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

  • Method Details

    • 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

    • getMassDerivative

      default double getMassDerivative(SpacecraftState state, double[] parameters)
      Compute the mass rate. Zero by default.
      Parameters:
      state - current state information: date, kinematics, attitude
      parameters - values of the force model parameters at state date
      Returns:
      mass rate (kg/s)
      Since:
      13.1

    • getMassDerivative

      default <T extends CalculusFieldElement<T>> T getMassDerivative(FieldSpacecraftState<T> state, T[] parameters)
      Compute the mass rate. Zero by default.
      Type Parameters:
      T - field type
      Parameters:
      state - current state information: date, kinematics, attitude
      parameters - values of the force model parameters at state date
      Returns:
      mass rate (kg/s)
      Since:
      13.1

    • 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 mass or 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