How does Shawyer get v = group velocity in his "emdrive"? The "v" is the velocity of the charge, not the wave, and is << c.
I still cannot come up with an other analogy for how the em drive works other than the mach thruster also discussed on this thread. Emdrive approaches the problem from the point of view of a varying velocity and mach drive (woodward drive) relies on varying mass. The end result is the same though - forward motion.
"And, 400 watts from a cork sized battery? I don't have access to this technology. Is this actually a capacitor battery, one that you charge the heck out of and then can use to power the thrusters?"Yes, these are the new batteries from A123 that will be powering the next generation of electric vehicles like the Chevy Volt. I picked up a test kit with 3 of these cells a year or two ago and sent it to a PhD EE friend who benched them for me. They do indeed put out over 400 watts each and have a C rating of more than 40. But they're batteries, not supercaps. The barium titaniate "supercap" technology from EEStor is reported to have an even higher power density but that's not on the market yet.
And BTW, yes I know GOCE doesn't have the Isp of Deep Space 1, but for a first application of a low thrust efficiency M-E thruster, we are probably looking at satellite station keeping, not robotic travel to Jupiter's icy moons. So GECO really is the more applicable technology to compare against. So far, the discovery phase lab experiments seem to have a huge advantage over the cutting edge-tech on GECO.Someone tell me if I remember correctly--NASA spends $50 million annually boosting hydrazine to ISS to keep her on orbit? If we had commercial thrusters with efficiencies like what Paul saw, we could replace all the hydrazine on ISS and save about half a billion dollars over the course of a decade. That's just one application.
"The issue of hydrazine handling and leakage alone should make the case for this (not that we can't handle hydrazine, it's just a pain in the rear and always will be). And add to that no need for a clear line of thrust and no risk of exhaust contamination of experiments... this would be an awesome system. Especially if the caps could be made to last longer (replacement every 6 months or so). "There's a huge amount of utility in the fact that gravinertial thrusters don't have to be placed outside a spacecraft. Since they have no exhaust, you can place them anywhere you please and this makes up-keep much easier.
So far as the die-off issue is concerned, we haven't had the finances to do destructive analysis of played out thrusters, but this appears to concern things like depolarization. If that proves to be the case, then using non polarized ceramics like PMT-PT will solve the issue all at once. It still seems very likely M-E thrusters will have no ageing issues once they go online.
The notion of "group velocity" is not intended for book-keeping momentum. If you want to talk about the momentum of light, you have to talk about photons and they always move at c. Group velocity has nothing to do with momentum and Shawyer's device is indeed proposing a violation of conservation of momentum.Lots of physicists have looked at this and there's a reason Shawyer lost his funding from the British government. His physics is wrong and his thruster has nothing in common with M-E thrusters.
They are durable but we've had thrust die-off issues in the past and the ageing here is well in advance of normal ageing in normal use of these caps. There's something going on we haven't had the opportunity to check into yet. We do know that if you bake the caps they return for a time to their original abilities but they die off again. So what is going on here? These caps are not generally polarized to start. Could the thrust be forcing the tetrahedrons off axis so that instead of a chaotic, generally unpolarized state they are polarized off axis? We haven't even taken the opportunity to polarize these caps for a single run though, that is easy to do when the time comes.There are other possibilities. What if the mobile ions are quantum tunneling out of the lattice while they're fluctuated light and moving fast? That would leave a net charge on the lattice and once again, we haven't had the time and resources to check. The ultimate in destructive analysis is to stick a failed cap under a scanning electron microscope--easy to do if you have the funds. . .
Quote from: GI-Thruster on 04/20/2009 03:17 pmYou can find some of the papers here:http://physics.fullerton.edu/Woodward.html. . .Unfortunately, I am leaving in a few days for a 3 week stint at a caving expedition to Mexico (http://www.usdct.org if you are interested--and no I am not insane enough to dive in-cave), so it will be a while before I can sit down and really absorb them. Anyone know if Blazotron made it out of the cave alive?
You can find some of the papers here:http://physics.fullerton.edu/Woodward.html. . .Unfortunately, I am leaving in a few days for a 3 week stint at a caving expedition to Mexico (http://www.usdct.org if you are interested--and no I am not insane enough to dive in-cave), so it will be a while before I can sit down and really absorb them.