This paper presents the catalytic effects of Cu-Co~* catalyst on the decomposition of AN and AN/KDN based oxidizer and propellant samples. Ozawa-Flynn-Wall(OFW) iso-conversional method was used for the kinetic studies...This paper presents the catalytic effects of Cu-Co~* catalyst on the decomposition of AN and AN/KDN based oxidizer and propellant samples. Ozawa-Flynn-Wall(OFW) iso-conversional method was used for the kinetic studies and to compute the activation energy(Ea) values for various decomposition steps of the prepared oxidizer and propellant samples in the temperature range of 50 e500C. TG-DTG experiments were carried out for both oxidizer and propellant samples at the heating rates of 3, 5, and 10C/min. AN/KDN based oxidizer samples were prepared by an evaporative co-crystallization method. Citric acid sol-gel method was used for the synthesis of Cu-Co~* catalyst. The propellant sample contains HTPB as the fuel binder along with other ingredients such as TDI, DOA, and Glycerol. The Cu-Co~* catalyst was used as 2% by weight to the total weight of catalyzed oxidizer and propellant samples. It was observed from the present study that, Cu-Co~* catalyst helps in reducing the Ea values for AN and AN based propellant samples. However, with the percentage increment of KDN in the AN crystals, Ea value increases.Further, it was observed that Cu-Co~* catalyst stabilizes the initial partial decomposition of KDN.展开更多
Experiments and computations were performed over an ogive-cylinder body having an lift-to-drag ratio of 16 at a diameter Reynolds number of 29000. The side force on the slender body augments with increasing angles of ...Experiments and computations were performed over an ogive-cylinder body having an lift-to-drag ratio of 16 at a diameter Reynolds number of 29000. The side force on the slender body augments with increasing angles of attack for the case without a ring. This increase was mainly due to the increase in the asymmetry of the existing vortex pair in the wake of the body. Attempts were made to completely reduce the existing side force at the angle of attack ranging from 35° to 45°.Three rectangular cross-sectioned circumferential rings having a height of 3% of the local diameter were placed at axial distances of 2.5, 3.5 and 4.5 times the base diameter from the tip of the body so as to reduce the side force. The results obtained indicate that inclusion of three rings completely alleviated the side force on the slender body at the angle of attack ranging from 0° to 45°. The presence of rings was found to alter the growth of the vortices that helped in the reduction of the side force. Computations performed were in reasonable agreement with the experiments.展开更多
The spaceplane is perspective vehicle due to wide maneuverability in comparison with a space capsule. Its maneuverability is expressed by the larger flight range and also by a possibility to rotate orbital inclination...The spaceplane is perspective vehicle due to wide maneuverability in comparison with a space capsule. Its maneuverability is expressed by the larger flight range and also by a possibility to rotate orbital inclination in the atmosphere by the aerodynamic and thrust forces. Orbital plane atmospheric rotation maneuvers can significantly reduce fuel costs compared to rocket-dynamic non-coplanar maneuver. However, this maneuver occurs at Mach numbers about 25, and such velocities lead to non-equilibrium chemical reactions in the shock wave. Such reactions change a physicochemical air property, and it affects aerodynamic coefficients. This paper investigates the influence of non-equilibrium reactions on the aerothrust aeroassisted maneuver with orbital change.The approach is to solve an optimization problem using the differential evolution algorithm with a temperature limitation. The spaceplane aerodynamic coefficients are determined by the numerical solution of the Reynolds-averaged Navier-Stokes equations. The aerodynamic calculations are conducted for the cases of perfect and non-equilibrium gases. A comparison of optimal trajectories,control laws, and fuel costs is made between models of perfect and non-equilibrium gases. The effect of a chemically reacting gas on the finite parameters is also evaluated using control laws obtained for a perfect gas.展开更多
