Vintage paperback

Mike Mars is chosen for Project Quicksilver, but suspicion of sabotage puts the X-15 rocket and his life in danger.

Mike barely escapes with his life when the Starfighter jet he is piloting to Cape Kennedy is fired upon-by another American plane! But that's just the beginning of his danger-filled efforts to complete a successful test flight of his space capsule. For someone-or something-was determined to destroy Project Quicksilver, and Mike's life along with it!

Book #6 in series finds Mike Mars in trouble and stranded on a polar ice cap. He mission is to prevent the Russians from discovering the secret of the Blue Scout rocket!