to capture a target by a mission arm and accomplish base manoeuvring with the coupling effects by a manoeuvring arm. Three manoeuvring cases for the base are discussed concerning attitude regulation, attitude tracking and position tracking. In all cases, an optimization method is applied to solve for the joint velocity of the arms, which ensures that the joint states of the mission arm obtain the desired states for capturing and control the motion of the base. Moreover, the collision avoidance of the manoeuvring arm with the base and mission arm is considered an inequality constraint. In particular, the joint velocity of the mission arm is represented by a new variable to remove the disturbance caused by the mission arm on the attitude of the base which makes it easier to complete the attitude manoeuvring case. Finally, numerical simulations are carried out by the planar and spatial dual-arm robots to validate the efficiency of the control strategy during both capturing and base manoeuvring.
       
  • Iterative trajectory learning for highly accurate optical satellite
           tracking systems
    • Abstract: Publication date: Available online 17 July 2019Source: Acta AstronauticaAuthor(s): Thomas Riel, Andreas Sinn, Christian Schwaer, Martin Ploner, Georg Schitter This paper investigates the tracking accuracy of an optical telescope system used for satellite tracking and laser ranging applications. The investigated system uses a high precision motion controller and a pointing model based on spherical harmonics to achieve high accuracy. To overcome the limitations due to local pointing model inaccuracies and dynamic effects during tracking, an iterative trajectory learning algorithm is proposed. The implementation, as well as the stability analysis of the proposed concept is presented. Satellite tracking experiments are conducted to verify the accuracy of the proposed system. Utilizing the proposed iterative trajectory learning concept, the tracking error is reduced by a factor of 11 and is ultimately limited by the uncertainty of the orbit prediction.
       
  • Autonomy and operational concept for self-removal of spacecraft: Status
           detection, removal triggering and passivation
    • Abstract: Publication date: Available online 14 July 2019Source: Acta AstronauticaAuthor(s): Alexandra Wander, Konstantinos Konstantinidis, Roger Förstner, Philipp Voigt The growing population of space debris is posing a threat to future spacecraft in Earth orbit. The technology for self-removal of spacecraft, TeSeR, is an innovative project of eleven European partners coordinated by Airbus Defense & Space within the HORIZON2020 framework of the European Union with the goal to develop a removal module that can be carried into orbit by future spacecraft of any size and mass into any orbit, interconnected only by a standardized interface. At early 2019, a prototype shall already have demonstrated the main functions on ground. This paper introduces the mission and operational concept as well as the functional architecture and presents the autonomy considerations for the design of the overall post-mission disposal module focusing on three areas: the status detection of the host spacecraft by the developed post-mission disposal module, the removal triggering by the post-mission disposal module in case of lost link to ground station and malfunctioning host spacecraft as well as the passivation options of the host spacecraft and the post-mission disposal module itself.
       
  • Realization of methane-air continuous rotating detonation wave
    • Abstract: Publication date: November 2019Source: Acta Astronautica, Volume 164Author(s): Hao-Yang Peng, Wei-Dong Liu, Shi-Jie Liu, Hai-Long Zhang, Wei-Yong Zhou Methane-air Continuous Rotating Detonation (CRD) has been firstly achieved in this paper in the hollow chamber with a Laval nozzle, and the diameter of the chamber is just 100 mm. The contraction ratio of the Laval nozzle is a key factor for the CRD realization. CRD can only be obtained when the contraction ratio is no less than 4, but its ER operating range decreases in the increase of contraction ratio from 4 to 10. For all the success cases, the average propagation frequency and velocity are in the ranges of 5.32–5.65 kHz and 1670.48–1774.10 m/s, respectively, and the velocity deficits are less than 10%. Based on the high-speed photography images, the approach of chemiluminescence intensity integral is proposed in this paper, and the propagation characteristics of the flame are analyzed quantitatively. The propagation velocities of the flame and shock wave are agreed well with each other, indicating that the typical feature of detonation wave, i.e., the coupling of the flame and the shock wave, is verified quantitatively.
       
  • Survey on key techniques of rocket-based combined-cycle engine in ejector
           mode
    • Abstract: Publication date: Available online 13 July 2019Source: Acta AstronauticaAuthor(s): Zeyu Dong, Mingbo Sun, Zhenguo Wang, Jian Chen, Zun Cai A rocket-based combined-cycle (RBCC) engine synthetically integrates a traditional rocket engine with an airbreathing engine, effectively combining both advantages of high thrust-to-weight ratio and high specific impulse. It has become one of the most efficient propulsion systems for future reusable space transportation vehicles. In engineering practice, the engine performance during ejector mode plays a significant role in determining the efficiency of the whole RBCC propulsion system. This study aims to provide a summary report on the recent research progress on the RBCC engine in ejector mode. Firstly, the basic operating principle of the RBCC ejector mode is introduced and its ideal thermodynamic cycle process is theoretically analyzed. Secondly, the influencing factors on RBCC engine performance in ejector mode are specifically investigated, including rocket ejector parameters, geometry configurations of RBCC engine, secondary fuel injection schemes, flight Mach number and altitude. Thirdly, the research progress on key techniques of the RBCC ejector mode in recent two decades is reviewed from four aspects, namely the combustion organization, the mixing enhancement, the resistance to backpressure and the ejector/ramjet mode transition. Finally, some suggestions for the future work on the RBCC ejector mode are proposed.
       
