Invincible by G.P. Hudson (The Pike Chronicles)

The brutal Juttari Empire invaded the Sol System, conquering Earth. The starship Invincible managed to escape the onslaught and has spent the last 25 years on the run. An entire generation has grown up knowing nothing more than life on board this starship. With the ship showing its age and hope running out, an unexpected discovery promises salvation for Invincible and its crew. Can they succeed, despite insurmountable odds?