Re: Falling body software.

[brian whatcott <inet@intellisys.net>]

At 20:37 5/27/97 -0400, you wrote:
> A friend of mine has need of software to correctly simulate a body falling
> or projected from a great height near the earth, as, for example, the
> re-entry of a space satellite. The software must correctly deal with the
> height variation of the atmosphere's density, with shape and attitude of
> the falling body.
>
> Serious software for ballistics deals with the shape and attitude of the
> projectiole, but usually assumes constant atmospheric density during the
> trajectory. This is not acceptable.
>
> Does anyone here know of any such commercial software?
>
> 	-- Donald

Apparently the most serious exterior ballistics codes use the same method
as flight simulation, namely proceding by small differences over small
 time intervals. In the case of flight simulators, 33 milliseconds is not 
uncommon, and sometimes 17 milliseconds is used, except where great detail 
on fast internal movements is needed.

 FlightSimulator code  typically uses a theoretical atmosphere specified 
by the ICAO which is typical of the mid northern latitudes. 
It takes the tropopause to occur at 11000 meters up to which altitude 
it specifies a constant temperature lapse rate. 
Simulators make appropriate assumptions for non-standard day conditions 
(15degC at 1013.2millibars at mean sea level.)

   Given this level of idealization, and a (typically) constant value
for g is going to be acceptable, it seems to me that a representative 
flight simulator code of this kind, which I believe is freely available 
from a NASA server might provide a low-cost approach to ballistics.
 A query on the sci.aeronautics.simulation newsgroup would provide
a current URL, I suggest.

Regards
brian whatcott <inet@intellisys.net>
Altus OK