FSD- FLEXIBLE SPACECRAFT DYNAMICS

( NASA Goddard Space Flight Center )

     The Flexible Spacecraft Dynamics and Control program (FSD) was devel-
oped to aid in the simulation of a large class of flexible and rigid space-
craft. FSD is extremely versatile and can be used in attitude dynamics and
control analysis as well as in-orbit support of deployment and control of
spacecraft. FSD has been used to analyze the in-orbit attitude performance
and antenna deployment of the RAE and IMP class satellites, and the HAWKEYE,
SCATHA, EXOS-B, and Dynamics Explorer flight programs.

     FSD is applicable to inertially-oriented spinning, earth oriented,
or gravity gradient stabilized spacecraft. The spacecraft flexibility is
treated in a continuous manner (instead of finite element) by employing a
series of shape functions for the flexible elements. Torsion, bending, and
three flexible modes can be simulated for every flexible element. FSD can
handle up to ten tubular elements in an arbitrary orientation. FSD is ap-
propriate for studies involving the active control of pointed instruments,
with options for digital PID (proportional, integral, derivative) error
feedback controllers and control actuators such as thrusters and momentum
wheels.

     The input to FSD is in four parts: 1) Orbit Construction FSD calcu-
lates a Keplerian orbit with environmental effects such as drag, magnetic
torque, solar pressure, thermal effects, and thruster adjustments; or the
user can supply a GTDS format orbit tape for a particular satellite/time-
span; 2) Control words - for options such as gravity gradient effects, con-
trol torques, and integration ranges; 3) Mathematical descriptions of
spacecraft, appendages, and control systems- including element geometry,
properties, attitudes, libration damping, tip mass inertia, thermal ex-
pansion, magnetic tracking, and gimbal simulation options; and 4) Desired
state variables to output, i.e., geometries, bending moments, fast Fourier
transform plots, gimbal rotation, filter vectors, etc. All FSD input is of
free format, namelist construction.

     FSD is written in FORTRAN 77, PASCAL, and MACRO assembler for batch ex-
ecution and has been implemented on a DEC VAX series computer operating un-
der VMS. The PASCAL and MACRO routines (in addition to the FORTRAN program)
are supplied as both source and object code, so the PASCAL compiler is not
required for implementation. This program was last updated in 1985.

     COSMIC, and the COSMIC logo are registered trademarks of the National
Aeronautics and Space Administration. All other brands and product names
are the trademarks of their respective holders.



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LANGUAGE: FORTRAN 77 ( 99 %); PASCAL ( 01 %); ASSEMBLER ( 00 %);

MACHINE REQUIREMENTS: DEC VAX SERIES

PROGRAM SIZE: APPROXIMATELY 31,449 SOURCE STATEMENTS

DISTRIBUTION MEDIA: 9 Track 1600 BPI DEC VAX BACKUP Format Magnetic Tape

PROGRAM NUMBER: GSC-13006

DOMESTIC - DOCUMENTATION PRICE: $113.00    PROGRAM PRICE: $4000.00

INTERNATIONAL - DOCUMENTATION PRICE: $226.00   PROGRAM PRICE: $8000.00



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