The Ur Quan Masters

In the last phase of the war between the Alliance of Free Stars and the Hierarchy of Battle Thralls, the Tobermoon, an Earthling ship, discovered an ancient Precursor subterranean installation in a cave on the surface of an uninhabited planet in the Vela star system. The Alliance hastily sent a secret scientific mission to study the relics, but a massive Hierarchy offensive forced the Alliance fleets to retreat beyond Vela; the mission commander, Captain Burton, decided to go into hiding on the planet and sent back the Tobermoon, her only starship, asking for help. Though the Ur-Quan forces didn't find the Earthlings during their sweep of the system, relief never arrived. Years later, with the help of a genius child born on the planet, the colonists activated the Precursor machinery and found out that it was programmed to build a starship. Using the limited store of raw materials available in the planet, in ten years the Precursor factory built a (barely) functional ship, which could be piloted only by the now grown genius child, who alone could interact with the Precursor central computer. In the first test flight, it was discovered that the ship Burton had sent for help had been severely damaged by the Ur-Quan and was orbiting unpowered in the outer solar system: the Alliance had never known of the mission's discoveries. The colonists decided to fix the recovered ship, train new crew members for both the Precursor ship and the Tobermoon and send a mission back to Earth, eager to know how the war had ended. Shortly before reaching Sol the little fleet was attacked by an unknown ship; Captain Burton, commanding the Earthling ship, intercepted the alien ship before it could damage the defenseless Precursor starship, but was killed in the short fight, leaving the genius young man in command