1   /* Copyright 2022-2025 Romain Serra
2    * Licensed to CS GROUP (CS) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * CS licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    *
9    *   http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  package org.orekit.control.indirect.adjoint.cost;
18  
19  import org.hipparchus.util.FastMath;
20  import org.orekit.propagation.events.EventDetectionSettings;
21  import org.orekit.propagation.events.EventDetector;
22  
23  import java.util.stream.Stream;
24  
25  /**
26   * Class for unbounded energy cost with Cartesian coordinates.
27   * Here, the control vector is chosen as the thrust force, expressed in the propagation frame.
28   * This leads to the optimal thrust being in the same direction as the adjoint velocity.
29   * @author Romain Serra
30   * @see UnboundedCartesianEnergyNeglectingMass
31   * @since 12.2
32   */
33  public class UnboundedCartesianEnergy extends CartesianEnergyConsideringMass {
34  
35      /**
36       * Constructor.
37       * @param name name
38       * @param massFlowRateFactor mass flow rate factor
39       * @param eventDetectionSettings detection settings for singularity detections
40       */
41      public UnboundedCartesianEnergy(final String name, final double massFlowRateFactor,
42                                      final EventDetectionSettings eventDetectionSettings) {
43          super(name, massFlowRateFactor, eventDetectionSettings);
44      }
45  
46      /**
47       * Constructor.
48       * @param name name
49       * @param massFlowRateFactor mass flow rate factor
50       */
51      public UnboundedCartesianEnergy(final String name, final double massFlowRateFactor) {
52          this(name, massFlowRateFactor, EventDetectionSettings.getDefaultEventDetectionSettings());
53      }
54  
55      /** {@inheritDoc} */
56      @Override
57      protected double getThrustForceNorm(final double[] adjointVariables, final double mass) {
58          final double adjointVelocityNorm = getAdjointVelocityNorm(adjointVariables);
59          double factor = adjointVelocityNorm / mass;
60          if (getAdjointDimension() > 6) {
61              factor -= getMassFlowRateFactor() * adjointVariables[6];
62          }
63          return FastMath.max(0., factor);
64      }
65  
66      /** {@inheritDoc} */
67      @Override
68      public Stream<EventDetector> getEventDetectors() {
69          return Stream.of(new SingularityDetector(getEventDetectionSettings(), 0.));
70      }
71  }