for Journals by Title or ISSN
for Articles by Keywords

Publisher: Elsevier   (Total: 3118 journals)

 A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z  

        1 2 3 4 5 6 7 8 | Last   [Sort by number of followers]   [Restore default list]

Showing 1 - 200 of 3118 Journals sorted alphabetically
A Practical Logic of Cognitive Systems     Full-text available via subscription   (Followers: 7)
AASRI Procedia     Open Access   (Followers: 15)
Academic Pediatrics     Hybrid Journal   (Followers: 25, SJR: 1.402, h-index: 51)
Academic Radiology     Hybrid Journal   (Followers: 22, SJR: 1.008, h-index: 75)
Accident Analysis & Prevention     Partially Free   (Followers: 89, 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: 371, SJR: 0.726, h-index: 43)
Acta Automatica Sinica     Full-text available via subscription   (Followers: 3)
Acta Biomaterialia     Hybrid Journal   (Followers: 27, 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: 235, 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: 6)
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: 136, 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: 3)
Advances in Applied Mathematics     Full-text available via subscription   (Followers: 6, SJR: 1.054, h-index: 35)
Advances in Applied Mechanics     Full-text available via subscription   (Followers: 11, SJR: 0.801, h-index: 26)
Advances in Applied Microbiology     Full-text available via subscription   (Followers: 22, SJR: 1.286, h-index: 49)
Advances In Atomic, Molecular, and Optical Physics     Full-text available via subscription   (Followers: 16, SJR: 3.31, h-index: 42)
Advances in Biological Regulation     Hybrid Journal   (Followers: 4, SJR: 2.277, h-index: 43)
Advances in Botanical Research     Full-text available via subscription   (Followers: 3, SJR: 0.619, h-index: 48)
Advances in Cancer Research     Full-text available via subscription   (Followers: 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: 5, 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: 22)
Advances in Ecological Research     Full-text available via subscription   (Followers: 46, SJR: 3.25, h-index: 43)
Advances in Engineering Software     Hybrid Journal   (Followers: 26, SJR: 0.486, h-index: 10)
Advances in Experimental Biology     Full-text available via subscription   (Followers: 8)
Advances in Experimental Social Psychology     Full-text available via subscription   (Followers: 44, SJR: 5.465, h-index: 64)
Advances in Exploration Geophysics     Full-text available via subscription   (Followers: 3)
Advances in Fluorine Science     Full-text available via subscription   (Followers: 8)
Advances in Food and Nutrition Research     Full-text available via subscription   (Followers: 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: 15, SJR: 2.558, h-index: 54)
Advances in Genome Biology     Full-text available via subscription   (Followers: 11)
Advances in Geophysics     Full-text available via subscription   (Followers: 6, SJR: 2.325, h-index: 20)
Advances in Heat Transfer     Full-text available via subscription   (Followers: 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: 26)
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: 9)
Advances in Marine Biology     Full-text available via subscription   (Followers: 16, SJR: 1.645, h-index: 45)
Advances in Mathematics     Full-text available via subscription   (Followers: 10, SJR: 3.261, h-index: 65)
Advances in Medical Sciences     Hybrid Journal   (Followers: 6, SJR: 0.489, h-index: 25)
Advances in Medicinal Chemistry     Full-text available via subscription   (Followers: 5)
Advances in Microbial Physiology     Full-text available via subscription   (Followers: 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: 3)
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: 15, SJR: 1.718, h-index: 58)
Advances in Physical Organic Chemistry     Full-text available via subscription   (Followers: 8, SJR: 0.384, h-index: 26)
Advances in Phytomedicine     Full-text available via subscription  
Advances in Planar Lipid Bilayers and Liposomes     Full-text available via subscription   (Followers: 3, SJR: 0.248, h-index: 11)
Advances in Plant Biochemistry and Molecular Biology     Full-text available via subscription   (Followers: 8)
Advances in Plant Pathology     Full-text available via subscription   (Followers: 5)
Advances in Porous Media     Full-text available via subscription   (Followers: 4)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 18)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 20, SJR: 1.5, h-index: 62)
Advances in Psychology     Full-text available via subscription   (Followers: 62)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 5, SJR: 0.478, h-index: 32)
Advances in Radiation Oncology     Open Access  
Advances in Small Animal Medicine and Surgery     Hybrid Journal   (Followers: 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: 366, 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: 8, 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: 334, SJR: 0.816, h-index: 49)
AEU - Intl. J. of Electronics and Communications     Hybrid Journal   (Followers: 8, SJR: 0.318, h-index: 36)
African J. of Emergency Medicine     Open Access   (Followers: 5, SJR: 0.344, h-index: 6)
Ageing Research Reviews     Hybrid Journal   (Followers: 9, SJR: 3.289, h-index: 78)
Aggression and Violent Behavior     Hybrid Journal   (Followers: 446, 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: 41, 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: 8, SJR: 2.05, h-index: 20)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 3)
Allergologia et Immunopathologia     Full-text available via subscription   (Followers: 1, SJR: 0.46, h-index: 29)
Allergology Intl.     Open Access   (Followers: 4, SJR: 0.776, h-index: 35)
Alpha Omegan     Full-text available via subscription   (SJR: 0.121, h-index: 9)
ALTER - European J. of Disability Research / Revue Européenne de Recherche sur le Handicap     Full-text available via subscription   (Followers: 9, SJR: 0.158, h-index: 9)
Alzheimer's & Dementia     Hybrid Journal   (Followers: 48, SJR: 4.289, h-index: 64)
Alzheimer's & Dementia: Diagnosis, Assessment & Disease Monitoring     Open Access   (Followers: 4)
Alzheimer's & Dementia: Translational Research & Clinical Interventions     Open Access   (Followers: 4)
Ambulatory Pediatrics     Hybrid Journal   (Followers: 5)
American Heart J.     Hybrid Journal   (Followers: 49, 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: 41, 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: 46, SJR: 2.023, h-index: 189)
American J. of Medicine Supplements     Full-text available via subscription   (Followers: 3)
American J. of Obstetrics and Gynecology     Hybrid Journal   (Followers: 201, SJR: 2.255, h-index: 171)
American J. of Ophthalmology     Hybrid Journal   (Followers: 60, 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: 35, 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: 59, SJR: 0.124, h-index: 9)
Anaesthesia Critical Care & Pain Medicine     Full-text available via subscription   (Followers: 13)
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: 164, 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  

        1 2 3 4 5 6 7 8 | Last   [Sort by number of followers]   [Restore default list]

Journal Cover Acta Astronautica
  [SJR: 0.726]   [H-I: 43]   [371 followers]  Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0094-5765
   Published by Elsevier Homepage  [3118 journals]
  • 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)
  • Sintering of micro-trusses created by extrusion-3D-printing of lunar
           regolith inks
    • Authors: Shannon L. Taylor; Adam E. Jakus; Katie D. Koube; Amaka J. Ibeh; Nicholas R. Geisendorfer; Ramille N. Shah; David C. Dunand
      Pages: 1 - 8
      Abstract: Publication date: February 2018
      Source:Acta Astronautica, Volume 143
      Author(s): Shannon L. Taylor, Adam E. Jakus, Katie D. Koube, Amaka J. Ibeh, Nicholas R. Geisendorfer, Ramille N. Shah, David C. Dunand
      The development of in situ fabrication methods for the infrastructure required to support human life on the Moon is necessary due to the prohibitive cost of transporting large quantities of materials from the Earth. Cellular structures, consisting of a regular network (truss) of micro-struts with ∼500 μm diameters, suitable for bricks, blocks, panels, and other load-bearing structural elements for habitats and other infrastructure are created by direct-extrusion 3D-printing of liquid inks containing JSC-1A lunar regolith simulant powders, followed by sintering. The effects of sintering time, temperature, and atmosphere (air or hydrogen) on the microstructures, mechanical properties, and magnetic properties of the sintered lunar regolith micro-trusses are investigated. The air-sintered micro-trusses have higher relative densities, linear shrinkages, and peak compressive strengths, due to the improved sintering of the struts within the micro-trusses achieved by a liquid or glassy phase. Whereas the hydrogen-sintered micro-trusses show no liquid-phase sintering or glassy phase, they contain metallic iron 0.1–2 μm particles from the reduction of ilmenite, which allows them to be lifted with magnets.

