DARPA has announced a contest where they will offer half a million in seed money to a private company that can come up with a blueprint to travel to another star in the next hundred years.
This is a huge undertaking, and I don't see how it can be done in only one hundred years. I do realize one hundred years is a long time for scientific progress. A hundred years ago Godard was just starting to experiment with rockets and IBM was selling the first of the Tabulating Machines. Now private companies are going into space and computers are everywhere. However traveling to the nearest stars seems like too big of a leap.
Our current space ships only have the power to break Earth's orbit. There are designs for Magnetic Field Oscillating Amplified Thrusters, using fluctuating magnetic fields to induce density waves in electric conductive media, that could allow a spaceship to reach speeds of 260 Kilometers per second or nearly 1/1,000th of the speed of light. These ships that are more advanced than anything we can build right now would take 4,000 years to reach the nearest star. Knowing my luck there would be an annoying kid kicking the back of my seat for the whole 4,000 year trip.
These ships would open up the inner solar system but would still leave the outer solar system where all the good stuff is isolated.
I've talked before about a giant space based solar power plant in Mercury's orbit to create antimatter to power ships at speeds of up to 6% of the speed of light. But even with real research and development budgets (3 to 5% of Earth's GDP) I really don't see that happening in the next hundred years.
A faster way to get something up to the speeds necessary to cross Interstellar space, at least 1/10 the speed of light so the nearest stars are only 40 years away, is with lasers and mirrors.
You could launch a lot of small craft, if you consider the largest spacecraft we've ever launched small, that are just solar power platforms with huge lasers into low orbits around the Sun. You could then have a ship that had a huge mirror on its back and the lasers around the Sun could aim at it speeding it up to the necessary speeds. This could get a ship to the nearest stars by 2100, however I've got no idea how you would stop the ship once it got there. This would work great for sending a probe to the nearest stars, as it would spend a good 5 hours in the inner solar system of that star, but it's not such a great idea for humans.
It would be possible to send a lot of small probes, weighing couple of pounds each, with a mirror made of buckypaper a mile wide so it could use it as a solar brake as it got near the star. This would work best with Alpha Centuri as you could use it's three stars to slow down. Then use the huge mirrors to concentrate the star's light to a solar panel to power a laser to slow the probes coming from Earth until you had enough lasers around Alpha Centuri to slow down a spaceship carrying humans. But getting all that in place in the next 60 years in order to hit the DARPA deadline of one hundred years, taking into account the 40 year voyage, seems a little far fetched.
The final option for reaching the nearest stars within a hundred years is something that is at the same stage as computers or controlled fusion were a hundred years ago. It might work or be a pipe dream. The Neutrino Drive. The idea is if you could find a way to store Neutrinos you could use them to power a space ship. Neutrinos have no mass or charge, so your fuel would weigh nothing. You could take as much fuel as you needed and you wouldn't have to use fuel to accelerate it. A ship with Neutrino drive could get near the speed of light and still be able to slow down. The question is can a method of storing Neutrinos ever work.
If it can it will lead to a fantastic future within the next hundred years.
By Darrell B. Nelson author of I KILLED THE MAN THAT WASN'T THERE