It's a Choose your own adventure style book in space. There were certain scenes where you were a tyro in space and you had to train in an antigravity room with other newbies. A scene where you were in a ship by the rings of Saturn and you had to pick whether to go through them or around them. I also believe you get to Earth perhaps on a train. Not sure about the earth part but I am really sure about the space parts of the book. I read it sometime in the 90s I believe.
This is the Choose Your Own Adventure book "The Rings of Saturn", part of the Time Machine series. Tyros are trainee 'Time Astronauts'
Once tyros arrive at the academy. You still may be on Earth. This must be how you learn how to move in outer space. You begin learning how to think like an astronaut. “Move those legs and shake those arms!” Padgett shouts from above. You sink. Like a feather drifting to the ground. You can even go up. The other tyros gleefully leap into the pool.