      PubDate: 2017-11-24T17:46:02Z
      DOI: 10.1016/j.actaastro.2017.11.005
      Issue No: Vol. 143 (2017)
  • Spherical gyroscopic moment stabilizer for attitude control of
    • Authors: Sajjad Keshtkar; Jaime A. Moreno; Hirohisa Kojima; Kenji Uchiyama; Masahiro Nohmi; Keisuke Takaya
      Pages: 9 - 15
      Abstract: Publication date: February 2018
      Source:Acta Astronautica, Volume 143
      Author(s): Sajjad Keshtkar, Jaime A. Moreno, Hirohisa Kojima, Kenji Uchiyama, Masahiro Nohmi, Keisuke Takaya
      This paper presents a new and improved concept of recently proposed two-degrees of freedom spherical stabilizer for triaxial orientation of microsatellites. The analytical analysis of the advantages of the proposed mechanism over the existing inertial attitude control devices are introduced. The extended equations of motion of the stabilizing satellite including the spherical gyroscope, for control law design and numerical simulations, are studied in detail. A new control algorithm based on continuous high-order sliding mode algorithms, for managing the torque produced by the stabilizer and therefore the attitude control of the satellite in the presence of perturbations/uncertainties, is presented. Some numerical simulations are carried out to prove the performance of the proposed mechanism and control laws.

      PubDate: 2017-11-24T17:46:02Z
      DOI: 10.1016/j.actaastro.2017.10.033
      Issue No: Vol. 143 (2017)
  • Trajectory design for Saturnian Ocean Worlds orbiters using
           multidimensional Poincaré maps
    • Authors: Diane Craig Davis; Sean M. Phillips; Brian P. McCarthy
      Pages: 16 - 28
      Abstract: Publication date: February 2018
      Source:Acta Astronautica, Volume 143
      Author(s): Diane Craig Davis, Sean M. Phillips, Brian P. McCarthy
      Missions based on low-energy orbits in the vicinity of planetary moons, such as Titan or Enceladus, involve significant end-to-end trajectory design challenges due to the gravitational effects of the distant larger primary. To address these challenges, the current investigation focuses on the visualization and use of multidimensional Poincaré maps to perform preliminary design of orbits with significant out-of-plane components, including orbits that provide polar coverage. Poincaré maps facilitate the identification of families of solutions to a given orbit problem and provide the ability to easily respond to changing inputs and requirements. A visual-based design process highlights a variety of trajectory options near Saturn's ocean worlds, including both moon-centered orbits and libration point orbits.

      PubDate: 2017-11-24T17:46:02Z
      DOI: 10.1016/j.actaastro.2017.11.004
      Issue No: Vol. 143 (2017)
  • Onboard guidance system design for reusable launch vehicles in the
           terminal area energy management phase
    • Authors: Lingxia Mu; Xiang Yu; Y.M. Zhang; Ping Li; Xinmin Wang
      Pages: 62 - 75
      Abstract: Publication date: February 2018
      Source:Acta Astronautica, Volume 143
      Author(s): Lingxia Mu, Xiang Yu, Y.M. Zhang, Ping Li, Xinmin Wang
      A terminal area energy management (TAEM) guidance system for an unpowered reusable launch vehicle (RLV) is proposed in this paper. The mathematical model representing the RLV gliding motion is provided, followed by a transformation of extracting the required dynamics for reference profile generation. Reference longitudinal profiles are conceived based on the capability of maximum dive and maximum glide that a RLV can perform. The trajectory is obtained by iterating the motion equations at each node of altitude, where the angle of attack and the flight-path angle are regarded as regulating variables. An onboard ground-track predictor is constructed to generate the current range-to-go and lateral commands online. Although the longitudinal profile generation requires pre-processing using the RLV aerodynamics, the ground-track prediction can be executed online. This makes the guidance scheme adaptable to abnormal conditions. Finally, the guidance law is designed to track the reference commands. Numerical simulations demonstrate that the proposed guidance scheme is capable of guiding the RLV to the desired touchdown conditions.

      PubDate: 2017-12-27T03:42:51Z
      DOI: 10.1016/j.actaastro.2017.10.027
      Issue No: Vol. 143 (2017)
  • Meteorite as raw material for Direct Metal Printing: A proof of concept
    • Authors: Karel Lietaert; Lore Thijs; Bram Neirinck; Thomas Lapauw; Brian Morrison; Chris Lewicki; Jonas Van Vaerenbergh
      Pages: 76 - 81
      Abstract: Publication date: February 2018
      Source:Acta Astronautica, Volume 143
      Author(s): Karel Lietaert, Lore Thijs, Bram Neirinck, Thomas Lapauw, Brian Morrison, Chris Lewicki, Jonas Van Vaerenbergh
      Asteroid mining as such is not a new concept, as it has been described in science fiction for more than a century and some of its aspects have been studied by academia for more than 30 years. Recently, there is a renewed interest in this subject due the more and more concrete plans for long-duration space missions and the need for resources to support industrial activity in space. The use of locally available resources would greatly improve the economics and sustainability of such missions. Due to its economy in material, use of additive manufacturing (AM) provides an interesting route to valorize these resources for the production of spare parts, tools and large-scale structures optimized for their local microgravity environment. Proof of concept has already been provided for AM of moon regolith. In this paper the concept of In-Situ Resource Utilization is extended towards the production of metallic objects using powdered iron meteorite as raw material. The meteorite-based powder was used to produce a structural part but further research is needed to obtain a high density part without microcracks.

      PubDate: 2017-12-27T03:42:51Z
      DOI: 10.1016/j.actaastro.2017.11.027
      Issue No: Vol. 143 (2017)
  • Evolved atmospheric entry corridor with safety factor
    • Authors: Zixuan Liang; Zhang Ren; Qingdong Li
      Pages: 82 - 91
      Abstract: Publication date: February 2018
      Source:Acta Astronautica, Volume 143
      Author(s): Zixuan Liang, Zhang Ren, Qingdong Li
      Atmospheric entry corridors are established in previous research based on the equilibrium glide condition which assumes the flight-path angle to be zero. To get a better understanding of the highly constrained entry flight, an evolved entry corridor that considers the exact flight-path angle is developed in this study. Firstly, the conventional corridor in the altitude vs. velocity plane is extended into a three-dimensional one in the space of altitude, velocity, and flight-path angle. The three-dimensional corridor is generated by a series of constraint boxes. Then, based on a simple mapping method, an evolved two-dimensional entry corridor with safety factor is obtained. The safety factor is defined to describe the flexibility of the flight-path angle for a state within the corridor. Finally, the evolved entry corridor is simulated for the Space Shuttle and the Common Aero Vehicle (CAV) to demonstrate the effectiveness of the corridor generation approach. Compared with the conventional corridor, the evolved corridor is much wider and provides additional information. Therefore, the evolved corridor would benefit more to the entry trajectory design and analysis.

