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Showing 1 - 200 of 3120 Journals sorted alphabetically
A Practical Logic of Cognitive Systems     Full-text available via subscription   (Followers: 8)
AASRI Procedia     Open Access   (Followers: 15)
Academic Pediatrics     Hybrid Journal   (Followers: 26, SJR: 1.402, h-index: 51)
Academic Radiology     Hybrid Journal   (Followers: 22, SJR: 1.008, h-index: 75)
Accident Analysis & Prevention     Partially Free   (Followers: 90, SJR: 1.109, h-index: 94)
Accounting Forum     Hybrid Journal   (Followers: 25, SJR: 0.612, h-index: 27)
Accounting, Organizations and Society     Hybrid Journal   (Followers: 30, SJR: 2.515, h-index: 90)
Achievements in the Life Sciences     Open Access   (Followers: 4)
Acta Anaesthesiologica Taiwanica     Open Access   (Followers: 5, SJR: 0.338, h-index: 19)
Acta Astronautica     Hybrid Journal   (Followers: 380, SJR: 0.726, h-index: 43)
Acta Automatica Sinica     Full-text available via subscription   (Followers: 3)
Acta Biomaterialia     Hybrid Journal   (Followers: 26, SJR: 2.02, h-index: 104)
Acta Colombiana de Cuidado Intensivo     Full-text available via subscription   (Followers: 1)
Acta de Investigación Psicológica     Open Access   (Followers: 2)
Acta Ecologica Sinica     Open Access   (Followers: 8, SJR: 0.172, h-index: 29)
Acta Haematologica Polonica     Free   (Followers: 1, SJR: 0.123, h-index: 8)
Acta Histochemica     Hybrid Journal   (Followers: 3, SJR: 0.604, h-index: 38)
Acta Materialia     Hybrid Journal   (Followers: 238, SJR: 3.683, h-index: 202)
Acta Mathematica Scientia     Full-text available via subscription   (Followers: 5, SJR: 0.615, h-index: 21)
Acta Mechanica Solida Sinica     Full-text available via subscription   (Followers: 9, SJR: 0.442, h-index: 21)
Acta Oecologica     Hybrid Journal   (Followers: 10, SJR: 0.915, h-index: 53)
Acta Otorrinolaringologica (English Edition)     Full-text available via subscription   (Followers: 1)
Acta Otorrinolaringológica Española     Full-text available via subscription   (Followers: 3, SJR: 0.311, h-index: 16)
Acta Pharmaceutica Sinica B     Open Access   (Followers: 2)
Acta Poética     Open Access   (Followers: 4)
Acta Psychologica     Hybrid Journal   (Followers: 25, SJR: 1.365, h-index: 73)
Acta Sociológica     Open Access  
Acta Tropica     Hybrid Journal   (Followers: 6, SJR: 1.059, h-index: 77)
Acta Urológica Portuguesa     Open Access  
Actas Dermo-Sifiliograficas     Full-text available via subscription   (Followers: 4)
Actas Dermo-Sifiliográficas (English Edition)     Full-text available via subscription   (Followers: 3)
Actas Urológicas Españolas     Full-text available via subscription   (Followers: 4, SJR: 0.383, h-index: 19)
Actas Urológicas Españolas (English Edition)     Full-text available via subscription   (Followers: 2)
Actualites Pharmaceutiques     Full-text available via subscription   (Followers: 5, SJR: 0.141, h-index: 3)
Actualites Pharmaceutiques Hospitalieres     Full-text available via subscription   (Followers: 4, SJR: 0.112, h-index: 2)
Acupuncture and Related Therapies     Hybrid Journal   (Followers: 5)
Acute Pain     Full-text available via subscription   (Followers: 13)
Ad Hoc Networks     Hybrid Journal   (Followers: 11, SJR: 0.967, h-index: 57)
Addictive Behaviors     Hybrid Journal   (Followers: 15, SJR: 1.514, h-index: 92)
Addictive Behaviors Reports     Open Access   (Followers: 7)
Additive Manufacturing     Hybrid Journal   (Followers: 7, SJR: 1.039, h-index: 5)
Additives for Polymers     Full-text available via subscription   (Followers: 22)
Advanced Cement Based Materials     Full-text available via subscription   (Followers: 3)
Advanced Drug Delivery Reviews     Hybrid Journal   (Followers: 139, SJR: 5.2, h-index: 222)
Advanced Engineering Informatics     Hybrid Journal   (Followers: 11, SJR: 1.265, h-index: 53)
Advanced Powder Technology     Hybrid Journal   (Followers: 17, SJR: 0.739, h-index: 33)
Advances in Accounting     Hybrid Journal   (Followers: 9, SJR: 0.299, h-index: 15)
Advances in Agronomy     Full-text available via subscription   (Followers: 15, SJR: 2.071, h-index: 82)
Advances in Anesthesia     Full-text available via subscription   (Followers: 27, SJR: 0.169, h-index: 4)
Advances in Antiviral Drug Design     Full-text available via subscription   (Followers: 4)
Advances in Applied Mathematics     Full-text available via subscription   (Followers: 9, SJR: 1.054, h-index: 35)
Advances in Applied Mechanics     Full-text available via subscription   (Followers: 12, SJR: 0.801, h-index: 26)
Advances in Applied Microbiology     Full-text available via subscription   (Followers: 23, SJR: 1.286, h-index: 49)
Advances In Atomic, Molecular, and Optical Physics     Full-text available via subscription   (Followers: 16, SJR: 3.31, h-index: 42)
Advances in Biological Regulation     Hybrid Journal   (Followers: 4, SJR: 2.277, h-index: 43)
Advances in Botanical Research     Full-text available via subscription   (Followers: 3, SJR: 0.619, h-index: 48)
Advances in Cancer Research     Full-text available via subscription   (Followers: 26, SJR: 2.215, h-index: 78)
Advances in Carbohydrate Chemistry and Biochemistry     Full-text available via subscription   (Followers: 9, SJR: 0.9, h-index: 30)
Advances in Catalysis     Full-text available via subscription   (Followers: 6, SJR: 2.139, h-index: 42)
Advances in Cell Aging and Gerontology     Full-text available via subscription   (Followers: 4)
Advances in Cellular and Molecular Biology of Membranes and Organelles     Full-text available via subscription   (Followers: 13)
Advances in Chemical Engineering     Full-text available via subscription   (Followers: 26, SJR: 0.183, h-index: 23)
Advances in Child Development and Behavior     Full-text available via subscription   (Followers: 10, SJR: 0.665, h-index: 29)
Advances in Chronic Kidney Disease     Full-text available via subscription   (Followers: 9, SJR: 1.268, h-index: 45)
Advances in Clinical Chemistry     Full-text available via subscription   (Followers: 29, SJR: 0.938, h-index: 33)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 18, SJR: 2.314, h-index: 130)
Advances in Computers     Full-text available via subscription   (Followers: 16, SJR: 0.223, h-index: 22)
Advances in Dermatology     Full-text available via subscription   (Followers: 12)
Advances in Developmental Biology     Full-text available via subscription   (Followers: 12)
Advances in Digestive Medicine     Open Access   (Followers: 7)
Advances in DNA Sequence-Specific Agents     Full-text available via subscription   (Followers: 6)
Advances in Drug Research     Full-text available via subscription   (Followers: 23)
Advances in Ecological Research     Full-text available via subscription   (Followers: 47, SJR: 3.25, h-index: 43)
Advances in Engineering Software     Hybrid Journal   (Followers: 27, SJR: 0.486, h-index: 10)
Advances in Experimental Biology     Full-text available via subscription   (Followers: 9)
Advances in Experimental Social Psychology     Full-text available via subscription   (Followers: 46, SJR: 5.465, h-index: 64)
Advances in Exploration Geophysics     Full-text available via subscription   (Followers: 3)
Advances in Food and Nutrition Research     Full-text available via subscription   (Followers: 52, SJR: 0.674, h-index: 38)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 16)
Advances in Genetics     Full-text available via subscription   (Followers: 17, SJR: 2.558, h-index: 54)
Advances in Genome Biology     Full-text available via subscription   (Followers: 11)
Advances in Geophysics     Full-text available via subscription   (Followers: 6, SJR: 2.325, h-index: 20)
Advances in Heat Transfer     Full-text available via subscription   (Followers: 22, SJR: 0.906, h-index: 24)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 9, SJR: 0.497, h-index: 31)
Advances in Human Factors/Ergonomics     Full-text available via subscription   (Followers: 27)
Advances in Imaging and Electron Physics     Full-text available via subscription   (Followers: 2, SJR: 0.396, h-index: 27)
Advances in Immunology     Full-text available via subscription   (Followers: 36, SJR: 4.152, h-index: 85)
Advances in Inorganic Chemistry     Full-text available via subscription   (Followers: 9, SJR: 1.132, h-index: 42)
Advances in Insect Physiology     Full-text available via subscription   (Followers: 3, SJR: 1.274, h-index: 27)
Advances in Integrative Medicine     Hybrid Journal   (Followers: 6)
Advances in Intl. Accounting     Full-text available via subscription   (Followers: 4)
Advances in Life Course Research     Hybrid Journal   (Followers: 8, SJR: 0.764, h-index: 15)
Advances in Lipobiology     Full-text available via subscription   (Followers: 2)
Advances in Magnetic and Optical Resonance     Full-text available via subscription   (Followers: 10)
Advances in Marine Biology     Full-text available via subscription   (Followers: 16, SJR: 1.645, h-index: 45)
Advances in Mathematics     Full-text available via subscription   (Followers: 10, SJR: 3.261, h-index: 65)
Advances in Medical Sciences     Hybrid Journal   (Followers: 6, SJR: 0.489, h-index: 25)
Advances in Medicinal Chemistry     Full-text available via subscription   (Followers: 6)
Advances in Microbial Physiology     Full-text available via subscription   (Followers: 5, SJR: 1.44, h-index: 51)
Advances in Molecular and Cell Biology     Full-text available via subscription   (Followers: 23)
Advances in Molecular and Cellular Endocrinology     Full-text available via subscription   (Followers: 10)
Advances in Molecular Toxicology     Full-text available via subscription   (Followers: 9, SJR: 0.324, h-index: 8)
Advances in Nanoporous Materials     Full-text available via subscription   (Followers: 4)
Advances in Oncobiology     Full-text available via subscription   (Followers: 2)
Advances in Organ Biology     Full-text available via subscription   (Followers: 2)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 15, SJR: 2.885, h-index: 45)
Advances in Parallel Computing     Full-text available via subscription   (Followers: 7, SJR: 0.148, h-index: 11)
Advances in Parasitology     Full-text available via subscription   (Followers: 7, SJR: 2.37, h-index: 73)
Advances in Pediatrics     Full-text available via subscription   (Followers: 24, SJR: 0.4, h-index: 28)
Advances in Pharmaceutical Sciences     Full-text available via subscription   (Followers: 13)
Advances in Pharmacology     Full-text available via subscription   (Followers: 16, SJR: 1.718, h-index: 58)
Advances in Physical Organic Chemistry     Full-text available via subscription   (Followers: 8, SJR: 0.384, h-index: 26)
Advances in Phytomedicine     Full-text available via subscription  
Advances in Planar Lipid Bilayers and Liposomes     Full-text available via subscription   (Followers: 3, SJR: 0.248, h-index: 11)
Advances in Plant Biochemistry and Molecular Biology     Full-text available via subscription   (Followers: 7)
Advances in Plant Pathology     Full-text available via subscription   (Followers: 5)
Advances in Porous Media     Full-text available via subscription   (Followers: 5)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 18)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 20, SJR: 1.5, h-index: 62)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 6, SJR: 0.478, h-index: 32)
Advances in Radiation Oncology     Open Access  
Advances in Small Animal Medicine and Surgery     Hybrid Journal   (Followers: 3, SJR: 0.1, h-index: 2)
Advances in Space Biology and Medicine     Full-text available via subscription   (Followers: 5)
Advances in Space Research     Full-text available via subscription   (Followers: 371, SJR: 0.606, h-index: 65)
Advances in Structural Biology     Full-text available via subscription   (Followers: 8)
Advances in Surgery     Full-text available via subscription   (Followers: 9, SJR: 0.823, h-index: 27)
Advances in the Study of Behavior     Full-text available via subscription   (Followers: 31, SJR: 1.321, h-index: 56)
Advances in Veterinary Medicine     Full-text available via subscription   (Followers: 16)
Advances in Veterinary Science and Comparative Medicine     Full-text available via subscription   (Followers: 13)
Advances in Virus Research     Full-text available via subscription   (Followers: 6, SJR: 1.878, h-index: 68)
Advances in Water Resources     Hybrid Journal   (Followers: 45, SJR: 2.408, h-index: 94)
Aeolian Research     Hybrid Journal   (Followers: 5, SJR: 0.973, h-index: 22)
Aerospace Science and Technology     Hybrid Journal   (Followers: 338, SJR: 0.816, h-index: 49)
AEU - Intl. J. of Electronics and Communications     Hybrid Journal   (Followers: 8, SJR: 0.318, h-index: 36)
African J. of Emergency Medicine     Open Access   (Followers: 6, SJR: 0.344, h-index: 6)
Ageing Research Reviews     Hybrid Journal   (Followers: 9, SJR: 3.289, h-index: 78)
Aggression and Violent Behavior     Hybrid Journal   (Followers: 433, SJR: 1.385, h-index: 72)
Agri Gene     Hybrid Journal  
Agricultural and Forest Meteorology     Hybrid Journal   (Followers: 15, SJR: 2.18, h-index: 116)
Agricultural Systems     Hybrid Journal   (Followers: 31, SJR: 1.275, h-index: 74)
Agricultural Water Management     Hybrid Journal   (Followers: 42, SJR: 1.546, h-index: 79)
Agriculture and Agricultural Science Procedia     Open Access  
Agriculture and Natural Resources     Open Access   (Followers: 3)
Agriculture, Ecosystems & Environment     Hybrid Journal   (Followers: 56, SJR: 1.879, h-index: 120)
Ain Shams Engineering J.     Open Access   (Followers: 5, SJR: 0.434, h-index: 14)
Air Medical J.     Hybrid Journal   (Followers: 5, SJR: 0.234, h-index: 18)
AKCE Intl. J. of Graphs and Combinatorics     Open Access   (SJR: 0.285, h-index: 3)
Alcohol     Hybrid Journal   (Followers: 11, SJR: 0.922, h-index: 66)
Alcoholism and Drug Addiction     Open Access   (Followers: 8)
Alergologia Polska : Polish J. of Allergology     Full-text available via subscription   (Followers: 1)
Alexandria Engineering J.     Open Access   (Followers: 1, SJR: 0.436, h-index: 12)
Alexandria J. of Medicine     Open Access   (Followers: 1)
Algal Research     Partially Free   (Followers: 9, SJR: 2.05, h-index: 20)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 3)
Allergologia et Immunopathologia     Full-text available via subscription   (Followers: 1, SJR: 0.46, h-index: 29)
Allergology Intl.     Open Access   (Followers: 4, SJR: 0.776, h-index: 35)
Alpha Omegan     Full-text available via subscription   (SJR: 0.121, h-index: 9)
ALTER - European J. of Disability Research / Revue Européenne de Recherche sur le Handicap     Full-text available via subscription   (Followers: 9, SJR: 0.158, h-index: 9)
Alzheimer's & Dementia     Hybrid Journal   (Followers: 49, SJR: 4.289, h-index: 64)
Alzheimer's & Dementia: Diagnosis, Assessment & Disease Monitoring     Open Access   (Followers: 4)
Alzheimer's & Dementia: Translational Research & Clinical Interventions     Open Access   (Followers: 4)
Ambulatory Pediatrics     Hybrid Journal   (Followers: 5)
American Heart J.     Hybrid Journal   (Followers: 48, SJR: 3.157, h-index: 153)
American J. of Cardiology     Hybrid Journal   (Followers: 48, SJR: 2.063, h-index: 186)
American J. of Emergency Medicine     Hybrid Journal   (Followers: 42, SJR: 0.574, h-index: 65)
American J. of Geriatric Pharmacotherapy     Full-text available via subscription   (Followers: 9, SJR: 1.091, h-index: 45)
American J. of Geriatric Psychiatry     Hybrid Journal   (Followers: 14, SJR: 1.653, h-index: 93)
American J. of Human Genetics     Hybrid Journal   (Followers: 32, SJR: 8.769, h-index: 256)
American J. of Infection Control     Hybrid Journal   (Followers: 26, SJR: 1.259, h-index: 81)
American J. of Kidney Diseases     Hybrid Journal   (Followers: 31, SJR: 2.313, h-index: 172)
American J. of Medicine     Hybrid Journal   (Followers: 45, SJR: 2.023, h-index: 189)
American J. of Medicine Supplements     Full-text available via subscription   (Followers: 3)
American J. of Obstetrics and Gynecology     Hybrid Journal   (Followers: 207, SJR: 2.255, h-index: 171)
American J. of Ophthalmology     Hybrid Journal   (Followers: 61, SJR: 2.803, h-index: 148)
American J. of Ophthalmology Case Reports     Open Access   (Followers: 6)
American J. of Orthodontics and Dentofacial Orthopedics     Full-text available via subscription   (Followers: 6, SJR: 1.249, h-index: 88)
American J. of Otolaryngology     Hybrid Journal   (Followers: 24, SJR: 0.59, h-index: 45)
American J. of Pathology     Hybrid Journal   (Followers: 27, SJR: 2.653, h-index: 228)
American J. of Preventive Medicine     Hybrid Journal   (Followers: 26, SJR: 2.764, h-index: 154)
American J. of Surgery     Hybrid Journal   (Followers: 36, SJR: 1.286, h-index: 125)
American J. of the Medical Sciences     Hybrid Journal   (Followers: 12, SJR: 0.653, h-index: 70)
Ampersand : An Intl. J. of General and Applied Linguistics     Open Access   (Followers: 6)
Anaerobe     Hybrid Journal   (Followers: 4, SJR: 1.066, h-index: 51)
Anaesthesia & Intensive Care Medicine     Full-text available via subscription   (Followers: 60, SJR: 0.124, h-index: 9)
Anaesthesia Critical Care & Pain Medicine     Full-text available via subscription   (Followers: 14)
Anales de Cirugia Vascular     Full-text available via subscription  
Anales de Pediatría     Full-text available via subscription   (Followers: 2, SJR: 0.209, h-index: 27)
Anales de Pediatría (English Edition)     Full-text available via subscription  
Anales de Pediatría Continuada     Full-text available via subscription   (SJR: 0.104, h-index: 3)
Analytic Methods in Accident Research     Hybrid Journal   (Followers: 4, SJR: 2.577, h-index: 7)
Analytica Chimica Acta     Hybrid Journal   (Followers: 36, SJR: 1.548, h-index: 152)
Analytical Biochemistry     Hybrid Journal   (Followers: 172, SJR: 0.725, h-index: 154)
Analytical Chemistry Research     Open Access   (Followers: 8, SJR: 0.18, h-index: 2)
Analytical Spectroscopy Library     Full-text available via subscription   (Followers: 12)
Anesthésie & Réanimation     Full-text available via subscription   (Followers: 1)
Anesthesiology Clinics     Full-text available via subscription   (Followers: 22, SJR: 0.421, h-index: 40)
Angiología     Full-text available via subscription   (SJR: 0.124, h-index: 9)
Angiologia e Cirurgia Vascular     Open Access  
Animal Behaviour     Hybrid Journal   (Followers: 177, SJR: 1.907, h-index: 126)
Animal Feed Science and Technology     Hybrid Journal   (Followers: 5, SJR: 1.151, h-index: 83)

