(written from a Production point of view)
Norman Richard Spinrad (born 15 September 1940; age 78) is a science fiction writer who has occasionally contributed episodes to television, most notably "The Doomsday Machine" for Star Trek: The Original Series, an episode that garnered him a 1968 Hugo Award nomination in the category "Best Dramatic Presentation", which he shared with Marc Daniels.
Spinrad wrote an article in Cinema magazine concerning current science fiction film projects, in which he mentioned Star Trek favorably, even putting it higher than Stanley Kubrick's 2001: A Space Odyssey, which resulted in Gene Roddenberry writing a letter of thanks to the young writer, and inviting him to pitch ideas for his series. After an unsuccessful first pitch (a story concerning an ancient mental probe creating beautiful illusory women, deemed too similar to "The Cage", "Mudd's Women", and "What Are Little Girls Made Of?"), Spinrad came up with the idea of the "Planet Eater", which sold and was later developed into "The Doomsday Machine". (These Are the Voyages: TOS Season Two)
Another script he wrote, entitled "He Walked Among Us" was not filmed, due to his own request, after producer Gene Coon rewrote it to a comedy.  Recently Spinrad reconfigured the story with original characters and settings, and posted it as an on-line novel.
For the aborted Star Trek: Phase II, Spinrad wrote a script entitled "To Attain The All."
Spinrad was set to direct "He Walked Among Us" as an episode of the fan film series, Star Trek: Phase II (formerly Star Trek: New Voyages), but those plans were scuttledby CBS's assertion of copyright on the original script.