Long before Creator/RodSerling created ''TheTwilightZone'', probably the best science fiction and fantasy program made, there was ''X Minus One'', the radio drama which ran during 1955-1958 on the NBC radio network. Using material supplied by the two major science fiction magazines of the day, ''Astounding Science Fiction'' and later ''Galaxy'', the show produced a weekly radio drama involving science fiction, aimed at adults. (One of the program's sponsors was Pabst Blue Ribbon beer.)

As noted on Wiki/TheOtherWiki, the show opened with the same teaser:
->Countdown for blastoff... X minus five, four, three, two, X minus one... Fire! [Rocket launch SFX] From the far horizons of the unknown come transcribed tales of new dimensions in time and space. These are stories of the future; adventures in which you'll live in a million could-be years on a thousand may-be worlds. The National Broadcasting Company, in cooperation with Street and Smith, publishers of ''Astounding Science Fiction'' presents... X Minus One.

Later they would use ''Galaxy'' in place of ''Astounding''. Some openings did not include the word 'transcribed'.

Each week, a new story, taken from either Astounding or Galaxy, was performed as a radio drama (or comedy) in which the material was played straight for an adult audience, as opposed to typical 1950s science fiction (especially science fiction movies or TV shows) which either trivialized this type of story (as in the case of most "bug eyed monster" style low-budget "earth is being invaded by monsters [[MarsNeedsWomen (or) Martians]]" films) or targeted it for juveniles (e.g., ''Series/CaptainVideo'').

For its time, the show was somewhat groundbreaking in that it covered science fiction as serious fiction directed to adults. Story lines included characters with gambling and addiction problems, criminal tendencies, and even one case where a space ship piloted by a computer with a female personality, was being "made love to" by its "robot boyfriend."

[=MP3s=] of the show can be downloaded for free from the Internet Archive http://www.archive.org/details/XMinus1_A , or can be purchased on CD for $10 for the low quality set or $25 for the high-quality set from the "official" http://www.xminusone.com/text/showlist.htm website, it claims to include all 195 episodes.
You can also listen to episodes on YouTube.
!!The various episodes of the series supply examples of
* DoubleDontKnow: One episode had the character using this trope
* DownerEnding: Many of the shows ended up with a bad result for the protagonist.
* GenreAnthology
* SpiritualSuccessor: X Minus One is this to ''Radio/DimensionX'', which aired on NBC radio from 1950–1951.
* WorthlessYellowRocks: A protagonist got mixed up in a time-traveling get-rich-quick scheme by going to the past and investing in stocks that would rise and property loaded with a type of mineral that the seller told him had interesting scientific qualities but was basically worthless—uranium.