Of course, this question runs perilously close to this site's prohibition against discussing non-mainstream physics. However, the accepted answer in meta about what is acceptable and what is not acceptable regarding non-mainstream physics, says that it's okay to ask for an evaluation within mainstream physics of a new concept or paradigm. I believe my question falls under this heading. The new concept is that it might be possible (counter-intuitively) to accelerate a body in a vaccuum without a traditional propellant. My understanding from this article (paragraph starting "Dr. White proposed") is that the engineers at NASA have some kind of theory which is supposed to fit into mainstream physics about how this would work. But I'll understand if people vote to close.

The article I've linked to is not technical, and provides no technical references. My Google-fu has not managed to uncover a more technical description anywhere (I can't even find a homepage for the group doing this research). So

Question: What exactly is the theoretical mechanism that NASA (in particular, Sonny White, in particular, not Roger Shawyer) is proposing? And where can I read about it?

The proposal is apparently precise enough to build a computer simulation off of it (see near the end of the article, the section labeled "Progress Update"), so I'm assuming that it must be intelligible.

For example, here's something that might be the sort of thing they're talking about. Imagine that on your spacecraft you have a gamma-gamma collider (powered by a nuclear reactor or solar panels or whatever). When the photons collide, they create lots of high-energy electron-positron pairs spraying out in all directions. By clever design of the hull of your spacecraft, let's say that you preferentially readsorb electrons / positrons moving toward the bow of the ship (e.g. put a big lead block to the bow of the collider). Then you will generate momentum going forward. Your propellant particles have been bought from the vaccuum.

Now, the EM fields involved in the NASA setup are nowhere near this strong, so the mechanism can't be quite this. The article I linked to says something about virtual particle-antiparticle pairs, so maybe the proposal is that the "propellant" is made up of waves in the electron field which are not localized as particles?

EDIT Earlier questions have focused on whether the proposed effect would violate conservation of momentum. My assumption is that if we actually look at NASA's proposed mechanism, we will see that it's not violating conservation of momentum, just sending that momentum off into "new" particles, as in the example version I sketched. I'm really mostly interested in seeing the actual proposal, so maybe this question is best viewed as a reference request.

EDIT I'm disappointed to see this question marked as a duplicate. I'm asking for a specific link, and I haven't seen that link, nor have I seen a definitive claim that the link I'm looking for doesn't exist.

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    $\begingroup$ @KyleKanos Thanks, those are good links, since they're about the same project. But those questions were asking whether the experimentally observed effects were correctly interpreted as violating conservation of momentum. I'm asking what the proposed mechanism behind the effect is, which I think is a different question. $\endgroup$ – tcamps May 1 '15 at 17:22
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    $\begingroup$ Mach Effect Thruster, aka the Woodward effect. See en.wikipedia.org/wiki/Woodward_effect . I'm voting to close as off-topic. $\endgroup$ – David Hammen May 1 '15 at 17:37
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    $\begingroup$ From a quick look, I tentatively think this is on topic for the reasons outlined in previous comments. That being said, we do need to be careful in general about what EMdrive questions we allow, since the topic straddles the boundary of non-mainstream physics. $\endgroup$ – David Z May 1 '15 at 18:14
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    $\begingroup$ I can't see anything new here. The only recent development seems to be a NASA engineer reporting independent experiments at the NASASpaceflight forum (apparently, post 1632 here, which I don't find intelligible or novel). Note that NASASpaceflight is not officially related to NASA. IF NASA releases an official technical report on tests in vacuum, that's something we can talk about. As it is, the only thing to talk about so far is whether this can work, which has been well covered already. Voting to close as a duplicate. $\endgroup$ – Emilio Pisanty May 1 '15 at 18:55
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    $\begingroup$ If you are asking for a THEORETICAL explanation, then you are out of luck, because there is none. If you are asking for a HYPOTHETICAL one, then you can come up with as many as you like, since you are not constrained by standard physics any longer. The problem with hypothetical explanations is that you would have to re-check the entire knowledge of physics against their predictions and come up with consistency except for the emDrive. How likely is that? $\endgroup$ – CuriousOne May 1 '15 at 19:21