GEV on other worlds

I was thinking about extra-terrestrial settings / environments for DS2
and 
SG2 games this afternoon, and one thing I'm wondering about is GEV 
vehicles and how they might operate or what changes might be made to
them 
to allow them to operate.

First I'm just considering the effects of gravity and atmospheric
pressure.  Increasing/decreasing gravity changes the weight of the
vehicle
proportionately; increasing/decreasing the atmospheric pressure is what
I'm less certain about.  I would think that increasing the atmospheric
pressure would proportionately increase the ground pressure generated by
the GEV, so that if (for example) the vehicle is on a world with 1/2
Earth's gravity and 1/2 the Earth's atmospheric pressure, these two
factors effectively cancel each other out and the vechile operates more
or
less the same as on Earth.

Now this ignores things like air resistance and concerns re: combustion 
engines, but aside from that, do the effects of gravity and air pressure

work linearly and inversely to each other?

Does atmos. pressure have any effect on the engine / turbines?	If we 
consider a given volume of air being pushed through the system, does 
atmos. pressure matter?  I.e. 2x the pressure means the turbines spin
1/2 
as fast to push the same amount of air through, 1/2 the pressure means 
they spin 2x as fast, but in either case, the same volume is being
pushed 
through so the fuel / energy requirements are the same in either case.	
Right?	Of course taken to *extremes* (near vaccuum, dense as water) I
can 
easily see this breaking down, but otherwise...?

Cheers,
--Jerry

-- 
Jerry Acord [+] acord@imagiware.com [+] http://imagiware.com/acord