You should have a look at thread here about editing saved games. If you open your saved game using SQLiteStudio or similar software you can change feasibility rating of any tech there. First you have to know your techs ID in your game, open: Tables->techs=>Data Tab->Filter technology by name (preferably 1 word or _ instead of spaces) You should find your tech id.
Now go to Table->player_techs->Data Tab->Filter using ID, It should filter out technologies one entry for every player, you need to change one which player_id is 1. Change field feasibility to 1 and player_feasibility to 0.99. Do not forget to commit changes (press orange button with a tick on it assuming you're using SQLiteStudio).
Note: Sometimes you also might need to make changes in player_tech_branches table, to unlock technology branch.
I had good results with "UPDATE player_tech_branches SET feasibility = feasibility + 0.9 WHERE player_id = 1" - it increases Feasibility without completely removing it from the game (btw I'm using Link under Firefox).