agi.foundation.celestial

(agi.foundation.orbitpropagation-2024r2.jar)

Class NPlateAtmosphericDragForce

java.lang.Object

agi.foundation.infrastructure.DefinitionalObject

agi.foundation.celestial.ForceModel

agi.foundation.celestial.NPlateAtmosphericDragForce

All Implemented Interfaces:

ICloneWithContext, IEnumerateDependencies, IEquatableDefinition, IFreezable

public class NPlateAtmosphericDragForce
extends ForceModel

A medium-fidelity force model for atmospheric drag on a spacecraft. The model requires that a spacecraft's attitude be specified by its BodyAxes (get / set), the spacecraft's body and solar panels be modeled by an NPlateModel (get / set) that contains a model for each outward facing surface of the spacecraft, and the atmospheric density is modeled by a density model.

This model does not take into account the effect of plates physically blocking other plates from experiencing drag if the blocked plates are behind them but pointing in the same direction.

Constructor Summary

Constructors

Modifier	Constructor and Description
	NPlateAtmosphericDragForce() Initializes a ForceModel describing the atmospheric drag force on an object.
protected	NPlateAtmosphericDragForce(NPlateAtmosphericDragForce existingInstance, CopyContext context)
	NPlateAtmosphericDragForce(NPlateModel nPlateModel, Axes bodyAxes, ScalarAtmosphericDensity density, CentralBody illuminatingBody) Initializes a ForceModel describing the atmospheric drag force on an object.

Method Summary

Modifier and Type	Method and Description
void	buildForceEvaluator(ResultantForceBuilder builder, EvaluatorGroup group) Build lists of principal and perturbation forces based on this model in order to create an overall resultant force.
protected boolean	checkForSameDefinition(ForceModel other) Checks to determine if another instance has the same definition as this instance and returns true if it does.
protected boolean	checkForSameDefinition(NPlateAtmosphericDragForce other) Checks to determine if another instance has the same definition as this instance and returns true if it does.
Object	clone(CopyContext context) Clones this object using the specified context.
protected int	computeCurrentDefinitionHashCode() Computes a hash code based on the current properties of this object.
void	enumerateDependencies(DependencyEnumerator enumerator) Enumerates the dependencies of this object by calling DependencyEnumerator#enumerate(T) for each object that this object directly depends upon.
Axes	getBodyAxes() Gets the axes defining the orientation of the spacecraft body.
Axes	getDefinedInAxes() Gets the Axes in which this force is defined.
ScalarAtmosphericDensity	getDensity() Gets the atmospheric model used to calculate density at the location of the TargetPoint (get / set).
CentralBody	getIlluminatingBody() Gets the body that is used to determine the direction that solar panel plates face (typically, the Sun).
NPlateModel	getNPlateModel() Gets a collection that models the spacecraft's body as a collection of individual plates with oriented surface areas and drag coefficients.
Point	getTargetPoint() Gets the point at which the drag is applied from the TargetPoint (get / set) of the Density (get / set).
void	setBodyAxes(Axes value) Sets the axes defining the orientation of the spacecraft body.
void	setDensity(ScalarAtmosphericDensity value) Sets the atmospheric model used to calculate density at the location of the TargetPoint (get / set).
void	setIlluminatingBody(CentralBody value) Sets the body that is used to determine the direction that solar panel plates face (typically, the Sun).
void	setNPlateModel(NPlateModel value) Sets a collection that models the spacecraft's body as a collection of individual plates with oriented surface areas and drag coefficients.

Methods inherited from class agi.foundation.celestial.ForceModel

checkForSameDefinition, freezeAggregatedObjects, getForceEvaluator, getForceEvaluator, getForceVector, getKind, getRole

Methods inherited from class agi.foundation.infrastructure.DefinitionalObject

areSameDefinition, areSameDefinition, areSameDefinition, areSameDefinition, areSameDefinition, collectionItemsAreSameDefinition, collectionItemsAreSameDefinition, collectionItemsAreSameDefinition, dictionaryItemsAreSameDefinition, freeze, getCollectionHashCode, getCollectionHashCode, getCollectionHashCode, getDefinitionHashCode, getDefinitionHashCode, getDefinitionHashCode, getDefinitionHashCode, getDefinitionHashCode, getDefinitionHashCode, getDictionaryHashCode, getIsFrozen, isSameDefinition, throwIfFrozen

Methods inherited from class java.lang.Object

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

Constructor Detail

NPlateAtmosphericDragForce

public NPlateAtmosphericDragForce()

Initializes a ForceModel describing the atmospheric drag force on an object.

The NPlateModel (get / set), BodyAxes (get / set), Density (get / set), and IlluminatingBody (get / set) properties must be set before creating an evaluator.

