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I recently made a spreadsheet for non-Hohmann Earth Mars (or vice versa) trips. I've been wanting to do this for a long time. RobS provided the nudge.
Years and AU (astronomical unit) are the preferred units. Traditional dates are an unwieldy combination of years, months and days. I use
http://clowder.net/hop/date]http://clow … alyear.xls
to convert dates to decimal years.
Once a date's in decimal year format, Earth or Mars coordinates close to that date can be found in
http://clowder.net/hop/EarthMars.xls]ht … thMars.xls
This gives space time coordinates for each vertice of 1000 sided polygons approximating Earth and Mars orbits.
Also given is velocity vector at a space time point.
This spreadsheet is big - about a megabyte.
The last spreadsheet is
http://clowder.net/hop/lambtrans2.xls]h … trans2.xls
In Excel Preferences iteration must be turned on or Circular Reference errors occur.
Cell B7 is the reset switch. Typing 0 into b7 will erase info stored in iteration cells, typing 1 will restart iterations.
From EarthMars.xls copy space-time coordinates of departure point as well as velocity vector and paste these 7 values into cells A12 to G12 (not an ordinary paste, use Paste Special and choose Value button in dialogue box)
Likewise paste destination coordinates and velocity vector into cells A13 to G13 of the lambtrans spreadsheet.
Hope these are helpful. If anyone finds misteaks or bugs please let me know.
Hop's [url=http://www.amazon.com/Conic-Sections-Celestial-Mechanics-Coloring/dp/1936037106]Orbital Mechanics Coloring Book[/url] - For kids from kindergarten to college.
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I found the Excell preferences and will play with this more tonight. I haven't tried cutting and pasting the coordinates from EarthMars.xls yet. Can this program be used to plot mars to Earth trajectories as well as Earth to Mars? I didn't see a way to do that.
-- RobS
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The first seven cells of row 12 is the starting point info and the first seven cells of row 13 is destination info.
So to start from Mars copy the 7 martian cells closest to the departure date and paste them into the 12th row.
Then find the 7 earth cells closest to arrival date and paste them into the 13th row.
It's aggravating that it runs iterations each time data's changed. But it goes through them faster if the reset cell (B7) equals zero. Then when all the info is entered, set the reset to equal 1.
I believe 100 iterations is Excel's default. But 50 probably suffices.
Hop's [url=http://www.amazon.com/Conic-Sections-Celestial-Mechanics-Coloring/dp/1936037106]Orbital Mechanics Coloring Book[/url] - For kids from kindergarten to college.
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