[PSUBS-MAILIST] Hydrogen Peroxide: on to the topic of flywheels

["Gary R. Boucher" <protek@shreve.net>]

Wade,

At 10:15 PM 7/26/00 , you wrote:
>Wow,
>I think we must be talking about a fairly different size of flywheel.  19000
>feet?  That's crazy.  I'm guessing the fellow didn't survive.  I think that
>most of the flywheels proposed for HP subs were fairly small and were simply
>intended to give a good burst of acceleration off the line and to keep the
>propeller turning at a constant rate (same sort of application as the one in
>any automobile).

     The 19,000 foot figure was simply used for reference to demonstrate 
how much energy a flywheel powered car can store.  If Popular Science had 
given the energy in Joules, most readers would have said, "Oh, xxxx 
Joules...  What's a joule?"  By saying that the energy was enough to lift 
the whole car to so many thousand feet the reader got a better 
picture.  The energy is directly proportional to the mass of the wheel, but 
proportional to the angular velocity squared.  If you double the rotational 
speed you raise the energy by a factor of 4.  If you double the mass the 
energy goes up by 2.  The trick is to get the highest speeds for rotation 
even if you have to sacrifice some mass.  This can be done by generating a 
flywheel that is not cylindrical.  It is thicker in the center than on the 
edges.  If you don't do this, less energy is stored before the FW material 
"flies" apart.  At these very high rotational speeds the mechanical linkage 
is difficult.  Sometimes, flywheels have been used to generate electricity 
which in-turn drives a motor.  The problem is the angular momentum.  The 
flywheel acts like a giant gyroscope when the vehicle tilts or relocates 
the axis of the FW.  Therefore, if their are two identical flywheels 
turning in opposite directions this effect is totally eliminated.
     Once again, this is a very exotic form of energy.  The only reason 
that I ever considered it for subs was the fact that weight is not always a 
problem in a sub as it is in an automobile.  Right now, for most Psubbers 
conventional batteries offer the best source of energy.  It's interesting 
to think about exotic power sources, but the standard ones should be where 
most people focus.

Gary Boucher