CN113343369B - Perturbation analysis method for spacecraft aerodynamic fusion orbit - Google Patents
Perturbation analysis method for spacecraft aerodynamic fusion orbit Download PDFInfo
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Abstract
The invention discloses a perturbation analysis method for a spacecraft aerodynamic fusion orbit, which relates to the field of aerospace forecasting, and the perturbation analysis method comprehensively considers the influences of a refined cross-basin aerodynamic modeling and a posture rotation effect and forecasts the information of a degradation orbit of the spacecraft in advance, overcomes the defect that the traditional technical method does not take pneumatic influence factors into consideration, can remarkably improve the forecasting precision of the large-scale uncontrolled spacecraft in an orbit flight and reentry process, can prejudge in advance, thus providing a basis for forecasting of information such as reentry time position and the like, and being beneficial to developing problem solving forecasting, hazard analysis and risk assessment of the reentry process of the large-scale uncontrolled spacecraft; meanwhile, the technology can support multidisciplinary coupling research and optimization design of the problems of uncontrolled reentry of a large spacecraft, maneuvering orbital transfer and the like.
Description
Technical Field
The invention relates to the field of space forecasting, in particular to a perturbation analysis method for a spacecraft aerodynamic fusion orbit.
Background
The process of returning and re-entering the earth atmosphere by the large spacecraft at the end of the service life can be divided into uncontrolled re-entry and controlled off-orbit re-entry. Large-scale spacecrafts without controlled reentry are usually out of control due to communication faults and finally naturally derail and reenter the atmosphere. Historically, large spacecraft have failed and then entered the atmosphere in many cases, such as the "Skylab" space station in the united states. After the service life of the large-scale spacecraft is ended, the orbit height is gradually reduced to finally enter the atmosphere under the influence of perturbation factors such as atmospheric resistance, gravitational attraction and the like in a low-earth orbit environment, the flight attitude, the trajectory and the falling area of the spacecraft are not controllable under the condition, and the risk of accidents caused by disintegration fragments to a population dense area must be avoided by means of forecasting in advance. The method can accurately and reliably track and forecast the orbit evolution of the spacecraft in the orbit degradation process, can obviously reduce the harmfulness of a reentry disintegration zone, improves the reentry forecast precision, and has very important significance for developing the orbit forecast, collision early warning and on-orbit service technology of space non-cooperative targets.
Generally, the whole natural meteority process of the spacecraft is divided into an orbit attenuation process, a reentry disintegration process and a disintegration debris fragment distribution process, and demarcation points of all stages can be respectively assumed to be an orbit descent reentry point and a spacecraft disintegration process. In order to reliably forecast the time, position and speed information of the spacecraft in the derailing reentry, a countermeasure must be made in advance and feasible derailing input parameters are provided for the disintegration process and the calculation of the debris scattering, which needs a reliable orbit forecasting model. The internationally common method for medium-and-long-term forecasting of low-orbit spacecraft is to forecast by combining two-line root (TLE) and a simplified root perturbation model. The TLE (Two-Line Element) data format is a Two-Line orbit number which is internationally and generally used at present and used for describing satellite orbit parameters, the conventional TLE data comprises parameters such as ephemeris of a satellite, a flat orbit number and the like, and does not comprise orbit error information, and errors of the TLE data are influenced by factors such as observation equipment, an orbit model, observation data, space environment conditions and the like. Because the number of TLE tracks is the average number of tracks, if the instantaneous number of tracks is to be obtained, extrapolation is carried out according to a set track forecasting model, namely, the track forecasting models such as SGP4 or SGP8, and corresponding disturbance terms are added, and the SGP4 track forecasting model is selected as a reference model to carry out track number extrapolation calculation. The SGP4 model was developed in 1966 based on Kozai's analytic theory. The error source of the prediction accuracy of the TLE + SGP4 model mainly comprises two aspects: the method is characterized in that TLE root errors exist, and an index atmospheric density model with atmospheric density changing along with altitude is adopted by an SGP4 model. The main unknown item in the TLE number is the aerodynamic resistance item, and the conventional method is to use historical data to solve the TLE number and other orbit numbers together to obtain an averaged calculation initial value, and the prediction process is an invariant item, which may cause large error accumulation. The resistance coefficient items obtained by simply depending on historical data fitting still cannot meet the forecasting precision.
The atmospheric resistance has obvious influence on the orbit prediction of the low-orbit spacecraft, 5% of resistance error is considered, and the maximum error of the 24-hour position calculation precision of the low-orbit space target can reach 64 km. For the process that a large-scale spacecraft returns from a space orbit and reenters, the large-scale spacecraft can experience the stages of in-orbit free molecular flow, thin transition flow, high-altitude near-continuous slip flow and the like in sequence, and the process is a cross-watershed multi-scale non-equilibrium change process. How to accurately simulate the problem of cross-basin complex multi-physical-field unbalanced streaming in the process of the large spacecraft returning to the reentry in an uncontrolled manner at extremely high speed plays a crucial role in the on-orbit flight and reentry forecasting precision of the large spacecraft.
