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Journal Cover Acta Astronautica
  [SJR: 0.726]   [H-I: 43]   [387 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0094-5765
   Published by Elsevier Homepage  [3177 journals]
  • Shock wave structures in the wake of sonic transverse jet into a
           supersonic crossflow
    • Authors: Chang-hai Liang; Ming-bo Sun; Yuan Liu; Yi-xin Yang
      Pages: 12 - 21
      Abstract: Publication date: July 2018
      Source:Acta Astronautica, Volume 148
      Author(s): Chang-hai Liang, Ming-bo Sun, Yuan Liu, Yi-xin Yang
      This study experimentally and numerically investigated the flow physics of a sonic transverse gaseous jet under a Ma = 2.95 supersonic crossflow. NPLS (Nanoparticle-based Planar Laser Scattering) and oil flow techniques were combined to achieve experimental visualization, while RANS (Reynolds-averaged Navier-Stokes) model was used to carry out the numerical simulation. Under the supersonic crossflow with jet-to-crossflow momentum flux ratio (J) of 7.7, the typical structures, including a bow shock, a barrel shock, horseshoe vortex, and separation zones, were clearly observed by the NPLS techniques. V-shape separation bubbles and V-shape collision shocks were identified based on the oil-flow results. Detailed flow fields around the V-shape separation bubble were then revealed by numerical calculations. It is shown that the collision shock induced V-shape separation bubbles can further affect the Mach disk, the reflected shock and the barrel shock. The reflected shock deflects the collision shock toward the two flanks. The collision shock intersects with the barrel shock, influencing the shape of the Mach disk. In addition, the interaction between the reflected shock and the wall leads to the velocity slip in the near-wall region.

      PubDate: 2018-05-02T17:12:21Z
      DOI: 10.1016/j.actaastro.2018.04.009
      Issue No: Vol. 148 (2018)
       
  • Conceptual Moon imaging micro/nano-satellite design optimization under
           uncertainty
    • Authors: Xingzhi Hu; Yong Zhao; Xiaoqian Chen; Valerio Lattarulo
      Pages: 22 - 31
      Abstract: Publication date: July 2018
      Source:Acta Astronautica, Volume 148
      Author(s): Xingzhi Hu, Yong Zhao, Xiaoqian Chen, Valerio Lattarulo
      Low-cost Moon imaging micro/nano-satellites have been receiving much attention from the engineering community. The reliability-based robust design optimization (RBRDO) of these weight/size/power constrained satellites is crucial. In this study, the configuration of this conceptual design problem considering uncertainty is analyzed and the interdisciplinary relations are described. Discipline models including orbit, payload, propulsion, and communication are mainly discussed. A new RBRDO approach to lunar micro/nano-satellite system design is presented, involving dimension reduction, dynamic response surface, system decoupling, and multiobjective alliance search. The optimization goal includes payload cost-effective ratio and satellite mass, and five reliability constraints are considered including satellite installation volume and battery cycles. Through identifying a dominant active subspace for high-dimensional inputs, the in-loop uncertainty quantification is greatly accelerated by about two orders of magnitude. A smooth and uniformly distributed Pareto front is therefore obtained to provide beneficial Pareto-optimal solutions, which indicates that the orbit altitude gathers around 200 km and the mission cycle is nearly 2.4 years. An optimal trade-off design has the minimum satellite mass of 8.95 kg and smaller cost-effective ratio. Compared with the deterministic optimization, the RBRDO approach is preferable for designing Moon imaging micro/nano-satellites of high reliability and robustness.

      PubDate: 2018-05-02T17:12:21Z
      DOI: 10.1016/j.actaastro.2018.04.017
      Issue No: Vol. 148 (2018)
       
  • Investigation of combustion characteristics in a scramjet combustor using
           a modified flamelet model
    • Authors: Guoyan Zhao; Mingbo Sun; Hongbo Wang; Hao Ouyang
      Pages: 32 - 40
      Abstract: Publication date: July 2018
      Source:Acta Astronautica, Volume 148
      Author(s): Guoyan Zhao, Mingbo Sun, Hongbo Wang, Hao Ouyang
      In this study, the characteristics of supersonic combustion inside an ethylene-fueled scramjet combustor equipped with multi-cavities were investigated with different injection schemes. Experimental results showed that the flames concentrated in the cavity and separated boundary layer downstream of the cavity, and they occupied the flow channel further enhancing the bulk flow compression. The flame structure in distributed injection scheme differed from that in centralized injection scheme. In numerical simulations, a modified flamelet model was introduced to consider that the pressure distribution is far from homogenous inside the scramjet combustor. Compared with original flamelet model, numerical predictions based on the modified model showed better agreement with the experimental results, validating the reliability of the calculations. Based on the modified model, the simulations with different injection schemes were analysed. The predicted flame agreed reasonably with the experimental observations in structure. The CO masses were concentrated in cavity and subsonic region adjacent to the cavity shear layer leading to intense heat release. Compared with centralized scheme, the higher jet mixing efficiency in distributed scheme induced an intense combustion in posterior upper cavity and downstream of the cavity. From streamline and isolation surfaces, the combustion at trail of lower cavity was depressed since the bulk flow downstream of the cavity is pushed down.

