Author Topic: Use of the orbit planner  (Read 15547 times)


  • Administrator
  • Sr. Member
  • *****
  • Posts: 441
    • View Profile
Use of the orbit planner
« on: June 20, 2015, 10:54:45 AM »
(brief introduction to the orbit visualizer/planner included in version 1.0.3  )

The orbit planner can be accessed at any time  as long as the spacecraft is moving , and it is outside the atmosphere. Simply press "ORBIT" button (top left ) to enter orbit planner mode .

In the default view, we ll see our spacecraft's orbit represented by a green line . Please note that this line can be closed ( circular/eliptical orbits ) or open ( hyperbolic orbits ), in which the exccentricity is > 1.0

By pressing "BACK" button we will return to normal flight simulation mode.

"ORBIT" button opens up the orbital maneuver control panel

On the left , we can increase / decrease 

Delta-V , namely the increase/decrease of speed due to the orbital burn . It increases the altitude at the point opposite the current orbit position .

Delta-T , i.e. how far in the future would be the orbital burn. When planning orbital burns in the future ( Delta-T > 0 ) , the current spacecraft's position is shown in white , while the spacecraft's future position at the time of burn is shown in pink/red ,
Delta-N ,  The burn is tilted perpendicular to the orbit's plane ,

The current orbit will still be shown as green .
The orbit after the burn is shown in Yellow .

The total Delta-V required ( and hence constrained by remaining fuel ) can be seen .

Orbit Reference

As most cellestial objets are orbiting around anothers,  a  spacecraft -say- in orbit around the Moon is also obviously in orbit around the Earth ,and also in orbit around the Sun. You can toggle  the orbital reference by pressing the button with the current reference :

3 views of the same spaecraft with different orbital references:

Moon Orbit Reference

Earth Orbit Reference

Sun Orbital Reference

Transfer orbits

In order to travel to a different celestial body , we need to follow a Transfer orbit . The Hohmann Transfer orbit is an elliptical orbit used to transfer between two circular orbits of different radii in the same plane.
The orbits need to be in the same plane.  It is always a good idea before attempting a Hohmann transfer orbit to  adjust the orbital plane to be the same as the target , and then if possible circularize the orbit , before attempting the transfer.

Example 1:    Mars orbit to Phobos

In this example , we start with mission "Mars Orbit ( Low circular mars orbit )
Here is a video run through of the below steps:

We can see that our orbit lies on a different plane as phobos . 

Let's prepare for transfer by first circularizing our current orbit, ie, reduce eccentricity to 0 as much as possible. Having a circularized orbit will make the subsequent steps easier and more predictable.
Adjust Delta-V accordingly until we get close to 0

In the mobile version of Space Simulator , all natural planets/moons lie on the same elliptic plane (inclination = 0.0 ).  So we need to adjust the orbit of the spacecraft to match the one of Phobos.

To match orbital inclinations ( and hence similar orbital planes) , the maneuver should be performed at the point of crossing those planes. (Ascending and descending nodes ). So here, in this example , we need to advance the Delta_T until the position of the spacecraft is in the same plane as the orbital target .

*tip: an easy way to find the point of intersection with the target plane is to rotate the screen vertically until all the lines of the ecliptic plane align and overlap on the screen in the middle. From here it's easy to identify where your orbit intersects this line.

So we advance Delta T until spacecraft is visually on the ecliptic (or the same target orbital plane ) . 

And then adjust delta N ( Normal burn )  to bring the orbit up (or down) to match the ecliptic until the orbital inclination gets close to zero ( -1 in this example ). Please note the displayed total DeltaV and fuel  requirements for the burn 

By clicking on "GO!" button we perform the orbital burn , and we will be have now an spacecraft orbiting on a almost circular orbit on the same orbital plane than our target Phobos.

Before advancing further on the hohmann maneuvre , we need to understand the use of  "SHOW APO"  (show position at Apogee ).  By pressing this button , the planets/moons,etc. will be show in red , in the position they will be by the time our spacecraft reaches the apogee of the orbit,

"Show APO" Disabled .
Shows (in grey ) the position of Phobos at the current Time
"Show APO" Enabled
Shows (in red ) the position of Phobos by the time the spacecraft will reach Apogee

« Last Edit: November 09, 2020, 06:52:13 PM by jcarrion »