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Acta Astronautica
Journal Prestige (SJR): 0.758
Citation Impact (citeScore): 2
Number of Followers: 434  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0094-5765
Published by Elsevier Homepage  [3183 journals]
  • Iterative trajectory learning for highly accurate optical satellite
           tracking systems
    • Abstract: Publication date: Available online 17 July 2019Source: Acta AstronauticaAuthor(s): Thomas Riel, Andreas Sinn, Christian Schwaer, Martin Ploner, Georg Schitter This paper investigates the tracking accuracy of an optical telescope system used for satellite tracking and laser ranging applications. The investigated system uses a high precision motion controller and a pointing model based on spherical harmonics to achieve high accuracy. To overcome the limitations due to local pointing model inaccuracies and dynamic effects during tracking, an iterative trajectory learning algorithm is proposed. The implementation, as well as the stability analysis of the proposed concept is presented. Satellite tracking experiments are conducted to verify the accuracy of the proposed system. Utilizing the proposed iterative trajectory learning concept, the tracking error is reduced by a factor of 11 and is ultimately limited by the uncertainty of the orbit prediction.
       
  • Autonomy and operational concept for self-removal of spacecraft: Status
           detection, removal triggering and passivation
    • Abstract: Publication date: Available online 14 July 2019Source: Acta AstronauticaAuthor(s): Alexandra Wander, Konstantinos Konstantinidis, Roger Förstner, Philipp Voigt The growing population of space debris is posing a threat to future spacecraft in Earth orbit. The technology for self-removal of spacecraft, TeSeR, is an innovative project of eleven European partners coordinated by Airbus Defense & Space within the HORIZON2020 framework of the European Union with the goal to develop a removal module that can be carried into orbit by future spacecraft of any size and mass into any orbit, interconnected only by a standardized interface. At early 2019, a prototype shall already have demonstrated the main functions on ground. This paper introduces the mission and operational concept as well as the functional architecture and presents the autonomy considerations for the design of the overall post-mission disposal module focusing on three areas: the status detection of the host spacecraft by the developed post-mission disposal module, the removal triggering by the post-mission disposal module in case of lost link to ground station and malfunctioning host spacecraft as well as the passivation options of the host spacecraft and the post-mission disposal module itself.
       
  • Realization of methane-air continuous rotating detonation wave
    • Abstract: Publication date: November 2019Source: Acta Astronautica, Volume 164Author(s): Hao-Yang Peng, Wei-Dong Liu, Shi-Jie Liu, Hai-Long Zhang, Wei-Yong Zhou Methane-air Continuous Rotating Detonation (CRD) has been firstly achieved in this paper in the hollow chamber with a Laval nozzle, and the diameter of the chamber is just 100 mm. The contraction ratio of the Laval nozzle is a key factor for the CRD realization. CRD can only be obtained when the contraction ratio is no less than 4, but its ER operating range decreases in the increase of contraction ratio from 4 to 10. For all the success cases, the average propagation frequency and velocity are in the ranges of 5.32–5.65 kHz and 1670.48–1774.10 m/s, respectively, and the velocity deficits are less than 10%. Based on the high-speed photography images, the approach of chemiluminescence intensity integral is proposed in this paper, and the propagation characteristics of the flame are analyzed quantitatively. The propagation velocities of the flame and shock wave are agreed well with each other, indicating that the typical feature of detonation wave, i.e., the coupling of the flame and the shock wave, is verified quantitatively.
       
  • Electric sail displaced orbit control with solar wind uncertainties
    • Abstract: Publication date: September 2019Source: Acta Astronautica, Volume 162Author(s): Lorenzo Niccolai, Alessandro Anderlini, Giovanni Mengali, Alessandro A. Quarta The working principle of the Electric Solar Wind Sail, an innovative propellantless propulsion system proposed in 2004, is based on the electrostatic interaction between a spinning grid of tethers, kept at a high positive potential, and the incoming ions from the solar wind. Similar to the well-known solar sail concept, the E-sail could simplify the feasibility of advanced (deep space) missions which would otherwise require a significative amount of propellant, if enabled by conventional thrusters. However, the intrinsic variability of the solar wind properties makes accurate trajectory tracking a difficult task, since the perturbations of the solar wind dynamic pressure have the same order of magnitude as their mean value. To circumvent such a problem, in a recent study the plasma dynamic pressure was modelled as a random variable with a gamma probability density function and the sail grid voltage was suggested to be varied as a function of the instantaneous value of the solar wind properties. The aim of this paper is to improve those results, by discussing a more accurate statistical model of the solar wind dynamic pressure, which is used in the numerical simulations to estimate the actual impact of the solar wind uncertainties on the spacecraft heliocentric trajectory. In particular, the paper proposes a control law that is able to accurately track a nominal, non-Keplerian orbit.
       
  • Modifying the constant coefficients of Eddy-dissipation concept model in
           moderate or intense low-oxygen dilution combustion using inverse problem
           methodology
    • Abstract: Publication date: September 2019Source: Acta Astronautica, Volume 162Author(s): Mohammad Mansourian, Reza Kamali There are many differences between combustion modeling of conventional and moderate or intense low oxygen dilution combustion. Among them, turbulent-chemistry interaction modeling is an open field of study. Studies show that the eddy dissipation concept model is very suitable for modeling of moderate or intense low-oxygen dilution combustion but the constants of eddy dissipation concept should be modified for better prediction.In this work, the inverse problem methodology is applied to predict the optimum volume fraction and time scale constants of eddy dissipation concept in order to enhance the accuracy of the numerical prediction of moderate or intense low-oxygen dilution combustion in a jet-in-hot-coflow burner. For this purpose, computational fluid dynamics modeling approach, considering Reynolds-averaged Navier-Stokes equations and detailed reaction mechanism, is used in the openfoam package. The results show that the values of 0.48 and 1.9 are suitable for time scale and volume fraction constants, respectively, as the values leading to the highest results in comparison to experimental data. After validating the numerical results, the effect of sinusoidal variations in the preheated co-flow temperature on the flame characteristics of Methane-Hydrogen blended fuel, to produce more complete moderate or intense low-oxygen dilution combustion regime, was considered. The results show that in moderate or intense low-oxygen dilution combustion regime, the peak temperature under sinusoidal variations in the preheated co-flow temperature is constant as compared to typically moderate or intense low-oxygen dilution combustion; but the amount of CO2 and H2O species, as well as OH and CH2O intermediate species, are increased and CO emission is reduced.
       
  • Novel numerical boundary condition for simulating plasma actuator effects
           on rocket roll rate
    • Abstract: Publication date: September 2019Source: Acta Astronautica, Volume 162Author(s): S. Sumanik, J. Etele, R. Pimentel A modified boundary condition is proposed which does not require alteration to a standard Navier-Stokes solver and which can be used to simulate the effects of Dielectric Barrier Discharge (DBD) plasma actuators. This boundary condition is used to examine the effect of actuator location and freestream velocity on the normal force (per unit span) generated by a DBD actuator operating on one side of a typical sounding rocket fin. A position between 35% and 50% chord is found to produce the largest force over a range of freestream velocities between 10 m/s and 90 m/s. This force increases with increasing speed up to approximately 45 m/s after which it remains relatively constant. Applying this force on a three fin sounding rocket for approxitely 7 s before apogee results in a predicted roll rate of approximately 3 RPM.
       
  • Survey on key techniques of rocket-based combined-cycle engine in ejector
           mode
    • Abstract: Publication date: Available online 13 July 2019Source: Acta AstronauticaAuthor(s): Zeyu Dong, Mingbo Sun, Zhenguo Wang, Jian Chen, Zun Cai A rocket-based combined-cycle (RBCC) engine synthetically integrates a traditional rocket engine with an airbreathing engine, effectively combining both advantages of high thrust-to-weight ratio and high specific impulse. It has become one of the most efficient propulsion systems for future reusable space transportation vehicles. In engineering practice, the engine performance during ejector mode plays a significant role in determining the efficiency of the whole RBCC propulsion system. This study aims to provide a summary report on the recent research progress on the RBCC engine in ejector mode. Firstly, the basic operating principle of the RBCC ejector mode is introduced and its ideal thermodynamic cycle process is theoretically analyzed. Secondly, the influencing factors on RBCC engine performance in ejector mode are specifically investigated, including rocket ejector parameters, geometry configurations of RBCC engine, secondary fuel injection schemes, flight Mach number and altitude. Thirdly, the research progress on key techniques of the RBCC ejector mode in recent two decades is reviewed from four aspects, namely the combustion organization, the mixing enhancement, the resistance to backpressure and the ejector/ramjet mode transition. Finally, some suggestions for the future work on the RBCC ejector mode are proposed.
       
  • Comparison of HTP catalyst performance for different internal monolith
           structures
    • Abstract: Publication date: Available online 12 July 2019Source: Acta AstronauticaAuthor(s): Robert-Jan Koopmans, Varun Reddy Nandyala, Sara Pavesi, Yann Batonneau, Romain Beauchet, Corentin Maleix, Martin Schwentenwein, Manfred Spitzbart, Altan Alpay Altun, Carsten Scharlemann A new technology for the manufacturing of 3D-printed ceramic catalyst support structures enables further optimisation of the catalyst, including the size and the internal geometry. An important design consideration for catalysts used in monopropellant thrusters is the size for a given design thrust level. A too small size may lead to only a partly decomposition of the incoming propellant. A too large size may lead to unnecessary heat loss to the environment and an excessive pressure drop. Both cases will result in a reduced performance. In the current investigation, four catalyst designs were subjected to a range of mass flow rates, thereby varying the average residence time in the chamber. It was found that shorter residence times lead to higher average chamber temperatures. This suggests that the catalyst is too large. Although the results for each internal design cannot be compared directly to each other, the convex tetrahedron design seems to be slightly better.
       
  • Impact probability computation for NEO resonant returns through a
           polynomial representation of the Line of Variations
    • Abstract: Publication date: Available online 12 July 2019Source: Acta AstronauticaAuthor(s): Marcello Sciarra, Matteo Losacco, Daniele Santeramo, Pierluigi Di Lizia A differential algebra based representation and propagation of the Line of Variations for Near Earth Objects impact monitoring is presented in this paper. The Line of Variations is described at the initial epoch by a high-order polynomial that is propagated forward in time. An Automatic Domain Splitting algorithm is embedded in the numerical integrator, in such a way that when the polynomials truncation error becomes too large, the line is split as many times as necessary to meet accuracy requirements. The Line of Variations is propagated forward in time until an intersection with a properly defined target plane occurs for all the generated subdomains. The subdomains are then projected onto the target plane to compute the impact probability by numerically integrating an associated one-dimensional probability density function. The proposed approach is applied to several test-cases to assess the performance of the method for the different possible shapes of the initial confidence region. Starting from a case of direct encounter, the technique is tested up to the case of a resonant return, which features critical nonlinearities.
       
  • Personal value diversity in confinement and isolation: Pilot study results
           from the 180-day CELSS integration experiment
    • Abstract: Publication date: Available online 12 July 2019Source: Acta AstronauticaAuthor(s): Qianying Ma, Gro M. Sandal, Ruilin Wu, Jianghui Xiong, Yinghui Li, Zi Xu, Li He, Yang Liu As a major life-challenging event, being confined in an isolated environment with a small group for an extended period may make individuals re-evaluate their personal values. The present study aimed to understand the changes in personal values among Chinese crew members (n = 4) participating in a 180-day isolation and confinement experiment. The whole experiment was divided into three phases: the first and third phases followed Earth's 24-h cycle, and the second phase followed Mars' 24-h and 40-min cycle. The Portrait Values Questionnaire (PVQ) was administered once per month. Anecdotal reports provided supplementary information to further understand the value changes. The results showed a linear decrease over time in the importance attributed to power. The mean scores on benevolence during the third phase of the experiment were significantly higher than those of the first phase, while the mean scores on universalism were significantly lower in the third phase. Taken together, the findings suggest that group members may adjust personal values to accommodate living in a small group in an isolated and confinement environment over an extended period.
       
  • A centrifuge-based flight simulator: Optimization of a baseline
           acceleration profile based on the motion sickness incidence
    • Abstract: Publication date: Available online 12 July 2019Source: Acta AstronauticaAuthor(s): Rafał Lewkowicz Simulator sickness is a common problem when using centrifuge-based flight simulator. During centrifuge-based training, achieving a G-baseline level and returning to a complete stop after each G-profile still cause unpleasant sensations and motion sickness. The aim of this study was to determine the optimal G-baseline level and the optimal approach motion cueing when the centrifuge-based flight simulator achieved and returned from this G-baseline level. A model of motion sickness incidence (MSI) was used to elucidate the optimal solution of motion cueing. The motion stimuli were computed based on an inverse kinematics model of the centrifuge-based motion system. For each analysed G-baseline profile, there were stimuli that provoked the occurrence of MSI. These stimuli were directly proportional to the applied G-onset rate. There was found the optimal G-baseline level at 1.41 G and optimal motion cueing (0.05 G s−1) that gave the minimal MSI. Up to 41% and 32% a reduction in the MSI could be obtained during the achievement and return from this G-baseline level, respectively. In order to confirm obtained results further studies should be performed with participants in an actual centrifuge-based flight simulator.
       
  • The influence of external magnetic field on the plume of vacuum arc
           thruster
    • Abstract: Publication date: Available online 11 July 2019Source: Acta AstronauticaAuthor(s): Qimeng Xia, Ningfei Wang, Xianming Wu, Kan Xie, Song Bai, Zun Zhang, Liang Ren The vacuum arc thruster (VAT) is considered to be a potential micro-thruster because of its simple structure and high specific impulse. The plume downstream from the cathode spot region of a co-axial type thruster with external magnetic field is analyzed by numerical simulation. Plasma velocity, temperature and density are used to represent the influence of the cathode spot region. When the magnetic field is applied, the plume is significantly affected even at the intensity of 0.03 T. Most ions move around the magnetic induction line, forming a concentrated beam. The beam expansion angle and the ion backflow are controlled therefore. The ion beam total velocity increment is about 20% in the plume while the beam direction is determined significantly by the cathode spot position and the external magnetic field. The deflection angle of the magnetic induction line in the near-field region will bring axial velocity loss. The magnetic field intensity affects little on the ion beam velocity increment while the influence of the initial plasma density change caused by the magnetic field cannot be ignored. Ground experiment data show a large increment of ion beam velocity between the conditions with and without the magnetic field (0.03 T and 0 T), but nearly no obvious variation from 0 to 15 cm downstream of the thruster in the former condition.
       
