Contrary to what the science fiction TV series Babylon 5 portrays, I reluctantly have to predict that, given what human society is preoccupied with these days, we will probably have working, stable colonies of a few dozen people on the Moon and Mars only by then. Tourism into low Earth orbit for $50,000 a trip will be thriving, just as some tourists can now visit Antarctica. The commercialization of the space within lunar orbit will be well under way. Mars will still be very exotic, but mainly a destination for a few dozen scientists per year looking for fossils. I can imagine small spacecraft being sent into the Oort Cloud and perhaps beyond, but we are a long way from technology that lets us build machines capable of working for the hundreds of years needed to reach the nearby stars. I can imagine that the outer solar system will still be essentially unexplored by manned spacecraft because it is sooooo expensive. Plus, Europa aside, there is little need for humans to go out that far for adventure that can be supported by the rest of us through our taxes! I know this sounds pessimistic, but I think there will still be a lot of interesting things for us to do then. As for the actual technology, we will have fleets of single-stage-to-orbit space planes, solar sails and ion engines. All of these have been tested as prototypes by now. We just need to get ourselves motivated to be explorers and not worry about the costs and book keeping.
