Welcome to Shmorbit

An orbital mechanics sandbox: a 40-meter rocket, the real solar system in 3D, and Kepler. Everything counterintuitive about orbits lives here: to catch up to something, slow down; to go faster at the far side, burn at the near side; to reach Pluto, first tilt your whole orbital plane 17°. Sizes, masses, orbits, and inclinations are the real ones, so a Mars transfer really costs ~3.6 km/s and really takes five months.

Motion is one two-body problem at a time. You're always on a conic (ellipse or hyperbola) around whichever body dominates: inside a moon's sphere of influence — the region where its gravity outweighs its planet's — you orbit the moon; leave a planet's sphere and you orbit the Sun. The path is these conics patched together at the boundaries. Each conic obeys vis-viva, $v^2 = \mu\left(\frac{2}{r} - \frac{1}{a}\right)$, and is solved in closed form: no simulation steps, just Kepler's equation. Maneuvers are instant velocity changes — prograde, radial, or out-of-plane — that fire automatically at their planned time.

Because everything is closed-form, your position is a pure function of the clock and the mission plan. Warp, rewind, and jump don't fast-forward a simulation — they just move the clock. Rewinding to before a maneuver un-executes it, and the future re-forms the moment you edit the plan.

The one thing that must be hunted for rather than solved for is where your path first dips into a body's sphere of influence, so the future is only surveyed a few weeks ahead. A long warp surveys as it goes — and if it turns up an encounter your map didn't show, the warp stops just before it.

• Click your trajectory to place a maneuver or warp to that point; maneuvers snap to Ap/Pe and, with a target set, to the AN/DN plane-crossing nodes.
• Drag the yellow handles for prograde/retrograde, cyan for radial, purple for out-of-plane. Hold shift for fine control.
• Click any body to make it the target or the camera focus; the target panel shows your closest approach and relative inclination.
• ⏮ and ⏭ skip straight between events — maneuvers, encounters, escapes, impacts.
• Scroll to zoom, drag to orbit the camera. Zoom all the way in and the map fades away, leaving just your ship pointed the way it last burned.