      PubDate: 2018-05-02T17:12:21Z
      DOI: 10.1016/j.actaastro.2018.04.005
      Issue No: Vol. 148 (2018)
       
  • Uncertainty dynamic theoretical analysis on ceramic thermal protection
           system using perturbation method
    • Authors: Jie Huang; Weixing Yao; Piao Li
      Pages: 41 - 47
      Abstract: Publication date: July 2018
      Source:Acta Astronautica, Volume 148
      Author(s): Jie Huang, Weixing Yao, Piao Li
      A two degree-of-freedom uncertainty dynamic theoretical model under the acoustic and base excitations was presented to analyze the uncertainty dynamic behaviors of thermal protection system (TPS) and the uncertainty dynamic strength of strain-isolation-pad (SIP). The tile and SIP are both simplified as the combination of a mass point, a linear spring and a damping element, and all the dynamic parameters obey the normal distribution. The probability distributions of responses were derived from adopting the perturbation method. The difference method is used to analyze the sensitivity of the mean responses to random parameters, and the reasonable sensitivity values are obtained under a difference step which is equal to the standard deviation of the random parameter. The probability distributions calculated by the uncertainty theoretical model match well with the Monte Carlo numerical results, so the accuracy of the uncertainty dynamic theoretical model is verified. The researches in this paper provide a theoretical foundation for studying the uncertainty dynamic behaviors of TPS, analyzing uncertainty dynamic strength of SIP and intensifying the integrity and security of TPS.

      PubDate: 2018-05-02T17:12:21Z
      DOI: 10.1016/j.actaastro.2018.04.027
      Issue No: Vol. 148 (2018)
       
  • Laplace ℓ1 Huber based cubature Kalman filter for attitude
           estimation of small satellite
    • Authors: Lu Cao; Dong Qiao; Xiaoqian Chen
      Pages: 48 - 56
      Abstract: Publication date: July 2018
      Source:Acta Astronautica, Volume 148
      Author(s): Lu Cao, Dong Qiao, Xiaoqian Chen
      This paper offers a solution to the attitude estimation of small satellite with the existence of model error and heavy-tailed noise, which is referred as to the Laplace ℓ1 Huber Based Kalman filter (ℓ1-HBKF). It employs the Laplace distribution and Huber based method to update the measurement covariance to deal with different types of model error or heavy-tailed noise for robust design. Then, the majorization minimization approach is discussed to improve the estimation accuracy by an iterative algorithm. In addition, the proposed ℓ1-HBKF is implemented in the Kalman filtering framework and is further extended by the strategy of fifth-degree cubature rule for high accuracy. Finally, the attitude estimation of small satellite is simulated and compared with conventional cubature Kalman filter (CKF), which can prove the accuracy and robustness of the proposed methods for the attitude estimation with low precision sensors.

      PubDate: 2018-05-02T17:12:21Z
      DOI: 10.1016/j.actaastro.2018.04.020
      Issue No: Vol. 148 (2018)
       
  • Performance evaluation of regenerative cooling/film cooling for
           hydrocarbon fueled scramjet engine
    • Authors: Jingying Zuo; Silong Zhang; Jiang Qin; Wen Bao; Naigang Cui
      Pages: 57 - 68
      Abstract: Publication date: July 2018
      Source:Acta Astronautica, Volume 148
      Author(s): Jingying Zuo, Silong Zhang, Jiang Qin, Wen Bao, Naigang Cui
      Thermal protection is considered to be a significant challenge for scramjet engine. In this paper, a combined cooling method which combines film cooling (F.C.) with regenerative cooling (R.C.) instead of single regenerative cooling for hydrocarbon fueled scramjet engine by using gaseous hydrocarbon fuel coming out of the cooling channel exit as film coolant has been proposed to increase the engine's flight Mach number without bringing extra fuel on board. One-dimensional (1-D) model of the combined cooling in terms of supersonic combustion in combustor and cracking reaction in regenerative cooling channels has been built and validated in order to evaluate its performance. The calculation results indicate that the engine wall temperature can be reduced significantly with R.C./F.C. and the flight Mach number of engine can be increased by nearly 8% under the stoichiometric fuel flow rate when material limit of the engine wall is set to be 1300 K. It is found that the effect of film inlet temperature on the cooling performance can be ignored because of the high total temperature of main flow, while the flow direction inside the cooing channel will have significant effects on the cooling performance of R.C./F.C.. The heat flux imposed on the engine wall is less uniform with “parallel flow” inside the cooling channel and the cooling performance is better and more sensitive to the change of film injection position under this condition. In addition, the cooling performance of R.C./F.C. present a very slight change when the number of the slots stays at a very low value and 2–3 film slots may be more practical and useful for the hydrocarbon fueled scramjet engine.

