Origami-based structures have expanded in recent years due to new mathematical formulations along with materials that can achieve the bending requirements, often in the form of composites. While current methods of manufacturing can produce complex structures, they lack the ability to scale efficiently. A novel manufacturing technique is discussed in this work that allows for a simpler and lower cost fabrication that can scale to larger structures through robotic deposition. Samples made from this technique are investigated to understand the mechanical bending performance and effect on the tensile properties. Results show an orientation-dependent response for the material with the 45° samples having a direct impact on the tensile response. However, their bending response proved to be stiffer compared to the [Formula: see text] samples, holding more consistent bend radii. Joint stacking was also investigated, where discrete layers were not bonded together and showed an increase in force required to bend compared to the completely bonded samples. The results provide insight into how integrated composite hinges can perform in complex structures. The advancement of composite origami technology additionally works to reduce the overall number or parts and fasteners that are needed to achieve detailed deployable structures.
{"title":"Impact of Joint Parameters on Performance of Self-Opening Dual-Matrix Composites","authors":"Charles White, Jordan A. Firth, M. Pankow","doi":"10.2514/1.a35383","DOIUrl":"https://doi.org/10.2514/1.a35383","url":null,"abstract":"Origami-based structures have expanded in recent years due to new mathematical formulations along with materials that can achieve the bending requirements, often in the form of composites. While current methods of manufacturing can produce complex structures, they lack the ability to scale efficiently. A novel manufacturing technique is discussed in this work that allows for a simpler and lower cost fabrication that can scale to larger structures through robotic deposition. Samples made from this technique are investigated to understand the mechanical bending performance and effect on the tensile properties. Results show an orientation-dependent response for the material with the 45° samples having a direct impact on the tensile response. However, their bending response proved to be stiffer compared to the [Formula: see text] samples, holding more consistent bend radii. Joint stacking was also investigated, where discrete layers were not bonded together and showed an increase in force required to bend compared to the completely bonded samples. The results provide insight into how integrated composite hinges can perform in complex structures. The advancement of composite origami technology additionally works to reduce the overall number or parts and fasteners that are needed to achieve detailed deployable structures.","PeriodicalId":50048,"journal":{"name":"Journal of Spacecraft and Rockets","volume":" ","pages":""},"PeriodicalIF":1.6,"publicationDate":"2023-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45491910","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Space-based optical monitoring systems have become promising options for space situational awareness with their advantages of observation range, duration, and quality. The dual-altitude band coverage evaluation of optical sensors is fundamental to designing and optimization of such systems. In this study, the dual-altitude band coverage evaluation of a spaceborne optical sensor with a cone field-of-view (FOV) constraint is addressed. Specifically, the target dual-altitude band region is discretized into crescent-shaped volume cells by introducing equidistant nodes along the radial and azimuth directions. When the size of each cell becomes sufficiently thin, the coverage of this cell can be approximated by the coverage of its centerline. Thus, the original dual-altitude band coverage problem is converted into a one-dimensional zenithal angular coverage problem. Then, considering geometric constraints on Earth’s occlusion and thermal background and the cone FOV constraints, we obtained the effective coverage of the azimuthal and zenithal angles of the target region by performing a comprehensive analysis of all 14 possible geometric cases. Alongside a pure coverage volume scoring method, a weighted coverage scoring method is introduced to take account of the nonuniform density distribution of space objects in altitude. Finally, the accuracy of the proposed method is validated by numerical examples.