      PubDate: 2017-12-27T03:42:51Z
      DOI: 10.1016/j.actaastro.2017.11.021
      Issue No: Vol. 143 (2017)
  • Heat transfer reduction using combination of spike and counterflow jet on
           blunt body at high Mach number flow
    • Authors: Z. Eghlima; K. Mansour; K. Fardipour
      Pages: 92 - 104
      Abstract: Publication date: February 2018
      Source:Acta Astronautica, Volume 143
      Author(s): Z. Eghlima, K. Mansour, K. Fardipour
      Heat transfer reduction around blunt bodies is one of the important issues in the field of high speed aerodynamics. Using of spikes and counterflow jets each of them separately for reducing of drag force and heat transfer is well known. The present work is description of flow field around a hemispherical nose cylinder with a combination of spike and counterflow jet at free stream of Mach number of 6. The air gas was injected through the nozzle at the nose of the hemispherical model at sonic speed. In this numerical analysis, axisymmetric Reynolds-averaged Navier-Stokes equations was solved by k-ω (SST) turbulence model. The grid study was done and the results are validated with experimental results for spiked body without jet condition. Then the results presented for different lengths of spike and different pressures of counterflow jets. The results show a significant reduction in the peak heat transfer about 60%–78% for different models compared to the spherical cylinder model without any jet and spike. Furthermore, also our results indicate that the heat transfer reduction is increased even more with increasing of the length of the spike.

      PubDate: 2017-12-27T03:42:51Z
      DOI: 10.1016/j.actaastro.2017.11.012
      Issue No: Vol. 143 (2017)
  • New technologies for ammonium dinitramide based monopropellant thrusters
           – The project RHEFORM
    • Authors: Michele Negri; Marius Wilhelm; Christian Hendrich; Niklas Wingborg; Linus Gediminas; Leif Adelöw; Corentin Maleix; Pierre Chabernaud; Rachid Brahmi; Romain Beauchet; Yann Batonneau; Charles Kappenstein; Robert-Jan Koopmans; Sebastian Schuh; Tobias Bartok; Carsten Scharlemann; Ulrich Gotzig; Martin Schwentenwein
      Pages: 105 - 117
      Abstract: Publication date: February 2018
      Source:Acta Astronautica, Volume 143
      Author(s): Michele Negri, Marius Wilhelm, Christian Hendrich, Niklas Wingborg, Linus Gediminas, Leif Adelöw, Corentin Maleix, Pierre Chabernaud, Rachid Brahmi, Romain Beauchet, Yann Batonneau, Charles Kappenstein, Robert-Jan Koopmans, Sebastian Schuh, Tobias Bartok, Carsten Scharlemann, Ulrich Gotzig, Martin Schwentenwein
      New technologies are developed in the project RHEFORM to enable the replacement of hydrazine with liquid propellants based on ammonium dinitramide (ADN). The replacement of hydrazine with green propellants will make space propulsion more sustainable and better suitable for the requirements of future missions. In the RHEFORM project investigation on the composition of the propellants are conducted to enable the use of materials for catalysts and combustion chambers which are not subject to the International Traffic in Arms Regulations (ITAR). New igniters are under development aiming at a reduction of required energy and a more prompt ignition. Two different types of igniters are considered: improved catalytic igniters and thermal igniters. The technologies developed in RHEFORM will be implemented in two thruster demonstrators, aiming at a technology readiness level (TRL) of 5. In the present work the results obtained in the first half of the project are presented.

      PubDate: 2017-12-13T06:26:39Z
      DOI: 10.1016/j.actaastro.2017.11.016
      Issue No: Vol. 143 (2017)
  • Experimental study on line-of-sight (LOS) attitude control using control
           moment gyros under micro-gravity environment
    • Authors: Hirohisa Kojima; Kana Hiraiwa; Yasuhiro Yoshimura
      Pages: 118 - 125
      Abstract: Publication date: February 2018
      Source:Acta Astronautica, Volume 143
      Author(s): Hirohisa Kojima, Kana Hiraiwa, Yasuhiro Yoshimura
      This paper presents the results of line-of-sight (LOS) attitude control using control moment gyros under a micro-gravity environment generated by parabolic flight. The W-Z parameters are used to describe the spacecraft attitude. In order to stabilize the current LOS to the target LOS, backstepping-based feedback control is considered using the W-Z parameters. Numerical simulations and experiments under a micro-gravity environment are carried out, and their results are compared in order to validate the proposed control methods.

      PubDate: 2017-12-27T03:42:51Z
      DOI: 10.1016/j.actaastro.2017.11.020
      Issue No: Vol. 143 (2017)
  • Tethered spacecraft in asteroid gravitational environment
    • Authors: Alexander A. Burov; Anna D. Guerman; Ivan I. Kosenko; Vasily I. Nikonov
      Pages: 126 - 132
      Abstract: Publication date: February 2018
      Source:Acta Astronautica, Volume 143
      Author(s): Alexander A. Burov, Anna D. Guerman, Ivan I. Kosenko, Vasily I. Nikonov
      Relative equilibria of a pendulum attached to the surface of a uniformly rotating celestial body are considered. The locations of the tether anchor that correspond to a given spacecraft position are defined. The domains, where the spacecraft can be held with the help of such a pendulum, are also described. Stability of the found relative equilibria is studied.

      PubDate: 2017-12-27T03:42:51Z
      DOI: 10.1016/j.actaastro.2017.11.018
      Issue No: Vol. 143 (2017)
  • Suboptimal artificial potential function sliding mode control for
           spacecraft rendezvous with obstacle avoidance
    • Authors: Lu Cao; Dong Qiao; Jingwen Xu
      Pages: 133 - 146
      Abstract: Publication date: February 2018
      Source:Acta Astronautica, Volume 143
      Author(s): Lu Cao, Dong Qiao, Jingwen Xu
      Sub-Optimal Artificial Potential Function Sliding Mode Control (SOAPF-SMC) is proposed for the guidance and control of spacecraft rendezvous considering the obstacles avoidance, which is derived based on the theories of artificial potential function (APF), sliding mode control (SMC) and state dependent riccati equation (SDRE) technique. This new methodology designs a new improved APF to describe the potential field. It can guarantee the value of potential function converge to zero at the desired state. Moreover, the nonlinear terminal sliding mode is introduced to design the sliding mode surface with the potential gradient of APF, which offer a wide variety of controller design alternatives with fast and finite time convergence. Based on the above design, the optimal control theory (SDRE) is also employed to optimal the shape parameter of APF, in order to add some degree of optimality in reducing energy consumption. The new methodology is applied to spacecraft rendezvous with the obstacles avoidance problem, which is simulated to compare with the traditional artificial potential function sliding mode control (APF-SMC) and SDRE to evaluate the energy consumption and control precision. It is demonstrated that the presented method can avoiding dynamical obstacles whilst satisfying the requirements of autonomous rendezvous. In addition, it can save more energy than the traditional APF-SMC and also have better control accuracy than the SDRE.

