Numerous bodies orbiting loop help
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sweetdreams
on 23 May 2015
Answered: Walter Roberson
on 23 May 2015
I've recently finished making a simulation of one body orbiting a stationary one. However I would like to extend it to more than 2 bodies like 50 or more. I would like to use a for loop instead of copying bits of code 50 times over. However this is where I'm stuck. I have an idea of what to do but I don't know how to code it.Any help will be appreciated :)
This is my function code:
function [ de ] = orbit(t,y)
de = zeros(4,1);
%Position
xx=y(1);
yy=y(2);
%Radius
r=(xx.^2+yy.^2).^0.5;
%Constants
M = 4E30; % mass
G = 6.67384E-11;
%dX/dt
de(1) = y(3); %vx
de(3) = (-G.*M.*xx)/(r.^3); %ax
%dY/dt
de(2) = y(4); %vy
de(4) = -G.*M.*yy/(r.^3); %ay
end
and call code:
x0=149.513e9;
y0=0;
vx0=0;
vy0=29.78e3;
trange=[0:1:100]; %time range to be solved for
p0=[x0;y0;vx0;vy0]; %assemble an intial p
[tarray, parray] = ode45(@orbit,trange,p0);
x=parray(:,1);
y=parray(:,2);
plot(x,y)
xlabel('x');
ylabel('y');
title('y=f(x)');
4 Comments
Walter Roberson
on 23 May 2015
Your posting is incomplete for the same reason that your previous exactly-the-same postings were incomplete: you do not indicate what you want to be looped over. For example should exactly the same equations be used each time but you want to use different initial positions? Or do the masses change?
Accepted Answer
Walter Roberson
on 23 May 2015
function [ DE ] = orbit(t,Y)
y = reshape(Y,4,[]);
de = 0 * Y;
%Position
xx=y(1,:);
yy=y(2,:);
%Radius
r=(xx.^2+yy.^2).^0.5;
%Constants
M = 4E30; % mass
G = 6.67384E-11;
%dX/dt
de(1,:) = y(3,:); %vx
de(3,:) = (-G.*M.*xx)./(r.^3); %ax
%dY/dt
de(2,:) = y(4,:); %vy
de(4,:) = -G.*M.*yy./(r.^3); %ay
DE = de(:);
end
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