I'm trying to find a roleplaying game system that lends itself to hard science fiction. To quote another stack exchange user, "Hard science fiction is defined by scientific rigor." I'm looking for something that you could, for example, play out Rendezvous With Rama. The adventure would be space based and include travel in a slower than light vessel.

A game world isn't required, only a game-system. I have developed my own setting, I just want a ruleset to support it.

The system preferably would be skill based. Mechanics for missiles or simple ballistic space combat would be useful but aren't required. Lots of physics would be troublesome as well. The system shouldn't rely on fantasy elements to balance out characters. Psychological "mechanics" would be an interesting add-on.

Aside from diaspora, eclipse phase and traveller, are there any other game systems that might lend itself to that play style? A lesser well known game system?

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    \$\begingroup\$ As mxy says in his answer, we don't know what you're imagining in a rules system that would qualify it as "scientifically rigorous." You say, lots of physics would be troublesome, so what are you looking for? Based on your current description I could recommend Fate Core because it's skill-based with psychological mechanics, no mandatory fantasy elements, and it will adhere to physics if you order it to do so via narrative positioning during campaign setup. But Fate Core is not scientifically rigorous in any way except what the players bring to the table. \$\endgroup\$
    – BESW
    Mar 13, 2014 at 21:09
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    \$\begingroup\$ Do not answer in comments. If you have a partial answer such that fulfils the game recommendation criteria, you are welcome to post it. \$\endgroup\$ Mar 16, 2014 at 6:36

2 Answers 2


Well, it depends what you want out of an actual game system that would make it "hard SF." Except for systems that have bunches of magic integral to them, I assume what you want is a "simulationist" system, one that behaves realistically, and has some explicit rules support for realistic near-future tech.

The most prominent fit for this is probably GURPS. GURPS is skill based, crunchy, and by default is quite realistic (add-ons for being more cinematic or even more realistic exist). There are sourcebooks for GURPS with additional support for near-future spacefaring - GURPS High-Tech, GURPS Ultra-Tech, GURPS Ultra-tech 2, GURPS Space, and the GURPS Transhuman Space line or the older GURPS Terradyne cover your desired hard-SF niche pretty strongly. (Not to mention many other variants, from Biotech to specific novel tie-ins like War Against the Cthorr and Uplift; if you're cribbing from an established author you have options).

GURPS is very crunchy and when handling tech doesn't go in for "it's a story element," they have a variety of specced-out options - in GURPS Space, for example, they offer options of chemical rockets, ion drives, fission, fusion, antimatter, Bussard ramjets, etc. with spaceship building options that are very detailed - each kind of drive has a thrust and a consumption (e.g. a TL9 optimized fusion drive has a thrust of .0013 tons per hour per unit of drive and a consumption of .000003 tons per hour of hydrogen). There's a sidebar on Hohmann transfer orbits. You want hard SF, the GURPSers deliver.

Wikipedia describes Terradyne thus:

GURPS Terradyne, a future history suitable for a hard science fiction campaign-in the tradition of stories by Robert A. Heinlein, Lester Del Rey and Ben Bova-in which technology has moved man out into space and Terradyne, a space-based corporate state, dominates but does not have exclusive control of space-based industries. It was superseded by the Transhuman Space series which covers the same niche.

Transhuman Space, however, goes more for the newer SF stuff which is more updated and '2010-correct' hard SF but if you're looking for a Rama feel you'd want something more dated. I own all these GURPS supplements I've mentioned so can go into more detail if you narrow down. It would really help if you mentioned representative authors and works that you consider hard SF such that there could be a closer match.

Pulling out Terradyne, it is about colonization of the solar system, with solar sails and ion drives being the limit of space travel. It is pretty heavily a setting book but it shows how you stitch together the various GURPS tech rulesets to support a setting.

Using "lighter" rulesets like Savage Worlds or FATE generally do not successfully give that hard sci-fi feel; they add a more cinematic flavor that tends strongly towards space opera. "Narratively" establishing hard SF would seem odd and tend to degenerate into technobabble quickly unless all the players are scientists themselves. Also, GURPS people tend to be science and tech wonks so the rulesets on these things are strongly reviewed by picky people.

Other respected harder SF games tend to be tied to a specific setting, like Blue Planet and Eclipse Phase. Traveller is very much not hard SF, though it was the gaming outlet for a lot of people with those inclinations over time.


This might be an oddball suggestion, but I would take a look at Shock: Human Contact, which is an in-depth varient of Shock: Social Science Fiction . It's an unusual game in its focus, style, and mechanics, but it allows focus and attention to the hard-SF element, in a way that's quite unique (and doesn't actually require any astrophysics calculations, unless you're absolutely slavering for 'em...).

It's an indie game, and while I won't explain the entire system, it's got two fundamental mechanics I think will interest you:

Shock Ownership: One central tenet of Shock is that the game is defined by a small number of, well, "Shocks," which is the game-term for major SF elements. So "FTL Space Travel" could be a shock, as could "Uploaded Consciousness" or a new alien race.

Here's the cool part: each Shock is "owned" by a particular player. That player is effectively the GM or the arbitrator for how that particular science, technology, or race works. So for every major trope you use, you've got somebody who's actually in charge of keeping consistency and rigor - which is exactly what you want! And then, yes, the game focuses on the particular Shocks you've chosen, and you can expect the game to explore those ideas and technologies.

Minutiæ Contribution: A common occurrence is for somebody to add "Minutiæ" about one of the Shocks - basically, to contribute a new wrinkle or detail about it. (I won't go into the mechanic of when precisely this happens.)

This doesn't force your science fiction to be hard ("My Minutiæ is that FTL travel is actually powered by burning unicorns for fuel!"). What it does do, though, is shine a spotlight on the details of your SF-nal tech and science. Instead of everything being hand-waving and SF-dressed magic, there's constant interest in the details, and I think this meshes very nicely with your desire for a hard SF feel to your game. A game that's interested in these details will, I think, feel tightly bound to small details, and how they can have big and unanticipated effects. That feels a lot like a hard-SF flavor to me.

Shock is an indie game; Shock: Social Science Fiction provides the basic framework and mechanics (which are extremely versatile), whereas Human Contact adds in a specific setting, a lot of specifics and Minutiæ, and a particular structure very appropriate to creating a campaign of linked Shock games. The theme of Human Contact is an exploring society making contact with far-flung colonies, which split off from Earth long ago.

You could certainly adapt your own setting to the Shock mechanics. Alternatively, if the other elements of Shock don't appeal to you, you might try to lift the "Shock Ownership" mechanic into some other system, where it might add great flavor.


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