      PubDate: 2018-05-02T17:12:21Z
      DOI: 10.1016/j.actaastro.2018.04.037
      Issue No: Vol. 148 (2018)
       
  • Dynamic analysis of lunar lander during soft landing using explicit finite
           element method
    • Authors: Guang Zheng; Hong Nie; Jinbao Chen; Chuanzhi Chen; Heow Pueh Lee
      Pages: 69 - 81
      Abstract: Publication date: July 2018
      Source:Acta Astronautica, Volume 148
      Author(s): Guang Zheng, Hong Nie, Jinbao Chen, Chuanzhi Chen, Heow Pueh Lee
      In this paper, the soft-landing analysis of a lunar lander spacecraft under three loading case was carried out in ABAQUS, using the Explicit Finite Element method. To ensure the simulation result's accuracy and reliability, the energy and mass balance criteria of the model was presented along with the theory and calculation method, and the results were benchmarked with other software (LS-DYNA) to get a validated model. The results from three loading case showed that the energy and mass of the models were conserved during soft landing, which satisfies the energy and mass balance criteria. The overloading response, structure steady state, and the crushing stroke of this lunar lander all met the design requirements of the lunar lander. The buffer energy-absorbing properties in this model have a good energy-absorbing capability, in which up to 84% of the initial energy could be dissipated. The design parameters of the model could guide the design of future manned landers or larger lunar landers.

      PubDate: 2018-05-02T17:12:21Z
      DOI: 10.1016/j.actaastro.2018.04.014
      Issue No: Vol. 148 (2018)
       
  • Orbit estimation using a horizon detector in the presence of uncertain
           celestial body rotation and geometry
    • Authors: Amir Shakouri; Mahdi Hazrati Azad; Nima Assadian
      Pages: 82 - 88
      Abstract: Publication date: July 2018
      Source:Acta Astronautica, Volume 148
      Author(s): Amir Shakouri, Mahdi Hazrati Azad, Nima Assadian
      This paper presents an orbit estimation using non-simultaneous horizon detector measurements in the presence of uncertainties in the celestial body rotational velocity and its geometrical characteristics. The celestial body is modeled as a tri-axial ellipsoid with a three-dimensional force field. The non-simultaneous modelling provides the possibility to consider the time gap between horizon measurements. An unscented Kalman filter is used to estimate the spacecraft state variables and the geometric characteristics as well as the rotational velocity vector of the celestial body. A Monte-Carlo simulation is implemented to verify the results. Simulations showed that using non-simultaneous horizon vector measurements, the spacecraft state errors converge to zero even in the presence of an uncertain geometry and rotational velocity of the celestial body.

      PubDate: 2018-05-02T17:12:21Z
      DOI: 10.1016/j.actaastro.2018.04.021
      Issue No: Vol. 148 (2018)
       
  • Static and moving solid/gas interface modeling in a hybrid rocket engine
    • Authors: Alexandre Mangeot; Mame William-Louis; Philippe Gillard
      Pages: 89 - 98
      Abstract: Publication date: July 2018
      Source:Acta Astronautica, Volume 148
      Author(s): Alexandre Mangeot, Mame William-Louis, Philippe Gillard
      A numerical model was developed with CFD-ACE software to study the working condition of an oxygen-nitrogen/polyethylene hybrid rocket combustor. As a first approach, a simplified numerical model is presented. It includes a compressible transient gas phase in which a two-step combustion mechanism is implemented coupled to a radiative model. The solid phase from the fuel grain is a semi-opaque material with its degradation process modeled by an Arrhenius type law. Two versions of the model were tested. The first considers the solid/gas interface with a static grid while the second uses grid deformation during the computation to follow the asymmetrical regression. The numerical results are obtained with two different regression kinetics originating from ThermoGravimetry Analysis and test bench results. In each case, the fuel surface temperature is retrieved within a range of 5% error. However, good results are only found using kinetics from the test bench. The regression rate is found within 0.03 mm s−1 and average combustor pressure and its variation over time have the same intensity than the measurements conducted on the test bench. The simulation that uses grid deformation to follow the regression shows a good stability over a 10 s simulated time simulation.