  • An experimental and modelling study of heat loads on a subscale methane
           rocket motor
    • Abstract: Publication date: Available online 10 July 2019Source: Acta AstronauticaAuthor(s): Ye Hong, Zhanyi Liu, Simona Silvestri, Maria P. Celano, Oskar J. Haidn, Zhendong Yu Given growing competition in the business space launch market, more researchers are evaluating the merit of methane as a potential propellant. In this study, a rocket combustion chamber with a single coaxial shear injector is tested. Gaseous oxygen and gaseous methane are employed in the hot firing tests at 2 MPa and a mass ratio of oxidizer to fuel of 2.65. Along the chamber axis, the wall temperatures are recorded; an inverse heat conduction approach forms the basis of the wall heat flux calculations. By applying the CFD code ANSYS Fluent, numerical simulations offer a superior analysis of the results. To model turbulent combustion, the eddy dissipation concept model is employed. Prior to additional analysis, mesh independency has been verified with the objective of comparing the experimental data with the heat fluxes calculated from simulations. To gain a more thorough understanding of the experimentally determined heat flux profile, the hot gas temperature distribution is also examined. As the comparison proves, this study’s simulation approach predicts, with sufficient precision, wall heat fluxes in a rocket combustor.
       
  • Parameterization and optimization design of a hypersonic inward turning
           inlet
    • Abstract: Publication date: Available online 9 July 2019Source: Acta AstronauticaAuthor(s): Bing Xiong, Xiao-qiang Fan, Yi Wang To improve the performance of a hypersonic inward turning inlet, an optimization design method was proposed. A parameterization methodology was developed for an axisymmetric basic flowfield, and the geometry of a basic flowfield can be easily generated in several parameters. Preliminarily, an optimization targeting on the basic flowfield performance was conducted. As a result, the total pressure recovery of the basic flowfield was improved 7.65% compared with the referred one under the same constraints. The corresponding stream-traced inlet performance was also improved 5.65%. For further optimization, an optimization directly targeting on the 3-D inlet performance was carried out. The method of calculating along streamlines (MCS), which is for the fast calculation of a stream-traced inlet flowfield, was proposed and confirmed before this optimization. The result shows that the 3-D inlet total pressure can be further enhanced 6.74% than the previous one, and it is 12.78% higher than the referred one. That is to say, it is more reasonable to target on the inlet performance directly for an optimization, rather than targeting on the basic flowfield performance. By statistically analyzing the optimization data, it was found that the opinion “A better basic flowfield means a better stream-traced inlet” is statistically correct, but not exactly correct. The steam-traced inlet performance is not exactly determined by a basic flowfield, and it is determined by a combination of all the flow tubes the inlet captures.
       
  • Heat reduction mechanism of hypersonic spiked blunt body with installation
           angle at large angle of attack
    • Abstract: Publication date: Available online 5 July 2019Source: Acta AstronauticaAuthor(s): Jie Huang, Wei-Xing Yao, Ning Qin The spiked blunt body is usually adopted to reduce the aerodynamic heating of hypersonic vehicles. In this paper, the heat reduction mechanism of hypersonic spiked blunt body with installation angle at large angle of attack is studied by the CFD numerical method. The AUSM+ scheme and Menter's SST k-ω turbulent model are adopted for the spatial discretization and turbulent simulation respectively. The results show that the maximum wall heat flux of blunt body is sensitive to the angle of attack. The increase of angle of attack causes the aerodynamic heating to rise sharply. The installation angle of the spike can effectively reduce the maximum heat flux of blunt body at large angle of attack, which is very beneficial to the thermal protection of blunt body. There is an optimal installation angle to minimize the maximum heat flux of blunt body. The optimal installation angle is about 1.5° greater than the angle of attack. All the investigations in this paper show the feasibility and advantages of spiked blunt body with installation angle in the engineering applications.
       
  • Nussbaum-based robust tracking control of flexible air-breathing
           hypersonic vehicles with actuator dynamics
    • Abstract: Publication date: Available online 3 July 2019Source: Acta AstronauticaAuthor(s): Xianlei Cheng, Peng Wang, Zhaojun Mao, Wenbo Huang, Guojian Tang This paper proposes an effective control scheme to address the robust tracking control problem of the flexible air-breathing hypersonic vehicle subject to actuator dynamics. The whole vehicle dynamics is decomposed into the velocity subsystem and altitude subsystem, and the nonlinear disturbance observer based dynamic surface control is employed in the controller design within both subsystems. In order to tackle the input constraints, different hyperbolic tangent functions are carefully designed to approximate the non-smooth saturation functions. The compensators are further introduced for saturation approximations with the Nussbaum function technique. Through Lyapunov stability analysis, the closed-loop system is guaranteed to be semi-globally uniformly ultimately bounded. Moreover, the tracking and estimation errors converge to an arbitrary small neighborhood around zero. Extensive simulation and evaluations verify the superiority of the proposed scheme.
       
  • Radio seti observations of the interstellar object 'oumuamua
    • Abstract: Publication date: Available online 1 July 2019Source: Acta AstronauticaAuthor(s): Gerald R. Harp
       
  • Composite weighted average consensus filtering for space object tracking
    • Abstract: Publication date: Available online 29 June 2019Source: Acta AstronauticaAuthor(s): Hao Chen, Jianan Wang, Chunyan Wang, Jiayuan Shan, Ming Xin In this paper, a composite weighted average consensus filtering (CWACF) algorithm is proposed for space object tracking by combining two distributed heterogeneous nonlinear filters. In light of the sensors’ different sensing accuracy and computational capability, extended Kalman filter (EKF) and sparse-grid quadrature filter (SGQF) are compositely adopted on different sensors as local filters. Then, estimates from neighbours are fused based on the weighted average consensus framework to attain better estimation performance. Moreover, it is proved that the estimation error is exponentially bounded in mean square. The performances of the proposed algorithm, the distributed extended Kalman filtering (DEKF) and the distributed sparse-grid quadrature filter (DSGQF) are compared in a space object tracking problem.
       
  • Least-squares solution of a class of optimal space guidance problems via
           Theory of Connections
    • Abstract: Publication date: Available online 18 June 2019Source: Acta AstronauticaAuthor(s): Roberto Furfaro, Daniele Mortari In this paper, we apply a newly developed method to solve boundary value problems for differential equations to solve optimal space guidance problems in a fast and accurate fashion. The method relies on the least-squares solution of differential equations via orthogonal polynomials expansion and constrained expression as derived via Theory of Connection (ToC). The application of the optimal control theory to derive the first order necessary conditions for optimality, yields a Two-Point Boundary Value Problem (TPBVP) that must be solved to find state and costate. Combining orthogonal polynomials expansion and ToC, we solve the TPBVP for a class of optimal guidance problems including energy-optimal landing on planetary bodies and fixed-time optimal intercept for a target-interceptor scenario. The performance analysis in terms of accuracy shows the potential of the proposed methodology as applied to optimal guidance problems.
       
  • Influence of flow parameters on the dynamic performance for the supersonic
           jet element
    • Abstract: Publication date: Available online 17 June 2019Source: Acta AstronauticaAuthor(s): Y. Xu, G.Q. Zhang The influence of the inlet and outlet flow parameters on the dynamic performance for the supersonic jet element have been investigated numerically in details. And the precision and errors accumulation of the numerical method has also been estimated. The influence of the main jet pressure and the mass flow rate of the control flow on the output thrust as well as the switching time have been deeply studied. The results have shown that increasing the mass flow rate of the control flow can shorten the switching time and increase the effective thrust slightly, but it also can enhance the unsteadiness of flow in the wall-attached work state but decrease the energy utilization rate of the supersonic jet flow component. The effective thrust generated by the cold air is larger than the gas work medium. And the switching time for the gas working medium is also shorter, which is more conducive to the completion of the switch process. The vortical structures at different switching time together with the force variations inside the jet element have been obtained computationally and analyzed in details.
       
  • Calorimetric study on electrolytic decomposition of hydroxylammonium
           nitrate (HAN) ternary mixtures
    • Abstract: Publication date: Available online 5 June 2019Source: Acta AstronauticaAuthor(s): Wai Siong Chai, Jitkai Chin, Kean How Cheah, Kai Seng Koh, Tengku F.Wahida Ku Chik Electrolytic decomposition of hydroxylammonium nitrate (HAN) is appealing for development of chemical micropropulsion system due to its effectiveness in thermal management. In this paper we present the decomposition characteristics and behaviour of various HAN ternary mixtures prepared according to 0 Oxygen Balance (0 OB). There are multiple stages of decomposition depending on the type of fuels added into the HAN solution. While concentrated HAN solution (73 wt%) has only single stage of decomposition, the saccharides-based HAN ternary mixtures has three stages reaction with increased energy release. The addition of nitrogen-rich compounds has sustained the electrolytic decomposition process into the second stage of reaction, which produced the highest decomposition temperature. The study also reveals a linear relationship between the electrical resistivity of HAN ternary mixture and reaction rate in the first stage of reaction, indicating the presence of Joule heating in the process. The influence of electrical resistivity of the ternary mixture became negligible in the second stage of reaction. This work concludes the importance of combined electrical and thermal energy in the first stage decomposition of HAN ternary mixtures.Graphical abstractImage 1
       
  • An optimized analytical solution for geostationary debris removal using
           solar sails
    • Abstract: Publication date: Available online 5 June 2019Source: Acta AstronauticaAuthor(s): Patrick Kelly, Riccardo Bevilacqua Debris in geostationary Earth orbits is often uncontrollable, consisting of launch-vehicle upper stages and non-operational payloads. To help mitigate orbital debris congestion, a solar-sailing satellite concept is proposed which retrieves and relocates large debris for placement into the “graveyard” orbit above the geostationary regime. This work derives an analytical deorbit solution based on Lyapunov control theory combined with the calculus of variations. A dynamic constraint vector is introduced as a result, which dictates the orbital response of a spacecraft to some controlled perturbation. The resulting controller is simulated for various solar sailing platforms to characterize deorbit capability based on a system's area to mass ratio. User design parameters in these solutions are then optimized using a Particle Swarm Optimizer (PSO) to produce robust, locally time optimal solutions for orbital debris removal using solar sails. Solar sail deorbit times are shown to decrease as the reflective area increases, with additional performance dependencies based on the Earth's relative position from the sun.
       
  • Uncertain parameters analysis of powered-descent guidance based on
           Chebyshev interval method
    • Abstract: Publication date: Available online 26 May 2019Source: Acta AstronauticaAuthor(s): Long Cheng, Hao Wen, Dongping Jin This paper focuses on the powered-descent guidance (PDG) problem involving uncertain-but-bounded parameters. An efficient numerical algorithm based on the high approximation accuracy of the Chebyshev series expansion is presented to solve the nonlinear optimal control problem with interval uncertain parameters. First, an infinite number of uncertain optimal control problems is translated into a series of deterministic optimal control problems by exploiting the Chebyshev interval inclusion. Subsequently, the deterministic optimal control problem is solved by a convex optimization method based on the lossless convexification of the PDG problem. Afterwards, these techniques are used to generate the enclosure of the PDG trajectory with uncertainty and the upper and lower bounds of the minimum fuel consumption during the pinpoint landing mission. Finally, the effectiveness and superiority of the proposed approach are validated by illustrative numerical simulations.
       
  • Switching mechanism investigation for the supersonic jet element:
           Deflection, attachment and adjustment stages
    • Abstract: Publication date: Available online 22 May 2019Source: Acta AstronauticaAuthor(s): Y. Xu, G.Q. Zhang Based on the unsteady viscous flow simulation, the flow characteristics inside the supersonic jet Element have been investigated numerically. The results have revealed that once the specific structures of the supersonic jet element are finalized, even if the boundary conditions remain unchanged, the corresponding internal flow will also shows strong unsteady in a certain range of primary gas source pressure. The instability of the main vortex center is a main reason to make the output thrust of the supersonic jet components fluctuate all the time in the attached wall condition. At the deflection of the jet stage, once the static pressure for the right side of the wedge exceeds the left side, the transverse expansion for the stripping zone near the right output channel entrance can play a significant role in making the primary jet deflect successfully. When the jet starts to attach the wall layer, due to the “Coanda” effect, the jet also can attach the layer successfully even though the corresponding control flow is totally closed. When the jet enters the adjustment stage, the thrust changes process for the left and right outputs will experience two typical stages: adjusting and adjusted stages. The corresponding vortex structures at different switching time together with the force variations etc. inside the jet Element have been obtained computationally and analyzed in details.
       
  • A techno-economic analysis of asteroid mining
    • Abstract: Publication date: Available online 10 May 2019Source: Acta AstronauticaAuthor(s): Andreas M. Hein, Robert Matheson, Dan Fries Asteroid mining has been proposed as an approach to complement Earth-based supplies of rare earth metals and supplying resources in space, such as water. However, existing studies on the economic viability of asteroid mining have remained rather simplistic and do not provide much guidance on which technological improvements would be needed for increasing its economic viability. This paper develops a techno-economic analysis of asteroid mining with the objective of providing recommendations for future technology development and performance improvements. Both, in-space resource provision such as water and return of platinum to Earth are considered. Starting from first principles of techno-economic analysis, gradually additional economic and technological factors are added to the analysis model. Applied to mining missions involving spacecraft reuse, learning curve effect, and multiple spacecraft, their economic viability is assessed. A sensitivity analysis with respect to throughput rate, spacecraft mass, and resource price is performed. Furthermore, a sample asteroid volatile mining architecture based on small CubeSat-class spacecraft is presented. It is concluded that key technological drivers for asteroid mining missions are throughput rate, number of spacecraft per mission, and the rate in which successive missions are conducted. Furthermore, for returning platinum to Earth, market reaction strongly influences its economic viability.
       
