The Journal of Space Exploration has just accepted my latest paper in which I focus far more on applying quantised inertia to propulsion, and which also shows an even simpler way to derive and understand QI, just from the uncertainty principle and relativity. This is a path I've been tending towards for a long time (see references). Werner Heisenberg showed, for a quantum object, the uncertainty in its momentum (dp) times the uncertainty in its position (dx) always has to be larger then Planck's constant divided by two Pi (hbar), over two (aka hbar/2). So: dpdx > hbar/2.

The assumption of quantised inertia is that you can apply quantum mechanics on the macroscale, if you take account of relativistic horizons. So, imagine we have a highly-accelerated system that excites the quantum vacuum (another way to say that is to say it sees Unruh radiation). For example, this might be a cavity with microwaves or a discharge spark inside. Imagine we now increase 'hbar' to represent the energy in this macroscopic system - bringing quantum mechanics to the macroscale. Now make the cavity asymmetrical so that the Unruh waves on the left side are blocked by a shield but those on the right side are not. Since you are blocking information from the left from getting to the system you are decreasing dx on the left side (the uncertainty in position in space is decreased because so far as the system knows there is no space beyond your shield), and so dp must increase to the left. This means that the normal quantum jitter (dp) usually very weak, is now magnified by the large accelerations (Unruh radiation) and also must be larger towards the left hand side. The system on a statistical average will move towards the left. As I show in the new paper, this predicts, to the right order of magnitude, the thrusts seen in the emdrive, the Woodward drive and also some intriguing results from asymmetrical capacitors.

The thrust of the argument :) is that quantum mechanics may not just apply to the small, and relativity to the fast: quantised inertia implies that at very high accelerations they join up to produce observable, and very useful, behaviour. Thrust without propellant means much lighter (cheaper) launch systems, and the possibility of interstellar travel in a human lifetime.

**References**

McCulloch, M.E., 2013. Gravity from the uncertainty principle. Astrophy & Space Science, 349, 957-959 Preprint

McCulloch, M.E., 2016. Quantised inertia from relativity and the uncertainty principle. EPL, 115, 69001 Preprint

McCulloch, M.E., 2018. Propellant-less propulsion from quantised inertia. J. of Space Exploration (in press). Preprint