      PubDate: 2018-05-02T17:12:21Z
      DOI: 10.1016/j.actaastro.2018.04.046
      Issue No: Vol. 148 (2018)
       
  • Speed-constrained three-axes attitude control using kinematic steering
    • Authors: Hanspeter Schaub; Scott Piggott
      Pages: 1 - 8
      Abstract: Publication date: June 2018
      Source:Acta Astronautica, Volume 147
      Author(s): Hanspeter Schaub, Scott Piggott
      Spacecraft attitude control solutions typically are torque-level algorithms that simultaneously control both the attitude and angular velocity tracking errors. In contrast, robotic control solutions are kinematic steering commands where rates are treated as the control variable, and a servo-tracking control subsystem is present to achieve the desired control rates. In this paper kinematic attitude steering controls are developed where an outer control loop establishes a desired angular response history to a tracking error, and an inner control loop tracks the commanded body angular rates. The overall stability relies on the separation principle of the inner and outer control loops which must have sufficiently different response time scales. The benefit is that the outer steering law response can be readily shaped to a desired behavior, such as limiting the approach angular velocity when a large tracking error is corrected. A Modified Rodrigues Parameters implementation is presented that smoothly saturates the speed response. A robust nonlinear body rate servo loop is developed which includes integral feedback. This approach provides a convenient modular framework that makes it simple to interchange outer and inner control loops to readily setup new control implementations. Numerical simulations illustrate the expected performance for an aggressive reorientation maneuver subject to an unknown external torque.

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

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

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

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

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

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

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

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

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

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

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

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

      PubDate: 2018-04-12T08:29:20Z
      DOI: 10.1016/j.actaastro.2018.03.042
      Issue No: Vol. 147 (2018)
       
  • Variable Mach number design approach for a parallel waverider with a
           wide-speed range based on the osculating cone theory
    • Authors: Zhen-tao Zhao; Wei Huang; Shi-Bin Li; Tian-Tian Zhang; Li Yan
      Pages: 163 - 174
      Abstract: Publication date: June 2018
      Source:Acta Astronautica, Volume 147
      Author(s): Zhen-tao Zhao, Wei Huang, Shi-Bin Li, Tian-Tian Zhang, Li Yan
      In the current study, a variable Mach number waverider design approach has been proposed based on the osculating cone theory. The design Mach number of the osculating cone constant Mach number waverider with the same volumetric efficiency of the osculating cone variable Mach number waverider has been determined by writing a program for calculating the volumetric efficiencies of waveriders. The CFD approach has been utilized to verify the effectiveness of the proposed approach. At the same time, through the comparative analysis of the aerodynamic performance, the performance advantage of the osculating cone variable Mach number waverider is studied. The obtained results show that the osculating cone variable Mach number waverider owns higher lift-to-drag ratio throughout the flight profile when compared with the osculating cone constant Mach number waverider, and it has superior low-speed aerodynamic performance while maintaining nearly the same high-speed aerodynamic performance.

      PubDate: 2018-05-02T17:12:21Z
      DOI: 10.1016/j.actaastro.2018.04.008
      Issue No: Vol. 147 (2018)
       
  • Hybrid Smith predictor and phase lead based divergence compensation for
           hardware-in-the-loop contact simulation with measurement delay
    • Authors: Chenkun Qi; Feng Gao; Xianchao Zhao; Qian Wang; Anye Ren
      Pages: 175 - 182
      Abstract: Publication date: June 2018
      Source:Acta Astronautica, Volume 147
      Author(s): Chenkun Qi, Feng Gao, Xianchao Zhao, Qian Wang, Anye Ren
      On the ground the hardware-in-the-loop (HIL) simulation is a good approach to test the contact dynamics of spacecraft docking process in space. Unfortunately, due to the time delay in the system the HIL contact simulation becomes divergent. However, the traditional first-order phase lead compensation approach still result in a small divergence for the pure time delay. The serial Smith predictor and phase lead compensation approach proposed by the authors recently will lead to an over-compensation and an obvious convergence. In this study, a hybrid Smith predictor and phase lead compensation approach is proposed. The hybrid Smith predictor and phase lead compensation can achieve a higher simulation fidelity with a little convergence. The phase angle of the compensator is analyzed and the stability condition of the HIL simulation system is given. The effectiveness of the proposed compensation approach is tested by simulations on an undamped elastic contact process.