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Journal Cover Acta Astronautica
  [SJR: 0.726]   [H-I: 43]   [380 followers]  Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0094-5765
   Published by Elsevier Homepage  [3123 journals]
  • Onboard autonomous mission re-planning for multi-satellite system
    • Authors: Zixuan Zheng; Jian Guo; Eberhard Gill
      Pages: 28 - 43
      Abstract: Publication date: April 2018
      Source:Acta Astronautica, Volume 145
      Author(s): Zixuan Zheng, Jian Guo, Eberhard Gill
      This paper presents an onboard autonomous mission re-planning system for Multi-Satellites System (MSS) to perform onboard re-planing in disruptive situations. The proposed re-planning system can deal with different potential emergency situations. This paper uses Multi-Objective Hybrid Dynamic Mutation Genetic Algorithm (MO-HDM GA) combined with re-planning techniques as the core algorithm. The Cyclically Re-planning Method (CRM) and the Near Real-time Re-planning Method (NRRM) are developed to meet different mission requirements. Simulations results show that both methods can provide feasible re-planning sequences under unforeseen situations. The comparisons illustrate that using the CRM is average 20 % faster than the NRRM on computation time. However, by using the NRRM more raw data can be observed and transmitted than using the CRM within the same period. The usability of this onboard re-planning system is not limited to multi-satellite system. Other mission planning and re-planning problems related to autonomous multiple vehicles with similar demands are also applicable.

