But on the other hand, experience points for creatures defeated or aided makes sense. Of course, unlike the all-too-common interpretation of "defeating" a creature, you should really expand "defeat" in a mission-oriented game as any method of getting what you want out of the creature, from trickery through bribery to successfully negotiating an alliance. And, although I'm sure some GMs would throw fits at the idea, I think it's counterproductive to limit such experience to once per creature. In fact, allowing players to score lots of experience by defeating the same creature multiple times encourages non-violent solutions, because anything that kills an opponent ends the chance at future experience.
Earning experience for aiding someone is also a new twist on an old idea. It works the same way: 100 xp /HD, divided among the PCs and adjusted for PC level. Most of the citizens of interstellar civilization or a low-tech fantasy world will actually be 1 HD, which means that characters need to aid larger groups of people as they increase in level, particular since treasure no longer matters.
And in a space patrol campaign, you can save very large groups of people, perhaps entire cities or planets. This calls for a hack to avoid too much number-crunching. For aiding (or, for that matter, defeating) groups of 10 or more people/creatures:
- Make a rough guess as to population: one significant digit followed by a number of zeros.
- Divide the significant digit by the number of people who saved/defeated the group to get the party xp ratio; thus, five people saving a town of 5,000 are treated the same as one person saving 1,000.
- Count the digits, to get the number of hit dice; so, that town of 5,000 is equivalent to a 4 HD creature.
- Multiply HD x xp ratio x 100; that is the xp per character; ignore the level adjustment.
These xp awards should be adjusted by penalties if someone you promised or are obligated to help is injured or slain. Subtract the HD of innocent victims slain, or half the HD of those injured, from the creature or big mission HD before doing any xp calculation. So, if you save a deadly horta-like creature because it's the last of its kind, but it then kills 3 miners in the colony you were supposed to help, you subtract 3 HD from the HD of the horta, then multiply by 100, divide among the PCs, and adjust for level.