The appearance of science fiction in the pages of SPICY ADVENTURE STORIES in the early 1940's was mirrored by the same appearance in ACTION STORIES at the same time.  ACTION STORIES, which was an adventure pulp without a spicy slant, also began to run science fiction stories and covers in the early 1940's.  Clearly, there must have been some factor at work which led the editors of two different adventure magazines to believe that the inclusion of science fiction would help their sales.  In both cases, it appears to have been an unsuccessful experiment that was dropped after a short period of time.