In the existing internationally adopted spacecraft orbit forecasting methods, a method of fitting a ballistic coefficient is adopted for aerodynamic consideration, even a constant resistance coefficient mode is directly adopted aerodynamically, the influence of the near-earth orbit cross-basin aerodynamic characteristics on the aerodynamic force and moment coefficient of a large spacecraft under different orbit heights and attitudes is not considered, and the influence on the aerodynamic characteristic change and the perturbation of the medium and long-term orbit caused by the attitude change of the large uncontrolled spacecraft is not fully considered. However, the flight and reentry process of the actual large uncontrolled spacecraft is subjected to complex cross-basin aerodynamic perturbation under the conditions of different orbit heights and flight attitudes. As a non-conservative force, the energy dissipation of the large-scale spacecraft caused by aerodynamic force in the process of in-orbit flight is difficult to ignore, and even is a main factor influencing the process of converting the elliptical orbit into the near-circular orbit. The existing technical method cannot fully consider the influence of the aerodynamic characteristics and attitude changes of the near-earth orbit cross-basin unbalanced streaming on the perturbation of the orbit of the large spacecraft, so that the orbit prediction precision is insufficient, and misleading influence can be even generated on the decision of flight control.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a perturbation analysis method for a spacecraft aerodynamic fusion orbit, and the method can improve the calculation precision of on-orbit flight and reentry forecast.
In order to achieve the above object, the present invention provides a perturbation analysis method for a spacecraft aerodynamic fusion orbit, which comprises:
step 1: generating first two-row root orbit root information of a spacecraft based on ephemeris data and instantaneous orbit root information in observation data corresponding to the initial moment of the spacecraft;
step 2: calculating to obtain the initial orbit height and the initial velocity vector of the spacecraft based on the state variable of the first two-row root orbit root information of the spacecraft; establishing a coordinate rotation matrix for describing the attitude change of the spacecraft based on the initial attitude observation data of the spacecraft, and converting the initial attitude observation data according to the coordinate rotation matrix to obtain an initial attack angle and an initial sideslip angle;
and step 3: calculating and obtaining an initial aerodynamic drag coefficient and an initial aerodynamic disturbance moment coefficient of the spacecraft based on the initial orbit altitude, the initial velocity vector, the initial angle of attack and the initial sideslip angle;
and 4, step 4: calculating to obtain a ballistic coefficient based on the initial aerodynamic resistance coefficient and the surface-to-mass ratio of the spacecraft, and replacing a resistance item in the first two-row radical orbit radical information by using the ballistic coefficient to obtain second two-row radical orbit radical information;
and 5: performing track root information extrapolation calculation based on the second two-line root track root information and the track forecasting model to obtain the track height and the velocity vector of the spacecraft corresponding to the next moment; if the orbit altitude obtained in the step 5 reaches the reentry orbit altitude, outputting ephemeris data and orbit information of the spacecraft corresponding to the next moment; if the height of the track obtained in the step 5 does not reach the height of the reentry track, executing a step 6;
step 6: calculating attitude angle data corresponding to the spacecraft at the next moment by using a state equation of the spacecraft based on the initial attitude observation data and the initial aerodynamic disturbance moment coefficient, and converting the attitude angle data according to the coordinate rotation matrix to obtain an attack angle and a sideslip angle corresponding to the next moment;
and 7: and substituting the orbit altitude, the velocity vector and the attack angle and the sideslip angle obtained in the step 5 and obtained in the step 6 into the step 3 to calculate and obtain the aerodynamic resistance coefficient and the aerodynamic disturbance moment coefficient of the spacecraft corresponding to the next moment, and continuing to iteratively execute the steps 4 to 7 based on the aerodynamic resistance coefficient and the aerodynamic disturbance moment coefficient of the spacecraft corresponding to the next moment until the orbit altitude obtained in the step 5 reaches the re-entering orbit altitude.
The orbit attenuation simulation of the large uncontrolled spacecraft in the low-earth orbit environment needs to fully consider the influence of cross-basin aerodynamic characteristics on the orbit attenuation process, meanwhile, most uncontrolled reentry spacecrafts are in an attitude out-of-control state, and the influence of the rotating attitude of the spacecraft needs to be simultaneously considered when the orbit dynamics characteristics of the large uncontrolled spacecraft in the low-orbit or even ultra-low orbit condition at the end of the service life are researched. Therefore, a higher-precision pneumatic coefficient modeling method needs to be integrated into an orbit dynamics model by combining the attitude and the cross-basin pneumatic environment, so that the on-orbit flight and reentry forecast precision is improved. The method considers the influence of the near-earth orbit cross-basin aerodynamic characteristics on the aerodynamic force and moment coefficient of the large spacecraft under different orbit heights and attitudes, and fully considers the influence on the aerodynamic characteristic change caused by the attitude change of the large uncontrolled spacecraft and the perturbation of the medium and long-term orbit, so that the method considers the attitude rotation effect of the large uncontrolled spacecraft, establishes a pneumatic localization fast engineering algorithm based on the cross-basin aerodynamic characteristics, establishes a pneumatic fusion orbit perturbation analysis method by combining with an average orbit root number model, and can improve the calculation precision of on-orbit flight and reentry prediction.
