Wind-Pellet Shear Sailing

Author: Jeffrey Greason, B.S., Chairman, Tau Zero Foundation

Background: Gaining the kinetic energy required for interstellar flight affordably is difficult and tapping existing natural sources of energy such as the solar wind is attractive for reducing costs.  However, a gap exists in the published concepts, in that solar wind speeds are limited to ~700 km/s, while even with concepts such as the wind-powered reaction drive (‘q’-drive), speeds of ~5% of c must be reached before they can take over.  A cost effective way to fill that gap has been lacking. Objective – Demonstrate a method by which inert pellets, accelerated by the solar wind, can be used to accelerate a spacecraft from solar wind speeds up to ~5% of c.

Methods: Classical physics computations to support the basic physics and feasibility of the approach.

Results: When two matter streams are in proximity but with different velocities, or when they move through the same space but with different velocities and distinguishable properties, the difference in velocities, or velocity shear, can be used to gain propulsive energy.   A stream of pellets moving through the interstellar medium is an example of such a case.   Propulsion by pellets is an idea explored in the prior art that requires high speed pellets; the extraction of useful work from the difference in speed between the pellets and the interstellar medium allows a ship running over the pellets and also drawing energy from the passage through the interstellar medium to gain propulsive energy even when faster than the pellets and even when the pellets are composed of inert reaction mass.  We will discuss the basic physics of this and the performance equations and discuss this in the context of using relatively slow pellets (accelerated by solar wind), to send a spacecraft to a substantial multiple over the solar wind velocity.   Another case where small macroparticles and a plasma wind are at different speeds is the inner solar system in the plane of the ecliptic, where the solar wind and zodiacal dust have different velocity distributions; this may offer further applications of the same principle.