Simulated time0 d

Bodies0

Rate–

FrameInertial

Velocity Launch Osculating orbit

Inspector Hover over a body Drag on empty space to launch a new body. Scroll to zoom; right-drag or Shift-drag to pan.

Click a body to select it · double-click to follow

Orbit Sandbox

A real N-body gravity simulator. Velocity-Verlet integration with adaptive substeps keeps energy and angular momentum honest. Launch bodies, slingshot probes, and watch chaos unfold.

Time scale 1 s = 1 d

Scenarios

Launcher drag on empty space

Mass 1 M⊕ Radius × (collision size) 1×

Display

Trail length 200 Body size (visual) 1×

Selected body

Click a body to see its Kepler elements relative to its dominant attractor.

Conserved quantities drift since last reset or merge

ΔE / |E₀| 0 ΔL / L₀ 0

How it works

Units: AU, solar masses and years, so G = 4π². Planet masses and distances are the real ones.
Integrator: kick-drift-kick velocity Verlet. It is symplectic, so energy error oscillates instead of growing. The step is a few percent of the shortest free-fall or crossing time, re-evaluated every 16 steps.
Collisions merge bodies, conserving momentum and volume. This is inelastic, so the plot re-baselines at each merge.
Rotating frame co-rotates with the two heaviest bodies, which is where Lagrange points sit still. Hill radius is where a body's gravity beats its parent's tidal pull.

2-D Newtonian gravity, point masses, no relativity or non-gravitational forces. Keys: Space pause · F fit · Del delete · Esc deselect.