/* Copyright 2002-2017 CS Systèmes d'Information
* Licensed to CS Systèmes d'Information (CS) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* CS licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
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package org.orekit.forces.maneuvers;
import org.hipparchus.geometry.euclidean.threed.Vector3D;
import org.hipparchus.util.FastMath;
import org.orekit.attitudes.Attitude;
import org.orekit.attitudes.AttitudeProvider;
import org.orekit.errors.OrekitException;
import org.orekit.orbits.CartesianOrbit;
import org.orekit.propagation.SpacecraftState;
import org.orekit.propagation.events.AbstractDetector;
import org.orekit.propagation.events.EventDetector;
import org.orekit.propagation.events.handlers.EventHandler;
import org.orekit.time.AbsoluteDate;
import org.orekit.utils.Constants;
import org.orekit.utils.PVCoordinates;
/** Impulse maneuver model.
* <p>This class implements an impulse maneuver as a discrete event
* that can be provided to any {@link org.orekit.propagation.Propagator
* Propagator}.</p>
* <p>The maneuver is triggered when an underlying event generates a
* {@link org.orekit.propagation.events.handlers.EventHandler.Action#STOP STOP} event,
* in which case this class will generate a {@link
* org.orekit.propagation.events.handlers.EventHandler.Action#RESET_STATE RESET_STATE}
* event (the stop event from the underlying object is therefore filtered out).
* In the simple cases, the underlying event detector may be a basic
* {@link org.orekit.propagation.events.DateDetector date event}, but it
* can also be a more elaborate {@link
* org.orekit.propagation.events.ApsideDetector apside event} for apogee
* maneuvers for example.</p>
* <p>The maneuver is defined by a single velocity increment in satellite
* frame. The current attitude of the spacecraft, defined by the current
* spacecraft state, will be used to compute the velocity direction in
* inertial frame. A typical case for tangential maneuvers is to use a
* {@link org.orekit.attitudes.LofOffset LOF aligned} attitude provider for state propagation and a
* velocity increment along the +X satellite axis.</p>
* <p>Beware that the triggering event detector must behave properly both
* before and after maneuver. If for example a node detector is used to trigger
* an inclination maneuver and the maneuver change the orbit to an equatorial one,
* the node detector will fail just after the maneuver, being unable to find a
* node on an equatorial orbit! This is a real case that has been encountered
* during validation ...</p>
* @see org.orekit.propagation.Propagator#addEventDetector(EventDetector)
* @param <T> class type for the generic version
* @author Luc Maisonobe
*/
public class ImpulseManeuver<T extends EventDetector> extends AbstractDetector<ImpulseManeuver<T>> {
/** Serializable UID. */
private static final long serialVersionUID = 20131118L;
/** The attitude to override during the maneuver, if set. **/
private final AttitudeProvider attitudeOverride;
/** Triggering event. */
private final T trigger;
/** Velocity increment in satellite frame. */
private final Vector3D deltaVSat;
/** Specific impulse. */
private final double isp;
/** Engine exhaust velocity. */
private final double vExhaust;
/** Indicator for forward propagation. */
private boolean forward;
/** Build a new instance.
* @param trigger triggering event
* @param deltaVSat velocity increment in satellite frame
* @param isp engine specific impulse (s)
*/
public ImpulseManeuver(final T trigger, final Vector3D deltaVSat, final double isp) {
this(trigger.getMaxCheckInterval(), trigger.getThreshold(),
trigger.getMaxIterationCount(), new Handler<T>(),
trigger, null, deltaVSat, isp);
}
/** Build a new instance.
* @param trigger triggering event
* @param attitudeOverride the attitude provider to use for the maneuver
* @param deltaVSat velocity increment in satellite frame
* @param isp engine specific impulse (s)
*/
public ImpulseManeuver(final T trigger, final AttitudeProvider attitudeOverride, final Vector3D deltaVSat, final double isp) {
this(trigger.getMaxCheckInterval(), trigger.getThreshold(),
trigger.getMaxIterationCount(), new Handler<T>(),
trigger, attitudeOverride, deltaVSat, isp);
}
/** Private constructor with full parameters.
