Re: GEVs

>On  3-Dec-99 at 12:00, Bell, Brian K (Brian_Bell@dscc.dla.mil) wrote:
>> An interesting question.
>> A GEV must displace an amount of air equal to or exceeding its mass
in
>> order to hover. 
>> 
>
>Not quite, it must put enough pressure in the plenum that there is
>as much pressure on the ground as the mass of the GEV.
>
>> Perhaps I misunderstood the question, but it seems like you are
asking what
>> if you took a battleship that you know will float in Lake Erie and
put it
>> in a pond. It would sink because there is not enough water to support
it.
>> But then a battleship is not designed to work on both land and water
like a
>> GEV. 
>
>Let's get extreme so I can make my point.
>
>I have an 80 ton block of iron sitting on a 1 cm x 1 cm skirt.  This
skirt
>has air in it equal to 80 tons/cm^2.  I put it over the a 300 foot deep
>lake.	It's pretty obvious it will bubble wonderfully as it sinks to
the
>bottom.  We have to pay attention to wether our tanks will do this
also.
>If the pressure required to lift them is greater than what the water
will
>support they will sink.
 
I think this can be simplified to: If the pressure required to
support the vehicle exceeds atmospheric pressure, it will sink.
At some point, the weight of the surrounding water will be
sufficient to balance the supporting air pressure, but unless the
vehicle has tall snorkels, this won't happen until long after
the air intakes are flooded (which won't do the blades any good!).
 
>If our Slammer Tank sinks in water that means it is going to sink in
>swamp.
 
If the swamp is shallow enough that the displaced water can't
enter the air intakes, the vehicle should just displace the
water and muck until it reaches a solider base. If there is no
such solider base, it will sink until it the intakes are flooded.
'Course, I suppose one could design a vehicle to function as a
GEV on land and as a submarine in water. Stop the fans during
air to water transition, then restart them at a lower speed.
Moving from water to air would be a problem, though.
 
- Sam
____________________________________________________________
Samuel Reynolds
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