Pub Date : 2026-02-03DOI: 10.1016/j.actaastro.2026.01.072
Mingxuan Song , He Liao , Jinjin Xie
The successful launch of the Xihe satellite and the accomplishment of its on-orbit experimental mission demonstrate that the non-contact spacecraft technology has emerged as a pivotal developmental trend in ultra-high-precision spacecraft control. To further enhance the control performance and reduce the launch mass of the spacecraft, this paper proposes a three-stage comprehensive structure optimization focusing on the mass and magnetic uniformity within the air-gap of the Linear Lorentz Actuator (LLA), which is the key actuator of non-contact spacecraft. Firstly, configuration optimization is performed via finite element simulation (FEM) to identify the optimal configuration among three candidate LLA configurations suitable for non-contact spacecraft. Subsequently, dimensional parameters of the optimal configuration are then refined to maximize magnetic uniformity. Furthermore, a composited-objective topology optimization based on density interpolation function is proposed to achieve global optimality. This yields an optimized LLA structure achieving a magnetic uniformity of 0.00057 and a 50% mass reduction in the magnetic conduction ring. Furthermore, a physical LLA prototype is fabricated based on the optimized design in this paper. Ground tests confirm that deviations between measured and theoretical magnetic field data in the air-gap did not exceed 4%, validating the effectiveness of the proposed optimization strategy.
{"title":"Topology optimization and experimental validation of Linear Lorentz Actuator for non-contact spacecraft","authors":"Mingxuan Song , He Liao , Jinjin Xie","doi":"10.1016/j.actaastro.2026.01.072","DOIUrl":"10.1016/j.actaastro.2026.01.072","url":null,"abstract":"<div><div>The successful launch of the Xihe satellite and the accomplishment of its on-orbit experimental mission demonstrate that the non-contact spacecraft technology has emerged as a pivotal developmental trend in ultra-high-precision spacecraft control. To further enhance the control performance and reduce the launch mass of the spacecraft, this paper proposes a three-stage comprehensive structure optimization focusing on the mass and magnetic uniformity within the air-gap of the Linear Lorentz Actuator (LLA), which is the key actuator of non-contact spacecraft. Firstly, configuration optimization is performed via finite element simulation (FEM) to identify the optimal configuration among three candidate LLA configurations suitable for non-contact spacecraft. Subsequently, dimensional parameters of the optimal configuration are then refined to maximize magnetic uniformity. Furthermore, a composited-objective topology optimization based on density interpolation function is proposed to achieve global optimality. This yields an optimized LLA structure achieving a magnetic uniformity of 0.00057 and a 50% mass reduction in the magnetic conduction ring. Furthermore, a physical LLA prototype is fabricated based on the optimized design in this paper. Ground tests confirm that deviations between measured and theoretical magnetic field data in the air-gap did not exceed 4%, validating the effectiveness of the proposed optimization strategy.</div></div>","PeriodicalId":44971,"journal":{"name":"Acta Astronautica","volume":"244 ","pages":"Pages 20-37"},"PeriodicalIF":3.4,"publicationDate":"2026-02-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146109806","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-01DOI: 10.1016/j.actaastro.2026.01.062
Yiming Ke , Hao Zhu , Shuting Wang , Yuanjun Zhang , Hui Tian , Guobiao Cai
Hybrid rocket motors (HRMs) are gaining widespread application due to their advantages, including high safety, ease of thrust control, and multiple restart capability. However, nozzle ablation remains a critical technical bottleneck limiting their development. This study presents a numerical investigation of nozzle mechanical erosion in HRMs under overload conditions. The mechanical erosion of nozzles for four propellant grain configurations tube, star, single-channel wheel, and multi-channel wheel were computationally analyzed. The results reveal a strong correlation between nozzle mechanical erosion and the propellant-grain type, as well as a significant dependence on motor overload conditions. Under certain operating scenarios, the peak erosion rate increases by more than threefold compared with that under non-overload conditions. As overload increases, the peak erosion rate initially rises and then stabilizes. For the motor configurations studied, when the overload exceeds 10 g, the maximum erosion rate remains nearly constant. Furthermore, the magnitude of the overload effect on erosion and particle distribution varies with grain type. Overall, the influence of overload is more pronounced for single-channel grains than for multi-channel grain. Within the single-channel grains, the degree of influence decreases in the following order: cylindrical, star, and wheel grain. It is worth noting that this study focuses on the mechanical erosion of HRMs nozzle under overload conditions and does not consider the effect of overload on the combustion state.
