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.geometry.euclidean.threed.Vector3D;
20  import org.orekit.propagation.events.EventDetector;
21  
22  import java.util.stream.Stream;
23  
24  /**
25   * Class for unbounded energy cost with Cartesian coordinates neglecting the mass consumption.
26   * Under this assumption, the mass is constant and there is no need to consider the corresponding adjoint variable.
27   * Here, the control vector is chosen as the acceleration given by thrusting, expressed in the propagation frame.
28   * This leads to the optimal thrust force being equal to the adjoint velocity vector times the mass.
29   * @author Romain Serra
30   * @since 12.2
31   */
32  public class UnboundedCartesianEnergyNeglectingMass extends AbstractCartesianCost {
33  
34      /**
35       * Constructor.
36       * @param name name
37       */
38      public UnboundedCartesianEnergyNeglectingMass(final String name) {
39          super(name, 0.);
40      }
41  
42      /** {@inheritDoc} */
43      @Override
44      public Vector3D getThrustAccelerationVector(final double[] adjointVariables, final double mass) {
45          return new Vector3D(adjointVariables[3], adjointVariables[4], adjointVariables[5]);
46      }
47  
48      /** {@inheritDoc} */
49      @Override
50      public void updateAdjointDerivatives(final double[] adjointVariables, final double mass,
51                                           final double[] adjointDerivatives) {
52          // nothing to do
53      }
54  
55      /** {@inheritDoc} */
56      @Override
57      public double getHamiltonianContribution(final double[] adjointVariables, final double mass) {
58          final Vector3D thrustAcceleration = getThrustAccelerationVector(adjointVariables, mass);
59          return -thrustAcceleration.getNormSq() / 2.;
60      }
61  
62      /** {@inheritDoc} */
63      @Override
64      public Stream<EventDetector> getEventDetectors() {
65          return Stream.empty();
66      }
67  
68  }