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NASA: EM Drive really does work

sciencealert.com

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Re: NASA: EM Drive really does work

#11

Post by thearn4 »

I'm a researcher working in propulsion technologies at NASA. For what it's worth, the "Eagleworks" guys at JSC are basically doing their own thing that, as far as I can tell, is outside of any peer review process. For the life of me I can't imagine a team at one of the research centers (GRC, LaRC, ARC, GSFC, JPL) getting away with that.

I'm guessing that they're running off of resources from center-level micro seedling funding.

On one hand, the effort is probably costing next to nothing in terms of FTE and procurement. On the other hand, they're giving the public warp-drive level expectations, when the agency can barely afford to keep the lights on for a manned spaceflight program.

Re: NASA: EM Drive really does work

#12

Post by lucozade »

leephillips wrote: post #9
lucozade wrote: post #4

Earlier quoted context omitted.

As far as i understand it, there no free energy being claimed i.e. they still need to power the drive. What's being claimed is a drive that creates thrust without a reaction (in the Newtonian sense). If true, from a physics point of view, this is huge. Less clear about its immediate practical implications other than it may make a useful thruster for spacecraft. To put it in its historical context, its hardly unpreced…

Energy-momentum conservation is more fundamental than Newtonian physics. It's part of the structure of spacetime. http://arstechnica.com/science/2015/05/the-female-mathematic...

There's possibly another, more subtle, interpretation.

It may be that the structure of spacetime does not necessarily exhibit this conservation. However, all scientifically observable phenomenon must, by definition, exhibit space, time and rotational invariants. Otherwise they can't be scientifically observable i.e. by repeatable experiments.

From Noether's theorem, this means that the scientifically observable phenomena must exhibit at least energy, momentum and angular momentum conservation. Either in the laws that govern the phenomena or the consequences of a, potentially violating, law that do conserve.

It's an interesting take on the duality, at least it is to me.

Re: NASA: EM Drive really does work

#14

Post by todd8 »

A few years ago, before this news of the EM Drive started to appear, I was contacted by a friend who wanted to introduce me to an "inventor".

This young inventor that had not taken any courses in physics, but believed that he had invented a mechanical inertial drive mechanism that worked with rotating wheels and moving rods and weights. He was looking for investors to fund the construction of the mechanism. I tried to explain that conservation of momentum meant that his "drive" could not generate any net motion, but he never accepted my assessment; he kept asking me to explain in detail why this or that force combined with a rotating pair or arms wouldn't propel a vehicle forward. I told him that the laws of Newtonian physics would have to be tossed out if his invention indeed worked; he responded by saying that this is how scientific revolutions happened.

It was all quite frustrating for both of us and reminded me of seeing a report on a national news program (NBC) perhaps twenty years ago of a farmer in the US that had inventing a perpetual motion machine. They showed the complex machine turning a wheel in the farmer's barn. The reporter was quite excited by the possibility that this would be the answer to unlimited energy. Seriously!

Now there is this EM Drive, of which I am naturally skeptical, and no one seems to be able to explain the experimental results. It's ironic.

Re: NASA: EM Drive really does work

#15

Post by leephillips »

lucozade wrote: post #12
leephillips wrote: post #9

Earlier quoted context omitted.

Energy-momentum conservation is more fundamental than Newtonian physics. It's part of the structure of spacetime. http://arstechnica.com/science/2015/05/the-female-mathematic...

There's possibly another, more subtle, interpretation. It may be that the structure of spacetime does not necessarily exhibit this conservation. However, all scientifically observable phenomenon must, by definition, exhibit space, time and rotational invariants. Otherwise they can't be scientifically observable i.e. by repeatable experiments. From Noether's theorem, this means that the scientifically observable pheno…

I think there are some interesting ideas here, thanks.

Re: NASA: EM Drive really does work

#16

Post by sjburt »

cloudsloth wrote: post #13

Forgive me if I'm being obtuse, but can't someone just put am EM drive in space and see if it goes?

There is a venture, Cannae, that is attempting to launch a Cubesat with an incarnation of this device.

I'm not sure if they're funded, but the cost for a mission of this type can be only a few hundred thousand US$, so it's not an unreachable quantity by any means.

http://cannae.com/the-technology/

Re: NASA: EM Drive really does work

#17

Post by andygates »

cloudsloth wrote: post #13

Forgive me if I'm being obtuse, but can't someone just put am EM drive in space and see if it goes?

Lightsail (which uses regular physics) is doing that, launching a breadbox sail and a second proximity measuring cubesat along with it.

So there's the challenge of building the space-rated devices, with all the testing. It's got to have independent power, have a set of tests defining "it goes" and not, and you've got to consider that LEO isn't really space, it's freefall in a gravity well and magnetic field with tenuous atmosphere. And it's expensive!

That will all take a lot of bench testing. So the project needs access to shielded, vacuum rated facilities, and so on. Testing satellite engine concepts with a 2D model (effectively a huge air hockey table) is also common. This would all be done to both build the satellite and to prove the concept. So they need to do the bench work first.

Re: NASA: EM Drive really does work

#20

Post by Rooster61 »

andygates wrote: post #17
cloudsloth wrote: post #13

Forgive me if I'm being obtuse, but can't someone just put am EM drive in space and see if it goes?

Lightsail (which uses regular physics) is doing that, launching a breadbox sail and a second proximity measuring cubesat along with it. So there's the challenge of building the space-rated devices, with all the testing. It's got to have independent power, have a set of tests defining "it goes" and not, and you've got to consider that LEO isn't really space, it's freefall in a gravity well and magnetic field with tenu…

> it's freefall in a gravity well

Bit of a nitpick, but this is true of any object in "space", at least on sub-galactic scales. If it wasn't in freefall around Earth, it would be in freefall around the Sun, and if not that, the Milky Way.

You are correct about the magnetic field and magnetosphere however.

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