NASA knows a way to get humans to Mars in about a month, and to land unmanned probes in just three days.
In a NASA 360 video University of California Santa Barabara professor Philip Lubin describes the process of "photonic propulsion." It involves propelling objects with mass-free particles of light (photons). Basically, pushing spaceships with a great, big laser.
Lubin explains that the proposed system would require about the same amount of energy as the upcoming Space Launch System to get to "relativistic speeds." Which is to say speeds matching a significant percentage of the speed of light. In this case, 30 percent in about 10 minutes.
That speed is totally unheard of as far as human technology goes. And at a relatively reasonable energy cost, it sounds too good to be true. So what's the catch? According to Lubin there doesn't appear to be one. At least none that we couldn't overcome.
"There is no known reason why we could not do this," Lubin says in the video.
Lubin has a far more detailed roadmap on the subject, if you're interested in the specifics. Though the broad benefit is this: at that speed we could scout, and perhaps one day reach potentially habitable exoplanets light years away from Earth.