Frequently Asked Questions
From EM Drive
- Could the thrust be generated by microwave transmission?
- What are the experimental results regarding the EM Drives?
- See Experimental Results.
- Does the EM Drive violate momentum- or energy-conservation?
- See Energy Conservation and Momentum Conservation.
- How does an EM Drive work?
- Someone unknown posted:
- deltaMass has shown that Shawyer does not even understand that momentum is governed by the phase velocity, not the group velocity. Therefore any explanations for thrust (like Shawyer's) which are based on a difference between group velocities, are just plain wrong.
- TheTraveller responds
- deltaMass' assumption is just plain wrong as inside a waveguide, phase velocity is above c and momentum is governed by the group velocity or the guide waveguide:
- Phase velocity is an almost useless piece of information you'll find in waveguide mathematics; here you multiply frequency times guide wavelength, and come up with a number that exceeds the speed of light!
- Be assured that the energy in your wave is not exceeding the speed of light, because it travels at what is called the group velocity of the waveguide:
- Additionally Cullen has shown the reflection force generated on an endplate inside a waveguide is related to the guide wavelength or group velocity and not the phase velocity as claimed by deltaMass.
- The researchers at NWPU also agree with the Cullen 15 equation used by Shawyer and use it in their own calculations.
- So we have Cullen (backed by experimental data), Shawyer and NWPU all saying the level of the reflected Force on an endplate, in a waveguide, is related to guide wavelength / group velocity. Yet deltaMass says they are all wrong and it is related to phase velocity, which in a waveguide is above c and nothing travels above c.
The EM Drive researchers at NASA Eagleworks and Prof. Yang's team at Northwestern Polytechnical University (NWPU) in Xi'anin, China, have different theories of its operation:
Image of EmDrive thrust direction in posts attachment.
See the Theory page for a list of additional theories purporting to explain how the EmDrive works.
- Wikipedia has a lot of technical background.
- On Reddit, this subreddit has active discussion.