John, though I'm no means an expert in physics, but I could write a paper to answer your question, so I'll give you a list of Wikipedia articles and give a basic rundown of what I mean by using the quantum realm as an energy source.
Virtual Particles
Vacuum Energy
Zero-point energy
Casimir effect
Alcubierre warp drive
wormholes
Due to the uncertainty principle, all space is filled with the energy of virtual particles popping into existence and immediately annihilating each other in which very small regions of space have varying energy densities which, at macroscopic scales, averages out. Placing two uncharged plates nanometers apart causes the energy density in the space between the plates to be less than the rest of space. Since this density is less than the average, the energy is said to be negative and exerts a negative pressure on the plates, drawing them together. Thus quantum forces are producing mechanical motion which could one day be used to power a nanotech machine. Both the hypothetical Alcubierre warp drive and wormholes require negative mass/energy to either create the spacetime warp, or hold the wormhole throat open. Since large spacecraft will need larger bubbles or wormholes, and hence enormous energy to power them, it seems logical to me that an advanced nanotech craft could possibly take advantage of the Casimir effect for all it negative energy needs for the creation of microscopic bubbles. I'm on the fence on whether or not warp drives or wormholes will ever be found to be producible or usable at any scale. The realists in me says "No", however we have yet to discover everything and maybe a quantum theory of gravity will yield solutions or confirm such drives are impossible.
Nathan, my remark is less about ingenuity, innovation, and the advancement of sciences and knowledge, but about the practical matter of cost. In all the science fiction I have read, including hard, economic realities are almost always ignored; cultures are building grand space stations, spacecraft and fleets, hollowing out asteroids, and many more engineering feats with a seemingly infinite supply of value and labor. We can send people to Mars now with today's technology but the craft would be massive and the entire program and mission would cost the GNP of small countries. Probes are obviously cheaper, and less riskier.
From an article in the Aviation Week and Space Technology (June 23, 2014):
The space station is the engineering marvel of our age—a spaceship the length of a football field where six people conduct cutting-edge scientific research while refining our collective skill at operating above the atmosphere. But the space agencies of the world do not agree on where we should go next with that hard-won expertise. There are not that many choices, and the few that there are will not be easy. Mars, it seems, is as far as humankind can practicably expect to go, for now.
“Based on limitations to human physiology, based on reasonable technical limitations to the ability to shield humans during long voyages in interplanetary space, the horizon goal for human space exploration is Mars,” says Jonathan Lunine, a top planetary scientist at Cornell University, who co-chaired the recent U.S. National Research Council (NRC) human-spaceflight study. “Now, horizon in this case essentially means the farthest goal. It is not the only goal.”
Nor will it be cheap. Ultimately, the NRC panel found, the human exploration of Mars will take “decades” of work, and cost “hundreds of billions” of dollars. No one has that kind of money—not the U.S., not China and not, in the foreseeable future, all of the spacefaring nations and wannabees put together.
“I would not want to indulge in specious precision to say whether it was $300 billion or $500 billion, but it is a lot of money,” says John C. Sommerer, a retired Applied Physics Laboratory engineer who headed the subcommittee that drafted the technical portion of the NRC report. “Given that we currently spend on the order of $8 billion [annually in the U.S.] on human spaceflight, you immediately understand why it is a long-term program.”
Although humans are getting a robot’s-eye view of the Martian surface every day, courtesy of the Curiosity rover (see page 40), no one even pretends there will be a human landing there until the 2030s at the earliest. Most of the world’s space agencies include Mars in their exploration plans, but only NASA treats it as a viable goal toward which work is ongoing now that is designed to make it happen.
Even with expected advancements in technology, human exploration of space is costly. The privatization of space will bring the price down some. The ticket for a Virgin Galactic SpaceShipTwo is $250,000. I'll never be able to afford that. If I had that kind of money, I'd put it to better use. The private citizens that will be touring space will be wealthy enough to blow a quarter of a million dollars on a short spaceflight that doesn't really go anywhere except straight up and back down.
If John's target dates are correct, we will have the Singularity and SICs well before the industrial nations and wealthy citizens and corporation of the world could bankroll the colonization of the solar system, let alone finance an interstellar voyage. Now, is there any reason to doubt that neurological science and technology will not advance to the stage that the mind can be recorded and uploaded into computer system or robotic probe, or that the reverse could happen, that a robotic probe's experiences could be downloaded into a person's mind so that they can experience space exploration from wherever they are? Wouldn't it be great to plop down on the couch, log onto a probe feed on the internet, and explore Titan? That will be the most affordable method. Humans will go to Mars, but I think it more likely that intelligent machines will colonize the solar system, and some of those machines would have been born human.