FLYING DISKMAN OF MARS (1950)

Martian invader, Mota, attempts to conquer the Earth as Mars is worried about its use of new atomic technology. The Martians consider that it would be much safer, and beneficial for both Earth and Mars, if the Martians were in charge. Mota, having been shot down by an experimental ray gun, blackmails American scientist, and former Nazi, Dr. Bryant, into assisting him and hires some criminals to be his henchmen.
Kent Fowler, the private pilot who shot down Mota with Dr. Bryant's ray gun, gets caught up in these events while working security for atomic industrial sites.