The Mushroom Planet series by Eleanor Cameron.  Two boys decide to build a rocket.  Mom packs them a lunch and says, “Have fun and be careful!”  They land on the Mushroom planet and meet Mr. Bass.  Pure old-fashioned fun, with no messy technical details to get in the way.  

Astrotwins series by Mark Kelly.  Project Blastoff and Project Rescue.   Written by real life former astronaut and twin.  Adventures about twin boys who decide to build a real rocket – and launch themselves into space.   

The Lion of Mars by Jennifer Holm.  Life on Mars as part of an Earth colony takes a scary turn when all the adults get sick and communication between the settlements is lost.  It’s up to Bell to figure things out. 

Moon Base Alpha series: Space Case, Waste of Space ... by Stuart Gibbs.  In 2041 on Moon Base Alpha, thirteen-year-old Dash must solve the mystery of how Lars was poisoned before the base loses oxygen, forcing the colonists to return to Earth. 

Full Cicada Moon by Marilyn Hilton.  Mimi Yoshiko Oliver dreams of being an astronaut as she follows the Apollo 11 moon mission.  But in 1969, being a girl, being half black Japanese and not especially interested in the “domestic” sciences causes her to be more an outcast than anything.   

The Jamie Drake Equation by Christopher Edge.  Jamie has a close encounter with an alien who tells him his father, an astronaut on a mission at the International Space Station, is in trouble and needs Jamie's help. 

Cosmic by Frank Cottrell-Boyce.  Liam Digby is so unusually tall that people think he is an adult, which leads him to compete against adults for a chance to go into space.  Then things go hilariously wrong. 

Stowaway by John David Anderson.  An interplanetary war has left Leo, his brother and father determined to leave Earth.  But their spaceship is hijacked, his father kidnapped and Leo stranded in the middle of space.  Will stowing away on the mercenary pirate ship be successful or disastrous? 

The Last Cuentista by Donna Higuera.  As a deadly comet heads toward Earth, a select group of families is preparing to leave the planet to colonize another planet.  Petra’s family is among them, but when she finally awakens hundreds of years after an artificial coma, only the children have survived, and she alone remembers the past on Earth.  Will she be able to use her power as a a cuentista (storyteller) for the new society?