Everyone knows that space is big. The thing about calling the Universe massive and what not is that no one can get a clear image of precisely what type of distances we're talking about. The closest star to our location would take the equivalent of 50 million Earth-Moon journeys to get too, or roughly 4.2 light-years. Other stars are thousands, millions, and billions of light-years away, so you do the math. For instance, Voyager 1, traveling at about 17 kilometers per second – the fastest speed of a human-built space probe, would take 74,000 years to get to Proxima Centauri, our closest stellar neighbor. So, how do we go about shortening these awfully-long times?
The common sense answer is fly faster, much faster. In fact, experts say, we should develop the technology to fly at close to the speed of light before we even think about leaving the solar system. According to our understanding of basic physics, nothing can travel faster than the speed of light, which is a constant. Other interpretation says otherwise but, for practical applications, this constant needs to be used. Proposals on how these massive speeds can be achieved include ships propelled by repeated hydrogen bomb explosions, or by vast, laser-powered reflective sails, or even by the annihilation of matter and antimatter. Naturally, we would have to develop an antimatter drive first.
Experts at the Kansas State University even proposed spacecrafts that would be powered by artificial black holes. Some say that warping time is the way to go, as in construct a ship that is able to create a bubble of sorts around it, in which time would pass slower than on the outside of the bubble. This would allow for massively-long trips to take only a few human years. But all these ideas are not what puzzle physicists. What's really disconcerting is the fact that there is absolutely nothing in our understanding of physics to prevent us from building such machines. In other words, they are not sci-fi, NewScientist
Some experts even propose a dark matter-fueled spaceship. The idea behind this proposal is based on solid astronomical knowledge. Dark matter makes up most of the contents of the Universe, and so the experts are proposing the construction of a vessel that would be able to collect dark matter as it moves, thus eliminating the need to carry the fuel it needs with it. The same type of design applies to a construct which plans to steal hydrogen from the interstellar medium, and force it into nuclear fusion aboard a spacecraft. The ship would then exhaust the by-products and obtain thrust. Sadly, in the matter of space exploration, only time will show which design works, and which is doomed to failure.