222 lines
8.2 KiB
Matlab
222 lines
8.2 KiB
Matlab
function balloon_output = create_balloon(balloon_input_filename)
|
|
% Authors:
|
|
% Brent Justice - justiceb@purdue.edu
|
|
% Ian Means
|
|
% Purpose:
|
|
% Design contour for zero pressure balloon
|
|
% With given mission criteria
|
|
% References:
|
|
% "A Parallel Shooting Method for Determining the Natural
|
|
% shape of a Large Scientific Balloon", Frank Baginski,
|
|
% William Collier, Tami Williams
|
|
%
|
|
% "Scientific Ballooning", Nobuyuki Yajima, Naoki Izutsu,
|
|
% Takeshi Imamura, Toyoo Abe
|
|
% Units:
|
|
% ALL calculations performaed in SI units. Only converted
|
|
% to english units for printing or plotting
|
|
|
|
%% Inputs (Mission Criteria)
|
|
load(balloon_input_filename) %load the following input parameters
|
|
%rho_PE --> kg/m^3 density of polyethlyene we purchased
|
|
%thickness_PE --> m thickness of polyethylene we purchased
|
|
%Wpayload --> N payload weight
|
|
%alt_apogee --> altitude at apogee (m)
|
|
%numGores --> number of gores
|
|
%R_gas --> gas constant of lifting gas
|
|
|
|
%constants (mission criteria and materials)
|
|
g = 9.81; %m/s/s
|
|
R_air = 287.058; %specific gas constant air (SI)
|
|
%R_H2 = 4124; %specific gas constant hydrogen (SI)
|
|
%R_He = 2077; %specific gas constant helium (SI)
|
|
|
|
%% float conditions (at apogee)
|
|
[rho_air,a_apogee,T,P,nu,ZorH]=stdatmo(alt_apogee); %SI (standard atmosphere)
|
|
rho_gas = P/(R_gas*T); %Ideal gas law, assume ambient pressure
|
|
a = 0; %distance from zero pressure line to base (0 for apogee)
|
|
k = (2*pi)^(-1/3); %constant of geometry
|
|
tb = 1; % == b/bd == 1 at apogee
|
|
rho = 1; % == w/wd == 1 at apogee
|
|
bd = (rho_air - rho_gas) * g; %effective bouyant force per unit volume at apogee (N/m^3)
|
|
wd = rho_PE * thickness_PE; %mass per unit area of PE at apogee (kg/m^2) [changes with altitude]
|
|
lambda = (Wpayload/bd)^(1/3); %shaping parameter (m)
|
|
epsilon = (2*pi)^(1/3) * wd * g / (bd*lambda); %shaping parameter []
|
|
a_dash = a/lambda;
|
|
|
|
%print sizing parameters in english units (easier to digest)
|
|
%fprintf('bd = %f lbs/ft^3 \n',bd / 157.087464)
|
|
%fprintf('Payload = %f lbs \n',Wpayload / 4.44822162)
|
|
%fprintf('lambda = %f ft\n',lambda*3.28084)
|
|
%fprintf('wd = %f lbs/ft^2 \n',wd *0.204816144)
|
|
%fprintf('epsilon = %f \n',epsilon)
|
|
%fprintf('Number of gores = %f\n', numGores)
|
|
|
|
%% Shooting method simulation for finding gore contour shape
|
|
%constant initial conditions
|
|
r0 = 0; %radius at base = 0
|
|
z0 = 0; %height at base = 0
|
|
S0 = 0; %area at base = 0
|
|
V0 = 0; %volume at base = 0
|
|
|
|
%final value conditions
|
|
r_end_condition = 0; %radius at apex = 0
|
|
theta_end_condition = -pi/2; %angle at apex = -90 (radians)
|
|
|
|
options = simset('SrcWorkspace','current');
|
|
%iterate
|
|
theta_end_error = 0.1; %set error high to enter loop
|
|
theta_0_guess = 60 * 0.0174532925; %angle at base (rads) [GUESS]
|
|
m0 = 2*pi*cos(theta_0_guess); %calculation dependant on guess
|
|
while abs(theta_end_error) > 0.00174532925 %while error high, keep iterating
|
|
r_end_error = 2; %set error high to enter loop
|
|
s_dash_end_guess = 2; %arclength of gore (m/lambda) [GUESS]
|
|
while abs(r_end_error) > 0.001 %shooting method until error for r is small
|
|
sim('natural_balloon',[],options) %run simulink model
|
|
s_dash = simout.time; %format sim outputs
|
|
z_dash = simout.data(:,1);
|
|
r_dash = simout.data(:,2);
|
|
S_dash = simout.data(:,4);
|
|
V_dash = simout.data(:,5);
|
|
theta = simout.data(:,3);
|
|
|
|
%Calcuate non-dashed values
|
|
r = r_dash*lambda; %m
|
|
s = s_dash*lambda; %m
|
|
z = z_dash*lambda; %m
|
|
S = S_dash(end)*lambda^2; %balloon surface area (m^2)
|
|
V = V_dash(end)*lambda^3; %balloon volume (m^3)
|
|
|
|
%calculate radius error
|
|
r_end_error = (r_end_condition - r(end));
|
|
