Have Space Suit – Will Travel (1958) – Kip Russell does not win a prize contest trip to the Moon, but he does win a consolation prize, a used space suit he reconditions as a summer project. He picks up a distress call and goes to help – and finds himself in the middle of interstellar and even intergalactic intrigue, forced to stand as a representative of the entire human race in the judgment of aliens.
For more information on Heinlien's Juveniles (written between 1947 and 1958) see our entry on Robert Heinlein's Rocket Ship Galileo, The Literary Encyclopedia profile by William Patterson, University of California, Santa Cruz
Patterson, William. "Have Space Suit - Will Travel". The Literary Encyclopedia. First published 10 November 2004
[https://www.litencyc.com/php/sworks.php?rec=true&UID=16275, accessed 21 March 2018.]