Ace Combat 3 ES Mission Sim

can anyone help me pls...?

... To get mission simulator you have to get all 5 endings (in other words finish the game 5 times while getting a different ending each time) see gamefaqs if you need help. Only in the european and US version you could unlock Mission Simulator in one go (but you said your playing Ace Combat 3 Electrosphere that must mean its the Jap version, the EU and US version are called just Ace Combat 3, well i haven't played actually the US one but from what i read about it its the same as the EU one).

no, the one that I played wasn't Japanese version, it's either US or European version...
I have played it on real PSX and I managed to unlock the mission simulator, but when I played on emu, it doesn't happen...

Then i don't know i have both the PAL and the NTSC-J one and for the pal one it unlocks Mission Simulator after i beat the game the first time. Though i did it on hard while getting all A's and B's .