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So, photons exert a tiny force when they reflect off of something. I was thinking about the EMDrive yesterday, and how it supposedly uses radiation pressure for thrust. Then I had this ridiculously funny and impractical idea of how the EMDrive is supposed to work, according to the physics we know. It would best be explained by a picture:

8J8H2SA.png  

It would use mirrors as fuel, and would leave a stream of mirrors in it's wake as it slowly gets pushed along. It's completely impractical, but would work. I thought it was a funny idea...:P

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The ISP it will be given by the exhaust velocity that the mirrors can achieve.
Not sure if the mirrors mass matters or not in this scenery. It also depends on how you get your light-power source. 

I draw a different concept but taking advantage from the same bounce here.

This guy also thought in something similar.

https://www.youtube.com/watch?v=8Gr3UtCaREY 

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12 minutes ago, AngelLestat said:

The ISP it will be given by the exhaust velocity that the mirrors can achieve.
Not sure if the mirrors mass matters or not in this scenery. It also depends on how you get your light-power source.

The mirror's mass does matter, as they're basically the same as fuel in a chemical rocket. The light is a simple lightbulb using solar/nuclear energy. As more mirrors get ejected, the craft gets lighter, and goes faster. The light is provided inside the craft so it would be able to propel itself wherever you need but it produces extremely low thrust, creates Kessler syndrome with it's exhaust, and requires an immense number of mirrors to get anywhere, which reduces the thrust even more. I wouldn't count on the mirror drive being the next revolution in space travel, but it's a funny idea.

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13 hours ago, RainDreamer said:

So why not just use solar sail instead? XD

Because it would be funny to have mirrors as exhaust. I imagine a person shoving in new mirrors into the light chamber the way people would shove coal into a train engine way back in the day. :D Of course it would be really slow, and the person's job would be really boring, just move a mirror every so often, probably at least every several hours if not days or weeks. You'd be better off having all the people you don't need anymore jump as hard as they can off the back of the spacecraft :D That is, if you prefer moving your spaceship over having more people.

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One of the problems with this concept is that the mirrors move away from you, hence the frequency of the light is reduced by every passing. This effect is not that big, but the main advantage of this design over just beaming light away is that the light is reflected multiple times, so you gain more impulse by these multiple reflections. And after all these reflections, the frequency is reduced by a big amount, at least if the mirrors move with a reasonable speed. And the reduction of frequency leads to a reduction of impulse of the light and this seriously harms the efficiency of this construction.

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I'm assuming mirrors are made from metal foil. That's the only way to pack enough of them. In which case, I propose an upgrade to mirror drive's efficiency. Instead of converting electric energy into light, which tends to be pretty inefficient at required power levels, lets install a rail gun inside, and fire the mirrors using electromagnetic forces. :P

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23 hours ago, cubinator said:

Because it would be funny to have mirrors as exhaust.

More funny, take human waste, freeze it then use a mass accelerator to eject it backwards. Even more funny, take a focus gamma irradiator place it on a object then have is shine high energy gamma back at the ship to accelerate the ship and coincidentally killing everything on board. If we want to propel things on the Nelson-Hah-hah metric, we can do alot better than mirrors. How about a nuclear reactor that produces radioactive cobalt as its waste which it the mass accelerates for propulsion. Even better a ship that creates warp fields around two proximal adjacent bodies and hurls them backwards therefore propelling itself forward at near light speed (notably altering the orbits of the two celestials until eventually they collide). 

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