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.forces.maneuvers;
18  
19  import org.hipparchus.geometry.euclidean.threed.Vector3D;
20  import org.orekit.propagation.SpacecraftState;
21  import org.orekit.time.AbsoluteDate;
22  
23  /** Interface providing velocity increment vectors to impulsive maneuvers.
24   *
25   * @author Romain Serra
26   * @see ImpulseManeuver
27   * @since 13.0
28   */
29  public interface ImpulseProvider {
30  
31      /**
32       * Method returning the impulse to be applied.
33       * @param state state before the maneuver is applied if {@code isForward} is true, after otherwise
34       * @param isForward flag on propagation direction
35       * @return impulse in satellite's frame
36       */
37      Vector3D getImpulse(SpacecraftState state, boolean isForward);
38  
39      /**
40       * Method called at start of propagation.
41       * @param initialState state at start of propagation
42       * @param targetDate target end date
43       */
44      default void init(SpacecraftState initialState, AbsoluteDate targetDate) {
45          // nothing by default
46      }
47  
48      /**
49       * Method called at end of propagation.
50       * @param finalState state at end of propagation
51       */
52      default void finish(SpacecraftState finalState) {
53          // nothing by default
54      }
55  
56      /**
57       * Get a provider returning a given vector for forward propagation and its opposite for backward.
58       * The attitude comes from the state directly.
59       * @param forwardImpulse forward impulse vector
60       * @return constant provider
61       */
62      static ImpulseProvider of(final Vector3D forwardImpulse) {
63          return (state, isForward) -> isForward ? forwardImpulse : forwardImpulse.negate();
64      }
65  }