(written from a Production point of view)
Franz Nicholas Bachelin (10 November 1895 – 26 May 1980; age 84) was the Academy Award-nominated art director who oversaw the set design for Star Trek's first pilot, "The Cage", after Pato Guzman dropped out to return to Chile.
The sudden departure of Guzman in early October 1964, left Associate Producer Byron Haskin seriously shorthanded, as Guzman's subordinate, Matt Jefferies, had his hands full with designing the exterior and subsequently the bridge of the new starship USS Enterprise, leaving the design work for other production assets, such as sets and props, up in the air. Haskin needed a replacement for Guzman fast. It was then that he recalled Bachelin, with whom he had worked previously, among others on the 1951 western Silver City. Being 68 at the time when Bachelin received the call from Haskin, Bachelin was actually already looking forward to retirement, but agreed to pitch in when Haskin promised that it only constituted merely a month's work and that he was home in time for the holidays, though that did not quite happen the way Haskin had led to believe. A veteran set designer, Bachelin's first responsibility entailed working out the layout of the bridge set in close cooperation with Jefferies, before moving on to work on the other sets for the pilot episode. Like his friend Haskin, Bachelin has taken a dim view on the interrupting on-set antics of Star Trek creator Gene Roddenberry, a novice producer, during the production of "The Cage". (The Making of Star Trek, pp. 101-102; These Are the Voyages: TOS Season One, 1st ed, p. 44)
Jefferies, by his own admission a practical "nuts-and-bolts" designer, approached his new superior's more artful designs for the other sets, beyond that of the bridge, with some skepticism, as he had admitted to decades later, "I had to come up with the construction drawings to actually build these sets, and my problem was in trying to figure out just what the hell Bachelin had done such a pretty painting about. I mean in terms of practicality, his paintings just didn't work; the construction crew would have gone out of their minds trying to build what he'd painted. At any rate, as I had said, I was a nuts-and-bolts man, so I took his basic paintings and used them in creating all of the ship's specific design work. I'm talking mainly about the bridge, the layout, the relationships between Enterprise crew members positions, the original instrumentations – all of this stuff required a massive amount of work." (Star Trek Memories, 1994, p. 57)
After the pilot was produced, Bachelin, having been an outside contractor, left and did not return for either the next pilot or the eventual series when it was picked up by NBC, his place being filled by Desilu Art Director Rolland M. Brooks. However, his work was later seen in "The Menagerie, Part I" and "The Menagerie, Part II" (from the unaired pilot reworked regular series episodes), and he received onscreen credit for it in the latter episode.
Along with Ernest Haller and friend Byron Haskin, Bachelin is one of only three credited production staffers born in the 19th century known to have worked on any Star Trek production, addended with the eleven Star Trek performers Judith Anderson, Morgan Farley, Richard Hale, Anthony Jochim, Felix Locher, Celia Lovsky, Leonard Mudie, Bill Borzage, Charles Seel, Abraham Sofaer, and Ian Wolfe.
German-born Franz Bachelin served as a fighter pilot in the imperial German air service during World War I. (The Making of Star Trek, p.101) After the war, Bachelin received an invitation from fellow former fighter pilot Hermann Göring to help rebuild the German air force (it eventually becoming the World War II "Luftwaffe"), which he declined, opting to study architecture instead.  Bachelin subsequently decided to emigrate in 1927 in the face of rising Nazism in his home country, a decision very much expedited by the circumstance that he, a Catholic, had in the meantime married actress/dancer Anita Hirtfield, who was of Jewish descent. After a brief stay in Cuba, he arrived in Los Angeles, USA, (alone, as his homesick wife returned to native Berlin, but who rejoined her husband in 1932 in Hollywood, very shortly before the Nazi party rose to power the year after, thereby, unlike most of her German family, escaping the Holocaust) where he was from 1928 onward working as art director at various Hollywood studios, conspicuously Paramount Pictures. 
Bachelin's many other art direction credits include a number of the classic Bulldog Drummond films of the 1930s, Billy Wilder's classic 1953 comic war film Stalag 17 (in which Bachelin made an uncredited and non-speaking – as he had never been able to loose his thick German accent (The Making of Star Trek, p.101) – background cameo appearance, ironically as an American POW), the 1954 adventure film The Naked Jungle (starring Abraham Sofaer), the 1955 John Wayne film The Sea Chase (co-starring Paul Fix, a fellow World War I veteran – one of only two known other Star Trek affiliated veterans, the other one having been Ian Wolfe), the 1957 drama Band of Angels (featuring William Schallert), the 1962 fantasy The Magic Sword (starring Gary Lockwood), and the 1965 sci-fi B-movie Village of the Giants. Bachelin earned an Academy Award nomination in Best Art Direction-Set Decoration for the 1959 adaptation of Jules Verne's science fiction novel, Journey to the Center of the Earth. He shared the nomination with fellow art directors Herman A. Blumenthal and Lyle R. Wheeler and set decorators Joseph Kish and Walter M. Scott.
While he had intended to retire after Star Trek, Bachelin made three more motion picture contributions afterwards, two 1965 films and the 1966 two-part pilot episode for the legendary series Batman, featuring Star Trek: The Original Series guest star Frank Gorshin in his Emmy Award-nominated role as The Riddler, becoming his last recorded motion picture industry work.
Bachelin died in Pacific Palisades, California in 1980, aged 84, and was survived by his daughter Inez Storer, a well-known Californian art paintress and mixed-media artist. Her father incidentally, had taken up art painting as well after his retirement from the motion picture industry. 
- The Making of Star Trek, September 1968
- Star Trek: The Original Series Sketchbook, May 1997
- These Are the Voyages: TOS Season One, August 2013