      PubDate: 2018-05-02T17:12:21Z
      DOI: 10.1016/j.actaastro.2018.04.010
      Issue No: Vol. 147 (2018)
       
  • Reliability analysis of multicellular system architectures for low-cost
           satellites
    • Authors: A.O. Erlank; C.P. Bridges
      Pages: 183 - 194
      Abstract: Publication date: June 2018
      Source:Acta Astronautica, Volume 147
      Author(s): A.O. Erlank, C.P. Bridges
      Multicellular system architectures are proposed as a solution to the problem of low reliability currently seen amongst small, low cost satellites. In a multicellular architecture, a set of independent k-out-of-n systems mimic the cells of a biological organism. In order to be beneficial, a multicellular architecture must provide more reliability per unit of overhead than traditional forms of redundancy. The overheads include power consumption, volume and mass. This paper describes the derivation of an analytical model for predicting a multicellular system's lifetime. The performance of such architectures is compared against that of several common forms of redundancy and proven to be beneficial under certain circumstances. In addition, the problem of peripheral interfaces and cross-strapping is investigated using a purpose-developed, multicellular simulation environment. Finally, two case studies are presented based on a prototype cell implementation, which demonstrate the feasibility of the proposed architecture.

      PubDate: 2018-05-02T17:12:21Z
      DOI: 10.1016/j.actaastro.2018.04.006
      Issue No: Vol. 147 (2018)
       
  • Initiation characteristics of wedge-induced oblique detonation waves in
           turbulence flows
    • Authors: Moyao Yu; Shikun Miao
      Pages: 195 - 204
      Abstract: Publication date: June 2018
      Source:Acta Astronautica, Volume 147
      Author(s): Moyao Yu, Shikun Miao
      The initiation features of wedge-induced oblique detonation waves (ODWs) in supersonic turbulence flows are studied with numerical simulations based on the SST k-ω model. The results show that the ignition delays are smaller in turbulence flows which results in a decrease in the initiation lengths of ODWs, and the initiation length decreases with the increase of the turbulence intensity. The effects of turbulence on the initiation limits of ODWs are analyzed with the energetic limit and the kinetic limit. It is shown that the initiation limit is not affected by the energetic limit, but affected by the kinetic limit. Because the ignition delay decreases in a turbulence flow, the kinetic limit is more easily to be fulfilled. Therefore, the initiation limit decreases with the increase of the turbulence intensity, that is to say, ODWs in strongly turbulent flows are more easily to be initiated. Besides, the transition structures of ODWs are investigated and the results show that for the same inflow condition, transition structures of ODWs in strongly turbulent flows are smooth while it is abrupt in an inviscid or slightly turbulent flow, and the reasons are discussed.

      PubDate: 2018-05-02T17:12:21Z
      DOI: 10.1016/j.actaastro.2018.04.022
      Issue No: Vol. 147 (2018)
       
  • Satellite Vibration Testing: Angle optimisation method to Reduce
           Overtesting
    • Authors: Charly Knight; Marcello Remedia; Guglielmo S. Aglietti; Guy Richardson
      Pages: 205 - 218
      Abstract: Publication date: June 2018
      Source:Acta Astronautica, Volume 147
      Author(s): Charly Knight, Marcello Remedia, Guglielmo S. Aglietti, Guy Richardson
      Spacecraft overtesting is a long running problem, and the main focus of most attempts to reduce it has been to adjust the base vibration input (i.e. notching). Instead this paper examines testing alternatives for secondary structures (equipment) coupled to the main structure (satellite) when they are tested separately. Even if the vibration source is applied along one of the orthogonal axes at the base of the coupled system (satellite plus equipment), the dynamics of the system and potentially the interface configuration mean the vibration at the interface may not occur all along one axis much less the corresponding orthogonal axis of the base excitation. This paper proposes an alternative testing methodology in which the testing of a piece of equipment occurs at an offset angle. This Angle Optimisation method may have multiple tests but each with an altered input direction allowing for the best match between all specified equipment system responses with coupled system tests. An optimisation process that compares the calculated equipment RMS values for a range of inputs with the maximum coupled system RMS values, and is used to find the optimal testing configuration for the given parameters. A case study was performed to find the best testing angles to match the acceleration responses of the centre of mass and sum of interface forces for all three axes, as well as the von Mises stress for an element by a fastening point. The angle optimisation method resulted in RMS values and PSD responses that were much closer to the coupled system when compared with traditional testing. The optimum testing configuration resulted in an overall average error significantly smaller than the traditional method. Crucially, this case study shows that the optimum test campaign could be a single equipment level test opposed to the traditional three orthogonal direction tests.