Preferably, in the method, the step 1 specifically includes: acquiring observation data corresponding to the initial time of the spacecraft in a J2000 geocentric inertial coordinate system, and generating the first two-row root orbit root information in a TEME instant true equator spring deciduous point coordinate system based on ephemeris data and instant orbit root information in the observation data.
Preferably, in the method, the orbit prediction model is an SGP4 model.
Preferably, in the method, the state variable of the two-row root track root information is represented as:
wherein the content of the first and second substances,as a matter of time, the time is,the average number of tracks in the form of a two-row number,is time of dayIncluding position and velocity,for SGP4 model function, initial timeCorresponding variableThe average number of tracks in the form of a two-row number,including eccentricityInclination of the trackThe right ascension channelArgument of near placeFlat near point angleAnd average angular velocity;
Resistance term in two rows of radicalsFor normalized atmospheric drag coefficients, the form is calculated as:
wherein the content of the first and second substances,is a dimensionless aerodynamic drag coefficient,for space flightThe surface-to-quality ratio of the device;in order to be the reference value of the atmospheric density,,the radius of the earth.
wherein the content of the first and second substances,is the aerodynamic force applied to the spacecraft,is the average atmospheric density at the altitude where the spacecraft is located,is the characteristic area of the spacecraft,is the velocity of the spacecraft relative to the atmosphere.
Preferably, a coordinate rotation matrix describing the change of the spacecraft attitude is established based on the initial attitude observation data of the spacecraft, and the initial attitude observation data is converted according to the coordinate rotation matrix to obtain an initial attack angle and an initial sideslip angle, which specifically includes:
step a: calculating to obtain initial attitude angle data of the spacecraft based on the initial attitude observation data of the spacecraft;
step b: describing the initial attitude angle data in a quaternion form, and establishing a coordinate rotation matrix for describing attitude change;
step c: and converting the initial attitude angle data of the spacecraft into an airflow coordinate system to convert the initial attitude angle data and the coordinate rotation matrix to obtain an initial attack angle and an initial sideslip angle.
Preferably, in order to avoid the singularity of the solution, the method describes the attitude change of the spacecraft in a quaternion mode, and the state equation of the spacecraft in the step 6 is obtained by combining an attitude kinematics equation of the spacecraft and an attitude dynamics equation of the spacecraft;
describing the attitude change of the spacecraft in a quaternion mode, wherein the attitude kinematic equation of the spacecraft described by the quaternion is obtained by the following steps:
wherein the content of the first and second substances,is the differential quantity of the attitude quaternion,is the quaternion of the attitude,for the cross-product sign of the vector matrix,representing the angular velocity of the extended projectile coordinate system relative to the orbital coordinate system and the inertial angular velocity of the projectileThe relationship of (1) is:
wherein the content of the first and second substances,the rotating angular velocity of the spacecraft projectile system,the symbols are transposed for the matrix,a pose matrix of the projectile coordinate system to the orbit coordinate system described by a quaternion,for the track angular velocity, a coordinate rotation matrix for describing the attitude change in a quaternion form can be obtained by combining the specified coordinate axis rotation sequence;
the attitude dynamics equation of the spacecraft is as follows:
wherein the content of the first and second substances,is a matrix of the moment of inertia of the spacecraft,is the angular velocity vector of the rotation of the spacecraft,is the differential quantity of the rotation angular velocity vector of the spacecraft,in order to be a gravity gradient moment,is a pneumatic disturbance moment;is marked as,Is gyro moment;
the state equation of the spacecraft is expressed as:
whereinIn order to be a state variable, the state variable,is a generalized matrix of quaternion differential quantities,,is the angular velocity of rotation of the spacecraft about the x-axis,is the differential quantity of the rotation angular velocity of the spacecraft around the x-axis,is the angular velocity of the spacecraft about the y-axis,is the differential quantity of the rotation angular velocity of the spacecraft around the y-axis,is the angular velocity of the spacecraft about the z-axis,is a differential quantity of the rotation angular velocity of the spacecraft around the z-axis,、、andthe differential quantities are respectively corresponding to four elements of a quaternion;
and integrating the state variable by using the state equation of the spacecraft to obtain the attitude angle data of the spacecraft at the required moment.
Preferably, the aerodynamic disturbance torque is used in the methodThe method comprises the following steps:、and,、andthe calculation method is as follows:
wherein the roll moment coefficient isCoefficient of pitching moment ofYaw moment coefficient ofThe characteristic length of the spacecraft is,In order to be a gravity gradient moment,for aerodynamic disturbance moments on the x-axis,for the aerodynamic disturbance moment on the y-axis,for aerodynamic disturbance moments in the z-axis,is the average atmospheric density at the altitude where the spacecraft is located,is the characteristic area of the spacecraft,is the velocity of the spacecraft relative to the atmosphere.
wherein the content of the first and second substances,is the radial diameter of the aerodynamic pressure center relative to the mass center of the spacecraft,is the aerodynamic force that the spacecraft is subjected to.
