Since Dan’s interested in changing his Warhammer 40K setting using SavageWorlds over to Kapow! I need to get cracking on writing up a minimal set of the genre-specific rules for changing it from supers to space opera.
Broadly I think these are the areas that need tweaking:
Equipment
For superheroes, equipment other than vehicles is just an explanation of some heroes’ powers. For most SF settings, gear matters and players care about it (and upgrading it). Tentative rule: an item of gear is a power, with its own dice rating, but most gear requires that you have an appropriate Shtick to use it to full effectiveness; roll only 1 die if you don’t have a Shtick that covers it. E.g. a Blaster might be d8, d8 but you only roll d8 if you lack a Shtick like Soldier or Gunslinger to justify it. Some characters might still take a full-fledged Power where the explanation is gear, such as a cyborg with a built-in laser, bought with the usual power rules.
Vehicles
Vehicles will have their own Scope appropriate to the vehicle, so a groundcar would be Scope: Planetary Region, while a in-system shuttle might be Scope: Interplanetary, and a star-cruiser Scope: Interstellar. There will probably be more Scopes, so you can make distinctions between FTL where travel between nearby stars takes a couple weeks, a couple days, a couple hours, etc. Movement will be rated in terms of Scenes. One of the things I’ve noticed about travel in RPGS, and in SF RPGS in particular, is beyond a certain point unless travel is insanely dangerous (as in wandering monster rolls every 6 hours) players tend to stop caring about how long trips take; a journey of 10 days is not really any different from a journey of 100 days… both will be blipped over with the exact same hand-waving. Zap! will address this by requiring that you play out, or at least describe, a scene aboard the ship for each unit of distance traveled (size of unit determined by scope). Hopefully the scenes will be interesting, since the point isn’t to punish players for wanting to travel longer distances, but to give the act of travel texture so that the trips become more memorable and make longer trips seem longer because you can expect to have and later remember more incidents happening during them.
Maintenance
Similarly, and along the lines of my musings in Clarke’s Law and SF Roleplaying, to make tech seem a bit less magical, we’ll give equipment maintenance ratings (and maybe Advantages/Disadvantages like Low Maintenance/No Maintenance and High Maintenance/Constant Maintenance) that will also be expressed in terms of Scenes that need to be spent playing out or describing maintenance being done, or else it starts having chances of degrading or malfunctioning. Scenes will probably require that a character with an appropriate Shtick make a roll, with failure or mishap resulting in having to spend extra money or get replacement parts. I think this kind of thing is pretty important in SF…even in squeaky clean futures ships like the Enterprise require a ton of work to keep in repair, if the number of episodes where something goes wrong or needs replacement prompting them to make a landing and get in trouble is any indication. Again the idea is to make sure that there’s some “spotlight time” devoted to players, particularly those who’ve focussed on Shticks like Engineering, doing the things that define this as SF.
Aliens
We’ll just be using the Template rules from Argh! to handle alien races that have unusual abilities. We’ll probably also use the Argh! Templates for characters, but with new names if needed (e.g. Magician -> Technician).
Commerce
I’d like to come up with a simple way of handling commerce and trade, since that’s often important to star-faring SF. Again this is probably going to be expressed in terms of Scenes rather than tables of trade goods and prices, perhaps with some notion of trading off travel distances and risk vs. profit.
I think that’s the gist of it… but I’m open to suggestion on things I might have overlooked that would be important to an SF campaign that aren’t already covered.
Tales of the Rambling Bumblers 
Equipment: I would add the Disadvantage “Requires Training” to some equipment. While “point this end, pull this stick” works for a gun, is will not work with a hyperdrive or a specialized scanner.
Commerce: D20 Modern had an interesting way of handling commerce. You had a skill level in Income (or some such). If you want something and it’s price level is less than your Income, the cost is trivial and you can buy as much as you want. If it costs more, you have to roll. If you fail the roll, you can not find the item you want for a price that you can afford right now. You could also sacrifice levels of Income for high value items (I think it was 10 times the level sacrificed). Want to buy a house? That’s a target 60 item and your Income is 7, so you drop your Income to 6 and you now have a house. You are still getting the income, but you have less liquid income, because you have to keep up the house payments. Large windfalls work the same way. You save the King of Maldonia and he gives you 10 billion quadlocks? That is a scope 7 windfall, so your Income is increased. (either you put the money in the bank, or you pay off some debts.)