      PubDate: 2018-02-04T23:09:28Z
      DOI: 10.1016/j.actaastro.2018.01.017
      Issue No: Vol. 145 (2018)
  • Effect of fertilizer prepared from human feces and straw on germination,
           growth and development of wheat
    • Authors: Dianlei Liu; Beizhen Xie; Chen Dong; Guanghui Liu; Dawei Hu; Youcai Qin; Hongyan Li; Hong Liu
      Pages: 76 - 82
      Abstract: Publication date: April 2018
      Source:Acta Astronautica, Volume 145
      Author(s): Dianlei Liu, Beizhen Xie, Chen Dong, Guanghui Liu, Dawei Hu, Youcai Qin, Hongyan Li, Hong Liu
      Solid waste treatment is one of the most important rate-limiting steps in the material circulation and energy flow of Bioregenerative Life Support System (BLSS). In our previous work, an efficient and controllable solid waste bio-convertor has been built and a solid waste degradation efficiency of 41.0% has been reached during a 105-d BLSS experiment. However, the fermented residues should be further utilized to fulfill the closure of the system. One solution might be to use the residues as the fertilizer for plant cultivation. Thus in this study, substrates were prepared using different ratios of the fermented residues to the vermiculite. And the influences of different ratios of the fermented residues on the seed germination, growth, photosynthetic characteristics and antioxidant capacity of wheat were studied. The results showed that the optimal rate of the fermented residue was 5%. With this ratio, the seed germination reached 97.3% with the root length, shoot length and biomass production as 59 mm, 52 mm and 150 mg, respectively, at the 4th day. Besides, the highest straw height of 25.1 cm was obtained at the 21st day. The salinity adversely affected the growth and some relevant metabolic processes of wheat. The Group-40% led to the lowest seed germination of 34.7% and the minimum straw height of 15 cm. This inhibition might be caused by the high Na content of 2118 mg/kg in the fermented residues. Chlorophyll b was more sensitive to the mineral nutrition stress and affects the wheat photosynthetic characteristics. Higher reactive oxygen species levels and reduced antioxidant enzymes may contribute, directly and/or indirectly, to the decline in the observed pigment contents in wheat.

      PubDate: 2018-02-04T23:09:28Z
      DOI: 10.1016/j.actaastro.2018.01.014
      Issue No: Vol. 145 (2018)
  • Review on pressure swirl injector in liquid rocket engine
    • Authors: Zhongtao Kang; Zhen-guo Wang; Qinglian Li; Peng Cheng
      Pages: 174 - 198
      Abstract: Publication date: April 2018
      Source:Acta Astronautica, Volume 145
      Author(s): Zhongtao Kang, Zhen-guo Wang, Qinglian Li, Peng Cheng
      The pressure swirl injector with tangential inlet ports is widely used in liquid rocket engine. Commonly, this type of pressure swirl injector consists of tangential inlet ports, a swirl chamber, a converging spin chamber, and a discharge orifice. The atomization of the liquid propellants includes the formation of liquid film, primary breakup and secondary atomization. And the back pressure and temperature in the combustion chamber could have great influence on the atomization of the injector. What's more, when the combustion instability occurs, the pressure oscillation could further affects the atomization process. This paper reviewed the primary atomization and the performance of the pressure swirl injector, which include the formation of the conical liquid film, the breakup and atomization characteristics of the conical liquid film, the effects of the rocket engine environment, and the response of the injector and atomization on the pressure oscillation.

      PubDate: 2018-02-04T23:09:28Z
      DOI: 10.1016/j.actaastro.2017.12.038
      Issue No: Vol. 145 (2018)
  • Observer enhanced control for spin-stabilized tethered formation in earth
    • Authors: Zhai Guang; Li Yuyang; Bin Liang
      Pages: 216 - 228
      Abstract: Publication date: April 2018
      Source:Acta Astronautica, Volume 145
      Author(s): Zhai Guang, Li Yuyang, Bin Liang
      This paper addresses the issues relevant to control of spin-stabilized tethered formation in circular orbit. Due to the dynamic complexities and nonlinear perturbations, it is challenging to promote the control precision for the formation deployment and maintenance. In this work, the formation dynamics are derived with considering the spinning rate of the central body, then major attention is dedicated to develop the nonlinear disturbance observer. To achieve better control performance, the observer-enhanced controller is designed by incorporating the disturbance observer into the control loop, benefits from the disturbance compensation are demonstrated, and also, the dependences of the disturbance observer performance on some important parameters are theoretically and numerically analyzed.

      PubDate: 2018-02-04T23:09:28Z
      DOI: 10.1016/j.actaastro.2017.12.049
      Issue No: Vol. 145 (2018)
  • Validation of vibration-dissociation coupling models in hypersonic
           non-equilibrium separated flows
    • Authors: G. Shoev; G. Oblapenko; O. Kunova; M. Mekhonoshina; E. Kustova
      Pages: 147 - 159
      Abstract: Publication date: March 2018
      Source:Acta Astronautica, Volume 144
      Author(s): G. Shoev, G. Oblapenko, O. Kunova, M. Mekhonoshina, E. Kustova
      The validation of recently developed models of vibration-dissociation coupling is discussed in application to numerical solutions of the Navier–Stokes equations in a two-temperature approximation for a binary N2/N flow. Vibrational-translational relaxation rates are computed using the Landau–Teller formula generalized for strongly non-equilibrium flows obtained in the framework of the Chapman–Enskog method. Dissociation rates are calculated using the modified Treanor–Marrone model taking into account the dependence of the model parameter on the vibrational state. The solutions are compared to those obtained using traditional Landau–Teller and Treanor–Marrone models, and it is shown that for high-enthalpy flows, the traditional and recently developed models can give significantly different results. The computed heat flux and pressure on the surface of a double cone are in a good agreement with experimental data available in the literature on low-enthalpy flow with strong thermal non-equilibrium. The computed heat flux on a double wedge qualitatively agrees with available data for high-enthalpy non-equilibrium flows. Different contributions to the heat flux calculated using rigorous kinetic theory methods are evaluated. Quantitative discrepancy of numerical and experimental data is discussed.

      PubDate: 2018-02-04T23:09:28Z
      DOI: 10.1016/j.actaastro.2017.12.023
      Issue No: Vol. 144 (2018)
  • Fixed-axis electric sail deployment dynamics analysis using hub-mounted
           momentum control
    • Authors: JoAnna Fulton; Hanspeter Schaub
      Pages: 160 - 170
      Abstract: Publication date: March 2018
      Source:Acta Astronautica, Volume 144
      Author(s): JoAnna Fulton, Hanspeter Schaub
      The deployment dynamics of a spin stabilized electric sail (E-sail) with a hub-mounted control actuator are investigated. Both radial and tangential deployment mechanisms are considered to take the electric sail from a post-launch stowed configuration to a fully deployed configuration. The tangential configuration assumes the multi-kilometer tethers are wound up on the exterior of the spacecraft hub, similar to yo-yo despinner configurations. The deployment speed is controlled through the hub rate. The radial deployment configuration assumes each tether is on its own spool. Here both the hub and spool rate are control variables. The sensitivity of the deployment behavior to E-sail length, maximum rate and tension parameters is investigated. A constant hub rate deployment is compared to a time varying hub rate that maintains a constant tether tension condition. The deployment time can be reduced by a factor of 2 or more by using a tension controlled deployment configuration.

      PubDate: 2018-02-04T23:09:28Z
      DOI: 10.1016/j.actaastro.2017.11.048
      Issue No: Vol. 144 (2018)
  • Geomagnetic field models for satellite angular motion studies
    • Authors: M. Yu. Ovchinnikov; V.I. Penkov; D.S. Roldugin; A.V. Pichuzhkina
      Pages: 171 - 180
      Abstract: Publication date: March 2018
      Source:Acta Astronautica, Volume 144
      Author(s): M. Yu. Ovchinnikov, V.I. Penkov, D.S. Roldugin, A.V. Pichuzhkina
      Four geomagnetic field models are discussed: IGRF, inclined, direct and simplified dipoles. Geomagnetic induction vector expressions are provided in different reference frames. Induction vector behavior is compared for different models. Models applicability for the analysis of satellite motion is studied from theoretical and engineering perspectives. Relevant satellite dynamics analysis cases using analytical and numerical techniques are provided. These cases demonstrate the benefit of a certain model for a specific dynamics study. Recommendations for models usage are summarized in the end.

      PubDate: 2018-02-04T23:09:28Z
      DOI: 10.1016/j.actaastro.2017.12.026
      Issue No: Vol. 144 (2018)
  • Hydrogen jet combustion in a scramjet combustor with the
           rearwall-expansion cavity
    • Authors: Yan-Xiang Zhang; Zhen-Guo Wang; Ming-Bo Sun; Yi-Xin Yang; Hong-Bo Wang
      Pages: 181 - 192
      Abstract: Publication date: March 2018
      Source:Acta Astronautica, Volume 144
      Author(s): Yan-Xiang Zhang, Zhen-Guo Wang, Ming-Bo Sun, Yi-Xin Yang, Hong-Bo Wang
      This study is carried out to experimentally investigate the combustion characteristics of the hydrogen jet flame stabilized by the rearwall-expansion cavity in a model scramjet combustor. The flame distributions are characterized by the OH* spontaneous emission images, and the dynamic features of the flames are studied through the high speed framing of the flame luminosity. The combustion modes are further analyzed based on the visual flame structure and wall pressure distributions. Under the present conditions, the combustion based on the rearwall-expansion cavity appears in two distinguished modes – the typical cavity shear-layer stabilized combustion mode and the lifted-shear-layer stabilized combustion mode. In contrast with the shear-layer stabilized mode, the latter holds stronger flame. The transition from shear-layer stabilized combustion mode to lifted-shear-layer stabilized mode usually occurs when the equivalence ratio is high enough. While the increases of the offset ratio and upstream injection distance both lead to weaker jet-cavity interactions, cause longer ignition delay, and thus delay the mode transition. The results reveal that the rearwall-expansion cavity with an appropriate offset ratio should be helpful in delaying mode transition and preventing thermal choke, and meanwhile just brings minor negative impact on the combustion stability and efficiency.

      PubDate: 2018-02-04T23:09:28Z
      DOI: 10.1016/j.actaastro.2017.12.029
      Issue No: Vol. 144 (2018)
  • Effects of cusped field thruster on the performance of drag-free control
    • Authors: K. Cui; H. Liu; W.J. Jiang; Q.Q. Sun; P. Hu; D.R. Yu
      Pages: 193 - 200
      Abstract: Publication date: March 2018
      Source:Acta Astronautica, Volume 144
      Author(s): K. Cui, H. Liu, W.J. Jiang, Q.Q. Sun, P. Hu, D.R. Yu
      With increased measurement tasks of space science, more requirements for the spacecraft environment have been put forward. Those tasks (e.g. the measurement of Earth's steady state gravity field anomalies) lead to the desire for developing drag-free control. Higher requirements for the thruster performance are made due to the demand for the drag-free control system and real-time compensation for non-conservative forces. Those requirements for the propulsion system include wide continuous throttling ability, high resolution, rapid response, low noise and so on. As a promising candidate, the cusped field thruster has features such as the high working stability, the low erosion rate, a long lifetime and the simple structure, so that it is chosen as the thruster to be discussed in this paper. Firstly, the performance of a new cusped field thruster is tested and analyzed. Then a drag-free control scheme based on the cusped field thruster is designed to evaluate the performance of this thruster. Subsequently, the effects of the thrust resolution, transient response time and thrust uncertainty on the controller are calculated respectively. Finally, the performance of closed-loop system is analyzed, and the simulation results verify the feasibility of applying cusped field thruster to drag-free flight in the space science measurement tasks.

