[Kryptid (OP)]

Alright, so have you guys heard of a lifter/ionocraft? Here's some information if you need it: http://en.wikipedia.org/wiki/Ionocraft

Well 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 m²(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 m² (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?

[JP]

Looking at the links at the bottom, it seems as if the current, I, is the corona current, i.e. the current of ionized air.  You'll need massive voltage to convince the air to conduct 1.7 A of current.

[yor_on]

Yes Supercryptid. We definitely need to build those. As I have some defense contacts I've been able to procure this instructive film footage for your viewing pleasure.
We need this..

[lyner]

3MV/m is needed to produce ionisation of air. For a 1cm gap, this implies that you would need something like 30kv. With a sharply pointed electrode, this could be less but it would have to be about 15kV.
Your 1.5V cell can provide, say, 1A  - which is 1.5W. The current for 1.5W at 15kV would be only 0.1mA. That's the sort of current which your 1.5 cell could provide at high voltage and is what you should use in your calculations. (I haven't included the inefficiency of the voltage converter circuit here)
I think that makes the force about 6mN.

[yor_on]

Take look at this page, it's more than I ever needed to know about this.

http://blazelabs.com/l-intro.asp#peek
And this one is good too.
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20040171929_2004178266.pdf

[Kryptid (OP)]

3MV/m is needed to produce ionisation of air. For a 1cm gap, this implies that you would need something like 30kv. With a sharply pointed electrode, this could be less but it would have to be about 15kV.
Your 1.5V cell can provide, say, 1A  - which is 1.5W. The current for 1.5W at 15kV would be only 0.1mA. That's the sort of current which your 1.5 cell could provide at high voltage and is what you should use in your calculations. (I haven't included the inefficiency of the voltage converter circuit here)
I think that makes the force about 6mN.

3MV/m? Can you point out a source for that?

[lyner]

Yes - you can find it on the link yor_on has given you!

[theSloth]

Craft hinder your understanding and the fine tuning of your tech. Construct a model wherupon you can measure the thrust pressure of your model, and adjust distance between terminals, voltage and such . So your coils will be likely horizontally or vertically mounted with some form of vice or the like affixing your positive and negative coils (or molded)/ electrodes. Because your thruster is not bouncing around on thread, its function will be far more stable, and with things other than air not moving you're far less likely to fry your gear, environment or self in experiments.

Also, while the science community has concluded that placing the thruster within a housing negatively impacts efficiency, I wouldn't be so sure. A housing may allow for shaping resulting airflow, as well as providing mounting space for magnetic field projection hardware which I feel will allow for more energy imparted to airflow about the coronal coil and attractor blade. I won't overplay my hand too far, but consider mechanisms like wartenburg wheels to initiate coronas in a cylindrical housing with variable intensity electromagnets generating field constriction in the place of a concurrent jet turbine's internal shaping for similar effect. The airflow itself will spin your wartenburgs, and multistage electrohydrodynamic corona are as yet poorly explored. Try *layers of oppositional spiral airflow "sleeves" to funnel compression.

Science for fun, and profit for the future!

Corrected for redundancy