105 lines
2.6 KiB
C
105 lines
2.6 KiB
C
/***************************************************************************
|
|
|
|
TITLE: ls_gravity
|
|
|
|
----------------------------------------------------------------------------
|
|
|
|
FUNCTION: Gravity model for LaRCsim
|
|
|
|
----------------------------------------------------------------------------
|
|
|
|
MODULE STATUS: developmental
|
|
|
|
----------------------------------------------------------------------------
|
|
|
|
GENEALOGY: Created by Bruce Jackson on September 25, 1992.
|
|
|
|
----------------------------------------------------------------------------
|
|
|
|
DESIGNED BY: Bruce Jackson
|
|
|
|
CODED BY: Bruce Jackson
|
|
|
|
MAINTAINED BY: Bruce Jackson
|
|
|
|
----------------------------------------------------------------------------
|
|
|
|
MODIFICATION HISTORY:
|
|
|
|
DATE PURPOSE BY
|
|
|
|
940111 Changed include files to "ls_types.h" and
|
|
"ls_constants.h" from "ls_eom.h"; also changed DATA types
|
|
to SCALAR types. EBJ
|
|
|
|
|
|
$Header$
|
|
$Log$
|
|
Revision 1.1 1999/06/17 18:07:34 curt
|
|
Initial revision
|
|
|
|
Revision 1.1.1.1 1999/04/05 21:32:45 curt
|
|
Start of 0.6.x branch.
|
|
|
|
Revision 1.3 1998/08/06 12:46:39 curt
|
|
Header change.
|
|
|
|
Revision 1.2 1998/01/19 18:40:26 curt
|
|
Tons of little changes to clean up the code and to remove fatal errors
|
|
when building with the c++ compiler.
|
|
|
|
Revision 1.1 1997/05/29 00:09:56 curt
|
|
Initial Flight Gear revision.
|
|
|
|
* Revision 1.2 1994/01/11 18:50:35 bjax
|
|
* Corrected include files (was ls_eom.h) and DATA types changed
|
|
* to SCALARs. EBJ
|
|
*
|
|
* Revision 1.1 1992/12/30 13:18:46 bjax
|
|
* Initial revision
|
|
*
|
|
|
|
----------------------------------------------------------------------------
|
|
|
|
REFERENCES: Stevens, Brian L.; and Lewis, Frank L.: "Aircraft
|
|
Control and Simulation", Wiley and Sons, 1992.
|
|
ISBN 0-471-
|
|
|
|
----------------------------------------------------------------------------
|
|
|
|
CALLED BY:
|
|
|
|
----------------------------------------------------------------------------
|
|
|
|
CALLS TO:
|
|
|
|
----------------------------------------------------------------------------
|
|
|
|
INPUTS:
|
|
|
|
----------------------------------------------------------------------------
|
|
|
|
OUTPUTS:
|
|
|
|
--------------------------------------------------------------------------*/
|
|
#include "ls_types.h"
|
|
#include "ls_constants.h"
|
|
#include "ls_gravity.h"
|
|
#include <math.h>
|
|
|
|
#define GM 1.4076431E16
|
|
#define J2 1.08263E-3
|
|
|
|
void ls_gravity( SCALAR radius, SCALAR lat, SCALAR *gravity )
|
|
{
|
|
|
|
SCALAR radius_ratio, rrsq, sinsqlat;
|
|
|
|
radius_ratio = radius/EQUATORIAL_RADIUS;
|
|
rrsq = radius_ratio*radius_ratio;
|
|
sinsqlat = sin(lat)*sin(lat);
|
|
*gravity = (GM/(radius*radius))
|
|
*sqrt(2.25*rrsq*rrsq*J2*J2*(5*sinsqlat*sinsqlat -2*sinsqlat + 1)
|
|
+ 3*rrsq*J2*(1 - 3*sinsqlat) + 1);
|
|
|
|
}
|