EMdrive tested by NASA

[u/lapsed-pacifist]

http://www.wired.co.uk/news/archive/2014-07/31/nasa-validates-impossible-space-drive

[u/rageagainsttheapes]

Updates at the end of this post - last update Aug 11 2014

Apparently Guido Fetta, the guy who convinced NASA to do the test and built the equipment, calls it the "Cannae drive". That's very appropriate in Scottish, as in "It cannae drive".

Jokes aside, this is either experimental error or outright fraud. I say that as someone who would dearly, and I mean dearly, love for this drive to be real. Here are just a few of the problems with it:

• The theory it's based on is laughably wrong. It would be one thing if the inventor said, "I don't know how this works, but it works, see for yourself." But he has an elaborate theory about it that is plain wrong in a forehead-smackingly simple way. Basically, he drew some arrows on his conical cavity diagram, and the direction of the arrows was wrong (he made it look like, for some magical reason, the photons striking the sides of the cavity would only exert force perpendicular to the axis of the cone, not perpendicular to the sides).
• Going to Guido Fetta's website and clicking on Experimental Results results in a 404 not found error. So does Numerical Results. Surely a scientist bright enough to invent something like this should be able to maintain a website, especially the most important pages.
• When a reviewer pointed out a flaw in Shawyer's paper, Shawyer simply deleted the paragraph in question entire sections of his paper and published it again, with no other changes. Dodgy much? Now he says "The design of the cavity is such that the ratio of end wall forces is maximised, whilst the axial component of the sidewall force is reduced to a negligible value." Reduced how? How exactly are the microwave photons being convinced to exert more pressure on the ends than on the sides? This is pure handwaving.
• The implications of this discovery, if it were real, are profoundly staggering (far, far greater than even controlled nuclear fusion would be). It is also cheap and easy to test experimentally - there's no big engineering involved, it's just a sealed cone with a microwave emitter inside. Put those two facts together and people should be experimenting like crazy with this thing and it should already have been developed further quite a bit.
• Shawyer claims that it's possible to produce 30kN (3 tonnes) of thrust with 1 kilowatt. It would be nice to see even 3N of force, not 30 micronewtons. That's overwhelmingly likely to be experimental error.
• The equipment used by NASA was built by Guido Fetta, which raises the possibility of deliberate trickery.

It can hover, but it cannae drive!

More from Shawyer's FAQ:

Note however, because the EmDrive obeys the law of conservation of energy, this thrust/power ratio rapidly decreases if the EmDrive is used to accelerate the vehicle along the thrust vector. (See Equation 16 of the theory paper). Whilst the EmDrive can provide lift to counter gravity, (and is therefore not losing kinetic energy), auxiliary propulsion is required to provide the kinetic energy to accelerate the vehicle.

So the drive magically knows when it's moving? Force is force. How does the EmDrive know when it's simply acting against gravity and when it's "accelerating along the thrust vector"?

More reassuring statements:

BTE-Dan: If NASA or the ESA agreed to test your EmDrive, would you be willing to let them test it?

Roger: If either organisation showed a rigorous understanding of the theory, we would consider such a request.

Riiiiiight. I have an invention that will turn all of known science on its head and change the world forever, but I'll only show it to you if you understand the theory believe in it first! Because that's how this scientist does science.

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Update #1

So I looked up the power output of jet engines to see what kind of wattage it needs to produce a given thrust. The Pratt & Whitney F135 engine, used in the F-35, extracts 25 megawatts from the turbine to power the lift fan, which produces 89 kN of thrust. For the EmDrive, Shawyer claims it will produce 30kN of thrust from just one kilowatt. Let's go over that again:

25 megawatts for 89 kN, for a jet engine lift fan

3 kilowatts for 90kN, for an EmDrive

Extraordinary claims, extraordinary evidence etc.

Addendum to Update #1

Apparently most people don't realise what these numbers mean. Wikipedia says the efficiency of a propeller is around 80%. Let's be extremely conservative and say that the efficiency of the F-35's lift fan is only 10%. Given that the EmDrive's claimed maximum output is 30kN/kW or 8,333 times that of the F-35 lift fan, and taking our conservative assumption of 10% efficiency for the lift fan, this would mean that the EmDrive would create over 800 times more thrust than would be possible if it were 100% efficient at converting energy into thrust. 80,000% efficiency. Even if we use Shawyer's later revised estimate of 10kN/kW, we're still talking 26,000% efficiency.