      PubDate: 2018-05-02T17:12:21Z
      DOI: 10.1016/j.actaastro.2018.04.004
      Issue No: Vol. 147 (2018)
       
  • Boundary control of anti-symmetric vibration of satellite with flexible
           appendages in planar motion with exponential stability
    • Authors: Hossein Kaviani Rad; Hassan Salarieh; Aria Alasty; Ramin Vatankhah
      Pages: 219 - 230
      Abstract: Publication date: June 2018
      Source:Acta Astronautica, Volume 147
      Author(s): Hossein Kaviani Rad, Hassan Salarieh, Aria Alasty, Ramin Vatankhah
      In this research, we have investigated the planar maneuver of a flexible satellite with appendages anti-symmetric vibration. The hybrid governing equations are comprised of coupled partial and ordinary differential equations which are derived by employing Hamilton's principle. In this paper, control goals are the tracking desired pitch angle along with the flexible appendages vibration suppression simultaneously by using only one control torque which is applied to the central hub. The boundary control is proposed to fulfill these control aims; furthermore, this boundary control ensures that spillover instability phenomenon is eliminated, and in-domain sensors and actuators implement are excluded. Indeed, the proposed boundary control is able to stabilize an infinite number of vibration modes, which is one of the important benefits of the proposed control when it is considered that different factors including external disturbances and even the satellite maneuver can excite the various vibration modes of the flexible appendages and consequently the excitement of the high order vibration modes will be possible. Lyapunov's direct method is used to prove the exponential stability; moreover, this Proof is achieved in absence of any damping effect in modeling the vibrations of flexible appendages. In addition, the procedure for finding the boundary control coefficients which ensures the exponential stability is provided. Eventually, numerical simulations are presented to illustrate the effectiveness of the proposed boundary control.

      PubDate: 2018-05-02T17:12:21Z
      DOI: 10.1016/j.actaastro.2018.03.050
      Issue No: Vol. 147 (2018)
       
  • Numerical form-finding method for large mesh reflectors with elastic rim
           trusses
    • Authors: Dongwu Yang; Yiqun Zhang; Peng Li; Jingli Du
      Pages: 241 - 250
      Abstract: Publication date: June 2018
      Source:Acta Astronautica, Volume 147
      Author(s): Dongwu Yang, Yiqun Zhang, Peng Li, Jingli Du
      Traditional methods for designing a mesh reflector usually treat the rim truss as rigid. Due to large aperture, light weight and high accuracy requirements on spaceborne reflectors, the rim truss deformation is indeed not negligible. In order to design a cable net with asymmetric boundaries for the front and rear nets, a cable-net form-finding method is firstly introduced. Then, the form-finding method is embedded into an iterative approach for designing a mesh reflector considering the elasticity of the supporting rim truss. By iterations on form-findings of the cable-net based on the updated boundary conditions due to the rim truss deformation, a mesh reflector with a fairly uniform tension distribution in its equilibrium state could be finally designed. Applications on offset mesh reflectors with both circular and elliptical rim trusses are illustrated. The numerical results show the effectiveness of the proposed approach and that a circular rim truss is more stable than an elliptical rim truss.

      PubDate: 2018-05-02T17:12:21Z
      DOI: 10.1016/j.actaastro.2018.04.007
      Issue No: Vol. 147 (2018)
       
  • Nonlinear convective flows in a two-layer system under the action of
           spatial temperature modulation of heat release/consumption at the
           interface
    • Authors: Ilya B. Simanovskii; Antonio Viviani; Frank Dubois
      Pages: 297 - 315
      Abstract: Publication date: June 2018
      Source:Acta Astronautica, Volume 147
      Author(s): Ilya B. Simanovskii, Antonio Viviani, Frank Dubois
      An influence of a spatial temperature modulation of the interfacial heat release/consumption on nonlinear convective flows in the 47v2 silicone oil - water system, is studied. Rigid heat-insulated lateral walls, corresponding to the case of closed cavities, have been considered. Transitions between the flows with different spatial structures, have been investigated. It is shown that the spatial modulation can change the sequence of bifurcations and lead to the appearance of specific steady and oscillatory flows in the system.

      PubDate: 2018-05-02T17:12:21Z
      DOI: 10.1016/j.actaastro.2018.03.032
      Issue No: Vol. 147 (2018)
       
  • A comprehensive assessment of collision likelihood in Geosynchronous Earth
           Orbit
    • Authors: D.L. Oltrogge; S. Alfano; C. Law; A. Cacioni; T.S. Kelso
      Pages: 316 - 345
      Abstract: Publication date: June 2018
      Source:Acta Astronautica, Volume 147
      Author(s): D.L. Oltrogge, S. Alfano, C. Law, A. Cacioni, T.S. Kelso
      Knowing the likelihood of collision for satellites operating in Geosynchronous Earth Orbit (GEO) is of extreme importance and interest to the global community and the operators of GEO spacecraft. Yet for all of its importance, a comprehensive assessment of GEO collision likelihood is difficult to do and has never been done. In this paper, we employ six independent and diverse assessment methods to estimate GEO collision likelihood. Taken in aggregate, this comprehensive assessment offer new insights into GEO collision likelihood that are within a factor of 3.5 of each other. These results are then compared to four collision and seven encounter rate estimates previously published. Collectively, these new findings indicate that collision likelihood in GEO is as much as four orders of magnitude higher than previously published by other researchers. Results indicate that a collision is likely to occur every 4 years for one satellite out of the entire GEO active satellite population against a 1 cm RSO catalogue, and every 50 years against a 20 cm RSO catalogue. Further, previous assertions that collision relative velocities are low (i.e., <1 km/s) in GEO are disproven, with some GEO relative velocities as high as 4 km/s identified. These new findings indicate that unless operators successfully mitigate this collision risk, the GEO orbital arc is and will remain at high risk of collision, with the potential for serious follow-on collision threats from post-collision debris when a substantial GEO collision occurs.