{"title":"Numerical simulation and analysis of nozzle mechanical erosion in hybrid rocket motors under overload conditions","authors":"Yiming Ke , Hao Zhu , Shuting Wang , Yuanjun Zhang , Hui Tian , Guobiao Cai","doi":"10.1016/j.actaastro.2026.01.062","DOIUrl":"10.1016/j.actaastro.2026.01.062","url":null,"abstract":"<div><div>Hybrid rocket motors (HRMs) are gaining widespread application due to their advantages, including high safety, ease of thrust control, and multiple restart capability. However, nozzle ablation remains a critical technical bottleneck limiting their development. This study presents a numerical investigation of nozzle mechanical erosion in HRMs under overload conditions. The mechanical erosion of nozzles for four propellant grain configurations tube, star, single-channel wheel, and multi-channel wheel were computationally analyzed. The results reveal a strong correlation between nozzle mechanical erosion and the propellant-grain type, as well as a significant dependence on motor overload conditions. Under certain operating scenarios, the peak erosion rate increases by more than threefold compared with that under non-overload conditions. As overload increases, the peak erosion rate initially rises and then stabilizes. For the motor configurations studied, when the overload exceeds 10 g, the maximum erosion rate remains nearly constant. Furthermore, the magnitude of the overload effect on erosion and particle distribution varies with grain type. Overall, the influence of overload is more pronounced for single-channel grains than for multi-channel grain. Within the single-channel grains, the degree of influence decreases in the following order: cylindrical, star, and wheel grain. It is worth noting that this study focuses on the mechanical erosion of HRMs nozzle under overload conditions and does not consider the effect of overload on the combustion state.</div></div>","PeriodicalId":44971,"journal":{"name":"Acta Astronautica","volume":"244 ","pages":"Pages 122-140"},"PeriodicalIF":3.4,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146174807","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-31DOI: 10.1016/j.actaastro.2026.01.064
Matteo Carattoli, Adriano Ceccotti, David Paolo Madonna, Mauro Pontani, Marco Sabatini, Paolo Gasbarri
{"title":"A GEOMETRIC APPROACH TO NEAR-OPTIMAL FEEDBACK ATTITUDE SLEWING WITH DIRECTIONAL AND ACTUATION CONSTRAINTS","authors":"Matteo Carattoli, Adriano Ceccotti, David Paolo Madonna, Mauro Pontani, Marco Sabatini, Paolo Gasbarri","doi":"10.1016/j.actaastro.2026.01.064","DOIUrl":"https://doi.org/10.1016/j.actaastro.2026.01.064","url":null,"abstract":"","PeriodicalId":44971,"journal":{"name":"Acta Astronautica","volume":"62 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146089653","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper presents an efficient method for designing the rhombus-shaped facets of a parabolic reflector. An approximate solution is derived to calculate the RMS error induced by mesh deformation. Finite Element Analysis (FEA) is conducted by modeling a single rhombus facet to validate the approximate solution. The FEA results show good agreement with the approximate solution in terms of maximum facet deformation. Furthermore, the RMS error of an actual 1 m-scale reflector was measured, revealing a difference of only 4.5 % between the measured and estimated values. Finally, the facet length and angle are designed to satisfy the surface accuracy requirements for different frequency bands using the proposed method.