      PubDate: 2018-02-04T23:09:28Z
      DOI: 10.1016/j.actaastro.2017.12.032
      Issue No: Vol. 144 (2018)
  • Erratum to “On guided wave propagation in fully clamped porous
           functionally graded nanoplates” [Acta Astronaut. 143 (2018) 380–390]
    • Authors: Behrouz Karami; Maziar Janghorban; Li Li
      First page: 201
      Abstract: Publication date: March 2018
      Source:Acta Astronautica, Volume 144
      Author(s): Behrouz Karami, Maziar Janghorban, Li Li

      PubDate: 2018-02-04T23:09:28Z
      DOI: 10.1016/j.actaastro.2017.12.042
      Issue No: Vol. 144 (2018)
  • Chagas disease study using satellite image processing: A Bolivian case
    • Authors: Natalia I. Vargas-Cuentas; Avid Roman-Gonzalez; Alicia Alva Mantari; Luis AnthonyAucapuma Muñoz
      Pages: 216 - 224
      Abstract: Publication date: March 2018
      Source:Acta Astronautica, Volume 144
      Author(s): Natalia I. Vargas-Cuentas, Avid Roman-Gonzalez, Alicia Alva Mantari, Luis AnthonyAucapuma Muñoz
      Remote sensing is the technology that has enabled us to obtain information about the Earth's surface without directly contacting it. For this reason, currently, the Bolivian state has considered a list of interesting applications of remote sensing in the country, including the following: biodiversity and environment monitoring, mining and geology, epidemiology, agriculture, water resources and land use planning. The use of satellite images has become a great tool for epidemiology because with this technological advance we can determine the environment in which transmission occurs, the distribution of the disease and its evolution over time. In that context, one of the important diseases related to public health in Bolivia is Chagas disease, also known as South American Trypanosomiasis. Chagas is caused by a blood-sucking bug or Vinchuca, which causes serious intestinal and heart long term problems and affects 33.4% of the Bolivian population. This disease affects mostly humble people, so the Bolivian state invests millions of dollars to acquire medicine and distribute it for free. Due to the above reasons, the present research aims to analyze some areas of Bolivia using satellite images for developing an epidemiology study. The primary objective is to understand the environment in which the transmission of the disease happens, and the climatic conditions under which occurs, observe the behavior of the blood-sucking bug, identify in which months occur higher outbreaks, in which months the bug leaves its eggs, and under which weather conditions this happens. All this information would be contrasted with information extracted from the satellite images and data from the Ministry of Health, and the Institute of Meteorology in Bolivia. All this data will allow us to have a more integrated understanding of this disease and promote new possibilities to prevent and control it.

      PubDate: 2018-02-04T23:09:28Z
      DOI: 10.1016/j.actaastro.2017.12.039
      Issue No: Vol. 144 (2018)
  • Assessment of active methods for removal of LEO debris
    • Authors: Houman Hakima; M. Reza Emami
      Pages: 225 - 243
      Abstract: Publication date: March 2018
      Source:Acta Astronautica, Volume 144
      Author(s): Houman Hakima, M. Reza Emami
      This paper investigates the applicability of five active methods for removal of large low Earth orbit debris. The removal methods, namely net, laser, electrodynamic tether, ion beam shepherd, and robotic arm, are selected based on a set of high-level space mission constraints. Mission level criteria are then utilized to assess the performance of each redirection method in light of the results obtained from a Monte Carlo simulation. The simulation provides an insight into the removal time, performance robustness, and propellant mass criteria for the targeted debris range. The remaining attributes are quantified based on the models provided in the literature, which take into account several important parameters pertaining to each removal method. The means of assigning attributes to each assessment criterion is discussed in detail. A systematic comparison is performed using two different assessment schemes: Analytical Hierarchy Process and utility-based approach. A third assessment technique, namely the potential-loss analysis, is utilized to highlight the effect of risks in each removal methods.

      PubDate: 2018-02-04T23:09:28Z
      DOI: 10.1016/j.actaastro.2017.12.036
      Issue No: Vol. 144 (2018)
  • CFD analysis of a scramjet combustor with cavity based flame holders
    • Authors: Obula Reddy Kummitha; Krishna Murari Pandey; Rajat Gupta
      Pages: 244 - 253
      Abstract: Publication date: March 2018
      Source:Acta Astronautica, Volume 144
      Author(s): Obula Reddy Kummitha, Krishna Murari Pandey, Rajat Gupta
      Numerical analysis of a scramjet combustor with different cavity flame holders has been carried out using ANSYS 16 - FLUENT tool. In this research article the internal fluid flow behaviour of the scramjet combustor with different cavity based flame holders have been discussed in detail. Two dimensional Reynolds-Averaged Navier-Stokes governing(RANS) equations and shear stress turbulence (SST) k − ω model along with finite rate/eddy dissipation chemistry turbulence have been considered for modelling chemical reacting flows. Due to the advantage of less computational time, global one step reaction mechanism has been used for combustion modelling of hydrogen and air. The performance of the scramjet combustor with two different cavities namely spherical and step cavity has been compared with the standard DLR scramjet. From the comparison of numerical results, it is found that the development of recirculation regions and additional shock waves from the edge of cavity flame holder is increased. And also it is observed that with the cavity flame holder the residence time of air in the scramjet combustor is also increased and achieved stabilized combustion. From this research analysis, it has been found that the mixing and combustion efficiency of scramjet combustor with step cavity design is optimum as compared to other models.

      PubDate: 2018-02-04T23:09:28Z
      DOI: 10.1016/j.actaastro.2018.01.005
      Issue No: Vol. 144 (2018)
  • Radiation production and absorption in human spacecraft shielding systems
           under high charge and energy Galactic Cosmic Rays: Material medium,
           shielding depth, and byproduct aspects
    • Authors: Joseph Barthel; Nesrin Sarigul-Klijn
      Pages: 254 - 262
      Abstract: Publication date: March 2018
      Source:Acta Astronautica, Volume 144
      Author(s): Joseph Barthel, Nesrin Sarigul-Klijn
      Deep space missions such as the planned 2025 mission to asteroids require spacecraft shields to protect electronics and humans from adverse effects caused by the space radiation environment, primarily Galactic Cosmic Rays. This paper first reviews the theory on how these rays of charged particles interact with matter, and then presents a simulation for a 500 day Mars flyby mission using a deterministic based computer code. High density polyethylene and aluminum shielding materials at a solar minimum are considered. Plots of effective dose with varying shield depth, charged particle flux, and dose in silicon and human tissue behind shielding are presented.

      PubDate: 2018-02-04T23:09:28Z
      DOI: 10.1016/j.actaastro.2017.12.040
      Issue No: Vol. 144 (2018)
  • A novel adaptive finite time controller for bilateral teleoperation system
    • Authors: Ziwei Wang; Zhang Chen; Bin Liang; Bo Zhang
      Pages: 263 - 270
      Abstract: Publication date: March 2018
      Source:Acta Astronautica, Volume 144
      Author(s): Ziwei Wang, Zhang Chen, Bin Liang, Bo Zhang
      Most bilateral teleoperation researches focus on the system stability within time-delays. However, practical teleoperation tasks require high performances besides system stability, such as convergence rate and accuracy. This paper investigates bilateral teleoperation controller design with transient performances. To ensure the transient performances and system stability simultaneously, an adaptive non-singular fast terminal mode controller is proposed to achieve practical finite-time stability considering system uncertainties and time delays. In addition, a novel switching scheme is introduced, in which way the singularity problem of conventional terminal sliding manifold is avoided. Finally, numerical simulations demonstrate the effectiveness and validity of the proposed method.

      PubDate: 2018-02-04T23:09:28Z
      DOI: 10.1016/j.actaastro.2017.12.046
      Issue No: Vol. 144 (2018)
  • Entropy-based adaptive attitude estimation
    • Authors: Maryam Kiani; Aylin Barzegar; Seid H. Pourtakdoust
      Pages: 271 - 282
      Abstract: Publication date: March 2018
      Source:Acta Astronautica, Volume 144
      Author(s): Maryam Kiani, Aylin Barzegar, Seid H. Pourtakdoust
      Gaussian approximation filters have increasingly been developed to enhance the accuracy of attitude estimation in space missions. The effective employment of these algorithms demands accurate knowledge of system dynamics and measurement models, as well as their noise characteristics, which are usually unavailable or unreliable. An innovation-based adaptive filtering approach has been adopted as a solution to this problem; however, it exhibits two major challenges, namely appropriate window size selection and guaranteed assurance of positive definiteness for the estimated noise covariance matrices. The current work presents two novel techniques based on relative entropy and confidence level concepts in order to address the abovementioned drawbacks. The proposed adaptation techniques are applied to two nonlinear state estimation algorithms of the extended Kalman filter and cubature Kalman filter for attitude estimation of a low earth orbit satellite equipped with three-axis magnetometers and Sun sensors. The effectiveness of the proposed adaptation scheme is demonstrated by means of comprehensive sensitivity analysis on the system and environmental parameters by using extensive independent Monte Carlo simulations.

      PubDate: 2018-02-04T23:09:28Z
      DOI: 10.1016/j.actaastro.2017.12.044
      Issue No: Vol. 144 (2018)
  • Trajectory design for a cislunar CubeSat leveraging dynamical systems
           techniques: The Lunar IceCube mission
    • Authors: Natasha Bosanac; Andrew D. Cox; Kathleen C. Howell; David C. Folta
      Pages: 283 - 296
      Abstract: Publication date: March 2018
      Source:Acta Astronautica, Volume 144
      Author(s): Natasha Bosanac, Andrew D. Cox, Kathleen C. Howell, David C. Folta
      Lunar IceCube is a 6U CubeSat that is designed to detect and observe lunar volatiles from a highly inclined orbit. This spacecraft, equipped with a low-thrust engine, is expected to be deployed from the upcoming Exploration Mission-1 vehicle. However, significant uncertainty in the deployment conditions for secondary payloads impacts both the availability and geometry of transfers that deliver the spacecraft to the lunar vicinity. A framework that leverages dynamical systems techniques is applied to a recently updated set of deployment conditions and spacecraft parameter values for the Lunar IceCube mission, demonstrating the capability for rapid trajectory design.