      PubDate: 2018-05-02T17:12:21Z
      DOI: 10.1016/j.actaastro.2018.03.017
      Issue No: Vol. 147 (2018)
       
  • Elements of ESA’s policy on space and security
    • Authors: Christina Giannopapa; Maarten Adriaensen; Ntorina Antoni; Kai-Uwe Schrogl
      Pages: 346 - 349
      Abstract: Publication date: June 2018
      Source:Acta Astronautica, Volume 147
      Author(s): Christina Giannopapa, Maarten Adriaensen, Ntorina Antoni, Kai-Uwe Schrogl
      In the past decade Europe has been facing rising security threats, ranging from climate change, migrations, nearby conflicts and crises, to terrorism. The demand to tackle these critical challenges is increasing in Member States. Space is already contributing, and could further contribute with already existing systems and future ones. The increasing need for security in Europe and for safety and security of Europe’s space activities has led to a growing number of activities in ESA in various domains. It has also driven new and strengthened partnerships with security stakeholders in Europe. At the European level, ESA is collaborating closely with the main European institutions dealing with space security. In addition, as an organisation ESA has evolved to conduct security-related projects and programmes and to address the threats to its own activities, thereby securing the investments of the Member States. Over the past years the Agency has set up a comprehensive regulatory framework in order to be able to cope with security related requirements. Over the past years, ESA has increased its exchanges with its Member States. The paper presents main elements of the ESA’s policy on space and security. It introduces the current European context for space and security, the European goals in this domain and the specific objectives to which the Agency intends to contribute. Space and security in the ESA context is set out under two components: a) security from space and b) security in space, including the security of ESA’s own activities (corporate security and the security of ESA’s space missions). Subsequently, ESA’s activities are elaborated around these two pillars, composed of different activities conducted in the most appropriate frameworks and in coordination with the relevant stakeholders and shareholders.

      PubDate: 2018-05-02T17:12:21Z
      DOI: 10.1016/j.actaastro.2018.02.044
      Issue No: Vol. 147 (2018)
       
  • An integrated control scheme for space robot after capturing
           non-cooperative target
    • Authors: Mingming Wang; Jianjun Luo; Jianping Yuan; Ulrich Walter
      Pages: 350 - 363
      Abstract: Publication date: June 2018
      Source:Acta Astronautica, Volume 147
      Author(s): Mingming Wang, Jianjun Luo, Jianping Yuan, Ulrich Walter
      How to identify the mass properties and eliminate the unknown angular momentum of space robotic system after capturing a non-cooperative target is of great challenge. This paper focuses on designing an integrated control framework which includes detumbling strategy, coordination control and parameter identification. Firstly, inverted and forward chain approaches are synthesized for space robot to obtain dynamic equation in operational space. Secondly, a detumbling strategy is introduced using elementary functions with normalized time, while the imposed end-effector constraints are considered. Next, a coordination control scheme for stabilizing both base and end-effector based on impedance control is implemented with the target's parameter uncertainty. With the measurements of the forces and torques exerted on the target, its mass properties are estimated during the detumbling process accordingly. Simulation results are presented using a 7 degree-of-freedom kinematically redundant space manipulator, which verifies the performance and effectiveness of the proposed method.

      PubDate: 2018-05-02T17:12:21Z
      DOI: 10.1016/j.actaastro.2018.04.016
      Issue No: Vol. 147 (2018)
       