      PubDate: 2017-12-13T06:26:39Z
      DOI: 10.1016/j.actaastro.2017.11.022
      Issue No: Vol. 143 (2017)
  • Control of pseudo-shock oscillation in scramjet inlet-isolator using
           periodical excitation
    • Authors: Wei-Yi Su; Yun Chen; Feng-Rui Zhang; Piao-Ping Tang
      Pages: 147 - 154
      Abstract: Publication date: February 2018
      Source:Acta Astronautica, Volume 143
      Author(s): Wei-Yi Su, Yun Chen, Feng-Rui Zhang, Piao-Ping Tang
      To suppress the pressure oscillation, stabilize the shock train in the scramjet isolator and delay the hypersonic inlet unstart, flow control using periodic excitation was investigated with unsteady Reynolds averaged Navier-Stokes simulations. The results showed that by injecting air to manipulate the cowl reflected shock wave, the separation bubble induced by it was diminished and the pressure oscillations of the shock train were markedly suppressed. The power spectral density and standard deviation of wall pressure were significantly reduced. The simulations revealed that this active control method can raise the critical back pressure by 17.5% compared with the baseline, which would successfully delay the hypersonic inlet unstarts. The results demonstrated that this active control method is effective in suppressing pressure oscillation and delaying hypersonic inlet unstarts.

      PubDate: 2017-12-13T06:26:39Z
      DOI: 10.1016/j.actaastro.2017.10.040
      Issue No: Vol. 143 (2017)
  • Building X-ray pulsar timing model without the use of radio parameters
    • Authors: Hai-feng Sun; Xiong Sun; Hai-yan Fang; Li-rong Shen; Shao-peng Cong; Yan-ming Liu; Xiao-ping Li; Wei-min Bao
      Pages: 155 - 162
      Abstract: Publication date: February 2018
      Source:Acta Astronautica, Volume 143
      Author(s): Hai-feng Sun, Xiong Sun, Hai-yan Fang, Li-rong Shen, Shao-peng Cong, Yan-ming Liu, Xiao-ping Li, Wei-min Bao
      This paper develops a timing solution for the X-ray pulsar timing model without the use of the initial radio model parameters. First, we address the problem of phase ambiguities for the pre-fit residuals in the construction of pulsar timing model. To improve the estimation accuracy of the pulse time of arrival (TOA), we have deduced the general form of test statistics in Fourier transform, and discussed their estimation performances. Meanwhile, a fast maximum likelihood (FML) technique is presented to estimate the pulse TOA, which outperforms cross correlation (CC) estimator and exhibits a performance comparable with maximum likelihood (ML) estimator in spite of a much less reduced computational complexity. Depending on the strategy of the difference minimum of pre-fit residuals, we present an effective forced phase-connected technique to achieve initial model parameters. Then, we use the observations with the Rossi X-Ray Timing Explorer (RXTE) and X-ray pulsar navigation-I (XPNAV-1) satellites for experimental studies, and discuss main differences for the root mean square (RMS) residuals calculated with the X-ray and radio ephemerides. Finally, a chi-square value (CSV) of pulse profiles is presented as a complementary indicator to the RMS residuals for evaluating the model parameters. The results show that the proposed timing solution is valid and effective, and the obtained model parameters can be a reasonable alternative to the radio ephemeris.

      PubDate: 2017-12-27T03:42:51Z
      DOI: 10.1016/j.actaastro.2017.11.014
      Issue No: Vol. 143 (2017)
  • Anthropomorphism in the search for extra-terrestrial intelligence – The
           limits of cognition'
    • Authors: Ulrike M. Bohlmann; Moritz J.F. Bürger
      Pages: 163 - 168
      Abstract: Publication date: February 2018
      Source:Acta Astronautica, Volume 143
      Author(s): Ulrike M. Bohlmann, Moritz J.F. Bürger
      The question “Are we alone'” lingers in the human mind since ancient times. Early human civilisations populated the heavens above with a multitude of Gods endowed with some all too human characteristics – from their outer appearance to their innermost motivations. En passant they created thereby their own cultural founding myths on which they built their understanding of the world and its phenomena and deduced as well rules for the functioning of their own society. Advancing technology has enabled us to conduct this human quest for knowledge with more scientific means: optical and radio-wavelengths are being monitored for messages by an extra-terrestrial intelligence and active messaging attempts have also been undertaken. Scenarios have been developed for a possible detection of extra-terrestrial intelligence and post-detection guidelines and protocols have been elaborated. The human responses to the whole array of questions concerning the potential existence, discovery of and communication/interaction with an extra-terrestrial intelligence share as one clear thread a profound anthropomorphism, which ascribes classical human behavioural patterns also to an extra-terrestrial intelligence in much the same way as our ancestors attributed comparable conducts to mythological figures. This paper aims at pinpointing this thread in a number of classical reactions to basic questions related to the search for extra-terrestrial intelligence. Many of these reactions are based on human motives such as curiosity and fear, rationalised by experience and historical analogy and modelled in the Science Fiction Culture by literature and movies. Scrutinising the classical hypothetical explanations of the Fermi paradox under the angle of a potentially undue anthropomorphism, this paper intends to assist in understanding our human epistemological limitations in the search for extra-terrestrial intelligence. This attempt is structured into a series of questions: I. Can we be alone' II. Who are we looking for' III. Or what are we looking for' IV. Where is everybody' V. What if we make contact and VI. So, what now'

      PubDate: 2017-12-13T06:26:39Z
      DOI: 10.1016/j.actaastro.2017.11.033
      Issue No: Vol. 143 (2017)
  • Vibration isolation and dual-stage actuation pointing system for space
           precision payloads
    • Authors: Yongfang Kong; Hai Huang
      Pages: 183 - 192
      Abstract: Publication date: February 2018
      Source:Acta Astronautica, Volume 143
      Author(s): Yongfang Kong, Hai Huang
      Pointing and stability requirements for future space missions are becoming more and more stringent. This work follows the pointing control method which consists of a traditional spacecraft attitude control system and a payload active pointing loop, further proposing a vibration isolation and dual-stage actuation pointing system for space precision payloads based on a soft Stewart platform. Central to the concept is using the dual-stage actuator instead of the traditional voice coil motor single-stage actuator to improve the payload active pointing capability. Based on a specified payload, the corresponding platform was designed to be installed between the spacecraft bus and the payload. The performance of the proposed system is demonstrated by preliminary closed-loop control investigations in simulations. With the ordinary spacecraft bus, the line-of-sight pointing accuracy can be controlled to below a few milliarcseconds in tip and tilt. Meanwhile, utilizing the voice coil motor with the softening spring in parallel, which is a portion of the dual-stage actuator, the system effectively achieves low-frequency motion transmission and high-frequency vibration isolation along the other four degree-of-freedom directions.

