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enviroment.py
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enviroment.py
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from enum import Enum
from math import sqrt, pi, cos, fabs, exp, log
from constants import SOLAR_MASS_IN_GRAMS, SUN_MASS_IN_EARTH_MASSES
from math import inf as INCREDIBLY_LARGE_NUMBER
# Universal constants
from constants import GRAV_CONSTANT
from constants import MOLAR_GAS_CONST
# Import conversion factors
from constants import CM_PER_KM, CM_PER_METER, SECONDS_PER_HOUR, DAYS_IN_A_YEAR, RADIANS_PER_ROTATION, MILLIBARS_PER_BAR
# Import Earth related constants.
from constants import EARTH_RADIUS, EARTH_DENSITY, EARTH_MASS_IN_GRAMS, EARTH_AXIAL_TILT, EARTH_AVERAGE_KELVIN, EARTH_CONVECTION_FACTOR, EARTH_SURF_PRES_IN_MILLIBARS, EARTH_ACCELERATION, EARTH_EFFECTIVE_TEMP, EARTH_WATER_MASS_PER_AREA, KM_EARTH_RADIUS, CHANGE_IN_EARTH_ANG_VEL
# Atmospheric Chemistry stuff
from constants import CLOUD_COVERAGE_FACTOR, GAS_RETENTION_THRESHOLD
from constants import FREEZING_POINT_OF_WATER
from constants import AN_O
from constants import MOL_HYDROGEN, MOL_NITROGEN, ATOMIC_NITROGEN
from constants import WATER_VAPOR
from constants import MIN_O2_IPP, MAX_O2_IPP, H20_ASSUMED_PRESSURE
from constants import EARTH_ALBEDO, ICE_ALBEDO, CLOUD_ALBEDO, AIRLESS_ICE_ALBEDO, GREENHOUSE_TRIGGER_ALBEDO, ROCKY_ALBEDO, ROCKY_AIRLESS_ALBEDO, WATER_ALBEDO
# Tunable constants?
from constants import J
from tabulate import tabulate
from util import pow1_4, pow2, pow3, about
# TODO(woursler): Break this file up.
# TODO(woursler): This whole file desperately needs natu.
VERBOSE = True
class BreathabilityPhrase(Enum):
NONE = 0
BREATHABLE = 1
UNBREATHABLE = 2
POISONOUS = 3
class PlanetType(Enum):
UNKNOWN = 0
ROCK = 1
VENUSIAN = 2
TERRESTRIAL = 3
SUB_SUB_GAS_GIANT = 4
SUB_GAS_GIANT = 5
GAS_GIANT = 6
MARTIAN = 7
WATER = 8
ICE = 9
ASTERIODS = 10
# TODO(woursler): Don't know what this means... maybe tidally locked?
ONE_FACE = 11
class Zone(Enum): # TODO(woursler): Figure it out. Might be related to habitable zone?
ZONE_1 = 1
ZONE_2 = 2
ZONE_3 = 3
def orb_zone(luminosity, orb_radius):
'''The orbital 'zone' of the particle.'''
if orb_radius < (4.0 * sqrt(luminosity)):
return Zone.ZONE_1
elif orb_radius < (15.0 * sqrt(luminosity)):
return Zone.ZONE_2
else:
return Zone.ZONE_3
def volume_radius(mass, density):
'''The mass is in units of solar masses, the density is in units
of grams/cc. The radius returned is in units of km.'''
mass = mass * SOLAR_MASS_IN_GRAMS
volume = mass / density
radius_in_cm = ((3.0 * volume) / (4.0 * pi)) ** (1.0 / 3.0)
return radius_in_cm / CM_PER_KM
# These constants are specific to kothari_radius.
# All units are in cgs system, ie: cm, g, dynes, etc.
A1_20 = 6.485E12
A2_20 = 4.0032E-8
BETA_20 = 5.71E12
JIMS_FUDGE = 1.004
def kothari_radius(mass, giant, zone):
'''Returns the radius of the planet in kilometers.
The mass passed in is in units of solar masses.
