I want to make the spaceship orbit in the space, and i have done it through the below script.
But, i want the spaceship to move(change it's position while rotating) ie., for the first 10 rotations it should move around one orbit and for other 10 rotations it should change it's position to other orbit(which is located around the first)...

action orbit
{
var radius = 100; //the radius of the circle it'll move on
var cur_pan;
var speed = 10; //the speed at which the entity will be moving
var cur_center = 0; //the center of the circle.
while(1)
{
my.x = cur_center.x + sin(cur_pan)*radius;
my.y = cur_center.y + cos(cur_pan)*radius;
my.z = cur_center.z;
cur_pan +=speed*time_step;
my.pan -= speed/1 * time_step;
wait(1);
}
}

so you wanna make a solar system or something?

If those orbits are constans You may use paths...
and when ship reach last node add +1 to var f.e. oribts_count.
If orbits_count >=10 go to next path
About paths look HERE

If not... add two another vars
var starting_pan;
var orbit_counts =0;
at the beggining of ship's action set
starting_pan = my.pan (not in loop)
my.pan %= 360;

Then In loop add
if(abs(starting_pan - my.pan) >=360){orbits_count +=1;}
if(orbits_count >=10){radius += 50; orbits_count = 0;}

Not tested but something like this

My problem is not yet solved.

How to increment the radius after every 3 rotations(in the code pasted above).so that after every 3 rotations it will move to other orbit .

give the planet orbit rotation skills, say skill1 and skill2, and the distance from the sun as skill3.I think the script would look like this: Code:

---

my.skill1 += 1 * time;//horizontal orbit rotation += 1 * time
my.skill2 += 1 * time;//vertical orbit rotation += 1 * time (optional)
my.skill3 += 1 * time;//distance from sun increases;

my.x = sun.x + my.skill3 *  cos(my.skill1);//substitute coordinates for sun.x
my.y = sun.y + my.skill3 * sin(my.skill1);
my.z = sun.z + my.skill3 * tan(my.skill2);

---

this isn't tested, but it should make the planet orbit around whatever sun.x is, and increase distance from sun gradually. Hope this works!