Correction for ‘The modelling of a primitive ‘sustainable’ conservative cell’ by J. B. Bassingthwaighte (Phil. Trans. R. Soc. Lond. A 359, 1055–1072. (doi: 10.1098/rsta.2001.0821)). On p. 1055, the Digital Object Identifier should read 10.1098/rsta.2000.0821.
{"title":"Correction for Bassingthwaighte, The modelling of a primitive ‘sustainable’ conservative cell","authors":"J. Bassingthwaighte","doi":"10.1098/RSTA.2001.2004","DOIUrl":"https://doi.org/10.1098/RSTA.2001.2004","url":null,"abstract":"Correction for ‘The modelling of a primitive ‘sustainable’ conservative cell’ by J. B. Bassingthwaighte (Phil. Trans. R. Soc. Lond. A 359, 1055–1072. (doi: 10.1098/rsta.2001.0821)). On p. 1055, the Digital Object Identifier should read 10.1098/rsta.2000.0821.","PeriodicalId":20023,"journal":{"name":"Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2001-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81076420","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Fernando Moreira, José Roberto de França Arruda, D. Inman
In this paper, the design of a low–order controller for a high–order, smart–structural system is presented. The application considered here is a model of a solar panel dynamically similar to those used on satellites. Smart structure refers here to the use of integrated piezoceramic materials as sensors and actuators in the structural system in order to implement the control. The analytical contribution is made by extending the well–known robust control theory by relating the high–frequency robustness condition to the residual uncertainty, removing a trial–and–error step in the normal robust–control design. The procedure is applied experimentally to a half–metre long frame that is coupled in bending and torsion, verifying that the technique is viable for a reasonably complex structure.
{"title":"Design of a reduced–order H∞ controller for smart structure satellite applications","authors":"Fernando Moreira, José Roberto de França Arruda, D. Inman","doi":"10.1098/rsta.2001.0885","DOIUrl":"https://doi.org/10.1098/rsta.2001.0885","url":null,"abstract":"In this paper, the design of a low–order controller for a high–order, smart–structural system is presented. The application considered here is a model of a solar panel dynamically similar to those used on satellites. Smart structure refers here to the use of integrated piezoceramic materials as sensors and actuators in the structural system in order to implement the control. The analytical contribution is made by extending the well–known robust control theory by relating the high–frequency robustness condition to the residual uncertainty, removing a trial–and–error step in the normal robust–control design. The procedure is applied experimentally to a half–metre long frame that is coupled in bending and torsion, verifying that the technique is viable for a reasonably complex structure.","PeriodicalId":20023,"journal":{"name":"Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2001-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84286640","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Extensive work on the development of high–fidelity models of tethered systems has been carried out over the past three decades in support of the various space–tether missions flown to date. Although many of these models account for the full six–degrees–of–freedom motions of the end bodies, they did not consider a spinning tether. The reason is that most of the investigations are believed to focus on specific mission configurations such as the shuttle–based and space station–based applications. They addressed the particular features for that class of tethered systems and a spinning tether was not one of those features. However, from the flight of Canadian OEDIPUS–A (Observations of Electric–field Distributions in an Ionospheric Plasma – a Unique Strategy) mission, which was the first to involve a spinning tether, it is clear that the spin of the tether is an important factor that must be included in the modelling. This is especially true for a wire–like tether which has a finite bending stiffness. In this paper, a set of nonlinear equations of motion is formulated for a spacecraft comprising two rigid payloads with flexible booms and connected by a tether that is spinning at the same nominal rate as the end bodies. Additionally, closed–form infinitesimal and quasi–stability conditions that provide very useful design equations for a spinning tethered spacecraft are presented. One of the main findings of this work is the dominant role played by the subtle effects of the tether root bending on the dynamics of a spinning tethered spacecraft, particularly at high spin rates. Using our model, we show that these effects lead to the dynamics anomaly observed in the OEDIPUS–A mission, when the aft payload exhibited an unexpectedly rapid and large divergence of the coning angle.
