EmDrive: China claims success with this 'reactionless' engine for space travel
popsci.com
popsci.com
DC cavity currents were not listed as a potential error source, but these phenomenon could show up with high power and high Q.
Anyway, I just emailed a couple of the NASA guys; see what they say.
So far the tests have been static torque? Could there be an interaction with the earths magnetic field?
No one has any funding to research it. Despite the press, no major research agency is backing efforts to investigate the effect.
Cold fusion actually did get serious funding back in the 80s, which made it 'higher profile' to the scientific community.
I'll add that cold fusion seemed more plausible. In that it did not violate extremely well understood fundamental principles of physics, e.g. conservation of momentum. While incorrect, cold fusion was at least on the face of it a sensible inquiry at one time.
The EM drive has extremely compelling reasons to ellicit extreme skepticism from the scientific community at large.
Cold fusion violated the fundamental principle of 'Where are all the dead grad students caught up in the neutron flux?'.
So every time a positive result turns up incrementally more effort will be applied to test it, assuming the new result improves on previous ones.
Seems like a reasonable approach to me.
Gravity doesn't act at large distance. If you have a star like the Sun, it modifies the gravitational field locally. The modifications travel for a while and when the modification hits a planet like the Earth it applies a force to the Earth and modifies it's direction. The modifications are like the gravitational waves that have been recently measured. They travel at the speed of light.
If you have a force that can truly act at distance, you can use it to transmit information faster than light and it will break special relativity.
Let's analyze a similar case. The weak nuclear force is transmitted by the W+, Z0 and W- particles. They live approximately 1E-25 seconds. Assuming they travel near the speed of light, they can travel 3E-17 meters. That is a very small distance
You can think that an electron and a neutrino at 3E-17 meters can somehow interact at distance, because it's very small. But this is not true. The electron has to create one of the W+, Z0 and W- particles, send it to the neutrino, and the neutrino has to absorb it. Even 3E-17 meters is a long distance here, and it's possible to measure indirectly the properties of the intermediate particles.
If the Em-Drive device somehow interacts with the floor, walls or the Earth that are a few inches away, this is a extremely very big distance for the current theories. The Em-drive must interact with some kind of field and create some intermediate particles, like photons, gravitons or some new particle.
The problem is that if the Em-drive using some field and particles to conserve the energy and momentum locally, then the maximal theoretical output of a device that don't break the currently accepted physics laws is 1/c = 0.0033 mN/KW. I couldn't find in this article the experimental results in China, but it the recent "successful" experiment in NASA measured 4000x this value. [In my opinion, it was an experimental error.]
Getting 0.0033 mN/KW is "easy" with a perfect light source, like a perfect laser. Less is easier with a real light source, like a real laser. More is theoretical impossible with the current physics laws.
But the new physics would have to be fairly narrow since the standard model is fairly well-tested and consistent with most observations.
Anything that asymmetrically radiates photons will generate a net acceleration. This very mechanism has been experimentally verified as the pioneer acceleration anomaly.
If the emdrive is some kind of special case of this mechanism, it's entirely compatible with existing physics. The proposals so far are based on mechanisms which are different, and incompatible with the existing understanding of the universe.
It's also worth noting that in 2016 the Chinese research team was unable to replicate their findings after accounting for a power cable that was magnetically inducing a force on the experimental apparatus.
Now, the emdrive people are apparently claiming that it is truly reactionless. If so, you can build a perpetual motion machine of the first kind (produces energy from nothing) out of it --- which should demonstrate the degree of plausibility of such claims.
For photon rockets, there's apparently a hard upper bound on the efficiency, which limits the practical usability.
Some experiments just cannot be done properly in of our gravity well. EmDrive claims are tailored made for testing in space.
1. The magnitudes recorded in the several badly done experiments are very small and there are plenty of possible experimental errors.
2. The original inventor's own theory of how it works plainly violates very fundamental physics, like how all frames of reference are equivalent.
There is really no reason to think this will work, except hope. Still, it's a good idea to do some more research and put the idea to rest.
The equivalent in programming terms would be a program which nobody understands, and that some say can perform a comparison-based sort in constant time, but only for petabytes of data.