One or more technical schemes provided by the invention at least have the following technical effects or advantages:
the invention provides an orbit perturbation analysis method of a large-scale uncontrolled spacecraft, which comprehensively considers the influences of fine cross-basin aerodynamic modeling and attitude rotation effect, and forecasts the degradation orbit information of the spacecraft in advance, overcomes the defect that the traditional technical method does not take pneumatic influence factors into consideration, can remarkably improve the forecasting precision of the in-orbit flight and reentry process of the large-scale uncontrolled spacecraft, can forecast in advance, provides a basis for forecasting of information such as reentry time and position and the like, and is favorable for developing problem solving forecasting, hazard analysis and risk assessment of the reentry process of the large-scale uncontrolled spacecraft. Meanwhile, the technology can support multidisciplinary coupling research and optimization design of the problems of uncontrolled reentry of a large spacecraft, maneuvering orbital transfer and the like.
Drawings
The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention;
FIG. 1 is a schematic flow chart of a perturbation analysis method for a spacecraft aerodynamic fusion orbit in the invention.
Detailed Description
In order that the above objects, features and advantages of the present invention can be more clearly understood, a more particular description of the invention will be rendered by reference to the appended drawings. It should be noted that the embodiments of the present invention and features of the embodiments may be combined with each other without conflicting with each other.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, however, the present invention may be practiced in other ways than those specifically described and thus the scope of the present invention is not limited by the specific embodiments disclosed below.
Example one
Referring to fig. 1, fig. 1 is a schematic flow chart of a method for analyzing perturbation of a spacecraft aerodynamic fusion orbit, and an embodiment of the present invention provides a method for analyzing perturbation of a spacecraft aerodynamic fusion orbit, where the method includes:
step 1: generating first two-row root orbit root information of a spacecraft based on ephemeris data and instantaneous orbit root information in observation data corresponding to the initial moment of the spacecraft;
step 2: calculating to obtain the initial orbit height and the initial velocity vector of the spacecraft based on the state variable of the first two-row root orbit root information of the spacecraft; establishing a coordinate rotation matrix for describing the attitude change of the spacecraft based on the initial attitude observation data of the spacecraft, and converting the initial attitude observation data according to the coordinate rotation matrix to obtain an initial attack angle and an initial sideslip angle;
and step 3: calculating and obtaining an initial aerodynamic drag coefficient and an initial aerodynamic disturbance moment coefficient of the spacecraft based on the initial orbit altitude, the initial velocity vector, the initial angle of attack and the initial sideslip angle;
and 4, step 4: calculating to obtain a ballistic coefficient based on the initial aerodynamic resistance coefficient and the surface-to-mass ratio of the spacecraft, and replacing a resistance item in the first two-row radical orbit radical information by using the ballistic coefficient to obtain second two-row radical orbit radical information;
and 5: performing track root information extrapolation calculation based on the second two-line root track root information and the track forecasting model to obtain the track height and the velocity vector of the spacecraft corresponding to the next moment; if the orbit altitude obtained in the step 5 reaches the reentry orbit altitude, outputting ephemeris data and orbit information of the spacecraft corresponding to the next moment; if the height of the track obtained in the step 5 does not reach the height of the reentry track, executing a step 6;
step 6: calculating attitude angle data corresponding to the spacecraft at the next moment by using a state equation of the spacecraft based on the initial attitude observation data and the initial aerodynamic disturbance moment coefficient, and converting the attitude angle data according to the coordinate rotation matrix to obtain an attack angle and a sideslip angle corresponding to the next moment;
and 7: and substituting the orbit altitude, the velocity vector and the attack angle and the sideslip angle obtained in the step 5 and obtained in the step 6 into the step 3 to calculate and obtain the aerodynamic resistance coefficient and the aerodynamic disturbance moment coefficient of the spacecraft corresponding to the next moment, and continuing to iteratively execute the steps 4 to 7 based on the aerodynamic resistance coefficient and the aerodynamic disturbance moment coefficient of the spacecraft corresponding to the next moment until the orbit altitude obtained in the step 5 reaches the re-entering orbit altitude.
In the first embodiment of the present invention, the method specifically includes the following steps:
and generating TLE two-row root orbit information under a TEME instantaneous true equator vernal equinox coordinate system by using ephemeris and instantaneous orbit root information contained in the initial-moment observation data of the large-scale uncontrolled spacecraft under the existing J2000 geocentric inertial coordinate system.
The method comprises the steps of calculating to obtain an initial orbit height and a velocity vector by utilizing initial instantaneous orbit root information of the large-scale uncontrolled spacecraft, obtaining an initial attack angle and a sideslip angle by utilizing initial attitude observation data of the large-scale uncontrolled spacecraft, calling a pneumatic localization fast engineering algorithm, and calculating to obtain an initial pneumatic resistance coefficient of the large-scale uncontrolled spacecraft and a pneumatic moment coefficient for solving an attitude dynamic equation.