      PubDate: 2018-02-04T23:09:28Z
      DOI: 10.1016/j.actaastro.2017.12.025
      Issue No: Vol. 144 (2018)
  • Plasma brake model for preliminary mission analysis
    • Authors: Leonardo Orsini; Lorenzo Niccolai; Giovanni Mengali; Alessandro A. Quarta
      Pages: 297 - 304
      Abstract: Publication date: March 2018
      Source:Acta Astronautica, Volume 144
      Author(s): Leonardo Orsini, Lorenzo Niccolai, Giovanni Mengali, Alessandro A. Quarta
      Plasma brake is an innovative propellantless propulsion system concept that exploits the Coulomb collisions between a charged tether and the ions in the surrounding environment (typically, the ionosphere) to generate an electrostatic force orthogonal to the tether direction. Previous studies on the plasma brake effect have emphasized the existence of a number of different parameters necessary to obtain an accurate description of the propulsive acceleration from a physical viewpoint. The aim of this work is to discuss an analytical model capable of estimating, with the accuracy required by a preliminary mission analysis, the performance of a spacecraft equipped with a plasma brake in a (near-circular) low Earth orbit. The simplified mathematical model is first validated through numerical simulations, and is then used to evaluate the plasma brake performance in some typical mission scenarios, in order to quantify the influence of the system parameters on the mission performance index.

      PubDate: 2018-02-04T23:09:28Z
      DOI: 10.1016/j.actaastro.2017.12.048
      Issue No: Vol. 144 (2018)
  • Correlation of spacecraft thermal mathematical models to reference data
    • Authors: Ignacio Torralbo; Isabel Perez-Grande; Angel Sanz-Andres; Javier Piqueras
      Pages: 305 - 319
      Abstract: Publication date: March 2018
      Source:Acta Astronautica, Volume 144
      Author(s): Ignacio Torralbo, Isabel Perez-Grande, Angel Sanz-Andres, Javier Piqueras
      Model-to-test correlation is a frequent problem in spacecraft-thermal control design. The idea is to determine the values of the parameters of the thermal mathematical model (TMM) that allows reaching a good fit between the TMM results and test data, in order to reduce the uncertainty of the mathematical model. Quite often, this task is performed manually, mainly because a good engineering knowledge and experience is needed to reach a successful compromise, but the use of a mathematical tool could facilitate this work. The correlation process can be considered as the minimization of the error of the model results with regard to the reference data. In this paper, a simple method is presented suitable to solve the TMM-to-test correlation problem, using Jacobian matrix formulation and Moore-Penrose pseudo-inverse, generalized to include several load cases. Aside, in simple cases, this method also allows for analytical solutions to be obtained, which helps to analyze some problems that appear when the Jacobian matrix is singular. To show the implementation of the method, two problems have been considered, one more academic, and the other one the TMM of an electronic box of PHI instrument of ESA Solar Orbiter mission, to be flown in 2019. The use of singular value decomposition of the Jacobian matrix to analyze and reduce these models is also shown. The error in parameter space is used to assess the quality of the correlation results in both models.

      PubDate: 2018-02-04T23:09:28Z
      DOI: 10.1016/j.actaastro.2017.12.033
      Issue No: Vol. 144 (2018)
  • Effect of surface roughness on the heating rates of large-angled
           hypersonic blunt cones
    • Authors: Kiran Joy Irimpan; Viren Menezes
      Pages: 331 - 338
      Abstract: Publication date: March 2018
      Source:Acta Astronautica, Volume 144
      Author(s): Kiran Joy Irimpan, Viren Menezes
      Surface-roughness caused by the residue of an ablative Thermal Protection System (TPS) can alter the turbulence level and surface heating rates on a hypersonic re-entry capsule. Large-scale surface-roughness that could represent an ablated TPS, was introduced over the forebody of a 120° apex angle blunt cone, in order to test for its influence on surface heating rates in a hypersonic freestream of Mach 8.8. The surface heat transfer rates measured on smooth and roughened models under the same freestream conditions were compared. The hypersonic flow-fields of the smooth and rough-surfaced models were visualized to analyse the flow physics. Qualitative numerical simulations and pressure measurements were carried out to have an insight into the high-speed flow physics. Experimental observations under moderate Reynolds numbers indicated a delayed transition and an overall reduction of 17–46% in surface heating rates on the roughened model.

      PubDate: 2018-02-04T23:09:28Z
      DOI: 10.1016/j.actaastro.2018.01.011
      Issue No: Vol. 144 (2018)
  • Safe-trajectory optimization and tracking control in ultra-close proximity
           to a failed satellite
    • Authors: Jingrui Zhang; Xiaoyu Chu; Yao Zhang; Quan Hu; Guang Zhai; Yanyan Li
      Pages: 339 - 352
      Abstract: Publication date: March 2018
      Source:Acta Astronautica, Volume 144
      Author(s): Jingrui Zhang, Xiaoyu Chu, Yao Zhang, Quan Hu, Guang Zhai, Yanyan Li
      This paper presents a trajectory-optimization method for a chaser spacecraft operating in ultra-close proximity to a failed satellite. Based on the combination of active and passive trajectory protection, the constraints in the optimization framework are formulated for collision avoidance and successful docking in the presence of any thruster failure. The constraints are then handled by an adaptive Gauss pseudospectral method, in which the dynamic residuals are used as the metric to determine the distribution of collocation points. A finite-time feedback control is further employed in tracking the optimized trajectory. In particular, the stability and convergence of the controller are proved. Numerical results are given to demonstrate the effectiveness of the proposed methods.

      PubDate: 2018-02-04T23:09:28Z
      DOI: 10.1016/j.actaastro.2017.12.047
      Issue No: Vol. 144 (2018)
  • Gaseous film cooling investigation in a multi-element splash platelet
    • Authors: Liang Yin; Weiqiang Liu
      Pages: 353 - 362
      Abstract: Publication date: March 2018
      Source:Acta Astronautica, Volume 144
      Author(s): Liang Yin, Weiqiang Liu
      Film cooling is an effective technique that protects chamber walls in rocket combustion against chemical attacks and heat fluxes. This study discusses cooling effect in a multi-element GO2/CH4 splash platelet injector. Influence parameters, such as slot height, slot number, percentage of coolant, and injection position on cooling effect, were investigated. GCH4 with 298.15 K was applied as film coolant. In the first step, slot heights of 0.2 and 0.4 mm were compared by applying a constant film mass flow rate. Temperature, CH4 mole fraction distribution, and flow field structure were obtained. The effects of slot number, percentage of coolant, and injection position on wall temperature distribution were then determined. Finally, the reasons for the low cooling efficiency were analyzed. Improvement in the method is proposed to achieve improved cooling effect for splash platelet injectors.

      PubDate: 2018-02-04T23:09:28Z
      DOI: 10.1016/j.actaastro.2017.12.045
      Issue No: Vol. 144 (2018)
  • Numerical investigations of hybrid rocket engines
    • Authors: V.B. Betelin; A.G. Kushnirenko; N.N. Smirnov; V.F. Nikitin; V.V. Tyurenkova; L.I. Stamov
      Pages: 363 - 370
      Abstract: Publication date: March 2018
      Source:Acta Astronautica, Volume 144
      Author(s): V.B. Betelin, A.G. Kushnirenko, N.N. Smirnov, V.F. Nikitin, V.V. Tyurenkova, L.I. Stamov
      Paper presents the results of numerical studies of hybrid rocket engines operating cycle including unsteady-state transition stage. A mathematical model is developed accounting for the peculiarities of diffusion combustion of fuel in the flow of oxidant, which is composed of oxygen-nitrogen mixture. Three dimensional unsteady-state simulations of chemically reacting gas mixture above thermochemically destructing surface are performed. The results show that the diffusion combustion brings to strongly non-uniform fuel mass regression rate in the flow direction. Diffusive deceleration of chemical reaction brings to the decrease of fuel regression rate in the longitudinal direction.

      PubDate: 2018-02-04T23:09:28Z
      DOI: 10.1016/j.actaastro.2018.01.009
      Issue No: Vol. 144 (2018)
  • Influence of nitrogen source and concentrations on wheat growth and
           production inside “Lunar Palace-1”
    • Authors: Chen Dong; Zhengpei Chu; Minjuan Wang; Youcai Qin; Zhihao Yi; Hong Liu; Yuming Fu
      Pages: 371 - 379
      Abstract: Publication date: March 2018
      Source:Acta Astronautica, Volume 144
      Author(s): Chen Dong, Zhengpei Chu, Minjuan Wang, Youcai Qin, Zhihao Yi, Hong Liu, Yuming Fu
      Minimizing nitrogen (N) consumption and maximizing crop productivity are major challenges to growing plants in Bioregenerative Life Support System (BLSS) for future long-term space mission. Plants cultivated in the controlled environments are sensitive to the low recyclable N (such as from the urine). The purpose of this study is to investigate the effects of nitrogen fertilizer (NH4 +-N and NO3 −-N) disturbance on growth, photosynthetic efficiency, antioxidant defence systems and biomass yield and quality of wheat (Triticum aestivum L.) cultivars during ontogenesis. Experiments were divided into 4 controlled groups,Ⅰ: NO3 −-N: NH4 +-N = 7:1 mmol L−1; Ⅱ: NO3 −-N: NH4 +-N = 14:0.5 mmol L−1; Ⅲ: NO3 −-N: NH4 +-N = 7:0.5 mmol L−1 and CK: NO3 −-N: NH4 +-N = 14:1 mmol L−1, and other salt concentrations were the same. The results showed that heading and flowering stages in spring wheat are sensitive to low N concentration, especially NO3 −-N in group Ⅰ and Ⅲ. NO3 − is better to root growth than to shoot growth. The plants were spindling and the output was lower 21.3% when spring wheat was in low N concentration solution. Meanwhile, photosynthetic rate of low N concentrations is worse than that of CK. The soluble sugar content of the edible part of wheat plants is influenced with NO3 −: NH4 + ratio. In addition, when N concentration was lowest in group Ⅲ, the lignin content decreased to 2.58%, which was more beneficial to recycle substances in the processes of the environment regeneration.

