Download or view orbitalBurn.frink in plain text format
// This program draws the effects of a rocket changing an orbit.
// All of the burns use the same change in speed but burn in
// 4 different directions.
//
/** This file demonstrates how thrust in a rocket changes an orbit.
White: Typical orbit
Red: Stop: Slows down rocket
Green: Go: Speeds up rocket
Blue: Down: Burns downward toward planet
Yellow: Up: Burns upward away from planet
Each velocity change is regarded as instantaneous and occurs at the "top"
of the diagram.
*/
[orbitalHeight, dv] = eval[input["Enter orbital changes",[["Height above ground", "1000 km"], ["Velocity change", "1000 mph"]]]]
y = earthradius + orbitalHeight
x = 0 miles
vy = 0 m/s
// Calculate horizontal velocity for a circular orbit.
// This is derived sybolically by orbit.frink. It's amazing. Check it out.
vx = G^(1/2) earthmass^(1/2) (earthradius + orbitalHeight)^(-1/2)
println["vx = " + (vx -> "mph")]
// Calculate circular orbital period.
// This is derived sybolically by orbit.frink. It's amazing. Check it out.
period = 2 pi vx^-1 (earthradius + orbitalHeight)
println["Period is " + (period -> HMS)]
g = new graphics
g.backgroundColor[0,0,0]
g.color[0,0,.5]
g.fillEllipseCenter[0, 0, 2 earthradius/mile, 2 earthradius/mile]
g.color[1,1,1]
drawOrbit[g, x, y, vx, vy, period] // White: Nominal orbit
g.color[0,0,1] // Blue: down: Accelerate towards earth.
drawOrbit[g, x, y, vx, vy-dv, period]
g.color[1,1,0] // Yellow: up: Accelerate up
drawOrbit[g, x, y, vx, vy+dv, period]
g.color[1,0,0]
drawOrbit[g, x, y, vx-dv, vy, period] // Red: stop: Backwards (slow down)
g.color[0,1,0]
drawOrbit[g, x, y, vx+dv, vy, period] // Green: go: Forwards (speed up)
g.show[]
drawOrbit[g, x, y, vx, vy, period=120 min] :=
{
p = new polyline
timestep = period/1000
for t = 0 min to period step timestep
{
dsqr = x^2 + y^2
a = G earthmass / dsqr
theta = arctan[y,x]
ax = - a cos[theta]
ay = - a sin[theta]
vx = vx + timestep ax
vy = vy + timestep ay
x = x + timestep vx
y = y + timestep vy
p.addPoint[x/mile,-y/mile]
}
g.add[p]
}
Download or view orbitalBurn.frink in plain text format
This is a program written in the programming language Frink.
For more information, view the Frink
Documentation or see More Sample Frink Programs.
Alan Eliasen was born 20139 days, 6 hours, 35 minutes ago.