The Fact and Fiction of the NASA EmDrive Paper Leak

James Woodward&#x27;s one of the old names in propellentless thrust --- he&#x27;s been working on Mach Effect based systems for a long time now. His approach is my favourite of all the anomolous science thruster systems, because (a) he actually has a testable theoretical model to back up his experiments, and (b) he doesn&#x27;t talk about it much; in the fairly rare interviews, he tends to be focused more on coming up with ways to <i>disprove</i> his experiments, rather than self-aggrandisement; which to my mind is the main mark of a serious scientist.<p>By which I mean to say, in the nicest possible way, that he&#x27;s not an impartial observer when talking about this thing, so it&#x27;s worth being careful about what he says.

As an electric propulsion engineer used to measure thrust in the uN range, what disturbs me much more than thrust levels close to the sensitivity threshold is the fact that thrust is only detected some 10-20s after the RF is turned on (figs 9,8,13). I am rather confident that there is no physical time scale in the RF generation process that would account for a 10-20s ramp, and this would contradict their own report of the fast RF power stabilization. It definitely looks like thermal drift; in fact, thermal drift is _always_ the first thing to suspect when you get strange measurements with a low thrust balance.<p>It appears as well that the authors have conveniently prepared an answer for this objection with fig.5 which attempts to mislead the reader by suggesting that the very slow evolution of the balance displacement is to be expected as an artifact of the combined effect of thermal drift and RF pulse onset. But conveniently, the time units are arbitrary so that hopefully nobody will notice that RF onset was assumed in that figure to have exactly the same characteristic time as the thermal drift... When all measurements actually show that RF power stabilizes much faster.

NASA seems to be minimally involved.<p>The group has been working five years in their own time in this small laboratory with shoestring budget. White has a day job in NASA and he and others are working with this project in their free time. To best of my knowledge - and correct me if I&#x27;m wrong - NASA only gave them $50,000 and a room in Johnson Space Center 2011. They don&#x27;t seem to be involved in any other way but &quot;NASA Eagleworks Laboratories&quot; makes it sound like official NASA organization.<p>Their results are consistently close to the detection threshold of their sensors. They are always flirting with the measurement error.

Actual paper from NASA recently on EmDrive (from Eagle Works) <a href="https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=12906254" rel="nofollow">https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=12906254</a><p>Actual paper: <a href="https:&#x2F;&#x2F;drive.google.com&#x2F;file&#x2F;d&#x2F;0B7kgKijo-p0ibm94VUY0TVktQlU&#x2F;view" rel="nofollow">https:&#x2F;&#x2F;drive.google.com&#x2F;file&#x2F;d&#x2F;0B7kgKijo-p0ibm94VUY0TVktQlU...</a>

So far I&#x27;ve failed to grok the many arguments for and against this drive&#x27;s &quot;impossibility&quot;. I&#x27;d love to find an ELI5 for it.<p>I think at this point, I&#x27;m resigned to waiting for an emdrive cubesat to just prove it once and for all: <a href="http:&#x2F;&#x2F;www.popularmechanics.com&#x2F;science&#x2F;energy&#x2F;a22678&#x2F;em-drive-cannae-cubesat-reactionless&#x2F;" rel="nofollow">http:&#x2F;&#x2F;www.popularmechanics.com&#x2F;science&#x2F;energy&#x2F;a22678&#x2F;em-dri...</a>

I know absolutely zero about rocket physics or quantum mechanics but isn&#x27;t this a fairly easy and &quot;cheap&quot; thruster to prototype and test <i>in actual space?</i><p>Nothing beats real world results, and this doesn&#x27;t seem that hard to test. It might even be faster and cheaper than what&#x27;s already been done, no?

There&#x27;s been breakthroughs in a fully quantified theory of how electromagnetics can be used to create propulsion reliably and at (still incredibly small but) orders of magnitude larger than prior designs provided by the aeronautics research team from the Northwestern Polytechnical University in Xi&#x27;an.<p>The research team published their breakthroughs in 2008, and excitingly, they&#x27;ve been highly reproducible.<p>Unfortunately, the paper appears to be behind a paywall: <a href="http:&#x2F;&#x2F;en.cnki.com.cn&#x2F;Article_en&#x2F;CJFDTOTAL-YHXB200805027.htm" rel="nofollow">http:&#x2F;&#x2F;en.cnki.com.cn&#x2F;Article_en&#x2F;CJFDTOTAL-YHXB200805027.htm</a><p>Does anyone on HN have the background necessary to explain the mechanics of EM propulsion to laymen?

If they feed electricity into the microwave horn, how strong is the induced magnetic field around the wires? Would that push against anything? How is that compensated for in measurements?

Sad to see this nonsense pseudoscience constantly making HN&#x27;s front page. Whenever it appears I debunk it using the same post[1] (in short, conservation of momentum cannot be violated) but it keeps coming back. Looks like even highly intelligent people like HNers are easily fooled by pseudoscience.<p>[1] <a href="http:&#x2F;&#x2F;www.preposterousuniverse.com&#x2F;blog&#x2F;2015&#x2F;05&#x2F;26&#x2F;warp-drives-and-scientific-reasoning&#x2F;" rel="nofollow">http:&#x2F;&#x2F;www.preposterousuniverse.com&#x2F;blog&#x2F;2015&#x2F;05&#x2F;26&#x2F;warp-dri...</a>