Troy Rising Series by John Ringo (Books 1 to 3)

First Contact Was Friendly

When aliens trundled a gate to other worlds into the Solar System, the world reacted with awe, hope and fear. When the first aliens to come through, the Glatun, turned out to be peaceful traders, the world breathed a sigh of relief.

Who Controls the Orbitals, Controls the World

When the Horvath came through, they announced their ownership of us by dropping rocks on three cities and gutting them. Since then, they've held Terra as their own personal fiefdom. With their control of the orbitals, there's no way to win and Earth's governments have accepted the status quo.

Live Free or Die

To free the world from the grip of the Horvath is going to take an unlikely hero. A hero unwilling to back down to alien or human governments, unwilling to live in slavery and with enough hubris, if not stature, to think he can win.

Fortunately, there's Tyler Vernon. And he has bigger plans than just getting rid of the Horvath.
Troy Rising is a book in three parts—Live Free or Die being the first part—detailing the freeing of Earth from alien conquerors, the first steps into space using off-world technologies and the creation of Troy, a thousand trillion ton battlestation designed to secure the Solar System.