Author Topic: EM drive could be realistic after all  (Read 575 times)

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Offline SCarpelan

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EM drive could be realistic after all
« on: July 21, 2016, 02:07:23 am »
Electromagnetic drive was originally proposed by Roger Sawyer already  in 1999. It works by feeding light at microwave lenghts into a cavity where it bounces around and creates thrust. Some scientists have claimed they have succesfully created observable thrust with this method. Unfortunately, since there has not been any detected exhaustion this seems to break Newton's third law: everything has an equal and opposite reaction. It has naturally been deemed more probable that the observed thrust has been due to interference in the measuring equipment than a positive result that breaks a fundamental law of physics.

Now, a paper has been published that shows how the drive could actually work without breaking this law. The paper suggests that the exhaust is photons coming out in pairs that are out of phase. This means that these pairs cancel each other's electromagnetic signature out and they are not detected with the commonly used equipment. An interferometer could be used to detect these photons and if they are successfully detected it will result in people starting to take the engine seriously and probably put serious resources in developing it further.

This is one of those ideas that could revolutionize space exploration if anything usable comes out of it. An EM drive doesn't need the huge and heavy fuel supply that the current drives use and is therefore much faster. For example, according to Sawyer's calculations the trip to Mars could take only 70 days.

Offline Tolpuddle Martyr

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Re: EM drive could be realistic after all
« Reply #1 on: July 21, 2016, 02:50:51 am »
Ok, but do these sneaky, out of phase photons pack as much oomph as rapidly expanding hot gas?

Offline SCarpelan

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Re: EM drive could be realistic after all
« Reply #2 on: July 21, 2016, 07:11:36 am »
It doesn't need to pack nearly as much oomph since it has so much less mass to accelerate. Of course, the expanding gas would still be needed to get the drive and its payload to the orbit. I'm skeptical myself about anything coming from this but it is an interesting possibility. I read about this a couple of years ago but back then it seemed to be an obvious dead end due to the whole Newton's third law issue. Now there is an explanation for the measurements that is based on calculations using known physics so I'm waiting what the physicist community says about the new proposal.

Offline RavynousHunter

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Re: EM drive could be realistic after all
« Reply #3 on: July 21, 2016, 09:28:08 am »
Ok, but do these sneaky, out of phase photons pack as much oomph as rapidly expanding hot gas?

Even if they don't, they don't have nearly as big an environmental impact.  Combine it with a high-altitude launch, and the engine needn't be large at all, saving space for more useful things.  Wonder if you could power one off an RTG/RSG...
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Offline rookie

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Re: EM drive could be realistic after all
« Reply #4 on: July 21, 2016, 04:23:09 pm »
Could this be the start of jet packs?
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Offline TheContrarian

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Re: EM drive could be realistic after all
« Reply #5 on: July 22, 2016, 01:19:10 pm »
Ok, but do these sneaky, out of phase photons pack as much oomph as rapidly expanding hot gas?

Even if they don't, they don't have nearly as big an environmental impact.  Combine it with a high-altitude launch, and the engine needn't be large at all, saving space for more useful things.  Wonder if you could power one off an RTG/RSG...

Um, no?

The thrust from something like this would be comparatively tiny.  It's great for low acceleration in space over a long timescale, but as for getting out of earth's gravity well from the surface?  Not so much.


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Offline RavynousHunter

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Re: EM drive could be realistic after all
« Reply #6 on: July 22, 2016, 05:10:18 pm »
Derp...forgot those things output like a little DC motor.  Though, something like this does lend itself well to things like HTGRs (since they commonly use non-combustible CO2) and solar backups.
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