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% hybrid motor calculations by Glen E. Gardner Jr.
% glen.gardner@verizon.net


% Adjust these numbers for the motor you desire.

% specific impulse in seconds
specific_impulse=220

specific_impulse =

   220


% gravitational constant in m/s^2
gravity=9.80665

gravity =

                   9.80665


% average thrust (one second)in Newtons
average_thrust=60

average_thrust =

    60


% tank pressure (megapascals)
tank_pressure=5.136775

tank_pressure =

                  5.136775


% burn time (seconds)
burn_time=5

burn_time =

     5


% discharge coefficient (unitless, injector nozzle efficiency)
discharge_coefficient=0.80

discharge_coefficient =

                       0.8


% mass fraction of oxidizer (unitless)
oxidizer_fraction=0.87

oxidizer_fraction =

                      0.87


% mass fraction of the fuel (unitless)
fuel_fraction=0.13

fuel_fraction =

                      0.13


% oxidizer specific gravity for liquid nitrous oxide(unitless)
oxidizer_specific_gravity=1.530

oxidizer_specific_gravity =

                      1.53


% fuel specific gravity for solid HDPE polyethelyne(unitless)
fuel_specific_gravity=0.918

fuel_specific_gravity =

                     0.918


% fuel regression rate (meters per second)
fuel_regression_rate=0.001

fuel_regression_rate =

                     0.001


% outside diameter of fuel grain (meters)
fuel_grain_od=0.036

fuel_grain_od =

                     0.036



% nozzle stuff

% thrust coefficient (unitless)
thrust_coefficient=1.425

thrust_coefficient =

                     1.425


% expansion ratio (unitless)
expansion_ratio=4

expansion_ratio =

     4


% nozzle outlet half angle (in degrees)
half_angle=15

half_angle =

    15


half_angle=((2*pi)/360)*half_angle

half_angle =

         0.261799387799149



% the calculations begin here (don't thouch these numbers)


% inside diameter of the fuel grain (meters)
fuel_grain_id=fuel_grain_od-(2*burn_time*(fuel_regression_rate))

fuel_grain_id =

                     0.026


% inside diameter of oxidizer tank (meters)
oxidizer_tank_id=fuel_grain_od

oxidizer_tank_id =

                     0.036


% combustion chamber pressure (megapascals)
chamber_pressure=tank_pressure/2

chamber_pressure =

                 2.5683875


% nozzle throat area (millimeters)
throat_area=average_thrust/(thrust_coefficient*chamber_pressure)

throat_area =

          16.3936567818893


throat_diameter=2*sqrt(throat_area/pi)

throat_diameter =

          4.56870354668775


% exhaust nozzle exit area (square millimeters)
exit_area=expansion_ratio*throat_area

exit_area =

          65.5746271275573


% exhaust nozzle exit diameter (millimeters)
exit_diameter=2*sqrt(exit_area/pi)

exit_diameter =

          9.13740709337551


% exhaust nozzle skirt length (millimeters)
skirt_length=(((exit_diameter/2)-(throat_diameter/2))/sin(half_angle))*cos(half_angle)

skirt_length =

          8.52531688047941


% mass flow rate (kilograms per second)
mass_flow=average_thrust/(specific_impulse * gravity)

mass_flow =

        0.0278104421721253


% total mass flow (kilograms)
total_mass_flow=mass_flow*burn_time

total_mass_flow =

         0.139052210860627


% oxidizer mass flow rate (kilograms/second)
oxidizer_mass_flow=oxidizer_fraction*mass_flow

oxidizer_mass_flow =

         0.024195084689749


% fuel mass flow rate(kilograms/second)
fuel_mass_flow=fuel_fraction*mass_flow

fuel_mass_flow =

       0.00361535748237629


% total oxidizer mass flow (kilograms) 
total_oxidizer_mass_flow=total_mass_flow*oxidizer_fraction

total_oxidizer_mass_flow =

         0.120975423448745


% total fuel mass flow (kilograms)
total_fuel_mass_flow=total_mass_flow*fuel_fraction

total_fuel_mass_flow =

        0.0180767874118815


% combustion port cross-sectional-area (square meters)
combustion_port_area=pi*((fuel_grain_id/2)^2)

combustion_port_area =

      0.000530929158456675


% oxidizer flow volume (cubic meters per second)
oxidizer_flow_volume=oxidizer_mass_flow/oxidizer_specific_gravity

oxidizer_flow_volume =

        0.0158137808429732


% oxidizer velocity inside the combustion chamber (meters per second)
oxidizer_mass_velocity=oxidizer_flow_volume/combustion_port_area

oxidizer_mass_velocity =

          29.7851052086522


% oxidizer fuel injector port cross-sectional area (square millimeters)
injector_port_area=(oxidizer_mass_flow/discharge_coefficient)/sqrt(2*oxidizer_specific_gravity * (tank_pressure-chamber_pressure))

injector_port_area =

        0.0107881300345024


% oxidizer port diameter (millimeters)
injector_port_diameter=2*sqrt(injector_port_area/pi)

injector_port_diameter =

         0.117200144085549


% mass velocity inside combustion port (meters per second)
mass_velocity=mass_flow/combustion_port_area

mass_velocity =

          52.3807022634917


% total fuel volume (liters)
total_fuel_volume=total_fuel_mass_flow/fuel_specific_gravity

total_fuel_volume =

        0.0196914895554264


% total oxidizer volume (liters)
total_oxidizer_volume=total_oxidizer_mass_flow/oxidizer_specific_gravity

total_oxidizer_volume =

        0.0790689042148661


% fuel grain length (millimeters)
fuel_grain_length=total_fuel_volume/((pi/4)*(fuel_grain_od^2-fuel_grain_id^2))

fuel_grain_length =

           40.438682575336


% oxidizer tank length (millimeters)
oxidizer_tank_length=total_oxidizer_volume/(pi*((oxidizer_tank_id/2)^2))

oxidizer_tank_length =

          77.6802898188613


% conversions for component choices

% injector flow rate in gallons per minute.
injector_flow_rate=oxidizer_mass_flow*oxidizer_specific_gravity*0.2642*60

injector_flow_rate =

         0.586816938227909


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