The researcher has been pushing this claim for quite a while.
The experiments to measure the tiny force from the thrust have to be done VERY carefully to eliminate sources of experimental error- you are trying to measure a very small effect in an experimental setup that has high electrical currents.
There is no evidence that he has performed the experiment carefully and has understood and eliminated all possible sources of experimental error. There is no publication from this group that rigorously (and with peer review) demonstrates that all possible effects have been accounted for.
Meanwhile, others that HAVE gone to great lengths to understand and eliminate every possible source of experimental error.They have published in peer reviewed articles.
Their work shows that the purported propulsion simply is not there, and they are able to point to many possible sources of experimental error that could explain the force that Buhler claims to have seen.
This - coupled with the fact it violates conservation laws- makes it a safe bet that this electrostatic propulsion simply is nonsense.
I cannot explain why Buhler would make these wild claims- it makes no sense that a scientist would destroy his credibility in order to get 5 minutes of internet hype... But we have seen that there are those who will do exactly that. I don't understand it, yet it happens over and over...
In general, when someone making remarkable claims goes to great lengths to repeatedly emphasize they previously worked at NASA it makes me suspicious... the work should stand or fall based on the data, not based on someone's CV. Yes it appears he did work for NASA, so what? It smells too much like argument based on authority.
If the work was available for thorough peer review, and if it had been replicated in rigorous experiments then I might be interested...
Furthermore, while writers of popular science articles are often notoriously bad at over-hyping claims, it is clear that Buhler is doing all he can to ensure his claims are over-hyped.
Buhler says they commonly measured the forces in milliNewtons, but they prefer to describe the thrust in terms of gravity since that is the ultimate goal of propulsion physics.
That is just stupid... If you have a tiny force then -no matter how small it is- you can find a mass small enough so that it will have a large acceleration when subjected to that force... there is zero value in expressing the results in terms of acceleration... No value UNLESS you want to have headlines proclaiming that 'Buhler's propulsion can overcome the Earth's gravity!!!!' which is the way many of the pop science articles announced it....
So yeah... don't buy what he is selling....