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Comment by hdivider | Hacker News Reader

Was it a fizzle? Didn't they get an "inconclusive" result, rather than a negative one?

(No criticism intended -- I really want to know.) :)

After further review I believe they found that for the EmDrive, the thrust was being generated by interaction of the electricity through the cables with Earth's magnetic field. Someone tested it by dampening the actual microwaves and still getting the same thrust result, which eliminates the microwave cavity as a source for the thrust. However the follow up test was with very low power, so they wanted to run it with magnetic shielding and higher power to fully rule it out.

"I believe they found that for the EmDrive, the thrust was being generated by interaction of the electricity through the cables with Earth's magnetic field." isnt that still thrust without and propellant or am I missing something?

I think what you’re missing is that the entire Earth is the reaction mass.

I’ve had a bit of fun doing the maths on space launch systems that function like this — if I remember right, you might even be able to do it… if you can make a monocrystalline superconductor, of whatever the best critical current density was about five years ago, about ten times the combined mass of your payload and cooling equipment.

Unfortunately there are limits on which direction this force can act in that make it even less useful than I’ve just made it seem.

You are correct in that this does not use propellant, however the Earth would need to be nearby for this to be viable for any sort of space travel. Perhaps maybe keeping a satellite in orbit or doing orbital maneuvers, but even then the amount of thrust is so small that it would likely not be usable. So unless the review team comes back and says they've eliminated magnetic interference then we're probably back to square one.

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