  • A new principle of separation of gas mixtures in non-stationary
           transitional flows
    • Abstract: Publication date: Available online 10 May 2019Source: Acta AstronauticaAuthor(s): Artem Yakunchikov, Vasily Kosyanchuk The paper studies non-stationary gas flow in a transitional regime in a region with a moving boundary. Interest in this problem is due to the search for new principles of gas separation, which can be implemented in practice as a microelectromechanical system (MEMS). The diminutiveness of such systems makes them relevant for aerospace applications. To solve the problem, the method of event-driven molecular dynamics (EDMD) was used, which was extended by the authors to the case of computational domain with moving boundaries (simulating moving elements of the device). A new principle of operation of the separation device was proposed and investigated. It was obtained that the separation coefficient of proposed device can be significantly higher than that of the diffusion method.
       
  • Protection of inflatable modules of orbital stations against impacts of
           particles of space debris
    • Abstract: Publication date: Available online 27 April 2019Source: Acta AstronauticaAuthor(s): E.P. Buslov, I.S. Komarov, V.V. Selivanov, V.A. Titov, N.A. Tovarnova, V.A. Feldstein Provides the describing the impact micrometeoroid and orbital debris (MMOD) on the Micrometeoroids and Debris Protection System (MDPS) for inflatable modules for lunar orbital application. MDPS flexibility and compactness are achieved by the use as screens packets fabric materials. These materials have effective crushing properties due to absorption of impact energy in the breakdown of tissue layers. The soft materials used to create inflatable modules are proving they can perform just as well as more rigid structures in space, but the impact physics is different. The development of method of describing the impact MMOD linked with this type of shields will lead to an improvement in their design, in terms of mass, efficiency and costs. The results are hypervelocity impact test campaign on the MDPS for inflatable modules for lunar orbital application presented.
       
  • Rapid trajectory design in complex environments enabled by reinforcement
           learning and graph search strategies
    • Abstract: Publication date: Available online 25 April 2019Source: Acta AstronauticaAuthor(s): A. Das-Stuart, K.C. Howell, D. Folta Designing trajectories in dynamically complex environments is challenging and easily becomes intractable. Recasting the problem may reduce the design time and offer global solutions by leveraging phase space mapping patterns available as accessible regions, and the application of search techniques from combinatorics. A computationally efficient search process produces potential trajectory concepts to meet unique design requirements over a broad range of mission types, including low-thrust scenarios. A successful framework is summarized in terms of four components: (i) Accessible regions - establishing reachable regions within the design space for a given thruster/engine capability. (ii) Database exploitation - discretization of well known dynamical structures to form a searchable 2D or 3D volume or map. (iii) Automated pathfinding - exploiting machine learning techniques to determine the transport sequence to deliver an efficient path. (iv) Convergence/optimization - once the transport sequence is determined as a globally efficient concept, it is optimized locally by traditional numerical strategies.
       
  • How much of the solar system should we leave as wilderness'
    • Abstract: Publication date: Available online 16 April 2019Source: Acta AstronauticaAuthor(s): Martin Elvis, Tony Milligan “How much of the Solar System should we reserve as wilderness, off-limits to human development'” We make a general argument that, as a matter of fixed policy, development should be limited to one eighth, with the remainder set aside. We argue that adopting a “one-eighth principle” is far less restrictive, overall, than it might seem. One eighth of the iron in the asteroid belt is more than a million times greater than all of the Earth's currently estimated iron ore reserves, and it may well suffice for centuries. A limit of some sort is necessary because of the problems associated with exponential growth. We note that humans are poor at estimating the pace of such growth and, as a result, the limitations of a resource are hard to recognize before the final three doubling times. These three doublings take utilization successively from an eighth to a quarter, then to a half, and then to the point of exhaustion. Population growth and climate change are instances of unchecked exponential growth. Each places strains upon our available resources, each is a recognized problem that we would like to control, but attempts to do so at this comparatively late stage in their development have not been encouraging.Our limited ability to see ahead until such processes are far advanced, suggests that we should set ourselves a “tripwire” that gives us at least 3 doubling times as leeway. This tripwire would be triggered when one eighth of the Solar System's resources are close to being exploited. The timescale on which we might hit this tripwire, for several assumed growth rates, is long. At a 3.5% growth rate for the space economy, comparable to that of the use of iron from the beginning of the Industrial Revolution until now, the 1/8th point would be reached after 400 years. At that point, the 20-year doubling time associated with a 3.5% growth rate would mean that only 60 years would remain in which to transition the economic system to new “steady state” conditions. The rationale for adopting the one-eighth principle so far in advance is that it may be far easier to implement in-principle restrictions at an early stage, rather than later, when vested and competing interests have come into existence under conditions of diminishing opportunity.
       
  • Design of fault-tolerant microprocessors for space applications
    • Abstract: Publication date: Available online 16 April 2019Source: Acta AstronauticaAuthor(s): M.S. Gorbunov We discuss the main design concepts for fault-tolerant microprocessors, Instruction Set Architectures (ISA) of microprocessors for space applications and the achievable characteristics considering the KOMDIV microprocessors designed by SRISA. The trade-off between the fault-tolerance, performance and power consumption is considered for microprocessors designed using the silicon-on-insulator (SOI) and bulk CMOS technologies.
       
  • Dynamics of the gas-dust cloud observed in the upper atmosphere on October
           26, 2017
    • Abstract: Publication date: Available online 4 April 2019Source: Acta AstronauticaAuthor(s): Sergey Nikolayshvili, Stanislav Kozlov, Yulii Platov, Andrey Repin The results of the study of the gas-dust cloud of solid fuel combustion products dynamics formed under a rocket stages separation are presented. The sequence of the digital images obtained in the twilight condition at a distance of ∼1500 km from the missile trajectory was analyzed. The height of the cloud center reaches up to ∼900 km, and its diameter is ∼2000 km. The glow of the cloud is determined by the scattering of sunlight on dispersed particles of the combustion products. The obtained data allow to specify the dispersed composition of the cloud and dynamic parameters of its development. The proposed methodology can be used to clarify the physical picture of the interaction of the combustion products of solid propellant with the environment, as well as environmental conditions and processes in the upper atmosphere.
       
  • Fault detection and diagnosis algorithms for transient state of an
           open-cycle liquid rocket engine using nonlinear Kalman filter methods
    • Abstract: Publication date: Available online 29 March 2019Source: Acta AstronauticaAuthor(s): Jihyoung Cha, Sangho Ko, Soon-Young Park, Eunhwan Jeong This paper deals with an application of the fault detection and diagnosis algorithm based on nonlinear Kalman filter methods for transient state of an open-cycle liquid propellant rocket engine. In order to develop the algorithm, we designed two types of the nonlinear Kalman filter which are the extended Kalman filter and unscented Kalman filter with non-linear model of the liquid propellant rocket engine. Then using the measurement data of some important parameters of the engine, the residuals from the nonlinear Kalman filters are obtained. Using the residuals, we can detect and diagnose faults in the components of the engine by using the multiple model method. To confirm the fault detection and diagnosis algorithm, we developed mathematical model of an open-cycle liquid propellant rocket engine and artificially injected various faults such as decreasing turbopump efficiency. And then, perform the fault detection and diagnosis algorithm and check the performance of the algorithm. This process is numerically demonstrated for the open-cycle liquid propellant rocket engine under start-up process by using the simulated measurement data from the mathematical model of the engine.
       
  • A new gyroscopic principle. New gyroscopic effects on cold atoms and on de
           Broglie waves, different from the Sagnac effect
    • Abstract: Publication date: Available online 28 March 2019Source: Acta AstronauticaAuthor(s): Nikolay I. Krobka This article provides a brief overview of the state-of-the-art development of a new generation of gyros on cold atoms for space applications. The problem of narrowing the dynamic range of atomic interferometers in comparison with optical interferometers and method for resolving this problem are discussed. Three new results are presented for the first time in the world: 1) A new “kinematic” gyroscopic principle that allows one to determine uniquely the absolute angular velocity without limitations on the measurement range, in contrast to the interferometric gyroscopic principle; 2) Accurate expressions of gyroscopic effects on cold atoms and on de Broglie waves based on kinematic and interferometric gyroscopic principles, which are fundamentally different from the Sagnac effect; 3) The asymmetry of the particle-wave duality seen in gyroscopy: an increase in the sensitivity to rotation when stepping from photons to cold atoms is colossally greater than the increase in sensitivity when stepping from light waves to de Broglie waves of the order of (1013 ÷ 107) at atom temperature of the order of (10−9 ÷ 10−3) K.
       
  • High-order state transition polynomial with time expansion based on
           differential algebra
    • Abstract: Publication date: Available online 28 March 2019Source: Acta AstronauticaAuthor(s): Zhen-Jiang Sun, Pierluigi Di Lizia, Franco Bernelli-Zazzera, Ya-Zhong Luo, Kun-Peng Lin In this study, a high-order state transition polynomial with time expansion (STP-T) method is developed to propagate an initial orbital state around its reference value to a variable final time based on the differential algebra (DA) technique. STP-T is a high-order Taylor polynomial of the final orbital state expanded around the reference initial state and reference propagation time. Since the final state usually shows different nonlinearity with respect to different components of initial state and propagation time, a weighted-order scheme is combined with STP-T, which enables the STP-T to have higher orders on the components with higher nonlinearity and lower orders on the components with lower nonlinearity. Then, an error estimation method is presented, which can a priori provide the error profiles of a STP-T and is useful for selecting a proper order and determining the corresponding valid ranges of displacements. Finally, the STP-T method is tested for orbit propagation under three typical orbital dynamics: the unperturbed Keplerian dynamics, the J2 perturbed two-body dynamics, and the nonlinear relative dynamics. The numerical simulation results indicate that the STP-T supplies a good approximation of the final state within certain valid ranges of initial state and propagation time, the a priori estimated error is close to the exact error in sense of trend and magnitude, and the computational cost can be significantly saved by the weighted-order scheme without loss of accuracy.
       
  • Interaction between hypervelocity elongated projectile and screen
           protection of space vehicles
    • Abstract: Publication date: Available online 27 March 2019Source: Acta AstronauticaAuthor(s): B.V. Rumyantsev, I.V. Guk, A.I. Kozachuk, A.I. Mikhaylin, S.I. Pavlov, M.V. Silnikov In the article, we study the efficiency of screen protection of space vehicles against hypervelocity elongated projectiles that are an analog of the most dangerous space debris. We analyze the kinetics of an elongated projectile penetration into a target after the projectile passes through screen protection. Parameters of an elongated projectile impact with copper and aluminum screens and a state of a cavern surface formed as a result of projectile penetration into metal target have been found. Rapid unloading of the penetration zone, the emergence of pores in the volume of the projectile material before their destruction in a jet flow region can explain the increase of efficiency of screen protection when evaporating space junk.
       
  • Water quality monitoring during interplanetary space flights
    • Abstract: Publication date: Available online 26 March 2019Source: Acta AstronauticaAuthor(s): G.Yu. Grigoriev, A.S. Lagutin, Sh.Sh. Nabiev, B.K. Zuev, V.A. Filonenko, A.V. Legin, D.O. Kirsanov Advanced approaches to the development of analytical modules for water quality on-line monitoring during long-time orbital piloted missions are discussed. The first module is intended for an analysis of water ionic composition and its microbiological toxicity with individual selective sensors. The second module operating with the use of an oxythermographic method ensures recirculating water monitoring for the content of total carbon and specific hydrocarbons, e.g., ethanol. Both modules represent subsystems of an integrated analytical complex for an on-line control of air and water quality onboard spacecrafts.
       
  • Non-stationary process of accelerating the measuring probe in the
           laboratory ballistic module
    • Abstract: Publication date: Available online 21 March 2019Source: Acta AstronauticaAuthor(s): M. Yu Sotskiy, V.A. Veldanov, V.V. Selivanov A variant of the technology of dynamic contact sensing of rheological media, including a wired connection for connecting the measuring probe with the recorder, is presented. The results of a series of laboratory experiments with high-speed imaging of the process from the beginning of the movement of the measuring probe and the wire of electrical communication in the starting device to the end of the movement of the probe in the target medium are shown. The process of the impact of the detonation products of the working gas on the probe and on the elements of the measuring assembly is analyzed. Based on the analysis of the evolution of the shape of the electric wire, conditions were determined that ensure the reliability of recording the motion parameters of the measuring probe on the flight path and in the target.
       
  • HMGB1 mediated autophagy protects glioblastoma cells from carbon-ion beam
           irradiation injury
    • Abstract: Publication date: Available online 19 March 2019Source: Acta AstronauticaAuthor(s): Runhong Lei, Liben Yan, Yulin Deng, Jin Xu, Tuo Zhao, M. Umer Farooq Awan, Qiang Li, Guangming Zhou, Xiao Wang, Hong Ma The present study investigated autophagy changes and the expression of HMGB1 in human glioblastoma cells, responding to carbon-ion beam irradiation (35 keV/μm, 80.55 MeV/u). U251 cells were irradiated with carbon-ion beams and cell proliferation was measured by counting the number of living cells. The expression of Light Chain 3 beta (LC3B), Beclin 1, high-mobility-group box 1 (HMGB1), pro-form caspase-3 and Cellular FLICE-like inhibitory protein (c-FLIP) was analyzed by western blotting. Caspase enzyme activity was determined via a caspase cleavage based florescent substrate commercial Kit. Living cell counting demonstrated a time- and dose-dependent cell death in U251 cells. The expression of LC3B and Beclin 1 revealed that, a high level of autophagy was induced 24 h after irradiation with 1 Gy carbon ions and then decreased in a time- and dose-dependent manner. The expression of the whole HMGB1 showed a well correlation with the dynamic autophagic level. Cytoplasmic HMGB1 maintained autophagy was concluded. Enzyme-Linked Immuno Sorbent Assay (ELISA) measurement found that, HMGB1 was released into the extracellular space in a time- and dose-dependent manner. Lower intracellular HMGB1 levels correlated with decreased autophagy as measured by the expression of LC3B. Decreased expression of pro-form caspase-3 and c-FLIP as well as the increased caspase enzyme activity indicated that apoptosis was induced by carbon-ion beam irradiation. Inhibition of HMGB1 release from the area of intracellular to that of extracellular significantly increased cell survival. In summary, carbon-ion beam irradiation could elevate autophagy and HMGB1 expression efficiently, which would protect the cells from programmed cell death via inducing autophagy. Apoptosis as measured by expression of caspase activities increased as the dose increased, which was accompanied with decreased levels of LC3B and HMGB1.
       
