I had vague memories of watching this film on television with my parents when I was about ten years old. At that time I eagerly watched and enjoyed any sci-fi film that turned up on the three broadcast channels we received. Even to my uncritical ten-year-old self, this film seemed a bit "off." I particularly remembered the exterior shots of the projectile and how it obviously wasn't moving, and the ridiculous "meteors" that were just balls with flares attached to them.
I reacquainted myself with this film when TCM broadcast it recently. Like a lot of things from my childhood, it was worse than I remembered. Much of the film looks okay, and there are some interesting production design elements; the spaceship's period interior is intriguing. However, the film suffered from some mid-production budget cuts that drastically affected the special effects, which are Ed Wood-level quality. The film's abrupt ending also screams "sorry, we ran out of money."
Although other IMDb reviewers have criticized the film's storyline and acting, I found them tolerable. The "Power X" premise is a rather obvious reference to the Cold War arms race, but that was pretty typical of science fiction movies at the time; it's no more heavy-handed than "The Day the Earth Stood Still." Joseph Cotten and George Sanders were entering the last decades of their careers, but they are both competent and energetic here (although it is painful to see Sanders submitting to the indignity of being crammed into a plastic tube). Byron Haskin directs competently, as always.
It would be interesting to see a version of this film with updated special effects. CGI could be used to replace the effects shots and bring them up to the standards of the late 1950s. I think the film would be far more enjoyable that way; it has potential, but the dreadful special effects simply drag the entire movie down. Given the limited interest in the film, it probably won't happen, but it's fun to think about.