class Rocket:
DEBUG_VERBOSITY = 2
def __init__(self):
# The order of initialisation here reflects the hierarchy we are using
# For now, all properties are hard-coded, rather than inputs
self.Tank = Tank()
self.Injector = Injector()
self.CombustionChamber = CombustionChamber()
self.Nozzle = Nozzle()
self.t = 0
#self.T_tank = 0
#self.rho_tank_liquid = 0
self.T_cc = 0
#self.T_post_comb = 0 #cp = combustion products
self.P_cc = 0 #cp = combustion products
self.m_dot_ox = 0
self.m_dot_fuel = 0
self.m_dot_choke = 0
def simulate(self, dt=0.001, max_timesteps=1e6):
# Simulate until reach zero oxidiser/fuel mass, not based on final time
loop_ctr = 0
thrust_curve = []
self.initiate()
while self.Tank.m_ox > 0 and self.CombustionChamber.inner_radius < self.CombustionChamber.outer_radius \
and loop_ctr < max_timesteps:
if self.DEBUG_VERBOSITY > 0:
print("t = ", dt * loop_ctr)
# converge is configured to return -1 in order to end simulation
tmp = self.converge()
if tmp == -1:
break
self.update(dt)
loop_ctr += 1
thrust_curve.append(self.Nozzle.thrust)
if self.Tank.m_ox < 1e-5:
print("[Rocket.Simulate] Tank has emptied of oxidiser")
elif self.CombustionChamber.outer_radius - self.CombustionChamber.inner_radius < 1e-5:
print("[Rocket.Simulate] Fuel grain has burned away")
elif loop_ctr > max_timesteps:
print(
"[Rocket.Simulate: ERROR, minor] Simulator has exceeded max timesteps without emptying"
)
return thrust_curve
def initiate(self):
# Calculate m_dot_ox when ignition occurs
# Eventually we could change this to simulate the startup transient
# This assumes combustion is already occurring at steady state and
# that m_dot_ox is determined by the choke
self.m_dot_ox = self.Nozzle.get_mass_flow_rate(
self.CombustionChamber.pressure,
self.CombustionChamber.temperature)
#self.T_tank = self.Tank.T_tank
#self.rho_tank_liquid = self.Tank.rho_liquid
self.T_cc = self.CombustionChamber.temperature
#self.T_post_comb = 0
self.P_cc = 0
def update(self, dt):
self.Tank.update(dt, self.m_dot_ox) # change m_ox
# Tank.update is configured to set rho = -1 in certain cases to end simulation
if self.Tank.rho_liquid == -1:
return
#self.Injector.update(dt) # should do NOTHING
self.CombustionChamber.update(
dt, self.m_dot_fuel) # change m_fuel & r_fuel
#self.Nozzle.update(dt) # should do NOTHING
def converge(self):
#The second MAJOR function. After everything that depends EXPLICITLY on time
# has changed, call this function to "equilibrate" the various components. This should
# be done after every timestep
epsilon = 1000 # Percent change between steps
epsilon_min = 1e-3
converge_ctr = 0
while epsilon > epsilon_min:
# Does nothing
self.Tank.converge()
# Determine oxidiser mass flow rate based on the injector model
self.m_dot_ox = self.Injector.converge(self.Tank.T_tank, self.Tank.rho_liquid, \
self.CombustionChamber.temperature, self.CombustionChamber.pressure)
# Determine fuel mass flow rate based on CC model
self.m_dot_fuel = self.CombustionChamber.converge(
self.m_dot_ox, self.m_dot_fuel)
# Determine, based on CC conditions, the choked flow rate
# We require that this choked rate be equal to the total flow rate
m_dot_choke = self.Nozzle.converge(
self.CombustionChamber.temperature,
self.CombustionChamber.pressure)
epsilon = abs(self.m_dot_ox + self.m_dot_fuel - m_dot_choke)
converge_ctr += 1
if self.DEBUG_VERBOSITY > 1:
print("***DEBUG*** [Rocket.converge] Steps to convergence = ",
converge_ctr)
print("***DEBUG*** [Rocket.converge] Convergence epsilon = ",
epsilon)
