KRPC Code

text.py

import time
import math
import krpc

conn = krpc.connect(name='Hello World')
vessel = conn.space_center.active_vessel

#CONSTANTS
TARGET_APO = 120000


#Streams
ut = conn.add_stream(getattr, conn.space_center, 'ut')
altitude = conn.add_stream(getattr, vessel.flight(), 'mean_altitude')
apoapsis = conn.add_stream(getattr, vessel.orbit, 'apoapsis_altitude')
periapsis = conn.add_stream(getattr, vessel.orbit, 'periapsis_altitude')
curr_thrust = conn.add_stream(getattr, vessel, 'thrust')
curr_mass = conn.add_stream(getattr, vessel, 'mass')

#Expressions
srb_resources = vessel.resources_in_decouple_stage(stage=4, cumulative=False)
srb_fuel_amount = conn.get_call(srb_resources.amount, 'SolidFuel')

stage_1_resources = vessel.resources_in_decouple_stage(stage=3, cumulative=False)
lf_fuel_amount = conn.get_call(stage_1_resources.amount, 'LiquidFuel')

expr1 = conn.krpc.Expression.less_than(
    conn.krpc.Expression.call(srb_fuel_amount),
    conn.krpc.Expression.constant_float(0.1))

expr2 = conn.krpc.Expression.less_than(
    conn.krpc.Expression.call(lf_fuel_amount),
    conn.krpc.Expression.constant_float(0.1))

#Events
srb_low_fuel = conn.krpc.add_event(expr1)
lf_low_fuel = conn.krpc.add_event(expr2)

#Functions
def sep_srbs():
    vessel.control.activate_next_stage()
    print('SRB Booster Separation!')
    srb_low_fuel.remove()

def stage_booster():
    vessel.control.activate_next_stage()
    print('Stage 1 Booster Separation!')
    lf_low_fuel.remove()

def calc_gravity(m1, m2, radius):
    G = 6.67e-11
    return (G*(m1+m2))/(radius**2)

def get_twr(mass, thrust, gravity):
    weight = mass * gravity
    return thrust / weight

def twr_control(curr_twr, min, max):
    prop = 1
    if curr_twr > max:
        amt = (curr_twr - max)
        vessel.control.throttle -= prop * amt
    if curr_twr < min:
        amt = (min - curr_twr)
        vessel.control.throttle += prop * amt

def gravity_turn(alt):
    if alt <= 70000:
        return -10.8**-8*(alt**2)-(0.00091*alt)+90
    else:
        return 0

def calc_circ_dv():
    #calc velocity at target apo for perfect circle
    m_u = vessel.orbit.body.gravitational_parameter
    body_r = vessel.orbit.body.equatorial_radius
    target_vel = math.sqrt(m_u/(body_r+apoapsis()))
    #calc velocity at target apo for current vessel
    vessel_vel = math.sqrt(m_u*((2/(body_r+apoapsis()))-(1/vessel.orbit.semi_major_axis)))
    #take difference
    return target_vel - vessel_vel

def calc_burn_time(burn_dv):
    #Tsiolkovsky rocket equation to get end mass
    isp = vessel.specific_impulse_at(0)
    gravity = conn.space_center.bodies['Kerbin'].surface_gravity
    mass_start = vessel.mass
    thrust = vessel.available_thrust_at(0)
    mass_end = mass_start/math.e**(burn_dv/(isp*gravity))
    #calc avg acceleration
    avg_accel = ((thrust/mass_start)+(thrust/mass_end))/2
    #calc burn time
    return burn_dv / avg_accel


#Callbacks
srb_low_fuel.add_callback(sep_srbs)
srb_low_fuel.start()

lf_low_fuel.add_callback(stage_booster)
lf_low_fuel.start()

#1-Prelaunch
print(f'Preparing for launch of {vessel.name}...')
vessel.control.throttle = 1.0
time.sleep(.1)
print(f'Throttle set to: {vessel.control.throttle*100}%')
print(f'Ready for Launch!')
vessel.auto_pilot.engage()
vessel.auto_pilot.target_heading = 90
vessel.auto_pilot.target_pitch = 90
vessel.auto_pilot.target_roll = 0
time.sleep(1)

#Countdown
print(f'Countdown Started')
time.sleep(1)
print(f'3...')
time.sleep(1)
print(f'2...')
time.sleep(1)
print(f'1...')
time.sleep(1)

#2-Liftoff
vessel.control.activate_next_stage()
print(f'Liftoff!')

#3-Gravity Turn
while TARGET_APO - 1000 > apoapsis():
    curr_gravity = calc_gravity(curr_mass(), vessel.orbit.body.mass, vessel.orbit.radius)
    curr_twr = get_twr(curr_mass(), curr_thrust(), curr_gravity)
    twr_control(curr_twr, 1.4, 1.6)
    # print(f'Current TWR: {curr_twr}')
    target_pitch = gravity_turn(altitude())
    vessel.auto_pilot.target_pitch = target_pitch
    # print(f'Target pitch: {target_pitch}')
    time.sleep(.05)
vessel.control.throttle = 0.05
while TARGET_APO >= apoapsis():
    time.sleep(.02)
print(f'Target APO Reached')
vessel.control.throttle = 0

#4-Circ Burn
TARGET_THRUST = .3
circ_dv = calc_circ_dv()
print(f'Circ Dv = {circ_dv:.2f}')
burn_time = calc_burn_time(circ_dv)
mod_burn_time = burn_time / TARGET_THRUST
half_burn_time = burn_time / 2

conn.space_center.warp_to(ut()+vessel.orbit.time_to_apoapsis-half_burn_time-15, 50)

while vessel.orbit.time_to_apoapsis > half_burn_time:
    time.sleep(.05)

vessel.control.throttle = TARGET_THRUST

m_u = vessel.orbit.body.gravitational_parameter
body_r = vessel.orbit.body.equatorial_radius
target_vel = math.sqrt(m_u/(body_r+apoapsis()))

while vessel.orbit.speed < target_vel - 2:
    time.sleep(.05)

vessel.control.throttle = .05

while vessel.orbit.speed < target_vel:
    time.sleep(.02)

vessel.control.throttle = 0
print(f'Circularized')