Space Simulator
General Category => User's guide, tutorials, documentation => Topic started by: jcarrion on July 12, 2016, 12:40:45 PM

The release of Space Simulator v1.0.6 has been an exciting time for us. Among other major improvements, we finished implementing our nbody solver orbit predictor, which allows beginner and intermediate level players to plan long distance missions with ease.
How is the orbit predictor different to previous versions?
In previous versions, our orbit planner only showed classic analytic orbits, which are perfect circles or ellipses. Of course, these are idealized orbits that work only in an empty Universe with two celestial bodies. They do not take into account the effect of gravity on the orbiting body by other nearby celestial bodies. The idea of a spacecraft orbiting a planet in a perfect ellipse, while conceptually useful, is not always accurate enough for our purposes. In reality orbiting spacecrafts follow complex paths, and this is particularly true in the case of our Earth and Moon, which have a large mass disparity.
In Space Simulator v1.0.6 you are able to compute the actual path of your spacecraft indicated by the pink line. This pink path is calculated numerically. You can adjust the Sim Cycle Length to push how far into the future you wish to calculate the orbital path.
See the below examples
Here we have Shuttle Orion orbiting the Moon. The analytic orbit around the Moon (yellow) shows your typical elliptical orbit. However, using the orbit predictor we compute a path (pink) that tells a very different story. The yellow orbit is actually unstable as our shuttle will eventually be pulled back to the Earth. Our Earth is so massive in comparison to the Moon that only very low orbits around the Moon can be stable. Below are two images showing this unstable orbit. The first is from the point of view of Earth (SIM:Earth) and the second the Moon (SIM:Moon).
(https://s19.postimg.org/bbaye9r77/orbit_predictor_3.png) (https://s19.postimg.org/6e1z6welv/orbit_predictor_4.png)
Another classic example where we can make use of the orbit predictor is the TransLunar Injection. In the below images we see that we can arrive at the Moon by projecting into an orbit that by itself does not actually reach the Moon at the apogee. As we get further from the Earth and closer to the Moon, the Moon exerts some gravitational force that pulls our shuttle just enough to get it into orbit.
(https://s19.postimg.org/8jwa1ei2b/orbit_predictor_1.png) (https://s19.postimg.org/sfs9gxz3n/orbit_predictor_2.png)
With the new orbit predictor there are now two orbit reference buttons. The "ORB" selects the reference of the analytic orbit (yellow) and the "SIM" selects the actual orbit (pink). Below is an example showing a stable lunar orbit with its actual path as seen from Earth.
(https://s19.postimg.org/4q2ts90qb/orbit_planner_5.png)
We hope our new orbit predictor takes the simulation to a new level by giving a clearer view of the complexities and intricacies of space travel. Right from the beginning, our aim has always been to make our game as user friendly as possible for players at all levels. We hope to make our orbit predictor a neat and intuitive way of comprehending and controlling otherwise complex missions and maneuvers.