This note contains spoilers for the book.

Ended up with another copy of this in an SFBC omnibus of 4 juveniles. So of course I had to read it.

This remains grand fun.

NERVA might, if the radiation could be tolerated, have actually made this kind of casual jetting around the solar system semi-possible. Chemical rockets really don't do the job, even today.

One thing Heinlein consistently gets wrong is how far radio reaches through space. Nothing there to interfere with it, after all. We're still listening to Voyager, out beyond the tropopause, and it's transmitting with 35-year-old transmitters and somewhat reduced electrical power and a rather small antenna. Of course, we can only hear it with some of the biggest specialized receivers on the planet. But still.

Anyway, it's a heck of a romp. We get to see Luna, and Mars, and the Hallelujah node in the asteroids. We get three viewpoints on most things, Roger and Hazel and the twins, and they often disagree, so it's really three. It's an encouraging picture of an expanding species.

I'm not at all clear there's really economic justification for the expansion humanity is going through; I suspect a lot of the pioneers are misfits, there to get away from other places. So long as they can make some kind of a living, they'll be happy.