Calculating a ballistic coefficient by utilizing the initial aerodynamic resistance coefficient and the surface-to-mass ratio of the large uncontrolled spacecraft, and replacing the resistance item in two lines of TLE (total line of space) with the calculated ballistic coefficient。
And performing orbit extrapolation calculation by combining two lines of TLE elements containing updated resistance terms with an SGP4 model to obtain the position and speed information of the large-scale uncontrolled spacecraft at the next moment, calling a pneumatic localization fast engineering algorithm and an attitude dynamics calculation program, and integrating to obtain the pneumatic resistance coefficient, the pneumatic moment coefficient and the attitude angle information at the next moment.
And converting the orbit height according to the position and speed information at the next moment, judging whether the given reentry orbit height is reached, if so, terminating the calculation, and outputting the ephemeris and the orbit information at the moment.
If the specified re-entry height is not reached, the pneumatic resistance coefficient at the next moment is also used to update the TLE two-line number of resistance termsAnd returning to the step of calculating the orbit extrapolation, and sequentially and iteratively calculating until the given height of the reentry orbit is reached, terminating the calculation and outputting the ephemeris and the orbit information at the termination moment.
The method comprises the following specific technical scheme:
firstly, the instantaneous orbit root and ephemeris information obtained by observation data under a J2000 geocentric inertial coordinate system need to be converted into a TLE two-row root model. The SGP4 model adopts a true equator vernal equinox coordinate system, and the state variable of two-row root of TLE can be expressed as
Wherein the content of the first and second substances,is time of dayThe state vector (position and velocity) of (c),for SGP4 model function, corresponding to initial timeVariable of (2)Then the average number of tracks in TLE formIncluding eccentricityInclination of the trackThe right ascension channelArgument of near placeFlat near point angleAnd average angular velocityIn particular the resistance term in the two-line root of TLEFor normalized atmospheric drag coefficients, the form is calculated as follows:
wherein the content of the first and second substances,is a dimensionless aerodynamic drag coefficient,the surface-to-mass ratio of the large uncontrolled spacecraft is obtained;in order to be the reference value of the atmospheric density,,the radius of the earth. Solving equation (1) can obtain the position and speed information at any moment.
And then, a localized fast engineering algorithm of aerodynamic force and moment coefficients of the large uncontrolled spacecraft needs to be established based on the cross-basin aerodynamic characteristics. Because the aerodynamic coefficient of the large uncontrolled spacecraft obviously changes along with the height and the attitude of the orbit, the high efficiency of the calculation of the aerodynamic characteristics is also considered according to the quick response of the return and reentry processes of the spacecraft in the orbit forecasting process.
The large uncontrolled spacecraft orbit flight process is a very high supersonic flow problem of a high rarefied free molecular flow state of hundreds to tens of orders of magnitude Knudsen and a complex configuration of a multi-physics field, and the cross-basin gas flow problem experienced in the low orbit flight process can be solved by adopting a unified algorithm. The free molecular flow theory is adopted to control the highly thin flow region, and Nocilla wall reflection models corrected based on different model materials can be adopted to calculate the pressure coefficient and the friction coefficient. Under the assumption of a Maxwell equilibrium state gas molecule velocity distribution function, the pressure and friction coefficient of each surface element can be calculated, and verification analysis correctness is confirmed. In the continuous flow region where Knudsen numbers tend to be very small, it can be based on modified Newton's theory of non-viscous flow. However, aiming at the long orbit decay of the large uncontrolled spacecraft, the large uncontrolled spacecraft undergoes the unbalanced reentry process of multiple physical fields and multiple scales in different flight attitudes, in order to reliably capture the influence of aerodynamic characteristics on different arc-segment orbits, the method specifically adopts a literature that the aerodynamic characteristics of the cross-basin are summarized and described in the general literature of integrated modeling and calculation research (manned space) of the low-orbit control aerodynamic characteristics of the spacecraft, and the method establishes the pneumatic localization fast engineering algorithm based on the cross-basin aerodynamic characteristics without repeated description, and calculating typical streaming states of the spacecraft in the height areas (340 km,280km, 200km and 120 km) in the process of descending the spacecraft from the orbit to the reentry respectively at intervals of 10km, 5km and 2.5km by using a cross-streaming area aerodynamic numerical method, and taking the result as the boundary value of each sub-area. And for the middle transition zone connecting the boundaries of each sub-zone, a modified Boettcher/Legge asymmetric bridge function theory is adopted to develop a bridge function related to asymmetric pressure and friction coefficient which can be described in a segmented manner, so that an integrated rapid calculation technology for aerodynamic characteristics of the low-orbit cross-flow zone is formed, and a specific construction method can refer to the document.
