One of the few unexplored frontiers of legacy physics is momentum exchange. Conservation of momentum unlike conservation of energy, does not take many forms. At least not that we know of. It appears to be so simple a formula that no one has attempted to explore a theoretical approach to this physics. This situation is so dire, that conservation of momentum exchange is used as a necessary axiom or assumption in all physical theories.
Why do we need this physics? Because if we are to become an interstellar civilization, we need to once and for all prove or disprove that conservation of momentum is only a simple knocking heads (had another term but that did not sound right) formula. How could propellant-less interstellar propulsion, take us to the stars if momentum exchange cannot be bypassed?
Only the concept of the photon rocket may be seen as a true, propellantless propulsion system as it converts onboard electric power into directed radiation that in turn produces thrust.
Prof. Martin Tajmar's investigation into the EMDrive is an excellent example of experimental physics investigating the unknown or not fully understood, and possibly new physics. Ruling out thermal effects as a source for thrust while recognizing magnetic damping as a mechanism interfering with the experimental measurements. It is an example of the meticulousness required to eliminate experimental errors, and continue the dialog required between experimental and theoretical physics. For those of you interested in what it takes to do experimental physics - apparently boring until you get your hands dirty, and wow, the Universe changes in front of you - his paper is a must read.
Quoting the cautious Prof. Martin Tajmar,
The thrusts observed with the oil-damped torsion balance were close to the original prediction taking our small Q factor into account (around +/- 20 μN for 700 W of microwave power - still an order of magnitude more effective than pure radiation thrust). We also observed that the thrust appeared not to go down to zero immediately after power is switched-off but rather noted a gradual decrease as if the EMDrive was charged up and slowly reduced its thrust effect.
The nature of the thrusts observed is still unclear. Additional tests need to be carried out to study the magnetic interaction of the power feeding lines used for the liquid metal contacts. Our test campaign cannot confirm or refute the claims of the EMDrive but intends to independently assess possible side-effects in the measurements methods used so far.
Nevertheless, we do observe thrusts close to the magnitude of the actual predictions after eliminating many possible error sources that should warrant further investigation into the phenomena. Next steps include better magnetic shielding, further vacuum tests and improved EMDrive models with higher Q factors and electronics that allow tuning for optimal operation. As a worst case we may find how to effectively shield thrust balances from magnetic fields.
His paper suggests that Shawyer's EMDrive could have real experimental value for studying propellantless propulsion; but further experimental investigations are required to determine and eliminate experimental errors. Once this is completed we would have a substantially error proof experimental design that can be used to investigate the EMDrive thrust with confidence. That is the immediate goal.
To propel rockets using mass particles such as ions, atoms and molecules (aka fuel), momentum exchange is the basic concept behind thrust. So why do massless photons create thrust? Honestly, we don't know because we don't know how to falsify what we currently know. We have this empirical formula for photon momentum, p = h/λ where h is Planck's constant and λ is the photon's wavelength. And the group velocity that causes the EMDrive thrust, can be traced back to this empirical formula.
We cannot answer why a massless wave function has momentum, and therefore the need for a momentum exchange theory. Like energy, this empirical formula p = h/λ points to momentum having different forms. The two that we know of are, the mass based mv momentum, and the wave function h/λ momentum. This raises the question, are there other forms of momentum which we have not recognized for the lack of a theory? The dual momentum forms of mv and h/λ point to the possibility that momentum maybe an indirect property of mass-energy.
In An Introduction to Gravity Modification, I had proposed that in the absence of everything else, particles have a spherical shape that can be distorted. With linear velocity, the Lorentz-FitzGerald Transformation (LFT) distorts this shape in the direction of travel so that it is symmetrically flatter. In a gravitational field with acceleration, the Newtonian Gravitational Transformations (NGT) distort this shape asymmetrically, such that the near side (to the gravitational source) is flatter than the far side. This asymmetrical distortion led to the discovery of the massless gravitational acceleration formula g=τ.c^2, thereby confirming this shape hypothesis.
Therefore, momentum exchange is conserved and transmitted by this shape change. That is, we have a shape based foundational theory on momentum exchange that unifies motion (velocity, acceleration and momentum exchange) into a single phenomenon.
In Super Physics for Super Technologies, I had proposed that all particle properties can be constructed from 5 components or proto-fields, one of which is the sphere. Or, all particles have a spherical spacetime packet-like structure, whose size is related to the de Broglie wavelength. It is this spherical packet that conserves momentum. That is, we have deconstructed momentum exchange into its component parts. This introduces the possibility of replacing one of the components with a field that is equivalent to the wave function form. Sure much more research is required to tie up loose ends.
So where do we go from here? It's about inventing new types of engines. If we can apply an NGT-type transformation to a particle, a cluster, an object, or a spacecraft, we can cause motion in the direction per the NGT. How about that?
Our theoretical perspectives determine the questions we ask. Does this satisfy conservation of momentum? Does a particle accelerating in a gravitational field satisfy conservation of momentum? Is the momentum exchange question the right question to ask? Or should we be asking, which component of momentum exchange is in effect?
Therefore, since Shawyer stated that this thrust is greater than straight radiation pressure, is it possible that the EMDrive creates thrust by effecting an NGT-type spacetime transformation? By virtue of the EMDrive's asymmetrical design to create thrust, the greater the Q factor (reflections), greater the field strength of the NGT-type transformations, thus greater thrust?
That is the reason why we need to thoroughly investigate the EMDrive!