This formula is listed as eq.9 in Fogg's article, some typos
crop up in that eq. See "The Internal Constitution of Planets", by
Dr. D. S. Kothari, Mon. Not. of the Royal Astronomical Society, 96
pp.833-843, for the derivation. Specifically, is Kothari's
eq.23, appears on page 840.'''
if zone == Zone.ZONE_1:
if giant:
atomic_weight = 9.5
atomic_num = 4.5
else:
atomic_weight = 15.0
atomic_num = 8.0
else:
if zone == Zone.ZONE_2:
if giant:
atomic_weight = 2.47
atomic_num = 2.0
else:
atomic_weight = 10.0
atomic_num = 5.0
else:
if giant:
atomic_weight = 7.0
atomic_num = 4.0
else:
atomic_weight = 10.0
atomic_num = 5.0
temp1 = atomic_weight * atomic_num
temp = (2.0 * BETA_20 * (SOLAR_MASS_IN_GRAMS ** (1.0 / 3.0))) / \
(A1_20 * (temp1 ** (1.0 / 3.0)))
temp2 = A2_20 * (atomic_weight ** (4.0 / 3.0)) * \
(SOLAR_MASS_IN_GRAMS ** (2.0 / 3.0))
temp2 = temp2 * (mass ** (2.0 / 3.0))
temp2 = temp2 / (A1_20 * (atomic_num ** 2))
temp2 = 1.0 + temp2
temp = temp / temp2
temp = (temp * (mass ** (1.0 / 3.0))) / CM_PER_KM
temp = temp / JIMS_FUDGE
return(temp)
def empirical_density(mass, orb_radius, r_ecosphere, gas_giant):
'''The mass passed in is in units of solar masses, the orbital radius
is in units of AU. The density is returned in units of grams/cc.'''
temp = (mass * SUN_MASS_IN_EARTH_MASSES) ** (1.0 / 8.0)
temp = temp * (r_ecosphere / orb_radius) ** (1.0 / 4.0)
if gas_giant:
return(temp * 1.2)
else:
return(temp * 5.5)
def volume_density(mass, equat_radius):
'''The mass passed in is in units of solar masses, the equatorial
radius is in km. The density is returned in units of grams/cc.'''
mass = mass * SOLAR_MASS_IN_GRAMS
equat_radius = equat_radius * CM_PER_KM
volume = (4.0 * pi * (equat_radius ** 3)) / 3.0
return(mass / volume)
def period(separation, small_mass, large_mass):
'''The separation is in units of AU, both masses are in units of solar
masses. The period returned is in terms of Earth days.'''
period_in_years = sqrt((separation ** 3) / (small_mass + large_mass))
return(period_in_years * DAYS_IN_A_YEAR)
def day_length(planet):
'''Fogg's information for this routine came from Dole "Habitable Planets
for Man", Publishing Company, NY, 1964. From this, he came
up with his eq.12, is the equation for the 'base_angular_velocity'
below. He then used an equation for the change in angular velocity per
time (dw/dt) from P. Goldreich and S. Soter's paper "Q in the Solar
System" in Icarus, 5, pp.375-389 (1966). Using as a comparison the
change in angular velocity for the Earth, has come up with an
approximation for our planet (his eq.13) and take that into account.
This is used to find 'change_in_angular_velocity' below.
Input parameters are mass (in solar masses), radius (in Km), orbital
period (in days), radius (in AU), density (in g/cc),
eccentricity, whether it is a gas giant or not.