{"title":"Dual-Altitude Band Coverage for Spaceborne Optical Sensor with Field-of-View Constraint","authors":"Yangyuxi Sun, Changxuan Wen, Zhengfan Zhu, Chen Zhang","doi":"10.2514/1.a35630","DOIUrl":"https://doi.org/10.2514/1.a35630","url":null,"abstract":"Space-based optical monitoring systems have become promising options for space situational awareness with their advantages of observation range, duration, and quality. The dual-altitude band coverage evaluation of optical sensors is fundamental to designing and optimization of such systems. In this study, the dual-altitude band coverage evaluation of a spaceborne optical sensor with a cone field-of-view (FOV) constraint is addressed. Specifically, the target dual-altitude band region is discretized into crescent-shaped volume cells by introducing equidistant nodes along the radial and azimuth directions. When the size of each cell becomes sufficiently thin, the coverage of this cell can be approximated by the coverage of its centerline. Thus, the original dual-altitude band coverage problem is converted into a one-dimensional zenithal angular coverage problem. Then, considering geometric constraints on Earth’s occlusion and thermal background and the cone FOV constraints, we obtained the effective coverage of the azimuthal and zenithal angles of the target region by performing a comprehensive analysis of all 14 possible geometric cases. Alongside a pure coverage volume scoring method, a weighted coverage scoring method is introduced to take account of the nonuniform density distribution of space objects in altitude. Finally, the accuracy of the proposed method is validated by numerical examples.","PeriodicalId":50048,"journal":{"name":"Journal of Spacecraft and Rockets","volume":" ","pages":""},"PeriodicalIF":1.6,"publicationDate":"2023-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46360472","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Debris strikes on operational spacecraft are becoming more common due to increasing numbers of space objects. Sample return missions indicate hundreds of minor strikes, but rigorous analysis is often only performed when a strike causes an anomaly in spacecraft performance. Developing techniques to identify and assess minor strikes that do not immediately cause anomalous behavior can help to validate models for debris populations and aid in the attribution of future anomalies. This study develops methods to detect subtle abrupt orbit perturbations indicative of minor debris strikes. An extended Kalman filter with dynamic model compensation is used to estimate a spacecraft’s orbit state based on simulated full-state (i.e., GPS) measurements. The filter is applied to the data forward and backward in time, and then a modified Fraser–Potter smoother is used to produce a fused state estimate. Various test statistics are developed and compared to identify abrupt unexpected changes in spacecraft velocity; techniques include McReynold’s filter-smoother consistency test and the Mahalanobis distance between forward and backward filter states. A trade study is performed to investigate the performance of test statistics as a function of filter parameters, and a Monte Carlo analysis illustrates the filter’s ability to detect and estimate strikes.
{"title":"Methods to Detect Impact-Induced Orbit Perturbations Using Spacecraft Navigation Data","authors":"A. Bennett, R. Carpenter, H. Schaub","doi":"10.2514/1.a35495","DOIUrl":"https://doi.org/10.2514/1.a35495","url":null,"abstract":"Debris strikes on operational spacecraft are becoming more common due to increasing numbers of space objects. Sample return missions indicate hundreds of minor strikes, but rigorous analysis is often only performed when a strike causes an anomaly in spacecraft performance. Developing techniques to identify and assess minor strikes that do not immediately cause anomalous behavior can help to validate models for debris populations and aid in the attribution of future anomalies. This study develops methods to detect subtle abrupt orbit perturbations indicative of minor debris strikes. An extended Kalman filter with dynamic model compensation is used to estimate a spacecraft’s orbit state based on simulated full-state (i.e., GPS) measurements. The filter is applied to the data forward and backward in time, and then a modified Fraser–Potter smoother is used to produce a fused state estimate. Various test statistics are developed and compared to identify abrupt unexpected changes in spacecraft velocity; techniques include McReynold’s filter-smoother consistency test and the Mahalanobis distance between forward and backward filter states. A trade study is performed to investigate the performance of test statistics as a function of filter parameters, and a Monte Carlo analysis illustrates the filter’s ability to detect and estimate strikes.","PeriodicalId":50048,"journal":{"name":"Journal of Spacecraft and Rockets","volume":" ","pages":""},"PeriodicalIF":1.6,"publicationDate":"2023-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47816978","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Survey of Tether System Technology for Space Debris Removal Missions","authors":"V. Aslanov, A. Ledkov","doi":"10.2514/1.a35646","DOIUrl":"https://doi.org/10.2514/1.a35646","url":null,"abstract":"","PeriodicalId":50048,"journal":{"name":"Journal of Spacecraft and Rockets","volume":" ","pages":""},"PeriodicalIF":1.6,"publicationDate":"2023-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48716711","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
To extend the usability of solar sails in the sun–Earth–moon system, we analyze the transfer trajectories from the 9:2 Earth–moon near-rectilinear halo orbit (NRHO) to halo orbits around the sun–Earth L1 and L2 points under the assumption of a future mission for a solar sail spacecraft equipped with a solar electric propulsion (SEP) system deployed from the Lunar Orbital Platform-Gateway. The dynamics are modeled using the bicircular restricted four-body problem, where the gravitational forces from the sun, Earth, and moon as well as solar radiation pressure (SRP) are considered. We propose a trajectory design method that utilizes both SRP and SEP. The method consists of initial guess generation and optimization steps. The initial guess generation comprises the forward propagation of the escape trajectory from the NRHO, the backward propagation of the stable manifold of the target halo orbits, and their apoapsis patching process. Optimization is conducted to minimize propellant consumption by effectively controlling SRP. We perform optimizations with various parameters, namely, the sail area-to-mass ratio ([Formula: see text]), specifications of SEP, target sun–Earth halo orbit, and departure [Formula: see text] direction. The results validate the proposed trajectory design method and verify that solar sail acceleration can reduce the necessary amount of propellant, which indicates that such missions can be realized by small CubeSats.
