Transcript An Architecture for Generalized Trajectory Design and

Copernicus, A Generalized
Trajectory Design and
Optimization System
Greg Johnson
Sebastian Munoz
The University of Texas at Austin
November 25, 2003
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
What is trajectory design and
optimization?
► Finding
the best
trajectories for a given
mission
► Example:
Moon Capture
 Earth/Moon trajectory
 Ballistic
► 3rd
body perturbation
Trajectory produced with Copernicus, created in SOAP by Sebastian Munoz
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
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
Some other systems
► VARITOP
► CHEBYTOP
► MIDAS
► SEPSPOT
► GESOP
& ASTOS
► Strengths
and weaknesses
VARITOP
► “General
two-body, sun-centered trajectory
design and optimization program”
► Low
thrust trajectories only
CHEBYTOP
► “General
two-body, sun-centered trajectory
design and optimization program”
► Computationally
quick, but inaccurate
 Quick mission planning, but future analysis
required
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
SEPSPOT
► Computes
trajectories for electrically
propelled spacecraft
► Considers wide range of forces
► Only minimizes time
► Good for Orbital eccentricities less than .65
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
Inspiration
► Copernicus
developed to combine
capabilities of other programs,
without their weaknesses
► Development
Ocampo
began Fall 2001 by Dr. Cesar
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
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
Ocampo, Cesar, “An Architecture for a Generalized Spacecraft Trajectory Design
and Optimization System,” The University of Texas at Austin, Austin, TX, 2003.
methods
used to solve the
problem
What it can do…
► 2-body
transfer/rendezvous
► Return trajectories
► Libration point considerations
► Low thrust trajectories
► Gravity assists
► Ballistic/low energy captures using thirdbody effects
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
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