Author's note: Just a headcanon on who voices the countdown, and speculation that it is something the Tracy Brothers hear each time they launch.
The first time Jeff heard the countdown after he came home, he had chills running up and down his spine.
Grant Tracy had done that countdown as a surprise when Jeff and Lee had launched on their mission to Mars. The recording was moderately famous, and his taciturn father had refused any number of offers to lend his voice to anything media related afterwards. That countdown had been a message of love and pride to his two boys; Grant may not have been Lee's father in blood, but he had taken one look at the scrappy bruised boy Jeff had brought home with him from school one day and, well, there was no doubt where Virgil's soft heart had come from.
His mother had chuckled thoughtfully at his reaction.
"The boys couldn't think of a better memorial to you and him. Grandpa sending them off to save the world."