Alright, so have you guys heard of a lifter/ionocraft? Here's some information if you need it:

http://en.wikipedia.org/wiki/IonocraftWell anyway, there is an equation given on the page that tells you how to calculate the thrust produced by such a device:

F = (Id)/k

Where "F" is the force of thrust measured in newtons, "I" is the current measured in amperes, "d" is the air gap distance measured in meters, and "k" is the ion mobility coefficient of air measured in m

^{2}(V s).

I wanted to calculate how much thrust such a device could generate if it were powered by a AA battery. Wikipedia says that AA batteries can have 400 - 1700+ millamp-hours (0.4 - 1.7+ amp-hours), which I figure means that they can supply a current of 0.4 - 1.7+ amps for a period of 1 hour, right?

So here are the figures for a device with a 1 cm air gap:

I = 1.7 A

d = 0.01 m (1 cm)

k = 0.0002 m

^{2} (V s) (given by Wikipedia)

F = (Id)/k

F = (1.7 x 0.01)/0.0002

F = 0.017/0.0002

F = 85 newtons

Now, 85 newtons is about equal to 19.1 pounds of force. This seems to be

*way* too high. Ionocraft of this size are supposed to have a thrust-to-weight ratio too small to allow for an onboard power source to be carried. Yet AA batteries have a mass between 15 and 31 grams. The lifter's construction could also be made much under 19.1 pounds.

I must be doing something wrong.

What's the problem?