Hi!
I'm a relatively new FlightGear user and since I'm interested in
dirigibles and would want to fly those in FlightGear I have started
to implement some support for this in JSBSim.
My idea is to allow gas cell specifications to be added to the propulsion
part of a JSBSim aircraft description, like this:
<propulsion>
<gas_cell type="HYDROGEN">
<location unit="M">
<x> 0.5 </x>
<y> 0 </y>
<z> 15.0 </z>
</location>
<max_volume unit="M3"> 200.0 </max_volume>
<max_overpressure unit="PSI"> 0.0 </max_overpressure>
</gas_cell>
</propulsion>
The resulting buoyancy force from the cell would act on the aircraft at
the specified location (I know this is a simplification, but its a start).
Presently, I have a much simplified model of a gas cell (based on the
ideal gas law) and some code to include the gas cells in the state
computation of JSBSim.
However, sofar I have not managed to get the desirable behaviour (i.e.
lift-off) - if I add a gas cell to e.g. the c172p aircraft and increase
its volume it definitely affects the aircraft (like lift its tail) but if
the cell is large enough to lift it completely into the air the aircraft
just bounces a bit and then FlightGear decides that it has crashed.
My other (very poorly modelled) test vehicle (gas-balloon.xml) starts in
the air and just plunges to the ground regardless of the size of the gas cell.
If anyone has any idea of what might be the cause of the problems (e.g. if
some other module of JSBSim doesn't like floating aircraft or if I have
use the wrong coordinate transform) or have other comments, suggestions
and questions they are welcome. :)
(Some) More information and the patch for FlightGear-cvs (and
one for JSBSim-cvs) are available here:
http://www.gidenstam.org/FlightGear/JSBSim-LTA/
Best Regards,
Anders Gidenstam
--
"Luck is my middle name," said Rincewind, indistinctly. "Mind you,
my first name is Bad."
-- (Terry Pratchett, Interesting Times)
------------------------------------------------------------------
| Anders Gidenstam | Tel: 031-230645 070-296 1707 |
| Email: [EMAIL PROTECTED] | WWW: www.cs.chalmers.se/~andersg |
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