This could work with Income as a Power. It would nicely match the Scope of the Vehicles. It would get rid of keeping track of money, and make transactions either automatic, a roll, or a sacrifice.
As far as equipment, yes, there ought to be some equipment flagged as requiring expertise to work at all.
As far as Commerce, not actually tracking money is important, but I’m not sold on the d20 Modern approach, which is geared towards consumption rather than commerce. It works well enough for “What can my character afford to buy?” but it’s not a natural fit for “What can we pick up on this planet to sell elsewhere so we can meet the mortgage payment on the ship?” If you want to hand-wave away commerce entirely, as you probably would in a Star Trek or Starship Troopers style campaign, you don’t really need rules; if you want to worry about commerce as you might in a Firefly or Traveller type of campaign, then it would be nice to have rules that would help.
Ideally, I’d like to present commerce-oriented characters with interesting in-character decisions to make, without requiring the players to actually do a bunch of accounting or the GM to have to design and run an economy or turn every transaction into an adventure. Some transactions would be a springboard to an adventure, of course…but I’d like there to be a kind of background level of buying and selling and travelling that the PCs could do if they’re interested in that kind of campaign. That’s why I’m thinking of structuring things (again) in terms of scenes spent with that in the spotlight vs. resources gained/lost. Maybe special-purpose “XP” that can be spent on things like upgrading or repairing your ship or improving your merchant Shtick or wealth level…
I think the d20 Modern system could be used. if the ship has an Income power, then purchasing cargo lowers the Power and selling the cargo raises it. A table equating Scope to dollars (or credits or quadloos or whatever) makes translation easy.
Actually choosing what to buy should either be a character decision (with skill rolls to guide them perhaps) or fully abstracted. I don’t see any way around having some sort of economy though. Even if it is just a series of inputs and outputs (Planet Wibble imports nearly all food and luxury items and exports raw metals and machined parts). The players get to find special exports in game.
A character with business skills could modify the Scope of the planets imports and exports somewhat. (exactly how go do that, I don’t know.)
D20 Modern is entirely consumption-oriented, and it works because you can count on the players knowing what sorts of things are good for what…and being able to easily come up with things and their prices, because it’s just the modern world. If they decide they need a small portable generator for their jungle expedition they know such things exist and have some idea of how bulky it might be (not going to require a flatbed just to haul it, not going to fit in a pocket) and how expensive, what kinds of fuel it’s likely require, how easy it is to obtain, etc…. and they can Google it if they’re unsure.
In an SF game you can’t make any such assumptions. Is there a market for portable generators? How big are they, what do they run on, how expensive? You can probably cover a lot of the things that players might be interested in as consumers in advance, or on the fly as it crops up. But you can’t make what to buy and where to sell for a whole universe of commodities character decisions without inundating the players in tables and boring data. But if you fully abstract it, you turn it into “Roll to see whether you make money or lose it” People do enjoy craps, but that’s not what I want to turn commerce into for an SF RPG.
What I want to do is make commerce more like combat in Kapow! where players have narrative control to describe their wheeling and dealing in ways that seem plausible and are free to invent details on the fly, but have game-mechanical choices they can make that can help guide the outcome, such as using their Engineering Shtick to give themselves a boost on the value of their cargo by describing how they refurbish the engines that they bought before reselling them.
Based on our discussion a few weeks ago, here’s what I think might be a reasonable plan for equipment that can be used untrained, but should have an advantage for those who are trained: Equipment has one die , possibly with offset. If you have a shtick that indicates training with the equipment, you also roll your shtick dice and take the best. If you have a suitable power, you can Combine it with the equipment, and get a +1 to either the Power or the one die on the equipment, as you prefer. For some equipment, a low roll might indicate a malfunction or side effect, so having a shtick might make it significantly less likely to backfire.
Hm. Now I’m ambivalent about whether equipment is better represented as two dice, but one for untrained, or one die, but you get to roll your shtick as well.
Two dice lets you have more gradations (PL 6, 7, or 8 are all possible, not just 6 or 8), and rolling both dice is a more substantial advantage for a trained person if the equipment is powerful… being able to roll 2d4 in addition to a d12 is kind of meh. Unless the chance of malfunction is big, you’ll be relatively indifferent to having a trained or untrained person run the big gun.
On the other hand, rolling the Shtick and a single equipment die means the size of the Shtick matters, which is pretty important.