NPlateAtmosphericDragForce

public NPlateAtmosphericDragForce(NPlateModel nPlateModel,
                                  Axes bodyAxes,
                                  ScalarAtmosphericDensity density,
                                  CentralBody illuminatingBody)

Initializes a ForceModel describing the atmospheric drag force on an object.

Parameters:

nPlateModel - A collection that models the spacecraft's body as individual plates with oriented surface areas and drag coefficients.

bodyAxes - The axes defining the orientation of the spacecraft body.

density - The atmospheric model used to calculate density.

illuminatingBody - The body that is used to determine the direction that solar panel plates face (typically, the Sun).

NPlateAtmosphericDragForce

protected NPlateAtmosphericDragForce(@Nonnull
                                     NPlateAtmosphericDragForce existingInstance,
                                     @Nonnull
                                     CopyContext context)

Method Detail

clone

public Object clone(CopyContext context)

Clones this object using the specified context.

This method should be implemented to call a copy constructor on the class of the object being cloned. The copy constructor should take the CopyContext as a parameter in addition to the existing instance to copy. The copy constructor should first call CopyContext.addObjectMapping(T, T) to identify the newly constructed instance as a copy of the existing instance. It should then copy all fields, using CopyContext.updateReference(T) to copy any reference fields.

A typical implementation of ICloneWithContext:

public static class MyClass implements ICloneWithContext {
    public MyClass(MyClass existingInstance, CopyContext context) {
        context.addObjectMapping(existingInstance, this);
        someReference = context.updateReference(existingInstance.someReference);
    }

    @Override
    public final Object clone(CopyContext context) {
        return new MyClass(this, context);
    }

    private Object someReference;
}

In general, all fields that are reference types should be copied with a call to CopyContext.updateReference(T). There are a couple of exceptions:

1. Fields that are aggregate parts of the object should always be copied. A referenced object is an aggregate if properties or methods on the object being copied can modify the externally-visible value of the referenced object.
2. If the semantics of the referenced object require that it have a single parent, owner, context, etc., and the object being copied is that parent, owner, or context, then the referenced object should always be copied.

If one of these exceptions applies, the CopyContext should be given an opportunity to update the reference before the reference is copied explicitly. Use CopyContext.updateReference(T) to update the reference. If CopyContext.updateReference(T) returns the original object, indicating that the context does not have a replacement registered, then copy the object manually by invoking a Clone method, a copy constructor, or by manually constructing a new instance and copying the values.

alwaysCopy = context.updateReference(existingInstance.alwaysCopy);
if (existingInstance.alwaysCopy != null && alwaysCopy == existingInstance.alwaysCopy) {
    alwaysCopy = (AlwaysCopy) existingInstance.alwaysCopy.clone(context);
}

If you are implementing an evaluator (a class that implements IEvaluator), the IEvaluator.updateEvaluatorReferences(agi.foundation.infrastructure.CopyContext) method shares some responsibilities with the copy context constructor. Code duplication can be avoided by doing the following:

1. For references to other evaluators ONLY, simply assign the reference in the constructor instead of calling CopyContext.updateReference(T). You should still call CopyContext.updateReference(T) on any references to non-evaluators.
2. Call IEvaluator.updateEvaluatorReferences(agi.foundation.infrastructure.CopyContext) as the last line in the constructor and pass it the same CopyContext passed to the constructor.
3. Implement IEvaluator.updateEvaluatorReferences(agi.foundation.infrastructure.CopyContext) as normal. See the reference documentation for IEvaluator.updateEvaluatorReferences(agi.foundation.infrastructure.CopyContext) for more information on implementing that method.

public MyClass(MyClass existingInstance, CopyContext context) {
    super(existingInstance, context);
    someReference = context.updateReference(existingInstance.someReference);
    evaluatorReference = existingInstance.evaluatorReference;
    updateEvaluatorReferences(context);
}

@Override
public void updateEvaluatorReferences(CopyContext context) {
    evaluatorReference = context.updateReference(evaluatorReference);
}

@Override
public Object clone(CopyContext context) {
    return new MyClass(this, context);
}

private Object someReference;
private IEvaluator evaluatorReference;

Specified by:

clone in interface ICloneWithContext

Specified by:

clone in class DefinitionalObject

Parameters:

context - The context to use to perform the copy.

Returns:

A new instance which is a copy of this object.

checkForSameDefinition

protected final boolean checkForSameDefinition(ForceModel other)

Checks to determine if another instance has the same definition as this instance and returns true if it does. Derived classes MUST override this method and check all new fields introduced by the derived class for definitional equivalence. It is NOT necessary to check base class fields because the base class will already have done that. When overriding this method, you should NOT call the base implementation because it will return false for all derived-class instances. Derived classes should check the type of other to preserve the symmetric nature of IEquatableDefinition.isSameDefinition(java.lang.Object).

