Demonstrate computing moving mass positions

Use a 100 m sail at 1 AU.

Since version 7.
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See also TorqueToCM, CMToMassPositions, Plot2D, SailPropsToAccel
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Contents

%-------------------------------------------------------------------------------
%	 Copyright 2009 Princeton Satellite Systems, Inc.
%  All rights reserved.
%-------------------------------------------------------------------------------

Define spacecraft properties

%-----------------------------
mass  = 200; % spacecraft mass in kg
lSail = 100; % sail length along one side in m

Ballast mass

%-------------
mBallast   = 1; % kg

Force is along x direction in sail body frame

%----------------------------------------------
area  = lSail^2;
acc0  = SailPropsToAccel( area, mass );
fMag  = acc0*mass; % nominal sail force
force = [1;0;0]*fMag;

Center of pressure offset

%--------------------------
Cp = [0;0;0];

Maximum torque - 75% traverse

%------------------------------
Tmax = 0.75*lSail/2*mBallast/mass*fMag;

Command torques in y and z axes

%--------------------------------
Tcommand   = Tmax*linspace(-1,1);
zz         = zeros(size(Tcommand));
cM         = TorqueToCM( [zz;Tcommand;-Tcommand], force, Cp );

Find the mass positions

%------------------------
mControl   = [mass-2*mBallast mBallast mBallast];
dOffset    = zeros(3,3);
uTrack     = [ [0;1;0] [0;0;1] ];
for k = 1:length(Tcommand)
  rhoCommand(:,k) = CMToMassPositions( cM(:,k), mControl, dOffset, uTrack );
end

Plot2D(Tcommand,rhoCommand,'Torque (Nm)','Distance (m)',...
  sprintf('Torque Produced by %.2f kg ballast mass',mBallast))

Center of pressure offset - assume a 0.25% standard dev

%--------------------------------------------------------
Cp = [0;randn(2,1)]*lSail*0.0025;
cM = TorqueToCM( [0;0;0], force, Cp );
rhoCommand2 = CMToMassPositions( cM, mControl, dOffset, uTrack );

disp('Center of pressure offset (random 0.25% of sail length):')
disp(Cp)
disp('Required center of mass to correct:')
disp(cM)
disp('Locations of in-plane masses:')
disp(rhoCommand2)

%--------------------------------------
% PSS internal file version information
%--------------------------------------

Center of pressure offset (random 0.25% of sail length):
            0
      0.13442
      0.45847
Required center of mass to correct:
            0
      0.13442
      0.45847
Locations of in-plane masses:
       26.883
       91.694

Published with MATLAB® R2020a