The length of the day is returned in units of hours.'''
planetary_mass_in_grams = planet.mass * SOLAR_MASS_IN_GRAMS
equatorial_radius_in_cm = planet.radius * CM_PER_KM
year_in_hours = planet.orb_period * 24.0
giant = (planet.type == PlanetType.GAS_GIANT or
planet.type == PlanetType.SUB_GAS_GIANT or
planet.type == PlanetType.SUB_SUB_GAS_GIANT)
stopped = False
planet.resonant_period = False # Warning: Modifies the planet
if giant:
k2 = 0.24
else:
k2 = 0.33
base_angular_velocity = sqrt(2.0 * J * (planetary_mass_in_grams) /
(k2 * (equatorial_radius_in_cm ** 2)))
# This next calculation determines how much the planet's rotation is
# slowed by the presence of the star.
change_in_angular_velocity = CHANGE_IN_EARTH_ANG_VEL * (planet.density / EARTH_DENSITY) * (equatorial_radius_in_cm / EARTH_RADIUS) * (
EARTH_MASS_IN_GRAMS / planetary_mass_in_grams) * (planet.sun.mass_ratio ** 2.0) * (1.0 / (planet.orbit.a ** 6.0))
ang_velocity = base_angular_velocity + \
(change_in_angular_velocity * planet.sun.age)
# Now we change from rad/sec to hours/rotation.
if ang_velocity <= 0.0:
stopped = True
day_in_hours = INCREDIBLY_LARGE_NUMBER
else:
day_in_hours = RADIANS_PER_ROTATION / (SECONDS_PER_HOUR * ang_velocity)
if (day_in_hours >= year_in_hours) or stopped:
if planet.orbit.e > 0.1:
spin_resonance_factor = (1.0 - planet.orbit.e) / (1.0 + planet.orbit.e)
planet.resonant_period = True
return(spin_resonance_factor * year_in_hours)
else:
return(year_in_hours)
return(day_in_hours)
def inclination(orb_radius):
'''The orbital radius is expected in units of Astronomical Units (AU).
Inclination is returned in units of degrees. '''
temp = int((orb_radius ** 0.2) * about(EARTH_AXIAL_TILT, 0.4))
return temp % 360
def escape_vel(mass, radius):
'''This function implements the escape velocity calculation. Note that
it appears that Fogg's eq.15 is incorrect.
The mass is in units of solar mass, radius in kilometers, the
velocity returned is in cm/sec. '''
mass_in_grams = mass * SOLAR_MASS_IN_GRAMS
radius_in_cm = radius * CM_PER_KM
return sqrt(2.0 * GRAV_CONSTANT * mass_in_grams / radius_in_cm)
def rms_vel(molecular_weight, exospheric_temp):
'''This is Fogg's eq.16. The molecular weight (usually assumed to be N2)
is used as the basis of the Root Mean Square (RMS) velocity of the
molecule or atom. The velocity returned is in cm/sec.
Orbital radius is in A.U.(ie: in units of the earth's orbital radius).'''
return sqrt((3.0 * MOLAR_GAS_CONST * exospheric_temp) / molecular_weight) * CM_PER_METER
def molecule_limit(mass, equat_radius, exospheric_temp):
'''This function returns the smallest molecular weight retained by the
body, is useful for determining the atmosphere composition.
Mass is in units of solar masses, equatorial radius is in units of
kilometers. '''
esc_velocity = escape_vel(mass, equat_radius)
return ((3.0 * MOLAR_GAS_CONST * exospheric_temp) /
(pow2((esc_velocity / GAS_RETENTION_THRESHOLD) / CM_PER_METER)))
def acceleration(mass, radius):
'''This function calculates the surface acceleration of a planet. The
mass is in units of solar masses, radius in terms of km, the
acceleration is returned in units of cm/sec2. '''
return GRAV_CONSTANT * (mass * SOLAR_MASS_IN_GRAMS) / pow2(radius * CM_PER_KM)
def gravity(acceleration):
'''This function calculates the surface gravity of a planet. The
acceleration is in units of cm/sec2, the gravity is returned in
units of Earth gravities. '''
return acceleration / EARTH_ACCELERATION
def vol_inventory(mass, escape_vel, rms_vel, stellar_mass, zone, greenhouse_effect, accreted_gas):
'''This implements Fogg's eq.17. The 'inventory' returned is unitless.'''
