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question, how is a millinewton defined?

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Rex R

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is it the force required to accelerate 1g to meter per second? I ask because tests show that the 'emdrive' can generate 1.2 millinewtons per kilowatt...maybe Estes should do like battery makers and rate the mini motors in millinewtons :).
Rex
 

OverTheTop

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is it the force required to accelerate 1g to meter per second?
Nearly. It is the force required to accelerate a mass of 1g at a rate of 1 m/s/s ( 1 m/s2).

So a force of 1mN would accelerate 1g from rest to 1m/s in one second. That's about 2.2mph.

Let's make some assumptions. The average fart has been shown to be around 4psi in pressure. Assume a sphincter diameter of 3/32" on release. On flipping these numbers into SI units and bringing them back again, I get about 0.4 ounce-force at the orifice (assuming I haven't stuffed the calcs).

For comparison, our 1mN force is about 0.004 ozf.

So I think you could call 1mN about the same as a sparrow's fart. Not sure what pressure they have so I can't make an official calculation. We could assume the same pressure as humans, but I definitely have no idea about the sphincter area. Never been that close and personal to a sparrow.
 

fyrwrxz

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ZC beat me to it! Diet may have an effect.
 

Nytrunner

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I'd just call it 1 thousandth of a Newton.

And fortunately I wasn't eating lunch when I read OvertheTop's fart analysis method. Otherwise I'd be passed out atm from choke/laughing.
 

rharshberger

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I was eating and the fart comparison required me to break out a ktchen towel to clean up the mess! 😆
 

ThirstyBarbarian

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I guess this explains why sparrows have to flap their wings and can't just rocket around like they have a pulse jet up their behinds.
 

Rex R

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okay that is what I thought, thank you. interesting bit trivia, nasa tested the EmDrive at a max of 80 watts, guess they got less than a gnat fart of thrust :).
Rex
 

OverTheTop

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Although they only produce a small thrust currently, these drives really come into their own for long duration flights. The integration of a small acceleration over a long time can end up with some serious velocity.

There are other propulsion methods being worked on, some of them seriously weird. A good book on the subject (although a couple of years old now) is:
"Frontiers of Propulsion Science"
412Y+Sm5CRL._SX332_BO1,204,203,200_.jpg

http://arc.aiaa.org/doi/book/10.2514/4.479953?mobileUi=0

It is a good read.
 
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