The very first major science fiction series for adults on radio was Mutual Broadcasting System's 2000 Plus (1950-1952). An anthology program, 2000 Plus used all new material rather than adapting published stories. Just one month after its premiere, NBC Radio began airing(1950-1951), which dramatized the written work of such young writers as Ray Bradbury, Robert Heinlein, Isaac Asimov, and Kurt Vonnegut. In 1955, NBC relaunched Dimension X as(1955-1958), drawing from stories that had been published in the two most popular science fiction magazines at the time:and 17 of 30 episodes of 2000 Plus, all 50 episodes of Dimension X, and all 125 episodes of X Minus One are available for free download as individual mp3s from the Internet Archive.The shows are also available in free zip file compilations:Direct link to zip file: 2000 Plus Download pages: Dimension X and X Minus One