The pressure coefficient calculated by using the modified Newtonian non-viscous flow theory for the continuous flow region is as follows:
wherein、Andthe pressure, density and speed of the free incoming flow,is an angle of an object plane, and is a plane,at maximum surface pressureThe pressure coefficient of the post-shock stationary point is specifically calculated as follows:
whereinIn order to obtain a mach number of the incoming flow,is the specific heat ratio of the gas. The free molecular flow theory is adopted to control the highly thin flow region, a Nocilla wall reflection model corrected based on different model materials can be adopted to calculate the pressure coefficient and the friction coefficient, and the pressure of each surface element is calculated under the assumption of Maxwell equilibrium state gas distributionAnd coefficient of frictionComprises the following steps:
wherein the content of the first and second substances,in order to be an exponential function of the,、respectively the object plane and the incoming flow temperature,andnormal and tangential object plane momentum adaptation coefficients respectively,in order to be a function of the error,is the speed ratio, defined as:
whereinIs the universal gas constant. And smoothly overlapping the continuous flow coefficient and the free molecular flow coefficient in a transition flow region by adopting a semi-empirical local bridge function method, so that the continuous flow coefficient and the free molecular flow coefficient respectively approach to a flow function. At a given object plane angleWhen is coming into contact withThe pressure and friction coefficients on the surface elements are:
whereinAndpressure and friction bridge functions, respectively, dependent on independent parameters、And,knudsen number. The irregular object of the large uncontrolled spacecraft can be represented by a triangular unstructured grid surface element, the large uncontrolled spacecraft is subjected to object forming processing by adopting a general approximate surface element method, when the surface elements are divided into small enough, the normal force and tangential force integrals on all the surface elements are integrated along the whole object surface of the large uncontrolled spacecraft geometry, and therefore the error caused by the overall aerodynamic force coefficient is obtained to be smaller. And finally, a high-performance computer is fully utilized to develop DSMC and solve a Boltzmann model equation unified algorithm to carry out fine calculation on aerodynamic characteristics, so that a localized fast engineering algorithm suitable for the aerodynamic characteristics of the large uncontrolled spacecraft in a specific geometric configuration is determined by correction, and the corresponding aerodynamic coefficients of the large uncontrolled spacecraft under the conditions of different orbit heights and attack angles are obtained.
In addition, the attitude information of the large-scale uncontrolled spacecraft, including the angle of attack and the sideslip angle, needs to be synchronously calculated in real time by using the attitude dynamics model. The attack angle and the sideslip angle are included angles of a large-scale uncontrolled spacecraft projectile coordinate system relative to a speed coordinate system, and the attack angle and the sideslip angle can be obtained only by solving attitude angle changes of the large-scale uncontrolled spacecraft projectile coordinate system relative to an orbit coordinate system. The attitude angle is generally defined as the euler angle of the large uncontrolled spacecraft in rotation around the x, y and z axes, respectively:-a roll angle of the roll-off,-a pitch angle,-yaw angle.
In order to avoid the singularity of the solution, the attitude change of the large-scale uncontrolled spacecraft is described in a quaternion mode. The quaternion representation is directly related to the euler angle representation. The following four elements are defined:
wherein q is0、q1、q2、q3Four elements of a quaternion, q is a vector of three imaginary elements in the quaternion,the symbols are transposed for the matrix, n is the rotation axis, the first of the four elements in the quaternion represents the euler rotation angle, the last three represent the direction of the euler rotation axis. The four elements are combined in the following vector form:
it is clear that these four elements satisfy the normalization condition. According to the Euler rotation formula and the definition of quaternion, the attitude matrix represented by quaternion is:
wherein the content of the first and second substances,is a rotational inertia matrix of a large uncontrolled spacecraft,an augmentation matrix being a quaternion matrix q;
in order to establish the relationship between the instantaneous change rate of the attitude parameters and the rotation angular velocity, it is first required to solve the attitude kinematics equation. If the rotating speed of the attitude of the large uncontrolled spacecraft relative to the reference coordinate isThe rotating shaft isI.e. byIf at the momentAttitude matrix isIn aThe time attitude matrix isAnd then:
whereinTo around a rotating shaftIs rotated overThe angle rotation matrix applies the relation between the attitude quaternion and the direction cosine to obtain the change equation of the attitude quaternion, which is as follows:
wherein the content of the first and second substances,is the angular velocity of rotation of the spacecraft about the x-axis,is the angular velocity of the spacecraft about the y-axis,is the angular velocity of the spacecraft about the z-axis,、、andthe differential quantities are corresponding to four elements of a quaternion.
The attitude kinematics equation resulting in the quaternion description is as follows:
wherein the content of the first and second substances,is the differential quantity of the attitude quaternion,is the quaternion of the attitude,for the cross-product sign of the vector matrix,representing the angular velocity of the extended projectile coordinate system relative to the orbital coordinate system and the inertial angular velocity of the projectileThe relationship of (a) to (b) is as follows:
in the formulaA pose matrix of the projectile coordinate system to the orbit coordinate system described by a quaternion,is the track angular velocity.
