During principal photography, the first English Film Festival was being held in Berlin. Various British film dignitaries were brought to DEFA to meet the director, Prof. Kurt Maetzig, and watch as some scenes were being shot.
In the 1962 USA release version, on the film soundtrack, in a scene in the control room of the Kosmostrator rocket, we hear a music track titled "In Outer Space" from Destination Moon (1950) by Leith Stevens, and later in the movie, in the scenes of eerie destruction of the Venusian city, we hear a music track titled "Metaluna Catastrophe" from This Island Earth (1955) by Herman Stein. Both of these uses of music were uncredited and unlicensed, and unauthorized by the copyright holders.
In the original German version, "Brinkman(n)" isn't American but East German, and the "Durand" character is a Soviet cosmonaut by the name of "Prof. Arsenjew" (Arsenyev), "the man who steered the first rocket to the moon"!
The German version contains a reference to one of the professors having his career stalled when he was thrown out of the university by the Nazis. Director and co-writer Kurt Maetzig had his career stalled by the Nazis because his mother was Jewish.
At one point DEFA intended to establish a co-production with a French company for financing and scriptwriting. Part of the plan was to use French actors Yves Montand and Simone Signoret. However, Communist government officials disapproved of DEFA's pursuit of Western partners.