      PubDate: 2018-02-04T23:09:28Z
      DOI: 10.1016/j.actaastro.2017.12.043
      Issue No: Vol. 144 (2018)
  • Requirements for modeling airborne microbial contamination in space
    • Authors: Rob Van Houdt; Eero Kokkonen; Matti Lehtimäki; Pertti Pasanen; Natalie Leys; Ilpo Kulmala
      Pages: 380 - 387
      Abstract: Publication date: March 2018
      Source:Acta Astronautica, Volume 144
      Author(s): Rob Van Houdt, Eero Kokkonen, Matti Lehtimäki, Pertti Pasanen, Natalie Leys, Ilpo Kulmala
      Exposure to bioaerosols is one of the facets that affect indoor air quality, especially for people living in densely populated or confined habitats, and is associated to a wide range of health effects. Good indoor air quality is thus vital and a prerequisite for fully confined environments such as space habitats. Bioaerosols and microbial contamination in these confined space stations can have significant health impacts, considering the unique prevailing conditions and constraints of such habitats. Therefore, biocontamination in space stations is strictly monitored and controlled to ensure crew and mission safety. However, efficient bioaerosol control measures rely on solid understanding and knowledge on how these bioaerosols are created and dispersed, and which factors affect the survivability of the associated microorganisms. Here we review the current knowledge gained from relevant studies in this wide and multidisciplinary area of bioaerosol dispersion modeling and biological indoor air quality control, specifically taking into account the specific space conditions.

      PubDate: 2018-02-04T23:09:28Z
      DOI: 10.1016/j.actaastro.2018.01.004
      Issue No: Vol. 144 (2018)
  • Dynamics and control of three-body tethered system in large elliptic
    • Authors: Gefei Shi; Zhanxia Zhu; Zheng H. Zhu
      Pages: 397 - 404
      Abstract: Publication date: March 2018
      Source:Acta Astronautica, Volume 144
      Author(s): Gefei Shi, Zhanxia Zhu, Zheng H. Zhu
      This paper investigates the dynamic characteristics a three-body tethered satellite system in large elliptic orbits and the control strategy to suppress the libration of the system in orbital transfer process. The system is modeled by a two-piece dumbbell model in the domain of true anomaly. The model consists of one main satellite and two subsatellites connected with two straight, massless and inextensible tethers. Two control strategies based on the sliding mode control are developed to control the libration to the zero state and the steady state respectively. The results of numerical simulations show that the proposed control scheme has good performance in controlling the libration motion of a three-body tethered satellite system in an elliptic orbit with large eccentricity by limited control inputs. Furthermore, Hamiltonians in both states are examined and it shows that less control input is required to control the libration motion to the steady state than that of zero state.

      PubDate: 2018-02-04T23:09:28Z
      DOI: 10.1016/j.actaastro.2018.01.032
      Issue No: Vol. 144 (2018)
  • Determining characteristics of artificial near-Earth objects using
           observability analysis
    • Authors: Alex M. Friedman; Carolin Frueh
      Pages: 405 - 421
      Abstract: Publication date: March 2018
      Source:Acta Astronautica, Volume 144
      Author(s): Alex M. Friedman, Carolin Frueh
      Observability analysis is a method for determining whether a chosen state of a system can be determined from the output or measurements. Knowledge of state information availability resulting from observability analysis leads to improved sensor tasking for observation of orbital debris and better control of active spacecraft. This research performs numerical observability analysis of artificial near-Earth objects. Analysis of linearization methods and state transition matrices is performed to determine the viability of applying linear observability methods to the nonlinear orbit problem. Furthermore, pre-whitening is implemented to reformulate classical observability analysis. In addition, the state in observability analysis is typically composed of position and velocity; however, including object characteristics beyond position and velocity can be crucial for precise orbit propagation. For example, solar radiation pressure has a significant impact on the orbit of high area-to-mass ratio objects in geosynchronous orbit. Therefore, determining the time required for solar radiation pressure parameters to become observable is important for understanding debris objects. In order to compare observability analysis results with and without measurement noise and an extended state, quantitative measures of observability are investigated and implemented.

      PubDate: 2018-02-04T23:09:28Z
      DOI: 10.1016/j.actaastro.2017.12.028
      Issue No: Vol. 144 (2018)
  • Highly miniaturized FEEP propulsion system (NanoFEEP) for attitude and
           orbit control of CubeSats
    • Authors: Daniel Bock; Martin Tajmar
      Pages: 422 - 428
      Abstract: Publication date: March 2018
      Source:Acta Astronautica, Volume 144
      Author(s): Daniel Bock, Martin Tajmar
      A highly miniaturized Field Emission Electric Propulsion (FEEP) system is currently under development at TU Dresden, called NanoFEEP [1]. The highly miniaturized thruster heads are very compact and have a volume of less than 3 cm3 and a weight of less than 6 g each. One thruster is able to generate continuous thrust of up to 8 μN with short term peaks of up to 22 μN. The very compact design and low power consumption (heating power demand between 50 and 150 mW) are achieved by using Gallium as metal propellant with its low melting point of approximately 30 °C. This makes it possible to implement an electric propulsion system consisting of four thruster heads, two neutralizers and the necessary electronics on a 1U CubeSat with its strong limitation in space, weight and available power. Even formation flying of 1U CubeSats using an electric propulsion system is possible with this system, which is shown by the example of a currently planned cooperation project between Wuerzburg University, Zentrum fuer Telematik and TU Dresden. It is planned to use the NanoFEEP electric propulsion system on the UWE (University Wuerzburg Experimental) 1U CubeSat platform [2] to demonstrate orbit and two axis attitude control with our electric propulsion system NanoFEEP. We present the latest performance characteristics of the NanoFEEP thrusters and the highly miniaturized electronics. Additionally, the concept and the current status of a novel cold neutralizer chip using Carbon Nano Tubes (CNTs) is presented.

      PubDate: 2018-02-04T23:09:28Z
      DOI: 10.1016/j.actaastro.2018.01.012
      Issue No: Vol. 144 (2018)
  • Comments on theoretical foundation of “EM Drive”
    • Authors: C.-W.
      Abstract: Publication date: March 2018
      Source:Acta Astronautica, Volume 144
      Author(s): C.-W. Wu
      The concept of EM Drive has attracted much attention and groups of work have been conducted to prove or verify it, of which the published experimental outcome is criticized in great details while the theoretical foundation has not been discussed. The present essay investigates on the theoretical derivations of the net thrust in the “EM drive” and reveals the self-contradiction arising at the very start, when the law of conservation of momentum was utilized and opposed simultaneously.

      PubDate: 2018-02-04T23:09:28Z
  • In-orbit experience and lessons learned from the AVANTI experiment
    • Authors: Gabriella Gaias; Jean-Sébastien Ardaens
      Abstract: Publication date: Available online 4 February 2018
      Source:Acta Astronautica
      Author(s): Gabriella Gaias, Jean-Sébastien Ardaens
      This work addresses flight results and practical challenges of the Autonomous Vision Approach Navigation and Target Identification in-orbit demonstration. This endeavor realized a fully autonomous rendezvous to a noncooperative target in low Earth orbit, in the separation ranges between tens of kilometers to 50 m, relying exclusively on angles-only observations extracted from pictures collected by a monocular, far-range, camera system. By considering experiment commissioning and execution phases, a total of two months of in-orbit experience could be collected, making AVANTI the most authoritative benchmark for designing the first phase of the approach for future active debris removal missions. Accordingly, this work revisits how crucial design decisions revealed decisive to the success of the mission and how they impacted the obtained experiment performances. As conclusion, such lessons learned gained from the flight campaign are reshaped as design guidelines for handing over the peculiar guidance navigation and control system - referred as to AVANTI-concept - to future rendezvous missions.

      PubDate: 2018-02-04T23:09:28Z
      DOI: 10.1016/j.actaastro.2018.01.042
  • Design of relative trajectories for in orbit proximity operations
    • Authors: Roberto Opromolla; Giancarmine Fasano; Giancarlo Rufino; Michele Grassi
      Abstract: Publication date: Available online 3 February 2018
      Source:Acta Astronautica
      Author(s): Roberto Opromolla, Giancarmine Fasano, Giancarlo Rufino, Michele Grassi
      This paper presents an innovative approach to design relative trajectories suitable for close-proximity operations in orbit, by assigning high-level constraints regarding their stability, shape and orientation. Specifically, this work is relevant to space mission scenarios, e.g. formation flying, on-orbit servicing, and active debris removal, which involve either the presence of two spacecraft carrying out coordinated maneuvers, or a servicing/recovery spacecraft (chaser) performing monitoring, rendezvous and docking with respect to another space object (target). In the above-mentioned scenarios, an important aspect is the capability of reducing collision risks and of providing robust and accurate relative navigation solutions. To this aim, the proposed approach exploits a relative motion model relevant to two-satellite formations, and developed in mean orbit parameters, which takes the perturbation effect due to secular Earth oblateness, as well as the motion of the target along a small-eccentricity orbit, into account. This model is used to design trajectories which ensure safe relative motion, to minimize collision risks and relax control requirements, providing at the same time favorable conditions, in terms of target-chaser relative observation geometry for pose determination and relative navigation with passive or active electro-optical sensors on board the chaser. Specifically, three design strategies are proposed in the context of a space target monitoring scenario, considering as design cases both operational spacecraft and debris, characterized by highly variable shape, size and absolute rotational dynamics. The effectiveness of the proposed design approach in providing favorable observation conditions for target-chaser relative pose estimation is demonstrated within a simulation environment which reproduces the designed target-chaser relative trajectory, the operation of an active LIDAR installed on board the chaser, and pose estimation algorithms.

      PubDate: 2018-02-04T23:09:28Z
      DOI: 10.1016/j.actaastro.2018.01.062
  • Prospects of use of electromagnetic railgun as plasma thruster for
    • Authors: S.A. Poniaev; B.I. Reznikov; R.O. Kurakin; P.A. Popov; A.I. Sedov; Y.A. Shustrov; B.G. Zhukov
      Abstract: Publication date: Available online 3 February 2018
      Source:Acta Astronautica
      Author(s): S.A. Poniaev, B.I. Reznikov, R.O. Kurakin, P.A. Popov, A.I. Sedov, Y.A. Shustrov, B.G. Zhukov
      Estimation of a possibility to use an electromagnetic plasma railgun as a safe and reliable plasma thruster based on calculations of the thrust force and specific impulse of a plasma jet flowing from an accelerator channel is presented. Theoretical and experimental investigations of acceleration of a plasma armature in railguns filled with inert gases (helium, argon, xenon) carried out at Ioffe Institute are described.

