MassDepletionDelay.java
- /* Copyright 2002-2022 CS GROUP
- * Licensed to CS GROUP (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
- * limitations under the License.
- */
- package org.orekit.forces.maneuvers.jacobians;
- import org.hipparchus.geometry.euclidean.threed.Vector3D;
- import org.orekit.forces.maneuvers.Maneuver;
- import org.orekit.propagation.SpacecraftState;
- import org.orekit.propagation.integration.AdditionalDerivativesProvider;
- import org.orekit.time.AbsoluteDate;
- /** Generator for effect of delaying mass depletion when delaying a maneuver.
- * @author Luc Maisonobe
- * @since 11.1
- */
- public class MassDepletionDelay implements AdditionalDerivativesProvider {
- /** Prefix for state name. */
- public static final String PREFIX = "Orekit-depletion-";
- /** Name of the mass depletion additional state. */
- private final String depletionName;
- /** Start/stop management flag. */
- private final boolean manageStart;
- /** Maneuver that is delayed. */
- private final Maneuver maneuver;
- /** Indicator for forward propagation. */
- private boolean forward;
- /** Simple constructor.
- * <p>
- * The generated additional state and derivatives will be named by prepending
- * the {@link #PREFIX} to the name of the date trigger parameter.
- * </p>
- * @param triggerName name of the date trigger parameter
- * @param manageStart if true, we compute derivatives with respect to maneuver start
- * @param maneuver maneuver that is delayed
- */
- public MassDepletionDelay(final String triggerName, final boolean manageStart, final Maneuver maneuver) {
- this.depletionName = PREFIX + triggerName;
- this.manageStart = manageStart;
- this.maneuver = maneuver;
- }
- /** {@inheritDoc} */
- @Override
- public String getName() {
- return depletionName;
- }
- /** Get the dimension of the generated column.
- * @return dimension of the generated column
- */
- public int getDimension() {
- return 6;
- }
- /** {@inheritDoc} */
- @Override
- public void init(final SpacecraftState initialState, final AbsoluteDate target) {
- forward = target.isAfterOrEqualTo(initialState);
- }
- /** {@inheritDoc} */
- @Override
- public double[] derivatives(final SpacecraftState state) {
- // retrieve current Jacobian column
- final double[] p = state.getAdditionalState(getName());
- final double[] pDot = new double[6];
- if (forward == manageStart) {
- // current acceleration
- final double[] parameters = maneuver.getParameters();
- final Vector3D acceleration = maneuver.acceleration(state, parameters);
- // we have acceleration Γ = F/m and m = m₀ - q (t - tₛ)
- // where m is current mass, m₀ is initial mass and tₛ is maneuver trigger time
- // a delay dtₛ on trigger time induces delaying mass depletion
- // we get: dΓ = -F/m² dm = -F/m² q dtₛ = -Γ q/m dtₛ
- final double minusQ = maneuver.getPropulsionModel().getMassDerivatives(state, parameters);
- final double m = state.getMass();
- final double ratio = minusQ / m;
- pDot[0] = p[3];
- pDot[1] = p[4];
- pDot[2] = p[5];
- pDot[3] = ratio * acceleration.getX();
- pDot[4] = ratio * acceleration.getY();
- pDot[5] = ratio * acceleration.getZ();
- }
- return pDot;
- }
- }