On the basis of the attitude kinematics equation, an attitude kinematics equation can be further established for solving the attitude angle in an integral mode. Considering the attitude angle change of the large-scale uncontrolled spacecraft under the action of the perturbation moments such as the aerodynamic disturbance moment geocentric non-spherical gravitation and the like, an attitude dynamics equation is established as follows:
whereinIs a rotational inertia matrix of a large uncontrolled spacecraft,an item is generally denoted asBy angular velocityOf the representationComprises the following steps:
the state equation of the attitude motion of the large-scale uncontrolled spacecraft can be expressed by combining an attitude kinematics equation as follows:
To the right of equation (20)For the aerodynamic disturbance torque, the aerodynamic disturbance torque model can be expressed as:
whereinIs the radius of the mass center of the aerodynamic pressure center relative to the large-scale uncontrolled spacecraft,the aerodynamic force of a large uncontrolled spacecraft is expressed as follows:
whereinIn order to obtain the coefficient of aerodynamic drag,is the average atmospheric density of the height of the large uncontrolled spacecraft,is a characteristic area of a large uncontrolled spacecraft,the speed of the large uncontrolled spacecraft relative to the atmosphere.
And (3) calculating the result according to the localization rapid engineering algorithm in the step 2: roll moment coefficient ofCoefficient of pitching moment ofYaw moment coefficient ofThe characteristic length of the large-scale uncontrolled spacecraft isThen the aerodynamic moment at the three-axis component of the projectile coordinate is:
to the right of equation (20)The gravity gradient moment is generated by different gravitations of the earth to parts of the large-scale uncontrolled spacecraft.
Converting the attitude angle obtained by solving the attitude dynamics equation into an airflow coordinate system to obtain an attack angle and a sideslip angle through conversion, converting the height and the velocity vector of the orbit by using the position and the velocity obtained by solving the equation (1), calling the pneumatic localization fast engineering algorithm of the step 2, and obtaining the corresponding pneumatic resistance coefficient under the conditions of corresponding orbit height and attack angle through integral equations (9) and (10)。
The aerodynamic drag coefficient is obtained by calculation based on a refined aerodynamic localization quick engineering algorithm and by considering the attitude rotation effectCalculating and updating the ballistic coefficient in equation (3)And calculating a resistance term in the two-line root of the TLE according to equation (2)Meanwhile, the position and speed calculation of the next moment is carried out by combining the SGP4 model, and the solution is iterated in sequence until the given reentry is reachedAnd (4) outputting the time, the position and the speed information corresponding to the reentry altitude and the previously experienced orbit ephemeris data to complete the on-orbit prediction and the reentry prediction of the large-scale uncontrolled spacecraft.
The method established by the invention is used for carrying out orbit perturbation analysis and on-orbit flight and reentry forecast on the similar Tiangong I, the given reentry height is 120km, the initial time is 3 months in 2018, 18 months in 2018, 12 days in 18 months, 16 minutes and 1 second, the obtained specific position, speed and attitude information is shown in table 2, and the reentry forecast information is as follows:
reentry time (year, month, day, hour, minute, second):
2018 4 3 19 54 1。
then enter longitude, latitude, altitude (°, km):
-144.76 16.18 119.95。
while preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (9)
1. A perturbation analysis method for a spacecraft aerodynamic fusion orbit is characterized by comprising the following steps:
step 1: generating first two-row root orbit root information of a spacecraft based on ephemeris data and instantaneous orbit root information in observation data corresponding to the initial moment of the spacecraft;
step 2: calculating to obtain the initial orbit height and the initial velocity vector of the spacecraft based on the state variable of the first two-row root orbit root information of the spacecraft; establishing a coordinate rotation matrix for describing the attitude change of the spacecraft based on the initial attitude observation data of the spacecraft, and converting the initial attitude observation data according to the coordinate rotation matrix to obtain an initial attack angle and an initial sideslip angle;
and step 3: calculating and obtaining an initial aerodynamic drag coefficient and an initial aerodynamic disturbance moment coefficient of the spacecraft based on the initial orbit altitude, the initial velocity vector, the initial angle of attack and the initial sideslip angle;
and 4, step 4: calculating to obtain a ballistic coefficient based on the initial aerodynamic resistance coefficient and the surface-to-mass ratio of the spacecraft, and replacing a resistance item in the first two-row radical orbit radical information by using the ballistic coefficient to obtain second two-row radical orbit radical information;
and 5: performing track root information extrapolation calculation based on the second two-line root track root information and the track forecasting model to obtain the track height and the velocity vector of the spacecraft corresponding to the next moment; if the orbit altitude obtained in the step 5 reaches the reentry orbit altitude, outputting ephemeris data and orbit information of the spacecraft corresponding to the next moment; if the height of the track obtained in the step 5 does not reach the height of the reentry track, executing a step 6;
step 6: calculating attitude angle data corresponding to the spacecraft at the next moment by using a state equation of the spacecraft based on the initial attitude observation data and the initial aerodynamic disturbance moment coefficient, and converting the attitude angle data according to the coordinate rotation matrix to obtain an attack angle and a sideslip angle corresponding to the next moment;
and 7: and substituting the orbit altitude, the velocity vector and the attack angle and the sideslip angle obtained in the step 5 and obtained in the step 6 into the step 3 to calculate and obtain the aerodynamic resistance coefficient and the aerodynamic disturbance moment coefficient of the spacecraft corresponding to the next moment, and continuing to iteratively execute the steps 4 to 7 based on the aerodynamic resistance coefficient and the aerodynamic disturbance moment coefficient of the spacecraft corresponding to the next moment until the orbit altitude obtained in the step 5 reaches the re-entering orbit altitude.
