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   Finds the cost for going from startNode to nextNode.
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   Form:
   cost = ManeuverCost3D( startNode, nextNode, d )
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   Inputs
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   startNode (1,1) Id of start location
   nextNode  (1,1) Id of next location
   d         (1,1) Data structure
                   .rA     (1,:) Node right ascension
                   .dec    (1,:) Node declination
                   .r      (1,:) Radius

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   Outputs
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   cost      (1,1)  Cost to traverse the distance

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