The important thing to remember is that there's no correct running order for Space: 1999. It's the nature of the beast. Unlike modern shows, where events take place in a specific order and "story arcs" continue from episode to episode, the film series of the sixties and seventies were deliberately designed to have as little continuity between episodes as possible. This was done to make the shows more saleable - broadcasters knew they were buying a series of (largely) self-contained films, which gave them much more flexibility in the way they could transmit the show; episodes could be dropped, switched around or preempted without any difference being discernable to the viewer. [Well, that's the theory. It's blatant nonsense however - in the first American screenings, Dragon's Domain was shown as the second episode. Even a half-asleep viewer's going to notice that the episode opens 877 days after the Moon left orbit, and wonder what the hell's been going on for the last two and a half years!] So, the show is designed to have a definitive first episode, to establish the format and introduce the characters, with all subsequent episodes being interchangeable. Part of the sales package would be an instruction to open with Breakaway, after which it would be up to broadcasters to sort out a running order - or more likely to put the episodes out completely at random.
What this doesn't do is take note of the way the series develops. The producers may have been aiming to have interchangeable, continuity-free episodes, but with the best will in the world, subtle changes are going to work their way into the show. Characters will start to be written differently once the writers see how the actors are playing them. Ideas and concepts that didn't work out are quietly dropped. The thinking at the time was that such differences were small and wouldn't be noticed by the casual viewer. [This seriously underestimates the intelligence and observation of the audience, of course, but it really does seem as if tv executives thought their consumers were idiots.] All they had to avoid was doing something irrevocable, like killing off a major character, as they couldn't guarantee that other episodes featuring that character wouldn't be screened later. (They can kill off Commissioner Simmonds in Earthbound; since the only other episode he appears in is Breakaway, there's no way you can show those out of sequence. But the only other major characters we see dying are single episode guest stars; by the same token, we never see what happens to Jackie Crawford after Alpha Child.) [I'm reminded of the character of Mr Leslie in Star Trek - he's not one of the main players, but he's a named and recognizable character who features in a huge number of episodes - he's killed off by the alien creature in the episode Obsession, yet is seen back on duty several times subsequently. This would have seemed even worse once the episodes were being shown in random sequence in syndication.]
So, is there a "right" order in which to show the series? It's quite common these days to place the episodes into production order. This is how they're arranged on the DVDs for instance; and it's the order in which the BBC (mostly) showed the first series. Now, one might think that this would take account of those subtle changes I talked about - that's true to an extent, except for that fact that it's not a progressively linear development, as multiple scripts were being written and re-written at the same time. (Take Matter of Life and Death - it was produced second, but there's just as much dialogue suggesting it's not the second episode as that suggesting it is...) Then again, there are some fans who argue that the production order makes more sense of the changes to the set layouts. For instance, the basic design of Main Mission changes as the series goes on: the lighting behind the translucent panels changes colour; the steps along the wall leading up to the windows disappear; and Kano acquires his own rotating desk in the centre. Well, I seriously have to ask: should we allow what must have been practical production decisions to dictate our understanding of the narrative? Let's think about this for a second. What that's effectively saying is that, in the midst of their desperate struggle to survive, Koenig got the decorators in to completely remodel the room - a huge control room sitting at the top of a tower overlooking the base. Is that really credible? Surely, it's far better to overlook what amount to a few visual continuity errors? (I would guess they took the steps out to make the set easier to work with - perhaps to create some more floor space for the cameras and actors to move in. As for the lighting panels - I think constant changes in colour make more sense within the context of the series, as a deliberate attempt to break up the sterile look of the base and prevent claustrophobic reactions in the personnel.) There are other more aesthetic and narrative reasons why production order is unsatisfactory: to take a single example, it means watching War Games andThe Last Enemy - two episodes in which the base comes under heavy military attack - back to back. Any responsible broadcaster would separate these episodes to stop it looking like the programme is repeating itself.
When I started watching the series, courtesy of the ITC video releases, I had no idea what the production order was. All I could tell then was that the order in which the episodes were being released was clearly wrong. So, because I'm of that sort of mind, I found myself trying to work out the "proper" running order.[Even before I'd seen all the episodes! It's like a sort of intellectual jigsaw puzzle - you move the pieces around to see what fits best, then when something new comes along and spoils your theory, you move them around some more. It's an organic process, but it does mean that once finalized, the sequence sets in stone in my mind. That's one reason why I've stuck with it for this site - although I do genuinely believe it works to enhance the viewing experience.] For the first series, this was based on what little continuity there is in the show - lines of dialogue, and other hints that certain events might occur later than others, changes in the characters' attitudes, and so on - but overall, the aim was just to come up with the most logical and watchable sequence of events. The second series was relatively easier to order, since most of the episodes are given a date at the beginning. This means that the sequence is much closer - though not identical - to the production order. (As for the two episodes without dates, their approximate positions can be inferred from the dates given in the episodes produced around them.) Of course, going with the stated chronological order is not without its own continuity problems, but I'll examine those in the episode analyses. [You have to wonder though why they bothered to put such obvious dates on the second series - it flies in the face of the way film series are supposed to work. You can be sure that the episodes weren't ever screened in that order (although the BBC rerun in 1999 almost managed it...) - so the alert viewer would have seen the Alphan's chronology jumping about.]
So, to go back to the first series: in creating my running order, I noticed that the episodes divide roughly into two categories - those where the Moon arrives at a new planet, and those where the Alphans are visited by aliens or encounter various space phenomena. Since one of the common criticisms of the show is the perceived regularity with which the Moon encounters a new planet, it made sense to alternate the two different types of episode - that way, they wouldn't seem to arrive at a new planet every week. (In actuality, it's not every week, as the series takes place over a much longer timescale.) This may create some artificial and arbitrary shuffling of episodes, but I felt it was important to maintain this balance. At the same time, I made sure that episodes dealing with similar concepts were moved apart in an attempt to keep things fresh. My third decision was to try and suggest a progression further into the depths of the universe - which meant that episodes that retained some link to Earth (whether it be aliens who had observed our world, or discovering lost Earth expeditions) would be placed in the first half of the series, with the more exotically strange episodes later on.