An idea that will not go to rest: The EM Drive

tomBitonti · Dec 1, 2016

Seeing a bit of discussion re: the EM Drive, which I thought we concluded was junk.

Not something worth much attention, except that the articles are in mainstream media, and presumably should have been at least minimally vetted.

The idea really seems to have gotten much more press than it deserves.

"This space engine breaks a law of physics. But a NASA test says it works anyway."
Washington Post, 22-Nov-2016, Sarah Kaplan

https://www.washingtonpost.com/news...-says-it-works-anyway/?utm_term=.c716a91badae

"Could Dark Matter Be Powering The EMdrive?"
Forbes, 30-Nov-2016, Ethan Siegel

http://www.forbes.com/sites/startsw...-matter-be-powering-the-emdrive/#20c085071e53

Thx!

TomB

Janx · Dec 1, 2016

Beats me. Tell me what to believe, else I'll wait until we have an EM driven spacecract going somewhere in actual space before I'll concern myself with it.

And even then, it's not like it concerns me. NASA isn't going to ask me for advice on their spacecraft, so how its powered isn't likely to matter to me.

Morrus · Dec 1, 2016

It seems like the effect size is so small that it fits into the range often considered statistical noise.

tomBitonti · Dec 1, 2016

Morrus said:
It seems like the effect size is so small that it fits into the range often considered statistical noise.

Yup.

Here are two links that discuss the idea:

"RF resonant cavity thruster"

https://en.wikipedia.org/wiki/RF_resonant_cavity_thruster

This follow-on by Greg Egan is an interesting read:

Footnot 15: Egan, Greg (19 September 2006). Baez, John C., ed. "A Plea to Save New Scientist". The n-Category Café (a group blog on math, physics and philosophy)

https://golem.ph.utexas.edu/category/2006/09/a_plea_to_save_new_scientist.html

Thx!
TomB

ccs · Dec 2, 2016

If it actually does work then our "laws of physics" were incomplete.

freyar · Dec 2, 2016

tomBitonti said:
"Could Dark Matter Be Powering The EMdrive?"
Forbes, 30-Nov-2016, Ethan Siegel

http://www.forbes.com/sites/startsw...-matter-be-powering-the-emdrive/#20c085071e53

The axion idea is kind of funny; while improbable, I guess it's not outside the realm of probability conceptually (though I haven't checked the numbers to see if it quantitatively makes sense). But the idea of using EM field conversion to axions to drive the ship is very silly since you'd get a lot more thrust just by beaming the photons out the back of the engine at no worse of an energy cost/delta v.