{"title":"Rhombus facet design of fan-fold deployable reflector","authors":"Tadashi Masuoka , Satoru Ozawa , Takahiro Kuhara , Yuji Yamagata , Nobuaki Minami , Kazuyuki Nakamura","doi":"10.1016/j.actaastro.2026.01.069","DOIUrl":"10.1016/j.actaastro.2026.01.069","url":null,"abstract":"<div><div>This paper presents an efficient method for designing the rhombus-shaped facets of a parabolic reflector. An approximate solution is derived to calculate the RMS error induced by mesh deformation. Finite Element Analysis (FEA) is conducted by modeling a single rhombus facet to validate the approximate solution. The FEA results show good agreement with the approximate solution in terms of maximum facet deformation. Furthermore, the RMS error of an actual 1 m-scale reflector was measured, revealing a difference of only 4.5 % between the measured and estimated values. Finally, the facet length and angle are designed to satisfy the surface accuracy requirements for different frequency bands using the proposed method.</div></div>","PeriodicalId":44971,"journal":{"name":"Acta Astronautica","volume":"243 ","pages":"Pages 305-314"},"PeriodicalIF":3.4,"publicationDate":"2026-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146089662","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-30DOI: 10.1016/j.actaastro.2026.01.057
Hugh Chen, Samuel T. Hart, Álvaro Romero-Calvo
CubeSat cold-gas propulsion increasingly relies on two-phase, self-pressurizing propellants stored in conformal tanks. However, state-of-the-art propellant management strategies for these systems result in significant inefficiencies in volume or power management, limiting the total V budget and the mission lifetime. These challenges highlight the need for a more compact propellant management approach. The VAporization for PrOpellant Repositioning (VAPOR) experiment investigates the feasibility of repositioning an ullage gas bubble of R-236fa using thermally-induced phase change in various propellant management devices (PMDs). These devices utilize a heat source to vaporize propellant near the outlet, inducing pressure-driven bubble condensation in colder regions of the tank. Capillary structures are integrated to retain vapor near the heater and promote bubble coalescence, facilitating extraction and routing to thrusters. Building upon iterative designs across two parabolic flight campaigns, six thermocapillary PMDs are evaluated, culminating in three thermal start basket architectures. Patch heater PMDs initiate ullage generation in under 1 s and sustain the highest boiling rates, whereas sponge-based start baskets exhibit an average initiation time of s with more modest ullage generation. All capillary structures successfully capture the generated vapor. Collectively, results establish thermocapillary PMDs as a compact alternative to conventional two-tank systems for CubeSat cold-gas propulsion.
{"title":"Thermal propellant management devices for CubeSat cold gas propulsion","authors":"Hugh Chen, Samuel T. Hart, Álvaro Romero-Calvo","doi":"10.1016/j.actaastro.2026.01.057","DOIUrl":"10.1016/j.actaastro.2026.01.057","url":null,"abstract":"<div><div>CubeSat cold-gas propulsion increasingly relies on two-phase, self-pressurizing propellants stored in conformal tanks. However, state-of-the-art propellant management strategies for these systems result in significant inefficiencies in volume or power management, limiting the total <span><math><mi>Δ</mi></math></span>V budget and the mission lifetime. These challenges highlight the need for a more compact propellant management approach. The VAporization for PrOpellant Repositioning (VAPOR) experiment investigates the feasibility of repositioning an ullage gas bubble of R-236fa using thermally-induced phase change in various propellant management devices (PMDs). These devices utilize a heat source to vaporize propellant near the outlet, inducing pressure-driven bubble condensation in colder regions of the tank. Capillary structures are integrated to retain vapor near the heater and promote bubble coalescence, facilitating extraction and routing to thrusters. Building upon iterative designs across two parabolic flight campaigns, six thermocapillary PMDs are evaluated, culminating in three thermal start basket architectures. Patch heater PMDs initiate ullage generation in under 1 s and sustain the highest boiling rates, whereas sponge-based start baskets exhibit an average initiation time of <span><math><mrow><mn>6</mn><mo>.</mo><mn>9</mn><mo>±</mo><mn>1</mn><mo>.</mo><mn>3</mn></mrow></math></span> s with more modest ullage generation. All capillary structures successfully capture the generated vapor. Collectively, results establish thermocapillary PMDs as a compact alternative to conventional two-tank systems for CubeSat cold-gas propulsion.</div></div>","PeriodicalId":44971,"journal":{"name":"Acta Astronautica","volume":"243 ","pages":"Pages 291-304"},"PeriodicalIF":3.4,"publicationDate":"2026-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146089678","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-30DOI: 10.1016/j.actaastro.2025.12.035
Darren McKnight , Erin Dale , Joe Cassady , Andy Ratcliffe , Satomi Kawamoto , Alessandro Rossi , Dmitriy Grishko
The growth of orbital debris in number and mass in low Earth orbit (LEO) has been a subject of analysis for decades. The global community established the 25-yr debris mitigation rule 20–25 years ago and at that time many started assembling long lists of number, mass, and nationality of abandoned hardware. In 2020, a team of 19 experts from 13 countries assembled to create a definitive list of 50 objects that would most likely directly drive debris growth in LEO. This list was provided as a “priority list” for active debris removal (ADR) operations. Since 2020, continued accumulation of derelict objects coupled with the rapid increase of operational satellites has occurred. This combination has motivated the authors to update the 2020 Top 50 List. The new list considers (a) aggregate collision risk (i.e., probability of collision x consequence) since January 1, 2022, (b) orbital persistence of fragments (if a collision occurs), (c) proximity to existing altitudes where aggregate statistical risk of the population is the largest (meaning clusters centered around 775 km, 840 km, 1000 km, and 1400 km), (d) mass of object, and (e) coupling between removing objects on the list.