velocity_ratio = escape_vel / rms_vel
if velocity_ratio >= GAS_RETENTION_THRESHOLD:
if zone == Zone.ZONE_1:
proportion_ = 140000.0
'''100 . 140 JLB'''
elif zone == Zone.ZONE_2:
proportion_ = 75000.0
elif zone == Zone.ZONE_3:
proportion_ = 250.0
else:
raise NotImplementedError("orbital zone not initialized correctly")
earth_units = mass * SUN_MASS_IN_EARTH_MASSES
temp1 = (proportion_ * earth_units) / stellar_mass
temp2 = about(temp1, 0.2)
temp2 = temp1
if greenhouse_effect or accreted_gas:
return temp2
else:
return temp2 / 140.0 # 100 . 140 JLB
else:
return 0.0
def pressure(volatile_gas_inventory, equat_radius, gravity):
'''This implements Fogg's eq.18. The pressure returned is in units of
millibars (mb). The gravity is in units of Earth gravities, radius
in units of kilometers.
JLB: Aparently this assumed that pressure = 1000mb. I've added a
fudge factor (EARTH_SURF_PRES_IN_MILLIBARS / 1000.) to correct for that'''
equat_radius = KM_EARTH_RADIUS / equat_radius
return volatile_gas_inventory * gravity * (EARTH_SURF_PRES_IN_MILLIBARS / 1000.) / (equat_radius ** 2)
def boiling_point(surf_pressure):
'''This function returns the boiling point of water in an atmosphere of
pressure 'surf_pressure', in millibars. The boiling point is
returned in units of Kelvin. This is Fogg's eq.21. '''
surface_pressure_in_bars = surf_pressure / MILLIBARS_PER_BAR
return 1.0 / ((log(surface_pressure_in_bars) / -5050.5) + (1.0 / 373.0))
def hydro_fraction(volatile_gas_inventory, planet_radius):
'''This function is Fogg's eq.22. Given the volatile gas inventory and
planetary radius of a planet (in Km), function returns the
fraction of the planet covered with water.
I have changed the function very slightly: the fraction of Earth's
surface covered by water is 71%, not 75% as Fogg used. '''
temp = (0.71 * volatile_gas_inventory / 1000.0) * \
((KM_EARTH_RADIUS / planet_radius) ** 2)
if temp >= 1.0:
return 1.0
else:
return temp
# Constant only used here and not really explained.
Q2_36 = 0.0698 # 1/Kelvin
def cloud_fraction(surf_temp, smallest_MW_retained, equat_radius, hydro_fraction):
'''Given the surface temperature of a planet (in Kelvin), function
returns the fraction of cloud cover available. This is Fogg's eq.23.
See Hart in "Icarus" (vol 33, pp23 - 39, 1978) for an explanation.
This equation is Hart's eq.3.
I have modified it slightly using constants and relationships from
Glass's book "Introduction to Planetary Geology", p.46.
The 'CLOUD_COVERAGE_FACTOR' is the amount of surface area on Earth
covered by one Kg. of cloud.'''
if smallest_MW_retained > WATER_VAPOR:
return 0.0
else:
surf_area = 4.0 * pi * (equat_radius ** 2)
hydro_mass = hydro_fraction * surf_area * EARTH_WATER_MASS_PER_AREA
water_vapor_in_kg = (0.00000001 * hydro_mass) * \
exp(Q2_36 * (surf_temp - EARTH_AVERAGE_KELVIN))
fraction = CLOUD_COVERAGE_FACTOR * water_vapor_in_kg / surf_area
if fraction >= 1.0:
return 1.0
else:
return fraction
def ice_fraction(hydro_fraction, surf_temp):
'''Given the surface temperature of a planet (in Kelvin), function
returns the fraction of the planet's surface covered by ice. This is
Fogg's eq.24. See Hart[24] in Icarus vol.33, p.28 for an explanation.
