Package org.orekit.forces.drag

Class AbstractDragForceModel

java.lang.Object

org.orekit.forces.drag.AbstractDragForceModel

All Implemented Interfaces:

ForceModel, EventDetectorsProvider, ParameterDriversProvider

Direct Known Subclasses:

DragForce, TimeSpanDragForce

public abstract class AbstractDragForceModel
extends Object
implements ForceModel

Base class for drag force models.

Since:

10.2

Author:

Bryan Cazabonne

See Also:

DragForce, TimeSpanDragForce

Field Summary

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

DATATION_ACCURACY

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	AbstractDragForceModel(Atmosphere atmosphere)	Constructor.

Method Summary

Modifier and Type	Method	Description
boolean	dependsOnPositionOnly()	Check if force models depends on position only.
protected DerivativeStructure	getDSDensityWrtStateUsingFiniteDifferences(AbsoluteDate date, Frame frame, FieldVector3D<DerivativeStructure> position)	Compute density and its derivatives.
protected Gradient	getGradientDensityWrtStateUsingFiniteDifferences(AbsoluteDate date, Frame frame, FieldVector3D<Gradient> position)	Compute density and its derivatives.
protected <T extends CalculusFieldElement<T>> boolean	isDSStateDerivative(FieldSpacecraftState<T> state)	Check if a field state corresponds to derivatives with respect to state.
protected <T extends CalculusFieldElement<T>> boolean	isGradientStateDerivative(FieldSpacecraftState<T> state)	Check if a field state corresponds to derivatives with respect to state.
protected boolean	isVariable(DerivativeStructure ds, int index)	Check if a derivative represents a specified variable.
protected boolean	isVariable(Gradient g, int index)	Check if a derivative represents a specified variable.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

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

getEventDetectors, getFieldEventDetectors

Methods inherited from interface org.orekit.forces.ForceModel

acceleration, acceleration, addContribution, addContribution, getEventDetectors, getFieldEventDetectors, init, init

Methods inherited from interface org.orekit.utils.ParameterDriversProvider

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

Constructor Detail

AbstractDragForceModel

protected AbstractDragForceModel(Atmosphere atmosphere)

Constructor.

Parameters:

atmosphere - atmospheric model

Method Detail

dependsOnPositionOnly

public boolean dependsOnPositionOnly()

Check if force models depends on position only.

Specified by:

dependsOnPositionOnly in interface ForceModel

Returns:

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

isDSStateDerivative

protected <T extends CalculusFieldElement<T>> boolean isDSStateDerivative(FieldSpacecraftState<T> state)

Check if a field state corresponds to derivatives with respect to state.

Type Parameters:

T - type of the field elements

Parameters:

state - state to check

Returns:

true if state corresponds to derivatives with respect to state

isGradientStateDerivative

protected <T extends CalculusFieldElement<T>> boolean isGradientStateDerivative(FieldSpacecraftState<T> state)

Check if a field state corresponds to derivatives with respect to state.

Type Parameters:

T - type of the field elements

Parameters:

state - state to check

Returns:

true if state corresponds to derivatives with respect to state

isVariable

protected boolean isVariable(DerivativeStructure ds,
                             int index)

Check if a derivative represents a specified variable.

Parameters:

ds - derivative to check

index - index of the variable

Returns:

true if the derivative represents a specified variable

isVariable

protected boolean isVariable(Gradient g,
                             int index)

Check if a derivative represents a specified variable.

Parameters:

g - derivative to check

index - index of the variable

Returns:

true if the derivative represents a specified variable

getDSDensityWrtStateUsingFiniteDifferences

protected DerivativeStructure getDSDensityWrtStateUsingFiniteDifferences(AbsoluteDate date,
                                                                         Frame frame,
                                                                         FieldVector3D<DerivativeStructure> position)

Compute density and its derivatives. Using finite differences for the derivatives. And doing the actual computation only for the derivatives with respect to position (others are set to 0.).

From a theoretical point of view, this method computes the same values as Atmosphere.getDensity(FieldAbsoluteDate, FieldVector3D, Frame) in the specific case of DerivativeStructure with respect to state, so it is less general. However, it is *much* faster in this important case.

The derivatives should be computed with respect to position. The input parameters already take into account the free parameters (6, 7 or 8 depending on derivation with respect to drag coefficient and lift ratio being considered or not) and order (always 1). Free parameters at indices 0, 1 and 2 correspond to derivatives with respect to position. Free parameters at indices 3, 4 and 5 correspond to derivatives with respect to velocity (these derivatives will remain zero as the atmospheric density does not depend on velocity). Free parameter at indexes 6 and 7 (if present) corresponds to derivatives with respect to drag coefficient and/or lift ratio (one of these or both). This 2 last derivatives will remain zero as atmospheric density does not depend on them.

Parameters:

date - current date

frame - inertial reference frame for state (both orbit and attitude)

position - position of spacecraft in inertial frame

Returns:

the density and its derivatives

getGradientDensityWrtStateUsingFiniteDifferences

protected Gradient getGradientDensityWrtStateUsingFiniteDifferences(AbsoluteDate date,
                                                                    Frame frame,
                                                                    FieldVector3D<Gradient> position)

Compute density and its derivatives. Using finite differences for the derivatives. And doing the actual computation only for the derivatives with respect to position (others are set to 0.).

From a theoretical point of view, this method computes the same values as Atmosphere.getDensity(FieldAbsoluteDate, FieldVector3D, Frame) in the specific case of Gradient with respect to state, so it is less general. However, it is *much* faster in this important case.

The derivatives should be computed with respect to position. The input parameters already take into account the free parameters (6, 7 or 8 depending on derivation with respect to drag coefficient and lift ratio being considered or not) and order (always 1). Free parameters at indices 0, 1 and 2 correspond to derivatives with respect to position. Free parameters at indices 3, 4 and 5 correspond to derivatives with respect to velocity (these derivatives will remain zero as the atmospheric density does not depend on velocity). Free parameter at indexes 6 and 7 (if present) corresponds to derivatives with respect to drag coefficient and/or lift ratio (one of these or both). This 2 last derivatives will remain zero as atmospheric density does not depend on them.

Parameters:

date - current date

frame - inertial reference frame for state (both orbit and attitude)

position - position of spacecraft in inertial frame

Returns:

the density and its derivatives