Ten minutes of narrative stuffed into a ninety-minute vessel, the new documentary feature “Space Dogs” is an unfocused, half-baked stumble. It would be bad enough if the film were just short on things to say, lacking any cohesive structure, and uncomfortable to look at (all of which is also true), but it is also a dreadful slog lacking anything resembling momentum. Even the worst movies out there often give their audiences a glimpse at something interesting, or the fleeting promise of an idea worth pursuing, yet one can’t hold out hope for anything like that with “Space Dogs,” which seems to struggle to justify its own existence with each frame.