I have changed a constant from 70 to 90 in order to bring it more in
line with the fraction of the Earth's surface covered with ice, which
is approximatly .016 (=1.6%). '''
if (surf_temp > 328.0):
surf_temp = 328.0
temp = ((328.0 - surf_temp) / 90.0) ** 5.0
if temp > (1.5 * hydro_fraction):
temp = (1.5 * hydro_fraction)
if temp >= 1.0:
return 1.0
else:
return temp
def eff_temp(ecosphere_radius, orb_radius, albedo):
'''This is Fogg's eq.19. The ecosphere radius is given in AU, orbital
radius in AU, the temperature returned is in Kelvin.'''
return sqrt(ecosphere_radius / orb_radius) * pow1_4((1.0 - albedo) / (1.0 - EARTH_ALBEDO)) * EARTH_EFFECTIVE_TEMP
def est_temp(ecosphere_radius, orb_radius, albedo):
return sqrt(ecosphere_radius / orb_radius) * pow1_4((1.0 - albedo) / (1.0 - EARTH_ALBEDO)) * EARTH_AVERAGE_KELVIN
def grnhouse(r_ecosphere, orb_radius):
'''Old grnhouse:
Note that if the orbital radius of the planet is greater than or equal
to R_inner, 99% of it's volatiles are assumed to have been deposited in
surface reservoirs (otherwise, suffers from the greenhouse effect).
if ((orb_radius < r_greenhouse) and (zone == 1))
The definition is based on the inital surface temperature and what
state water is in. If it's too hot, water will never condense out
of the atmosphere, down and form an ocean. The albedo used here
was chosen so that the boundary is about the same as the old method
Neither zone, r_greenhouse are used in this version JLB'''
temp = eff_temp(r_ecosphere, orb_radius, GREENHOUSE_TRIGGER_ALBEDO)
return temp > FREEZING_POINT_OF_WATER
def green_rise(optical_depth, effective_temp, surf_pressure):
'''This is Fogg's eq.20, is also Hart's eq.20 in his "Evolution of
Earth's Atmosphere" article. The effective temperature given is in
units of Kelvin, is the rise in temperature produced by the
greenhouse effect, is returned.
I tuned this by changing a pow(x,.25) to pow(x,.4) to match Venus - JLB'''
convection_factor = EARTH_CONVECTION_FACTOR * \
pow(surf_pressure / EARTH_SURF_PRES_IN_MILLIBARS, 0.4)
rise = (pow1_4(1.0 + 0.75 * optical_depth) - 1.0) * \
effective_temp * convection_factor
if (rise < 0.0):
rise = 0.0
return rise
def planet_albedo(water_fraction, cloud_fraction, ice_fraction, surf_pressure):
'''The surface temperature passed in is in units of Kelvin.
The cloud adjustment is the fraction of cloud cover obscuring each
of the three major components of albedo that lie below the clouds.'''
rock_fraction = 1.0 - water_fraction - ice_fraction
components = 0.0
if water_fraction > 0.0:
components = components + 1.0
if ice_fraction > 0.0:
components = components + 1.0
if rock_fraction > 0.0:
components = components + 1.0
cloud_adjustment = cloud_fraction / components
if rock_fraction >= cloud_adjustment:
rock_fraction = rock_fraction - cloud_adjustment
else:
rock_fraction = 0.0
if water_fraction > cloud_adjustment:
water_fraction = water_fraction - cloud_adjustment
else:
water_fraction = 0.0
if ice_fraction > cloud_adjustment:
ice_fraction = ice_fraction - cloud_adjustment
else:
ice_fraction = 0.0
cloud_part = cloud_fraction * CLOUD_ALBEDO # about(...,0.2)
if surf_pressure == 0.0:
rock_part = rock_fraction * ROCKY_AIRLESS_ALBEDO # about(...,0.3)
ice_part = ice_fraction * AIRLESS_ICE_ALBEDO # about(...,0.4)
water_part = 0
else:
rock_part = rock_fraction * ROCKY_ALBEDO # about(...,0.1)
water_part = water_fraction * WATER_ALBEDO # about(...,0.2)
ice_part = ice_fraction * ICE_ALBEDO # about(...,0.1)
return(cloud_part + rock_part + water_part + ice_part)
def opacity(molecular_weight, surf_pressure):
'''This function returns the dimensionless quantity of optical depth,
which is useful in determining the amount of greenhouse effect on a
planet.'''
