Lander Loads Code

function Preliminary_Loads_trade_offs_2_5_13

%%

%{ Schemes to investigate:

Shaped airbags for impact attenuation with structure inside similar to an inner skirt for a hovercraft.

Conventionally shaped landing gear with:

conventional impact attenuation like aluminum honeycomb

OR

Gelled Hydraulic impact attenuation schemes using high temperature

silicone greases/gels.

This assumes landing while the moon is sunlit

%}

% FOR LANDING GEAR CONVENTIONAL LEGS

% total nominal craft mass

massTotal = input('How much is your payload? [in kg]: ', 's'); % kg

gravityMoon = 1.622; % m/s^2

gravityEarth = 9.81; % m/s^2

numberLegs = 3; %this is to start with, the basic 3 legged model, also 5

weightTotalMoon = massTotal*gravityMoon;

% craft diameter and radius

dCraft = 4.6;

rCraft = dCraft/2;

% height of the bottom of the lower propulsion module off the ground

h = 2;

FS = 1.5;

theta_l = 20:60;

% i = 1;

% theta_l = 45;

for i =  1:length(theta_l)

% Static Loads ?

craftWeightMoon = massTotal*gravityMoon;

F_leg = craftWeightMoon*FS/numberLegs;

F_leg_worst = craftWeightMoon*FS;

legForce = F_leg/(2*cosd(theta_l(i)));

legForceWorst = F_leg_worst/(2*cosd(theta_l(i)));

mainMemberLength(i) = h/cosd(theta_l(i));

% This is just a diagnostic value to show which of buckling bending etc

% will be our limiting force, we are not stuck with this moment of

% inertia

I_desired = 4e6;

% Pick a radius and back out the other to plug in and compare bending

% and buckling

% Bending Loads ?

%     rOut = 0:152.25;

%     rIn = 0:152.25;

%     [RIN,ROUT] = meshgrid(rIn,rOut);

%     I = (pi/4)*(ROUT.^4 - RIN.^4);

F=weightTotalMoon+Fdynamic;

sigma=F*(cosd(theta_l)/(pi*(rOut^2-rIn^2))+mainMemberLength*I*rOut);

% Buckling Loads ?

Ealum = 72e9; %Pa

Pbuckle(i) = ((pi^2)*(Ealum)*I_desired)/(1e12*4*mainMemberLength(i)^2);

% Dynamic Loads ?

%requirements for landing from last semester

%Maximum Touchdown Velocity: 3 m/sec vertical, 1.5 m/sec horizontal

velocityMaxVector = [1.5,1.5,3]; % m/s

velocityMax =norm([1.5,1.5,3]); % m/s

velocityOnSurfaceVector = [0,0,0]; % m/s

velocityOnSurface = 0; % m/s

dv = velocityMax - velocityOnSurface; % m/s

dvVector = velocityMaxVector - velocityOnSurfaceVector; % m/s

impulseTotalVector = massTotal*dvVector; % Newton seconds

% assuming we don't want more than 9.8 m/s^2 accel (1 earth gravity)

% to be felt in the cabin

accelMax = gravityMoon:3*gravityEarth; % m/s^2

for j = 1:length(accelMax)

for i = 1:3

dt(j) = dvVector(i)/accelMax(j); % seconds

end

end

for i = 1:3

Fvector(i) = massTotal*(dvVector(i)/dt(i));

end    F_dynamic = norm(Fvector);

KEVector = (0.5*massTotal.*velocityMaxVector.^2)';

KE = KEVector(1)+KEVector(2)+KEVector(3);

% Vibration Loads ?

% Thermal Cycling Loads ?

% Tipping ?

end

plot(accelMax/9.81,dt)

figure

plot(mainMemberLength,Pbuckle)

% Question for bowden: can we assume that the dynamic loads and static are

% decoupled? That the damping device will act as a point of failure and not

% buckle the legs from the dynamic loads?

totalF = weightTotalMoon+F_dynamic