Set onboard the titular lunar outpost in the year 2003, the series starred Donald Houston as base director David Caulder, who is appointed to the position after the previous director is killed while returning to Earth. Co-starring are Ralph Bates as Deputy Director Michel Lebrun, Fiona Gaunt as base psychiatrist Dr. Helen Smith, and Barry Lowe as base technical section head Tom Hill.
The show was notable in part for its combination of strong, character-based writing and realistic spaceflight procedures.
- Absent Aliens: There are no aliens on the series, though are rumours about a lunar monster in "Behemoth".
- Artificial Gravity: Moonbase 3 is equipped with it.
- British Brevity: Only six episodes.
- Bus Crash: In "Departure and Arrival", Caulder is appointed to his position as base director after his predecessor Dr. Tony Ransome is killed in a shuttle crash caused by the pilot, Harry Sanders, suffering a mental breakdown while en route to Earth.
- Cassette Futurism: The series' depiction of the future generally falls into this trope.
- Explosive Decompression: A laboratory is destroyed because of it in "Behemoth".
- Exty Years from Now: 2003 was thirty years in the future at the time of production.
- French Jerk: Deputy Director Lebrun is a rigid and inflexible procedure nut who is often resentful of Caulder's position, believing himself to have been overlooked for the job by the higher-ups.
- Go Mad from the Isolation: Alongside various technical problems, the protagonists must deal with the psychological problems arising from the cramped, dangerous environment in which they live.
- The Great Politics Mess-Up: The Soviet Union still exists in 2003. It operates Moonbase 2, one of five lunar outposts (the others being operated by the US, Europe, China and Brazil). Furthermore, in the fifth episode "Castor and Pollux", it is revealed that the Soviets are on the verge of sending a manned mission to Mars and that their long-term goal is to launch a manned orbital flight of Jupiter using Mars as a springboard.
- In Space, Everyone Can See Your Face: The only major exception to the series' slavish adherence to scientific fact; the spacesuits in the series lack sun visors, which they would be equipped with in real life but which would have obscured the actors' faces and made it difficult for the audience to tell them apart.
- Jerk with a Heart of Gold: Despite his misgivings, Lebrun refuses to relieve Caulder of command when ordered to do so in the episode "Castor and Pollux".
- Multi National Team: The Moonbase 3 personnel are, unsurprisingly, predominantly British but there are scientists from other European countries such as France, Italy, Spain and Germany.
- Mundane Dogmatic: The show practically lived on this trope, as all the equipment was designed according to real-world technical specifications.
- Ooh, Me Accent's Slipping: Ralph Bates' French accent as Lebrun is variable.
- Our Graphics Will Suck in the Future: The computers were certainly more advanced looking than those used in 1973 - considering that they didn't take up a room - but there are no graphic interfaces.
- Shown Their Work: As mentioned above, the series went out of its way to portray the scientific and procedural details as accurately as possible. However, much like with Heaven's Gate, this ultimately backfired as the creators effectively sacrificed story for scientific accuracy, causing audiences and reviewers to refuse to accept any of it as "accurate" at all and creating a disquieting sense of claustrophobia that undermined the optimism of its premise, as pointed out by academic Peter Wright. Terrance Dicks later admitted in hindsight that he and Barry Letts had overdone that aspect of the series and consequently created too restrictive a format for themselves.
- The Shrink: Dr. Helen Smith is such a straight example of The Well-Meaning, But Dopey And Ineffective Shrink version of this trope that it borders on parody. She has empathy to beat the band but she really isn't very good at her job.
- In "Departure and Arrival", she does not treat the matter of Harry Sanders' erratic behaviour with the seriousness that it deserves - though Caulder found that she was not at fault in that instance. Things get worse from there.
- In "Behemoth", she failed to take any notice of Heinz Laubenthal's similarly erratic behaviour.
- In both "Achilles Heel" and "Outsiders", she is completely blind to the strange patterns of behaviour and relatively obvious warning signs displayed by two emotionally disturbed men as she is too distracted by her attraction to them. She does realise that they have problems but believes that they are of the kind that can be solved by her kissing them.
- United Europe: The European Community has far greater political authority than it did in real life at the time of production. There is frequent talk of the Assembly which controls the funding of Moonbase 3 and to which it is answerable. This does not seem to be an elected body. (The real life European Parliament was established in 1952 but did not become a directly elected body until 1979, six years after the series was made.) As such, it is probably more similar to the United Nations General Assembly than the modern incarnation of the European Parliament. Furthermore, the series correctly predicted that there would be a single European currency - which it calls the Euro dollar - by 2003. Unlike the real one, however, this fictional Eurozone includes the United Kingdom.
- Video Phone: A commonly used technology on both the moonbases and Earth in the series' version of 2003.
- Zeerust: The series takes place in 2003, a time when the United States, the Soviet Union, Europe, China and Brazil all have moonbases. A European manned probe to Venus is discussed at some length in "Achilles Heel".