The paper is enabled through the application of new analytic tools created by LeoLabs based on empirical observations of close approaches in LEO merged with open-source tagging of objects in the public catalogue with known masses. It is important to note the coauthors abide by the philosophy that many viable models can be used to derive the top 50 objects to be removed from LEO. The benefit of the current approach applies a team approach to adjusting filters to a single model; however, the implication is not that this model is the only way to select the top 50 objects. In essence, one of the most critical aspects of any attempt to identify the objects whose retrieval will decrease the debris-generating potential in LEO is to identify key features of objects such as mass, probability of collision (especially with other massive objects), altitude, etc. A comparison of the 2020 Top 50 List and the new 2025 Top 50 List is provided to illuminate key lessons for debris hazard evolution and to motivate operationalization of ADR.
{"title":"Top 50 List for 2025","authors":"Darren McKnight , Erin Dale , Joe Cassady , Andy Ratcliffe , Satomi Kawamoto , Alessandro Rossi , Dmitriy Grishko","doi":"10.1016/j.actaastro.2025.12.035","DOIUrl":"10.1016/j.actaastro.2025.12.035","url":null,"abstract":"<div><div>The growth of orbital debris in number and mass in low Earth orbit (LEO) has been a subject of analysis for decades. The global community established the 25-yr debris mitigation rule 20–25 years ago and at that time many started assembling long lists of number, mass, and nationality of abandoned hardware. In 2020, a team of 19 experts from 13 countries assembled to create a definitive list of 50 objects that would most likely directly drive debris growth in LEO. This list was provided as a “priority list” for active debris removal (ADR) operations. Since 2020, continued accumulation of derelict objects coupled with the rapid increase of operational satellites has occurred. This combination has motivated the authors to update the 2020 Top 50 List. The new list considers (a) aggregate collision risk (i.e., probability of collision x consequence) since January 1, 2022, (b) orbital persistence of fragments (if a collision occurs), (c) proximity to existing altitudes where aggregate statistical risk of the population is the largest (meaning clusters centered around 775 km, 840 km, 1000 km, and 1400 km), (d) mass of object, and (e) coupling between removing objects on the list.</div><div>The paper is enabled through the application of new analytic tools created by LeoLabs based on empirical observations of close approaches in LEO merged with open-source tagging of objects in the public catalogue with known masses. It is important to note the coauthors abide by the philosophy that many viable models can be used to derive the top 50 objects to be removed from LEO. The benefit of the current approach applies a team approach to adjusting filters to a single model; however, the implication is not that this model is the only way to select the top 50 objects. In essence, one of the most critical aspects of any attempt to identify the objects whose retrieval will decrease the debris-generating potential in LEO is to identify key features of objects such as mass, probability of collision (especially with other massive objects), altitude, etc. A comparison of the 2020 Top 50 List and the new 2025 Top 50 List is provided to illuminate key lessons for debris hazard evolution and to motivate operationalization of ADR.</div></div>","PeriodicalId":44971,"journal":{"name":"Acta Astronautica","volume":"243 ","pages":"Pages 346-357"},"PeriodicalIF":3.4,"publicationDate":"2026-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146089657","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-29DOI: 10.1016/j.actaastro.2026.01.065
Lei Chen , Zhangfan Xu , Song Pan , Huafeng Li
Control moment gyroscopes serving as high-power attitude actuators for large spacecraft require sustained lubrication performance of their high-speed bearings to ensure long-term operation. A critical challenge arises from the temperature-dependent release rate of lubricant stored in oil reservoirs, combined with structural constraints that impede direct temperature measurement at key bearing nodes. To address this issue, this study develops a thermal network modeling methodology for control moment gyroscopes that enables comprehensive and precise temperature estimation across all critical components. Experimental validation via thermal equilibrium tests demonstrates strong agreement between the measured and simulated temperatures (with an error coefficient of less than 12 %). The verified thermal network model provides an effective theoretical framework for the on-orbit thermal management and failure early warning of control moment gyroscopes, thereby enhancing operational reliability and extending lifespan. This methodology offers significant value for precision thermal control in advanced aerospace instrumentation systems.
