There is a daily limitation (or 20h to be concrete), but the first time you do them they count as tutorial and give 480 dil each (Romulan & Fed), and you can do the same following missions after the "tutorial" ones (because there is no countdown on the first time) that will now give 1460 dil each.
Do them a couple od times and it opens new options like adding the Cardassians so then you'll be able to do 3 dailies at this point of time and so.
There are more options for dil. on the KDF side, but I've mentioned these cause you were specific about ship combat and these nebula encounters are always space combat by default.
this will come in handy ty vm im looking for foudnry missions for just plane fun fleet actyion not farming just fun ship killing only care to list a few? i know multiplayer also like i said i like ot mix it up so far i will say the klingon side has more ships that are of interest to me compared ot the fed side dont get mr wrong the armitage looks somewhat ok and i love my odyship, the multivector looks semi but that is about it whjere as the klingon damn i look forward to the bortasqu pack,Guramba siege destroyer,Marauder ,Corsair flight deck cruiser,karfai battle carrier i think in time i will get all of these bad boys