Computations and Experiments were performed to get an understanding of the flow field around a rectangular supersonic air intake with pointed cowl [90°] at different back pressures for Mach 2.2. The effect of Cow...Computations and Experiments were performed to get an understanding of the flow field around a rectangular supersonic air intake with pointed cowl [90°] at different back pressures for Mach 2.2. The effect of Cowl shape on the ramp surface pressure distribution is discussed and compared with existing V-Notch [90°] intake model at free exit condition. It was found that using pointed cowl [90°] intake model, a better pressure recovery was achieved compared to the V-Notch [90°] intake model at Mach 2.2. Both Pointed and V-Notch intake models showed good starting characteristics. For change in back pressure, the occurence of normal shock, flow separation zone and flow reversal were observed. All experiments are performed only for the Pointed cowl [90°] intake model. All the 3-D computations were performed by using software available at B.I.T, Mesra, Ranchi.展开更多
A feature-constrained stereo matching algorithm for lunar rover navigation is presented based on the analysis of the stereo vision system and working environments of lunar rover. In feature-matching phase, edge points...A feature-constrained stereo matching algorithm for lunar rover navigation is presented based on the analysis of the stereo vision system and working environments of lunar rover. In feature-matching phase, edge points are extracted with wavelet transform and are used as the primitives for matching. Then three criterions are utilized in turn to select the correct matching points with the pyramidal searching strategy. As a result,the algorithm finds corresponding points successfully for large numbers of edge points. Area-matching is accomplished under the constraint of edge-matching results,and the correlation is selected as the criterion.Experimental results with real images of natural terrain indicate that the algorithm provides dense disparity maps with fairly high accuracy.展开更多
Nowadays,the use of Machine Learning(ML)onboard Earth Observation(EO)satellites has been investigated for a plethora of applications relying on multispectral and hyperspectral imaging.Traditionally,these studies have ...Nowadays,the use of Machine Learning(ML)onboard Earth Observation(EO)satellites has been investigated for a plethora of applications relying on multispectral and hyperspectral imaging.Traditionally,these studies have heavily relied on high-end data products,subjected to extensive pre-processing chains natively designed to be executed on the ground.However,replicating such algorithms onboard EO satellites poses significant challenges due to their computational intensity and need for additional metadata,which are typically unavailable on board.Because of that,current missions exploring onboard ML models implement simplified but still complex processing chains that imitate their on-ground counterparts.Despite these advancements,the potential of ML models to process raw satellite data directly remains largely unexplored.To fill this gap,this paper investigates the feasibility of applying ML models directly to Sentinel-2 raw data to perform thermal hotspot classification.This approach significantly limits the processing steps to simple and lightweight algorithms to achieve real-time processing of data with low power consumption.To this aim,we present an end-to-end(E2E)pipeline to create a binary classification map of Sentinel-2 raw granules,where each point suggests the absence/presence of a thermal anomaly in a square area of 2.5 km.To this aim,lightweight coarse spatial registration is applied to register three different bands,and an EfficientNetlite0 model is used to perform the classification of the various bands.The trained models achieve an average Matthew’s correlation coefficient(MCC)score of 0.854(on 5 seeds)and a maximum MCC of 0.90 on a geographically tripartite dataset of cropped images from the THRawS dataset.The proposed E2E pipeline is capable of processing a Sentinel-2 granule in 1.8 s and within 6.4 W peak power on a combination of Raspberry PI 4 and CogniSat-XE2 board,demonstrating real-time performance.展开更多
While novel artificial intelligence and machine learning techniques are evolving and disrupting established terrestrial technologies at an unprecedented speed,their adaptation onboard satellites is seemingly lagging.A...While novel artificial intelligence and machine learning techniques are evolving and disrupting established terrestrial technologies at an unprecedented speed,their adaptation onboard satellites is seemingly lagging.A major hindrance in this regard is the need for highquality annotated data for training such systems,which makes the development process of machine learning solutions costly,time-consuming,and inefficient.This paper presents“the OPS-SAT case”,a novel data-centric competition that seeks to address these challenges.The