  • Atmosphere composition control during long-duration space missions
    • Abstract: Publication date: Available online 16 March 2019Source: Acta AstronauticaAuthor(s): G.Yu. Grigoriev, A.S. Lagutin, Sh.Sh. Nabiev, A.A. Vasiliev, O.I. Orlov, L.N. Mukhamedieva, A.A. Pakhomova, A.V. Rodin, V.M. Semenov, D.B. Stavrovskii, M.G. Golubkov A concept and strategy of the monitoring of chemical composition of the atmosphere in manned spacecrafts applicable during long-term and interplanetary flights are considered. The suggested concept and strategy are applicable for the life support system in spacecraft, which includes a system of gas composition support, a water supply system, a system of sanitary and hygienic support, a food supply system and a thermal control system. Major risk factors related with changes of the atmosphere composition during interplanetary space missions are evaluated.An advanced design of the analytical complex is described for the control of air quality in manned spacecraft's taking into account these risk factors. The simultaneous use of several methods of gas analysis is proposed together with partial overlapping of the set of substances to be detected with regard to the substances of particular (critical) importance. Application of such gas control system will provide a tool for the analyzing of a wide range of substances and will ensure the analysis of the atmosphere even in case of the failure of some of its parts.
       
  • High-frequency electromagnetic radiation affecting moving conductive
           screens
    • Abstract: Publication date: Available online 14 March 2019Source: Acta AstronauticaAuthor(s): M.N. Smirnova, V.V. Tyurenkova, S.N. Kosinov, V.F. Nikitin Protection of on board electronic devises subjected to high-frequency electromagnetic emission is a crucial problem of Space flight safety. The present paper contains the results of theoretical investigation of the effects of high frequency electromagnetic radiation on a moving conductive screen. Methods are developed and results are presented aimed at evaluating conductive screen protective properties depending on thermophysical and electromagnetic properties of material, radiation intensity and frequency, as well as relative velocity of the radiation source and the target.
       
  • Geostationary station-keeping with electric propulsion in full and failure
           modes
    • Abstract: Publication date: Available online 14 March 2019Source: Acta AstronauticaAuthor(s): Lincheng Li, Jingrui Zhang, Yanyan Li, Shuge Zhao This paper focuses on geostationary satellites with an electric propulsion system and develops two efficient station-keeping strategies in full and failure modes. High-precision mean orbital elements are calculated by an estimator and used as the inputs of two control strategies. In the full mode, an optimization-based maneuver planner, which requires the computations of future orbits, is proposed to achieve long-term minimum-fuel station-keeping. In the failure mode, a fault detection algorithm is designed to diagnose the thruster failure and compute the orbital deviation caused by faulted thruster. Subsequently, a real-time control law as well as a threshold function is formulated to produce the on-off commands of electric thrusters, which correct the orbital deviation. Finally, numerical simulations are made to validate the accuracy and efficiency of two strategies.
       
  • Study on the damping capacity of a fluidic baffle under different
           injection conditions
    • Abstract: Publication date: Available online 13 March 2019Source: Acta AstronauticaAuthor(s): Wooseok Song, Jongkwon Lee, Jaye Koo Passive control methods have been widely used to decrease the intensity of combustion instability, and a structural baffle injector has been applied in liquid rocket-engine development. However, the development cost of a structural baffle injector increases because the thrust of a liquid rocket engine should increase as the weight increases. The objective of this paper is to analyze the damping capacity of a fluidic baffle injector using a dissimilar injector arrangement. In this study, a cold-flow test was conducted to observe the effect of using a fluidic baffle injector, and a pulse gun was adopted to generate the pressure wave. A gas-centered swirl coaxial injector and a shear coaxial injector were used to inject the bipropellant. Gaseous nitrogen and liquid water were used for the bipropellant. In addition, multi injectors and a pulse gun were used to compare the effects of a gas-centered swirl coaxial injector and a shear coaxial injector, each acting as the fluidic baffle, on the spray intensity under different conditions. When the gas-centered swirl coaxial injector was used as the fluidic baffle injector, the amplitude increase rate increased as the momentum flux ratio decreased. However, the shear coaxial injector obstructed the pressure-wave propagation. Therefore, the shear coaxial injector was a better fluidic baffle injector than the gas-centered swirl coaxial injector.
       
  • Dual-arm coordinated capturing of an unknown tumbling target based on
           efficient parameters estimation
    • Abstract: Publication date: Available online 12 March 2019Source: Acta AstronauticaAuthor(s): Jianqing Peng, Wenfu Xu, ErZhen Pan, Lei Yan, Bin Liang, Ai-guo Wu A malfunctioned satellite or other space debris is generally non-cooperative and tumbling, bringing great challenge to capture and remove it. In this paper, we propose a dual-arm coordinated capturing method based on efficient parameters estimation. Firstly, the dynamics model of a tumbling target is deduced in details. Its motion characteristics are then analyzed. Secondly, we design an efficient Hybrid Kalman Filter (HKF) by combining Extended Kalman Filter (EKF) with Unscented Kalman Filter (UKF). It effectively overcomes the shortcoming of low accuracy of EKF and long iteration time of UKF, and improves the speed and accuracy of the Kalman Filter iteration algorithm. Two movement cases of an uncontrolled target are considered: one is rotation around the principal axes of inertia; the other is rotation around arbitrary axes. Thirdly, the estimated motion and inertia parameters are used to plan the trajectories of a dual-arm space robot to capture the tumbling target. Finally, the simulation environment is created and the proposed method is verified. The simulation results show that the proposed HKF algorithm can estimate the attitude quaternion, angular velocity, and the inertia tensor (including Ixx, Iyy, Izz, Ixy, Ixz and Iyz) with higher accuracy (compared to EKF) and lower computation cost (compared to UKF); the planned trajectories of the dual-arm space robot are effectively for tumbling target capturing.Graphical abstractImage 1
       
  • Visibility optimization of satellite constellations using a hybrid method
    • Abstract: Publication date: Available online 12 March 2019Source: Acta AstronauticaAuthor(s): Chao Han, Shengzhou Bai, Sihang Zhang, Xinwei Wang, Xiaohui Wang For the visibility optimization problem of satellite constellations, this paper presents an efficient hybrid optimization method taking multiple constraints into account. To reduce the time needed for the optimization, the satellite constellation is assumed to have a specific configuration. The optimization includes two steps. The first step searches for optima over a large scale, while the second step is designed to obtain the accurate optimal solution based on the result of the first-step optimization. Based on the analysis of the coverage performance function, a linear adaptive population method is proposed for the first step. When compared with the traditional optimization method, calculation time can be efficiently reduced while ensuring an accurate optimization. Several numerical simulations are conducted for validation. It proves to be a practical choice for engineering applications.
       
  • Experimental study and numerical simulation of chemiluminescence emission
           during the self-ignition of hydrocarbon fuels
    • Abstract: Publication date: Available online 6 March 2019Source: Acta AstronauticaAuthor(s): A.M. Tereza, S.P. Medvedev, V.N. Smirnov The time evolution of the chemiluminescence emission signals of CH*, OH*, C2*, and CO2* during the self-ignition of a number of the simple hydrocarbons is studied. The experiments are performed behind reflected shock waves over a temperature range of 1100–1900 K at a pressure of ∼1 bar. The effects of fuel-to-oxidizer equivalence ratio and the structure of the hydrocarbon molecule on the time profiles of the signals for each of the emitters are examined. A detailed kinetic mechanism for describing the emission signals from CH*, OH*, C2*, and CO2* recorded during the self-ignition of hydrocarbons is developed. To make the simulations more rigorous and reliable, the NASA thermodynamic polynomials for C2*, and CO2* were calculated based on the respective rotational and vibrational parameters given in the literature. Numerical simulations satisfactorily reproduce the measured time profiles of the signals from the studied emitters.
       
  • Statistical behavior of shear layers of reactive oxygen/kerosene spray
    • Abstract: Publication date: Available online 6 March 2019Source: Acta AstronauticaAuthor(s): Songyi Choi, Junsun Ahn, Jaye Koo Reactive gaseous oxygen/kerosene spray was visualized by a shadowgraph imaging technique in a lab-scale rocket engine combustor. Dynamic behaviors of inner and outer shear layer were observed morphologically and analyzed quantitatively by image processing. Correlation methods were used to statistically analyze dynamic behaviors of each shear layer and interaction between two shear layers. Relationship between shear layer dynamics and combustion flow-field was investigated by analyzing periodicity of jet-core length, lump-detachment, and luminous flame intensity. The results of correlation and frequency analysis show that dominant frequency of behaviors and interaction of shear layers is 270 Hz and the degree of correlation becomes stronger along the flow direction. The dominant frequency of core length variation and luminous flame formation is around 270 Hz and, which is the same as that of behaviors and interaction of shear layers. This proposes that the surface behaviors and interaction of the inner and outer jets in the upstream affect the downstream combustion flow-field.
       
  • Numerical investigation of embedding some hot obstacles in a low speed
           reacting flow of the moderate or intense low-oxygen dilution in a
           jet-in-hot-coflow
    • Abstract: Publication date: September 2019Source: Acta Astronautica, Volume 162Author(s): Mohammad Mansourian, Reza Kamali, In-Seuck Jeung Given the daily growth of pollutant emissions in this age of technology, every method that can increase the efficiency of the combustion as well as reduce the pollution is very important to consider. One way to reach this goal is moderate or intense low oxygen dilution. In the present work, this technology of turbulent nonpremixed CH4-H2 jet flames has investigated in various working conditions in Dally burner, numerically. In this regard, the finite volume method in OpenFOAM package has used with k-ε Re-Normalization Group as well as the discrete ordinates radiation model. Furthermore, the eddy dissipation concept for interaction between turbulence and chemistry in combination with the detailed reaction mechanism have been employed. At first, the results are compared with the experimental data and after validating the obtained results of the solution, the moderate or intense low-oxygen dilution combustion is investigated by putting some hot obstacles in the burner. The results show that the hot obstacle has a role similar to the hot spot and helps this condition of combustion to reduce the initial cost in order to preheat the hot oxidizer co-flow. This means that putting the hot obstacle in the burner causes to reduce the preheat temperature and the energy consumption per second up to 300 K and 17.9%, respectively, while it increases the turbulence intensity, reaction zone, outlet CO2 and H2O species while reduces NOx and CO emissions.
       
  • Novel augmented proportional navigation guidance law for mid-range
           autonomous rendezvous
    • Abstract: Publication date: September 2019Source: Acta Astronautica, Volume 162Author(s): Yuanhe Liu, Kebo Li, Lei Chen, Yangang Liang In this paper, a novel augmented proportional navigation (APN) guidance law is proposed for the mid-range autonomous rendezvous. The line-of-sight (LOS) rotation coordinate system is used, which can decouple the three-dimensional relative motion between the chaser and target into the relative motion in the engagement plane and the rotation of this plane. The APN guidance law is consisted of two parts. The first one is a novel nonsingular terminal sliding mode control (NTSMC) along LOS to drive the relative distance and approaching speed to the desired values in finite time. The second one is the modified true proportional navigation (TPN) guidance law perpendicular to LOS to control the LOS rate in a certain range. It has been proven that, even when there are disturbances and uncertainties along and perpendicular to LOS, the proposed APN can guarantee the finite time convergence of the relative distance and approaching speed and limit the LOS rate within a certain acceptable range. Hence, the mid-range autonomous rendezvous can be perfectly realized. The new theoretical findings are demonstrated by numerical simulation results.
       
  • Calibration and preliminary tests of the Brine Observation Transition To
           Liquid Experiment on HABIT/ExoMars 2020 for demonstration of liquid water
           stability on Mars
    • Abstract: Publication date: September 2019Source: Acta Astronautica, Volume 162Author(s): Miracle Israel Nazarious, Abhilash Vakkada Ramachandran, Maria-Paz Zorzano, Javier Martin-Torres The search for unequivocal proofs of liquid water on present day Mars is a prominent domain of research with implications on habitability and future Mars exploration. The HABIT (Habitability: Brines, Irradiation, and Temperature) instrument that will be on-board the ExoMars 2020 Surface Platform (ESA-IKI Roscosmos) will investigate the habitability of present day Mars, monitoring temperature, winds, dust conductivity, ultraviolet radiation and liquid water formation. One of the components of HABIT is the experiment BOTTLE (Brine Observation Transition To Liquid Experiment). The purposes of BOTTLE are to: (1) quantify the formation of transient liquid brines; (2) observe their stability over time under non-equilibrium conditions; and (3) serve as an In-Situ Resource Utilization (ISRU) technology demonstrator for water moisture capture. In this manuscript, we describe the calibration procedure of BOTTLE with standard concentrations of brines, the calibration function and the coefficients needed to interpret the observations on Mars.BOTTLE consists of six containers: four of them are filled with different deliquescent salts that have been found on Mars (calcium-perchlorate, magnesium-perchlorate, calcium-chloride, and sodium-perchlorate); and two containers that are open to the air, to collect atmospheric dust. The salts are exposed to the Martian environment through a high efficiency particulate air (HEPA) filter (to comply with planetary protection protocols). The deliquescence process will be monitored by observing the changes in electrical conductivity (EC) in each container: dehydrated salts show low EC, hydrated salts show medium EC and, liquid brines show high EC values. We report and interpret the preliminary test results using the BOTTLE engineering model in representative conditions; and we discuss how this concept can be adapted to other exploration missions.Our laboratory observations show that 1.2 g of anhydrous calcium-chloride captures about 3.7 g of liquid water as brine passing through various possible hydrate forms. This ISRU technology could potentially be the first attempt to understand the formation of transient liquid water on Mars and to develop self-sustaining in-situ water harvesting on Mars for future human and robotic missions.
       
