org.orekit.forces.drag
Class DragForce

java.lang.Object
  org.orekit.parameter.Parameterizable
      org.orekit.parameter.JacobiansParameterizable
          org.orekit.forces.drag.DragForce

All Implemented Interfaces:

Serializable, ForceModel, GradientModel, IJacobiansParameterizable, IParameterizable

public class DragForce
extends JacobiansParameterizable
implements ForceModel, GradientModel

Atmospheric drag force model.

The drag acceleration is computed as follows : γ = (1/2 * k * ρ * V² * S / Mass) * DragCoefVector
With:

• DragCoefVector = {Cx, Cy, Cz} and S given by the user through the interface DragSensitive.
• k: user-added multiplicative coefficient to atmospheric drag. Partial derivatives wrt this coefficient can be computed.

The implementation of this class enables the computation of partial derivatives with respect to normal and tangential ballistic coefficients.

Author:

Édouard Delente, Fabien Maussion, Véronique Pommier-Maurussane, Pascal Parraud

See Also:

Serialized Form

Field Summary

static String

K_COEFFICIENT Parameter name for k coefficient.

Constructor Summary

DragForce(Atmosphere atmosphere, DragSensitive spacecraft)
Constructor with multiplicative factor k = 1.0.

DragForce(Atmosphere atmosphere, DragSensitive spacecraft, boolean computePDPos, boolean computePDVel)
Constructor with multiplicative factor k = 1.0.

DragForce(double k, Atmosphere atmosphere, DragSensitive spacecraft)
Constructor with multiplicative factor k.

DragForce(double k, Atmosphere atmosphere, DragSensitive spacecraft, boolean computePDPos, boolean computePDVel)
Constructor with multiplicative factor k.

DragForce(IParamDiffFunction k, Atmosphere atmosphere, DragSensitive spacecraft)
Constructor with multiplicative factor k.

DragForce(IParamDiffFunction k, Atmosphere atmosphere, DragSensitive spacecraft, boolean computePDPos, boolean computePDVel)
Constructor with multiplicative factor k.

DragForce(Parameter k, Atmosphere atmosphere, DragSensitive spacecraft)
Constructor with multiplicative factor k.

DragForce(Parameter k, Atmosphere atmosphere, DragSensitive spacecraft, boolean computePDPos, boolean computePDVel)
Constructor with multiplicative factor k.

Method Summary

void	addContribution(SpacecraftState s, TimeDerivativesEquations adder) Compute the contribution of the drag to the perturbing acceleration.
void	addDAccDParam(SpacecraftState s, Parameter param, double[] dAccdParam) Compute acceleration derivatives with respect to additional parameters.
void	addDAccDState(SpacecraftState s, double[][] dAccdPos, double[][] dAccdVel) Compute acceleration derivatives with respect to state parameters.
static Vector3D	computeAcceleration(PVCoordinates pv, Frame frame, Atmosphere atm, AbsoluteDate date, double kD, double mass) Method to compute the acceleration.
Vector3D	computeAcceleration(SpacecraftState s) Compute the acceleration due to the force.
boolean	computeGradientPosition() This method returns true if the acceleration partial derivatives with respect to position have to be computed.
boolean	computeGradientVelocity() This method returns true if the acceleration partial derivatives with respect to velocity have to be computed.
EventDetector[]	getEventsDetectors() There are no discrete events for this model.

Methods inherited from class org.orekit.parameter.JacobiansParameterizable

addJacobiansParameter, addJacobiansParameter, addJacobiansParameter, supportsJacobianParameter

Methods inherited from class org.orekit.parameter.Parameterizable

addParameter, getParameters, supportsParameter

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.orekit.parameter.IParameterizable

getParameters, supportsParameter

Field Detail

K_COEFFICIENT

public static final String K_COEFFICIENT

Parameter name for k coefficient.

See Also:

Constant Field Values

Constructor Detail

DragForce

public DragForce(Atmosphere atmosphere,
                 DragSensitive spacecraft)

Constructor with multiplicative factor k = 1.0.

Parameters:

atmosphere - atmospheric model

spacecraft - the object physical and geometrical information

DragForce

public DragForce(Atmosphere atmosphere,
                 DragSensitive spacecraft,
                 boolean computePDPos,
                 boolean computePDVel)

Constructor with multiplicative factor k = 1.0.

Parameters:

atmosphere - atmospheric model

spacecraft - the object physical and geometrical information

computePDPos - if partial derivatives wrt position have to be computed

computePDVel - if partial derivatives wrt velocity have to be computed

DragForce

public DragForce(double k,
                 Atmosphere atmosphere,
                 DragSensitive spacecraft)

Constructor with multiplicative factor k.

Parameters:

k - drag multiplicative factor

atmosphere - atmospheric model

spacecraft - the object physical and geometrical information

DragForce

public DragForce(double k,
                 Atmosphere atmosphere,
                 DragSensitive spacecraft,
                 boolean computePDPos,
                 boolean computePDVel)

Constructor with multiplicative factor k.

