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There are the so-called ionocrafts based on the Biefeld-Brown effect, your suggestion sounds sort of similar. The thrust per unit area tends to be incredibly weak, but see here and here for some speculative proposals about actually using them for practical purposes, along with this NASA paper on the Biefeld-Brown effect.


As someone who has spent some time playing with gyros, I am very familiar (though on a non-mathematical level) with these objects. I have six battery powered high precision Gyros found here: http://www.gyroscope.com/d.asp?product=SUPER2 I have been intensely fascinated with the way they behave when spinning at maximum speed. I feel hesitant to comment ...


Rather than beating your student over the head with facts, try to approach the problem the way scientists did in the first place, by following the scientific method. Your student should come up with a hypothesis, and use known theory to make a prediction (calculate the momentum transfer in some idealized model), and then build a model to test the prediction. ...


Specific impulse is usually defined as $I_{sp} = \frac{F_T}{\dot m ~ g_0} $ That's true only if you use standard metric units. With force expressed in pounds-force and mass flow rate expressed in pounds, one simply divides the force (in pounds-force) by the mass flow rate (in pounds/second) and voila! you have specific impulse in lbf·s/lb. For example, ...

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