For fans of serious science fiction, there aren’t too many options on TV these days. Despite this age of peak TV and the glut of original programming that has yielded some extremely popular genre series, including Game of Thrones and The Walking Dead, science fiction has struggled to find a foothold, and most of what exists is essentially contemporary in setting (think Westworld or Person of Interest).

For the kind of classic sci-fi built around spaceships and interplanetary relations, there’s really only one choice: The Expanse.

Fortunately, it’s a good choice. The series, which wraps up its second season on Syfy this week, was recently nominated for a Hugo Award — science fiction’s top honor — and even though its ratings are less than stellar, Syfy has renewed it for a third season.

A lavishly produced, politically complex drama about interplanetary rivalries as humans reach beyond the solar system, The Expanse is, by nearly any measure, one of the most ambitious science fiction shows ever made. But it also helps to illustrate why the genre has had such a difficult time flourishing on the small screen in recent years, and why it’s so hard to make great science fiction TV.

Science fiction is hard to produce well on a typical TV budget

The first obstacle any science fiction show has to reckon with is the budget. There’s a built-in visual appeal to most any science fiction world. From the sprawl of futuristic urban transportation systems to cramped spaceship interiors to the particulars of fashion, weaponry, and computing, most imaginary renderings of what the future will look like are inherently interesting. But typically, they’re also incredibly expensive to produce, because visualizing the future inevitably requires custom-built sets and props and complex computer-generated effects.

That makes science fiction a great fit for feature films, where it’s common for studio-backed sci-fi properties to spend well in excess of $100 million on a movie. For a two-hour film, that comes to nearly $1 million per minute of screen time. In contrast, few TV shows even come close to spending $100 million per season, and full-season budgets are often less than half of that: The production budget for Netflix's Marvel comics shows is reportedly around $200 million for five seasons spread over 60 episodes, and the first 10-episode season of Westworld cost about $100 million. In any case, that money has to cover 10 or more hours of screen time. This means expensive sets and effects can only be used sparingly, if at all.

(This is a problem for fantasy series, too, of course. But fantasy at least has the advantage of being set in something that resembles the ancient past, which means producers can expect lots of scenes set in natural environments with nothing more expensive than a few horses and some sword props. Game of Thrones, one of the most lavish and expensive shows on TV, reportedly costs somewhere between $6 million and $10 million per episode.)

You can see this dynamic at work on The Expanse. Based on a series of books by James S.A. Corey, the pen name of authors Daniel Abraham and Ty Franck, the show is set roughly 200 years in the future, after humans have colonized the solar system. There are three distinct factions — Earth, Mars, and the Belt, led by a loosely organized, quasi-terroristic Belters rights organization called the OPA (Outer Planets Alliance) — all of which are vying for political influence. The spaceship and settlement sets are impressive, but most are used repeatedly in order to wring maximum value out of each location. The show boasts consistently impressive special effects sequences, like the Martian power armor battle that opens the second season — but there’s also an awful lot of diplomacy and negotiation going on.

Much more than feature films, TV science fiction almost always has to be built around conversation rather than action set pieces or otherworldly visual spectacle. That’s not to say that space battles and shootouts are off limits entirely; but creating 10 or more hours of science fiction TV inevitably necessitates a lot of scenes of people standing around and talking to each other.

Science fiction TV has to explain everything from the ground up

That brings us to the next challenge for science fiction television: It has to explain almost everything. A contemporary show, or one set in the recent past, can take an awful lot for granted — everything from how governments work to what the characters eat to how people get around. All of this material is assumed when a show is set in the same world that viewers live in every day.

A future-set show like The Expanse, on the other hand, has to explain everything: how people living in space get access to air, food, and water, how the economy works, and what sort of governments are in power.

The show’s three-way power struggle drives much of its story, which means that the complex political dynamics between Earth, Mars, and the Belt have to be explained. The show’s politics are pretty fascinating; as Tufts University professor Daniel Drezner recently wrote at the Washington Post, it might be the best show about international relations on TV right now. But it’s still a heavy storytelling lift.