{"title":"Thermal analysis of control moment gyroscopes based on the thermal network method","authors":"Lei Chen , Zhangfan Xu , Song Pan , Huafeng Li","doi":"10.1016/j.actaastro.2026.01.065","DOIUrl":"10.1016/j.actaastro.2026.01.065","url":null,"abstract":"<div><div>Control moment gyroscopes serving as high-power attitude actuators for large spacecraft require sustained lubrication performance of their high-speed bearings to ensure long-term operation. A critical challenge arises from the temperature-dependent release rate of lubricant stored in oil reservoirs, combined with structural constraints that impede direct temperature measurement at key bearing nodes. To address this issue, this study develops a thermal network modeling methodology for control moment gyroscopes that enables comprehensive and precise temperature estimation across all critical components. Experimental validation via thermal equilibrium tests demonstrates strong agreement between the measured and simulated temperatures (with an error coefficient of less than 12 %). The verified thermal network model provides an effective theoretical framework for the on-orbit thermal management and failure early warning of control moment gyroscopes, thereby enhancing operational reliability and extending lifespan. This methodology offers significant value for precision thermal control in advanced aerospace instrumentation systems.</div></div>","PeriodicalId":44971,"journal":{"name":"Acta Astronautica","volume":"243 ","pages":"Pages 162-171"},"PeriodicalIF":3.4,"publicationDate":"2026-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146072608","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-29DOI: 10.1016/j.actaastro.2026.01.044
Xi Wang , Gang He , Yan-ping Tian , Yu-xin Zhao , Qian-cheng Wang , Yi-long Zhao
The boundary layer on the surface of supersonic and hypersonic vehicles exerts a significant influence on inlet performance. The diverter is widely utilized to expel the boundary layer directly, thereby enhancing the inlet’s efficiency. This paper establishes a simplified research model of the diverter and investigates the characteristics and mechanisms of the complex three-dimensional flow both within and external to the diverter using oil-flow visualization, pressure measurement, and Nanoparticle-based Planar Laser Scattering (NPLS) techniques. The results indicate that the flow within the diverter exhibits three states: choked, critical, and unchoked. In the choked and critical states, the separation line on the flat plate forms a ”bow” shape, and secondary separation phenomena are observed. In contrast, the separation zone in the unchoked state exhibits quasi-conical flow characteristics. Additionally, as the diverter height increases, the separation angle of the separation line increases and approaches that of swept shock wave/boundary layer interactions under the same deflection conditions. Furthermore, with an increase in the diverter height, the flow state within the diverter transitions from the choked state to the critical state, and ultimately to the unchoked state. Regarding the diverter as two symmetric, back-to-back side-compression inlets, the inviscid effects of the diverter height increase are examined through the inlet starting theory. The results shows that the inviscid factor plays a limited role in the diverter’s flow-passing capability. In future, the viscous effects of the diverter height increase would be examined with high-precision simulation results.
