What is the best way to create volume fog effect for a space sim without compromising performance ?

I have tried Global fog,but there are a few problems with it so i opt out of using it.

In my game the scenes are all set in space so I was hoping that i could easily get a simple fog going in the game . but its actually a bit difficult.

I have tried using particle systems with billboard planes with a foggy looking image on them but i fun into a few GPU processing issues there.

if not a volume fog then anything but global fog would be good.

any ideas on how I could get a fog going that will not compromise my GPU ?