  • Role of aerodome in pulsation/oscillation control and aeroheating
           reduction
    • Abstract: Publication date: September 2019Source: Acta Astronautica, Volume 162Author(s): Qihao Qin, Jinglei Xu There exist two distinct modes of flow instability, namely pulsation and oscillation, related to the flat-ended cylinder with pointed spike in high-speed flights. A new method is proposed in this article to weaken the pressure fluctuations and aeroheating acting on the cylinder, through mounting an aerodome on the spike tip, which creates a cavity-like flow in front of the afterbody. Turbulent, axisymmetric flow at a freestream Mach number of Ma∞ = 6.0 and a Reynolds number (based on the cylinder diameter D) of ReD = 0.13 × 106 is simulated using a temporally and spatially second-order-accurate finite volume method. Numerical results are verified by comparison with the experimental data available in the open literature. It is shown that flow pulsation under the spike length of L/D = 1.0 can be totally controlled as the aerodome diameter increases to DA/D = 23.0%, whereas flow oscillation under the spike length of L/D = 2.0 is suppressed as the aerodome diameter reaches DA/D = 10.0%. Besides, the combination of the double-aerodome and sonic jet is proved the most effective way to provide thermal protection for the afterbody, which smooths down the heat flux peak in the vicinity of the reattachment.
       
  • 8th Paolo Santini memorial lecture on safety of spaceflight structures -
           The application of fracture and damage control
    • Abstract: Publication date: September 2019Source: Acta Astronautica, Volume 162Author(s): Gerben Sinnema Since Apollo it has been necessary to ensure the safety of spaceflight structures by fracture control and damage tolerance methods. Fracture and damage control cover a wide range of structural and materials engineering disciplines. This paper presents a brief overview of the history, the current state of art, and new developments in implementing fracture and damage control to assure spaceflight structural integrity.
       
  • Managing the microvibration impact on satellite performances
    • Abstract: Publication date: September 2019Source: Acta Astronautica, Volume 162Author(s): Frank Steier, Torben Runte, Anneke Monsky, Timo Klock, Gregory Laduree Due to the increasing needs on the performance of satellites, in particular optical satellites, microvibrations have become more and more important over the last years.Microvibrations affect a large number of satellites for both Earth observation and space observation missions. Further, microvibrations are also a concern for other missions with sensitive instruments like Fourier spectrometers, high-precision accelerometers or reference oscillators.In classical fields like structural dynamic engineering, management approaches have been established and implemented in all space projects. This paper presents a corresponding approach for the area of microvibrations. Focus is on the definition of all key elements needed to establish a microvibration control approach. This includes the establishment of microvibration budgets and associated summation rules. A systematic way for microvibration disturbance minimization is presented and rules for the application are defined. Specific emphasis is given to the definition of microvibration interface requirements and the associated control process.The concepts provided in this paper have been verified by tests performed in the frame of various satellite programs and studies. Tests related to the superposition of different noise sources are presented in here.
       
  • Propagation of strong cylindrical shock wave in a self-gravitating
           rotational axisymmetric mixture of small solid particles and perfect gas
           with density varying exponentially
    • Abstract: Publication date: September 2019Source: Acta Astronautica, Volume 162Author(s): G. Nath The non-similarity solution for the propagation of a strong cylindrical shock wave in a self-gravitating and rotational axisymmetric dusty gas, having variable azimuthal and axial fluid velocities is obtained. The dusty gas is assumed to be a mixture of small solid particles of micro size and perfect gas. The equilibrium flow conditions are assumed to be maintained. The density of the mixture and the fluid velocities in the ambient medium are assumed to be varying and obeying an exponential law. The shock wave moves with variable velocity and the total energy of the wave is non-constant. The effects of variation of the mass concentration of solid particles in the mixture, the ratio of the density of solid particles to the initial density of the gas, and the gravitational parameter on the flow variables in the region behind the shock are investigated at a given time in both the rotating and non-rotating cases. Our analysis reveals that an increase in gravitational parameter or in the ratio of the density of solid particles to the initial density of the gas surprisingly the shock strength increases and remarkable differences are found in the distribution of flow variables in both the rotating and non-rotating cases. An increase in time also, increases the shock strength in the case of isothermal flow, but to decrease the shock strength in the case of adiabatic flow in general. Further, it is investigated that the consideration of isothermal flow increases the shock strength. A comparison is made between the solutions in isothermal and adiabatic flow cases with or without gravitational effects in both the rotating and non-rotating medium. The obtained solutions are applicable for arbitrary values of time.
       
  • Lifesaving rockets in Sweden. A century of operation
    • Abstract: Publication date: September 2019Source: Acta Astronautica, Volume 162Author(s): A. Ingemar Skoog The industrialization in the early 19th century gave rise to a major growth in sea-way transportations in European waters. A direct result of this was a rapid increase in sea disasters, in particular in coastal areas. The United Kingdom was the first nation to implement rescue services around its coasts, and several optional systems, in addition to traditional rescue boats, like rockets, mortars and cannons were tested. By the mid 1840's the “rocket apparatus” was implemented as a standard at many British rescue stations. The first rocket type used was the Dennett-rocket, which was of a design similar to the Congreve rockets. Rocket systems were later also designed in several other European countries with need of effective sea rescue systems.1855 the first rescue station in Sweden was taken into service equipped with a rescue boat and a rocket apparatus of Dennett fabrication. During the following century some 40 rescue stations around the Swedish coast were equipped with rocket apparatus. Over the years to come a number of different new rocket systems were tested and some implemented. Some of the Swedish rescue stations have been preserved and are today museums and it turns out that in total some 40 rockets of different types and ages have been preserved at these museum stations. The official records of all activities conducted over a century have also been saved.The today existing rockets have undergone a detailed technical investigation as for the design, performance and operation. Steps of improvements and potential influence of the general advancements of the solid rocket technology over more than a century, from the Congreve type rockets to the rockets in service at the mid of last century, have been analysed. Basically any improvements were made in small steps to advance the handling of a simple but reliable system and less to implement latest advancements in rocket technology. Like the latest rockets preserved, manufactured in 1950 and 1952, the major bulk of rockets used until the mid 20's century were of a Congreve-similar design with the stick guidance concept. The simplicity and conservative evolution to improve the range is also reflected in the use of a “compound”-type of staging for two- and three-stage rockets.
       
  • Shoulder consultations and surgery incidence rates in NASA astronauts and
           a cohort population of working individuals
    • Abstract: Publication date: Available online 10 July 2019Source: Acta AstronauticaAuthor(s): Mitzi S. Laughlin, Jocelyn D. Murray, Mary Wear, William J. Tarver, T. Bradley Edwards, Hussein A. Elkousy, Mary Van Baalen Individuals frequently seek medical care for musculoskeletal disorders of the shoulder and astronauts are no different. The purpose of this study was: 1) to determine the impact of age and sex as risk factors for orthopedic shoulder consultations and surgery in a cohort population; and 2) to determine if NASA astronauts are at a higher risk for consultations and surgery than a cohort population. The cohort (n = 347,540) was a group of working individuals that participated in a capitated insurance plan managed by their employers over a 10-year period. The astronaut cohort was comprised of NASA astronauts selected from 1959 through December 31, 2014 (n = 338). Both populations were limited to individuals between 25 and 64 years. Incidence rates indicate that age and sex were risk factors for consultation and surgery. As age increased, consultations increased significantly for both sexes in a stair-step manner. Males consistently had a higher rate than females in all age categories (all p ≤ 0.001) except for 55-64 year-olds (p = 0.228). Survival analysis confirmed that age (p 
       
  • Zinc oxide aluminum doped slabs for heat-eliminating coatings of
           spacecrafts
    • Abstract: Publication date: Available online 10 July 2019Source: Acta AstronauticaAuthor(s): E.V. Shirshneva-Vaschenko, P.S. Shirshnev, Zh.G. Snezhnaia, L.A. Sokura, V.E. Bougrov, A.E. Romanov This paper discuss a possibility for using a thin-film functional coating based on transparent conducting thin films of aluminum doped zinc oxide (AZO) as a heat-eliminating material on the surface of a spacecraft. The structure of the functional coating has been chosen taking into account the plasmonic properties of AZO and silver and represents the AZO slabs with embedded silver nanoparticles deposited on AZO layer and AZO slabs with embedded silver nanoparticles deposited on thin film fused quartz layer. The paper contains COMSOL finite element simulations of the scattering cross section for thermal radiation in the IR band in the case the investigated coating deposited on a reflective aluminum film, and absorption cross section in the near UV and visible spectral bands when the coating deposited on silicon solar panels. The calculations demonstrate an increase in the scattering cross-section in the spectral band of blackbody radiation by several orders of magnitude, with the maximum in the scattering spectrum of the AZO slabs/ AZO /Al structure corresponding to the maximum intensity of the blackbody thermal radiation, which has been heated to 100 °C in the case the lattice period of the AZO slabs is equal to the resonance wavelength for AZO. Also an increase in the absorption cross-section of AZO slabs/ AZO /Si structure in visible spectral band is observed corresponding to plasmon absorption of embedded silver nanoparticles.
       
  • Modeling and control of a nonlinear coupled spacecraft-fuel system
    • Abstract: Publication date: September 2019Source: Acta Astronautica, Volume 162Author(s): M. Navabi, A. Davoodi, M. Reyhanoglu This paper considers the nonlinear interaction of the rigid body dynamics of a spacecraft with the sloshing dynamics of the liquid propellant in its partially filled spherical tank during an orbital transfer. Fuel slosh dynamics are described by a three-dimensional two-pendulum model characterizing the first two sloshing modes, and the coupled equations of motion of the vehicle and the fuel masses are derived by means of quasi-Lagrangian equations. In addition, this paper studies active nonlinear control methods to control the attitude of the spacecraft while suppressing the sloshing of fuel. Simulations are conducted to illustrate the effectiveness of these control methods.
       
  • Experimental research on the spray characteristics of pintle injector
    • Abstract: Publication date: September 2019Source: Acta Astronautica, Volume 162Author(s): Huiyuan Chen, Qinglian Li, Peng Cheng The spray characteristics of an oxidizer-centered liquid-liquid pintle injector at different momentum ratios are experimentally investigated. Water is used as the simulation fluid of both the fuel and the oxidizer and injected into the axial annular gap and radial orifices, respectively. The radial-to-axial local momentum ratio (LMR) is varied from 0.16 to 0.93 by adjusting the mass flow rate of the oxidizer under constant mass flow rate of the fuel. A high-speed camera and Phase Doppler Anemometry (PDA) system are used to investigate the spray pattern, spray angle, droplet size and velocity distribution. The results indicate that the spray generated by the pintle injector is shaped as a hollow-to-solid cone with a rough boundary. A hollow structure appears in the spray center in the near field and disappears in the far field. With the increase of the momentum ratio, the outer boundary of the spray field is enlarged and the range of the hollow field also increases. The spray angle varies from 34° to 122° for the LMR in the range of 0.16–0.93. Furthermore, the spray angle is deduced as a monotonically increasing function of the local momentum ratio of the pintle injector with discrete radial orifices. The diameter-velocity distribution indicates that SMD (Sauter Mean Diameter) increases slightly and the axial velocity decreases mildly with the increase in the momentum ratio. The SMD curve exhibits an “N” shape in the radial direction, whereas the axial velocity and radial velocity curves exhibit inverted “V” shapes in general. The spray distribution and spray development are mainly controlled by the interaction of the radial flow of the jet and the axial flow of the film, and also to some degree by the impingement of the liquid droplets in the spray center. From the spray center to the edge, the spray of the pintle injector is divided into three regions: the spray core, the mainstream, and the outer boundary.
       
  • Optimal thrust control with magnitude and direction constraints
    • Abstract: Publication date: September 2019Source: Acta Astronautica, Volume 162Author(s): Hong-Xin Shen, Zhi-Sheng Duan, Lorenzo Casalino An indirect optimization procedure is presented to minimize the propellant consumption for finite-burn transfers with two practical thrust control models, namely, inertially fixed thrust and fixed-plane linearly varying thrust direction. The optimality equations are derived with theory of optimal control and the consequent boundary value problem is solved with a procedure based on Newton's method. A homotopic approach is used to find suitable tentative solutions and assure convergence. The method is applied to the optimization of Moon escape trajectories with accurate dynamic models and proves to be fast and accurate.
       
  • A cost effective methodology for building flight spares for robotic life
           extension on the International Space Station
    • Abstract: Publication date: September 2019Source: Acta Astronautica, Volume 162Author(s): Vivian Truong, Tom Greco, Iqbal Kassam, Oneil D'Silva, Ernest Tan The Mobile Servicing System (MSS) is a suite of robotic systems built by MDA to maintain, service, and provide robotic capability on the International Space Station (ISS). It includes the Robotic Workstation (RWS) (launched 2000), the Canadarm2 (launched 2001), the Mobile Base System (MBS) (launched 2002), and the Dextre (launched 2008). All four systems were certified for ten years on-orbit life. The RWS, Canadarm2 and MBS have well-exceeded their design life to-date and the Dextre is at the end of its design life.In order to extend the utilization of the MSS to support ISS missions to 2024, the Canadian Space Agency (CSA) and MDA initiated a sparing effort. From a systems reliability perspective, the main focus of the effort is to ensure sufficient spares are available to support and maintain MSS functionality and availability to the end of 2024.The main challenges with building spares are cost, schedule, and on-orbit storage availability. Flight ready spares are costly due to the need for long lead time procurement, complex workmanship, extensive testing, verification and certification. Depending on the complexity of the design, assembly time will generally take 2 + years. Additionally, limited on-orbit storage and up-mass availability to the ISS have become rising concerns. As such, it is not cost effective nor time permissive to build multiple flight ready spares for the entire MSS. CSA/MDA's Launch on Need (LON) sparing readiness methodology strives to maintain on-orbit system availability while simultaneously optimizing cost and schedule.Sparing readiness can be maintained by identifying and grouping physical and functional commonalities at the Orbital Replaceable Unit (ORU) level; the Shop Replaceable Unit (SRU) level; and/or the subassembly/component levels. To accomplish this, unique and individual common subassemblies can be built, tested, verified and placed on standby. When required on-orbit, the subassemblies/SRUs can then be integrated for the required flight ready spare. Verification is a challenging aspect in building spares due to legacy specifications written at original design and build and may not be directly applicable to building spares.This paper will summarize CSA/MDA's LON methodology in cost-effective preparation of flight spares including manufacture, assembly, test and verification. This methodology was recently applied to the successful build of two Electronics Platforms (EP) critical to Dextre's functionality and continues to prepare CSA and MDA for the extended support of the ISS to 2024 or beyond.
       
