Space Simulator  1.0.9
space flight simulator
Trans Lunar Injection

Trans Lunar Injection is an orbital maneuver to get your spacecraft from an Earth parking orbit to the Moon. By burning the rocket engines at the appropriate time, we are able to increase Delta-V enough to change a circular orbit to a highly ecentric orbit capturing the Moon on the other side.

In this walkthrough we'll use the custom Earth Shuttle Orion mission scenario. Open Missions/Custom Scenario. Select Earth as the reference and Launch, leaving all other default settings.


We begin our mission with the Shuttle Orion orbiting the Earth in an orbit with eccentricity of 0.35 and inclination of 39 degrees.

A basic TransLunar Injection consists of 4 steps:

STEP 1: make orbit COPLANAR

First thing to do is align our orbit with the ecliptic plane. Move the shuttle forward in time, using either the Delta-T buttons or Time+, until it intersects the ecliptic plane and adjust the normal until the inclination is as close to 0 as possible. For detailed instructions of this step please see the page .CoplanarOrbits.

STEP 2: make orbit CIRCULAR

The next step is to circularize our oribt. Move the shuttle to the apogee using either the Delta-T or Time+. Once at the apogee, increase Delta-V until the orbit is circularized. An orbit is circualrized when the eccentricity is 0. For detailed instructions of this step please see the page .CircularizeOrbits.

STEP 3: Hohmann Transfer to the Moon

Once our orbit is coplanar and circular we are ready to transfer to the Moon. Increasing Delta-V until the orbit just reaches the Moon on the other side.


Now we need to find the right combo of Delta-T and Delta-V that takes us to the Moon. For this we need to use the button "APO":


APO shows where the Moon would be when you are at the apogee on the other side of the orbit.

In the above image, using APO we see that by the time we are on far side of the orbit at Point A, the Moon will be at Point B. In this case, the Moon will have already moved forward by the time we get to the other side of our orbit so we will have missed it.

Now adjust Delta-V and Delta-T until the apogee captures the Moon.


Once you're happy with the positions, hit "Select" to save changes. You are now set for the Moon. Use Time+ to speed up this part of the journey. Slow down as you approach the Moon, making sure to not overshoot.


STEP 4: Moon orbit insertion

Finally, once you are within range of the Moon orbit, change your orbit reference to Moon.


You will see that you are in a hyperbolic orbit with respect to the Moon. Decrease Delta-V until you have a circular orbit.


You have now successfully completed your mission.