OrbitalMechanics

Orbits do not behave like driving. This course builds the mental model first — free fall, energy, the shape of a conic — and only then introduces the equations, so the maths confirms something you already believe.

The chapter and lesson structure below is real and final. Lesson content is still being written, so nothing here opens yet — and there is no sign-in, no progress and no completion tracking, because none of that is built.

• How Flight Works, or equivalent physics
• Basic trigonometry

1. 01

   Falling around

   Why orbit is sideways, and what weightlessness really is.

   1. VisualiseNewton's cannonballIncrease the muzzle velocity until the ball misses the ground entirely.9m
   2. ReadWeightlessness is free fallWhy the station is not "outside gravity", and what astronauts are actually doing.7m
2. 02

   The shape of an orbit

   Circles, ellipses, apoapsis and periapsis, and orbital energy.

   1. ReadConic sectionsOne family of curves covers every unpowered trajectory there is.10m
   2. VisualiseEnergy and velocityAdd and remove energy at different points and watch the orbit change.12m
   3. ApplyGetting from one orbit to anotherPlan a Hohmann transfer and check your delta-v against the answer.14m