* <p>
* This constructor is private as users are expected to use the builder
* API with the various {@code withXxx()} methods to set up the instance
* in a readable manner without using a huge amount of parameters.
* </p>
* @param maxCheck maximum checking interval (s)
* @param threshold convergence threshold (s)
* @param maxIter maximum number of iterations in the event time search
* @param handler event handler to call at event occurrences
* @param trigger triggering event
* @param attitudeOverride the attitude provider to use for the maneuver
* @param deltaVSat velocity increment in satellite frame
* @param isp engine specific impulse (s)
* @since 6.1
*/
private ImpulseManeuver(final double maxCheck, final double threshold,
final int maxIter, final EventHandler<? super ImpulseManeuver<T>> handler,
final T trigger, final AttitudeProvider attitudeOverride, final Vector3D deltaVSat,
final double isp) {
super(maxCheck, threshold, maxIter, handler);
this.attitudeOverride = attitudeOverride;
this.trigger = trigger;
this.deltaVSat = deltaVSat;
this.isp = isp;
this.vExhaust = Constants.G0_STANDARD_GRAVITY * isp;
}
/** {@inheritDoc} */
@Override
protected ImpulseManeuver<T> create(final double newMaxCheck, final double newThreshold,
final int newMaxIter, final EventHandler<? super ImpulseManeuver<T>> newHandler) {
return new ImpulseManeuver<T>(newMaxCheck, newThreshold, newMaxIter, newHandler,
trigger, attitudeOverride, deltaVSat, isp);
}
/** {@inheritDoc} */
public void init(final SpacecraftState s0, final AbsoluteDate t) {
forward = t.durationFrom(s0.getDate()) >= 0;
}
/** {@inheritDoc} */
public double g(final SpacecraftState s) throws OrekitException {
return trigger.g(s);
}
/**
* Get the Attitude Provider to use during maneuver.
* @return the attitude provider
*/
public AttitudeProvider getAttitudeOverride() {
return attitudeOverride;
}
/** Get the triggering event.
* @return triggering event
*/
public T getTrigger() {
return trigger;
}
/** Get the velocity increment in satellite frame.
* @return velocity increment in satellite frame
*/
public Vector3D getDeltaVSat() {
return deltaVSat;
}
/** Get the specific impulse.
* @return specific impulse
*/
public double getIsp() {
return isp;
}
/** Local handler.
* @param <T> class type for the generic version
*/
private static class Handler<T extends EventDetector> implements EventHandler<ImpulseManeuver<T>> {
/** {@inheritDoc} */
public EventHandler.Action eventOccurred(final SpacecraftState s, final ImpulseManeuver<T> im,
final boolean increasing)
throws OrekitException {
// filter underlying event
final EventHandler.Action underlyingAction = im.trigger.eventOccurred(s, increasing);
return (underlyingAction == Action.STOP) ? Action.RESET_STATE : Action.CONTINUE;
}
/** {@inheritDoc} */
@Override
public SpacecraftState resetState(final ImpulseManeuver<T> im, final SpacecraftState oldState)
throws OrekitException {
final AbsoluteDate date = oldState.getDate();
final AttitudeProvider override = im.getAttitudeOverride();
final Attitude attitude;
if (override == null) {
attitude = oldState.getAttitude();
} else {
attitude = override.getAttitude(oldState.getOrbit(), date, oldState.getFrame());
}
// convert velocity increment in inertial frame
final Vector3D deltaV = attitude.getRotation().applyInverseTo(im.deltaVSat);
final double sign = im.forward ? +1 : -1;
// apply increment to position/velocity
final PVCoordinates oldPV = oldState.getPVCoordinates();
final PVCoordinates newPV =
new PVCoordinates(oldPV.getPosition(),
new Vector3D(1, oldPV.getVelocity(), sign, deltaV));
final CartesianOrbit newOrbit =
new CartesianOrbit(newPV, oldState.getFrame(), date, oldState.getMu());
// compute new mass
final double newMass = oldState.getMass() * FastMath.exp(-sign * deltaV.getNorm() / im.vExhaust);
// pack everything in a new state
return new SpacecraftState(oldState.getOrbit().getType().convertType(newOrbit),
attitude, newMass);
}
}
}