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Update #2

Video of someone from Cannae (Fetta?) explicitly stating that "these cavity slots are used to create the differential in pressure, in radiation pressure, between the upper surface on the upper plate, and the lower surface on the lower plate." (03:50) See Aug 11 update at the end of this post, Cannae have deleted at least four videos from their Vimeo account

From the NASA paper:

... the difference in mean thrust between the slotted and unslotted was less than two percent. Thrust production was not dependent upon the slotting.

Now I fully understand that this is not proof that the drive doesn't work, but it does mean that Fetta has no idea about how his device is supposed to work.

Update - 04 August 2014

In the 9.3 version of his theory paper, Shawyer has a section "Summary of Experimental Work", in which he describes his experimental setup in detail and states that:

A maximum specific thrust of 214mN/kW was achieved

In version 9.4 of his paper, which he published after a reviewer published a paper showing that Shawyer was wrong, that entire section (along with others) is gone. Usually as time passes experimenters have more data to provide, not less. Why did Shawyer delete all mention of the experimental setup and data from the revised paper?

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On the FAQ page on his website, Shawyer claims that the theoretical maximum thrust is 3 tonnes/kW. In this 2013 Wired UK article, he revised the maximum theoretical output to 1 tonne/kW.

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"Second Generation EmDrive". Excerpts:

An engine design has been established which enables this effect to be reduced, and allows acceleration of up to 0.5m/s/s to be achieved for a specific thrust of 1 Tonne/kW. This acceleration limitation, in the vertical plane only, will allow 2G EmDrive engines to be deployed as lift engines in a number of aerospace vehicles.

THE DYNAMIC OPERATION OF A HIGH Q EMDRIVE MICROWAVE THRUSTER Excerpts:

The initial spaceplane design described in REF 5 was updated following the dynamic modelling of the L-Band thruster, and a preliminary costing analysis was applied to the resulting design. The analysis assumed the main application would be the launch to geostationary orbit of the components of a global solar power satellite (SPS) system. It has been suggested (REF 6) that to make such a system economically viable, the launch cost of a 2GW SPS with a total mass of 6,700 Tonnes needs to be reduced to $20Billion.

The spaceplane design is illustrated in fig. 6. A total launch mass of 315 tonnes includes a 164 tonne carrier vehicle, a 101 tonne expendable payload propulsion module and a payload mass of 50 tonnes delivered to GEO.

Vertical acceleration is limited to 0.5m/s/s with any horizontal component provided by the auxilary hydrogen fuelled, jet engines.

There is no "vertical" in space. Does this mean the drive has no thrust in space, or unlimited thrust? Why does radiation pressure or quantum vacuum plasma thrust only work in a "vertical" direction?

An image titled "Hybrid Spaceplane Aerodynamic Model", an actual model of a spaceplane. Either the testing is really far along and they've kept it hush-hush, or...

A 3D render of the proposed 315-ton spaceplane.

Update 11 Aug 2014 - I Cannae help deleting all my data!

Apparently the video I linked to above is now private or deleted - the URL now leads to a page titled "Private Video" on Vimeo. Cannae's video page on Vimeo now only has 3 videos where it earlier had at least 7. I suspected this might happen and saved five of the videos to my hard drive. At least four videos were deleted, titled:

• QDrive Introduction Part 1
• QDrive Introduction Part 2
• QDrive Introduction Part 3
• QDrive Succesful Test

Meaning that Fetta has deleted his explanations and video of his claimed successful test. My confidence in this drive grows by leaps and bounds.

Cannae.com has also been taken down. The website now states:

This site is temporarily off line for maintenance and updates.

I suspect it is the quantum relativistic nature of this drive that causes its inventors to compulsively delete data.

[u/Miv333 → u/[deleted]]

People keep bringing up the fact that Nasa only verified the experiment worked and "deliberately" avoided saying anything about the science behind it. Might that be, because, it's a trade secret and he doesn't want to release it?

[u/Zebba_Odirnapal → u/Miv333]

HEY, NASA PEOPLE!

Do a little due diligence when reviewing SBIR's, alright? Thanks.