EM Drive

On this page we will discuss the "EmDrive" that offers to revolutionize space travel, by offering a peer review of NASA's 2014 paper on the topic. And we'll kick in a few other "alternative" sciences.

By the way, the way most people in videos are pronouncing the term as "em-drive".  If you are a microwave engineer, you are probably tempted to say "ee-em drive".  Maybe we should all practice saying "em-drive" so we can disassociate ourselves from it...

Nasa EmDrive

Photo of brassboard EmDrive from NASA's 2014 report

Engineers follow up on science experiments, to take advantage of the latest ideas and introduce the technology to the masses in saleable forms.  Science should not be accepted by engineering as a "belief system", you have to take new science with some skepticism.  Many of us simply believe the EmDrive can't work, thanks to the works of 17th century natural philosopher Isaac Newton.  If you know an engineer that predicts that EmDrive will change the future, up to and including tera-forming Mars and providing a path toward "warp drive", tell him/her to step back a bit and wait to see if the EM drive is really real or just another unclothed emperor.  Anyone that talks like they understand the EmDrive phenomenon should be suspected of being a phony intellect, until the theory is proven to actually work.

The first question you might ask about new science topic is, is there a reasonable and understandable explanation of how it violates existing canons such as Newton's Laws? We don't have an answer for that, and the theory, good or bad, is not really that important to engineers.   The second and third questions are far more important:  can you show me the data, and does it pass a full peer review?

Invented by Roger Shawyer in 1999-2001, below, he claims that EmDrive will provide free energy and flying cars.  Forget about free energy, two decades later, where are the flying cars? Your skepticism antennae should be twitching... Note that the original inventor was an engineer and not a scientist: the hay-days of experimentalists creating new forms of science were in the late 1800s. We all know how that ended: vacuum tubes! There is only a snowball's chance in hell that an engineer could have dreamed up how atomic energy and semiconductors work, but once the science is published, let the engineering begin...  Microwave engineers design excellent power amplifiers without a full understanding of semiconductor physics, let's have a look at this new widget and see what we can make of it.

Roger Shawyer discusses EmDrive

Not all science that turns out to be incorrect is secretly a fraud from the beginning, it may take some time before the history of EmDrive is complete. EmDrive was all over the news during the summer of 2014, as NASA claimed they were able to verify results initially discovered by researchers in China.  NASA would presumably not put their name on a paper if it was known internally to be bunk. Here is their publicly-available 2014 NASA report, paid for by U.S. taxpayers:

For sake of completeness in Microwaves101's unsolicited peer review, the full reference appears at the foot of this page.

The picture at the top of this web page is from NASA's report.  There is supposed to be something magical about one end of the EM garbage can being wider than the other, the fat end is supposed to provide thrust. 

The NASA experiment seem like a reasonable try at validating the EmDrive; it brings the science down to engineering level with an attempt to measure the actual thrust of a unit.  The DUT was mounted on an extremely sensitive torsion meter, inside a vacuum chamber (to simulate space), with liquid metal contacts providing DC power (supposed to remove the stress of DC cables). There are at least two major flaws in the paper: they don't provide a detailed mechanical schematic of what is isolated on the torsion setup, and they don't try to provide a list of all possible error terms, let alone  try to quantify them. But now that NASA put their name on EmDrive, you can't stop internet crank technologists are saying it is "proof" that the thing works.

One potential problem is that the test setup is not self-contained: The test set up includes SMA cables running out to a dual-directional power meter and VCO (or are they mounted on the torsion meter? Hard to tell). Some uncertainties added by cable connections could have been eliminated by using an on-board battery to power the system, and using BlueTooth to grab the data.  Does RF cable self-heating have an effect?

NASA's authors claim to have measured 116 micro-Newtons thrust when the RF power is switched on.  That is the equivalent of 12 milligrams force.    Note that cannabis gummies contain ~10mg of THC

The authors noted that different forces were recorded for different frequency resonances, buy they did not record DC power versus frequency, or thrust versus RF power.  As a control sample, the force generated by a 50 ohm load was used to calibrate the system, and was shown to be much less.  Maybe there is some type of magnetic interaction going on: are we just looking at a really crappy electromagnet? More on that later....

One positive outcome of the study is that we now have a publicly-available schematic that provides an example of what not to do, concerning ground loops.  You could not do worse than this, every power form is tied to chassis ground.  Read about why this is a bad idea, here.

Ground loops

Has there been any further work on EM drive by NASA?   Seems like they shut this idea down.  Maybe it is a conspiracy of the Deep State.  More likely, EmDrive is a load of BS.  Recent work in Germany may have figured out an actual reason that thrust could be measured on experimental hardware: The power cables may interact with the Earth's magnetic field, just like a compass. Here's a hint that the EM drive does not generate thrust: the German team measured the same thrust with just the DC power going through the cables and the RF switched off, and that when the turned the EM garbage can around they did not see the thrust reverse.  Ach du lieber!  It is hard to produce an explanation that supports EmDrive theory knowing these small facts. Notably, the ultimate answer to the question "does it work" will likely be a new benchmark in accurate experimentation and engineering peer review, and yet another low point in U.S. versus worldwide technology studies. Here are some links to the Dresden study.


In other news, Elizabeth Holmes pleaded guilty to fraud for her company's (Theranos) ability to evaluate blood samples:

Cold fusion

Cold fusion is the idea that you can get "free energy" from fusing hydrogen atoms in an intense magnetic field, yielding more energy that is required to sustain said magnetic field.  In 1989,  electro-chemistry seemed to provide the answer to free fusion energy, while skipping the detail that a crazy-intense magnetic field has been part of every credible fusion experiment.  Below, Bill Nye tells the story about how University of Utah researchers Martin Fleischmann and Stanley Pons fooled themselves and the world because they had placed the thermometer in the wrong place. Today, the very words "cold fusion" are used to indicate cooked data and disgrace.  

Bill Nye on Cold Fusion

 Brilliant Light Power

Yet another free-energy startup.  T=One accomplishment: hey trademarked the word "hydrino".


David A. Brady, Harold G. White, Paul March, James T. Lawrence, and Frank J. Davies, "Anomalous Thrust Production from an RF Test Device Measured on a Low-Thrust Torsion Pendulum", 50th AIAA/ASME/SAE/ASEE Joint Propulsion Conference; 28-30 Jul. 2014; Cleveland, OH; United States.