Re: Arindam Banerjee's peer-reviewed 2013 paper

Woof-woof, Arindam allowed me to post the background info. about rail
guns in his 2013 seminal paper on the rail gun.
Arindam Banerjee and Dr. P J Radcliffe
School of Electrical and Computer Engineering
Royal Melbourne Institute of Technology
Melbourne, Australia
Abstract—Recent experimental work on model rail guns shows very little
recoil upon the rails for the static case, where the armature or
projectile does not move. This appears to be a direct violation of
Newton’s Third Law of Motion, and has been mentioned as being such by
the experimenters. This paper proposes computer simulation exercises and
a new, simple, comprehensive and conclusive experiment to test the
nature of recoil for the dynamic case, where the armature does move in a
model rail gun.   The outcome of such experiments will either show a
definite, visible and repeatable violation of Newton’s Third Law of
Motion; or solidify the accepted physics theories and obtain new
insights into the nature of recoil from rail guns as a closed system
including the power source.
Index Terms—recoil, railgun, matter, energy, force, Newton, Maxwell,
Lorentz, Ampere, Coulomb
I. INTRODUCTION
Rail guns are an important technology for the future as they have many
operational advantages such as no bulky and dangerous explosives with
finite shelf life, very high bullet velocities, and can derive their
energy from standard energy systems often found on large equipment such
as ships and tanks.  Rail guns have been constructed that project 17Kg
masses exceeding Mach 7 as an exit velocity and higher speeds may be
possible [1]. By 2025 it is expected that the US navy will be equipped
with rail guns [2].  A range of potential commercial applications
(notably in space, mining and civil engineering) could take advantage of
new rail gun technology.
Essentially a rail gun is composed of two parallel conducting rails. A
large current is passed through them via a sliding short circuit
component which is the armature (the projectile or bullet) that
accelerates very fast in a  field whose magnitude is proportional to the
square of the current. (Figure 1)
There remains considerable controversy as regards the nature or reason
for recoil on the rail gun and this needs thorough investigation to
ensure the rail gun design including its mechanical mounting options is
optimized.  Work on static-armature model rail guns, where the armature
is held fixed appears to detect no recoil force on the breech or on the
rails; apparently contradicting fundamental physical laws.  There has
been no reported dynamic testing of rail guns to measure the recoil thus
leaving a considerable hole in the body of knowledge.
Following the thorough experimental work done by Schroder [3] which was
followed up by Putnam [4], there seems no reason to doubt that there is
only around 1% of the predicted mechanical reaction directed oppositely
to the action force on the static armature in the pendulum-suspended
model rail gun. However, it seems premature to claim that Newtonian laws
of motion have been violated in this instance. The static tests were
concerned simply with current in the rails and the armature; the
conducting leads that carry the same current as the rails, along with
the battery power source, that together with the rails and armature form
the total current loop, have not been included in the experiment to find
the location of the ultimate reaction.  The reaction from the force on
the armature could be present in the connection leads and the battery,
so from the overall system point of view the proposed invalidity of the
Newtonian laws of motion is debatable.
There is a clear need for dynamic testing of a model rail gun that
involves the entire current loop being investigated as a closed system. This could not only lead to the resolution of the above mentioned issue,
but also provide definite answers to old controversies regarding the
mechanical impact of electromagnetic fields upon current carrying
conductors [5]. In the past this sort of approach was considered
impractical [3],[6].
II. THE ELECTRODYNAMICS INVOLVED IN RAIL GUNS
The Newtonian thinking relating to every action having an equal and
opposite reaction is valid in electrostatics, and is the basis of
Coulomb’s law for the force of attraction and repulsion of static
charges. The basic equations below are discussed in text books [7],[8]. Graneau [5] deals in detail with the conflicting ideas in Newtonian and
the later Maxwellian electrodynamics.
F = q1q2r/(4πε0r2)…..       (1)
F is the vector force of attraction or repulsion between charges q1 and
q2 separated by distance r in a vacuum, and r is the unit distance
vector between the charges.
This thinking ultimately depends upon the action-at-a-distance
principle, which is also the prevalent basis of understanding
gravitational forces.  With moving charges in a conductor, that is to
say, with a current, the Oersted-Ampere’s force equation for parallel
conductors carrying currents being attracted or repelled became,
effectively, an extension of Coulomb’s law.  Thus, there was no
violation of Newtonian principles.  It was only when the Maxwellian
concept of the electromagnetic field behaving as the means of conduction
of energy from source to sink with the speed of light became prevalent,
that the notion of a force acting upon a charged body without any
reaction directly measurable, came to be seen as an apparent violation
of Newtonian principles.  Resulting from Maxwell’s work on the
electromagnetic field theory of energy propagation at the speed of
light, and elaborated upon by Grassman, Lorentz [9] and Einstein, is the
Lorentz equation for finding the force upon a charged mass in an
electromagnetic field, given by:
F = q(E + v× B) ……       (2)
Here, F is the Lorentz force on the conductor in newtons, q is the
coulomb charge in the conductor, E is the electric field as volts per
meter, and v x B is the vector cross product of the charged particles’
average velocity in meters per second in the conductor with the local
magnetic field expressed in teslas.  While there is a force on the
charged particle the equations do not predict any force on any other
object.  This would appear to violate the concept of an equal and
opposite reaction; Newton's third law.
The work of Graneau [5] clearly shows the heavy impact of Amperian
equal-and-opposite forces at the junction of the armature and the rail,
involving buckling of the rails with high currents.  On the other hand,
the work of Schroeder demonstrates very little mechanical reaction
against the electromagnetic force on the armature directed to the rails,
which suggests that the Newtonian concepts of equal and opposite
reaction are being violated and perhaps Lorentz forces are at work. Graneau [8] mentions that energy must be “flying out” of the battery or
electrical energy source, and that the mechanical reaction should
ultimately be found around the source and the leads.  He quotes Feynman:
“So our “crazy” theory says that the electrons are getting their energy
to generate heat because of the energy flowing into the wire from the
field outside” [10].
III.  RAILGUN RECOIL: SIMULATION APPROACHES
It should be possible with detailed finite element modeling to predict
the outcome of static and dynamic performance in terms of forces and
exit velocity taking into account the entire system along with its
geometry.  When matched with experimental results, they should go a long
way to reconcile these contradictory approaches in electrodynamics.  We
present below our approaches for such modeling and experimentation.
Earlier and more theoretical approaches to the issue have been made by
Hodge et al and Galanin et al [11],[12].  These studies are complex but
they have not lead to any experimental verification.  There is a clear
need for a straightforward theoretical approach, as clear and simple as
possible, that  will be tested by experiment.