optical_depth = 0.0
if (molecular_weight >= 0.0) and (molecular_weight < 10.0):
optical_depth = optical_depth + 3.0
if (molecular_weight >= 10.0) and (molecular_weight < 20.0):
optical_depth = optical_depth + 2.34
if (molecular_weight >= 20.0) and (molecular_weight < 30.0):
optical_depth = optical_depth + 1.0
if (molecular_weight >= 30.0) and (molecular_weight < 45.0):
optical_depth = optical_depth + 0.15
if (molecular_weight >= 45.0) and (molecular_weight < 100.0):
optical_depth = optical_depth + 0.05
if surf_pressure >= (70.0 * EARTH_SURF_PRES_IN_MILLIBARS):
optical_depth = optical_depth * 8.333
else:
if surf_pressure >= (50.0 * EARTH_SURF_PRES_IN_MILLIBARS):
optical_depth = optical_depth * 6.666
else:
if surf_pressure >= (30.0 * EARTH_SURF_PRES_IN_MILLIBARS):
optical_depth = optical_depth * 3.333
else:
if surf_pressure >= (10.0 * EARTH_SURF_PRES_IN_MILLIBARS):
optical_depth = optical_depth * 2.0
else:
if surf_pressure >= (5.0 * EARTH_SURF_PRES_IN_MILLIBARS):
optical_depth = optical_depth * 1.5
return(optical_depth)
def gas_life(molecular_weight, planet):
''' calculates the number of years it takes for 1/e of a gas to escape from a planet's atmosphere.
Taken from Dole p. 34. He cites Jeans (1916) & Jones (1923)'''
v = rms_vel(molecular_weight, planet.exospheric_temp)
g = planet.surf_grav * EARTH_ACCELERATION
r = (planet.radius * CM_PER_KM)
try:
t = (pow3(v) / (2.0 * pow2(g) * r)) * exp((3.0 * g * r) / pow2(v))
years = t / (SECONDS_PER_HOUR * 24.0 * DAYS_IN_A_YEAR)
if years > 2.0E10:
years = INCREDIBLY_LARGE_NUMBER
except OverflowError:
years = INCREDIBLY_LARGE_NUMBER
# long ve = planet.esc_velocity
# long k = 2
# long t2 = ((k * pow3(v) * r) / pow4(ve)) * exp((3.0 * pow2(ve)) / (2.0 * pow2(v)))
# long years2 = t2 / (SECONDS_PER_HOUR * 24.0 * DAYS_IN_A_YEAR)
# if VERBOSE:
# fprintf (stderr, "gas_life: %LGs, ratio: %Lf\n",
# years, ve / v)
return years
def min_molec_weight(planet):
'''TODO(woursler): Not sure this is ported well with the guesses and all. Also it's totally unreadable.'''
mass = planet.mass
radius = planet.radius
temp = planet.exospheric_temp
target = 5.0E9
guess_1 = molecule_limit(mass, radius, temp)
guess_2 = guess_1
life = gas_life(guess_1, planet)
loops = 0
if planet.sun:
target = planet.sun.age
if life > target:
while life > target and loops < 25:
guess_1 = guess_1 / 2.0
life = gas_life(guess_1, planet)
loops += 1
else:
while life < target and loops < 25:
guess_2 = guess_2 * 2.0
life = gas_life(guess_2, planet)
loops += 1
loops = 0
while (guess_2 - guess_1) > 0.1 and loops < 25:
guess_3 = (guess_1 + guess_2) / 2.0
life = gas_life(guess_3, planet)
if life < target:
guess_1 = guess_3
else:
guess_2 = guess_3
loops += 1
life = gas_life(guess_2, planet)
return guess_2
def calculate_surface_temp(planet, first, last_water, last_clouds, last_ice, last_temp, last_albedo):
'''The temperature calculated is in degrees Kelvin. '''
boil_off = False
if first:
planet.albedo = EARTH_ALBEDO
effective_temp = eff_temp(
planet.sun.r_ecosphere, planet.orbit.a, planet.albedo)
greenhouse_temp = green_rise(opacity(planet.molec_weight,
planet.surf_pressure),
effective_temp,
planet.surf_pressure)
planet.surf_temp = effective_temp + greenhouse_temp
set_temp_range(planet)