      PubDate: 2018-02-04T23:09:28Z
      DOI: 10.1016/j.actaastro.2017.12.035
  • Effects of spray angle variation on mixing in a cold supersonic combustor
           with kerosene fuel
    • Authors: Lin Zhu; Feng Luo; Yin-Yin Qi; Min Wei; Jia-Ru Ge; Wei-Lai Liu; Guo-Li Li; Tien-Chien Jen
      Pages: 1 - 11
      Abstract: Publication date: March 2018
      Source:Acta Astronautica, Volume 144
      Author(s): Lin Zhu, Feng Luo, Yin-Yin Qi, Min Wei, Jia-Ru Ge, Wei-Lai Liu, Guo-Li Li, Tien-Chien Jen
      Effective fuel injection and mixing is of particular importance for scramjet engines to be operated reliably because the fuel must be injected into high-speed crossflow and mixed with the supersonic air at an extremely short time-scale. This study numerically characterizes an injection jet under different spray angles in a cold kerosene-fueled supersonic flow and thus assesses the effects of the spray angle on the mixing between incident shock wave and transverse cavity injection. A detailed computational fluid dynamics model is developed in accordance with the real scramjet combustor. Next, the spray angles are designated as 45°, 90°, and 135° respectively with the other constant operational conditions (such as the injection diameter, velocity and pressure). Next, a combination of a three dimensional Couple Level Set & Volume of Fluids with an improved Kelvin-Helmholtz & Rayleigh-Taylor model is used to investigate the interaction between kerosene and supersonic air. The numerical predictions are focused on penetration depth, span expansion area, angle of shock wave and sauter mean diameter distribution of the kerosene droplets with or without evaporation. Finally, validation has been implemented by comparing the calculated to the measured in literature with good qualitative agreement. Results show that no matter whether the evaporation is considered, the penetration depth, span-wise angle and expansion area of the kerosene droplets are all increased with the spray angle, and most especially, that the size of the kerosene droplets is surely reduced with the spray angle increase. These calculations are beneficial to better understand the underlying atomization mechanism in the cold kerosene-fueled supersonic flow and hence provide insights into scramjet design improvement.

      PubDate: 2017-12-13T06:26:39Z
      DOI: 10.1016/j.actaastro.2017.12.013
      Issue No: Vol. 144 (2017)
  • Characterization of ignition transient processes in kerosene-fueled model
           scramjet engine by dual-pulse laser-induced plasma
    • Authors: Xipeng Li; Weidong Liu; Yu Pan; Leichao Yang; Bin An; Jiajian Zhu
      Pages: 23 - 29
      Abstract: Publication date: March 2018
      Source:Acta Astronautica, Volume 144
      Author(s): Xipeng Li, Weidong Liu, Yu Pan, Leichao Yang, Bin An, Jiajian Zhu
      Dual-pulse laser-induced plasma ignition of kerosene in cavity at model scramjet engine is studied. The simulated flight condition is Ma 6 at 30 km, and the isolator entrance has a Mach number of 2.92, a total pressure of 2.6 MPa and a stagnation temperature of 1650 K. Two independent laser pulses at 532 nm with a pulse width of 10 ns, a diameter of 12 mm and a maximum energy of 300 mJ are focused into cavity for ignition. The flame structure and propagation during transient ignition processes are captured by simultaneous CH* and OH* chemiluminescence imaging. The entire ignition process of kerosene can be divided into five stages, which are referred as turbulent dissipation stage, quasi-stable state, combustion enhancement stage, reverting stage and combustion stabilization stage. A local closed loop of propagations of the burning mixtures from the shear layer into the recirculation zone of cavity is revealed, which the large-scale eddy in the shear layer plays a key role. The enhancement of mass exchange between shear layer and the recirculation zone of cavity could promote the flame propagation process and enhance the ignition capability as well as extend the ignition limits. A cavity shear-layer stabilized combustion of kerosene is established in the supersonic flow roughly 3.3 ms after the laser pulse. Chemical reactions mainly occur in the shear layer and the near-wall zone downstream of the cavity. The distribution of OH* is thicker than CH* at stable combustion condition.

      PubDate: 2017-12-27T03:42:51Z
      DOI: 10.1016/j.actaastro.2017.12.018
      Issue No: Vol. 144 (2017)
  • Detailed experimental investigations on flow behaviors and velocity field
           properties of a supersonic mixing layer
    • Authors: Jianguo Tan; Dongdong Zhang; Hao Li; Juwei Hou
      Pages: 30 - 38
      Abstract: Publication date: March 2018
      Source:Acta Astronautica, Volume 144
      Author(s): Jianguo Tan, Dongdong Zhang, Hao Li, Juwei Hou
      The flow behaviors and mixing characteristics of a supersonic mixing layer with a convective Mach number of 0.2 have been experimentally investigated utilizing nanoparticle-based planar laser scattering and particle image velocimetry techniques. The full development and evolution process, including the formation of Kelvin-Helmholtz vortices, breakdown of large-scale structures and establishment of self-similar turbulence, is exhibited clearly in the experiments, which can give a qualitative graphically comparing for the DNS and LES results. The shocklets are first captured at this low convective Mach number, and their generation mechanisms are elaborated and analyzed. The convective velocity derived from two images with space-time correlations is well consistent with the theoretical result. The pairing and merging process of large-scale vortices in transition region is clearly revealed in the velocity vector field. The analysis of turbulent statistics indicates that in weakly compressible mixing layers, with the increase of convective Mach number, the peak values of streamwise turbulence intensity and Reynolds shear stress experience a sharp decrease, while the anisotropy ratio seems to keep quasi unchanged. The normalized growth rate of the present experiments shows a well agreement with former experimental and DNS data. The validation of present experimental results is important for that in the future the present work can be a reference for assessing the accuracy of numerical data.

      PubDate: 2017-12-27T03:42:51Z
      DOI: 10.1016/j.actaastro.2017.12.010
      Issue No: Vol. 144 (2017)
  • Feedback slew algorithms for prolate spinners using Single–Thruster
    • Authors: Juntian Si; Yang Gao; Abadi Chanik
      Pages: 39 - 51
      Abstract: Publication date: March 2018
      Source:Acta Astronautica, Volume 144
      Author(s): Juntian Si, Yang Gao, Abadi Chanik
      A number of low-cost open-loop slew control algorithms have been developed for prolate spinning spacecraft using single-thruster actuation. Robustness analysis indicates that these algorithms have high sensitiveness over thruster firing time error, spacecraft inertia error, and especially spin rate perturbations. This paper proposed two novel feedback slew algorithms, Feedback Half-Cone and Feedback Sector-Arc Slew, built on the existing open-loop algorithms and they use attitude and angular velocity feedback to compensate the errors in knowledge of spin rate, without external torques. As presented, after the first thruster actuation initiate the spin-axis precession, the feedback slew algorithms take attitude and spin-rate feedback to estimate the angular momentum and predict the spin-axis attitude during the slew. These techniques contribute to improve the cancelation thrust impulse accuracy and reduce the final nutation error. Simulations for a Penetrator mission scenario validate these feedback algorithms and show their slew performance and robustness over the perturbations mentioned above. It is proved that the attitude feedback greatly improves the slew accuracy and robustness.

      PubDate: 2017-12-27T03:42:51Z
      DOI: 10.1016/j.actaastro.2017.11.044
      Issue No: Vol. 144 (2017)
  • Reliable spacecraft rendezvous without velocity measurement
    • Authors: Shaoming He; Defu Lin
      Pages: 52 - 60
      Abstract: Publication date: March 2018
      Source:Acta Astronautica, Volume 144
      Author(s): Shaoming He, Defu Lin
      This paper investigates the problem of finite-time velocity-free autonomous rendezvous for spacecraft in the presence of external disturbances during the terminal phase. First of all, to address the problem of lack of relative velocity measurement, a robust observer is proposed to estimate the unknown relative velocity information in a finite time. It is shown that the effect of external disturbances on the estimation precision can be suppressed to a relatively low level. With the reconstructed velocity information, a finite-time output feedback control law is then formulated to stabilize the rendezvous system. Theoretical analysis and rigorous proof show that the relative position and its rate can converge to a small compacted region in finite time. Numerical simulations are performed to evaluate the performance of the proposed approach in the presence of external disturbances and actuator faults.

      PubDate: 2017-12-27T03:42:51Z
      DOI: 10.1016/j.actaastro.2017.12.016
      Issue No: Vol. 144 (2017)
  • Spacecraft reorientation control in presence of attitude constraint
           considering input saturation and stochastic disturbance
    • Authors: Yu Cheng; Dong Ye; Zhaowei Sun; Shijie Zhang
      Pages: 61 - 68
      Abstract: Publication date: March 2018
      Source:Acta Astronautica, Volume 144
      Author(s): Yu Cheng, Dong Ye, Zhaowei Sun, Shijie Zhang
      This paper proposes a novel feedback control law for spacecraft to deal with attitude constraint, input saturation, and stochastic disturbance during the attitude reorientation maneuver process. Applying the parameter selection method to improving the existence conditions for the repulsive potential function, the universality of the potential-function-based algorithm is enhanced. Moreover, utilizing the auxiliary system driven by the difference between saturated torque and command torque, a backstepping control law, which satisfies the input saturation constraint and guarantees the spacecraft stability, is presented. Unlike some methods that passively rely on the inherent characteristic of the existing controller to stabilize the adverse effects of external stochastic disturbance, this paper puts forward a nonlinear disturbance observer to compensate the disturbance in real-time, which achieves a better performance of robustness. The simulation results validate the effectiveness, reliability, and universality of the proposed control law.

      PubDate: 2017-12-27T03:42:51Z
      DOI: 10.1016/j.actaastro.2017.12.002
      Issue No: Vol. 144 (2017)
  • Value-centric design architecture based on analysis of space system
    • Authors: Q. Xu; P. Hollingsworth; K. Smith
      Pages: 69 - 79
      Abstract: Publication date: March 2018
      Source:Acta Astronautica, Volume 144
      Author(s): Q. Xu, P. Hollingsworth, K. Smith
      Emerging design concepts such as miniaturisation, modularity, and standardisation, have contributed to the rapid development of small and inexpensive platforms, particularly cubesats. This has been stimulating an upcoming revolution in space design and development, leading satellites into the era of “smaller, faster, and cheaper”. However, the current requirement-centric design philosophy, focused on bespoke monolithic systems, along with the associated development and production process does not inherently fit with the innovative modular, standardised, and mass-produced technologies. This paper presents a new categorisation, characterisation, and value-centric design architecture to address this need for both traditional and novel system designs. Based on the categorisation of system configurations, a characterisation of space systems, comprised of duplication, fractionation, and derivation, is proposed to capture the overall system configuration characteristics and promote potential hybrid designs. Complying with the definitions of the system characterisation, mathematical mapping relations between the system characterisation and the system properties are described to establish the mathematical foundation of the proposed value-centric design methodology. To illustrate the methodology, subsystem reliability relationships are therefore analysed to explore potential system configurations in the design space. The results of the applications of system characteristic analysis clearly show that the effects of different configuration characteristics on the system properties can be effectively analysed and evaluated, enabling the optimization of system configurations.

