[aetherspawn]

It kind of protects against low budget sci-fi I guess, which could be a net good thing.

Under the rules you could attempt to shoot Resident Alien, but not Star Trek.

[irdc]

I'm thinking you could shoot an awesome sci-fi thriller under these rules. Even one that includes space travel. Just don't have any of the narrative take place in space: have only one character off-planet and have them communicate via radio.

[jmusall]

I've seen good, low-budget indie sci-fi short films that would presumably meet all of the Dogma 25 rules. So I think it doesn't protect against this category of films and neither would that be a good thing anyways. It just requires creative solutions if you want to e.g. portrait space travel.