{"title":"On the dynamics of spinning tethered space vehicles","authors":"G. Tyc, R. Han","doi":"10.1098/rsta.2001.0881","DOIUrl":"https://doi.org/10.1098/rsta.2001.0881","url":null,"abstract":"Extensive work on the development of high–fidelity models of tethered systems has been carried out over the past three decades in support of the various space–tether missions flown to date. Although many of these models account for the full six–degrees–of–freedom motions of the end bodies, they did not consider a spinning tether. The reason is that most of the investigations are believed to focus on specific mission configurations such as the shuttle–based and space station–based applications. They addressed the particular features for that class of tethered systems and a spinning tether was not one of those features. However, from the flight of Canadian OEDIPUS–A (Observations of Electric–field Distributions in an Ionospheric Plasma – a Unique Strategy) mission, which was the first to involve a spinning tether, it is clear that the spin of the tether is an important factor that must be included in the modelling. This is especially true for a wire–like tether which has a finite bending stiffness. In this paper, a set of nonlinear equations of motion is formulated for a spacecraft comprising two rigid payloads with flexible booms and connected by a tether that is spinning at the same nominal rate as the end bodies. Additionally, closed–form infinitesimal and quasi–stability conditions that provide very useful design equations for a spinning tethered spacecraft are presented. One of the main findings of this work is the dominant role played by the subtle effects of the tether root bending on the dynamics of a spinning tethered spacecraft, particularly at high spin rates. Using our model, we show that these effects lead to the dynamics anomaly observed in the OEDIPUS–A mission, when the aft payload exhibited an unexpectedly rapid and large divergence of the coning angle.","PeriodicalId":20023,"journal":{"name":"Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2001-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84040192","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Detailed modelling of contact dynamics involving a flexible space manipulator system and a payload is considered in this paper. The components undergoing direct contact (the end–effector of a manipulator and a payload) are modelled using the finite–element method, while the rest of the system is handled through the usual flexible multi–body formulation. Then, the system dynamics is composed of a set of differential equations subjected to sets of algebraic equations expressing kinematic or contact constraints. This dynamic model is then used to design a composite controller which must simultaneously achieve three goals: (i) trajectory tracking, (ii) force control and (iii) stabilization of the flexible degrees of freedom of the multi–body system. The singular perturbation method is used to obtain two reduced–order models; subsequently, the slow subsystem is used to design a hybrid position/force controller based on impedance control, and the fast subsystem is used to design a linear quadratic regulator (LQR).
{"title":"Contact dynamics and force control of space manipulator systems","authors":"S. W. Kim, A. Misra, V. Modi","doi":"10.1098/rsta.2001.0886","DOIUrl":"https://doi.org/10.1098/rsta.2001.0886","url":null,"abstract":"Detailed modelling of contact dynamics involving a flexible space manipulator system and a payload is considered in this paper. The components undergoing direct contact (the end–effector of a manipulator and a payload) are modelled using the finite–element method, while the rest of the system is handled through the usual flexible multi–body formulation. Then, the system dynamics is composed of a set of differential equations subjected to sets of algebraic equations expressing kinematic or contact constraints. This dynamic model is then used to design a composite controller which must simultaneously achieve three goals: (i) trajectory tracking, (ii) force control and (iii) stabilization of the flexible degrees of freedom of the multi–body system. The singular perturbation method is used to obtain two reduced–order models; subsequently, the slow subsystem is used to design a hybrid position/force controller based on impedance control, and the fast subsystem is used to design a linear quadratic regulator (LQR).","PeriodicalId":20023,"journal":{"name":"Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2001-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84452188","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper deals with the design algorithm of the first–stage attitude control for the M–V launch vehicle, Japan's scientific satellite carrier. The control features enhanced and robust characteristics against a range of uncertainties of the system parameters. To achieve sufficiently robust characteristics, the problem is approached within the framework of the H∞ mixed sensitivity problem. The emphasis is put on how to apply the robust control theory to a complicated real problem. In the design, the standard process is modified in a special way. The original, unstable plant dynamics are preliminarily stabilized by a direct output feedback prior to using the standard design process. Then the standard theory is applied to these pre–stabilized plant dynamics to yield control. The final form of the controller is provided by its combination with the pre–specified feedback. This modification of the procedure is prompted by the fact that it is not always effective in unstable systems. Thus, the controller can be derived much more easily. The effectiveness of the design has been finally established by the first ever flight of the vehicle successfully putting the world's first radio astronomy satellite into orbit.