2. The perturbation analysis method for the spacecraft aerodynamic fusion orbit according to claim 1, wherein the step 1 specifically comprises: acquiring observation data corresponding to the initial time of the spacecraft in a J2000 geocentric inertial coordinate system, and generating the first two-row root orbit root information in a TEME instant true equator spring deciduous point coordinate system based on ephemeris data and instant orbit root information in the observation data.
3. A spacecraft aerodynamic fusion orbit perturbation analysis method according to claim 1, wherein the orbit prediction model is an SGP4 model.
4. A spacecraft aerodynamic fusion orbit perturbation analysis method according to claim 1, wherein the state variables of two rows of root orbit root information are expressed as:
wherein the content of the first and second substances,as a matter of time, the time is,the average number of tracks in the form of a two-row number,is time of dayIncluding position and velocity,for SGP4 model function, initial timeCorresponding variableThe average number of tracks in the form of a two-row number,including eccentricityInclination of the trackThe right ascension channelArgument of near placeFlat near point angleAnd average angular velocity;
Resistance term in two rows of radicalsFor normalized atmospheric drag coefficients, the form is calculated as:
5. A spacecraft aerodynamic fusion orbit perturbation analysis method according to claim 1, wherein aerodynamic drag coefficientThe calculation method is as follows:
6. The method for analyzing perturbation of a spacecraft aerodynamic fusion orbit according to claim 1, wherein a coordinate rotation matrix describing changes of the spacecraft attitude is established based on initial attitude observation data of the spacecraft, and the initial attitude observation data is converted according to the coordinate rotation matrix to obtain an initial attack angle and an initial sideslip angle, and specifically comprises:
step a: calculating to obtain initial attitude angle data of the spacecraft based on the initial attitude observation data of the spacecraft;
step b: describing the initial attitude angle data in a quaternion form, and establishing a coordinate rotation matrix for describing attitude change;
step c: and converting the initial attitude angle data of the spacecraft into an airflow coordinate system to convert the initial attitude angle data and the coordinate rotation matrix to obtain an initial attack angle and an initial sideslip angle.
7. A perturbation analysis method for a spacecraft aerodynamic fusion orbit according to claim 6, wherein the state equation of the spacecraft in the step 6 is obtained by combining an attitude kinematics equation of the spacecraft and an attitude dynamics equation of the spacecraft;
describing the attitude change of the spacecraft in a quaternion mode, wherein the attitude kinematic equation of the spacecraft described by the quaternion is obtained by the following steps:
wherein the content of the first and second substances,is the differential quantity of the attitude quaternion,is the quaternion of the attitude,for the cross-product sign of the vector matrix,representing the angular velocity of the extended projectile coordinate system relative to the orbital coordinate system and the inertial angular velocity of the projectileThe relationship of (1) is:
wherein the content of the first and second substances,the rotating angular velocity of the spacecraft projectile system,the symbols are transposed for the matrix,a pose matrix of the projectile coordinate system to the orbit coordinate system described by a quaternion,is the track angular velocity;
the attitude dynamics equation of the spacecraft is as follows:
wherein the content of the first and second substances,is a matrix of the moment of inertia of the spacecraft,is the angular velocity vector of the rotation of the spacecraft,is the differential quantity of the rotation angular velocity vector of the spacecraft,in order to be a gravity gradient moment,is a pneumatic disturbance moment;is marked as,Is gyro moment;
the state equation of the spacecraft is expressed as:
whereinIn order to be a state variable, the state variable,is a generalized matrix of quaternion differential quantities,,is the angular velocity of rotation of the spacecraft about the x-axis,is the differential quantity of the rotation angular velocity of the spacecraft around the x-axis,is the angular velocity of the spacecraft about the y-axis,is the differential quantity of the rotation angular velocity of the spacecraft around the y-axis,is the angular velocity of the spacecraft about the z-axis,is a differential quantity of the rotation angular velocity of the spacecraft around the z-axis,、、andthe differential quantities are respectively corresponding to four elements of a quaternion;
and integrating the state variable by using the state equation of the spacecraft to obtain the attitude angle data of the spacecraft at the required moment.
8. A spacecraft aerodynamic fusion orbit perturbation analysis method according to claim 7, wherein the aerodynamic disturbance torqueThe method comprises the following steps:、and,、andthe calculation method is as follows:
wherein the roll moment coefficient isCoefficient of pitching moment ofYaw moment coefficient ofThe characteristic length of the spacecraft is,In order to be a gravity gradient moment,for aerodynamic disturbance moments on the x-axis,for the aerodynamic disturbance moment on the y-axis,for aerodynamic disturbance moments in the z-axis,is the average atmospheric density at the altitude where the spacecraft is located,is the characteristic area of the spacecraft,is the velocity of the spacecraft relative to the atmosphere.
9. A spacecraft aerodynamic fusion orbit perturbation analysis method according to claim 7, wherein aerodynamic disturbance torqueThe calculation method is as follows:
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