if planet.greenhouse_effect and planet.max_temp < planet.boil_point:
'''if VERBOSE:
fprintf(stderr, "Deluge: %s %d max (%Lf) < boil (%Lf)\n",
planet.sun.name,
planet.planet_no,
planet.max_temp,
planet.boil_point)'''
planet.greenhouse_effect = 0
planet.volatile_gas_inventory = vol_inventory(planet.mass,
planet.esc_velocity,
planet.rms_velocity,
planet.sun.mass_ratio,
planet.orbit_zone,
planet.greenhouse_effect,
(planet.gas_mass
/ planet.mass) > 0.000001)
planet.surf_pressure = pressure(planet.volatile_gas_inventory,
planet.radius,
planet.surf_grav)
planet.boil_point = boiling_point(planet.surf_pressure)
water_raw = planet.hydrosphere = hydro_fraction(planet.volatile_gas_inventory,
planet.radius)
clouds_raw = planet.cloud_cover = cloud_fraction(planet.surf_temp,
planet.molec_weight,
planet.radius,
planet.hydrosphere)
planet.ice_cover = ice_fraction(planet.hydrosphere,
planet.surf_temp)
if planet.greenhouse_effect and (planet.surf_pressure > 0.0):
planet.cloud_cover = 1.0
if (planet.high_temp >= planet.boil_point) and (not first) and (not int(planet.day) == int(planet.orb_period * 24.0)) or planet.resonant_period:
planet.hydrosphere = 0.0
boil_off = True
if planet.molec_weight > WATER_VAPOR:
planet.cloud_cover = 0.0
else:
planet.cloud_cover = 1.0
if planet.surf_temp < (FREEZING_POINT_OF_WATER - 3.0):
planet.hydrosphere = 0.0
planet.albedo = planet_albedo(planet.hydrosphere,
planet.cloud_cover,
planet.ice_cover,
planet.surf_pressure)
effective_temp = eff_temp(planet.sun.r_ecosphere, planet.orbit.a, planet.albedo)
greenhouse_temp = green_rise(opacity(planet.molec_weight,
planet.surf_pressure),
effective_temp,
planet.surf_pressure)
planet.surf_temp = effective_temp + greenhouse_temp
if not first:
if not boil_off:
planet.hydrosphere = (planet.hydrosphere + (last_water * 2)) / 3
planet.cloud_cover = (planet.cloud_cover + (last_clouds * 2)) / 3
planet.ice_cover = (planet.ice_cover + (last_ice * 2)) / 3
planet.albedo = (planet.albedo + (last_albedo * 2)) / 3
planet.surf_temp = (planet.surf_temp + (last_temp * 2)) / 3
set_temp_range(planet)
if VERBOSE:
print("calculate_surface_temp readout\n" + tabulate([
["AU", planet.orbit.a],
["Surface Temp C", planet.surf_temp - FREEZING_POINT_OF_WATER],
["Effective Temp C", effective_temp - FREEZING_POINT_OF_WATER],
["Greenhouse Temp", greenhouse_temp],
["Water Cover", planet.hydrosphere],
["water_raw", water_raw],
["Cloud Cover", planet.cloud_cover],
["clouds_raw", clouds_raw],
["Ice Cover", planet.ice_cover],
["Albedo", planet.albedo],
]))
def iterate_surface_temp(planet):
initial_temp = est_temp(planet.sun.r_ecosphere, planet.orbit.a, planet.albedo)
if VERBOSE:
print(tabulate([
["Initial temp", initial_temp],
["Solar Ecosphere", planet.sun.r_ecosphere],
["AU", planet.orbit.a],
["Albedo", planet.albedo],
]))
h2_life = gas_life(MOL_HYDROGEN, planet)
h2o_life = gas_life(WATER_VAPOR, planet)
n2_life = gas_life(MOL_NITROGEN, planet)
n_life = gas_life(ATOMIC_NITROGEN, planet)
print('Gas lifetimes:\n' + tabulate([
['H2', h2_life],
['H2O', h2o_life],
['N', n_life],
['N2', n2_life],
]))
calculate_surface_temp(planet, True, 0, 0, 0, 0, 0)
for _ in range(26): # TODO(woursler): WTF is this magic number? just an iteration limit? Should be a param.
