Think back: a lot of American rocket programs have had 'codenames' taken from Greek or Roman mythology. Hermes, Nike, Hercules, Atlas, Agena, Juno, Jupiter, Apollo, Gemini, Mercury...

I have no idea where "Redstone" came from. Ah, but Google reminds me of the Redstone Arsenal in Alabama. (paging through the historical photos that site brings you a bonus: V-2 launches from Peenemunde!)

I want to agree with Raoul, about Orion being a favorite, and maybe the second-most recognized constellation after the part of Ursa Major we call the Big Dipper. It figures in the sky-lore of every culture I've looked into, and it's always a man.

There might be another consideration, from a graphic design standpoint: that row of three stars. Notice how in both the Apollo and Orion program logos, Orion's Belt is emphasized. I have a feeling it's meant to imply "linear upward progression".