SolidMotor Class¶
Class to specify characteristics and useful operations for solid motors.

Geometrical attributes

Motor.
nozzleRadius
¶ Radius of motor nozzle outlet in meters.
 Type
float

Motor.
throatRadius
¶ Radius of motor nozzle throat in meters.
 Type
float

Motor.
grainNumber
¶ Number of solid grains.
 Type
int

Motor.
grainSeparation
¶ Distance between two grains in meters.
 Type
float

Motor.
grainDensity
¶ Density of each grain in kg/meters cubed.
 Type
float

Motor.
grainOuterRadius
¶ Outer radius of each grain in meters.
 Type
float

Motor.
grainInitialInnerRadius
¶ Initial inner radius of each grain in meters.
 Type
float

Motor.
grainInitialHeight
¶ Initial height of each grain in meters.
 Type
float

Motor.
grainInitialVolume
¶ Initial volume of each grain in meters cubed.
 Type
float

Mass and moment of inertia attributes

Motor.
grainInitialMass
¶ Initial mass of each grain in kg.
 Type
float

Motor.
propellantInitialMass
¶ Total propellant initial mass in kg.
 Type
float

Motor.
massDot
¶ Time derivative of propellant total mass in kg/s as a function of time.
 Type

Motor.
inertiaI
¶ Propellant moment of inertia in kg*meter^2 with respect to axis perpendicular to axis of cylindrical symmetry of each grain, given as a function of time.
 Type

Motor.
inertiaIDot
¶ Time derivative of inertiaI given in kg*meter^2/s as a function of time.
 Type

Motor.
inertiaZ
¶ Propellant moment of inertia in kg*meter^2 with respect to axis of cylindrical symmetry of each grain, given as a function of time.
 Type

Motor.
inertiaDot
¶ Time derivative of inertiaZ given in kg*meter^2/s as a function of time.
 Type

Thrust and burn attributes

Motor.
totalImpulse
¶ Total impulse of the thrust curve in N*s.
 Type
float

Motor.
maxThrust
¶ Maximum thrust value of the given thrust curve, in N.
 Type
float

Motor.
maxThrustTime
¶ Time, in seconds, in which the maximum thrust value is achieved.
 Type
float

Motor.
averageThrust
¶ Average thrust of the motor, given in N.
 Type
float

Motor.
burnOutTime
¶ Total motor burn out time, in seconds. Must include delay time when the motor takes time to ignite. Also seen as time to end thrust curve.
 Type
float

Motor.
exhaustVelocity
¶ Propulsion gases exhaust velocity, assumed constant, in m/s.
 Type
float

Motor.
burnArea
¶ Total burn area considering all grains, made out of inner cylindrical burn area and grain top and bottom faces. Expressed in meters squared as a function of time.
 Type

Motor.
Kn
¶ Motor Kn as a function of time. Defined as burnArea divided by nozzle throat cross sectional area. Has no units.
 Type

Motor.
interpolate
¶ Method of interpolation used in case thrust curve is given by data set in .csv or .eng, or as an array. Options are ‘spline’ ‘akima’ and ‘linear’. Default is “linear”.
 Type
string

rocketpy.SolidMotor.
exhaustVelocity
¶ Calculates and returns exhaust velocity by assuming it as a constant. The formula used is total impulse/propellant initial mass. The value is also stored in self.exhaustVelocity.
 Parameters
None –
 Returns
self.exhaustVelocity – Constant gas exhaust velocity of the motor.
 Return type
float