The electromagnetic stress-tensor as a possible space drive propulsion concept

The Heaviside force, by virtue of its nonzero value in vacuum, would appear to offer the germ of a real spacedrive. Classical electrodynamic interactions may be viewed as transmitted continuously through deformations in the state of the electromagnetic field, which acts like a stressed elastic medium. Maxwell stresses not only provide a controllable net momentum flow, but also a physical mechanism acting on the fabric of space-time. In response to this unbalanced force it has been asserted that a spacecraft will move off with equal and opposite momentum. The electromagnetic interaction mechanism under consideration suggests the basis for a novel development in electrical machine technology and a possible space-drive for space transportation. The physical basis of this concept is examined in this paper, and experimental investigations are described. Supporting analyses and historical background are included. INTRODUCTION Perhaps the most intriguing challenge facing twentyfirst century space-flight is the novel concept of a "Space-Drive". John W. Campbell and Sir Arthur C. Clarke are usually credited with conceiving this visionary hypothesis. Without proposing any physical mechanism (for which one might cultivate some emerging technology to exploit) they articulated what such an astonishing apparatus will do: a space-drive is a propulsion mechanism that acts directly upon the fabric of free-space. (Actually, the notion of a space-drive was discussed in the engineering literature almost a dozen years earlier by Joseph Slepian. See below.) Remarkably, spacecraft employing such space-drive devices would not have to convey any reaction mass to eject as propellant. The grand challenge is, how might such a striking proposition be supported within the framework of conventional physics? And, even more thoughtprovoking, how might such a concept be realized in actual engineering hardware? There exist several enchanting candidates for making progress along these lines. We will address only one such concept, Copyright © 2001 by the Institute for Software Research, Inc. Published by the American Institute of Aeronautics and Astronautics, Inc. with permission. and let us confess from the offset that we have no startling breakthrough to disclose. However, we do want to report on a phenomenological approach to the problem, which, to us, would seem both to encompass the concept of a space-drive, and also to hold out the promise of achievability with technology that is within reach. ELECTROMAGNETIC FOUNDATION In Maxwell's field theory electrodynamic interactions are transmitted continuously through deformations in the state of electromagnetic fields, which act like elastic stresses. (Note that Maxwell's equations were already relativistically covariant when he wrote them down in 1864, so what we are exploring has little, if any, relation to the old "luminiferous aether" theories.) Recall that in General Relativity (also a field theory) the interactions are transmitted as deformations in the underlying metrical structure of space-time. Ultimately, any true space drive mechanism must be expressible within such a framework. The original force-field derivation, actually constructed by Maxwell (and extended to vector differential form by Heaviside)' provides the archetypical classical space-drive: an electromagnetic force acting directly upon the electrical fabric of space-time itself. The classical derivation of the Maxwell stress tensor is 1 American Institute of Aeronautics and Astronautics c)2001 American Institute of Aeronautics & Astronautics or Published with Permission of Author(s) and/or Author(s)' Sponsoring Organization. presented in many places and we have discussed it in several previous publications.' The most direct approach for developing the stress tensor is to start with the traditional coordinate independent Gibbsian, vector differential form of Maxwell's four celebrated equations in practical engineering (MKSA) units: + H ,W) (8)