In this comment below the question Visualization of non-Keplerian orbits for solar sails, NASA's open source General Mission Analysis Tool is suggested. Sounds great!
The link https://gmat.gsfc.nasa.gov/ only gives me a "your connection is not private" error (shown below) even when I delete the
s and change it back to
http:// , and http://opensource.gsfc.nasa.gov/projects/GMAT/index.php seems to be a dead end.
Where can I find this software? Is it something I have to compile on my computer, or is it hosted somewhere?