Change in velocity equation with explicit method
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BioZ
am 29 Mär. 2020
Beantwortet: Ameer Hamza
am 29 Mär. 2020
Hello Everyone, I am new to MatLab, and looking for some help.
I have a code where I have 3600 time steps.
I am calculating change in mass of a rocket every step which is assumed to be constant (5000kg/s)
with this bit of a code
for n=2:length(t)
if M(n-1) >= mass_r;
M(n)=M(n-1)-dm*dt;
else
M(n)=mass_r-1;
end
end
I would like someone to help me to implement this equation in MatLab form
I tried using an explicit method but alot of errors just rainfalls on me.
Would appreciate any help.
2 Kommentare
darova
am 29 Mär. 2020
Can you explain more? You have constant. What are you trying to calculate? What is V?
Akzeptierte Antwort
Ameer Hamza
am 29 Mär. 2020
See this solution by using ode45
[t, V] = ode45(@dV, [0 300], 0);
plot(t,V)
function dVdt = dV(t, V)
G = 6.67408e-11;
M = 5.9722e24;
R = 6371e3;
A = 75;
Cd = 0.4;
me = 54000;
mo = 894000;
ve = 4500;
dmdt = 5000;
m_fuel = mo - me;
time_fuel = m_fuel/dmdt;
if t < time_fuel
m = mo - t*dmdt;
else
m = me;
end
dVdt = 1/m*(ve*dmdt - G*M*m/R^2 - 0.5*Cd*A*V^2);
end
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darova
am 29 Mär. 2020
Here is what i think about this question
for n = 2:length(t)
if m(n-1) > me % if rocket has fuel
dm = 5000;
else
dm = 0; % no fuel, mass change=0
end
dV = (ve*dm - ...)/m % longformula for acceleration
m(n) = m(n) - dm*dt; % mass change
V(n) = V(n-1) + dV*dt;
end
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