  • Hong-Ou-Mandel Gravitational Wave Space spectrometER – HOMER mission
    • Authors: Clovis Jacinto de Matos; Martin Tajmar
      Pages: 364 - 373
      Abstract: Publication date: June 2018
      Source:Acta Astronautica, Volume 147
      Author(s): Clovis Jacinto de Matos, Martin Tajmar
      Michelson type gravitational wave detectors measure the strain caused by gravitational waves on the interferometer's arms. Gravitational waves can also cause the rotation of photon's linear polarization vector, thus disturbing the interference of entangled photons in Hong-Ou-Mandel (HOM) interferometers. Here one uses that physical phenomenon to devise a spectrometer for gravitational waves through the implementation of a Hong-Ou-Mandel interferometer in Earth geostationary orbit with a constellation of three different spacecraft in accurate formation flight. We call this mission, the Hong-Ou-Mandel Gravitational Waves Space SpectrometER (HOMER). HOMER will cover the part of the gravitational wave spectrum with wavelengths around λ = 10 5 km, which falls between the long wavelength detection range of LISA, around λ = 10 6 km, and of ground based detectors like LIGO, around λ = 10 3 km. With respect to Michelson type detectors, the proposed concept for the detection and spectral analysis of gravitational waves has the advantage of operating without the need of drag free satellites, however it requires a relative precision of the attitude between satellites of the order of the gravitational waves amplitude δ θ / θ ∼ h ∼ 10 − 20 , which makes the architecture of the HOMER mission as challenging as the Michelson type space detectors. The difficulty being however transferred from the monitoring of the relative distance between spacecraft (for Michelson antennas) to their relative attitude. By focusing on photons polarization instead of photons phase one can measure the spectrum of the detected gravitational signal. As a bonus, the proposed instrument could also investigate the influence of spacetime curvature on photons quantum entanglement, thus experimentally peering into the relation between general relativity and quantum mechanics, which is currently a subject of high interest in theoretical physics. This paper will describe the HOMER mission concept in general and the main elements of the payload and spacecraft design in particular.

      PubDate: 2018-05-02T17:12:21Z
      DOI: 10.1016/j.actaastro.2018.03.040
      Issue No: Vol. 147 (2018)
       
  • Effects of atomic oxygen on titanium dioxide thin film
    • Authors: Naoki Shimosako; Yukihiro Hara; Kazunori Shimazaki; Eiji Miyazaki; Hiroshi Sakama
      Pages: 1 - 6
      Abstract: Publication date: May 2018
      Source:Acta Astronautica, Volume 146
      Author(s): Naoki Shimosako, Yukihiro Hara, Kazunori Shimazaki, Eiji Miyazaki, Hiroshi Sakama
      In low earth orbit (LEO), atomic oxygen (AO) has shown to cause degradation of organic materials used in spacecrafts. Similar to other metal oxides such as SiO2, Al2O3 and ITO, TiO2 has potential to protect organic materials. In this study, the anatese-type TiO2 thin films were fabricated by a sol-gel method and irradiated with AO. The properties of TiO2 were compared using mass change, scanning electron microscope (SEM), atomic force microscope (AFM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), transmittance spectra and photocatalytic activity before and after AO irradiation. The results indicate that TiO2 film was hardly eroded and resistant against AO degradation. AO was shown to affects only the surface of a TiO2 film and not the bulk. Upon AO irradiation, the TiO2 films were slightly oxidized. However, these changes were very small. Photocatalytic activity of TiO2 was still maintained in spite of slight decrease upon AO irradiation, which demonstrated that TiO2 thin films are promising for elimination of contaminations outgassed from a spacecraft's materials.

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

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

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

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

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

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

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

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

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

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

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

      PubDate: 2018-04-12T08:29:20Z
      DOI: 10.1016/j.actaastro.2018.02.034
      Issue No: Vol. 146 (2018)
       
  • Effects of gas liquid ratio on the atomization characteristics of
           gas-liquid swirl coaxial injectors
    • Authors: Zhongtao Kang; Qinglian Li; Jiaqi Zhang; Peng Cheng
      Abstract: Publication date: Available online 22 February 2018
      Source:Acta Astronautica
      Author(s): Zhongtao Kang, Qinglian Li, Jiaqi Zhang, Peng Cheng
      To understand the atomization characteristics and atomization mechanism of the gas-liquid swirl coaxial (GLSC) injector, a back-lighting photography technique has been employed to capture the instantaneous spray images with a high speed camera. The diameter and velocity of the droplets in the spray have been characterized with a Dantec Phase Doppler Anemometry (PDA) system. The effects of gas liquid ratio (GLR) on the spray pattern, Sauter mean diameter (SMD), diameter-velocity distribution and mass flow rate distribution were analyzed and discussed. The results show that the atomization of the GLSC injector is dominated by the film breakup when the GLR is small, and violent gas-liquid interaction when the GLR is large enough. The film breakup dominated spray can be divided into gas acceleration region and film breakup region while the violent gas-liquid interaction dominated spray can be divided into the gas acceleration region, violent gas-liquid interaction region and big droplets breakup region. The atomization characteristics of the GLSC injector is significantly influenced by the GLR. From the point of atomization performance, the increase of GLR has positive effects. It decreases the global Sauter mean diameter (GSMD) and varies the SMD distribution from a hollow cone shape (GLR = 0) to an inverted V shape, and finally slanted N shape. However, from the point of spatial distribution, the increase of GLR has negative effects, because the mass flow rate distribution becomes more nonuniform.

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