{"title":"Study on the mechanism of supersonic diverter flow","authors":"Xi Wang , Gang He , Yan-ping Tian , Yu-xin Zhao , Qian-cheng Wang , Yi-long Zhao","doi":"10.1016/j.actaastro.2026.01.044","DOIUrl":"10.1016/j.actaastro.2026.01.044","url":null,"abstract":"<div><div>The boundary layer on the surface of supersonic and hypersonic vehicles exerts a significant influence on inlet performance. The diverter is widely utilized to expel the boundary layer directly, thereby enhancing the inlet’s efficiency. This paper establishes a simplified research model of the diverter and investigates the characteristics and mechanisms of the complex three-dimensional flow both within and external to the diverter using oil-flow visualization, pressure measurement, and Nanoparticle-based Planar Laser Scattering (NPLS) techniques. The results indicate that the flow within the diverter exhibits three states: choked, critical, and unchoked. In the choked and critical states, the separation line on the flat plate forms a ”bow” shape, and secondary separation phenomena are observed. In contrast, the separation zone in the unchoked state exhibits quasi-conical flow characteristics. Additionally, as the diverter height increases, the separation angle of the separation line increases and approaches that of swept shock wave/boundary layer interactions under the same deflection conditions. Furthermore, with an increase in the diverter height, the flow state within the diverter transitions from the choked state to the critical state, and ultimately to the unchoked state. Regarding the diverter as two symmetric, back-to-back side-compression inlets, the inviscid effects of the diverter height increase are examined through the inlet starting theory. The results shows that the inviscid factor plays a limited role in the diverter’s flow-passing capability. In future, the viscous effects of the diverter height increase would be examined with high-precision simulation results.</div></div>","PeriodicalId":44971,"journal":{"name":"Acta Astronautica","volume":"243 ","pages":"Pages 315-325"},"PeriodicalIF":3.4,"publicationDate":"2026-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146072609","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-29DOI: 10.1016/j.actaastro.2026.01.063
Pietro Canal , Alejandro Cano , Santiago Martínez , Adrián Hernández , Pierluigi Di Lizia , Diego Escobar
The availability of realistic covariance information for the orbit of every Resident Space Object (RSO) contained in a catalogue is crucial for Space Situational Awareness activities, e.g., collision avoidance services. The most comprehensive of these catalogues is the Special Perturbations Catalogue (SPCAT), maintained by the U.S. 18th Space Defense Squadron. The SPCAT is the high-precision ephemeris version of the Two Line Elements RSOs catalogue, publicly available on databases such as Space Track and Celestrak. However, covariance information is not provided with the mean state of the SPCAT ephemerides. So-called observed covariance values can be obtained via a comparison procedure between consecutive orbit information updates referring to the same SPCAT RSO. This paper proposes new methodologies for calculating covariance values for catalogues deprived of such information, including the application and adaptation of existing data-fusion methods from literature. The main final goal is to compute covariance matrices that are more realistic and reliable than those obtained with the currently available methods. Another key objective is the integration of the new methodology in an operational environment. Computational efficiency is then a relevant factor, and the baseline method to be developed is selected and improved taking into account such efficiency criterion. A new routine that considers the Orbit Determination epoch of each RSO ephemeris arc to coherently combine covariances based on their propagation time is developed and implemented. Two fusion methods are deployed, Covariance Intersection and Covariance Union, and the realism of the results is tested with a well-established metric, the Mahalanobis distance and its fitting of the Chi-square distribution according to appropriate Empirical Distribution Function tests such as Cramer-von Mises. The realism of the combined covariances is validated against precise ephemeris of LEO Sentinel satellites. While Covariance Intersection is proved inadequate as a stand-alone fusion method due to the characteristics of the SPCAT observed covariances, Covariance Union provides covariance values that are consistently more realistic than the ones obtained with the baseline method.
