Package org.orekit.forces

Interface ForceModel

All Superinterfaces:

EventDetectorsProvider, ParameterDriversProvider

All Known Subinterfaces:

ForceModelModifier, RadiationForceModel

All Known Implementing Classes:

AbstractBodyAttraction, AbstractDragForceModel, AbstractParametricAcceleration, AbstractRadiationForceModel, ConstantThrustManeuver, CR3BPForceModel, DeSitterRelativity, DragForce, ECOM2, HolmesFeatherstoneAttractionModel, InertialForces, J2OnlyPerturbation, KnockeRediffusedForceModel, LenseThirringRelativity, Maneuver, NewtonianAttraction, OceanTides, ParametricAcceleration, RadiationPressureModel, Relativity, SingleBodyAbsoluteAttraction, SingleBodyRelativeAttraction, SolarRadiationPressure, SolidTides, ThirdBodyAttraction, ThirdBodyAttractionEpoch, TimeSpanDragForce, TimeSpanParametricAcceleration

public interface ForceModel
extends ParameterDriversProvider, EventDetectorsProvider

This interface represents a force modifying spacecraft motion.

Objects implementing this interface are intended to be added to a numerical propagator before the propagation is started.

The propagator will call at each step the addContribution(SpacecraftState, TimeDerivativesEquations) method. The force model instance will extract all the state data it needs (date, position, velocity, frame, attitude, mass) from the first parameter. From these state data, it will compute the perturbing acceleration. It will then add this acceleration to the second parameter which will take thins contribution into account and will use the Gauss equations to evaluate its impact on the global state derivative.

Force models which create discontinuous acceleration patterns (typically for maneuvers start/stop or solar eclipses entry/exit) must provide one or more events detectors to the propagator thanks to their getEventDetectors() method. This method is called once just before propagation starts. The events states will be checked by the propagator to ensure accurate propagation and proper events handling.

Author:

Mathieu Roméro, Luc Maisonobe, Véronique Pommier-Maurussane, Melina Vanel

Field Summary

Fields inherited from interface org.orekit.propagation.events.EventDetectorsProvider

DATATION_ACCURACY

Method Summary

Modifier and Type	Method	Description
<T extends CalculusFieldElement<T>> FieldVector3D<T>	acceleration(FieldSpacecraftState<T> s, T[] parameters)	Compute acceleration.
Vector3D	acceleration(SpacecraftState s, double[] parameters)	Compute acceleration.
default <T extends CalculusFieldElement<T>> void	addContribution(FieldSpacecraftState<T> s, FieldTimeDerivativesEquations<T> adder)	Compute the contribution of the force model to the perturbing acceleration.
default void	addContribution(SpacecraftState s, TimeDerivativesEquations adder)	Compute the contribution of the force model to the perturbing acceleration.
default boolean	dependsOnAttitudeRate()	Check if force model depends on attitude's rotation rate or acceleration at a given, fixed date.
boolean	dependsOnPositionOnly()	Check if force model depends on position only at a given, fixed date.
default Stream<EventDetector>	getEventDetectors()	Get the discrete events related to the model.
default <T extends CalculusFieldElement<T>> Stream<FieldEventDetector<T>>	getFieldEventDetectors(Field<T> field)	Get the discrete events related to the model.
default <T extends CalculusFieldElement<T>> void	init(FieldSpacecraftState<T> initialState, FieldAbsoluteDate<T> target)	Initialize the force model at the start of propagation.
default void	init(SpacecraftState initialState, AbsoluteDate target)	Initialize the force model at the start of propagation.

Methods inherited from interface org.orekit.propagation.events.EventDetectorsProvider

getDateDetector, getEventDetectors, getFieldDateDetector, getFieldEventDetectors

Methods inherited from interface org.orekit.utils.ParameterDriversProvider

getNbParametersDriversValue, getParameterDriver, getParameters, getParameters, getParameters, getParameters, getParametersAllValues, getParametersAllValues, getParametersDrivers, isSupported

Method Detail

init

default void init(SpacecraftState initialState,
                  AbsoluteDate target)

Initialize the force model at the start of propagation. This method will be called before any calls to addContribution(SpacecraftState, TimeDerivativesEquations), addContribution(FieldSpacecraftState, FieldTimeDerivativesEquations), acceleration(SpacecraftState, double[]) or acceleration(FieldSpacecraftState, CalculusFieldElement[])

The default implementation of this method does nothing.

