i think i already responded to this thread, i'm doing it again cause ppl often don't grasp this simple phenomena at first. so called reactionless or inertial propulsion comes down to a simple natural law which can be formulated as:
Unbalanced mass spinning 360° with varying speed or oscillating within 180° or less, accelerated and deccelerated at the axis, converts centrifugal force into linear acceleration.
in other words, any time you move an unbalanced mass, such as your arm, on an axis, you are breaking all the sacred "laws" of so called physics, namely,
law of action and reaction
law of conservation of angular momentum
and law of conservation of energy
or to put it more simply, you can literally swim in space
your mind will probably resist this, but how can it be, there must be a back reaction as you slow the mass down, but no, if mass if slowed down at the axis, inertia of the arm is converted into heat or magnetic breaking, no reaction.
consider also a fluid solution. imagine a circular pipe, bottom half 4 times the diameter of the upper, there is a pump inside the system,
in short, centrifugal force will be 4 x greater in upper part despite the fact that volume of water is 4 times less.
this is due to venturi effect (continuity principle), that water in narrower part speeds up proportionally to how much narrower pipe is (
https://youtu.be/UJ3-Zm1wbIQ?t=97 ) and a fact that centrifugal force is proportional to velocity squared.
here calculate for yourself
http://www.calctool.org/CALC/phys/newtonian/centrifugalof course increase of velocity means more friction and very low friction tube must be used, like electropolished stainless steel
of course, such design is not the best cause volume of water in bottom part is too big, this can be avoided using 45 degree knee due to a bernouli's principle, that is, that water loses pressure as it enters narrower part. as it exits into the wider part inertia is converted into static pressure (acting on all sides of the pipe) and there is no backward reaction.
picture below how it could be made
there are also other approaches to water inertial drives, like this
https://www.youtube.com/watch?v=cIri1tTuaqU