If you radio BDU, (and you are out of torps) they will order you to return at any rate. You will probably lose some points for not making your PA and staying there for 24 hours, but shouldn't be reduced much. You won't lose renown for the two ships though.
Also, if you choose to, there is a way to add renown to a campaign. (Kind of cheating... well no, it IS cheating...), but if you feel you deserve it, what the heck!
S