Optimal Thrust Vector Control of Coplanar Orbital Evasive Maneuvers
Abstract
Optimal inplane orbital maneuvers enabling a target spacecraft in geosynchronous orbit to avoid interception by a threat in direct coasting ascent are examined. Given constant magnitude, low thrust electric propulsion, the thrust vector control history is determined to propel the spacecraft to either a maximum or minimum orbit radius in a specified time of flight. The evasive maneuver is studied from two aspects. First, an orthogonality constraint is applied at the final time of the maneuver, such that the target spacecraft's position vector is orthogonal to its velocity vector. This requirement is then removed to allow the spacecraft to travel without influence of a terminal constraint. Results demonstrate the adverse shaping effect the orthogonality constraint applies over the entire evasive maneuver. Upon completion of the evasive maneuver, the spacecraft returns in minimum time to its nominal orbit, in a position as if no evasive thrusting had occurred. Results show the time required to rendezvous with the nominal orbit may be significantly greater than the time of flight of the evasive maneuver. Optimal control is applied to formulate the evasive and rendezvous maneuvers using Euler-Lagrange theory and the calculus or variations. The behavior of the Lagrange costates is examined in terms of their effect upon solution convergence. The resulting two point boundary value problem is solved by numerical methods to yield the optimal spaceflight trajectory.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 1987
- Accession Number
- ADA189544
Entities
People
- Sharon A. Eide
Organizations
- Air Force Institute of Technology