Finally got TSG and TSG:Missions running again as of 11/30/2021 on PC - what worked for me was BlueMaxima’s “FlashPoint 10.1 Infinity” (715MB download, 3GB when installed) - install, open, search for “The Space Game”, and you’ll find the original plus the “Missions” sequel. Thank you to BlueMaxima and anyone else who contributed to preserving this amazinly fun game!
 "The Space Game"){kind=icon}