Cosmic by Frank Cottrell Boyce

Check out a book trailer for COSMIC, the new novel from Frank Cottrell Boyce, the bestselling author of MILLIONS.

Liam is an unusually tall (and bearded) 12-year-old who often gets mistaken for a grownup. After conning his way onto a secret space mission as the only adult chaperone for a group of kids, Liam has to use both his kid-ness and adult-ness to save them all from disaster.
(From the YouTube description)