Demonstrate a 2 satellite CubeSat constellation.

This simulation includes drag, solar radiation pressure, sun and moon perturbations, and a thruster model. Uses ode113 and FOrbitMultiSpacecraft. The simulation takes a few minutes and there is no waitbar; be patient!

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See also LabelLine, NewFig, Plot2D, TimeLabl, XLabelS, YLabelS, Skew,
Date2JD, CubeSatPropulsion, CubeSatAero, CubeSatRadiationPressure,
CubeSatFaces, FOrbitMultiSpacecraft, SolarFluxPrediction
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Simulation duration
Common fields
Initial state vector
Atmosphere data
Make a second copy for the second spacecraft
CubeSat face areas
Attitude model
Propulsion system for two CubeSats
Add surface models for both CubeSats
ode 113 parameters
Numerically integrate the orbit
Flip the matrices for plotting
Plot the xy-plane

%------------------------------------------------------------------------
%   Copyright (c) 2009 Princeton Satellite Systems, Inc.
%   All rights reserved.
%------------------------------------------------------------------------
% Since version 8.
% 2016.1: Update data structure format to match RHSCubeSat
%------------------------------------------------------------------------

d    = FOrbitMultiSpacecraft;

Simulation duration

%--------------------
days  = 0.5;
tEnd  = days*86400;

Common fields

%---------------
d.jD0           = Date2JD([2012 4 5 0 0 0]);
d.planet        = 'earth';
d.thrusterModel = @CubeSatPropulsion;
d.aeroModel     = @CubeSatAero;
d.opticalModel  = @CubeSatRadiationPressure;

Initial state vector

%----------------------
m0   = 1;         % Initial mass, kg
switch d.planet
  case 'moon'
    x0 = 3500;
    mu = Constant( 'mu moon' );
  case 'earth'
    x0 = 6500;
    mu = Constant( 'mu earth' );
end

x1   = x0;          % Orbit radius
x2   = x0 + 0.010;  % Radius with an offset
vY1  = VOrbit(x1,x1,mu);
vY2  = VOrbit(x2,x2,mu);

% State is [position;velocity;mass]
% CubeSats are 1 kg
%---------------------------------
r1   = [x1;0;0];
r2   = [x2;0;0];
v1   = [0;vY1;0];
v2   = [0;vY2;0];
x    = [r1;v1;1;r2;v2;m0];

Atmosphere data

%-----------------
% if you want J70, uncomment this.
% [aP, f, fHat, fHat400] = SolarFluxPrediction( d.jD0, 'nominal' );
% atm = struct;
% atm.aP = aP(1);
% atm.f = f(1);
% atm.fHat = fHat(1);
% atm.fHat400 = fHat400(1);
d.atm = []; % atm;

Make a second copy for the second spacecraft

%----------------------------------------------
d(2) = d;

CubeSat face areas

%-------------------
[a,n,r] = CubeSatFaces( '1U', 1 );
cM      = [0;0;0];

Attitude model

%---------------
att             = struct();
att.type        = 'lvlh';
att.qLVLHToBody = [1;0;0;0];

Propulsion system for two CubeSats

%-----------------------------------
thrusterData = CubeSatPropulsion();
d(1).thrusterData = thrusterData;
d(1).thrusterData.gas                 = 'nitrogen';
d(1).thrusterData.thrustCoeff         = 0.05/690000;
d(1).thrusterData.Isp                 = 68; % s
d(1).thrusterData.temperature         = 300;
d(1).thrusterData.volumeTank          = (4/3)*pi*0.02^3;
d(1).thrusterData.rNozzle             = [0.05;0;0];
d(1).thrusterData.uNozzle             = [0;1;0];
d(1).thrusterData.qECIToBody          = [1;0;0;0];
d(1).thrusterData.massDry             = 0.99;
d(1).thrusterData.pulsewidthFraction  = 1.0;
d(1).thrusterData.cM                  = cM;
d(1).thrusterData.att.calc            = false;
d(2).thrusterData                     = d(1).thrusterData;
d(2).thrusterData.pulsewidthFraction  = 0;

Add surface models for both CubeSats

%--------------------------------------
surfData = CubeSatAero();
surfData = CubeSatRadiationPressure(surfData);
surfData.nFace = n;
surfData.rFace = r;
surfData.area  = a;
surfData.cM    = cM;
surfData.att   = att;
surfData.rho   = [1 1 1 1 1 1;zeros(2,6)];
d(1).surfData  = surfData;
d(2).surfData  = surfData;

ode 113 parameters

%-------------------
opt   = odeset( 'AbsTol', 1e-7, 'RelTol', 1e-4, 'outputfcn', @ODETimeDisplay );

Numerically integrate the orbit

%--------------------------------
disp('Simulating with ode113. This will take a few minutes.');
tic
[t,x] = ode113( @FOrbitMultiSpacecraft, [0 tEnd], x, opt, d );
toc

Simulating with ode113. This will take a few minutes.
Elapsed time is 156.520460 seconds.

Flip the matrices for plotting

%-------------------------------
delT = diff(t);
[t,tL] = TimeLabl( t');
x     = x';

Plot the xy-plane

%------------------
dX    = x([1;2],:) - x([8:9],:);

NewFig('Simulation Timestep')
plot(delT);
YLabelS('Timestep (sec)')
XLabelS('Steps')
grid on

Plot2D( dX(1,:)*1000, dX(2,:)*1000, '\Delta x (m)', '\Delta y (m)', 'Two spacecraft XY-Plane' );
LabelLine( dX*1000, t, 10, ['- %4.1f ' tL(7:end-1)]  )

Plot2D(t,x(7,:),tL,'Mass (kg)','Fuel Consumption')


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