  In the nearly 60 years of spaceflight we have accomplished wonderful feats of
exploration that have shown the incredible spirit of the human drive to explore
and understand our universe. Yet in those 60 years we have barely left our
solar system with the Voyager 1 spacecraft launched in 1977 finally leaving the
solar system after 37 years of flight at a speed of 17 km/s or less than 0.006%
the speed of light. As remarkable as this is we will never reach even the
nearest stars with our current propulsion technology in even 10 millennium. We
have to radically rethink our strategy or give up our dreams of reaching the
stars, or wait for technology that does not currently exist. While we all dream
of human spaceflight to the stars in a way romanticized in books and movies, it
is not within our power to do so, nor it is clear that this is the path we
should choose. We posit a technological path forward, that while not simple, it
is within our technological reach. We propose a roadmap to a program that will
lead to sending relativistic probes to the nearest stars and will open up a
vast array of possibilities of flight both within our solar system and far
beyond. Spacecraft from gram level complete spacecraft on a wafer ("wafersats")
that reach more than $1/4c$ and reach the nearest star in 20 years to
spacecraft with masses more than $10^5$ kg (100 tons) that can reach speeds of
greater than 1000 km/s. These systems can be propelled to speeds currently
unimaginable with existing propulsion technologies. To do so requires a
fundamental change in our thinking of both propulsion and in many cases what a
spacecraft is. In addition to larger spacecraft, some capable of transporting
humans, we consider functional spacecraft on a wafer, including integrated
optical communications, imaging systems, photon thrusters, power and sensors
combined with directed energy propulsion.