  • A distributed congestion avoidance routing algorithm in mega-constellation
           network with multi-gateway
    • Abstract: Publication date: September 2019Source: Acta Astronautica, Volume 162Author(s): Quan Chen, Xiaoqian Chen, Lei Yang, Shuai Wu, Xuefeng Tao Recently several large-scale constellation networks have been proposed, requiring inter-satellite links and multiple gateways to be equipped. The gateway assignment and traffic congestion avoidance issues are of fundamental importance for the network. In this work, we establish the network model for mega-constellation network with multi-gateway by introducing the concept of satellite router and satellite gateway. We propose a distributed routing algorithm consisting of three processes: 1) Gateway assignment; 2) Path candidate region partitioning and 3) Optimal path generation. In Optimal path generation, Longer Side Priority (LSP) strategy is proposed, aiming at maximizing the path searching space. By solving the path survival problem, LSP strategy is proved to perform better in congestion avoidance. Through simulation, we verify the routing algorithm and find the significant effects of seam movement in network performance. Results suggest that the proposed strategy performs better in load balance and congestion avoidance compared with the minimum delay strategy.
       
  • New star identification algorithm using labelling technique
    • Abstract: Publication date: September 2019Source: Acta Astronautica, Volume 162Author(s): Sangkyun Kim, Mengu Cho A new star identification algorithm is proposed for the attitude determination of a star sensor in the lost-in-space case, where prior attitude information is not available. The algorithm is based on a labelling technique, which uses label values to represent each group of stars. Using label values, multiple stars are simultaneously identified without repetition of search work. This labelling algorithm allows for a fast identification speed with efficiency, and provides the capability of more reliable identification by redundant confirmation. The proposed algorithm was verified by simulation study under various conditions.
       
  • Pendulum-type elastic metamaterial for reducing the vibration of a space
           tether
    • Abstract: Publication date: September 2019Source: Acta Astronautica, Volume 162Author(s): Joo Young Yoon, Weon Keun Song, No-Cheol Park In this paper, we present a pendulum-type elastic metamaterial that can be used to absorb the shock of a tether system. A tether system comprises a long and thin cable, so the resonant part of the elastic metamaterial should be attached to outside the cable. The unit cell of the elastic metamaterial consists of three strings and one ring, and strings are attached to the tether cable and reduces the shock transmitted to the satellite. We used modal analysis to find mode shapes of the unit cell of the elastic metamaterial that do not deform when in contact with the tether cable. A harmonic analysis on the properties of the strings confirmed the presence of bandgaps for the pendulum-type metamaterial because of the lateral resonance of the strings. The effect of the unit cell design parameters on the bandgaps were also investigated.
       
  • Nuclear microbomb propulsion for manned deep space exploration with return
           travel
    • Abstract: Publication date: September 2019Source: Acta Astronautica, Volume 162Author(s): F. Winterberg For manned deep space exploration with return travel a novel nuclear microbomb propulsion concept is proposed. It assumes the presence of easily mineable natural uranium and lithium deposits on Solar System planets. The concept makes use of large negative mass densities in a rapidly rotating reference system predicted by Hund as a consequence of Einstein's general theory of relativity. It permits the ignition of the deuterium thermonuclear reaction by the implosion of Li6D salt inside a rapidly rotating natural uranium shell by an intense relativistic electron beam of over 100 MJ. This concept avoids the drawbacks of carrying along liquid deuterium-tritium and Plutonium 239 or Uranium 235 for fission spark plugs on a deep space mission.The generation of the pulsed high-energy relativistic beams can be done by solar collectors charging the high-voltage Marx generators, or by a small natural uranium reactor, requiring not much more than a small chemical factory, not a large isotope separating facility. A small chemical plant is also needed to make the high explosives used to achieve the large rotational target velocity.
       
  • Numerical and experimental investigations on injection effects of orifice
           injector plate in hybrid rocket motors
    • Abstract: Publication date: September 2019Source: Acta Astronautica, Volume 162Author(s): Hao Zhu, Meng Li, Hui Tian, Pengfei Wang, Nanjia Yu, Guobiao Cai Orifice injector plates are widely used in hybrid rocket motors (HRM), but little work has been done on the influences of their design parameters on combustion performances of HRM. The effects of orifice diameter, injection pressure drop and orifices distribution of the orifice injector plate on combustion efficiency of HRM are investigated by experimental and numerical methods in this paper. The hydrogen peroxide (H2O2) and hydroxyl terminated polybutadiene (HTPB) with tube grain are selected as propellant. Firstly, 5 kinds of orifice injector plates with different orifice diameter and orifices distribution are designed, and 7 fire experiments are carried out. The experimental results show that the combustion efficiency of HRM increases with the decrease of orifice diameter and injection pressure drop. Moreover, the combustion efficiency of motor with plat using single-ring distribution is the highest, while the one using three-ring distribution is the lowest. Secondly, 36 orifice injector plates with different design parameters are calculated by three-dimensional numerical simulation of two-phase flow. The liquid oxidizer evaporation, solid-gas interaction, gaseous phase combustion, and turbulence are considered in the simulation model. The conclusions draw from simulation results agree with the experimental data, which illustrates the validity of numerical simulation model. The conclusions based on experimental and numerical results can provide guidance for designing high-performance orifice injector plate in HRMs.
       
  • Technical evaluation of Off-Earth ice mining scenarios through an
           opportunity cost approach
    • Abstract: Publication date: Available online 27 June 2019Source: Acta AstronauticaAuthor(s): Timothy M. Pelech, Gordon Roesler, Serkan Saydam In this paper, four Off-Earth Mining scenarios for water extraction have been designed to supply a H2/LOx propellant market in Low Earth Orbit. A non-financial measure for determining feasibility has been devised for the analysis based on the opportunity cost as opposed to the Net Present Value. The first scenario for evaluation is a conventional strip mining operation in a southern lunar crater. An ‘In-Situ Sublimation’ method in the same location has been determined to be more competitive than strip mining due to equipment mass requirements. However, neither system can compete with direct launch of water from the Earth based on the assumptions in this research. The third and fourth scenarios are based on a near Earth dormant comet and also utilize In-Situ Sublimation techniques. These scenarios focus heavily on transport optimization. A single miner-hauler system was found to be inferior to the multi-craft system. It was also revealed that the dormant comet mining scenarios will not be competitive enough with lunar mining or direct launch from Earth to supply a Low Earth Orbit market.
       
  • Growth and biomass yield of 25 crops in the 4-subject 180-day integrated
           experiment
    • Abstract: Publication date: Available online 24 June 2019Source: Acta AstronauticaAuthor(s): Jialian Li, Nan Zhang, Jie Luo, Qingni Yu, Weidang Ai, Liangchang Zhang, Yongkang Tang To support human life during deep space exploration, the cultivation of higher plant plays a critical role in sustaining gas, water, and nutrient cycles in Controlled Ecological Life Support System (CELSS). This study aimed to develop crop co-cultivation and highly efficient production techniques, explore diverse plant growth patterns, and evaluate the capability of continuous production in a long-term closed environment. Twenty-five crops, including 1 grain, 2 tubers, 2 oil plants, 2 fruits, 3 functional plants, and 15 vegetables, were selected for their nutrient content, growth cycle, and environmental requirement. Depending on their requirements of light source, photoperiod, nutrient solution, and temperature, 25 crops were distributed in 4 separate cabins, which spanned 195.36 square meters in total. Most wheat were grown in a nutrient solution, whereas a small portion of wheat and the other crops were grown in a solid substrate, in order to recycle solution and solid wastes properly. Throughout the trial period, most of these crops adapted to the closed environment and completed the whole growth and development cycle normally. The results showed that the crop cultivation system could continuously provide a variety of vegetables and fruits at a rate of 1.43  kg d−1 (fresh weight) for 4 crews in the 180-day experiment and at a rate of 1.30 kg d−1 (dry weight) grains and tubers in the last 60 days. The harvest index of sweet potato was higher than that of wheat and potato, whereas its yield per unit area was similar to that of wheat. Since the harvest of the first batch of grains and tubers, crops grown in the cabins gradually became the main source of crews' diet. In addition, various cultivars displayed distinct differences in growth and yield under the same conditions. Further research in crop cultivation in CELSS should focus on the adaptability and adaptation mechanisms of the cultivated varieties.
       
  • Establishment and control of spacecraft formations using artificial
           potential functions
    • Abstract: Publication date: Available online 21 June 2019Source: Acta AstronauticaAuthor(s): Sylvain Renevey, David A. Spencer The automated control of spacecraft formations in specified relative orbits is a challenging problem that is computationally intensive using traditional methods of numerically integrating trajectories and applying optimal control theory. In this paper, relative orbital elements and artificial potential functions are combined into a methodology that allows full control of the relative orbits of spacecraft formations. This method enables the intuitive design of geometrically complex formations, and allows collision avoidance during the formation establishment. The effectiveness of the control algorithm is illustrated with the numerical simulation of the establishment of various formation geometries.
       
  • Hypersonic flow over Stardust Re-entry Capsule using ab-initio based
           chemical reaction model
    • Abstract: Publication date: Available online 19 June 2019Source: Acta AstronauticaAuthor(s): Tapan K. Mankodi, Upendra V. Bhandarkar, Bhalchandra P. Puranik Hypersonic air flow around the Stardust Re-entry Vehicle for diverse ambient conditions is investigated using the Direct Simulation Monte Carlo (DSMC) method. In the present work, the flow field and surface properties on the re-entry vehicle are compared for simulations employing two different chemical reaction models: the traditional phenomenological Total Collision Energy (TCE) model and a new chemical reaction model based on ab-initio principles. The reactive cross-section used in the new chemical reaction model are calculated using Quasi-Classical Trajectory method and employs highly accurate Potential Energy Surfaces. Conditions prevailing at 68 km, 80 km and 100 km are simulated and for two re-entry speeds. It is found that the DSMC simulations with the new ab-initio based chemical reaction model predicts higher heat flux and heat load on the re-entry vehicle surface compared to the simulations employing the TCE model. The difference in the heat flux predicted by the two models is most evident at 80 km. This is a significant inference for engineers designing the Thermal Protection Systems. It is observed that there are significant differences in the estimation of mole fraction of NO by the two models. The limitations of the present model and future scope are discussed in detail.
       
  • Fraunhofer satellite radiation sensing systems
    • Abstract: Publication date: Available online 17 June 2019Source: Acta AstronauticaAuthor(s): Stefan Metzger, Stefan Höffgen, Christoph Komrowski, Jochen Kuhnhenn, Tobias Kündgen, Michael Steffens Fraunhofer INT develops systems for on-board radiation sensing. On-board in this context means inside electronic boxes on printed circuit boards (PCB) in close proximity to radiation sensitive electronic devices. The ability to measure dose and/or particle fluxes on the PCB is particularly of interest as this is where radiation hurts the most. In case of intense solar particle events the sudden increase of the measured particle fluxes could be used as an input for adaptive radiation mitigation techniques to protect important electronic parts and systems. Furthermore it can help to reduce radiation design margins for future missions because you get a better knowledge of the received dose inside your electronic box in a given radiation environment. In addition in the case of in-orbit verification or validation missions it is of major importance to verify the reliability of your design against the actual dose received. Our approach is to add as little devices as possible and make use of already installed hardware e.g. microprocessors to operate them, so the output of those sensor devices should already be digital. We propose to integrate additional memory devices for radiation sensing on the PCB: non-volatile UV-EPROMs to measure dose and/or SRAMs to detect high energy (solar) particles. The radiation-induced change of their digital content is a measure for the radiation exposure after calibration in a known radiation field. Fraunhofer On-board Radiation Sensors are already accepted to fly on the German geostationary Heinrich Hertz communication satellite as part of the Fraunhofer On-Board Processor and is foreseen to be implemented on-board of a NanoSat.
       
  • Flowfield structures of pylon-aided fuel injection into a supersonic
           crossflow
    • Abstract: Publication date: Available online 15 June 2019Source: Acta AstronauticaAuthor(s): Yuan Liu, Ming-bo Sun, Chang-hai Liang, Jiang-fei Yu, Guang-xin Li Flowfield structures of pylon-aided fuel injection of a sonic jet into a supersonic crossflow with Ma = 2.95 have been investigated by Nanoparticle-based Planar Laser Scattering (NPLS) technique and oil flow technique, seperately. Two experimental cases have been done for jet-to-crossflow momentum flux ratios (J) of 7.7 and 20.6, respectively, and the results are compared with those obtained by normal injection of a single jet from a flat plate without a pylon. Experimental results indicate that the flow structures of pylon-aided injection cases are very similar to those found in the normal injection cases in the downstream region of the jet. Upstream of the jet orifice, the detached shock generated at the leading edge of the pylon is identified by inserting with the separation shock. For lower injection pressure case there is always larger influences of the pylon in the flow structures in terms of jet plums’ position and the shock intensity. Besides, the mechanism of mixing enhancement resulting from the pylon is also elaborated in the present work.
       
  • End-to-end mission design for microbial ISRU activities as preparation for
           a moon village
    • Abstract: Publication date: Available online 14 June 2019Source: Acta AstronauticaAuthor(s): B.A.E. Lehner, J. Schlechten, A. Filosa, A. Canals Pou, D.G. Mazzotta, F. Spina, L. Teeney, J. Snyder, S.Y. Tjon, A.S. Meyer, S.J.J. Brouns, A. Cowley, L.J. Rothschild In situ resource utilization (ISRU) increasingly features as an element of human long-term exploration and settlement missions to the lunar surface. In this study, all requirements to test a novel, biological approach for ISRU are validated, and an end-to-end mission architecture is proposed. The general mission consists of a lander with a fully autonomous bioreactor able to process lunar regolith and extract elemental iron. The elemental iron could either be stored or directly utilized to generate iron wires or construction material. To maximize the success rate of this mission, potential landing sites for future missions are studied, and technical details (thermal radiation, shielding, power-supply) are analyzed. The final section will assess the potential mission architecture (orbit, rocket, lander, timeframe). This design might not only be one step further towards an international “Moon Village”, but may also enable similar missions to ultimately colonize Mars and further explore our solar system.
       
