This program was developed in the mid 1970's under a contract from NASA Glenn Research Center. It was originally called "SECKSPOT" and was written by Ted Edelbaum (and his associates) while he was at MIT Lincoln Labs. For fairly obvious reasons, we gave it a new name. We also gave it new features which facilitate its ease of operation.

The program determines performance associated with a minimum trip time trajectory for electric propulsion spacecraft. It can simulate solar array degradation caused by trapped radiation in the Van Allen belts and shadowing of the spacecraft by the central planet. It allows the user to study orbital transfers from one closed conic to another closed conic. As long as the eccentricity of either the initial or the final orbit is not too large (<.65), the program will usually converge. Although intended as an earth centered program, it now can simulate trajectories about any of the nine planets and the Earth's moon.

The program computes optimal planetocentric trajectories using the techniques of optimal control and orbital averaging. Averaging assumes that of the six orbital elements used to describe a closed conic trajectory, only true anomaly varies quickly in time. By integrating over some number of orbits, one can quickly quantify the effect of several revolutions into a smaller group of terms. One thus solves the optimal control problem using these averaged results rather than "instantaneous" results.

The current version employs many modifications that Carl Sauer (of NASA's Jet Propulsion Lab.) has made over the intervening years since its release. He corrected errors and improved the convergence properties of the two-point boundary value solver. Modifications made at LeRC include generalizing the program to work at any of the Sun's planets not just Earth, adding solar array materials properties, and features to facilitate additional data post-processing.

John P. Riehl

Copies of the documentation are available from the NASA GRC Point of Contact listed above

A tar file containing SEPSPOT can be made available from the anonymous ftp server at external-ftp.grc.nasa.gov. The specifics of location within that ftp server can be obtained by contacting the Point of Contact.

Related Documentation
Theoretical Basis for SEPSPOT
Program outputs and old program inputs
The SEPSPOT Program Inputs & Execution

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1999-01-2449.pdf AIAA-93-4170.pdf AIAA-95-2812.pdf AIAA-96-2810.pdf	AIAA-97-2956.pdf AIAA-98-3591.pdf AIAA-98-3883.pdf NASA_CR-198427.pdf	NASA_CR-198517.pdf NASA_CR-204666.pdf NASA-TM-106406.pdf NASA-TM-1990-103234.pdf	NASA-TM-2000-210243.pdf NASA-TM-2002-211314.pdf NASA-TM-2002-211599.pdf NASA-TM-2002-211871.pdf	NASA-TM-2002-211892.pdf NASA-TM-2002-211893.pdf NASA-TM-2003-212227.pdf NASA-TM-2003-212315.pdf STAIF-2003-177.pdf

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