{"title":"Transfer from Lunar Gateway to Sun-Earth Halo Orbits Using Solar Sails","authors":"T. Chujo, Y. Takao, K. Oshima","doi":"10.2514/1.a35559","DOIUrl":"https://doi.org/10.2514/1.a35559","url":null,"abstract":"To extend the usability of solar sails in the sun–Earth–moon system, we analyze the transfer trajectories from the 9:2 Earth–moon near-rectilinear halo orbit (NRHO) to halo orbits around the sun–Earth L1 and L2 points under the assumption of a future mission for a solar sail spacecraft equipped with a solar electric propulsion (SEP) system deployed from the Lunar Orbital Platform-Gateway. The dynamics are modeled using the bicircular restricted four-body problem, where the gravitational forces from the sun, Earth, and moon as well as solar radiation pressure (SRP) are considered. We propose a trajectory design method that utilizes both SRP and SEP. The method consists of initial guess generation and optimization steps. The initial guess generation comprises the forward propagation of the escape trajectory from the NRHO, the backward propagation of the stable manifold of the target halo orbits, and their apoapsis patching process. Optimization is conducted to minimize propellant consumption by effectively controlling SRP. We perform optimizations with various parameters, namely, the sail area-to-mass ratio ([Formula: see text]), specifications of SEP, target sun–Earth halo orbit, and departure [Formula: see text] direction. The results validate the proposed trajectory design method and verify that solar sail acceleration can reduce the necessary amount of propellant, which indicates that such missions can be realized by small CubeSats.","PeriodicalId":50048,"journal":{"name":"Journal of Spacecraft and Rockets","volume":" ","pages":""},"PeriodicalIF":1.6,"publicationDate":"2023-05-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44897878","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
To reduce aerodynamic heat and drag, and thus improve the speed of hypersonic vehicles, opposing jet technology has become a research focus because of its excellent heat and drag reduction effect. In this paper, Navier–Stokes equations, the shear stress transport turbulent models, the Gupta chemical kinetics model, and the five-species air model are considered; and a numerical simulation program of hypersonic aerodynamic heat and drag with an opposing jet is developed and verified by existing experimental data. On this basis, the flight conditions of [Formula: see text], 14, and 15 at a 30 km flight altitude are simulated numerically; and the complex flowfield structure of the leading edge of a blunt body with or without the opposing jet is analyzed. It is found that the jet can push away the shock wave, playing a good role in reducing heat and drag. The influence of the pressure ratio, Mach number, and jet temperature on reducing heat and drag is investigated. The results indicate that, under the same conditions, increasing the pressure ratio, increasing the jet Mach number, and decreasing the inlet Mach number will be more helpful for reducing heat and drag; whereas increasing the jet temperature is not conducive to heat reduction and has little impact on aerodynamic drag.