powerful computational capabilities of the European Space Agency’s OPS-SAT satellite are utilized to showcase the design of machine learning systems for space by using only the small amount of available labeled data,relying on the widely adopted and freely available open-source software.The generation of a suitable dataset,design and evaluation of a public data-centric competition,and results of an onboard experimental campaign by using the competition winners’machine learning model directly on OPS-SAT are detailed.The results indicate that adoption of open standards and deployment of advanced data augmentation techniques can retrieve meaningful onboard results comparatively quickly,simplifying and expediting an otherwise prolonged development period.展开更多
文摘This paper presents the catalytic effects of Cu-Co~* catalyst on the decomposition of AN and AN/KDN based oxidizer and propellant samples. Ozawa-Flynn-Wall(OFW) iso-conversional method was used for the kinetic studies and to compute the activation energy(Ea) values for various decomposition steps of the prepared oxidizer and propellant samples in the temperature range of 50 e500C. TG-DTG experiments were carried out for both oxidizer and propellant samples at the heating rates of 3, 5, and 10C/min. AN/KDN based oxidizer samples were prepared by an evaporative co-crystallization method. Citric acid sol-gel method was used for the synthesis of Cu-Co~* catalyst. The propellant sample contains HTPB as the fuel binder along with other ingredients such as TDI, DOA, and Glycerol. The Cu-Co~* catalyst was used as 2% by weight to the total weight of catalyzed oxidizer and propellant samples. It was observed from the present study that, Cu-Co~* catalyst helps in reducing the Ea values for AN and AN based propellant samples. However, with the percentage increment of KDN in the AN crystals, Ea value increases.Further, it was observed that Cu-Co~* catalyst stabilizes the initial partial decomposition of KDN.
文摘Experiments and computations were performed over an ogive-cylinder body having an lift-to-drag ratio of 16 at a diameter Reynolds number of 29000. The side force on the slender body augments with increasing angles of attack for the case without a ring. This increase was mainly due to the increase in the asymmetry of the existing vortex pair in the wake of the body. Attempts were made to completely reduce the existing side force at the angle of attack ranging from 35° to 45°.Three rectangular cross-sectioned circumferential rings having a height of 3% of the local diameter were placed at axial distances of 2.5, 3.5 and 4.5 times the base diameter from the tip of the body so as to reduce the side force. The results obtained indicate that inclusion of three rings completely alleviated the side force on the slender body at the angle of attack ranging from 0° to 45°. The presence of rings was found to alter the growth of the vortices that helped in the reduction of the side force. Computations performed were in reasonable agreement with the experiments.
基金partially supported by the Ministrv of Education and Science of the Russian Federation within the framework of the State Assignments to Higher Education Institutions and Research Organizations in scientific activity in the project#9.5453.2017/8.9。
文摘The spaceplane is perspective vehicle due to wide maneuverability in comparison with a space capsule. Its maneuverability is expressed by the larger flight range and also by a possibility to rotate orbital inclination in the atmosphere by the aerodynamic and thrust forces. Orbital plane atmospheric rotation maneuvers can significantly reduce fuel costs compared to rocket-dynamic non-coplanar maneuver. However, this maneuver occurs at Mach numbers about 25, and such velocities lead to non-equilibrium chemical reactions in the shock wave. Such reactions change a physicochemical air property, and it affects aerodynamic coefficients. This paper investigates the influence of non-equilibrium reactions on the aerothrust aeroassisted maneuver with orbital change.The approach is to solve an optimization problem using the differential evolution algorithm with a temperature limitation. The spaceplane aerodynamic coefficients are determined by the numerical solution of the Reynolds-averaged Navier-Stokes equations. The aerodynamic calculations are conducted for the cases of perfect and non-equilibrium gases. A comparison of optimal trajectories,control laws, and fuel costs is made between models of perfect and non-equilibrium gases. The effect of a chemically reacting gas on the finite parameters is also evaluated using control laws obtained for a perfect gas.
