A pretty interesting read that addresses these questions is Deep Space Propulsion: A Roadmap to Interstellar Flight http://www.amazon.com/Deep-Space-Propulsio

A pretty interesting read that addresses these questions is Deep Space Propulsion: A Roadmap to Interstellar Flight http://www.amazon.com/Deep-Space-Propulsion-Interstellar-Astronomers/dp/1461406064 http://www.amazon.com/Deep-Space-Propulsion-Interstellar-Ast...