{"title":"Covariance estimation and fusion for ephemeris-only catalogues applied to the Special Perturbations Catalogue","authors":"Pietro Canal , Alejandro Cano , Santiago Martínez , Adrián Hernández , Pierluigi Di Lizia , Diego Escobar","doi":"10.1016/j.actaastro.2026.01.063","DOIUrl":"10.1016/j.actaastro.2026.01.063","url":null,"abstract":"<div><div>The availability of realistic covariance information for the orbit of every Resident Space Object (RSO) contained in a catalogue is crucial for Space Situational Awareness activities, e.g., collision avoidance services. The most comprehensive of these catalogues is the Special Perturbations Catalogue (SPCAT), maintained by the U.S. 18th Space Defense Squadron. The SPCAT is the high-precision ephemeris version of the Two Line Elements RSOs catalogue, publicly available on databases such as Space Track and Celestrak. However, covariance information is not provided with the mean state of the SPCAT ephemerides. So-called observed covariance values can be obtained via a comparison procedure between consecutive orbit information updates referring to the same SPCAT RSO. This paper proposes new methodologies for calculating covariance values for catalogues deprived of such information, including the application and adaptation of existing data-fusion methods from literature. The main final goal is to compute covariance matrices that are more realistic and reliable than those obtained with the currently available methods. Another key objective is the integration of the new methodology in an operational environment. Computational efficiency is then a relevant factor, and the baseline method to be developed is selected and improved taking into account such efficiency criterion. A new routine that considers the Orbit Determination epoch of each RSO ephemeris arc to coherently combine covariances based on their propagation time is developed and implemented. Two fusion methods are deployed, Covariance Intersection and Covariance Union, and the realism of the results is tested with a well-established metric, the Mahalanobis distance and its fitting of the Chi-square distribution according to appropriate Empirical Distribution Function tests such as Cramer-von Mises. The realism of the combined covariances is validated against precise ephemeris of LEO Sentinel satellites. While Covariance Intersection is proved inadequate as a stand-alone fusion method due to the characteristics of the SPCAT observed covariances, Covariance Union provides covariance values that are consistently more realistic than the ones obtained with the baseline method.</div></div>","PeriodicalId":44971,"journal":{"name":"Acta Astronautica","volume":"243 ","pages":"Pages 207-219"},"PeriodicalIF":3.4,"publicationDate":"2026-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146072606","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-28DOI: 10.1016/j.actaastro.2026.01.066
Lucia Lambertini , Maria Gabriella Santonicola , Susanna Laurenzi
Protection of astronauts from intense space radiation during long-term missions to the Moon or Mars remains a critical challenge. With space agencies planning permanent lunar bases as gateways for deep-space exploration, enhancing radiation shielding in spacesuits during extravehicular activities (EVAs) is essential. This study explores the feasibility of integrating poly(vinyl alcohol) (PVA)-based gels as an intermediate shielding layer between the pressure bladder garment (PBG) and the liquid cooling and ventilation garment (LCVG), without altering suit geometry or increasing layer thickness. Due to their high water content, PVA-based gels combine flexibility, softness, and ductility with effective radiation attenuation. Experimental analyses compared the physical and mechanical properties of PVA gels to nylon, the primary material of PBG and LCVG. The gels exhibited similar density and thermal conductivity but demonstrated superior deformability, achieving elongations up to ∼65 % despite a lower Young's modulus. Numerical simulations performed with the OLTARIS confirmed the shielding potential of the proposed configuration. While protection against Galactic Cosmic Rays (GCR) remained limited due to their high penetration depth, the inclusion of PVA-based gel layers significantly reduced proton doses from Solar Particle Events (SPE), indicating their potential as an effective, lightweight enhancement to current spacesuit designs.
{"title":"Flexible PVA/BA gel for passive radiation shielding in spacesuit applications beyond LEO","authors":"Lucia Lambertini , Maria Gabriella Santonicola , Susanna Laurenzi","doi":"10.1016/j.actaastro.2026.01.066","DOIUrl":"10.1016/j.actaastro.2026.01.066","url":null,"abstract":"<div><div>Protection of astronauts from intense space radiation during long-term missions to the Moon or Mars remains a critical challenge. With space agencies planning permanent lunar bases as gateways for deep-space exploration, enhancing radiation shielding in spacesuits during extravehicular activities (EVAs) is essential. This study explores the feasibility of integrating poly(vinyl alcohol) (PVA)-based gels as an intermediate shielding layer between the pressure bladder garment (PBG) and the liquid cooling and ventilation garment (LCVG), without altering suit geometry or increasing layer thickness. Due to their high water content, PVA-based gels combine flexibility, softness, and ductility with effective radiation attenuation. Experimental analyses compared the physical and mechanical properties of PVA gels to nylon, the primary material of PBG and LCVG. The gels exhibited similar density and thermal conductivity but demonstrated superior deformability, achieving elongations up to ∼65 % despite a lower Young's modulus. Numerical simulations performed with the OLTARIS confirmed the shielding potential of the proposed configuration. While protection against Galactic Cosmic Rays (GCR) remained limited due to their high penetration depth, the inclusion of PVA-based gel layers significantly reduced proton doses from Solar Particle Events (SPE), indicating their potential as an effective, lightweight enhancement to current spacesuit designs.</div></div>","PeriodicalId":44971,"journal":{"name":"Acta Astronautica","volume":"243 ","pages":"Pages 149-161"},"PeriodicalIF":3.4,"publicationDate":"2026-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146072618","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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