AbstractConstantThrustPropulsionModel.java

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 * CS licenses this file to You under the Apache License, Version 2.0
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 *
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package org.orekit.forces.maneuvers.propulsion;

import org.hipparchus.CalculusFieldElement;
import org.hipparchus.geometry.euclidean.threed.FieldVector3D;
import org.hipparchus.geometry.euclidean.threed.Vector3D;
import org.orekit.propagation.FieldSpacecraftState;
import org.orekit.propagation.SpacecraftState;
import org.orekit.utils.Constants;

/** This abstract class simply serve as a container for a constant thrust maneuver.
 * It re-writes all spacecraft dependent methods from {@link ThrustPropulsionModel}
 * and removes their dependencies to current spacecraft state.
 * Indeed since the thrust is constant (i.e. not variable during the maneuver), most of the
 * calculated parameters (thrust vector, flow rate etc.) do not depend on current spacecraft state.
 * @author Maxime Journot
 * @since 10.2
 */
public abstract class AbstractConstantThrustPropulsionModel implements ThrustPropulsionModel {

    /** Initial thrust vector (N) in S/C frame, when building the object. */
    private final Vector3D initialThrustVector;

    /** Initial flow rate (kg/s), when building the object. */
    private final double initialFlowRate;

    /** User-defined name of the maneuver.
     * This String attribute is empty by default.
     * It is added as a prefix to the parameter drivers of the maneuver.
     * The purpose is to differentiate between drivers in the case where several maneuvers
     * were added to a propagator force model.
     * Additionally, the user can retrieve the whole maneuver by looping on the force models of a propagator,
     * scanning for its name.
     * @since 9.2
     */
    private final String name;

    /** Generic constructor.
     * @param thrust initial thrust value (N)
     * @param isp initial isp value (s)
     * @param direction initial thrust direction in S/C frame
     * @param name name of the maneuver
     */
    public AbstractConstantThrustPropulsionModel(final double thrust,
                                                 final double isp,
                                                 final Vector3D direction,
                                                 final String name) {
        this.name = name;
        this.initialThrustVector = direction.normalize().scalarMultiply(thrust);
        this.initialFlowRate = -thrust / (Constants.G0_STANDARD_GRAVITY * isp);
    }

    protected Vector3D getInitialThrustVector() {
        return initialThrustVector;
    }

    protected double getInitialFlowrate() {
        return initialFlowRate;
    }

    /** {@inheritDoc} */
    @Override
    public String getName() {
        return name;
    }

    /** Get the specific impulse.
     * @return specific impulse (s).
     */
    public double getIsp() {
        final double thrust   = getThrust();
        final double flowRate = getFlowRate();
        return -thrust / (Constants.G0_STANDARD_GRAVITY * flowRate);
    }

    /** Get the thrust direction in S/C frame.
     * @return the thrust direction in S/C frame
     */
    public Vector3D getDirection() {
        return getThrustVector().normalize();
    }

    /** Get the thrust value (N).
     * @return the thrust value (N)
     */
    public double getThrust() {
        return getThrustVector().getNorm();
    }

    /** {@inheritDoc}
     * Here the thrust vector do not depend on current S/C state.
     */
    @Override
    public Vector3D getThrustVector(final SpacecraftState s) {
        // Call the abstract function that do not depend on current S/C state
        return getThrustVector();
    }

    /** {@inheritDoc}
     * Here the flow rate do not depend on current S/C state
     */
    @Override
    public double getFlowRate(final SpacecraftState s) {
        // Call the abstract function that do not depend on current S/C state
        return getFlowRate();
    }

    /** {@inheritDoc}
     * Here the thrust vector do not depend on current S/C state.
     */
    @Override
    public Vector3D getThrustVector(final SpacecraftState s, final double[] parameters) {
        // Call the abstract function that do not depend on current S/C state
        return getThrustVector(parameters);
    }

    /** {@inheritDoc}
     * Here the flow rate do not depend on current S/C state
     */
    public double getFlowRate(final SpacecraftState s, final double[] parameters) {
        // Call the abstract function that do not depend on current S/C state
        return getFlowRate(parameters);
    }

    /** {@inheritDoc}
     * Here the thrust vector do not depend on current S/C state.
     */
    public <T extends CalculusFieldElement<T>> FieldVector3D<T> getThrustVector(final FieldSpacecraftState<T> s,
                                                                            final T[] parameters) {
        // Call the abstract function that do not depend on current S/C state
        return getThrustVector(parameters);
    }

    /** {@inheritDoc}
     * Here the flow rate do not depend on current S/C state
     */
    public <T extends CalculusFieldElement<T>> T getFlowRate(final FieldSpacecraftState<T> s, final T[] parameters) {
        // Call the abstract function that do not depend on current S/C state
        return getFlowRate(parameters);
    }

    /** Get the thrust vector in spacecraft frame (N).
     * Here it does not depend on current S/C state.
     * @return thrust vector in spacecraft frame (N)
     */
    public abstract Vector3D getThrustVector();

    /** Get the flow rate (kg/s).
     * Here it does not depend on current S/C.
     * @return flow rate (kg/s)
     */
    public abstract double getFlowRate();

    /** Get the thrust vector in spacecraft frame (N).
     * Here it does not depend on current S/C state.
     * @param parameters propulsion model parameters
     * @return thrust vector in spacecraft frame (N)
     */
    public abstract Vector3D getThrustVector(double[] parameters);

    /** Get the flow rate (kg/s).
     * Here it does not depend on current S/C state.
     * @param parameters propulsion model parameters
     * @return flow rate (kg/s)
     */
    public abstract double getFlowRate(double[] parameters);

    /** Get the thrust vector in spacecraft frame (N).
     * Here it does not depend on current S/C state.
     * @param parameters propulsion model parameters
     * @param <T> extends CalculusFieldElement&lt;T&gt;
     * @return thrust vector in spacecraft frame (N)
     */
    public abstract <T extends CalculusFieldElement<T>> FieldVector3D<T> getThrustVector(T[] parameters);

    /** Get the flow rate (kg/s).
     * Here it does not depend on current S/C state.
     * @param parameters propulsion model parameters
     * @param <T> extends CalculusFieldElement&lt;T&gt;
     * @return flow rate (kg/s)
     */
    public abstract <T extends CalculusFieldElement<T>> T getFlowRate(T[] parameters);
}