Sam Tucker is the deceased father of Cale Tucker in Titan A.E.. It is unknown why he never even spoke of his wife, so it is possible that he and Cale's mother either got divorced or he got widowed. He was the director and leader of the Titan Project, a top secret project that made the Drej fear of how humanity will succeed in their place in the universe, thus leading to a full scale invasion of Earth.
In the year 3028, Sam found his son, Cale, with his invention that broke while in the stream. Sam said they can fix it together, but not right away, for they have to get to the space port to evacuate Earth. Sam's partners, Tek and Joseph Korso, found them in time to get Sam and Cale to the space port. Tek has informed Sam of the Drej breaching the Global Defence System, but the Titan is ready for launch and awaiting Sam's arrival, while Korso informs Sam that their intelligence unit claims the Drej don't know the Titan's location, otherwise they would have been hit already. At the space port, Sam informs Cale that he's going on a different ship to go away for a while and Tek will look after him, much to Cale's sadness. Before leaving, Sam gives Cale a ring and said to him "As long as you wear it, there's hope". He kissed him in the forehead and said he will see him again and that's a promise.
The ship Cale and Tek got on got out in time, just as the Titan launched and exited Earth's atmosphere at hyper speed, before the Drej destroyed Earth once and for all. 15 years later, Korso found Cale at an asteroid belt called Tau 14, where Cale works at and stays with Tek. Even though Tek lost his eyesight over the years, can identify Korso by his voice. Korso took Cale's ring and gave it back to him after entering a code into the ring. The ring is revealed to be a storage container genetically encrypted to Sam and therefor to Cale. The ring is actually a map that reveals the location of the Titan, the only hope for humanity's survival. Later on in the movie, Korso revealed that the Drej found Sam at some point while Cale was growing up, but not the Titan, and the Drej killed him for refusing to reveal the location of the ship. When Cale and Akima found the Titan and got on board, Cale used his ring to activate the ship, but instead, activated a message left to Cale. Sam informed Cale and Akima that the Titan has the power create a new Earth, thus; having the DNA of all the plants and animals of the former Planet Earth. The ring could not activate the transformation sequence because in the escape from the explosion of Earth, the power cells were drained. He said all they need is to find a large amount of power and then the new Earth can be born.
"Once in a great while mankind unlocks a secret so profound that our future is altered forever. Fire, electricity, splitting the atom, at the dawn of the 31st century we unlocked another. It had the potential to change humanity's role in the universe. We called it the "Titan Project", and it was a testament to the limitless power of the human imagination. Perhaps that is what the Drej feared most, for it brought them down upon us without warning and without mercy. Cale, that day, the day that the Drej descended from the sky, the only thing that mattered was keeping you safe".