  • Comparison of HTP catalyst performance for different internal monolith
           structures
    • Abstract: Publication date: Available online 12 July 2019Source: Acta AstronauticaAuthor(s): Robert-Jan Koopmans, Varun Reddy Nandyala, Sara Pavesi, Yann Batonneau, Romain Beauchet, Corentin Maleix, Martin Schwentenwein, Manfred Spitzbart, Altan Alpay Altun, Carsten Scharlemann A new technology for the manufacturing of 3D-printed ceramic catalyst support structures enables further optimisation of the catalyst, including the size and the internal geometry. An important design consideration for catalysts used in monopropellant thrusters is the size for a given design thrust level. A too small size may lead to only a partly decomposition of the incoming propellant. A too large size may lead to unnecessary heat loss to the environment and an excessive pressure drop. Both cases will result in a reduced performance. In the current investigation, four catalyst designs were subjected to a range of mass flow rates, thereby varying the average residence time in the chamber. It was found that shorter residence times lead to higher average chamber temperatures. This suggests that the catalyst is too large. Although the results for each internal design cannot be compared directly to each other, the convex tetrahedron design seems to be slightly better.
       
  • Personal value diversity in confinement and isolation: Pilot study results
           from the 180-day CELSS integration experiment
    • Abstract: Publication date: Available online 12 July 2019Source: Acta AstronauticaAuthor(s): Qianying Ma, Gro M. Sandal, Ruilin Wu, Jianghui Xiong, Yinghui Li, Zi Xu, Li He, Yang Liu As a major life-challenging event, being confined in an isolated environment with a small group for an extended period may make individuals re-evaluate their personal values. The present study aimed to understand the changes in personal values among Chinese crew members (n = 4) participating in a 180-day isolation and confinement experiment. The whole experiment was divided into three phases: the first and third phases followed Earth's 24-h cycle, and the second phase followed Mars' 24-h and 40-min cycle. The Portrait Values Questionnaire (PVQ) was administered once per month. Anecdotal reports provided supplementary information to further understand the value changes. The results showed a linear decrease over time in the importance attributed to power. The mean scores on benevolence during the third phase of the experiment were significantly higher than those of the first phase, while the mean scores on universalism were significantly lower in the third phase. Taken together, the findings suggest that group members may adjust personal values to accommodate living in a small group in an isolated and confinement environment over an extended period.
       
  • A centrifuge-based flight simulator: Optimization of a baseline
           acceleration profile based on the motion sickness incidence
    • Abstract: Publication date: Available online 12 July 2019Source: Acta AstronauticaAuthor(s): Rafał Lewkowicz Simulator sickness is a common problem when using centrifuge-based flight simulator. During centrifuge-based training, achieving a G-baseline level and returning to a complete stop after each G-profile still cause unpleasant sensations and motion sickness. The aim of this study was to determine the optimal G-baseline level and the optimal approach motion cueing when the centrifuge-based flight simulator achieved and returned from this G-baseline level. A model of motion sickness incidence (MSI) was used to elucidate the optimal solution of motion cueing. The motion stimuli were computed based on an inverse kinematics model of the centrifuge-based motion system. For each analysed G-baseline profile, there were stimuli that provoked the occurrence of MSI. These stimuli were directly proportional to the applied G-onset rate. There was found the optimal G-baseline level at 1.41 G and optimal motion cueing (0.05 G s−1) that gave the minimal MSI. Up to 41% and 32% a reduction in the MSI could be obtained during the achievement and return from this G-baseline level, respectively. In order to confirm obtained results further studies should be performed with participants in an actual centrifuge-based flight simulator.
       
  • The influence of external magnetic field on the plume of vacuum arc
           thruster
    • Abstract: Publication date: Available online 11 July 2019Source: Acta AstronauticaAuthor(s): Qimeng Xia, Ningfei Wang, Xianming Wu, Kan Xie, Song Bai, Zun Zhang, Liang Ren The vacuum arc thruster (VAT) is considered to be a potential micro-thruster because of its simple structure and high specific impulse. The plume downstream from the cathode spot region of a co-axial type thruster with external magnetic field is analyzed by numerical simulation. Plasma velocity, temperature and density are used to represent the influence of the cathode spot region. When the magnetic field is applied, the plume is significantly affected even at the intensity of 0.03 T. Most ions move around the magnetic induction line, forming a concentrated beam. The beam expansion angle and the ion backflow are controlled therefore. The ion beam total velocity increment is about 20% in the plume while the beam direction is determined significantly by the cathode spot position and the external magnetic field. The deflection angle of the magnetic induction line in the near-field region will bring axial velocity loss. The magnetic field intensity affects little on the ion beam velocity increment while the influence of the initial plasma density change caused by the magnetic field cannot be ignored. Ground experiment data show a large increment of ion beam velocity between the conditions with and without the magnetic field (0.03 T and 0 T), but nearly no obvious variation from 0 to 15 cm downstream of the thruster in the former condition.
       
