njme.net · orb-mechanics

Orbital mechanics

An eleven-module web introduction to orbital mechanics for readers with one college physics class plus basic calculus and trigonometry. Real equations, real understanding — you should leave knowing what SatView is showing.

Modules

  1. Gravity and free fall Newton's cannonball with real Newtonian gravity. An orbit is just falling sideways fast enough to keep missing. Ready
  2. Circular orbits Derive orbital velocity and period from F=ma. Connect to real satellites. Ready
  3. Energy and vis-viva Conservation of mechanical energy. The vis-viva equation as the workhorse of orbit problems. Ready
  4. Kepler's three laws Equal areas in equal times — the visual showpiece of celestial mechanics. Ready
  5. Anatomy of an ellipse Semi-major axis, eccentricity, periapsis, apoapsis. Geometry of the conic sections. Ready
  6. Orbital elements Six numbers that pin down a 3D orbit. Decode a real TLE. Ready
  7. Hohmann transfers First useful calculation: how much delta-v to move between circular orbits. Ready
  8. Interplanetary basics Patched conics, launch windows, gravity assists. Ready
  9. The rocket equation Tsiolkovsky, specific impulse, the exponential mass-ratio penalty. Why a launching rocket is mostly fuel. Ready
  10. Burns, timing, and launch windows Impulsive vs finite burns, Oberth effect, why the two Hohmann burns are non-negotiable, Earth-rotation boost, Mars's 26-month launch cadence. Ready
  11. Three-body and Lagrange points Rotating-frame simulator showing L1–L5. Ready
Appendix — Kepler's equation. A short page on M = E − e·sin E and Newton–Raphson iteration, cross-linked from modules 4 and 5 for the curious.
Glossary. Definitions for the technical terms used throughout the curriculum. Marked terms inside any module also surface as tooltips on hover or tap.