{"title":"Simulations of Heat and Drag Reduction of Opposing Jet in Hypersonic Flow","authors":"Qian Wu, Haiming Huang, Yipu Zhao, J. Yao, Jiajing Bai, Jinglai Zheng","doi":"10.2514/1.a35696","DOIUrl":"https://doi.org/10.2514/1.a35696","url":null,"abstract":"To reduce aerodynamic heat and drag, and thus improve the speed of hypersonic vehicles, opposing jet technology has become a research focus because of its excellent heat and drag reduction effect. In this paper, Navier–Stokes equations, the shear stress transport turbulent models, the Gupta chemical kinetics model, and the five-species air model are considered; and a numerical simulation program of hypersonic aerodynamic heat and drag with an opposing jet is developed and verified by existing experimental data. On this basis, the flight conditions of [Formula: see text], 14, and 15 at a 30 km flight altitude are simulated numerically; and the complex flowfield structure of the leading edge of a blunt body with or without the opposing jet is analyzed. It is found that the jet can push away the shock wave, playing a good role in reducing heat and drag. The influence of the pressure ratio, Mach number, and jet temperature on reducing heat and drag is investigated. The results indicate that, under the same conditions, increasing the pressure ratio, increasing the jet Mach number, and decreasing the inlet Mach number will be more helpful for reducing heat and drag; whereas increasing the jet temperature is not conducive to heat reduction and has little impact on aerodynamic drag.","PeriodicalId":50048,"journal":{"name":"Journal of Spacecraft and Rockets","volume":" ","pages":""},"PeriodicalIF":1.6,"publicationDate":"2023-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43380149","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Recently, NASA has pushed for returning humans to the moon sustainably with in situ resource utilization as the central focus. The moon has an abundance of water that is proposed to be electrolyzed into hydrogen and oxygen to be used as propellant. Other volatiles such as ammonia, carbon dioxide, and methane are also present. A mission architecture for a lunar ascent/descent vehicle (LADV) from the Polytechnic University of Turin and nuclear thermal propulsion (NTP) engine models from the University of Alabama in Huntsville were used to compare in-situ-derived propellants for a LADV. This study considered a LADV originating from the lunar surface, delivering a payload in the lunar distant retrograde orbit, and returning to the lunar surface for retanking. This research analyzed the impacts on this mission of using hydrogen NTP, water/ammonia NTP, liquid-oxygen augmented nuclear thermal rocket, and Aeon 1 methane–oxygen engines using the selected architecture and tools. The results were compared to the reference hydrogen–oxygen RL10 engine. The propulsion system comparison analysis showed that combustion engines will offer better overall performance than NTP-based engines due to a 50% decrease in propellant volume, a 20% decrease in dry mass, and a lower propellant mass than the water and ammonia NTP systems. Both the hydrogen–oxygen and methane–oxygen propulsion systems will have similar propellant masses when compared to other systems. This is due to the order of magnitude higher mass of the NTP engines, with the highest mass contribution coming from the reactor. However, both water and ammonia alternative propellant NTP engines can still be viable candidates for the usage of these minimally processed propellants to satisfy this mission.
{"title":"In Situ Propellant Alternatives for a Lunar Ascent/Descent Vehicle","authors":"Daria Nikitaeva, L. Dale Thomas","doi":"10.2514/1.a35507","DOIUrl":"https://doi.org/10.2514/1.a35507","url":null,"abstract":"Recently, NASA has pushed for returning humans to the moon sustainably with in situ resource utilization as the central focus. The moon has an abundance of water that is proposed to be electrolyzed into hydrogen and oxygen to be used as propellant. Other volatiles such as ammonia, carbon dioxide, and methane are also present. A mission architecture for a lunar ascent/descent vehicle (LADV) from the Polytechnic University of Turin and nuclear thermal propulsion (NTP) engine models from the University of Alabama in Huntsville were used to compare in-situ-derived propellants for a LADV. This study considered a LADV originating from the lunar surface, delivering a payload in the lunar distant retrograde orbit, and returning to the lunar surface for retanking. This research analyzed the impacts on this mission of using hydrogen NTP, water/ammonia NTP, liquid-oxygen augmented nuclear thermal rocket, and Aeon 1 methane–oxygen engines using the selected architecture and tools. The results were compared to the reference hydrogen–oxygen RL10 engine. The propulsion system comparison analysis showed that combustion engines will offer better overall performance than NTP-based