### Author Topic: Satellite motion  (Read 18721 times)

#### Fu-Kwun Hwang

• Hero Member
• Posts: 3062
##### Satellite motion
« on: August 28, 2007, 04:34:20 pm »
You will find two simulations for satellite motion due to the gravitation force between satellite and massive object(center one with cyan color).
Which one is the correct simulation? The one will rotate or another one which does not rotate?

You can pause the simulation. Change the location or velocity of the satellite when velocity vector is visiable, then press 'play' button again. Enjoy it!
-*-

Full screen applet or Problem viewing java?Add http://www.phy.ntnu.edu.tw/ to exception site list
• Please feel free to post your ideas about how to use the simulation for better teaching and learning.
• Post questions to be asked to help students to think, to explore.
• Upload worksheets as attached files to share with more users.
Let's work together. We can help more users understand physics conceptually and enjoy the fun of learning physics!

#### lookang

• Hero Member
• Posts: 1772
• http://weelookang.blogspot.com
##### Re: Satellite motion
« Reply #1 on: September 05, 2007, 01:23:15 am »
Hi prof hwang,

Q1: can you demonstrate how to wrap a world map onto the circle(sphere) in 3D view ?
http://science.nasa.gov/Realtime/JTrack/3d/JTrack3D.html

there is a non rotating Earth

many people can't visualize the meaning of geostationary orbit, i hope to help make an applet.

Q2: why is the xml file you declare GM = R*R instead of using the G = 6.67*10^-11 and M = 6.0x10^24 ?

the rest still thinking, those i know i post here for others to learn

Model constraint page:
cta=-Math.atan2(x,y); // cta is angle of satellite from origin which is earth comment lines by weelk
r=Math.sqrt(x*x+y*y); // r is radius of rotation comment lines by weelk
if(r>xmax*scale)scale=r*1.2/xmax; // just a way the scale the simulation 1.2 times bigger if the radius in getting bigger than xmax*scale instead of autoscale all the time comment lines by weelk

Model custom page:
double r,r2,r3,cst;
public double getA (double x, double y) {
r2=x*x+y*y;
r3=r2*Math.sqrt(r2);
return -GM*x/r3; //clever way of function getA (x,y) acceleration along each axis comment lines by weelk
}

I was hoping i can modify your codes to make a realistic earth with satellite in 3D view.

i will later add potential versus distance, mass of satellite changeable.

and others can use your template to make applets to suit their needs.

thanks
« Last Edit: September 05, 2007, 01:36:36 am by lookang »

#### Fu-Kwun Hwang

• Hero Member
• Posts: 3062
##### Re: Satellite motion
« Reply #2 on: September 06, 2007, 11:08:36 pm »
The applet created by NASA was running with real time data. That is a good resource.
I believe their world map was draw with available data. It is not a combination of a static graphs in a 3D environment.
If you can find data for the earth surface. You can draw it with polygon element easily.

#### lookang

• Hero Member
• Posts: 1772
• http://weelookang.blogspot.com
##### Re: Satellite motion
« Reply #3 on: September 06, 2007, 11:23:50 pm »
i like easy!!!

data refers to graphics ?