There is no in-game funtion to have multiple save file currently. You can only backup your save file manually. The save file is located under C:\Users\(Your user name)\AppData (hidden)\Local\Astro\Saved\SaveGames. The filename format is "savename$date-time". Everytime you quit the game or enter a space shuttle/rover seat/shelter the game updates that save file. You can copy that file to another folder as backups. When you would like to restore, quit the game first, delete the newly generated savefile, then copy the backup file back to the original folder. Now re-enter the game and you can load your backup save data. Hope that helps.