you dont, you cannot get it anymore, vets complained and had the rank up missions needed removed, they where mad people could in days or weeks, do what it took them months or years to do...rank up with empire/fed...you need federation rank to unlock sol, you are SOL( out of luck m8) because, they removed those, to make vets happy.
you canjot ge now.
wont work, fed/empire/etc rank gain is frozen and rank unlock missions removed, you have said you are one who reported this and demanded it be addressed, for your pride.
stop telling people to do things that wont work or do them any good, nobody can rank up or unlock anything now, and thats a good thing, it should take years of in game time before people can get fed ranks or unlock the big3...you said so yourself...it hurts your pride knowing others got things faster...