Parameters:

initialState - spacecraft state at the start of propagation.

target - date of propagation. Not equal to initialState.getDate().

init

default <T extends CalculusFieldElement<T>> void init(FieldSpacecraftState<T> initialState,
                                                      FieldAbsoluteDate<T> target)

Initialize the force model at the start of propagation. This method will be called before any calls to addContribution(SpacecraftState, TimeDerivativesEquations), addContribution(FieldSpacecraftState, FieldTimeDerivativesEquations), acceleration(SpacecraftState, double[]) or acceleration(FieldSpacecraftState, CalculusFieldElement[])

The default implementation of this method does nothing.

Type Parameters:

T - type of the elements

Parameters:

initialState - spacecraft state at the start of propagation.

target - date of propagation. Not equal to initialState.getDate().

getEventDetectors

default Stream<EventDetector> getEventDetectors()

Get the discrete events related to the model.

This method is not intended to be called several time, only once by a propagator, as it has the side effect of rebuilding the events detectors when called.

Specified by:

getEventDetectors in interface EventDetectorsProvider

Returns:

stream of event detectors

getFieldEventDetectors

default <T extends CalculusFieldElement<T>> Stream<FieldEventDetector<T>> getFieldEventDetectors(Field<T> field)

Get the discrete events related to the model.

This method is not intended to be called several time, only once by a propagator, as it has the side effect of rebuilding the events detectors when called.

Specified by:

getFieldEventDetectors in interface EventDetectorsProvider

Type Parameters:

T - extends CalculusFieldElement<T>

Parameters:

field - field to which the state belongs

Returns:

stream of event detectors

addContribution

default void addContribution(SpacecraftState s,
                             TimeDerivativesEquations adder)

Compute the contribution of the force model to the perturbing acceleration.

The default implementation simply adds the acceleration as a non-Keplerian acceleration.

Parameters:

s - current state information: date, kinematics, attitude

adder - object where the contribution should be added

addContribution

default <T extends CalculusFieldElement<T>> void addContribution(FieldSpacecraftState<T> s,
                                                                 FieldTimeDerivativesEquations<T> adder)

Compute the contribution of the force model to the perturbing acceleration.

Type Parameters:

T - type of the elements

Parameters:

s - current state information: date, kinematics, attitude

adder - object where the contribution should be added

dependsOnPositionOnly

boolean dependsOnPositionOnly()

Check if force model depends on position only at a given, fixed date.

Returns:

true if force model depends on position only, false if it depends on velocity, either directly or due to a dependency on attitude

Since:

9.0

dependsOnAttitudeRate

default boolean dependsOnAttitudeRate()

Check if force model depends on attitude's rotation rate or acceleration at a given, fixed date. If false, it essentially means that at most the attitude's rotation is used when computing the acceleration vector. The default implementation returns false as common forces do not.

Returns:

true if force model depends on attitude derivatives

Since:

12.1

acceleration

Vector3D acceleration(SpacecraftState s,
                      double[] parameters)

Compute acceleration.

Parameters:

s - current state information: date, kinematics, attitude

parameters - values of the force model parameters at state date, only 1 value for each parameterDriver

Returns:

acceleration in same frame as state

Since:

9.0

acceleration

<T extends CalculusFieldElement<T>> FieldVector3D<T> acceleration(FieldSpacecraftState<T> s,
                                                                  T[] parameters)

Compute acceleration.

Type Parameters:

T - type of the elements

Parameters:

s - current state information: date, kinematics, attitude

parameters - values of the force model parameters at state date, only 1 value for each parameterDriver

Returns:

acceleration in same frame as state

Since:

9.0