Orbital mechanics

Understand orbits and spacecraft maneuvers through diagrams, simulations, and mathematics.

Prerequisite: High-school physics. No calculus required. Follow trajectories and calculate idealized maneuvers. Each lesson includes visual models, exercises, hints, and worked answers.

Lessons

1. 1

   Why objects orbit

   Connect gravity, velocity, and continuous free fall. Distinguish speed from direction and altitude from radius.

2. 2

   Describing an orbit

   Read circular and elliptical trajectories. Explore equal areas, eccentricity, and orbital periods.

3. 3

   Energy and angular momentum

   Explain changing orbital speed with energy and angular momentum. Calculate speeds at both ends of an ellipse.

4. 4

   Changing an orbit

   Separate an immediate burn from the later coast. Calculate both burns of a Hohmann transfer.

5. 5

   Meeting another spacecraft

   Match position, timing, and velocity. Compare phasing orbits and the cost of plane changes.

6. 6

   Leaving a planet

   Calculate escape speed and plan an idealized Earth-to-Mars transfer with a departure phase angle.