  • An experimental and modelling study of heat loads on a subscale methane
           rocket motor
    • Abstract: Publication date: Available online 10 July 2019Source: Acta AstronauticaAuthor(s): Ye Hong, Zhanyi Liu, Simona Silvestri, Maria P. Celano, Oskar J. Haidn, Zhendong Yu Given growing competition in the business space launch market, more researchers are evaluating the merit of methane as a potential propellant. In this study, a rocket combustion chamber with a single coaxial shear injector is tested. Gaseous oxygen and gaseous methane are employed in the hot firing tests at 2 MPa and a mass ratio of oxidizer to fuel of 2.65. Along the chamber axis, the wall temperatures are recorded; an inverse heat conduction approach forms the basis of the wall heat flux calculations. By applying the CFD code ANSYS Fluent, numerical simulations offer a superior analysis of the results. To model turbulent combustion, the eddy dissipation concept model is employed. Prior to additional analysis, mesh independency has been verified with the objective of comparing the experimental data with the heat fluxes calculated from simulations. To gain a more thorough understanding of the experimentally determined heat flux profile, the hot gas temperature distribution is also examined. As the comparison proves, this study’s simulation approach predicts, with sufficient precision, wall heat fluxes in a rocket combustor.
       
  • Parameterization and optimization design of a hypersonic inward turning
           inlet
    • Abstract: Publication date: Available online 9 July 2019Source: Acta AstronauticaAuthor(s): Bing Xiong, Xiao-qiang Fan, Yi Wang To improve the performance of a hypersonic inward turning inlet, an optimization design method was proposed. A parameterization methodology was developed for an axisymmetric basic flowfield, and the geometry of a basic flowfield can be easily generated in several parameters. Preliminarily, an optimization targeting on the basic flowfield performance was conducted. As a result, the total pressure recovery of the basic flowfield was improved 7.65% compared with the referred one under the same constraints. The corresponding stream-traced inlet performance was also improved 5.65%. For further optimization, an optimization directly targeting on the 3-D inlet performance was carried out. The method of calculating along streamlines (MCS), which is for the fast calculation of a stream-traced inlet flowfield, was proposed and confirmed before this optimization. The result shows that the 3-D inlet total pressure can be further enhanced 6.74% than the previous one, and it is 12.78% higher than the referred one. That is to say, it is more reasonable to target on the inlet performance directly for an optimization, rather than targeting on the basic flowfield performance. By statistically analyzing the optimization data, it was found that the opinion “A better basic flowfield means a better stream-traced inlet” is statistically correct, but not exactly correct. The steam-traced inlet performance is not exactly determined by a basic flowfield, and it is determined by a combination of all the flow tubes the inlet captures.
       
  • Nussbaum-based robust tracking control of flexible air-breathing
           hypersonic vehicles with actuator dynamics
    • Abstract: Publication date: Available online 3 July 2019Source: Acta AstronauticaAuthor(s): Xianlei Cheng, Peng Wang, Zhaojun Mao, Wenbo Huang, Guojian Tang This paper proposes an effective control scheme to address the robust tracking control problem of the flexible air-breathing hypersonic vehicle subject to actuator dynamics. The whole vehicle dynamics is decomposed into the velocity subsystem and altitude subsystem, and the nonlinear disturbance observer based dynamic surface control is employed in the controller design within both subsystems. In order to tackle the input constraints, different hyperbolic tangent functions are carefully designed to approximate the non-smooth saturation functions. The compensators are further introduced for saturation approximations with the Nussbaum function technique. Through Lyapunov stability analysis, the closed-loop system is guaranteed to be semi-globally uniformly ultimately bounded. Moreover, the tracking and estimation errors converge to an arbitrary small neighborhood around zero. Extensive simulation and evaluations verify the superiority of the proposed scheme.
       
  • Shoulder consultations and surgery incidence rates in NASA astronauts and
           a cohort population of working individuals
    • Abstract: Publication date: Available online 10 July 2019Source: Acta AstronauticaAuthor(s): Mitzi S. Laughlin, Jocelyn D. Murray, Mary Wear, William J. Tarver, T. Bradley Edwards, Hussein A. Elkousy, Mary Van Baalen Individuals frequently seek medical care for musculoskeletal disorders of the shoulder and astronauts are no different. The purpose of this study was: 1) to determine the impact of age and sex as risk factors for orthopedic shoulder consultations and surgery in a cohort population; and 2) to determine if NASA astronauts are at a higher risk for consultations and surgery than a cohort population. The cohort (n = 347,540) was a group of working individuals that participated in a capitated insurance plan managed by their employers over a 10-year period. The astronaut cohort was comprised of NASA astronauts selected from 1959 through December 31, 2014 (n = 338). Both populations were limited to individuals between 25 and 64 years. Incidence rates indicate that age and sex were risk factors for consultation and surgery. As age increased, consultations increased significantly for both sexes in a stair-step manner. Males consistently had a higher rate than females in all age categories (all p ≤ 0.001) except for 55-64 year-olds (p = 0.228). Survival analysis confirmed that age (p 
       
 
 
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