Specified by:

checkForSameDefinition in class ForceModel

Parameters:

other - The other instance to compare to this one.

Returns:

true if the two objects are defined equivalently; otherwise false.

checkForSameDefinition

protected boolean checkForSameDefinition(NPlateAtmosphericDragForce other)

Checks to determine if another instance has the same definition as this instance and returns true if it does. Derived classes MUST override this method and check all new fields introduced by the derived class for definitional equivalence. It is NOT necessary to check base class fields because the base class will already have done that. When overriding this method, you should NOT call the base implementation because it will return false for all derived-class instances. Derived classes should check the type of other to preserve the symmetric nature of IEquatableDefinition.isSameDefinition(java.lang.Object).

Parameters:

other - The other instance to compare to this one.

Returns:

true if the two objects are defined equivalently; otherwise false.

computeCurrentDefinitionHashCode

protected int computeCurrentDefinitionHashCode()

Computes a hash code based on the current properties of this object. Derived classes MUST override this method and compute a hash code that combines: a unique hash code seed, the base implementation result, and the hash codes of all new fields introduced by the derived class which are used in the NPlateAtmosphericDragForce.checkForSameDefinition(agi.foundation.celestial.ForceModel) method.

Overrides:

computeCurrentDefinitionHashCode in class ForceModel

Returns:

The computed hash code.

enumerateDependencies

public void enumerateDependencies(DependencyEnumerator enumerator)

Enumerates the dependencies of this object by calling DependencyEnumerator#enumerate(T) for each object that this object directly depends upon. Derived classes which contain additional dependencies MUST override this method, call the base implementation, and enumerate dependencies introduced by the derived class.

Specified by:

enumerateDependencies in interface IEnumerateDependencies

Overrides:

enumerateDependencies in class ForceModel

Parameters:

enumerator - The enumerator that is informed of the dependencies of this object.

getDensity

public final ScalarAtmosphericDensity getDensity()

Gets the atmospheric model used to calculate density at the location of the TargetPoint (get / set).

setDensity

public final void setDensity(ScalarAtmosphericDensity value)

Sets the atmospheric model used to calculate density at the location of the TargetPoint (get / set).

getTargetPoint

@Nullable
public final Point getTargetPoint()

Gets the point at which the drag is applied from the TargetPoint (get / set) of the Density (get / set). If the Density (get / set) property is null, then this property will also return null.

getDefinedInAxes

@Nullable
public final Axes getDefinedInAxes()

Gets the Axes in which this force is defined. For drag, the Axes are taken from the fixed frame of the CentralBody used for the Density (get / set). Also note that while the drag force is defined in the fixed frame, forces are considered to be "inertial" for the purposes of Newtonian kinematics, and no kinematic transformation apart from a simple rotation is necessary when converting to an inertial frame. If the Density (get / set) property is null, then this property will also return null.

getNPlateModel

public final NPlateModel getNPlateModel()

Gets a collection that models the spacecraft's body as a collection of individual plates with oriented surface areas and drag coefficients. All plates in this collection must be DragPlates.

setNPlateModel

public final void setNPlateModel(NPlateModel value)

Sets a collection that models the spacecraft's body as a collection of individual plates with oriented surface areas and drag coefficients. All plates in this collection must be DragPlates.

getBodyAxes

public final Axes getBodyAxes()

Gets the axes defining the orientation of the spacecraft body.

setBodyAxes

public final void setBodyAxes(Axes value)

Sets the axes defining the orientation of the spacecraft body.

getIlluminatingBody

public final CentralBody getIlluminatingBody()

Gets the body that is used to determine the direction that solar panel plates face (typically, the Sun).

setIlluminatingBody

public final void setIlluminatingBody(CentralBody value)

Sets the body that is used to determine the direction that solar panel plates face (typically, the Sun).

buildForceEvaluator

public void buildForceEvaluator(ResultantForceBuilder builder,
                                EvaluatorGroup group)

Build lists of principal and perturbation forces based on this model in order to create an overall resultant force.

Specified by:

buildForceEvaluator in class ForceModel

Parameters:

builder - The builder object containing the lists and additional information on the Axes in which the overall resultant is defined.

group - The evaluator group in which to create evaluators.

Throws:

PropertyInvalidException - Thrown when Density (get / set), IlluminatingBody (get / set), or BodyAxes (get / set) is null. Also, thrown if NPlateModel (get / set) is null, empty, or contains plates that are not DragPlates.