Todd Baker is the son of NASA astronaut Colonel Peter Baker and grows up with a love of amateur rocketry. It is announced that Colonel Baker is to go up on the Endeavour space shuttle mission. But before this can happen, he is killed when one of his and Todd’s model rockets blows up. Afterwards, Todd’s mother moves to California to live with Todd’s grandfather, the former Mercury astronaut Gus Baker, who now runs a NASA museum. Todd starts to withdraw at school. But then Gus is offered an old Redwood (one of the rockets that launched the Mercury missions) at discount rates. Todd and schoolmate Sarah Miller come up with the idea of doing a class science project about the restoration of the Redwood to working condition. They start rebuilding the Redwood, naming it Mercury 10, and are later joined by the rest of the science class. However, NASA intervenes and closes the project down as being too dangerous. But then the Endeavour is hit by a meteorite shower and trapped in orbit. NASA come back to Todd and Gus, wanting to launch the Mercury 10 because it is the only spaceworthy vehicle available to reach the Endeavour in time.