ggAstro Astronautics

ggame extensions for modeling spacecraft in planetary orbit

Rocket

class ggame.astro.Rocket(planet, **kwargs)

Rocket is a class for simulating the motion of a projectile through space, acted upon by arbitrary forces (thrust) and by gravitaitonal attraction to a single planetary object.

Initialize the Rocket object.

Example:

rocket1 = Rocket(earth, altitude=400000, velocity=7670, timezoom=2)

Required parameters:

• planet: Reference to a Planet object.

Optional keyword parameters are supported:

• bitmap: url of a suitable bitmap image for the rocket (png recommended) default is ggimages/rocket.png
• bitmapscale: scale factor for bitmap. Default is 0.1
• velocity: initial rocket speed. default is zero.
• directiond: initial rocket direction in degrees. Default is zero.
• direction: initial rocket direction in radians. Default is zero.
• tanomalyd: initial rocket true anomaly in degrees. Default is 90.
• tanomaly: initial rocket true anomaly in radians. Default is pi/2.
• altitude: initial rocket altitude in meters. Default is zero.
• showstatus: boolean displays flight parameters on screen. Default is True.
• statuspos: tuple with x,y coordinates of flight parameters. Default is upper left.
• statuslist: list of status names to include in flight parameters. Default is all, consisting of: “velocity”, “acceleration”, “course”, “altitude”, “thrust”, “mass”, “trueanomaly”, “scale”, “timezoom”, “shiptime”
• leftkey: a ggame key identifier that will serve as the “rotate left” key while controlling the ship. Default is ‘left arrow’.
• rightkey: a ggame key identifier that will serve as the “rotate right” key while controlling the ship. Default is ‘right arrow’.

Following parameters may be set as a constant value, or pass in the name of a function that will return the value dynamically or the name of a ggmath UI control that will return the value.

• timezoom scale factor for time zoom. Factor = 10^timezoom
• heading direction to point the rocket in (must be radians)
• mass mass of the rocket (must be kg)
• thrust thrust of the rocket (must be N)

Animation related parameters may be ignored if no sprite animation:

• bitmapframe ((x1,y1),(x2,y2)) tuple defines a region in the bitmap
• bitmapqty number of bitmaps – used for animation effects
• bitmapdir “horizontal” or “vertical” use with animation effects
• bitmapmargin pixels between successive animation frames
• tickrate frequency of spacecraft dynamics calculations (Hz)

getthrust()

User override function for dynamically determining thrust force.

getmass()

User override function for dynamically determining rocket mass.

getheading()

User override function for dynamically determining the heading.

gettimezoom()

User override function for dynamically determining the timezoom.

addStatusReport(statuslist, statusfuncs, statusselect)

Accept list of all status names, all status text functions, and the list of status names that have been selected for display.

velocityText()

Report the velocity in m/s as a text string.

accelerationText()

Report the acceleration in m/s as a text string.

courseDegreesText()

Report the heading in degrees (zero to the right) as a text string.

thrustText()

Report the thrust level in Newtons as a text string.

massText()

Report the spacecraft mass in kilograms as a text string.

trueAnomalyDegreesText()

Report the true anomaly in degrees as a text string.

trueAnomalyRadiansText()

Report the true anomaly in radians as a text string.

altitudeText()

Report the altitude in meters as a text string.

radiusText()

Report the radius (distance to planet center) in meters as a text string.

scaleText()

Report the view scale (pixels/meter) as a text string.

timeZoomText()

Report the time acceleration as a text string.

shipTimeText()

Report the elapsed time as a text string.

dynamics(timer)

Perform one iteration of the simulation using runge-kutta 4th order method.

fr(pos)

Compute the net force vector on the rocket, as a function of the position vector.

ar(pos)

Compute the acceleration vector of the rocket, as a function of the position vector.

vadd(v1, v2)

Vector add utility.

vmul(s, v)

Scalar vector multiplication utility.

vmag(v)

Vector magnitude function.

fgrav()

Vector force due to gravity, at current position.

turn(event)

Respond to left/right turning key events.

Planet

class ggame.astro.Planet(**kwargs)

Initialize the Planet object.

Optional keyword parameters are supported:

• viewscale pixels per meter in graphics display. Default is 10.
• radius radius of the planet in meters. Default is Earth radius.
• planetmass mass of the planet in kg. Default is Earth mass.
• color color of the planet. Default is greenish (0x008040).
• viewalt altitude of initial viewpoint in meters. Default is rocket altitude.
• viewanom true anomaly (angle) of initial viewpoint in radians. Default is the rocket anomaly.
• viewanomd true anomaly (angle) of initial viewpoing in degrees. Default is the rocket anomaly.

run(rocket=None)

Execute the Planet (and Rocket) simulation.

Optional parameters:

• rocket Reference to a Rocket object - sets the initial view