This is as hard-core science-fiction as you ever find on TV, revolving around an insoluble problem in mechanics, and capping the always simmering tension between Vila and Avon which continued since the second episode of the first series.
Avon and Vila were Blake's 7's longest serving duo, Vila appearing in the first episode (and therefore the only character to appear in every episode) and Avon in every episode from the second on. This episode expertly levers the character flaws in the two anti-heroes.
I'm struggling to find other TV SF episodes to compare with this. Darmok and Jalad at Tanagra, from Star Trek TNG, Blink, from Doctor Who, perhaps the pilot episode from Lexx, but all of these are space-fantasy, not science-fiction in the way that Isaac Asimov, Arthur C. Clarke or William Gibson would have written it. When it comes to hard core mechanics, this episode is, to my mind, unbeaten.