Add a short technical report

Author: arda-guler

README.md

@@ -7,9 +7,7 @@ Sophisticated astrodynamics and space mission simulator.
 Simulate n-body trajectories, calculate Keplerian orbits, perform orbital maneuvers, apply perturbations, manage custom resources such as power generation, display or plot variables with as much customization as you want.
 Create scenario or batch files to share your simulations, export data or get rid of repetitive tasks.
 
-Do all of this in Python, the beloved programming language of science and engineering.
-
-To learn more, see [the manual](https://github.com/arda-guler/orbitSim3D/blob/master/docs/MANUAL.md).
+To learn more, see [the manual](https://github.com/arda-guler/orbitSim3D/blob/master/docs/MANUAL.md) or the [short technical report](https://github.com/arda-guler/orbitSim3D/blob/master/docs/OrbitSim3D.pdf).
 
 Having trouble finding your way around? Have a look at the [introductory tutorial](https://github.com/arda-guler/orbitSim3D/blob/master/docs/tutorial.md) for the basics!