文摘Computations and Experiments were performed to get an understanding of the flow field around a rectangular supersonic air intake with pointed cowl [90°] at different back pressures for Mach 2.2. The effect of Cowl shape on the ramp surface pressure distribution is discussed and compared with existing V-Notch [90°] intake model at free exit condition. It was found that using pointed cowl [90°] intake model, a better pressure recovery was achieved compared to the V-Notch [90°] intake model at Mach 2.2. Both Pointed and V-Notch intake models showed good starting characteristics. For change in back pressure, the occurence of normal shock, flow separation zone and flow reversal were observed. All experiments are performed only for the Pointed cowl [90°] intake model. All the 3-D computations were performed by using software available at B.I.T, Mesra, Ranchi.
文摘A feature-constrained stereo matching algorithm for lunar rover navigation is presented based on the analysis of the stereo vision system and working environments of lunar rover. In feature-matching phase, edge points are extracted with wavelet transform and are used as the primitives for matching. Then three criterions are utilized in turn to select the correct matching points with the pyramidal searching strategy. As a result,the algorithm finds corresponding points successfully for large numbers of edge points. Area-matching is accomplished under the constraint of edge-matching results,and the correlation is selected as the criterion.Experimental results with real images of natural terrain indicate that the algorithm provides dense disparity maps with fairly high accuracy.
文摘Nowadays,the use of Machine Learning(ML)onboard Earth Observation(EO)satellites has been investigated for a plethora of applications relying on multispectral and hyperspectral imaging.Traditionally,these studies have heavily relied on high-end data products,subjected to extensive pre-processing chains natively designed to be executed on the ground.However,replicating such algorithms onboard EO satellites poses significant challenges due to their computational intensity and need for additional metadata,which are typically unavailable on board.Because of that,current missions exploring onboard ML models implement simplified but still complex processing chains that imitate their on-ground counterparts.Despite these advancements,the potential of ML models to process raw satellite data directly remains largely unexplored.To fill this gap,this paper investigates the feasibility of applying ML models directly to Sentinel-2 raw data to perform thermal hotspot classification.This approach significantly limits the processing steps to simple and lightweight algorithms to achieve real-time processing of data with low power consumption.To this aim,we present an end-to-end(E2E)pipeline to create a binary classification map of Sentinel-2 raw granules,where each point suggests the absence/presence of a thermal anomaly in a square area of 2.5 km.To this aim,lightweight coarse spatial registration is applied to register three different bands,and an EfficientNetlite0 model is used to perform the classification of the various bands.The trained models achieve an average Matthew’s correlation coefficient(MCC)score of 0.854(on 5 seeds)and a maximum MCC of 0.90 on a geographically tripartite dataset of cropped images from the THRawS dataset.The proposed E2E pipeline is capable of processing a Sentinel-2 granule in 1.8 s and within 6.4 W peak power on a combination of Raspberry PI 4 and CogniSat-XE2 board,demonstrating real-time performance.
文摘While novel artificial intelligence and machine learning techniques are evolving and disrupting established terrestrial technologies at an unprecedented speed,their adaptation onboard satellites is seemingly lagging.A major hindrance in this regard is the need for highquality annotated data for training such systems,which makes the development process of machine learning solutions costly,time-consuming,and inefficient.This paper presents“the OPS-SAT case”,a novel data-centric competition that seeks to address these challenges.The powerful computational capabilities of the European Space Agency’s OPS-SAT satellite are utilized to showcase the design of machine learning systems for space by using only the small amount of available labeled data,relying on the widely adopted and freely available open-source software.The generation of a suitable dataset,design and evaluation of a public data-centric competition,and results of an onboard experimental campaign by using the competition winners’machine learning model directly on OPS-SAT are detailed.The results indicate that adoption of open standards and deployment of advanced data augmentation techniques can retrieve meaningful onboard results comparatively quickly,simplifying and expediting an otherwise prolonged development period.