      PubDate: 2017-12-13T06:26:39Z
      DOI: 10.1016/j.actaastro.2017.11.038
      Issue No: Vol. 143 (2017)
  • Mixing and combustion enhancement of Turbocharged Solid Propellant Ramjet
    • Authors: Shichang Liu; Jiang Li; Gen Zhu; Wei Wang; Yang Liu
      Pages: 193 - 202
      Abstract: Publication date: February 2018
      Source:Acta Astronautica, Volume 143
      Author(s): Shichang Liu, Jiang Li, Gen Zhu, Wei Wang, Yang Liu
      Turbocharged Solid Propellant Ramjet is a new concept engine that combines the advantages of both solid rocket ramjet and Air Turbo Rocket, with a wide operation envelope and high performance. There are three streams of the air, turbine-driving gas and augment gas to mix and combust in the afterburner, and the coaxial intake mode of the afterburner is disadvantageous to the mixing and combustion. Therefore, it is necessary to carry out mixing and combustion enhancement research. In this study, the numerical model of Turbocharged Solid Propellant Ramjet three-dimensional combustion flow field is established, and the numerical simulation of the mixing and combustion enhancement scheme is conducted from the aspects of head region intake mode to injection method in afterburner. The results show that by driving the compressed air to deflect inward and the turbine-driving gas to maintain strong rotation, radial and tangential momentum exchange of the two streams can be enhanced, thereby improving the efficiency of mixing and combustion in the afterburner. The method of injecting augment gas in the transverse direction and making sure the injection location is as close as possible to the head region is beneficial to improve the combustion efficiency. The outer combustion flow field of the afterburner is an oxidizer-rich environment, while the inner is a fuel-rich environment. To improve the efficiency of mixing and combustion, it is necessary to control the injection velocity of the augment gas to keep it in the oxygen-rich zone of the outer region. The numerical simulation for different flight conditions shows that the optimal mixing and combustion enhancement scheme can obtain high combustion efficiency and have excellent applicability in a wide working range.

      PubDate: 2017-12-13T06:26:39Z
      DOI: 10.1016/j.actaastro.2017.11.017
      Issue No: Vol. 143 (2017)
  • Agile deployment and code coverage testing metrics of the boot software
           on-board Solar Orbiter's Energetic Particle Detector
    • Authors: Pablo Parra; Antonio da Silva; Óscar R. Polo; Sebastián Sánchez
      Pages: 203 - 211
      Abstract: Publication date: February 2018
      Source:Acta Astronautica, Volume 143
      Author(s): Pablo Parra, Antonio da Silva, Óscar R. Polo, Sebastián Sánchez
      In this day and age, successful embedded critical software needs agile and continuous development and testing procedures. This paper presents the overall testing and code coverage metrics obtained during the unit testing procedure carried out to verify the correctness of the boot software that will run in the Instrument Control Unit (ICU) of the Energetic Particle Detector (EPD) on-board Solar Orbiter. The ICU boot software is a critical part of the project so its verification should be addressed at an early development stage, so any test case missed in this process may affect the quality of the overall on-board software. According to the European Cooperation for Space Standardization ESA standards, testing this kind of critical software must cover 100% of the source code statement and decision paths. This leads to the complete testing of fault tolerance and recovery mechanisms that have to resolve every possible memory corruption or communication error brought about by the space environment. The introduced procedure enables fault injection from the beginning of the development process and enables to fulfill the exigent code coverage demands on the boot software.

      PubDate: 2017-12-13T06:26:39Z
      DOI: 10.1016/j.actaastro.2017.11.037
      Issue No: Vol. 143 (2017)
  • Extended state observer based robust adaptive control on SE(3) for coupled
           spacecraft tracking maneuver with actuator saturation and misalignment
    • Authors: Jianqiao Zhang; Dong Ye; Zhaowei Sun; Chuang Liu
      Pages: 221 - 233
      Abstract: Publication date: February 2018
      Source:Acta Astronautica, Volume 143
      Author(s): Jianqiao Zhang, Dong Ye, Zhaowei Sun, Chuang Liu
      This paper presents a robust adaptive controller integrated with an extended state observer (ESO) to solve coupled spacecraft tracking maneuver in the presence of model uncertainties, external disturbances, actuator uncertainties including magnitude deviation and misalignment, and even actuator saturation. More specifically, employing the exponential coordinates on the Lie group SE(3) to describe configuration tracking errors, the coupled six-degrees-of-freedom (6-DOF) dynamics are developed for spacecraft relative motion, in which a generic fully actuated thruster distribution is considered and the lumped disturbances are reconstructed by using anti-windup technique. Then, a novel ESO, developed via second order sliding mode (SOSM) technique and adding linear correction terms to improve the performance, is designed firstly to estimate the disturbances in finite time. Based on the estimated information, an adaptive fast terminal sliding mode (AFTSM) controller is developed to guarantee the almost global asymptotic stability of the resulting closed-loop system such that the trajectory can be tracked with all the aforementioned drawbacks addressed simultaneously. Finally, the effectiveness of the controller is illustrated through numerical examples.

      PubDate: 2017-12-27T03:42:51Z
      DOI: 10.1016/j.actaastro.2017.11.034
      Issue No: Vol. 143 (2017)
  • A review of MEMS micropropulsion technologies for CubeSats and PocketQubes
    • Authors: Marsil A.C. Silva; Daduí C. Guerrieri; Angelo Cervone; Eberhard Gill
      Pages: 234 - 243
      Abstract: Publication date: February 2018
      Source:Acta Astronautica, Volume 143
      Author(s): Marsil A.C. Silva, Daduí C. Guerrieri, Angelo Cervone, Eberhard Gill
      CubeSats have been extensively used in the past decade as scientific tools, technology demonstrators and for education. Recently, PocketQubes have emerged as an interesting and even smaller alternative to CubeSats. However, both satellite types often lack some key capabilities, such as micropropulsion, in order to further extend the range of applications of these small satellites. This paper reviews the current development status of micropropulsion systems fabricated with MEMS (micro electro-mechanical systems) and silicon technology intended to be used in CubeSat or PocketQube missions and compares different technologies with respect to performance parameters such as thrust, specific impulse, and power as well as in terms of operational complexity. More than 30 different devices are analyzed and divided into 7 main categories according to the working principle. A specific outcome of the research is the identification of the current status of MEMS technologies for micropropulsion including key opportunities and challenges.

      PubDate: 2017-12-27T03:42:51Z
      DOI: 10.1016/j.actaastro.2017.11.049
      Issue No: Vol. 143 (2017)
  • Periodic forcing of a shock train in a scramjet inlet-isolator at
           overspeed condition
    • Authors: Xiaoliang Jiao; Juntao Chang; Zhongqi Wang; Daren Yu
      Pages: 244 - 254
      Abstract: Publication date: February 2018
      Source:Acta Astronautica, Volume 143
      Author(s): Xiaoliang Jiao, Juntao Chang, Zhongqi Wang, Daren Yu
      Unsteady viscous numerical simulations are performed to explore the response of a shock train to downstream backpressure forcing in a scramjet inlet-isolator at the overspeed condition. A sinusoidal dynamic backpressure is applied at the exit of the isolator, thus leading a forced shock train oscillation. The results show that the shock train travels along a different path for the upstream and downstream movements. There is a clear hysteresis loop during the shock train oscillation. Under the low forcing frequency, the shock train travels in a clockwise loop. While it travels in a counter-clockwise loop under the high forcing frequency. Moreover, there is a lag between the shock train oscillation and the fluctuating backpressure. Especially for the high forcing frequency, the phase of the shock train oscillation is opposite to the fluctuating backpressure. The effects of the amplitude and frequency of the periodic fluctuating backpressure on the oscillation range of the shock train are also investigated. With the amplitude of the fluctuating backpressure increasing, the oscillation range of the shock train increases. With the frequency of the fluctuating backpressure increasing, the oscillation range of the shock train increases first and then decreases under high frequency.

