| Answer | The differential corrector, while being a robust algorithm for solving many targeting problems, does not have control over the range of values. Because of this, there is no way to limit the value of the controls to be positive. There are two cases for which the differential corrector will push a duration value negative.
1. One common case can occur with a finite maneuver. The differential corrector will push the duration value negative if the maneuver is not targeting the direction and the direction is set in the opposite direction from that which is required. You can resolve this by changing the thrust vector 180 degrees opposite the initial vector.
For more information on thrust vectors in finite maneuvers, see the help topic Finite Maneuver Segment.
2. The second case is when the result occurs before the propagate segment begins. The differential corrector will push the duration negative to search for the equality constraint. To remedy this, alter the MCS such that the equality constraint happens at a positive time from the beginning of the propagate segment. |
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