      PubDate: 2017-12-27T03:42:51Z
      DOI: 10.1016/j.actaastro.2017.12.017
      Issue No: Vol. 144 (2017)
  • Design optimization of dual-axis driving mechanism for satellite antenna
           with two planar revolute clearance joints
    • Authors: Zheng Feng Bai; Ji Jun Zhao; Jun Chen; Yang Zhao
      Pages: 80 - 89
      Abstract: Publication date: March 2018
      Source:Acta Astronautica, Volume 144
      Author(s): Zheng Feng Bai, Ji Jun Zhao, Jun Chen, Yang Zhao
      In the dynamic analysis of satellite antenna dual-axis driving mechanism, it is usually assumed that the joints are ideal or perfect without clearances. However, in reality, clearances in joints are unavoidable due to assemblage, manufacturing errors and wear. When clearance is introduced to the mechanism, it will lead to poor dynamic performances and undesirable vibrations due to impact forces in clearance joint. In this paper, a design optimization method is presented to reduce the undesirable vibrations of satellite antenna considering clearance joints in dual-axis driving mechanism. The contact force model in clearance joint is established using a nonlinear spring-damper model and the friction effect is considered using a modified Coulomb friction model. Firstly, the effects of clearances on dynamic responses of satellite antenna are investigated. Then the optimization method for dynamic design of the dual-axis driving mechanism with clearance is presented. The objective of the optimization is to minimize the maximum absolute vibration peak of antenna acceleration by reducing the impact forces in clearance joint. The main consideration here is to optimize the contact parameters of the joint elements. The contact stiffness coefficient, damping coefficient and the dynamic friction coefficient for clearance joint elements are taken as the optimization variables. A Generalized Reduced Gradient (GRG) algorithm is used to solve this highly nonlinear optimization problem for dual-axis driving mechanism with clearance joints. The results show that the acceleration peaks of satellite antenna and contact forces in clearance joints are reduced obviously after design optimization, which contributes to a better performance of the satellite antenna. Also, the application and limitation of the proposed optimization method are discussed.

      PubDate: 2017-12-27T03:42:51Z
      DOI: 10.1016/j.actaastro.2017.11.015
      Issue No: Vol. 144 (2017)
  • Thermal protection performance of opposing jet generating with solid fuel
    • Authors: Binxian Shen; Weiqiang Liu
      Pages: 90 - 96
      Abstract: Publication date: March 2018
      Source:Acta Astronautica, Volume 144
      Author(s): Binxian Shen, Weiqiang Liu
      A light and small gas supply device, which uses fuel gas generating with solid fuel as coolant gas, is introduced for opposing jet thermal protection in hypersonic vehicles. A numerical study on heat flux reduction in hypersonic flow with opposing jet is conducted to investigate the cooling efficiency of fuel gas. Flow field and cooling efficiency at different jet temperatures, as well as the effect of fuel gas, are determined. Detailed results show that shock stand-off distance changes with an increase in jet pressure ratio and remains constant with an increase in jet temperature. Cooling efficiency weakens with an increase in jet temperature and can be strengthened by enhancing jet pressure. Lastly, a remarkable heat flux reduction is observed with fuel gas injection with respect to no fuel gas injection when jet temperature reaches 900 K, thereby proving the positive cooling efficiency of fuel gas.

      PubDate: 2017-12-27T03:42:51Z
      DOI: 10.1016/j.actaastro.2017.12.024
      Issue No: Vol. 144 (2017)
  • A voting-based star identification algorithm utilizing local and global
    • Authors: Qiaoyun Fan; Xuyang Zhong; Junhua Sun
      Pages: 126 - 135
      Abstract: Publication date: March 2018
      Source:Acta Astronautica, Volume 144
      Author(s): Qiaoyun Fan, Xuyang Zhong, Junhua Sun
      A novel star identification algorithm based on voting scheme is presented in this paper. In the proposed algorithm, the global distribution and local distribution of sensor stars are fully utilized, and the stratified voting scheme is adopted to obtain the candidates for sensor stars. The database optimization is employed to reduce its memory requirement and improve the robustness of the proposed algorithm. The simulation shows that the proposed algorithm exhibits 99.81% identification rate with 2-pixel standard deviations of positional noises and 0.322-Mv magnitude noises. Compared with two similar algorithms, the proposed algorithm is more robust towards noise, and the average identification time and required memory is less. Furthermore, the real sky test shows that the proposed algorithm performs well on the real star images.

      PubDate: 2017-12-27T03:42:51Z
      DOI: 10.1016/j.actaastro.2017.12.003
      Issue No: Vol. 144 (2017)
  • Cryo-braking using penetrators for enhanced capabilities for the potential
           landing of payloads on icy solar system objects
    • Authors: R.M. Winglee; T. Robinson; M. Danner; J. Koch
      Pages: 136 - 146
      Abstract: Publication date: March 2018
      Source:Acta Astronautica, Volume 144
      Author(s): R.M. Winglee, T. Robinson, M. Danner, J. Koch
      The icy moons of Jupiter and Saturn are important astrobiology targets. Access to the surface of these worlds is made difficult by the high ΔV requirements which is typically in the hypervelocity range. Passive braking systems cannot be used due to the lack of an atmosphere, and active braking by rockets significantly adds to the missions costs. This paper demonstrates that a two-stage landing system can overcome these problems and provide significant improvements in the payload fraction that can be landed The first stage involves a hypervelocity impactor which is designed to penetrate to a depth of a few tens of meters. This interaction is the cryo-breaking component and is examined through laboratory experiments, empirical relations and modeling. The resultant ice-particle cloud creates a transient artificial atmosphere that can be used to enable passive braking of the second stage payload dd, with a substantially higher mass payload fraction than possible with a rocket landing system. It is shown that a hollow cylinder design for the impactor can more efficiently eject the material upwards in a solid cone of ice particles relative to solid impactors such as spheres or spikes. The ejected mass is shown to be of the order of 103 to 104 times the mass of the impactor. The modeling indicates that a 10 kg payload with a braking system of 3 m2 (i.e. an areal density of 0.3 kg/m2) is sufficient to allow the landing of the payload with the deceleration limited to less than 2000 g's. Modern electronics can withstand this deceleration and as such the system provides an important alternative to landing payloads on icy solar system objects.

      PubDate: 2017-12-27T03:42:51Z
      DOI: 10.1016/j.actaastro.2017.12.019
      Issue No: Vol. 144 (2017)
  • Experimental investigation of atomization characteristics of swirling
           spray by ADN gelled propellant
    • Authors: Hao-Sen Guan; Guo-Xiu Li; Nai-Yuan Zhang
      Abstract: Publication date: Available online 12 December 2017
      Source:Acta Astronautica
      Author(s): Hao-Sen Guan, Guo-Xiu Li, Nai-Yuan Zhang
      Due to the current global energy shortage and increasingly serious environmental issues, green propellants are attracting more attention. In particular, the ammonium dinitramide (ADN)-based monopropellant thruster is gaining world-wide attention as a green, non-polluting and high specific impulse propellant. Gel propellants combine the advantages of liquid and solid propellants, and are becoming popular in the field of spaceflight. In this paper, a swirling atomization experimental study was carried out using an ADN aqueous gel propellant under different injection pressures. A high-speed camera and a Malvern laser particle size analyzer were used to study the spray process. The flow coefficient, cone angle of swirl atomizing spray, breakup length of spray membrane, and droplet size distribution were analyzed. Furthermore, the effects of different injection pressures on the swirling atomization characteristics were studied.

      PubDate: 2017-12-13T06:26:39Z
      DOI: 10.1016/j.actaastro.2017.12.015
  • Integral design method for simple and small Mars lander system using
           membrane aeroshell
    • Authors: Ryo Sakagami; Ryohei Takahashi; Akifumi Wachi; Yuki Koshiro; Hiroyuki Maezawa; Yasko Kasai; Shinichi Nakasuka
      Abstract: Publication date: Available online 12 December 2017
      Source:Acta Astronautica
      Author(s): Ryo Sakagami, Ryohei Takahashi, Akifumi Wachi, Yuki Koshiro, Hiroyuki Maezawa, Yasko Kasai, Shinichi Nakasuka
      To execute Mars surface exploration missions, spacecraft need to overcome the difficulties of the Mars entry, descent, and landing (EDL) sequences. Previous landing missions overcame these challenges with complicated systems that could only be executed by organizations with mature technology and abundant financial resources. In this paper, we propose a novel integral design methodology for a small, simple Mars lander that is achievable even by organizations with limited technology and resources such as universities or emerging countries. We aim to design a lander (including its interplanetary cruise stage) whose size and mass are under 1 m3 and 150 kg, respectively. We adopted only two components for Mars EDL process: a “membrane aeroshell” for the Mars atmospheric entry and descent sequence and one additional mechanism for the landing sequence. The landing mechanism was selected from the following three candidates: (1) solid thrusters, (2) aluminum foam, and (3) a vented airbag. We present a reasonable design process, visualize dependencies among parameters, summarize sizing methods for each component, and propose the way to integrate these components into one system. To demonstrate the effectiveness, we applied this methodology to the actual Mars EDL mission led by the National Institute of Information and Communications Technology (NICT) and the University of Tokyo. As a result, an 80 kg class Mars lander with a 1.75 m radius membrane aeroshell and a vented airbag was designed, and the maximum landing shock that the lander will receive was 115 G.

      PubDate: 2017-12-13T06:26:39Z
      DOI: 10.1016/j.actaastro.2017.11.024
  • Probability-based hazard avoidance guidance for planetary landing
    • Authors: Xu Yuan; Zhengshi Yu; Pingyuan Cui; Xu Rui; Shengying Zhu; Menglong Cao; Enjie Luan
      Abstract: Publication date: Available online 9 December 2017
      Source:Acta Astronautica
      Author(s): Xu Yuan, Zhengshi Yu, Pingyuan Cui, Xu Rui, Shengying Zhu, Menglong Cao, Enjie Luan
      Future landing and sample return missions on planets and small bodies will seek landing sites with high scientific value, which may be located in hazardous terrains. Autonomous landing in such hazardous terrains and highly uncertain planetary environments is particularly challenging. Onboard hazard avoidance ability is indispensable, and the algorithms must be robust to uncertainties. In this paper, a novel probability-based hazard avoidance guidance method is developed for landing in hazardous terrains on planets or small bodies. By regarding the lander state as probabilistic, the proposed guidance algorithm exploits information on the uncertainty of lander position and calculates the probability of collision with each hazard. The collision probability serves as an accurate safety index, which quantifies the impact of uncertainties on the lander safety. Based on the collision probability evaluation, the state uncertainty of the lander is explicitly taken into account in the derivation of the hazard avoidance guidance law, which contributes to enhancing the robustness to the uncertain dynamics of planetary landing. The proposed probability-based method derives fully analytic expressions and does not require off-line trajectory generation. Therefore, it is appropriate for real-time implementation. The performance of the probability-based guidance law is investigated via a set of simulations, and the effectiveness and robustness under uncertainties are demonstrated.

      PubDate: 2017-12-13T06:26:39Z
      DOI: 10.1016/j.actaastro.2017.11.039
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