      PubDate: 2017-12-27T03:42:51Z
      DOI: 10.1016/j.actaastro.2017.12.005
      Issue No: Vol. 143 (2017)
  • Mechanical properties of multifunctional structure with viscoelastic
           components based on FVE model
    • Authors: Dong Hao; Lin Zhang; Jing Yu; Daiyong Mao
      Pages: 255 - 262
      Abstract: Publication date: February 2018
      Source:Acta Astronautica, Volume 143
      Author(s): Dong Hao, Lin Zhang, Jing Yu, Daiyong Mao
      Based on the models of Lion and Kardelky (2004) and Hofer and Lion (2009), a finite viscoelastic (FVE) constitutive model, considering the predeformation-, frequency- and amplitude-dependent properties, has been proposed in our earlier paper [1]. FVE model is applied to investigating the dynamic characteristics of the multifunctional structure with the viscoelastic components. Combing FVE model with the finite element theory, the dynamic model of the multifunctional structure could be obtained. Additionally, the parametric identification and the experimental verification are also given via the frequency-sweep tests. The results show that the computational data agree well with the experimental data. FVE model has made a success of expressing the dynamic characteristics of the viscoelastic materials utilized in the multifunctional structure. The multifunctional structure technology has been verified by in-orbit experiments.
      Graphical abstract image

      PubDate: 2017-12-27T03:42:51Z
      DOI: 10.1016/j.actaastro.2017.11.043
      Issue No: Vol. 143 (2017)
  • Electro-mechanical vibration analysis of functionally graded piezoelectric
           porous plates in the translation state
    • Authors: Yan Qing Wang
      Pages: 263 - 271
      Abstract: Publication date: February 2018
      Source:Acta Astronautica, Volume 143
      Author(s): Yan Qing Wang
      To provide reference for aerospace structural design, electro-mechanical vibrations of functionally graded piezoelectric material (FGPM) plates carrying porosities in the translation state are investigated. A modified power law formulation is employed to depict the material properties of the plates in the thickness direction. Three terms of inertial forces are taken into account due to the translation of plates. The geometrical nonlinearity is considered by adopting the von Kármán non-linear relations. Using the d’Alembert's principle, the nonlinear governing equation of the out-of-plane motion of the plates is derived. The equation is further discretized to a system of ordinary differential equations using the Galerkin method, which are subsequently solved via the harmonic balance method. Then, the approximate analytical results are validated by utilizing the adaptive step-size fourth-order Runge-Kutta technique. Additionally, the stability of the steady state responses is examined by means of the perturbation technique. Linear and nonlinear vibration analyses are both carried out and results display some interesting dynamic phenomenon for translational porous FGPM plates. Parametric study shows that the vibration characteristics of the present inhomogeneous structure depend on several key physical parameters.

      PubDate: 2017-12-27T03:42:51Z
      DOI: 10.1016/j.actaastro.2017.12.004
      Issue No: Vol. 143 (2017)
  • A new planetary structure fabrication process using phosphoric acid
    • Authors: Christoph Buchner; Roland H. Pawelke; Thomas Schlauf; Alexander Reissner; Advenit Makaya
      Pages: 272 - 284
      Abstract: Publication date: February 2018
      Source:Acta Astronautica, Volume 143
      Author(s): Christoph Buchner, Roland H. Pawelke, Thomas Schlauf, Alexander Reissner, Advenit Makaya
      Minimising the launch mass is an important aspect of exploration mission planning. In-situ resource utilisation (ISRU) can improve this by reducing the amount of terrestrial materials needed for planetary exploration activities. We report on a recently concluded investigation into the requirements and available technologies for creating hardware on extra-terrestrial bodies, using the limited resources available on site. A trade-off of ISRU technologies for hardware manufacturing was conducted. A new additive manufacturing process suitable for fabricating structures on the Moon or Mars was developed. The process uses planetary regolith as the base material and concentrated phosphoric acid as the liquid binder. Mixing the reagents creates a sticky construction paste that slowly solidifies into a hard, rock-like material. Prior to solidification, the paste is extruded in layers, creating the desired structures in a 3D printing process. We used Martian regolith simulant JSC-Mars-1A, but the process is not selective towards regolith composition. Samples were exposed to thermal cycles and were mechanically characterised. Reduced-scale demonstrator structures were printed to demonstrate structure fabrication using the developed process.

      PubDate: 2017-12-27T03:42:51Z
      DOI: 10.1016/j.actaastro.2017.11.045
      Issue No: Vol. 143 (2017)
  • Program options to explore ocean worlds
    • Authors: B. Sherwood; J. Lunine; C. Sotin; T. Cwik; F. Naderi
      Pages: 285 - 296
      Abstract: Publication date: February 2018
      Source:Acta Astronautica, Volume 143
      Author(s): B. Sherwood, J. Lunine, C. Sotin, T. Cwik, F. Naderi
      Including Earth, roughly a dozen water ocean worlds exist in the solar system: the relict worlds Ceres and Mars, vast oceans inside most of the large Jovian and Saturnian icy moons, and Kuiper Belt Objects like Triton, Charon, and Pluto whose geologies are dominated by water and ammonia. Key pieces of the ocean-world science puzzle – which when completed may reveal whether life is widespread in the cosmos, why it exists where it does, and how it originates – are distributed among them. The eventual exploration of all these worlds will yield humanity's total tangible knowledge about life in the universe, essentially forever. Thus, their exploration has existential significance for humanity's self-regard, and indeed perhaps of our place in the natural scheme. The matter of planning how to pursue such a difficult and unprecedented exploration opportunity is therefore historic. The technical challenges are formidable, far harder than at Mars: missions to the Jovian and Saturnian ocean worlds are severely power-limited; trip times can be as much as a half decade and decade, respectively. And the science targets are global-scale oceans beneath kilometers of cryogenic ice. Reaching and exploring them would be a multi-generational undertaking, so again it is essential to plan and prepare. Today, we lack the instrumentation, subsystems, and remote operational-intelligence technologies needed to build and use exploration avatars as good as what we can envision needing. Each ocean world holds a piece of the puzzle, but the three priority targets are Europa at Jupiter, and Enceladus and Titan at Saturn. As with the systematic exploration of Mars, exploring these diverse worlds poses a complex technical and programmatic challenge – a strategic challenge – that needs to be designed and managed if each generation is to see its work bear fruit, and if the space science community is to make most effective use of the public money devoted to the quest. Strategic programs benefit from coherence. In only 15 years, the Mars Exploration Program (MEP) has transformed humanity's view of Mars as a once and future habitable place, a world quite possibly holding relict evidence of life. Finding such evidence, we would study it to know if that life shared an origin common with Earth life. However, life in the ocean worlds could not have shared our origin, so exploring them opens another level in our quest to understand life in the universe: not only to places with vast salt-water seas known to contain organics and hydrothermal seafloors active today, but to places where anything alive cannot be related to us. MEP's success – from its presence in the public consciousness to its rewriting of planetary habitability – make it an obvious template and source of lessons learned for a viable ocean worlds exploration program (OWEP). Six attributes of the MEP are analyzed for application to a potential OWEP. From this, five hypothetical programmatic scenarios are compared to the default case, and conclusions drawn. A coherent OWEP should have several parts: first, dedicated continuous investment in enabling technologies; and second, two directed-purpose, medium-class (∼$1 B) missions per decade that conduct pivotal investigations on a documented roadmap. Science could start in 2035, informing development of decadal flagship missions after Europa Clipper, to the places revealed to hold the most promise. The fastest pace of scientific discoveries would require access to high-performance propulsion infrastructure, e.g., the Space Launch System, Falcon Heavy, and high-power in-space solar electric propulsion, all capable of halving trip time. Not including these boosts, such a program would cost about a half-billion dollars more per year than NASA's existing mission portfolio; the program architecture funded today cannot deliver a strategic OWEP while also sustaining balance among other solar system exploration priorities and opportunities. Follow the Water. Yes, into the Ocean Worlds.