  • GNC & robotics for on orbit servicing with simulated vision in the loop
    • Abstract: Publication date: Available online 14 June 2019Source: Acta AstronauticaAuthor(s): Aureliano Rivolta, Paolo Lunghi, Michèle Lavagna Complex robotics missions require complex GNC and Robotics algorithms, often using vision sensors. The problem of vision-in-the-loop GNC is addressed using photorealistic simulated images and simple computer vision algorithms, coupled with relative estimation and control of a servicing satellite in close proximity operations with a customer satellite. In the near future it will be required to simulate the behavior of automated servicing missions comprehending also vision data, hence the request for vision-in-the-loop simulations. In this article is proposed a GNC and Robotics scheme for proximity operations between a servicer and a customer satellite through the use of adaptive control and computer vision. The scheme is then put to test through simulation of orbital robot dynamics, sensors and camera inputs, and computer vision algorithm in the loop.
       
  • Space as an enabler in the maritime sector
    • Abstract: Publication date: Available online 14 June 2019Source: Acta AstronauticaAuthor(s): Angeliki Papadimitriou, Katherine Pangalos, Isabelle Duvaux-Béchon, Christina Giannopapa Space can be used as a tool for business decision and policy makers. The maritime sector is rapidly evolving as far as business and industrial activities are concerned. Space can assist in transforming this sector through satellite navigation and positioning, telecommunications and integrated applications as well as earth observation. Additionally, space can be used as a tool in developing, implementing maritime affairs. This papers focuses on the role of space in maritime policy. Space technologies have been serving the maritime community for over fourty years. Satellite technology is becoming increasingly important for a wide range of maritime activities through enhanced navigation accuracy, marine environmental monitoring and maritime surveillance. For this reason, agreements between the European Space Agency (ESA) and the European Maritime Safety Agency (EMSA), have been signed in 2007 and 2010, strengthening the framework for cooperation between the two agencies for the use of space-based systems in support of maritime activities. The first part of the paper summarises European maritime related policy areas where space assets can contribute to achieve their objectives. The second part of the paper addresses how ESA's initiatives and programs could contribute and support the maritime sector in Europe. The main purpose of this paper is to come up with conclusions on whether and how the use of space assets, technology and applications, can contribute in achieving the maritime policy objectives for the benefit of Europe.
       
  • Fuzzy dipole magnetic control law
    • Abstract: Publication date: Available online 13 June 2019Source: Acta AstronauticaAuthor(s): Pedro A. Capo-Lugo, John Rakoczy This paper presents a new fuzzy logic system that decouples the measured Earth's magnetic field problem from the control analysis. The fuzzy logic takes care of the coupling between the magnetic field lines so that a classical controller is used to determine the necessary magnetic dipole moment to hold the satellite attitude motion. Although the fuzzy logic can have rules based on the vehicle states, the present method takes advantage of the magnetic field knowledge so that the controller can be simplified. In order to verify this method, an orbiting satellite was used to test this control system. Even though this method was used for a small satellite class, this control technique could be applied to nano and pico satellites using magnetic torquers.
       
  • The Thermocapillary Effects in Phase Change Materials in Microgravity
           experiment: Design, preparation and execution of a parabolic flight
           experiment
    • Abstract: Publication date: Available online 11 June 2019Source: Acta AstronauticaAuthor(s): J.M. Ezquerro, A. Bello, P. Salgado Sánchez, A. Laverón-Simavilla, V. Lapuerta The Thermocapillary Effects in Phase Change Materials in Microgravity (TEPiM) experiment aims to analyse the potential of Marangoni convection for heat transfer enhancement in Phase Change Materials (PCMs) in weightlessness, where the slow characteristic time of the phase change process constrains their use as thermal control devices. On ground, natural convection masks the influence of Marangoni flow, which means that quantifying each contribution to the heat transfer rate of the system precisely is not possible. In this sense, the microgravity environment provided by parabolic flights gives an excellent opportunity to execute an experiment on PCMs phase change coupled with thermocapillary convection, and retrieve useful data to validate theoretical and numerical models. We note that such microgravity research has never been performed prior to this project.In this paper, we describe the design, preparation and performance of the TEPiM microgravity experiment, executed during the 65th ESA Parabolic Flight campaign. The experiment cells, filled with solid n-octadecane and a layer of air, were heated to observe the melting process under the microgravity portions provided during the flight. The promising results obtained support the positive impact of thermocapillary effects in PCMs melting, and suggest themselves for further investigation. We also expect that the valuable lessons learned presented here will help the scientific community in developing future microgravity experiments of this nature.
       
  • Experimental study of severity level of structural discontinuities in
           paraffin grains of hybrid propellant rocket
    • Abstract: Publication date: Available online 11 June 2019Source: Acta AstronauticaAuthor(s): Artem Andrianov, Jungpyo Lee, Olexiy Shynkarenko, Domenico Simone, Artur Elias De Morais Bertoldi
       
  • Second-generation Micro-Spec: A compact spectrometer for far-infrared and
           submillimeter space missions
    • Abstract: Publication date: Available online 11 June 2019Source: Acta AstronauticaAuthor(s): Giuseppe Cataldo, Emily M. Barrentine, Berhanu T. Bulcha, Negar Ehsan, Larry A. Hess, Omid Noroozian, Thomas R. Stevenson, Edward J. Wollack, Samuel H. Moseley, Eric R. Switzer Micro-Spec is a direct-detection spectrometer which integrates all the components of a diffraction-grating spectrometer onto a ≈10-cm2 chip through the use of superconducting microstrip transmission lines on a single-crystal silicon substrate. The second generation of Micro-Spec is being designed to operate with a spectral resolution of at least 512 in the far-infrared and submillimeter (420–540 GHz, 714–555 μm) wavelength range, a band of interest for NASA's experiment for cryogenic large-aperture intensity mapping called EXCLAIM. EXCLAIM will be a balloon-borne telescope that is being designed to map the emission of redshifted carbon monoxide and singly-ionized carbon lines over a redshift range 0
       
  • Mixing characteristics of cracked gaseous hydrocarbon fuels in a scramjet
           combustor
    • Abstract: Publication date: Available online 10 June 2019Source: Acta AstronauticaAuthor(s): Magesh Ravindran, Mathew Bricalli, Adrian Pudsey, Hideaki Ogawa High-performance hydrocarbon-fuelled scramjet engines require efficient fuel-air mixing due to the relatively short flow residence time through the combustor. At high temperatures, hydrocarbon fuels react endothermically and absorb thermal energy from the surroundings. The process known as cracking becomes essential at high Mach numbers to increase the total heat-sink capacity of the fuel. This study presents the results of chemically frozen numerical simulations that investigate the mixing characteristics of cracked gaseous heavy hydrocarbon fuels injected through a circular, flush-wall porthole injector. The mixing characteristics of fuel compositions representing cracking efficiencies ranging from 0 to 100% are investigated. The mixing rates and flow structures are found to change with fuel compositions. As the cracking increases, the mixing and streamwise circulation increase for an injectant. However, the jet penetration and stagnation pressure losses decrease. The streamwise circulation is found to have a strong influence on the mixing, the injection pressure on the jet penetration and the strength of the bow shock on stagnation pressure losses. Overall, it is shown that there are mixing benefits to be gained by injecting cracked hydrocarbon fuels compared to heavy uncracked fuels in scramjets.
       
  • Near-term interstellar probe: First step
    • Abstract: Publication date: Available online 10 June 2019Source: Acta AstronauticaAuthor(s): Ralph L. McNutt, Robert F. Wimmer-Schweingruber, Mike Gruntman, Stamatios M. Krimigis, Edmond C. Roelof, Pontus C. Brandt, Steven R. Vernon, Michael V. Paul, Brian W. Lathrop, Douglas S. Mehoke, David H. Napolillo, Robert W. Stough Exploration of the heliosphere and the far reaches of our solar system by the Voyagers and New Horizons and near-Earth observations of the Kuiper Belt and exoplanetary systems have all profoundly changed how we view our own home in space. An Interstellar Probe escaping beyond the solar-system boundaries with new observational techniques would be a bold move in space exploration, enabling detailed, new understanding of the global heliosphere in the context of other astrospheres, further discoveries of unexplored Kuiper Belt Objects, and the first observations of our circumsolar dust disk. These would offer insight into the evolution of the solar system and our understanding of exoplanetary systems. With the power supplies on the Voyagers nearing their end of life, the rapid pace of discovery of exoplanets in other stellar systems, and the evolution in our own understanding brought about by results from the Voyager, Cassini, and Interstellar Boundary Explorer (IBEX) spacecraft, the time is right for looking at the next steps we can make into our stellar neighborhood. The question facing us today is what the appropriate next step - a true first step - is in negotiating the transition from science fiction to engineering reality. The scientific imperatives associated with reaching the near interstellar medium in order to understand our origins and our own current locale in the Milky Way trace to the beginnings of the Space Age, and they have been debated and refined since that time and into the current epoch. The subjects of interstellar travel, interstellar probes, and interstellar “precursor” missions are not new but have lacked traction with policy makers and the scientific community at large because of the states of both scientific.knowledge and engineering realities. The next step in reaching to the stars will require the recognition of engineering limits, scientific trades, and scientific compromises, but this is new neither in science nor exploration. Such a step would be an “Interstellar Probe.” The time for that step has come.
       
  • Theoretical study of the flame describing function of AP/HTPB propellant
           flame based on sandwich model
    • Abstract: Publication date: Available online 6 June 2019Source: Acta AstronauticaAuthor(s): Guanyu Xu, Peijin Liu, Wen Ao, Bingning Jin The flame dynamics of ammonium perchlorate/hydroxyl-terminated polybutadiene (AP/HTPB) composite propellant subject to the acoustic oscillation in a solid rocket motor (SRM) is investigated numerically in this article. The sandwich model is suitably modified to carry out the simulations of propellant combustion under unsteady conditions and the flame response to the acoustic oscillations with different amplitudes and frequencies is investigated. Attention is focused on the heat flux to the propellant surface and the Flame Describing Function (FDF) is utilized to capture the characteristics of the heat feedback under different forcing amplitudes and frequencies. The results indicate the flame responses are non-linear for the first longitudinal mode of acoustic oscillation and the gain of the fluctuating heat feedback reaches the point saturation at the high forcing amplitude. For high forcing frequency (the third acoustic mode), the gain of the fluctuating heat feedback shows insensitivity to the acoustic oscillations with different amplitudes and varies little. The full FDF confirms the nonlinearity of the gain response and shows the trend of fluctuating heat feedback as a function of different forcing frequencies and amplitudes.
       
  • A person-following nanosatellite for in-cabin astronaut assistance: System
           design and deep-learning-based astronaut visual tracking implementation
    • Abstract: Publication date: Available online 5 June 2019Source: Acta AstronauticaAuthor(s): Rui Zhang, Zhaokui Wang, Yulin Zhang An intelligent, person-following nanosatellite is under development for in-cabin astronaut assistance in the China Space Station. It is named the Intelligent Formation Personal Satellite (IFPS). The satellite weighs 2.0 kg and is shaped as a sphere of diameter 230 mm. Fans and MEMS flywheels are used for its position and attitude maneuvering as inside the Space Station cabin it is a weightless and standard atmospheric pressure environment. The RGB-D camera and IMU based visual-inertial SLAM method is used to support its localization and navigation. The on-board information processing and computing hardware primarily consists of an embedded AI microprocessor and an FPGA. The satellite is designed to fly autonomously and follow the designated astronaut to offer immediate assistance. Thus, efficient and robust astronaut visual tracking is the most important prerequisite for supporting its basic person-following operating mode. We achieved this by further improving our previously proposed tracking algorithm that consists of a deep convolution neural network (DCNN)-based detection module and a probabilistic-model-based tracking module. The DCNN in the detection module was further improved through optimizations of lightweight network architecture design, parameters model compression and inference acceleration. While maintaining the originally high detection accuracy, the DCNN was optimized significantly in terms of memory, computation and power consumption to quite meet the engineering constraints in the development of IFPS. The complete pipeline of the astronaut visual tracking algorithm was also designed and implemented in the embedded AI microprocessor for online tracking application. Experimental results demonstrated the effectiveness of the proposed efficient and robust astronaut detection and tracking algorithm.
       
  • Experimental evaluation of thermoelectric generators for nanosatellites
           application
    • Abstract: Publication date: September 2019Source: Acta Astronautica, Volume 162Author(s): A.L.A. Ostrufka, E.M. Filho, A.C. Borba, A.W. Spengler, T.S. Possamai, K.V. Paiva Energy generation is a crucial need for every kind of space vehicle, including CubeSats, a type of nanosatellite. Nowadays, the main component used to generate electric power is the solar panel. However, due to area restriction and solar panel low efficiency, other technologies are being studied to improve the overall power generation capacity in CubeSats. This paper presents an experimental study of a thermoelectric generator (TEG) for electric energy generation through temperature gradients from solar panels in CubeSats. The generation capacity is analyzed for different positioning configurations of the TEG relative to each CubeSat surface. In addition, TEG performance is evaluated considering two different kinds of energy harvesting circuits, responsible for storing and managing the generated energy. Using temperature variation profiles obtained by numerical analysis for a real CubeSat mission, it was possible to determine the amount of power generated by a TEG module from the heat waste from solar panels. As a result, a comparison process between TEG and solar panel generation systems themselves was conducted. It was verified that the proposed system can generate up to 9.62% of the energy generated by the conventional solution, considering energy harvesting storing efficiency of 10%.
       
  • Experimental study on the coupling process of flow and combustion
           phenomena during pilot ignition transients
    • Abstract: Publication date: September 2019Source: Acta Astronautica, Volume 162Author(s): Yu Pan, Xipeng Li, Weidong Liu, Ning Wang The pilot ignition of kerosene under different pre-established hydrogen flames is performed in a model scramjet combustor with the isolator entrance Mach number of 2.52, the total pressure of 1.6 MPa, and stagnation temperature of 1486 K, which corresponds to Ma 5.5 flight condition. The flame dynamics and evolvement of the precombustion shock train during pilot ignition transients are acquired through high-speed photography and schlieren photography. The flame stabilization mode of pilot hydrogen belongs to cavity-recirculation-region stabilized combustion with smaller equivalence ratio. While the flame stabilization mode turns into jet-wake stabilized combustion as the equivalence ratio of pilot hydrogen increases. Liquid kerosene can not be ignited by cavity-recirculation-region stabilized flame, while it can be ignited successfully by pilot hydrogen flame stabilized in the jet-wake. Thermal choking resulted from combustion of the pilot fuel should be large enough to produce and sustain the precombustion shock train in the combustor for igniting liquid kerosene. There is a positive feedback mechanism between combustion and flow dynamics. The backpressure caused by combustion produces and sustains the precombustion shock train, which in turn increases combustion intensity. The positive feedback mechanism lasts until a new balance between combustion and flow phenomena is achieved. Boundary-layer separation is the main reason for the upstream propagation of flame, which is a result of the large adverse pressure gradient caused by heat release.
       
