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Copernicus, A Generalized Trajectory Design and Optimization System

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  1. Copernicus, A Generalized Trajectory Design and Optimization System Greg Johnson Sebastian Munoz The University of Texas at Austin November 25, 2003

  2. Overview • What is trajectory design and optimization? • What makes this problem so difficult? • The necessity for a generalized trajectory system • Existing systems • The Copernicus trajectory system • Conclusions

  3. Trajectory produced with Copernicus, created in SOAP by Sebastian Munoz What is trajectory design and optimization? • Finding the best trajectories for a given mission • Example: Moon Capture • Earth/Moon trajectory • Ballistic • 3rd body perturbation

  4. What makes this problem so difficult? • What is the best trajectory? • Minimized parameters • Total ΔV • Time of flight • Maximized parameters • Payload capacity • Excess fuel • Finding a trajectory with optimal values for one or all of these parameters

  5. The necessity of a general system • General • “Not limited in scope, area or application” –The American Heritage Dictionary of the English Language • Capabilities of a general system • ΔV minimization • Time of flight minimization • Payload maximization • Excess fuel maximization • Multiple segments for a trajectory • Such a system would satisfy the needs for any mission, including complex interplanetary trajectories

  6. Some other systems • VARITOP • CHEBYTOP • MIDAS • SEPSPOT • GESOP & ASTOS • Strengths and weaknesses

  7. VARITOP • “General two-body, sun-centered trajectory design and optimization program” • Low thrust trajectories only

  8. CHEBYTOP • “General two-body, sun-centered trajectory design and optimization program” • Computationally quick, but inaccurate • Quick mission planning, but future analysis required

  9. MIDAS • “Patched-conic interplanetary trajectory solver” • Minimizes ΔV and mass, not time • Difficult to use, large input files • Created to verify the validity of results from other programs

  10. SEPSPOT • Computes trajectories for electrically propelled spacecraft • Considers wide range of forces • Only minimizes time • Good for Orbital eccentricities less than .65

  11. GESOP & ASTOS • “Graphical Environment for Simulation and OPtimization” • Can simulate any dynamical system • Uses ASTOS application for spacecraft trajectory optimization • Requires large amount of input • Result accuracy may be affected by broadness of problems it can solve

  12. Inspiration • Copernicus developed to combine capabilities of other programs, without their weaknesses • Development began Fall 2001 by Dr. Cesar Ocampo

  13. Ocampo, Cesar, “An Architecture for a Generalized Spacecraft Trajectory Design and Optimization System,” The University of Texas at Austin, Austin, TX, 2003. Copernicus Trajectory System • Goals • Solve any type of trajectory problem • Initial and final states • Fixed or variable • Parameters to minimize or maximize • Any or all • Methods used • “Basic” trajectory segment

  14. Ocampo, Cesar, “An Architecture for a Generalized Spacecraft Trajectory Design and Optimization System,” The University of Texas at Austin, Austin, TX, 2003. The Trajectory Segment • Allows boundary conditions to be specified • Allows discontinuities • Fixed/free parameters • Numerical methods used to solve the problem

  15. What it can do… • 2-body transfer/rendezvous • Return trajectories • Libration point considerations • Low thrust trajectories • Gravity assists • Ballistic/low energy captures using third-body effects

  16. Conclusions • General system is necessary • Saves mission design time, and man hours • Reliable for any conceivable problem • Copernicus is the most general trajectory design and optimization system available • combines features of other programs without their weaknesses • Copernicus is still a prototype, hence there is still a lot to be done – i.e. graphical user interface, OpenGL graphics

  17. References • For more information about the trajectory systems discussed, see: • Ocampo, Cesar, “An Architecture for a Generalized Spacecraft Trajectory Design and Optimization System,” The University of Texas at Austin, Austin, TX, 2003. • http://trajectory.grc.nasa.gov/Tools • http://www.astos.de