I found fighting in combat zones gives rep for the federation but did not trigger ranking missions,it was running missions for the individual factions at stations that triggered my naval missions..
Work on a 3 or more stations at a time, hitec, agricultural, industrial .. Hitec will ask for food handouts, agricultural will want food cartridges and industrial will want non leathal weopons.. Only take the missions for the federal factions not the independents.. I found it takes about 2 such missions to go from neutral to friendly, 4 or more gets you to allied.. Once done move oto another 3 stations..I found each time becoming friendly with about 6 minor factions triggered a ranking mission..
Currently I am Lt. commander in federal space and Count in empire..
when I switched from trading to combat for a while I became allied with the Feds really quick but did not see another naval mission until I started trading and building individual rep again..