What website would you go onto to find a free demo of pinball space cadet?????????????

Answer 1

Space cadet was created for Microsoft by Maxis (in 1995)
http://en.wikipedia.org/wiki/Maxis

They are famous for Sims City.

Their website is at
http://www.maxis.com/

However, I am not aware of a demo site for the Space Cadet game.

Other than the name (and the theme), it does not have much to do with astronomy & space...
;-)