This is a simple MFD that implements a solar sail for any vessel.
How to use:
Open an MFD
Set sail efficiency ([eff] or Shift+P) (in newtons per m^2) and square ([sqr] or Shift+S) (m^2).
Shift+G toggles it on/off.
Debug string shows current angle to the sun (ang) and push force (pow).
Since i don't know much about how a solar sail must behave i just made it behave like on a naval sailing vessel.
This is a prototype software, so it may have bugs (but it should be too simple for one), so any feedback is appreciated both for physics and for bugs.