      PubDate: 2017-12-27T03:42:51Z
      DOI: 10.1016/j.actaastro.2017.11.047
      Issue No: Vol. 143 (2017)
  • Microgravity effect on endophytic bacteria communities of Triticum
    • Authors: Youcai Qin; Yuming Fu; Huiwen Chen; Hong Liu; Yi Sun
      Pages: 297 - 301
      Abstract: Publication date: February 2018
      Source:Acta Astronautica, Volume 143
      Author(s): Youcai Qin, Yuming Fu, Huiwen Chen, Hong Liu, Yi Sun
      Under normal gravity conditions, endophytic bacteria, one of the key bacterial community that inhabit in plant tissues, are well-known in promoting the plant growth and health, which are essential for long-term and long-distance manned microgravity space exploration. Here, we report how the Triticum aestivum endophytic bacterial communities behave differently under the simulated microgravity conditions. We demonstrate that, under simulated microgravity conditions, the microbial diversity in wheat seedling leaf increases while that in root decreases, compared to that cultivated under normal gravity conditions. We found that the dominant bacteria genus such as Pseudomonas, Paenibacillus and Bacillus significantly changes with gravity. The findings of this study provide important insight for space research, especially in terms of the Triticum aestivum cultivation in space.

      PubDate: 2017-12-27T03:42:51Z
      DOI: 10.1016/j.actaastro.2017.11.008
      Issue No: Vol. 143 (2017)
  • A data driven control method for structure vibration suppression
    • Authors: Yangmin Xie; Chao Wang; Hang Shi; Junwei Shi
      Pages: 302 - 309
      Abstract: Publication date: February 2018
      Source:Acta Astronautica, Volume 143
      Author(s): Yangmin Xie, Chao Wang, Hang Shi, Junwei Shi
      High radio-frequency space applications have motivated continuous research on vibration suppression of large space structures both in academia and industry. This paper introduces a novel data driven control method to suppress vibrations of flexible structures and experimentally validates the suppression performance. Unlike model-based control approaches, the data driven control method designs a controller directly from the input-output test data of the structure, without requiring parametric dynamics and hence free of system modeling. It utilizes the discrete frequency response via spectral analysis technique and formulates a non-convex optimization problem to obtain optimized controller parameters with a predefined controller structure. Such approach is then experimentally applied on an end-driving flexible beam-mass structure. The experiment results show that the presented method can achieve competitive disturbance rejections compared to a model-based mixed sensitivity controller under the same design criterion but with much less orders and design efforts, demonstrating the proposed data driven control is an effective approach for vibration suppression of flexible structures.

      PubDate: 2017-12-27T03:42:51Z
      DOI: 10.1016/j.actaastro.2017.11.046
      Issue No: Vol. 143 (2017)
  • Dynamic modeling and Super-Twisting Sliding Mode Control for Tethered
           Space Robot
    • Authors: Yakun Zhao; Panfeng Huang; Fan Zhang
      Pages: 310 - 321
      Abstract: Publication date: February 2018
      Source:Acta Astronautica, Volume 143
      Author(s): Yakun Zhao, Panfeng Huang, Fan Zhang
      Recent years, tethered space capturing systems have been considered as one of the most promising solutions for active space debris removal due to the increasing threat of space debris to spacecraft and astronauts. In this paper, one of the tethered space capturing systems, Tethered Space Robot (TSR), is investigated. TSR includes a space platform, a space tether, and a gripper as the terminal device. Based on the assumptions that the platform and the gripper are point masses and the tether is rigid, inextensible and remaining straight, the dynamic model of TSR is presented, in which the disturbances from space environment is considered. According to the previous study, the in-plane and out-of-plane angles of the tether oscillate periodically although the tether is released to the desired length. A super-twisting adaptive sliding mode control scheme is designed for TSR to eliminate the vibration of the tether to assure a successful capture in station-keeping phase. Both uncontrolled and controlled situations are simulated. The simulation results show that the proposed controller is effective. Additionally, after comparing with normal sliding mode control algorithm, it is verified that the proposed control scheme can avoid the chattering of normal sliding mode control and is robust for unknown boundary perturbations.

      PubDate: 2017-12-27T03:42:51Z
      DOI: 10.1016/j.actaastro.2017.11.025
      Issue No: Vol. 143 (2017)
  • Ethics and public integrity in space exploration
    • Authors: Adam F. Greenstone
      Pages: 322 - 326
      Abstract: Publication date: February 2018
      Source:Acta Astronautica, Volume 143
      Author(s): Adam F. Greenstone
      This paper discusses the National Aeronautics and Space Administration's (NASA) work to support ethics and public integrity in human space exploration. Enterprise Risk Management (ERM) to protect an organization's reputation has become widespread in the private sector. Government ethics law and practice is integral to a government entity's ERM by managing public sector reputational risk. This activity has also increased on the international plane, as seen by the growth of ethics offices in UN organizations and public international financial institutions. Included in this area are assessments to ensure that public office is not used for private gain, and that external entities are not given inappropriate preferential treatment. NASA has applied rules supporting these precepts to its crew since NASA's inception. The increased focus on public sector ethics principles for human activity in space is important because of the international character of contemporary space exploration. This was anticipated by the 1998 Intergovernmental Agreement for the International Space Station (ISS), which requires a Code of Conduct for the Space Station Crew. Negotiations among the ISS Partners established agreed-upon ethics principles, now codified for the United States in regulations at 14 C.F.R. § 1214.403. Understanding these ethics precepts in an international context requires cross-cultural dialogue. Given NASA's long spaceflight experience, a valuable part of this dialogue is understanding NASA's implementation of these requirements. Accordingly, this paper will explain how NASA addresses these and related issues, including for human spaceflight and crew, as well as the development of U.S. Government ethics law which NASA follows as a U.S. federal agency. Interpreting how the U.S. experience relates constructively to international application involves parsing out which dimensions relate to government ethics requirements that the international partners have integrated into the ISS Crew Code of Conduct, and which relate to other areas of U.S. administrative law. It is also constructive to identify areas where national and/or cultural perspectives may differ. Another reason for heightened focus on ethics is the increasing regularity of long duration human spaceflight. In earlier days of spaceflight astronauts had little time for anything other than mission operations. The increase in inflight personal time and opportunity for personal communications heightens the importance to spacefaring nations of advising on ethics obligations in real time. Through individual and collective action, stakeholders in evolving and future government space exploration will be able to effectively address ethics compliance and reputational risk.

