A nice piece of science fantasy by an author well known for his science fiction. A scientist and three boys of high school age make a first trip to the moon- in time projected ahead. Lots of technical details about rocket ships, life on the moon, and so on make this juicy stuff for air-minded youngsters, and there's even some excitement involving a gang of Nazis hiding out on the moon, awaiting Der Tag. Claim to rival Jules Verne is a trifle immodest — but at that it's good enough yarning on its own.