engines due to a 50% decrease in propellant volume, a 20% decrease in dry mass, and a lower propellant mass than the water and ammonia NTP systems. Both the hydrogen–oxygen and methane–oxygen propulsion systems will have similar propellant masses when compared to other systems. This is due to the order of magnitude higher mass of the NTP engines, with the highest mass contribution coming from the reactor. However, both water and ammonia alternative propellant NTP engines can still be viable candidates for the usage of these minimally processed propellants to satisfy this mission.","PeriodicalId":50048,"journal":{"name":"Journal of Spacecraft and Rockets","volume":" ","pages":""},"PeriodicalIF":1.6,"publicationDate":"2023-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42027615","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The initiation and growth of turbulent spots in transitional hypersonic boundary layers can influence the transition length and the distribution of heat transfer and skin friction through the transitional region. There is debate in the literature about whether spots initiate in a small band at the start of transition or throughout the transitional region. This paper presents a new design of arrays of thin-film heat transfer specifically designed to detect whether spots initiate in a small band. The gauges were arranged in two spanwise rows at different streamwise locations and were tested on a 7° blunt cone in the T4 Stalker Tube. It is shown that such instrumentation is capable of identifying that some spots initiate between the rows when other spots have already formed upstream of the first row. This demonstrates that the breakdown of laminar boundary layers is not concentrated in a region of small streamwise extent in the current hypersonic flows.
{"title":"Heat-Transfer Gauge Arrays for Identifying Spot Initiation in Hypersonic Transitional Boundary Layers","authors":"D. Mee, S. Raghunath, M. McGilvray","doi":"10.2514/1.a35662","DOIUrl":"https://doi.org/10.2514/1.a35662","url":null,"abstract":"The initiation and growth of turbulent spots in transitional hypersonic boundary layers can influence the transition length and the distribution of heat transfer and skin friction through the transitional region. There is debate in the literature about whether spots initiate in a small band at the start of transition or throughout the transitional region. This paper presents a new design of arrays of thin-film heat transfer specifically designed to detect whether spots initiate in a small band. The gauges were arranged in two spanwise rows at different streamwise locations and were tested on a 7° blunt cone in the T4 Stalker Tube. It is shown that such instrumentation is capable of identifying that some spots initiate between the rows when other spots have already formed upstream of the first row. This demonstrates that the breakdown of laminar boundary layers is not concentrated in a region of small streamwise extent in the current hypersonic flows.","PeriodicalId":50048,"journal":{"name":"Journal of Spacecraft and Rockets","volume":" ","pages":""},"PeriodicalIF":1.6,"publicationDate":"2023-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46832109","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The results of a Pluto landing analysis study for a fast, hyperbolic approach trajectory are presented by assuming the use of a novel entry, descent, and landing system called an enveloping aerodynamic decelerator. A landing site uncertainty analysis is performed for an 11 September 2040 arrival by means of a Monte Carlo simulation to map key trajectory, aerodynamic, system, and atmosphere uncertainties to landing zone errors. The estimated 3 [Formula: see text] landing error ellipse is about 430 by 190 km. The band of feasible landing sites is between 35°N and 10°S latitude on the surface of Pluto.
{"title":"Mission Analysis for Landing on Pluto from a Fast, Hyperbolic Trajectory","authors":"Mark Warnecke, Kerry T. Nock, Kim M. Aaron","doi":"10.2514/1.a35498","DOIUrl":"https://doi.org/10.2514/1.a35498","url":null,"abstract":"The results of a Pluto landing analysis study for a fast, hyperbolic approach trajectory are presented by assuming the use of a novel entry, descent, and landing system called an enveloping aerodynamic decelerator. A landing site uncertainty analysis is performed for an 11 September 2040 arrival by means of a Monte Carlo simulation to map key trajectory, aerodynamic, system, and atmosphere uncertainties to landing zone errors. The estimated 3 [Formula: see text] landing error ellipse is about 430 by 190 km. The band of feasible landing sites is between 35°N and 10°S latitude on the surface of Pluto.","PeriodicalId":50048,"journal":{"name":"Journal of Spacecraft and Rockets","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135801485","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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