Brad Murray, via the excellent At-Will 4e IRC channel, hosted by Quinn Murphy. You might have heard about him recently for his first Worldbreaker, Etherkai, which I will be reviewing soon. Diaspora is a more "gritty" approach to science fiction roleplaying, which is, to say, very unlike other new(ish) sci-fi RPGs such as Eclipse Phase. In the introduction to the book, the authors mention that they wanted to create a Traveller-style experience, using the FATE system, and updated for modern players.
Alas but Traveller is a game which I have never had the joy of playing, so I can only speculate as to the relative faithfulness of Diaspora to that kind of experience, but I have had a bit of experience with FATE, albeit only theoretically. Meaning, I've read a lot more books based on FATE than I have any sort of material concerning Traveller. FATE is ultimately a very modular sort of system, concerning a slightly nebulous "core" of mechanics, which then can be dressed up with all sorts of other mechanics for flavor and ease of use. This is a strength of the FATE system, in my opinion, and one of the reasons why I keep returning to it. While Spirit of the Century, the Dresden Files RPG, Diaspora, and Strands of Fate all use the same core mechanic, in other words, they nevertheless end up "feeling" like very different games because of the peripheral details.
The biggest problem with FATE, however, is the learning curve. It is a very abstract system at first, and it uses a healthy supply of its own jargon which can feel a little overwhelming to the new player. Also unfortunately is the fact that FATE books are written, by and large, by authors who already presuppose that readers will, like themselves, be able to parse that jargon. I tried to read the Diaspora book as agnostically as I could, assuming ignorance of the system, and that is where I believe the book's primary weakness lies: it does, in my opinion, an inadequate job at explaining the jargon. In the chapter on mechanics, it explains some of these terms like "tagging" or "compelling" aspects, or invoking "maneuvers," but does not explain fully the methods and ramifications of those things. For instance, a new player might ask "do the player characters get to see what Aspects their enemies possess?" or "can enemies just as easily compel Aspects on the player characters as vice versa?" To the authors' credit, these sorts of issues become less pressing as the book goes on, and the reader can absorb more information about how the system works from context, but at this point early in the book, a sketchy overview could potentially serve as a hurdle for a prospective player. One has to imagine, though, that this was intentional: expending too much time and effort on the abstract mechanics early in the book would probably also have the effect of making the game seem trudging and tedious, and it makes for a better read without dwelling on minutiae. It really isn't until the chapter on combat that the Aspect system really becomes clear.
That all being said, on to the good bits. Diaspora is set in a universe which assumes that there are weaknesses in the fabric of space that, when compelled (usually by artificial means), open a sort of wormhole to another solar system that is an indeterminate distance away. These weak points, which are called "slipknots" in game, are the key feature to the entire game universe, and are what enables a "diaspora" to become possible. Namely, one creates a "cluster" of systems linked by "slipstreams" that could be neighboring solar systems within the same sector of space, or may just as easily be systems in another galaxy billions of light years away. Travel between them via slipstream renders distance, in this special case, meaningless. However, points not linked by slipknots still suffer under the burden of sub-relativistic speed.
Diaspora also assumes that human civilization can only advance so much before imploding in on itself; therefore, technology is dangerous, and systems which are at the "T4" (pinnacle of advancement) stage, are also on the verge of collapse (or may have already collapsed), and have strange consequences. As the book describes it, "[T4 civilizations] are on the verge of collapse—they are about to unfold one or many failed dreams, spiraling into a transhuman ascension indistinguishable from a multi-billion death disaster." Heavy stuff. Diaspora therefore assumes that most (playable) civilizations are in the T2-T3 range, which is to say that they are "masters of their domain" in that they can exploit slipstream technology and travel between systems. For perspective, the ratings go from -4 to 4, and present-day earth is T0. Given what the authors describe in the introduction, this "limit" on technological advancement is intentional as a key feature of the game universe, as they want to constrain the game within the bounds of "gritty and dangerous," and steer far clear of the Star Trek vision of the future.
The default type of player character by and large seems to be human characters, but it does allow for alien characters, alien civilizations, and alien technology. Pair a T4 system with an ancient alien civilization, for instance, and you have the opportunity to create a situation like Ivanova's encounter with the Walkers of Sigma-957 in Babylon 5. Or have an encounter with one of the most distant systems of another player's cluster, and reenact your favorite episode of Star Trek: The Next Generation (hint: it's Darmok).
The book rounds itself out at the end by providing good examples of how to start a story arc, what sort of interactions one might expect between cultures, and, to quote the title of the last chapter, "making it work." This is far and away the best chapter in the book, and it was only at this point for me when the game stops being an abstraction and really does feel like something that is playable. My only regret is that while there were many examples of spacecraft (which was helpful), there were not really examples of player characters. What I would have liked to have seen is, just like the sheets for example spacecraft, to have a layout of around the same number of characters, which could be used as PCs or NPCs, or just hashed out examples of what a character sheet looks like after it's all filled out.
Additionally the combat rules regarding range were a bit baroque, but I suspect strongly that once one actually tries to play it out it will become a lot more obvious. But that's just a minor complaint.
Overall, it seems that Diaspora is a very flexible system which allows for a very wide variety of gameplay, from harrowing paramilitary thriller to Firefly-esque space cowboy hijinx and anything in between, and I look forward to eventually getting to test it out with a group of real people. One of these days.