Beyond politics, The Expanse also has to work through basic questions about the nature of physics and technology. For example, the story requires characters to move throughout the solar system far faster than any currently known technology would permit, so a subplot in one episode this season was devoted to dramatizing the invention of the “Epstein Drive,” a propulsion system that allows for ultra-fast travel without gravity-related side effects that would otherwise turn a body into mush.

Even basic modes of communication like accents and body language are potentially unmoored from the everyday expectations of a typical viewer. The Expanse’s Belters speak in a jargon-heavy, accented slang, and although it’s downplayed somewhat in the TV show relative to the books, they often communicate via large arm gestures, which Belter culture developed because they spent much of their lives in spacesuits that made facial expressions difficult to read. To account for this, the producers hired a choreographer who, according to executive producer Mark Fergus, “developed a comprehensive video-dictionary of Belter hand-speak for the actors and producers.”

In novels, these sorts of in-world mechanisms can be explained directly to readers by the author or the narrator. In a science fiction TV series, all of this information — cultural, physical, political, and economic assumptions that would otherwise go unspoken and unquestioned — has to be built from the ground up and clearly communicated to the viewer without getting bogged down in clunky exposition. It has to be dramatized, frequently in scenes involving characters who already know what’s going on and wouldn’t naturally explain it to each other. And it has to do all of this in addition to fulfilling the requirement of any good scripted show: to tell an engaging story with compelling and believable characters.

The Expanse had the advantage of a preestablished world to fill out

On The Expanse, you can feel the producers straining against these challenges, and there are times when the seams start to show. Some of the space station interiors feel slightly underpopulated, as if the show couldn’t quite afford to fill out the big living spaces. The insides of the various spaceships and space-based habitats all seem to work from similar design concepts, as if imagined by a single designer. Some of the dialogue verges on being expository, and yet the nuances of the series’ three-way politics still may not always be clear to those who haven’t also read the books.

Overall, though, The Expanse handles these challenges exceptionally well, balancing political backstory, technical details, and cultural world building with a broad cast of well-developed characters and a sprawling narrative about a solar system–wide fight for resources and power.

The show’s handling of space travel may be the most impressive thing about it: There’s no artificial gravity, and spaceships have to fly plausible trajectories that account for the gravitational pull of planets. It’s a series that takes the technical challenges of life in space seriously. And it does it all this within the confines of a television budget, while managing to be one of the coolest looking shows on TV.

One reason it all works so effectively is that The Expanse’s world was largely built before it was developed into a story. According to Ty Franck, one of the writers behind the books and an executive producer on the show, The Expanse began as a pitch for a massive online role-playing game, which never came to fruition and was eventually converted into a homemade tabletop RPG. Franck’s co-author, Daniel Abraham, was one of the players.

“After about the third session,” Franck recently told Glixel, “[Abraham] kept looking at my giant notebook, and he would say things like, ‘Since every company out here in the Belt has their own scrip, what does the economy look like? How does the money exchange work?’ So I would explain it to him and he would say, ‘If we're in these rock tunnels, wouldn't the rocks be really cold? What do the tunnels look like?’ I would explain that to him, and he saw that it was all in my book, and finally he said, ‘You've done all the world-building that people do for novels. Why don't we just write a novel out of this?’ I was like, ‘Yeah sure.’"

In other words, The Expanse’s writers aren’t just making up the world as they go, adding convenient technologies on the spot. Instead, they’re populating a complex preexisting world with people and conflicts, rather like a more conventional show in a contemporary setting.

That may be the biggest reason The Expanse is so effective at solving the challenges of sci-fi television: It doesn't always act like a science fiction series that has to laboriously explain itself to its viewers. Because it's working from a fully fleshed-out world, it can do what shows set in our own time do and assume a degree of familiarity with how everything works. The characters on The Expanse all know how their world operates already, and that allows the audience to extrapolate on their own.

The Expanse obviously is not a contemporary show, but in many ways it functions like one, allowing it to develop its world without working too hard to justify it. Thus, it doesn’t just reveal the challenges of making great science fiction television — it also shows how to solve them.