last_water = planet.hydrosphere
last_clouds = planet.cloud_cover
last_ice = planet.ice_cover
last_temp = planet.surf_temp
last_albedo = planet.albedo
calculate_surface_temp(planet, False,
last_water, last_clouds, last_ice,
last_temp, last_albedo)
if fabs(planet.surf_temp - last_temp) < 0.25:
break
planet.greenhs_rise = planet.surf_temp - initial_temp
'''
if VERBOSE:
fprintf(stderr, "%d: %5.gh = %5.1Lf (%5.1Lf C) st - %5.1Lf it [%5.1Lf re %5.1Lf a %5.1Lf alb]\n",
planet.planet_no,
planet.greenhs_rise,
planet.surf_temp,
planet.surf_temp - FREEZING_POINT_OF_WATER,
initial_temp,
planet.sun.r_ecosphere, planet.a, planet.albedo
)
'''
# TODO(woursler): Move this into an atomosphere class.
def inspired_partial_pressure(surf_pressure, gas_pressure):
'''Inspired partial pressure, takes into account humidification of the
air in the nasal passage and throat This formula is on Dole's p. 14'''
pH2O = H20_ASSUMED_PRESSURE
fraction = gas_pressure / surf_pressure
return (surf_pressure - pH2O) * fraction
def breathability(planet):
'''This function uses figures on the maximum inspired partial pressures
of Oxygen, atmospheric and traces gases as laid out on pages 15,
16 and 18 of Dole's Habitable Planets for Man to derive breathability
of the planet's atmosphere. JLB'''
oxygen_ok = False
if planet.gases == 0:
return BreathabilityPhrase.NONE
for index in range(planet.gases):
gas_no = 0
ipp = inspired_partial_pressure(planet.surf_pressure,
planet.atmosphere[index].surf_pressure)
for n in range(len(planet.gases)):
if planet.gases[n].num == planet.atmosphere[index].num:
gas_no = n
if ipp > planet.gases[gas_no].max_ipp:
return BreathabilityPhrase.POISONOUS
if planet.atmosphere[index].num == AN_O:
oxygen_ok = ((ipp >= MIN_O2_IPP) and (ipp <= MAX_O2_IPP))
if oxygen_ok:
return BreathabilityPhrase.BREATHABLE
else:
return BreathabilityPhrase.UNBREATHABLE
def lim(x):
'''function for 'soft limiting' temperatures'''
return x / sqrt(sqrt(1 + x**4))
def soft(v, max, min):
dv = v - min
dm = max - min
return (lim(2*dv/dm-1)+1)/2 * dm + min
def set_temp_range(planet):
pressmod = 1 / sqrt(1 + 20 * planet.surf_pressure/1000.0)
ppmod = 1 / sqrt(10 + 5 * planet.surf_pressure/1000.0)
tiltmod = fabs(cos(planet.axial_tilt * pi/180) * pow(1 + planet.orbit.e, 2))
daymod = 1 / (200/planet.day + 1)
mh = pow(1 + daymod, pressmod)
ml = pow(1 - daymod, pressmod)
hi = mh * planet.surf_temp
lo = ml * planet.surf_temp
sh = hi + pow((100+hi) * tiltmod, sqrt(ppmod))
wl = lo - pow((150+lo) * tiltmod, sqrt(ppmod))
max = planet.surf_temp + sqrt(planet.surf_temp) * 10
min = planet.surf_temp / sqrt(planet.day + 24)
if lo < min:
lo = min
if wl < 0:
wl = 0
planet.high_temp = soft(hi, max, min)
planet.low_temp = soft(lo, max, min)
planet.max_temp = soft(sh, max, min)
planet.min_temp = soft(wl, max, min)