{"title":"Attitude control design of the M–V rocket","authors":"Y. Morita, J. Kawaguchi","doi":"10.1098/rsta.2001.0887","DOIUrl":"https://doi.org/10.1098/rsta.2001.0887","url":null,"abstract":"This paper deals with the design algorithm of the first–stage attitude control for the M–V launch vehicle, Japan's scientific satellite carrier. The control features enhanced and robust characteristics against a range of uncertainties of the system parameters. To achieve sufficiently robust characteristics, the problem is approached within the framework of the H∞ mixed sensitivity problem. The emphasis is put on how to apply the robust control theory to a complicated real problem. In the design, the standard process is modified in a special way. The original, unstable plant dynamics are preliminarily stabilized by a direct output feedback prior to using the standard design process. Then the standard theory is applied to these pre–stabilized plant dynamics to yield control. The final form of the controller is provided by its combination with the pre–specified feedback. This modification of the procedure is prompted by the fact that it is not always effective in unstable systems. Thus, the controller can be derived much more easily. The effectiveness of the design has been finally established by the first ever flight of the vehicle successfully putting the world's first radio astronomy satellite into orbit.","PeriodicalId":20023,"journal":{"name":"Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2001-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74047436","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Based on the theory of modified constrained modal methods, in which the constraints can be defined on arbitrary points of the system or subsystems, a simplified method for free–free modal analysis is presented in this paper. Using this method, the rigid–body motion of structures can be eliminated by an arbitrary selection of the constraints. The constrained structures then become either statically determinate or indeterminate. Therefore, the inverse of the stiffness matrix of the constrained system exists. The modelling of the finite–element method can be verified or corrected via numerical or experimental results involving statically constrained and normal modes of the constrained system. Hence, the modal analysis of the free–free system can be easily performed using modal information from numerical or experimental results. The traditional modal experimental method of hanging with flexible strings can be changed, and the effective experimental methods can be chosen in accordance with the real condition of the test structure and site. To verify the effectiveness of this approach, several examples of a free–free rocket are presented. From the results, it can be clearly seen that the presented method is practical for modal analysis. Additionally, it is suitable for large space structures, especially those involving the assemblage of large flexible space structures. For such a system, generally, the components can be tested on–ground but the assemblage cannot, as it can only be deployed in space.
{"title":"Dynamic analysis of large–scale flexible systems for free—free space structures","authors":"Zhao-chang Zheng, D. Guo, Ye Zhang, Z. Hou","doi":"10.1098/rsta.2001.0883","DOIUrl":"https://doi.org/10.1098/rsta.2001.0883","url":null,"abstract":"Based on the theory of modified constrained modal methods, in which the constraints can be defined on arbitrary points of the system or subsystems, a simplified method for free–free modal analysis is presented in this paper. Using this method, the rigid–body motion of structures can be eliminated by an arbitrary selection of the constraints. The constrained structures then become either statically determinate or indeterminate. Therefore, the inverse of the stiffness matrix of the constrained system exists. The modelling of the finite–element method can be verified or corrected via numerical or experimental results involving statically constrained and normal modes of the constrained system. Hence, the modal analysis of the free–free system can be easily performed using modal information from numerical or experimental results. The traditional modal experimental method of hanging with flexible strings can be changed, and the effective experimental methods can be chosen in accordance with the real condition of the test structure and site. To verify the effectiveness of this approach, several examples of a free–free rocket are presented. From the results, it can be clearly seen that the presented method is practical for modal analysis. Additionally, it is suitable for large space structures, especially those involving the assemblage of large flexible space structures. For such a system, generally, the components can be tested on–ground but the assemblage cannot, as it can only be deployed in space.","PeriodicalId":20023,"journal":{"name":"Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2001-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79824187","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper presents a novel way of stabilizing the constraint drift dynamics in the numerical simulation of multibody systems. This formulation is applicable for a large class of uncertain mechanical systems described by nonlinear differential algebraic equations that are subject to holonomic constraints. In the absence of uncertainty in the system inertia parameters, it is possible to develop stabilization relationships that suppress the accumulation of error in the constraint equations during the time integration process. In order to account for ignorance in the parameters, we propose a model reference adaptive control scheme that ensures the asymptotic realization of the desired (reference) constraint violation dynamics. Special attention is given to the case of redundantly actuated systems, as is typical for robotics. For this class of problems, we direct special attention to optimization criteria that achieve any desired manoeuvre using minimum control effort and coordination between the redundant set of actuators. An example application demonstrates the effectiveness and practicality of the proposed adaptive control formulation.
