A solution to the prohibitive cost of producing vehicles for further space explorations is Tom Swift Jr.'s new goal. But the success of the young scientist-inventor's project is threatened by the wily Li Ching, a renegade scientist. Banished from his native land because of rebellious acts, Li Ching is now the leader of a ruthless group intent on pirating scientific secrets.

But Li Ching and his nefarious confederates are only partially responsible for Tom's troubles. Olin Whaley, an unscrupulous international criminal, proves to be a second formidable obstacle.

Despite the ever-present threats of sabotage and piracy, Tom and his friend Bud Barclay are soon taking Tom's latest invention, the Space Kite -- a two-man craft for training future space pilots -- on its test flight. The experiment turns into a harrowing experience when the boys are nearly marooned in outer space.

Undaunted by the failure of the Space Kite, Tom quickly discovers the defect and decides to build a larger craft, the Cosmic Sailer. Certain that he has found the key to economical space explorations, the young inventor still has to conquer the sinister forces working against him. How Tom and the Cosmic Astronauts meet this challenge will keep the reader taut with suspense.