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Re: GEV capabilities

From: Adrian Johnson <ajohnson@i...>
Date: Mon, 16 Nov 1998 15:54:50 -0500
Subject: Re: GEV capabilities

>> Any GEV vehicle would require ducted fans or turbo fans to hop over
>>  obstructions, couter-act side tilt, etc. Ducted fans could be used
>>  VTOL craft, but still have bugs to work out. (After all helicopters
>>  NEARLY all the time)
>>	As far as side tilt rolling over a GEV, it isn't much different
>> rolling
>>  any other vehicle, except it slides instead of rturning turtle. The
>>  should be able to crab it up the hill at a reduced movement rate.
>The reason why hovercraft are so bad at climbing hills (except through
>momentum) is that as soon as you start moving up a incline, a component
>your lift thrust vector suddenly begins to push you down hill,
>your propulsion fans.	To overcome that you'd have to install almost
>thrust to make the whole thing fly, making it, in effect, a VTOL.
>Mike Jasinski

The Slammers' ground effect vehicles in the Hammer's Slammers novels
fans in ducts, but they don't adjust the duct position to change the
vector (correct me if I'm wrong here) - they selectively change pitch on
the thrust fans themselves (or maybe this in combination with
vanes/nozzles under the fan.  To go up a hill, they drop the thrust on
"up-side" fans, lowering that side of the vehicle, while increasing the
thrust on the "down-side" fans - the net effect is to add a much greater
lateral thrust component, reducing the "hill effect".  A significant
would be a real problem, though, because if you tip the vehicle too
you will let out the air cushion and the vehicle will ground.

If you have "power is no option" generators driving
"really-super-duper-effective" fans, you could say that the lift fans
the ability to *temporarily* provide direct lift (al la VTOL) for the
vehicle, in short bursts (to prevent damage to engines, bearings, etc by
prolonged overpowered running) - to overcome obstacles, short steep
etc.  You could use the same effect for braking (sudden high power in
direction opposite to that of travel) thereby removing the need for
drag-brakes (though the image of the driver pressing the "anchor" button
brings a smile).  I guess the air cushion would allow the vehicle to
in "fuel efficient" mode (or low-maintenance-needs mode?), while the
type movement would be used only in special circumstances.

The problem with considering vectored thrust fans on the underside of
type of vehicle is that if you vector the thrust into a confined space
attached to the vehicle (the air-cushion area inside the skirts), you
basically negate your thrust.  You need somewhere for the pressurized
from the fans to escape the confines of the vehicle, ie from one edge of
the skirts.  Maybe you vector the thrust and have vents in the skirts
up.  I don't imagine big propulsion fans on the outside of the upper
area (like today-era hovercraft) - 'cause these would be EASY to damage,
difficult to shield (from a thermal and radar standpoint), etc.    I
prefer the whole idea of countra-grav. technology.


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