{"title":"Adaptive realization of desired constraint stabilization dynamics in the control of multibody systems","authors":"J. Junkins, M. Akella, A. Kurdila","doi":"10.1098/rsta.2001.0884","DOIUrl":"https://doi.org/10.1098/rsta.2001.0884","url":null,"abstract":"This paper presents a novel way of stabilizing the constraint drift dynamics in the numerical simulation of multibody systems. This formulation is applicable for a large class of uncertain mechanical systems described by nonlinear differential algebraic equations that are subject to holonomic constraints. In the absence of uncertainty in the system inertia parameters, it is possible to develop stabilization relationships that suppress the accumulation of error in the constraint equations during the time integration process. In order to account for ignorance in the parameters, we propose a model reference adaptive control scheme that ensures the asymptotic realization of the desired (reference) constraint violation dynamics. Special attention is given to the case of redundantly actuated systems, as is typical for robotics. For this class of problems, we direct special attention to optimization criteria that achieve any desired manoeuvre using minimum control effort and coordination between the redundant set of actuators. An example application demonstrates the effectiveness and practicality of the proposed adaptive control formulation.","PeriodicalId":20023,"journal":{"name":"Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2001-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79743477","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A few months after launch of the TOPEX/POSEIDON (T/P) spacecraft, during the verification phase of the mission, the Precision Orbit Determination Team discovered residual along–track accelerations which were unexpected and of unknown origin. This paper describes the analysis of radiation forces acting on the T/P spacecraft for the purpose of understanding and providing an explanation for the anomalous accelerations. The radiation forces acting on the solar array, which experiences warping due to temperature differences between the front and back surfaces, are analysed and the resulting along–track accelerations are determined. This analysis led to the development of a new radiation force model which includes (1) warping of the solar array, (2) solar array deployment deflections as large as 2°, (3) necessary adjustments to certain surface property parameters, and (4) an adjustment to the coefficient of drag. As a result of the new model, estimates of the empirical constant along–track acceleration are significantly reduced in magnitude and are less dependent upon the location of the Sun relative to the orbit plane.
{"title":"Modelling the anomalous acceleration and radiation pressure forces for the TOPEX/POSEIDON spacecraft","authors":"D. Kubitschek, G. Born","doi":"10.1098/rsta.2001.0882","DOIUrl":"https://doi.org/10.1098/rsta.2001.0882","url":null,"abstract":"A few months after launch of the TOPEX/POSEIDON (T/P) spacecraft, during the verification phase of the mission, the Precision Orbit Determination Team discovered residual along–track accelerations which were unexpected and of unknown origin. This paper describes the analysis of radiation forces acting on the T/P spacecraft for the purpose of understanding and providing an explanation for the anomalous accelerations. The radiation forces acting on the solar array, which experiences warping due to temperature differences between the front and back surfaces, are analysed and the resulting along–track accelerations are determined. This analysis led to the development of a new radiation force model which includes (1) warping of the solar array, (2) solar array deployment deflections as large as 2°, (3) necessary adjustments to certain surface property parameters, and (4) an adjustment to the coefficient of drag. As a result of the new model, estimates of the empirical constant along–track acceleration are significantly reduced in magnitude and are less dependent upon the location of the Sun relative to the orbit plane.","PeriodicalId":20023,"journal":{"name":"Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2001-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90425077","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
I. Franchi, L. Baker, J. Bridges, I. Wright, C. Pillinger
Meteorites preserve a wide range of oxygen isotopic signatures from the time of the Solar System's formation. Most of these rocks record complex histories, each phase of which has the potential for overwriting initial oxygen signatures. The unequilibrated ordinary chondrites reveal evidence of hydrothermal alteration through isotopic disequilibrium within chondrules and in secondary magnetites, which we can now constrain to temperatures of 140–180°C. The effects of this alteration are progressively obliterated by later thermal metamorphism. Further heating leads to melting (shown in achondritic meteorites), producing well–defined mass–fractionation lines using high–precision analyses. The oxygen from low–temperature minerals in carbonaceous chondrites reveals high levels of isotopic uniformity, suggesting that the aqueous alteration occurred under open–system conditions. The initial isotopic composition of the water from the ordinary chondrites is quite distinct from that in the carbonaceous chondrites, but both fall on a single line of slope 1.0, as do the initial anhydrous silicate compositions. This is taken to show that a process generating a mass–independent fractionation was responsible for most of the oxygen–isotopic variation seen in meteorites. Subsequent aqueous alteration of the meteorite parent bodies involving these components is then capable of producing the full observed variation.