theta_end_error = theta_end_condition - theta(end);
|
|
|
|
%Use interpolation to determine next guess
|
|
if exist('shoot1') == 0 %this was our first guess. We must pick a 2nd arbitrary guess
|
|
shoot1.A2 = s_dash_end_guess;
|
|
shoot1.Z2 = r(end);
|
|
|
|
s_dash_end_guess = s_dash_end_guess + 0.0001; %set next guess to our first guess + some small amount
|
|
else
|
|
shoot1.A1 = shoot1.A2;
|
|
shoot1.Z1 = shoot1.Z2;
|
|
shoot1.A2 = s_dash_end_guess;
|
|
shoot1.Z2 = r(end);
|
|
Zsol = r_end_condition;
|
|
a = Zsol - shoot1.Z1;
|
|
b = shoot1.Z2 - Zsol;
|
|
|
|
Anew = (a*shoot1.A2 + b*shoot1.A1)/(a+b); %calculate next guess based upon interpolation of previous 2 results
|
|
s_dash_end_guess = Anew;
|
|
end
|
|
end
|
|
clearvars shoot1;
|
|
|
|
%calculate theta_0 guess for next iteration using interpolation method
|
|
if exist('shoot2') == 0
|
|
shoot2.A2 = theta_0_guess;
|
|
shoot2.Z2 = theta(end);
|
|
|
|
theta_0_guess = theta_0_guess + 0.001;
|
|
else
|
|
shoot2.A1 = shoot2.A2;
|
|
shoot2.Z1 = shoot2.Z2;
|
|
shoot2.A2 = theta_0_guess;
|
|
shoot2.Z2 = theta(end);
|
|
Zsol = theta_end_condition;
|
|
a = Zsol - shoot2.Z1;
|
|
b = shoot2.Z2 - Zsol;
|
|
|
|
Anew = (a*shoot2.A2 + b*shoot2.A1)/(a+b);
|
|
theta_0_guess = Anew;
|
|
m0 = 2*pi*cos(theta_0_guess);
|
|
end
|
|
end
|
|
|
|
%% Calculate sea level hydrogen needed
|
|
m_gas = rho_gas*V; %kg --> mass of lifting gas needed
|
|
[rho_air_SL,a_SL,T_SL,P_SL,nu_SL,ZorH_SL]=stdatmo(0); %SI (standard atmosphere)
|
|
rho_gas_SL = P_SL/(R_gas*T_SL); %Ideal gas law, assume ambient pressure
|
|
V_gas_SL = m_gas / rho_gas_SL; %m^3 lifting gas Volume at Sea Level
|
|
|
|
%% Print outputs
|
|
m_PE = S*wd; %kg
|
|
m_payload = Wpayload / g;
|
|
arclength = s(end);
|
|
height = z(end);
|
|
fprintf('epsilon = %f \n',epsilon)
|
|
fprintf('balloon surface area = %f m^2 \n',S )
|
|
fprintf('balloon volume = %f m^3 \n',V )
|
|
fprintf('balloon volume = %f ft^3 \n',V *35.3147)
|
|
fprintf('balloon mass = %f kg \n',m_PE )
|
|
fprintf('payload mass = %f kg \n',Wpayload/g )
|
|
fprintf('total weight = %f N \n',Wpayload+m_PE*g )
|
|
fprintf('total lift = %f N \n',V*bd )
|
|
fprintf('lifting gas Volume at Sea Level = %f ft^3 \n',V_gas_SL *35.3147 )
|
|
fprintf('angle at apex = %f degrees (shoot for -90) \n',theta(end)/ 0.0174532925 )
|
|
fprintf('angle at base = %f degrees (shoot for -90) \n',theta(1)/ 0.0174532925 )
|
|
fprintf('radius at apex = %f m (shoot for 0) \n',r(end) )
|
|
fprintf('arclength of gore = %f m \n',arclength )
|
|
fprintf('\n')
|
|
|
|
f1 = figure(1);
|
|
subplot(1,2,1)
|
|
plot(r,z)
|
|
xlabel('radius to center of balloon (m)')
|
|
ylabel('distance from balloon base (m)')
|
|
grid on
|
|
axis equal
|
|
title('balloon gore contour at apogee')
|
|
hold all
|
|
|
|
%% Determine Gore Shape
|
|
goreTheta = (2*pi)/numGores; %radians rotation per gore
|
|
s_print = 0:0.1:s(end);
|
|
for n = 1:1:length(s_print);
|
|
r_print = interp1(s,r,s_print(n));
|
|
goreWidth(n) = r_print*goreTheta; %m arc length formula
|
|
fprintf('At %.1f cm from bottom, gore is %.2f cm from center\n',s_print(n)*100,goreWidth(n)/2*100)
|
|
end
|
|
|
|
subplot(1,2,2)
|
|
plot(goreWidth/2,s_print,-goreWidth/2,s_print)
|
|
xlabel('width (m)')
|
|
ylabel('length (m)')
|
|
title('Flat Gore Shape (stencil)')
|
|
axis equal
|
|
grid on
|
|
hold all
|
|
|
|
%% 3D plot
|
|
y = r;
|
|
x = z;
|
|
ni = length(x);
|
|
nj = 2*ni-1;
|
|
tt = linspace(0,2*pi,nj);
|
|
for i=1:ni
|
|
for j=1:nj
|
|
xx(i,j) = x(i);
|
|
rr(i,j) = y(i);
|
|
yy(i,j) = rr(i,j)*cos(tt(j));
|
|
zz(i,j) = rr(i,j)*sin(tt(j));
|
|
end
|
|
end
|
|
|
|
f2 = figure(2);
|
|
surfl(yy,zz,xx)
|
|
colormap(gray)
|
|
axis('equal')
|
|
xlabel('(meters)')
|
|
ylabel('(meters)')
|
|
zlabel('height (meters)')
|
|
title('Balloon Shape at Apogee')
|
|
axis equal
|
|
|
|
%% Output
|
|
w = whos;
|
|
for a = 1:length(w)
|
|
balloon_output.(w(a).name) = eval(w(a).name);
|
|
end
|
|
|
|
end
|