Ultrafast-laser accelerated plasma propulsion system for space exploration

A near-term plasma propulsion system that could open up the solar system and beyond to human exploration is presented. It is based on some recent experimental research at the University of Michigan and several other laboratories throughout the world in which it was shown that ultrafast (with very short pulse length) lasers can accelerate charged particles to relativistic speeds. Those experiments have demonstrated dramatically the production of nearly collimated beams of protons at mean energies of several MeV when lasers with intensities of ≥ 10¹⁸ W/cm² were made to impinge on small focal spots in solid targets with a few microns thickness. When viewed from a propulsion standpoint these present- day systems can be considered as the precursors of devices that are capable of producing specific impulse of millions of second albeit at modest thrusts. If employed as propulsion systems, they can achieve interstellar fly-by missions in a scientist's lifetime but require significant enhancement in thrust to make then suitable for, say, manned mission in the solar system. In this paper we examine the underlying physics of the concept and indicate the steps required for its evolution into an effective near-term robust propulsion device.