Colony Defence

In most similar games there is the option of building some sort of ground/orbital defence grid on a planet. I haven`t gotten Starbase research finished yet so I don`t know if that ship works quite like what I`m talking about, but without such a feature the attacking party will always have a significant advantage over the defender, because the attacker can build a fleet they could never have the funds to sustain just to attack with it and burn off what they can`t while the defender has to sustain their own fleet or build that unsustainable fleet and simply stop playing until they are attacked.