[Cog]

Well you aren't getting a perpetual motion machine, even if this thing works. You still have to provide energy to the EM drive to get a very small thrust vector. I mean real small. My small finger could provide more thrust. But my small finger requires fuel to work and if you don't have to carry rocket fuel to create thrust, you have accomplished a great deal.

[KaiserJeep]

Depends upon the meaning of "fuel" I suppose. Electricity is not technically a fuel, but you can heat your house with it and use it to power a car. Photovoltaic power in space is pretty much unlimited, once you have boosted the panels into orbit.

[Subjectivist]

Most people are using the term fuel when what they actually mean isreaction mass. It is kind of irritating to be honest, after all a solar sail does not use "fuel" but it does use photons and solar wind particles as reaction mass reflecting off or sticking too the sail. An ion drive engine ejects a very small stream of very fast moving plasma via electic field effects on th plasma. The plasma is not fuel, it is just reaction mass accellerated electrically. A NERVA nuclear reaction engine uses heat to raise the pressure of a gas, often Hydrogen, and then eject it as reaction mass. The fuel is nuclear heat, but the fuel stays in the engine from start to finish of the service life of the engine.

An old fashioned chemical rocket mixed a fuel and oxidizer, allows them to react and the hot exhaust products become the reaction mass expelled from the rocket. Some rockets like the Space Shuttle Main Engine even add extra hydrogen to the reaction chamber that absorb part of the heat from the O2/H2 reaction to boost the amount of fast moving reaction mass to eke out a more efficient use of the heat generated. There was even a proposal and series of tests done to inject H2 into the top of the Solid Rocket Boosters to increase their reaction mass to heat capacity ratio and make them more efficient.

What makes this drive unique is not the "fuel" but the lack of visible reaction mass. If it is reacting with quantum fiam we just can't see then there is reaction mass, we just don't currently know how to detect it.

[evilgenius]

Instead of saying reaction mass you could just say propellant. I was reading the comments to a story about the Em Drive somewhere and a person made good use of that word. Propellant, being propelled, sort of invites the idea of direction in a way that fuel doesn't. We very easily conflate fuel with the idea of energy. Energy can be about direction, because of performing work, but not necessarily.

[vox_mundi]

NASA’s EM-Drive is a Magnetic WTF-Thruster

$this->bbcode_second_pass_quote('', '[')b]Test reveals that the magic space unicorns pushing the EM-drive are magnetic fields.

[KaiserJeep]

I always figured the EM space drive was another myth, like the 500mpg carburetor, the magic pill that turns water into ICE fuel, or the surplus WW2 Jeeps that are disassembled in crates and cost $50.

[Outcast_Searcher]

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[evilgenius]

The other day I read someone's very dismissive report on the EM Drive. They cataloged the details of how some experimenters built their own device. I suppose they built it according to the same specs as others have. Theirs could have been different, though, as the author didn't provide those specifics. They didn't detail the similarities or differences of construction. Whether they did or not is important. They came to the conclusion that having the wires run along the thrust detector made for a magnetic interaction. They speculated that interaction also involved the earth's magnetic field. Of course, that makes me think about what Kaiser Jeep said about how important this tech could be for low earth orbit satellite correction. Even if it does work because it interacts with the earth's magnetic field it would still be very useful. The tears come, really, over the disappointment about interstellar travel. But they might have experienced something which was only relevant to their device. For example, a year or so ago I watched someone's home video demonstrating their device, and they used a separated scale. I don't know if that person's device would have tested positive in the null mode. It might have. At any rate, I'm not ready to cry, yet.

https://arstechnica.com/science/2018/05/nasas-em-drive-is-a-magnetic-wtf-thruster/