blog.wired.com — To say that the "Emdrive" (short for "electromagnetic drive") concept is controversial would be an understatement. According to Roger Shawyer, the British scientist who developed the concept, the drive converts electrical energy into thrust via microwaves, without violating any laws of physics. Many other researchers believe otherwise.
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bigmanoncampusSep 24, 2008
From emdrive.com:"If the same EM wave is travelling at a fraction of the speed of light, the rate of change of momentum, and hence force, is reduced by that fraction. The propagation velocity of an EM wave, and the resulting force it exerts, can be varied depending on the geometry of a waveguide within which it travels."But... if relativity (Einstein) says that light always travels at c, and photons have "no mass" (question mark here) then how exactly do you reduce the momentum of an EM wave? We know that the group velocity of an EM wave can be reduced inside of different mediums, but that would seem to gain you nothing because as soon as it leaves said medium, it travels at c again. We know that light does transfer momentum when it hits objects, we know this. It is why we have tried the possibility of using a "solar sail" in space. However, his simple explanation on his website for why he gets a transfer of forward momentum from photons generated on his ship leaves a little to be desired.That said, I have seen another drive concept that uses only light to gain momentum, and this one actually works, but it doesn't use microwaves, and it has never been scaled up.
angryredplanetSep 25, 2008
The fact that a Chinese military scientist has picked it up and is actively developing it gives it some credibility. Watch this space.Propulsion techniques involving small thrust generally don't work well in non zero gravity situations, so demo-ing this near Earth wouldn't result in a spectacular result. The Emdrive has some distinct advantages over "conventional" drives like the fact that it can work without using any propellant and can keep working providing it is powered.
gn0stikSep 25, 2008
Yes, it has been widely replicated, and even improved upon. Even the DoE have retracted many of their previous negativity about it. However, there is still no common consensus of what is really going on. The presence of tritium ash is a pretty big blow to the nay-sayers, but it's still far from being proven beyond a reasonable doubt. I'd like to see that show, however.
catbellerSep 26, 2008
It'll cost two trillion. You have to factor in the cost of lifetimes of care for the broken men and women, and the cost of maintaining all those bases in Conquered Iraq.
Closed AccountSep 26, 2008
China inventing something? No way!They either lied about it or stole it.
bighairSep 27, 2008
yes, that is a good idea. haha
principleSep 28, 2008
<a class="user" href="http://en.wikipedia.org/wiki/Dean_drive">http://en.wikipedia.org/wiki/Dean_drive</a>I have seen a similar device that used counter-rotating weights. The claim was based on lack of a restriction on conservation of inertia unlike conservation of momentum.