Cyclers
There aren't any thrusters on that shot because I didn't make the film.
A "cycler" makes a lot of sense as long as the travel times remain large. I don't know enough about orbital mechanics to know how practical the idea is, but accelerating a small manned vehicle a (relatively) short distance to reach a space station makes more sense than having to accelerate the big vehicles over and over again to go all the way to Mars.
Hopefully, propulsion technologies will be developed to shorten travel times to the point where people aren't going to have to spend months in space either on cyclers or other vehicles.