create a reentry trajectory in matlab

main.m
% Define physical parameters
m = 5000;       % mass (kg)
Cd = 1.5;        % drag coefficient
Cl = 0.3;        % lift coefficient
r_e = 6371e3;   % radius of Earth (m)
mu = 3.986e14;  % gravitational parameter of Earth (m^3/s^2)

% Define initial state
h0 = 100e3;     % initial altitude (m)
v0 = 5000;      % initial speed (m/s)
gamma0 = -5;    % initial flight path angle (degrees)
psi0 = 90;      % initial heading angle (degrees)

% Define simulation time span
tspan = [0 2000];   % simulation time span (s)

% Define function for vehicle's equations of motion
f = @(t,X) reentry_ode(t,X,m,Cd,Cl,r_e,mu);

% Set initial conditions
X0 = [r_e+h0; v0; gamma0*pi/180; psi0*pi/180];

% Simulate trajectory
options = odeset('RelTol',1e-9,'AbsTol',1e-10);
[T,X] = ode45(f, tspan, X0, options);

% Convert results to altitude/latitude/longitude coordinates
[lat,lon,alt] = ecef2geodetic(X(:,1), X(:,2), X(:,3), r_e, 0.08181919^2);

% Plot trajectory in 3D
figure
plot3(X(:,1), X(:,2), X(:,3))
xlabel('X (m)')
ylabel('Y (m)')
zlabel('Z (m)')
axis equal

% Plot altitude vs. time
figure
plot(T/60, alt/1e3)
xlabel('Time (min)')
ylabel('Altitude (km)')
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