1 Directed Energy Interstellar Propulsion of WaferSats Travis Brashears (1) , Philip Lubin (1)) , Gary B. Hughes (2) , Kyle McDonough (1) , Sebastian Arias (1) , Alex Lang (1) , Caio Motta (1) , Peter Meinhold (1) , Payton Batliner (1) , Janelle Griswold (1) , Qicheng Zhang (1) , Yusuf Alnawakhtha (1) , Kenyon Prater (1) , Jonathan Madajian (1) , Olivia Sturman (1) , Jana Gergieva (1) , Aidan Gilkes (1) , Bret Silverstein (1) (1) Physics Department, University of Santa Barbara, CA 93106, trbrashears@gmail.com, +1-805- 893-8432 (2) Statistics Department, California Polytechnic State University, San Luis Obispo, CA 93407, gbhughes@calpoly.edu, +1-805-756-5648 Keywords: Interstellar Travel, Interstellar Exploration, Directed Energy, Laser Sail, WaferSats Abstract In the nearly 60 years of spaceflight we have accomplished wonderful feats of exploration and 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 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 (“wafer sats”) that reach more than ¼ c and reach the nearest star in 15 years to spacecraft with masses more than 10 5 kg (100 tons) that can reach speeds of near 1000 km/s such systems can be propelled to speeds currently unimaginable with our 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, optical systems and sensors combined with directed energy propulsion. Since “at home” the costs can be amortized over a very large number of missions. The human factor of exploring the nearest stars and exo-planets would be a profound voyage for humanity, one whose non-scientific implications would be enormous. It is time to begin this inevitable journey beyond our home. Introduction We propose a system that will allow us to take the step to interstellar exploration using directed energy propulsion combined with miniature probes including some where we would put an entire spacecraft on a wafer to achieve relativistic flight and allow us to reach nearby stars in a human lifetime. With recent work on wafer scale photonics and directed energy, we can now envision combining these technologies to allow for a realistic approach of sending probes far outside our solar system and to nearby stars. By leaving the main propulsion system back in Earth orbit (or nearby) and propelling wafer scale highly integrated spacecraft that include cameras, bi-directional optical communications, power and other sensors we can achieve gram scale systems coupled with small laser driven sails to