      PubDate: 2017-12-27T03:42:51Z
      DOI: 10.1016/j.actaastro.2017.10.031
      Issue No: Vol. 143 (2017)
  • Attitude dynamics and control of spacecraft with a partially filled liquid
           tank and flexible panels
    • Authors: Feng Liu; Baozeng Yue; Liangyu Zhao
      Pages: 327 - 336
      Abstract: Publication date: February 2018
      Source:Acta Astronautica, Volume 143
      Author(s): Feng Liu, Baozeng Yue, Liangyu Zhao
      A liquid-filled flexible spacecraft is essentially a time-variant fully-coupled system, whose dynamics characteristics are closely associated with its motion features. This paper focuses on the mathematical modelling and attitude control of the spacecraft coupled with fuel sloshing dynamics and flexible solar panels vibration. The slosh motion is represented by a spherical pendulum, whose motion description method is improved by using split variable operation. Benefiting from this improvement, the nonlinear lateral sloshing and the rotary sloshing as well as the rigid motion of a liquid respect to the spacecraft can be approximately described. The assumed modes discretization method has been adopted to approximate the elastic displacements of the attached panels, and the coupled dynamics is derived by using the Lagrangian formulation. A variable substitution method is proposed to obtain the apparently-uncoupled mathematical model of the rigid–flexible–liquid spacecraft. After linearization, this model can be directly used for designing Lyapunov output-feedback attitude controller (OFAC). With only torque actuators, and attitude and rate sensors installed, this kind of attitude controller, as simulation results show, is capable of not only bringing the spacecraft to the desired orientation, but also suppressing the effect of flex and slosh on the attitude motion of the spacecraft.

      PubDate: 2017-12-27T03:42:51Z
      DOI: 10.1016/j.actaastro.2017.11.036
      Issue No: Vol. 143 (2017)
  • Investigate the shock focusing under a single vortex disturbance using 2D
           Saint-Venant equations with a shock-capturing scheme
    • Authors: Jiaquan Zhao; Renfu Li; Haiyan Wu
      Pages: 337 - 352
      Abstract: Publication date: February 2018
      Source:Acta Astronautica, Volume 143
      Author(s): Jiaquan Zhao, Renfu Li, Haiyan Wu
      In order to characterize the flow structure and the effect of acoustic waves caused by the shock–vortex interaction on the performance of the shock focusing, the incident plane shock wave with a single disturbance vortex focusing in a parabolic cavity is simulated systematically through solving the two-dimensional, unsteady Saint-Venant equations with the two order HLL scheme of Riemann solvers. The simulations show that the dilatation effect to be dominant in the net vorticity generation, while the baroclinic effect is dominate in the absence of initial vortex disturbance. Moreover, the simulations show that the time evolution of maximum focusing pressure with initial vortex is more complicate than that without initial vortex, which has a lot of relevance with the presence of quadrupolar acoustic wave structure induced by shock-vortex interaction and its propagation in the cavity. Among shock and other disturbance parameters, the shock Mach number, vortex Mach number and the shape of parabolic reflector proved to play a critical role in the focusing of shock waves and the strength of viscous dissipation, which in turn govern the evolution of maximum focusing pressure due to the gas dynamic focus, the change in dissipation rate and the coincidence of motion disturbance vortex with aerodynamic focus point.

      PubDate: 2017-12-27T03:42:51Z
      DOI: 10.1016/j.actaastro.2017.11.040
      Issue No: Vol. 143 (2017)
  • Analysis of a Moon outpost for Mars enabling technologies through a
           Virtual Reality environment
    • Authors: Andrea E.M. Casini; Paolo Maggiore; Nicole Viola; Valter Basso; Marinella Ferrino; Jeffrey A. Hoffman; Aidan Cowley
      Pages: 353 - 361
      Abstract: Publication date: February 2018
      Source:Acta Astronautica, Volume 143
      Author(s): Andrea E.M. Casini, Paolo Maggiore, Nicole Viola, Valter Basso, Marinella Ferrino, Jeffrey A. Hoffman, Aidan Cowley
      The Moon is now being considered as the starting point for human exploration of the Solar System beyond low-Earth orbit. Many national space agencies are actively advocating to build up a lunar surface habitat capability starting from 2030 or earlier: according to ESA Technology Roadmaps for Exploration this should be the result of a broad international cooperation. Taking into account an incremental approach to reduce risks and costs of space missions, a lunar outpost can be considered as a test bed towards Mars, allowing to validate enabling technologies, such as water processing, waste management, power generation and storage, automation, robotics and human factors. Our natural satellite is rich in resources that could be used to pursue such a goal through a necessary assessment of ISRU techniques. The aim of this research is the analysis of a Moon outpost dedicated to the validation of enabling technologies for human space exploration. The main building blocks of the outpost are identified and feasible evolutionary scenarios are depicted, to highlight the incremental steps to build up the outpost. Main aspects that are dealt with include outpost location and architecture, as well as ISRU facilities, which in a far term future can help reduce the mass at launch, by producing hydrogen and oxygen for consumables, ECLSS, and propellant for Earth-Moon sorties and Mars journeys. A test outpost is implemented in a Virtual Reality (VR) environment as a first proof-of-concepts, where the elements are computer-based mock-ups. The VR facility has a first-person interactive perspective, allowing for specific in-depth analyses of ergonomics and operations. The feedbacks of these analyses are crucial to highlight requirements that might otherwise be overlooked, while their general outputs are fundamental to write down procedures. Moreover, the mimic of astronauts' EVAs is useful for pre-flight training, but can also represent an additional tool for failures troubleshooting during the flight controllers' nominal operations. Additionally, illumination maps have been obtained to study the light conditions, which are essential parameters to assess the base elements location. This unique simulation environment may offer the largest suite of benefits during the design and development phase, as it allows to design future systems to optimize operations, thus maximizing the mission's scientific return, and to enhance the astronauts training, by saving time and cost. The paper describes how a virtual environment could help to design a Moon outpost for an incremental architecture strategy towards Mars missions.

      PubDate: 2017-12-27T03:42:51Z
      DOI: 10.1016/j.actaastro.2017.11.023
      Issue No: Vol. 143 (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
  • Adaptive relative pose control of spacecraft with model couplings and
    • Authors: Liang Sun; Zewei Zheng
      Abstract: Publication date: Available online 11 November 2017
      Source:Acta Astronautica
      Author(s): Liang Sun, Zewei Zheng
      The spacecraft pose tracking control problem for an uncertain pursuer approaching to a space target is researched in this paper. After modeling the nonlinearly coupled dynamics for relative translational and rotational motions between two spacecraft, position tracking and attitude synchronization controllers are developed independently by using a robust adaptive control approach. The unknown kinematic couplings, parametric uncertainties, and bounded external disturbances are handled with adaptive updating laws. It is proved via Lyapunov method that the pose tracking errors converge to zero asymptotically. Spacecraft close-range rendezvous and proximity operations are introduced as an example to validate the effectiveness of the proposed control approach.

      PubDate: 2017-11-11T07:43:12Z
      DOI: 10.1016/j.actaastro.2017.11.006
School of Mathematical and Computer Sciences
Heriot-Watt University
Edinburgh, EH14 4AS, UK
Tel: +00 44 (0)131 4513762
Fax: +00 44 (0)131 4513327
Home (Search)
Subjects A-Z
Publishers A-Z
Your IP address:
About JournalTOCs
News (blog, publications)
JournalTOCs on Twitter   JournalTOCs on Facebook

JournalTOCs © 2009-2016