Parameters:

k - multiplicative factor

atmosphere - atmospheric model

spacecraft - the object physical and geometrical information

computePDPos - if partial derivatives wrt position have to be computed

computePDVel - if partial derivatives wrt velocity have to be computed

DragForce

public DragForce(Parameter k,
                 Atmosphere atmosphere,
                 DragSensitive spacecraft)

Constructor with multiplicative factor k.

Parameters:

k - parameter representing the multiplicative factor

atmosphere - atmospheric model

spacecraft - the object physical and geometrical information

DragForce

public DragForce(Parameter k,
                 Atmosphere atmosphere,
                 DragSensitive spacecraft,
                 boolean computePDPos,
                 boolean computePDVel)

Constructor with multiplicative factor k.

Parameters:

k - parameter representing the multiplicative factor

atmosphere - atmospheric model

spacecraft - the object physical and geometrical information

computePDPos - if partial derivatives wrt position have to be computed

computePDVel - if partial derivatives wrt velocity have to be computed

DragForce

public DragForce(IParamDiffFunction k,
                 Atmosphere atmosphere,
                 DragSensitive spacecraft)

Constructor with multiplicative factor k.

Parameters:

k - parameterizable function representing the multiplicative factor

atmosphere - atmospheric model

spacecraft - the object physical and geometrical information

DragForce

public DragForce(IParamDiffFunction k,
                 Atmosphere atmosphere,
                 DragSensitive spacecraft,
                 boolean computePDPos,
                 boolean computePDVel)

Constructor with multiplicative factor k.

Parameters:

k - parameterizable function representing the multiplicative factor

atmosphere - atmospheric model

spacecraft - the object physical and geometrical information

computePDPos - if partial derivatives wrt position have to be computed

computePDVel - if partial derivatives wrt velocity have to be computed

Method Detail

addContribution

public void addContribution(SpacecraftState s,
                            TimeDerivativesEquations adder)
                     throws OrekitException

Compute the contribution of the drag to the perturbing acceleration.

Specified by:

addContribution in interface ForceModel

Parameters:

s - the current state information : date, kinematics, attitude

adder - object where the contribution should be added

Throws:

OrekitException - if some specific error occurs

getEventsDetectors

public EventDetector[] getEventsDetectors()

There are no discrete events for this model.

Specified by:

getEventsDetectors in interface ForceModel

Returns:

an empty array

computeGradientPosition

public boolean computeGradientPosition()

This method returns true if the acceleration partial derivatives with respect to position have to be computed.

Specified by:

computeGradientPosition in interface GradientModel

Returns:

true if the derivatives have to be computed, false otherwise

computeGradientVelocity

public boolean computeGradientVelocity()

This method returns true if the acceleration partial derivatives with respect to velocity have to be computed.

Specified by:

computeGradientVelocity in interface GradientModel

Returns:

true if the derivatives have to be computed, false otherwise

computeAcceleration

public Vector3D computeAcceleration(SpacecraftState s)
                             throws OrekitException

Compute the acceleration due to the force.

Specified by:

computeAcceleration in interface ForceModel

Parameters:

s - current state information: date, kinematics, attitude

Returns:

acceleration in the SpacecraftState frame

Throws:

OrekitException - if some specific error occurs

computeAcceleration

public static Vector3D computeAcceleration(PVCoordinates pv,
                                           Frame frame,
                                           Atmosphere atm,
                                           AbsoluteDate date,
                                           double kD,
                                           double mass)
                                    throws OrekitException

Method to compute the acceleration. This method has been implemented in order to validate the force model only. The reason is that for the validation context, we do not want to set up an instance of the SpacecraftState object to avoid the inertial frame of the spacecraft orbit.

(see Story #V84 and Feature #34 on https://www.orekit.org/forge/issues/34)

Out of the validation context, one must use the method Vector3D computeAcceleration(final SpacecraftState s)

In the validation context, we assume that the multiplicative factor is equal to 1.

Parameters:

pv - PV coordinates of the spacecraft (spherical spacecraft only for the validation)

frame - frame in which the PV coordinates are given

atm - atmosphere

date - date

kD - Composite drag coefficient (S.Cd/2).

mass - mass of the spacecraft

Returns:

acceleration

Throws:

OrekitException - if an Orekit error occurs

addDAccDState

public void addDAccDState(SpacecraftState s,
                          double[][] dAccdPos,
                          double[][] dAccdVel)
                   throws OrekitException

Compute acceleration derivatives with respect to state parameters.

Specified by:

addDAccDState in interface IJacobiansParameterizable

Parameters:

s - spacecraft state

dAccdPos - acceleration derivatives with respect to position

dAccdVel - acceleration derivatives with respect to velocity

Throws:

OrekitException - if derivatives cannot be computed

addDAccDParam

public void addDAccDParam(SpacecraftState s,
                          Parameter param,
                          double[] dAccdParam)
                   throws OrekitException

Compute acceleration derivatives with respect to additional parameters..

Specified by:

addDAccDParam in interface IJacobiansParameterizable

Parameters:

s - spacecraft state

param - the parameter with respect to which derivatives are required

dAccdParam - acceleration derivatives with respect to specified parameters

Throws:

OrekitException - if derivatives cannot be computed