  • SETI in Russia, USSR and the post-Soviet space: a century of research
    • Abstract: Publication date: September 2019Source: Acta Astronautica, Volume 162Author(s): Lev M. Gindilis, Leonid I. Gurvits Studies on extraterrestrial civilisations in Russia date back to the end of the 19th century. The modern period of SETI studies began in the USSR in the early 1960s. The first edition of the I.S. Shklovsky's book Universe, Life, Intelligence published in 1962 was a founding stone of SETI research in the USSR. A number of observational projects in radio and optical domains were conducted in the 1960s–1990s. Theoretical studies focused on defining optimal spectral domains for search of artificial electromagnetic signals, selection of celestial targets in search for ETI, optimal methods for encoding and decoding of interstellar messages, estimating the magnitude of astro-engineering activity of ETI, and developing philosophical background of the SETI problem. Later, in the 1990s and in the first two decades of the 21st century, in spite of acute underfunding and other problems facing the scientific community in Russia and other countries of the former Soviet Union, SETI-oriented research continued. In particular, SETI collaborations conducted a number of surveys of Sun-like stars in the Milky Way, searched for Dyson spheres and artificial optical signals. Several space broadcasting programs were conducted too, including a radio transmission toward selected stars. Serious rethinking was given to incentives for passive and active participation of space civilisations in SETI and CETI. This paper gives an overview of past SETI activities. It also gives a comprehensive list of publications by authors from Russia, the Soviet Union and the post-Soviet space, as well as some SETI publications by other authors. The rich heritage of SETI research presented in the paper might offer a potentially useful background and starting point for developing strategy and specific research programs of the near future.
       
  • Constrained fuel-free control for spacecraft electromagnetic docking in
           elliptical orbits
    • Abstract: Publication date: September 2019Source: Acta Astronautica, Volume 162Author(s): Keke Shi, Chuang Liu, Zhaowei Sun This paper addresses the control problem of spacecraft electromagnetic docking in the presence of external disturbances, fault signals, elliptical eccentricity, and input magnitude and rate constraints (MRCs). More specifically, the dynamic model of translational motion in an elliptical orbit is derived first; by analyzing the influence of external disturbances, fault signals and elliptical eccentricity, a lumped disturbance is reconstructed to facilitate the controller design. Then, a state feedback control strategy based on disturbance observer, i.e. a disturbance observer-based controller (DOBC), is proposed, where the compensation of the lumped disturbance is considered. This controller thus has the nature of fault tolerance and robustness, and it requires no mass information on chaser or target spacecraft, no information on external disturbances, fault signals or even orbital elements except for semi-major axis. By choosing new state variables using the information on relative motion and estimation errors, an augmented plant is established. Using Lyapunov stability analysis, which shows that all states are uniformly ultimately bounded, sufficient conditions for the existence of the disturbance observer and controller subject to input MRCs are given based on linear matrix inequalities (LMIs). Numerical simulations are performed to demonstrate the validity and performance of the proposed strategy.
       
  • Lyapunov-based low-energy low-thrust transfers to the Moon
    • Abstract: Publication date: Available online 5 June 2019Source: Acta AstronauticaAuthor(s): R. Epenoy, D. Pérez-Palau This paper investigates the numerical computation of low-fuel low-thrust Earth-Moon transfers in a full ephemeris model incorporating the gravitational influence of the Sun, the Moon and all planets of the solar system plus the solar radiation pressure perturbation based on a sample spacecraft area and mass. First, an initial velocity increment to be provided by the launcher is computed. This initial impulse puts the spacecraft on the counterpart in the full ephemeris model of a stable invariant manifold defined in the Sun-Earth Circular Restricted Three-Body Problem. Then, after a coast arc, a closed-loop thrust law is applied to bring the spacecraft to the target lunar orbit. This control law is based on Lyapunov control theory. More precisely, a control-Lyapunov function is defined as the weighted quadratic distance between the first five equinoctial orbital elements of the spacecraft in a Moon-centered reference frame and those defining the target lunar orbit. The control is computed in such a way so as to make the time derivative of the control-Lyapunov function as negative as possible. Numerical results are provided first for a transfer with constant maximum thrust. Then, it is shown that unlike in the case of an open loop control, concentrating the thrust in the vicinity of the perilune and the apolune increases the transfer duration but without reducing the fuel consumption. This is largely due to the uncontrolled effect of the perturbations acting on the spacecraft during the coast arcs. Finally, the robustness of the guidance law against unexpected engine shutdown events is demonstrated.
       
  • Experimental and numerical study of solid rocket scramjet combustor
           equipped with combined cavity and strut device
    • Abstract: Publication date: Available online 31 May 2019Source: Acta AstronauticaAuthor(s): Chaolong Li, Zhixun Xia, Likun Ma, Xiang Zhao, Binbin Chen In this paper, a new solid rocket scramjet equipped with two combined cavity and strut device was studied by experimental and numerical approaches. The experiment simulated a flight Mach number 5.5 at 23 km. Hydrocarbon type fuel was used as the solid fuel-rich propellant. Three-dimensional Reynolds-averaged Navier–Stokes equations coupled with shear stress transport k−ω turbulence model are employed to simulate the flow field in the solid rocket scramjet combustor. The numerical method was validated by experimental data. The experimental results show that the combined cavity and strut device can play a role as ignition and flame holding in the solid rocket scramjet combustor. Additionally, the numerical results show that the combustion of gas and particle phase is conducted sequentially rather than simultaneously. And the total combustion efficiency mainly depends on the particle combustion. The total combustion efficiency is about 0.7 and the total pressure recovery is about 0.25 in this test. The combined cavity and strut device do improve the combustion efficiency in the solid rocket scramjet. However, the total pressure recovery is a rather low. Aerodynamic configuration optimization of the combined cavity and strut device will be carried out in the next step.
       
  • Novel osculating flowfield methodology for wide-speed range waverider
           vehicles across variable Mach number
    • Abstract: Publication date: Available online 31 May 2019Source: Acta AstronauticaAuthor(s): Jun Liu, Zhen Liu, Xun Wen, Feng Ding In order to guarantee the good aerodynamic performance of the waverider vehicle in the wide-speed range, the variable Mach number osculating flowfield waverider design theory based on conical basic flowfield is put forward. The shape and aerodynamic characteristics of the variable Mach number osculating flowfield waverider and osculating cone waverider are compared and analyzed. And the inviscid numerical simulation method is used to verify the correctness of the theory and the validity of the design method. The obtained results show that the osculating flowfield waverider has good waverider properties under the conditions of wide-ranged flight Mach numbers. Furthermore, the comparison of osculating flowfield waverider and osculating cone waveriders indicates that the variable Mach number osculating flowfield waverider has balanced internal loading capacity and aerodynamic performance, which is more suitable for wide-speed flight.
       
  • HI-SEAS habitat energy requirements and forecasting
    • Abstract: Publication date: Available online 31 May 2019Source: Acta AstronauticaAuthor(s): S.T. Engler, K. Binsted, H. Leung Travel to other planetary bodies represents a major challenge to resource management. Previous manned exploration missions of long duration have been resupplied with food, water, and air as required. Manned missions to other planetary bodies will have durations of years with little to no possibility of resupply. Consequently, monitoring and forecasting resource consumption are mission-critical capabilities. The Hawaii Space Exploration Analog and Simulation, a long-duration planetary analog simulation, has recently completed its fifth long-term isolation mission conducted to assess the energy, food, and water needs of a six-person long-term planetary mission. This study presents a novel method for forecasting energy consumption, which incorporates the emotional state of the habitat crew. Gathered data show inhabitants in small environments can be influenced considerably by the actions of a single member. This can result in dramatic changes in consumption that could cause forecasting models to deviate to the point of total failure. Previous work found that inclusion of the daily activities and the psychological states of the crew allows for higher accuracy in long-duration forecasts. Currently, psychological assessments in the form of a Positive and Negative Affect Schedule and a generalized artificial neural modulation method are used to incorporate emotional response into machine learning forecast methods. Using these techniques and developments, a large-scale smart habitat control and forecasting system is proposed that will monitor, control, and forecast HI-SEAS habitat resources for future HI-SEAS missions. This new system requires the incorporation of psychological and physiological data of the crew, together with information on their activities and schedules.
       
  • Study on ignition process of air/liquid oxygen/ethanol tripropellant
           coaxial jets in a subscale air heater
    • Abstract: Publication date: Available online 28 May 2019Source: Acta AstronauticaAuthor(s): Chibing Shen, Lei Yuan Up to the present, no studies have been published to investigate the ignition process in air heater. In this paper, spray combustion flow field during ignition process in air heater was first visualized by high-speed shadowgraph technique. High-speed shadowgraph movies and pressure data indicated that ignition-quenching–reignition phenomenon occurred during one test run. The experimental results demonstrated that combustion of the accumulated propellant mixture during a very short period led to a peak pressure at the moment of last ignition. This process caused reverse flow of flame and ethanol spray into air injector annulus, which was one of the reasons leading to local ablation of injector. In order to obtain reliable ignition, effective improvements were necessary.
       
  • Numerical investigation of deflagration to detonation transition in closed
           ducts under various working conditions
    • Abstract: Publication date: Available online 27 May 2019Source: Acta AstronauticaAuthor(s): Reza Soleimanpour, Hossain Nemati In the present study, a turbulent deflagration to detonation transition in gas mixtures of H2–O2 with a vertical concentration gradient in a closed duct was investigated numerically using OpenFOAM package. In this regard, the computational model is based on accounts for deflagrative flame propagation, autoignition as well as the formulation of a reaction progress variable. The simulation was carried out with several reaction mechanisms such as Warnatz, Oran, Ó-Conaire, Detailed, Skeletal, and GRI 2.11 mechanisms. It works on relatively coarse grids and indicates a good agreement with available experiment data when the Ó-Conaire mechanism was used. After validation of the numerical results, the DDT behavior was investigated under different working conditions including detonation in wavy closed ducted. Furthermore, the effects of the initial ignition power were investigated. The results were shown that changes in the duct geometry and initial ignition power have sensitive effects of DDT structure.
       
  • Relative motion and thrust estimation of a non-cooperative maneuvering
           target with adaptive filter
    • Abstract: Publication date: Available online 25 May 2019Source: Acta AstronauticaAuthor(s): Zhai Guang, Zhao Hanyu, Wen Qiuqiu, Liang Bin With the rapid increase in the number of spacecraft in outer space, the unknown maneuvers of a spacecraft significantly increase the probability of a collision between neighborhoods. In order to guarantee the safety of an operational spacecraft, we need to estimate and predict the relative trajectories of a non-cooperative target in real time. Traditional filter routines are ineffective when the target spacecraft performs unknown continuous maneuvers. In this work, we focus on the development of relative estimators with enhanced robustness against unknown maneuvers. First, a variable state dimension estimator based on filter switching and covariance inflation is proposed to adaptively cope with a constant unknown maneuver. To strengthen the robustness in response to the time-varying maneuvers, a novel observer-enhanced Kalman filter is subsequently proposed by incorporating an observer into the filtering routines. Finally, the performance of the proposed estimators is evaluated with a series of numerical simulations, both the advantages and the disadvantages are analyzed using the simulation results.
       
  • Climbing performance analysis of rocket-based combined cycle engine
           powered aircraft
    • Abstract: Publication date: Available online 25 May 2019Source: Acta AstronauticaAuthor(s): Yicong Jia, Wei Ye, Peng Cui, Wanwu Xu Evaluating the climbing performance of rocket-based combined cycle (RBCC) powered aircraft has a guiding role for single-stage to orbit. This study establishes a new modularized thrust model of the RBCC engine for low speeds (Ma∞ = 0.8–3) based on independent ramjet stream and pressure matching. The model can quickly estimate the quasi one-dimensional flow characteristics of secondary flow and primary flow at given runner geometry and operating conditions. Comparison with experimental results shows that the thrust model is correct. In this model, the influence of altitude, Mach number, and rocket flow on thrust and specific impulse is considered. The model was used to optimize the climbing trajectory of RBCC powered aircraft with a typical lifting-body. The comparison of RBCC propulsion and pure rocket propulsion shows that the former offers propellant saving advantages. During the climb, the RBCC powered aircraft needs to strictly control the air flow rate and ensure the pressure matching in the flow path to improve propulsion efficiency.
       
  • Experimental and numerical study on thermodynamic characteristics in a
           Z-shaped evaporating pilot-flameholder
    • Abstract: Publication date: Available online 24 May 2019Source: Acta AstronauticaAuthor(s): Junjie Miao, Yuxin Fan, Tianchi Liu, Weiqiu Wu Reliable ignition and flame stability are crucial, particularly for the increasing expansion of flight envelopes. Herein, a novel Z-shaped evaporating pilot-flameholder is put forward to overcome critical challenges; further, the flameholder's ignition, blowout, and fully-developed flame characteristics under the operating conditions of turbine-based combined cycle combustors are experimentally investigated with the numerical flow field. The dynamic ignition process and the equivalence ratio of flame are acquired using a high-speed color camera and processed using an image-processing algorithm. The experimental results confirm the high ignition and blowout performance of the Z-shaped evaporating flameholder resulting from the superiority of its evaporating atomizer and Z-shaped structure. The ignition process of the Z-shaped flameholder simultaneously generates the diffusion and premixed flame types. The ignition performance of Z-shaped flameholder is significantly affected by the premixed degree of the pilot flame, which is a comprehensive index of the fuel atomization, evaporation, and turbulent mixing. The reflux rate and the premixed degree after ignition are little affected by the operating conditions, and the blowout performance is mainly influenced by the flow residence time and temperature. Further, the local equivalence ratio of the flame is acquired by calibrating the green/blue and equivalence ratios. Changing the equivalence ratio alters the double-reaction-zone feature in the Z-shaped evaporating flameholder. Under low fuel-lean conditions, flame stability is mainly contributed by the secondary reaction zone.
       
 
 
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