Em drives

[Urwumpe]

There's a good reason for why I'm so skeptical about all of this: It flies in the face of all Physics, it's based on the same design, without any coherent theories and nobody can give a straight answer as to why it should work at all.

And we're not talking about some extreme case physical phenomenon here that would take a billion dollar particle collider to see. We're talking about radio waves and metal - something humans have been experimenting with and using for a hundred years.

Yes, sort of. But there is a lot of reason to trust science there: We never really understood until a Century ago, how birds can fly. Now we can even explain bumblebees.

 

[Fabri91]

As usual, a good article on the matter from ArsTechnica.com.

An excerpt:

In one experiment at 60 Watts of microwave power, the authors measure thrust of 128 microNewtons, while all three data points for 80 Watts of microwave power have thrusts of less than 120 microNewtons. Indeed, the thrust at 60 Watts for all data overlaps pretty much perfectly for all data taken at 80 Watts. They can only claim a slope by turning the power down to 40 Watts, where they do consistently measure less thrust.

 

[perseus]

Mike McCulloch of the University of Plymouth came up with a possible explanation on the basis of a new theory of inertia. He suggests that inertia emerges from an effect predicted by Einstein's theory of general relativity called "Unruh Radiation." The Unruh radiation effect states that if you are accelerating in a vacuum, the empty space will contain a particle gas at a temperature proportional to the acceleration.

When the accelerations involved are smaller, such as the EmDrive engine, the wavelength of the Unruh radiation becomes larger. At extremely small accelerations, the wavelengths become too large to fit into the observable universe.

As a result, inertia occurs only in units of wavelength all the time, causing it to become "quantified". "This means that it can exist only in some multiple of a unit of measurement, causing sudden jumps in acceleration."

But, because of the truncated cone of the EmDrive, the Unruh radiation is minuscule. The cone allows for Unruh radiation of a certain size at the large end, but only a smaller wavelength at the other end, according to an in-depth report by MIT

 

[RisingFury]

Yes, sort of. But there is a lot of reason to trust science there: We never really understood until a Century ago, how birds can fly. Now we can even explain bumblebees.

Birds and bees are well studied, with studies repeated over and over, with variations of planes flying in different ways. Also... birds do fly. That observation is solid.

I'm not convinced that EM drive even works, let alone what the theory behind it is. The observations behind EM drive are still inconsistent, with not even a clear relation between power and thrust. Imagine taking a wing and not getting the F = k * v^2 law out of it.

 

[Andy44]

 

[Urwumpe]

And another one against the EmDrive claims, this time from Dresden, Germany, with another replica of the thruster:

https://www.researchgate.net/public..._Results_on_EMDrive_and_Mach-Effect_Thrusters

Identified error sources in the low thrust measurements, that explain the observations there.

 

[boogabooga]

TL;DR- The EMDrive is actually just a compass.

 

[MaverickSawyer]

Looks like the "WTF" in "WTF thruster" stands for "Well, that flopped". :lol: