There's a space station orbiting the earth (complete with artificial gravity because the circular station revolves) and a space ship being constructed to rocket to Mars.
Got this DVD a oouple of days ago. It's a lot of fun.
No African-Americans in this space crew in 1955, but there is a Chinese American (played by Benson Fong).
The biggest star in the movie - although only a co-star at this time, is Ross Martin, of Wild, Wild West fame.