{"title":"Oxygen isotopes and the early Solar System","authors":"I. Franchi, L. Baker, J. Bridges, I. Wright, C. Pillinger","doi":"10.1098/rsta.2001.0894","DOIUrl":"https://doi.org/10.1098/rsta.2001.0894","url":null,"abstract":"Meteorites preserve a wide range of oxygen isotopic signatures from the time of the Solar System's formation. Most of these rocks record complex histories, each phase of which has the potential for overwriting initial oxygen signatures. The unequilibrated ordinary chondrites reveal evidence of hydrothermal alteration through isotopic disequilibrium within chondrules and in secondary magnetites, which we can now constrain to temperatures of 140–180°C. The effects of this alteration are progressively obliterated by later thermal metamorphism. Further heating leads to melting (shown in achondritic meteorites), producing well–defined mass–fractionation lines using high–precision analyses. The oxygen from low–temperature minerals in carbonaceous chondrites reveals high levels of isotopic uniformity, suggesting that the aqueous alteration occurred under open–system conditions. The initial isotopic composition of the water from the ordinary chondrites is quite distinct from that in the carbonaceous chondrites, but both fall on a single line of slope 1.0, as do the initial anhydrous silicate compositions. This is taken to show that a process generating a mass–independent fractionation was responsible for most of the oxygen–isotopic variation seen in meteorites. Subsequent aqueous alteration of the meteorite parent bodies involving these components is then capable of producing the full observed variation.","PeriodicalId":20023,"journal":{"name":"Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2001-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79571759","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
When the most primitive types of meteorite, the chondrites, formed, all of them incorporated small amounts of at least two types of unprocessed pre–solar material: interstellar organic matter and circumstellar grains. The organic matter formed in the protosolar molecular cloud. To date, six types of circumstellar grain have been identified and their isotopic compositions show that they formed around red giant/asymptotic giant branch (RGB/AGB) stars, supernovae and, possibly, novae and Wolf–Rayet stars. The range of isotopic compositions exhibited by the pre–solar grains requires a minimum of 35–40 stellar sources, suggesting that the circumstellar grains are a fairly representative sample of circumstellar dust production in the Galaxy. Comparison of the observed proportions of circumstellar grains with astronomical estimates reveals both striking similarities and differences. The differences probably reflect our ignorance of circumstellar dust formation rather than differential destruction in the interstellar medium or the Solar System. Silicates are predicted to be one of the dominant types of circumstellar grain, but they have yet to be isolated from meteorites. However, interstellar silicates may have been identified in interplanetary dust particles. The pre–solar materials demonstrate that some matter was never strongly heated during Solar System formation. There is no evidence for one dominant source of circumstellar grains, as might have occurred if Solar System formation was triggered by a supernova/AGB–generated shock wave or if refractory supernova condensates produced the widespread mass–independent oxygen isotopic variations found in Solar System materials.
{"title":"Inherited material from the protosolar cloud: composition and origin","authors":"C. Alexander","doi":"10.1098/rsta.2001.0891","DOIUrl":"https://doi.org/10.1098/rsta.2001.0891","url":null,"abstract":"When the most primitive types of meteorite, the chondrites, formed, all of them incorporated small amounts of at least two types of unprocessed pre–solar material: interstellar organic matter and circumstellar grains. The organic matter formed in the protosolar molecular cloud. To date, six types of circumstellar grain have been identified and their isotopic compositions show that they formed around red giant/asymptotic giant branch (RGB/AGB) stars, supernovae and, possibly, novae and Wolf–Rayet stars. The range of isotopic compositions exhibited by the pre–solar grains requires a minimum of 35–40 stellar sources, suggesting that the circumstellar grains are a fairly representative sample of circumstellar dust production in the Galaxy. Comparison of the observed proportions of circumstellar grains with astronomical estimates reveals both striking similarities and differences. The differences probably reflect our ignorance of circumstellar dust formation rather than differential destruction in the interstellar medium or the Solar System. Silicates are predicted to be one of the dominant types of circumstellar grain, but they have yet to be isolated from meteorites. However, interstellar silicates may have been identified in interplanetary dust particles. The pre–solar materials demonstrate that some matter was never strongly heated during Solar System formation. There is no evidence for one dominant source of circumstellar grains, as might have occurred if Solar System formation was triggered by a supernova/AGB–generated shock wave or if refractory supernova condensates produced the widespread mass–independent oxygen isotopic variations found in Solar System materials.","PeriodicalId":20023,"journal":{"name":"Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2001-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88473687","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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