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Public Domain Aeronautical Software (PDAS)  

This is an interesting little program from the old COSMIC collection. It isn't really aeronautical, but a modern aeronautical engineer should learn a bit about orbits and launch vehicles. It defines a satellite in earth orbit at a specific day of the year and tracks an array of solar panels through a complete orbit around the earth. It works out the 3-D geometry of angles between the sun and satellite and earth and comes up with an estimate of power. It is so old that I am sure the conversion efficiencies and weight estimates are out of date. If you can send me some better numbers for these, I can make an updated version someday.

This program was written by Rockwell International for NASA Marshall Spaceflight Center. It was originally released as program MSC-18558. The program has been modified by Public Domain Aeronautical Software to conform to Fortran 90 standards. All subroutines have placed in a module; all variables have declared types; all subroutine arguments have declared intent; and all code that used deprecated features of Fortran 95 have been recoded. As further proof of its compliance with all Fortran 95 standards, it may be noted that it compiles and runs with the ELF compiler from Lahey.

The student of astronautics can see the techniques for constructing an ephemeris of an orbiting body, the calculation of black-body radiation from the sun with corrections for reflection and shadowing of the earth, and the radiation from the photoelectric array. The calculation of the temperature of the satellite is done by numerical solution of the differential equations of heat absorbtion and radiation.

Originally released thru COSMIC as program MSC-18558 with the following description:

Solar arrays are becoming an increasingly important means of generating power for earth orbiting spacecraft. Currently, almost all unmanned earth satellites utilize solar array electrical power generation systems. Applications for solar arrays in the near future include providing power for space shuttle payloads and manned space stations. This computer program was developed to simulate the capabilities of earth orbiting arrays. The model used is based on an improved version of a finite-element radiation shape factor subprogram. The inherent simplicity and speed of the original subprogram has been augmented with an improved shadow evaluation technique to provide the user with an efficient array model.

The program allows the characteristics of orbiting arrays to be evaluated with a minimum of user effort and computer cost. Input to the program consists of a brief description of the array and the orbital parameters. The orbital parameters are used to determine the direct solar radiation incident on the cells, incident solar radiation reflected to cells from the earth, and the shadowing of any cells. Once the amount of thermal radiation gained and lost by the array is known, the amount of power which can be generated and the temperature of the array is determined.

PDAS home > Contents > Solar Array
Public Domain Aeronautical Software (PDAS)